Drosera anglica Huds. (English sundew): A Technical Conservation Assessment

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Drosera rotundifolia L. (roundleaf sundew):
A Technical Conservation Assessment
Prepared for the USDA Forest Service,
Rocky Mountain Region,
Species Conservation Project
June 29, 2006
Evan Wolf, Edward Gage, and David J. Cooper, Ph.D.
Department of Forest, Rangeland, and Watershed Stewardship
Colorado State University
Fort Collins, CO 80523

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Wolf, E., E. Gage, and D.J. Cooper. (2006, June 29). Drosera rotundifolia L. (roundleaf sundew): a technical
conservation assessment. [Online]. USDA Forest Service, Rocky Mountain Region. Available: http://
www.fs.fed.us/r2/projects/scp/assessments/droserarotundifolia.pdf [date of access].
ACKNOWLEDGMENTS
Numerous people helped us in preparation of this assessment by contributing ideas, data, photographs, or
other forms of assistance. The Colorado Natural Heritage Program provided element occurrence data and habitat
information essential to the document. We also wish to thank the many USDA Forest Service personnel who provided
help or guidance, including Steve Popovich, John Proctor, and Gary Patton. The Rocky Mountain Herbarium,
Colorado State University Herbarium, and the University of Colorado Herbarium provided important information,
as did several individuals including Nan Lederer, Betsy Neely, John Sanderson, Christopher Cohu, and Bill Jennings.
Thanks also to Rachel Ridenour and Emily Drummond for their assistance. We would like to thank David Anderson
for making available earlier drafts of his Species Conservation Project assessments, which were helpful in organizing
our work. Thanks also to Dan Rice of the University of California, Davis for permission to use photographs. We also
wish to thank Kathy Carsey, Beth Burkhart, Kathy Roche, Katherine Darrow, and an anonymous reviewer for their
insightful comments.
AUTHORS’ BIOGRAPHIES
Evan Wolf, M.S., is a research associate at Colorado State University, living and working in California where he
is involved in a number of mountain wetland research and restoration projects. He spent nine years in Colorado, four
earning a B.A. in Geology at Colorado College, two as a GIS specialist with the Inland West Water Initiative at the
USDA Forest Service Region 2 Headquarters, and three earning an M.S. in Ecology from Colorado State University.
Edward Gage, M.S., is a research associate at Colorado State University. He earned a B.S. in Natural Resource
Ecology from the University of Michigan and an M.S. from Colorado State University. His research and project
experiences include wetland and riparian inventory and mapping work, hydrologic, ecological, and functional wetland
assessments, studies of native ungulate and riparian vegetation interactions, and studies of anthropogenic impacts to
riparian and peatland ecosystems.
David J. Cooper, Ph.D. is a senior research scientist in the Department of Forest, Rangeland and Watershed
Stewardship, and an advising faculty member in the Graduate Degree Program in Ecology at Colorado State University,
where he has worked for 12 years. He received his bachelors and Ph.D. degrees at the University of Colorado, Boulder,
working on arctic and alpine tundra ecology. For the past 20 years his research and teaching involves wetland and
riparian ecosystems in western North America, and he has expertise in oristics, classication, ecosystem restoration,
hydrology, geochemistry and geomorphology.
COVER PHOTO CREDIT
Drosera rotundifolia L. (roundleaf sundew). Photograph by David J. Cooper.

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SUMMARY OF KEY COMPONENTS FOR CONSERVATION OF
DROSERA ROTUNDIFOLIA
Status
Drosera rotundifolia (roundleaf sundew) has a circumboreal distribution and is widespread and abundant
in many regions. Globally it is not threatened with extinction in the foreseeable future and is ranked as G5,
apparently secure (NatureServe 2004). However, the occurrences located within USDA Forest Service Region 2 are
geographically isolated and may represent genetically distinct occurrences. The species is ranked S2, imperiled, in the
state of Colorado (Colorado Natural Heritage Program 2004b).
The four veried Region 2 occurrences of Drosera rotundifolia are located in fens in Colorado. Three
occurrences are in sites with oating mats, and one is in a rare iron fen. Fens are uncommon in the Rocky Mountains
and are critical to the survival of these D. rotundifolia occurrences. Drosera rotundifolia is exceptionally well-adapted
to the waterlogged and nutrient poor environment of fens; it derives a signicant proportion of its nutrients through
carnivory and cannot compete and survive in any other habitat.
Primary Threats
The most immediate threats to Drosera rotundifolia are events that alter the hydrologic function of fens. Water-
saturated conditions produced by perennial groundwater discharge are critical for maintaining slow rates of organic
matter decomposition and nutrient turnover in fens. Activities that disrupt, divert, augment, or redistribute groundwater
or surface ow to and through a fen have the potential to alter its ecosystem function and oristic composition. Site-
wide impacts may occur directly in the fen from activities such as ditching or groundwater pumping. Other impacts
can occur from activities in adjacent ecosystems, including logging, res, road building, diverting surface ow, and
pumping groundwater.
Within a fen, a variety of microsites occur that inuence the distribution of plant communities. Activity within a
fen can signicantly impact the quality and abundance of these microsites. For example, trampling by cattle, people,
vehicles and native animals can break apart oating peat mats that provide Drosera rotundifolia habitat.
Any change in the nutrient budget of a fen can also signicantly alter site suitability for Drosera rotundifolia.
Being adapted to nutrient-poor environments, D. rotundifolia would likely suffer from fertilization via atmospheric
deposition of nitrogen, addition of livestock excrement, or an increase in the nutrient concentration of the water
supporting the fen.
Primary Conservation Elements, Management Implications and Considerations
The principle consideration when making conservation decisions for Drosera rotundifolia is to ensure that the
groundwater and surface water ow regimes remain unaltered. This necessitates a full understanding of the hydrologic
processes in sites supporting D. rotundifolia occurrences. Intra- and inter-annual groundwater and surface water data
are essential to identify water sources, ow paths, and the range of variability in ow rate and water levels in fens.
The integrity of the peat body in which Drosera rotundifolia roots is the second most important management
concern. Direct physical impact from hooves, feet, and tires is the most common source of damage to the interwoven
mass of roots, rhizomes, and undecayed organic matter. In the southern Rocky Mountain region, peat takes an
extremely long time to accumulate, but if broken apart and exposed to air, it will decompose rapidly. The peat body’s
structure provides much of the microsite variation critical to fen plants, including D. rotundifolia.
Another detrimental impact to peat-accumulating ecosystems is the input of mineral sediment. Peat is composed
primarily of undecayed plant material, and its physical properties, such as capillarity, bulk density, and water holding

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capacity, are altered when inorganic sediment is added. Any action that leads to the input of signicant amounts of
mineral sediment to a fen will alter the microsite hydrologic and geochemical regimes in the peat body, potentially
reducing habitat suitability for Drosera rotundifolia.

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TABLE OF CONTENTS
ACKNOWLEDGMENTS ..............................................................................................................................................2
AUTHORS’ BIOGRAPHIES.........................................................................................................................................2
COVER PHOTO CREDIT .............................................................................................................................................2
SUMMARY OF KEY COMPONENTS FOR CONSERVATION OF DROSERA ROTUNDIFOLIA ..........................3
Status..........................................................................................................................................................................3
Primary Threats..........................................................................................................................................................3
Primary Conservation Elements, Management Implications and Considerations.....................................................3
LIST OF TABLES ..........................................................................................................................................................7
LIST OF FIGURES ........................................................................................................................................................8
INTRODUCTION ..........................................................................................................................................................9
Goal............................................................................................................................................................................9
Scope and Information Sources .................................................................................................................................9
Treatment of Uncertainty ...........................................................................................................................................9
Publication of Assessment on the World Wide Web ................................................................................................10
Peer Review .............................................................................................................................................................10
MANAGEMENT STATUS AND NATURAL HISTORY ...........................................................................................10
Management and conservation status..................................................................................................................10
Global rank ..................................................................................................................................................... 10
Federal status ..................................................................................................................................................10
USDA Forest Service regional designation....................................................................................................10
State rank ........................................................................................................................................................10
Existing Regulatory Mechanisms, Management Plans, and Conservation Practices ..............................................10
Biology and Ecology................................................................................................................................................ 11
Classication and description..............................................................................................................................11
Systematics and synonymy.............................................................................................................................11
History of species ...........................................................................................................................................11
Morphological characteristics ........................................................................................................................12
Distribution and abundance.................................................................................................................................13
Population trends................................................................................................................................................. 15
Reproductive biology and autecology................................................................................................................. 15
Reproduction ..................................................................................................................................................15
Life history and strategy.................................................................................................................................18
Pollinators and pollination ecology ................................................................................................................19
Dispersal mechanisms ....................................................................................................................................19
Seed viability and germination requirements .................................................................................................19
Cryptic phases ................................................................................................................................................19
Mycorrhizal relationships...............................................................................................................................19
Hybridization..................................................................................................................................................19
Demography ........................................................................................................................................................20
Life history characteristics .............................................................................................................................21
Ecological inuences on survival and reproduction.......................................................................................21
Genetic characteristics and concerns.............................................................................................................. 22
Factors limiting survival and reproduction.....................................................................................................23
Community and ecosystem ecology....................................................................................................................23
General habitat characteristics........................................................................................................................23
Substrate characteristics and microhabitats.................................................................................................... 26
Region 2 habitat characteristics...................................................................................................................... 26
Water and peat chemistry ...............................................................................................................................27
Wetland hydrology .........................................................................................................................................29
Vegetation associations and associated plant species ..................................................................................... 31
Competitors and relationship to habitat..........................................................................................................31
Herbivores and relationship to habitat............................................................................................................33

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Parasites and disease.......................................................................................................................................33
Symbiotic and mutualistic interactions ..........................................................................................................33
CONSERVATION.........................................................................................................................................................33
Threats......................................................................................................................................................................33
Timber harvest.....................................................................................................................................................33
Fire ......................................................................................................................................................................34
Roads and trails ...................................................................................................................................................34
Peat extraction .....................................................................................................................................................35
Mineral development...........................................................................................................................................36
Livestock and native ungulate grazing................................................................................................................ 36
Recreational impacts ...........................................................................................................................................36
Over-collection.................................................................................................................................................... 38
Exotic species......................................................................................................................................................38
Atmospheric deposition of pollutants .................................................................................................................38
Climate change....................................................................................................................................................39
Assessment of threats to Region 2 Drosera rotundifolia populations.................................................................39
Conservation Status of Drosera rotundifolia in Region 2 .......................................................................................39
Management of Drosera rotundifolia in Region 2...................................................................................................41
Implications and potential conservation elements ..............................................................................................41
Tools and practices.............................................................................................................................................. 41
Availability of reliable restoration methods ...................................................................................................42
Information Needs and Research Priorities .............................................................................................................42
DEFINITIONS..............................................................................................................................................................44
REFERENCES .............................................................................................................................................................47
EDITORS: Kathy Carsey, Kathy Roche, and Beth Burkhart, USDA Forest Service, Rocky Mountain Region

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LIST OF TABLES
Table 1. List of USDA Forest Service Region 2 herbaria and Colorado Natural Heritage Program element
occurrence records for Drosera rotundifolia. ...............................................................................................................17
Table 2. Genetic variability at 13 loci of Drosera rotundifolia from Colorado and California occurrences................23
Table 3. Comparison of water pH, calcium (Ca2+) and magnesium (Mg2+) ion concentrations measured in
wetlands with Drosera rotundifolia.............................................................................................................................. 29
Table 4. Common vegetation associates reported from wetlands supporting Drosera rotundifolia.............................32
Table 5. Estimates of the relative importance of various threats to USDA Forest Service Region 2 Drosera
rotundifolia occurrences. ..............................................................................................................................................39

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LIST OF FIGURES
Figure 1. Key Drosera rotundifolia structures..............................................................................................................12
Figure 2. Rosette and leaves of Drosera rotundifolia...................................................................................................13
Figure 3. Distribution of Drosera rotundifolia in the northern hemisphere. ................................................................14
Figure 4. Distribution of main peat-forming areas in the continental United States. ...................................................14
Figure 5. Distribution of Drosera rotundifolia within USDA Forest Service Region 2...............................................16
Figure 6. Arthropod diversity of Drosera rotundifolia prey. ........................................................................................18
Figure 7. Seed germination of Dorsera rotundifolia in relation to burial depth...........................................................20
Figure 8. Hibernacula of Drosera rotundifolia. ............................................................................................................20
Figure 9. Life cycle diagram for Drosera rotundifolia. ................................................................................................21
Figure 10. Population growth rate for each of four one-year periods and quartiles for depth to water table and peat
production ability..........................................................................................................................................................22
Figure 11. Boxplot comparison of environmental variables in Sierra Nevada fens where Drosera rotundifolia was
present and absent.........................................................................................................................................................24
Figure 12. Illustration of hillslope fens associated with a bedrock contact or a bedrock fracture................................25
Figure 13. Illustration of upwelling groundwater at the toe of a hillslope supporting a spring mound fen. ................25
Figure 14. Illustration of a closed basin where groundwater feeds a lake that supports a oating mat fen. ................25
Figure 15. Illustration of sloping fen that formed where groundwater ow is concentrated........................................26
Figure 16. Photograph of the Gunnison County fen, Gunnison National Forest..........................................................27
Figure 17. Example of the type of oating mat habitat that supports Drosera rotundifolia at the Grand County fen. 27
Figure 18. Floating mat at Jackson County site 1.........................................................................................................27
Figure 19. pH values from groundwater monitoring wells established across the fen in Gunnison County................28
Figure 20. Box plots of water chemistry parameters comparing Sierra Nevada fens with Drosera rotundifolia and
without D. rotundifolia. ................................................................................................................................................30
Figure 21. Response surface for Drosera rotundifolia along water table and pH gradients in an Italian poor fen......30
Figure 22. Monitoring well and piezometer data from well 5 in Gunnison County fen, demonstrating the stable
water table and inuence of groundwater on fen hydrology.........................................................................................31
Figure 23. Schematic cross-section of the Gunnison County fen supporting Drosera rotundifolia.............................36
Figure 24. Effects of trampling from recreational users on the oating mat of the fen in Grand County. ...................37

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INTRODUCTION
This assessment is one of many being produced
to support the Species Conservation Project for the
Rocky Mountain Region (Region 2), USDA Forest
Service (USFS). Drosera rotundifolia L. (roundleaf
sundew) is the focus of an assessment because within
Region 2 it is a disjunct species with an extremely
limited distribution, and therefore the viability of the
population is a concern. Within the USFS, a species
whose population viability is identied as a concern
by a Regional Forester because of signicant current
or predicted downward trends in abundance and/or in
habitat capability that would reduce its distribution
may be designated as a sensitive species (USDA
Forest Service 2005). The USFS lists D. rotundifolia
as a sensitive species in Region 2 (USDA Forest
Service 2002). A sensitive species may require special
management, so knowledge of its biology and ecology is
critical. This assessment addresses the biology, ecology,
conservation status, and management of D. rotundifolia
throughout its range in Region 2. The introduction
denes the goal of the assessment, outlines its scope,
and describes the process used in its production.
Goal
Our goal in this document is to provide a
comprehensive and synthetic review of the biology,
ecology, and conservation status of Drosera rotundifolia
within USFS Region 2. The assessment goals limit the
scope of this work to critical summaries of scientic
knowledge, discussion of broad implications of that
knowledge, and outlines of information needs. Since D.
rotundifolia occurs only in specic types of wetlands,
we focus on factors controlling the hydrologic regime
and geochemistry of these wetlands since these variables
represent key ecological drivers of the structure and
function of wetlands. In this assessment, we do not seek
to develop specic management recommendations.
Rather we provide the ecological background upon
which management must be based and focus on the
consequences of changes in the environment that result
from management (i.e., management implications).
Scope and Information Sources
With this assessment, we provide a synthesis of
current knowledge on a wide variety of topics relevant
to the basic biology, ecology, and conservation status
of Drosera rotundifolia. Considering the broad scope
of the assessment, we have drawn upon a range of
information sources, including peer-reviewed scientic
literature, non-peer-reviewed literature (e.g., theses,
dissertations, agency reports), herbarium records, and
GIS data sources such as element occurrence records
from state natural heritage programs in the region.
Where appropriate we have incorporated unpublished
data, reports, and conversations with known experts.
The emphasis of this assessment is on Drosera
rotundifolia within Region 2. However, the species has
a wide geographic distribution throughout the northern
hemisphere, and considerable information is available
from outside the region. Though topics discussed
in this assessment are largely set in the context of
current environmental conditions, when possible we
have incorporated information regarding evolutionary
and biogeographic aspects of both the species and
the wetland types in which it occurs. These broader
perspectives are essential for developing realistic
assessments of current and future conservation threats.
Treatment of Uncertainty
Ecological systems and the biota inhabiting them
are, by nature, exceedingly complex. Multiple variables
inuence any given ecological attribute. Key variables
frequently lack independence and are difcult to isolate
and effectively measure, further complicating data
collection and analysis. Moreover, ecological patterns
and processes are often strongly scale dependent,
with generalizations appropriate at one scale being
inappropriate at another scale. When preparing a broad-
scale assessment as this one, it is important to explicitly
address issues of uncertainty.
Though widely distributed globally, Drosera
rotundifolia occurs at only a very few sites within
Region 2. Unfortunately, there are few quantitative
data on many aspects of D. rotundifolia available
from known Region 2 occurrences, making denitive
statements about the ecology or conservation status of
the species in the region difcult. However, because of
its wide distribution and its interest as one of a limited
number of carnivorous plant species, D. rotundifolia
has been extensively studied elsewhere. We have drawn
upon these studies to make inferences about the species
in Region 2, but because it is easy to misapply research
ndings outside of their original ecological context, we
have been judicious in the use of these data.
Considering the lack of rigorous, experimental
research conducted on Drosera rotundifolia within
Region 2, we have relied heavily upon our knowledge
of the particular wetland types where the species occurs.
In concert with insights provided by other scientists and
managers and careful extrapolation of work conducted

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outside the region, we provide a rst approximation of
the species’ biology, ecology, and conservation status.
To help readers evaluate our conclusions, we explicitly
note the strength of evidence for particular ideas
throughout the assessment and, where possible, provide
alternative hypotheses.
Publication of Assessment on the World
Wide Web
To facilitate their use in the Species
Conservation Project, species assessments will be
published on the USFS Region 2 World Wide Web
site (http://www.fs.fed.us/r2/projects/scp/assessments/
index.shtml). Placing documents on the Web makes
them available to agency biologists and the public
more rapidly than publishing them as reports. More
importantly, it facilitates revision of the assessments,
which will be accomplished based on guidelines
established by USFS Region 2 (USDA Forest
Service 2004).
Peer Review
Assessments developed for the Species
Conservation Project have been peer reviewed prior
to their release on the Web. This report was reviewed
through a process administered by the Center for Plant
Conservation, employing two recognized experts
on this or related taxa. Peer review was designed to
improve the quality of communication and to increase
the rigor of the assessment.
MANAGEMENT STATUS AND
NATURAL HISTORY
Management and conservation status
Global rank
The Global Heritage Status Rank for Drosera
rotundifolia is G5, globally secure, as a result of its
scattered distribution over a very broad range, and the
variety that occurs in Region 2, D. rotundifolia var.
rotundifolia, is ranked T5, a globally secure infraspecic
taxon (NatureServe 2004).
Federal status
The National Heritage Status Rank for Drosera
rotundifolia is N5, secure, within the United States
and Canada (NatureServe 2004). The species is neither
listed nor a candidate for listing under the Endangered
Species Act.
USDA Forest Service regional designation
USDA Forest Service Region 2, which
encompasses Colorado, and parts of Kansas, Nebraska,
South Dakota, and Wyoming, lists Drosera rotundifolia
as a sensitive species due to its disjunct distribution and
restriction to rare habitats that are unusually sensitive to
disturbance (USDA Forest Service 2002).
State rank
The Colorado Natural Heritage Program ranks
Drosera rotundifolia as S2, imperiled within the state,
because of rarity (6 to 20 occurrences, or 1,000 to 3,000
individuals) and/or other factors that demonstrably make
the species very vulnerable to extinction throughout
its range within the state (Colorado Natural Heritage
Program 2004b). The other states within Region 2 do
not rank D. rotundifolia.
Outside of Region 2 Drosera rotundifolia is
listed as critically imperiled (S1) in Iowa, Tennessee,
Alabama, and Georgia; imperiled (S2) in Illinois
and Delaware; and vulnerable (S3) in Indiana, West
Virginia, North Carolina, and Maryland. These rankings
are due to the species’ restricted range, relatively few
(often less than 80) occurrences in the state, recent
and widespread declines, or other factors making
it vulnerable to extirpation. Drosera rotundifolia is
apparently secure (S4) in Rhode Island, Newfoundland,
and Labrador (Canada), where it is uncommon but
not rare, with some cause for long-term concern due
to declines or other factors. Six Canadian provinces
– Alberta, Manitoba, Ontario, Quebec, Prince Edward
Island, and Nova Scotia – list D. rotundifolia as secure
(S5) because it is common, widespread, and abundant
(NatureServe 2004).
The variety Drosera rotundifolia var.
rotundifolia, the taxon found in Region 2, is listed
as vulnerable (S3) in North Carolina and secure (S5)
in New Jersey, British Columbia, Saskatchewan, and
Prince Edward Island. The variety D. rotundifolia
var. comosa is listed as critically imperiled (S1) in
New Brunswick. Explanations of the Natural Heritage
Program ranking system are found in the Denitions
section of this document.
Existing Regulatory Mechanisms,
Management Plans, and Conservation
Practices
The USFS Region 2 has designated Drosera
rotundifolia as a sensitive species. As such, it is

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protected under the Code of Federal Regulations, and
damaging or removing any plants is prohibited (Code
of Federal Regulations 2005). In addition the USFS is
bound by certain directives regarding the management
of sensitive species (US Forest Service 2005).
Drosera rotundifolia is an obligate wetland
species (i.e., restricted to wetland habitat) (Reed 1988).
The wetlands that support occurrences of this species
receive some protection under existing federal, state,
and local statutes. For instance, Section 404 of the
Clean Water Act has historically placed regulatory
oversight on a range of activities impacting wetlands
with the U.S. Army Corps of Engineers (USACE).
Executive order 11990, signed by Jimmy Carter,
instructs federal agencies to “minimize the destruction,
loss or degradation of wetlands”. However, a recent
Supreme Court decision (SWANCC vs. USACE)
has effectively removed federal regulatory oversight
for wetlands that lack connections to surface water
bodies, such as streams. Most fens are not connected to
navigable waters via surface ow and therefore may be
considered isolated under USACE jurisdiction through
the Clean Water Act (Bedford and Godwin 2003).
The Forest Service Manual series 2520 (USDA
Forest Service 2004) and the USDA Forest Service
Technical Guide to Managing Ground Water (USDA
Forest Service 2005) provide agency-wide guidance
on the denition, protection, and management of
wetlands. Wetland management directives specic to
Region 2 are covered by the Forest Service Handbook
series 2509.25 (USDA Forest Service 2006). Regional
guidance on fens is provided by USFS memo 2070/
2520-72620, signed by the Director of Renewable
Resources, which emphasizes the protection,
preservation, and enhancement of fens to all Region
2 forest supervisors (Proctor personal communication
2004). The U.S. Fish and Wildlife Service addresses
the protection of the wetland types specic to Drosera
rotundifolia habitat as well (U.S. Fish and Wildlife
Service 1997, Gessner 1998).
If properly executed and enforced, these directives
and regulations should help to identify, preserve, and
protect Drosera rotundifolia occurrences and habitat.
Biology and Ecology
Classication and description
Systematics and synonymy
Drosera rotundifolia L. is a member of the family
Droseraceae, which contains two other carnivorous snap-
trap genera, Dionaea (Venus ytrap) and Aldrovanda
(waterwheel plant). Droseraceae is classied in the
order Caryophyllales, in a clade with three other families
containing carnivorous genera, the Nepenthaceae,
Drosophyllaceae, Dioncophyllaceae, and one non-
carnivorous family, the Ancistrocladaceae. Carnivory
evolved in several other plant groups, but snaptrap-
type carnivory is only found in the Caryophyllales
(Stevens 2001). This indicates convergent evolution of
the general trait of carnivory but a common origin of
the specic snap-trapping mechanism (Cameron et al.
2002). The order Caryophyllales belongs to the class
Magnoliopida (dicotyledons), division Magnoliophyta
(owering plants), super-division Spermatophyta
(seed plants), sub-kingdom Tracheobionta (vascular
plants), in the kingdom Plantae (plants) (USDA Natural
Resources Conservation Service 2002).
Three North American varieties of Drosera
rotundifolia are recognized: var. rotundifolia, var.
camosa Fernald, and var. gracilis Laestad (USDA
Natural Resources Conservation Service 2002). Drosera
rotundifolia var. rotundifolia is found in Alaska, across
most of Canada, in the Pacic Northwest and Great
Lakes regions of the United States, along the Atlantic
and Gulf coasts, and in Colorado. Within the United
States, D. rotundifolia var. camosa is only found in the
northeast, and D. rotundifolia var. gracilis is found only
in Alaska.
History of species
Carl Linnaeus originally described Drosera
rotundifolia in 1753. The lectotype specimen is housed
in the herbarium of the Linnean Society of London.
Extensive work has since followed on the genetics,
biology, ecology and especially the carnivory of the
genus Drosera. Charles Darwin discussed Drosera

12 13
in his 1875 publication “Insectivorous Plants”, and
his brother Francis conducted experiments on the
nutrition of Drosera (Darwin 1878). The majority
of the current research on D. rotundifolia, from the
genetic level up through ecosystem processes such
as climate change and aerial nitrogen deposition, has
occurred in Europe. While relatively little research
has been conducted on this species in the western
United States, recent work includes a dissertation
on its pollination ecology in California (Engelhardt
1998), a botanical survey of a Colorado occurrence
(Rocchio and Stevens 2004), a genetic study of
Colorado and California occurrences (Cohu 2003),
and a hydrologic analysis of a fen supporting another
Colorado occurrence (Cooper 2003).
Morphological characteristics
Drosera rotundifolia is an herbaceous perennial
plant with a slender vertical axis about 3 cm long in
plants grown in full sun, and up to 5 cm long in shade-
grown plants (Figure 1). The leaves attach spirally in
a basal, prostrate rosette of long, at, narrow, petioled,
pubescent leaves up to 8 cm across (Figure 2). The
leaves are divided into two parts: a linear petiole up to
4 cm in length and a terminal obovate to orbicular blade
modied into a trapping mechanism up to 2 cm across
(Munz 1959). The petioles are green, hairy (sometimes
glabrous), up to 3 cm long, and contain large air spaces.
On the adaxial surface of the blade are two forms of
tentacular red stalked glands, about 200 per lamina, all
perpendicular to its surface, which secrete a glutinous,
dewdrop-like substance. The longer, sensitive stalks
located on the periphery of the leaf blade function in the
entrapment of prey whereas the short to sessile stalked
glands secrete digestive uids (Lloyd 1942).
Prey are lured to the traps by the plant’s
brilliant reddish coloration, which is a result of a high
concentration of the pigment plumbagin in the petioles
Figure 1. Key Drosera rotundifolia structures. Source: Watson and Dallwitz (2000), used with permission).
Drosera.
Diagram.
Drosera.
Fruit (mag.).
Drosera.
Vertical section of ower (mag.).
Drosera. Seed (mag.).
Sundew. (Drosera rotundifolia.)

12 13
and glandular hairs (Swales 1975). The leaves of
Drosera rotundifolia possess a unique mechanism for
bending: once entrapment has occurred, the leaf petiole
folds over the captured prey preventing the escape of
the insect (Darwin 1875). This is brought about by the
hyponasty of a more or less narrow zone of the petiole
at the base of the blade (Lloyd 1942).
The species’ root structure is brous, ne, and
blackish with two or three slightly divided branches
from about 1.3 to 2.5 cm in length. A fugacious taproot
fails to elongate but swells into a rounded mass covered
with root hairs (Lloyd 1942). As the shoot develops,
adventitious roots are put out from the stem producing
secondary rosettes, and as the stem decays they become
separated and function as asexual propagules.
The inorescence of Drosera rotundifolia is
a single, one-sided, cymose raceme that terminates
in a naked, glabrous scape 5 to 12 cm in height. The
owers are white, 10 to 12 mm in diameter, radially
symmetrical (actinomorphic), and 15 to 25 owers
occur on each owering scape (Figure 1). The owers
are hermaphroditic and have a calyx composed of a
series of ve united, oblong, obtuse, and imbricated
sepals that are 4 to 5 mm long and a corolla that is
composed of ve free, imbricated, ephemeral, and
spatulate petals that are slightly longer than the sepals.
The androecium includes ve stamens that have free,
liform laments and extrorse anthers (Weeden 1975).
The calyx, corolla, and stamens are persistent.
Pollen tetrads are 60 µm across, with single
grains 35 µm, exine with spines about 3 to 5 µm; the
spinules are dimorphic, the smaller 0.5 µm and more
frequent, the larger 2 µm long (Erdtman et al. 1963,
Chanda 1965). The gynoecium is described as a three
part, hypogynous, superior ovary with three free
styles (Munz 1959). The plant produces a 3-valved
loculicidally dehiscent capsule containing numerous
black, ovoid, sigmoid-fusiform seeds 1.0 to 1.5 mm
long with ne longitudinally striate markings that
shine with a metallic luster (Abrams 1944). The fruit
frequently persists entire, freeing the seeds when it rots.
The spindle-shaped seeds have a mean air-dry weight of
10 to 20 µg (Crowder et al. 1990).
Distribution and abundance
Drosera is a widely distributed genus, with
over 90 species occurring globally. The center of
diversity is Oceania, with over 40 species found in
southwest Australia alone (Juniper et al. 1989). Drosera
rotundifolia is one of the most broadly distributed
Drosera species, occurring throughout much of the
Holarctic (Figure 3; Hulten 1968, Schnell 2002).
In Eurasia, D. rotundifolia’s range extends from
Kamchatka, Japan, and the Korean peninsula in the east
through Siberia into Scandinavia, the British Isles, and
Iceland in the west (Crowder et al. 1990).
Drosera rotundifolia is broadly distributed in
North America; occurrences are found throughout
Canada and in 35 U.S. states, from California in the
west, through the northern Great Plains, the Great Lake
states, and along the East and Gulf coasts (Schnell
2002, NatureServe 2004). Notably, the distribution of
D. rotundifolia closely matches the main distribution of
peat-forming ecosystems in North America (Figure 4).
Peatlands are wetlands that accumulate peat soils over
time due to decomposition rates that are slower than
organic carbon input rates from primary production and
allochthonous sources.
Of the three recognized North American
varieties, Drosera rotundifolia var. rotundifolia is
the most widespread throughout North America and
the only variety that occurs in Region 2. The other
Figure 2. Rosette and leaves of Drosera rotundifolia. Photograph by E. Wolf.

14 15
Figure 3. Distribution of Drosera rotundifolia in the northern hemisphere. Occurrences in any given region tend to
be localized and can be widely separated from adjacent occurrences. Note that the Region 2 occurrences, in Colorado,
are widely disjunct from other known occurrences.
Figure 4. Distribution of main peat-forming areas in the continental United States. Source: USDA Natural Resources
Conservation Service (1999), used with permission.

14 15
two, D. rotundifolia L. var. gracilis Laestad and
D. rotundifolia L. var. comosa Fern, have limited
distributions, occurring only in Alaska and the northeast
United States, respectively (USDA Natural Resources
Conservation Service 2002).
Only seven locations supporting Drosera
rotundifolia occurrences have been reported in Region
2, and all of these are from National Forest System
lands in Colorado (Figure 5, Table 1). Four of these
occurrences have been veried; sites 1 and 2 are from
Jackson County, site 5 is from Grand County, and site 7
is from Gunnison County (Table 1). These occurrences
are disjunct from one another and from occurrences
outside of Region 2 (Figure 5). The three unveried
occurrence records (sites 3, 4, and 6 in Table 1) are each
based on a single Colorado Natural Heritage Program
account. A recent attempt to eld verify site number 6
(Figure 5) failed to nd any D. rotundifolia or suitable
habitat (Popovich personal communication 2006). For
this reason, the occurrence of D. rotundifolia at site 6 is
probably a false report. In light of the probable falseness
of the site 6 report, sites 3 and 4 should be considered
non-occurrences until they are eld checked and a D.
rotundifolia occurrence is veried.
Globally, Drosera rotundifolia is found across
a broad elevation range, from near sea level to nearly
3,000 meters (Crowder et al. 1990, Colorado Natural
Heritage Program 2004a). Region 2 occurrences and the
peatlands they occupy are at relatively high elevation,
2,680 to 2,930 meters, because the relatively warm
and dry climate of the region limits peat accumulation
rates in most low elevation sites (Cooper 1996). Stable
and consistently high water tables are necessary for
peat accumulation and thus for D. rotundifolia, and
these occur only in favorable microclimatic and
hydrogeomorphic settings, which are limited within
Region 2.
Abundance estimates for Region 2 occurrences
are generally lacking, but some rough estimates exist
for two of the seven sites. Rocchio and Stevens (2004)
estimated that approximately 1,000 to 2,000 plants
occurred at site 5 in Grand County. Steve Popovich
(personal communication 2006), recalls that this site
contained thousands more plants in 2004 than the
Rocchio and Stevens estimate. In addition, he recently
estimated that the Jackson County site 1 occurrence
supports approximately 10,000 plants (Popovich
personal communication 2006). This occurrence covers
1,980 square meters (0.49 acres) and is the largest
documented occurrence of Drosera rotundifolia in
Region 2. The population estimate for this single site
exceeds the state-wide estimate of 5,000 to 7,000
total plants given by Rocchio and Stevens (2004) and
underscores the difculty of making a regional estimate
with the current lack of local abundance data. (There
are no rigorously collected census data supporting these
limited estimates of local abundance.)
Population trends
Estimates of Drosera rotundifolia occurrence
sizes in Region 2 are mostly anecdotal. Most of the
known locations have been rarely visited since initial
collection or observation, and no quantitative data are
available to condently estimate population trends.
The Gunnison County iron fen occurrence was the
rst occurrence discovered in Colorado, and the fen it
occupies is perhaps the best understood hydrologically
and geochemically (Cooper 2003). Although the fen
has been extensively studied (Fall 1997, Cooper et al.
2002, Cooper 2003), no research has focused on D.
rotundifolia specically, and no estimates of the number
of individuals have been made.
The occurrence in Grand County was estimated
to support 1,000 to 2,000 individuals in 2002 and
2003 (Rocchio and Stevens 2004) or perhaps many
thousands (Popovich personal communication 2006).
A visit on September 3, 2004, by David Cooper and
Steve Popovich found fewer than 10 plants, indicating
enormous interannual variance in the number of
individuals. The fen has recently had a dramatic increase
in anthropogenic disturbance, due largely to visitor
trampling. However, it is unclear how signicantly this
inuences occurrence size and variability. Anomalously,
cool and wet conditions during the summer of 2004
may also have inuenced population size, perhaps by
inuencing seed germination and adult plant emergence
(Popovich personal communication 2004).
Reproductive biology and autecology
Reproduction
Drosera rotundifolia can reproduce both sexually
and asexually. Asexual reproduction occurs when leaf
buds form plantlets. Alternatively, axillary buds found
below the rosette can form a secondary rosette, with two
genetically identical individuals resulting following the
decay of the joining stem.
Sexual reproduction is achieved almost exclusively
through self-pollination of the hermaphroditic owers
(Engelhardt 1998). Cross-pollination and genetic
recombination are rare, so nearly all reproduction

16
17
Figure 5. Distribution of Drosera rotundifolia within USDA Forest Service Region 2. Four of the seven occurrences
reported have voucher specimens deposited in herbaria (red pentagons); the remaining three sites are identied in
Colorado Natural Heritage Program (2004a) records, but are unsubstantiated by voucher specimens or photographs
(blue circles). Information for individual locations, ordered by site number, is provided in Table 1. Sources: Colorado
Natural Heritage Program, Rocky Mountain Herbarium, Colorado State University Herbarium, University of
Colorado Herbarium.

16
17
Table 1. List of USDA Forest Service Region 2 herbaria and Colorado Natural Heritage Program (CNHP) element occurrence records
for Drosera rotundifolia. Multiple records (e.g., herbaria and CNHP) exist for several occurrences. The locations of occurrences listed
in the table are linked via the map key number to Figure 5.
Record source Map key In-text reference
Accession/
record number Management Collector
Record/
collection date
CNHP 1 Jackson County
site 1
PDDRO02070*007 Routt National
Forest
N. Barrett 9/1/1992
CNHP 1 Jackson County
site 1
PDDRO02070*005 Routt National
Forest
N. Barrett and M.
Zimmerman
8/13/1996
University
of Colorado
Herbarium
1 Jackson County
site 1
499695 Routt National
Forest
N. Lederer 7/28/2001
University
of Colorado
Herbarium
2 Jackson County
site 2
443092 Routt National
Forest
B. Neely and A. Carpenter 8/3/1989
Colorado State
University
Herbarium
2 Jackson County
site 2
53451 Routt National
Forest
B. Neely and A. Carpenter 8/3/1989
CNHP 2 Jackson County
site 2
PDDRO02070*002 Routt National
Forest
B. Neely and H. Richter 8/22/1991
University
of Colorado
Herbarium
2 Jackson County
site 2
468751 Routt National
Forest
J. Sanderson 9/10/1997
CNHP 3 Unveried site 3 PDDRO02070*009 Routt National
Forest
C. Stafford and C. Quinn 7/3/1996
CNHP 4 Unveried site 4 PDDRO02070*008 Routt National
Forest
S. Franklin 7/1/1996
Colorado State
University
Herbarium
5 Grand County 84788 Arapaho National
Forest
S. Popovich 7/15/2002
CNHP 5 Grand County PDDRO02070*010 Arapaho National
Forest
J. Rocchio and J. Stevens 8/1/2003
CNHP 6 Unveried site 6 PDDRO02070*006 Arapaho National
Forest
C. Samuelson 6/1/1993
University
of Colorado
Herbarium
7 Gunnison County 318670 Gunnison National
Forest
B. Johnston et al. 8/4/1978
University
of Colorado
Herbarium
7 Gunnison County 429567 Gunnison National
Forest
W. Weber 6/22/1987
University
of Colorado
Herbarium
7 Gunnison County 318660 Gunnison National
Forest
W. Keammerer et al. 7/23/1987
University
of Colorado
Herbarium
7 Gunnison County 58042 Gunnison National
Forest
B Johnston et al. 8/4/1978
Rocky Mountain
Herbarium
7 Gunnison County 339954 Gunnison National
Forest
B. Johnson 8/4/1978
CNHP 7 Gunnison County PDDRO02070*001 Gunnison National
Forest
B. Johnston et al. 6/22/1987

18 19
– vegetative or sexual (seeds) – results in offspring
that are either genetically identical to the parent (via
vegetative reproduction) or that contain an equal, or
slightly reduced, genetic variability compared to the
parent generation (via sexual self-pollination).
Life history and strategy
Drosera rotundifolia, like other carnivorous
plants (as dened by Givnish 1984), derives a signicant
proportion of its nutrients, most importantly nitrogen,
from the absorption of animal tissue. The independent
evolution of carnivory in multiple, diverse plant families
suggests that it is an adaptation to the nutrient poor
habitats where carnivorous plants are found (Givnish et
al. 1984). This adaptation to attract and consume insects
is physiologically costly (Thoren et al. 2003), and the
photosynthetic cost of the investment in carnivory is
only offset in sunny, wet settings. Thus in open, water-
saturated, low nutrient environments, carnivory confers
an important competitive advantage in the ability to
obtain nutrients without an overwhelming cost to
photosynthesis (Ellison and Gotelli 2001).
Drosera rotundifolia can capture and digest a
wide range of arthropods. In a study of prey capture
by different Drosera species, D. rotundifolia trapped
individuals from over 13 different arthropod orders,
with Dipterans (ies) being the most common prey type
(Figure 6).
Studies to determine the proportion of carnivory-
derived nitrogen within Drosera rotundifolia plants have
produced values ranging from 26.5 percent (Schulze
and Schulze 1990) to 50 percent (Millett et al. 2003).
The increased consumption of nitrogen that carnivory
provides has been shown to benet plant growth,
owering, and seed production; it does not, however,
produce an increase in the rate of photosynthesis
(Mendez and Karlsson 1999).
Charles Darwin showed that ower and seed
production in Drosera rotundifolia increased with
articially elevated feeding rates (Darwin 1878).
Other investigations have corroborated the correlation
between increased prey consumption and increased
growth (Thum 1988, Krafft and Handel 1991, Thoren
and Karlsson 1998). However, D. rotundifolia can
grow, survive, and reproduce in the absence of prey.
One study (Stewart and Nilsen 1992) found that there
was no difference in growth between plants where
insects were excluded and plants that trapped prey.
The study was conducted in a relatively high-nutrient
peatland, and it is likely that their ndings indicate that
this D. rotundifolia occurrence is not nutrient limited.
This study appears to be the exception in a wide array
of literature that demonstrates that the nitrogen derived
from carnivory aids plant growth at the time of capture
and into the future. In a separate study it was found that
24 to 30 percent of the nitrogen stored over winter in
the hypocotyl of D. rotundifolia leaves originated from
insect capture during the previous growing season
(Schulze and Schulze 1990).
While Drosera rotundifolia (and other carnivorous
plants) may be able to subsist for the duration of a
Figure 6. Arthropod diversity of Drosera rotundifolia prey. Data from Achterberg (1973), as presented in Juniper et
al. (1989), used with permission.

18 19
scientic study without the nutrients absorbed from
insects, their long-term, evolutionary strategy for
survival appears dependent on carnivory (Ellison and
Gotelli 2001).
Pollinators and pollination ecology
Drosera rotundifolia is an autogamous (self-
pollinating) species. Throughout most of its range,
the owers of D. rotundifolia never open, and these
plants reproduce through cleistogamy (self-pollination
within unopened owers) (Crowder et al. 1990).
Chasmogamous owers (open owers with exposed
reproductive structures) do occur, but they are only
open for about two hours during the brightest sunlight
for each of the three to seven days that they persist
(Engelhardt 1998). The stigmas and anthers of open
owers are often intertwined or in close proximity,
potentially enhancing the possibility of autogamy
(Murza and Davis 2003).
Pollen to ovule ratios and observation data
regarding pollinator visitation indicate that little to no
cross-pollination occurs via wind-dispersed pollen or
entomophily (insect pollination) (Murza and Davis
2003). All reported pollen to ovule ratios are low and
fall within the ranges reported for cleistogamy and
autogamy (Cruden 1977). Low pollen ratios indicate a
pollination strategy that does not rely on transporting
pollen between owers, which is a low probability event
for which copious pollen is benecial. Additionally,
Drosera rotundifolia does not possess functional
nectaries, which serve to attract insect pollinators. A
study of insect visitation to a chasmogamous occurrence
in California reported no activity that would result in
pollen transport (Engelhardt 1998).
Dispersal mechanisms
Drosera rotundifolia has no specic long distance
dispersal mechanism, but seeds may be distributed by
owing water, wind, or animals. The seeds are able to
oat for a week to several months on a water surface,
owing to trapped air within their testa (Ridley 1930,
Swales 1975, Crowder et al. 1990, Engelhardt 1998).
Their small weight allows them to be blown a short
distance by gusts of wind. Foraging animals such as
deer or bear may ingest seeds and defecate them at a
different location. The small, light seeds may also stick
to birds’ feet or feathers, or mammals’ fur as they move
past the plant (Crowder et al. 1990).
Seed viability and germination requirements
A persistent soil seed bank is reported for Drosera
rotundifolia (McGraw 1986, Poschlod 1995). This seed
bank may be especially important in establishing D.
rotundifolia following disturbance. The seeds are
viable for up to four years (Crowder et al. 1990). The
highest germination rate (95 percent) was achieved with
seed that was stored for eight weeks in a moist, dark
environment at 10 °C and then kept in a greenhouse
with 14 h of daylight between 18 to 22 °C. The optimal
germination conditions for maximum seedling survival
were light, wet storage, and 16 weeks of cold treatment
followed by alternating warm temperatures (Crowder et
al. 1990).
Engelhardt (1998) found that while cold
stratication is not necessary for germination, it does
increase germination success. In his study of Drosera
rotundifolia in Sequoia National Park, CA, he achieved
mean germination rates of 26 to 57 percent for several
treatments. The germinability of D. rotundifolia
seeds rapidly decreases with burial depth greater
than approximately 5 mm (Figure 7; Cambell and
Rochefort 2003).
Cryptic phases
During its up-to-ve-year lifespan, Drosera
rotundifolia passes through two life stages that may be
considered cryptic: dormant seeds within the soil seed
bank (Crowder et al. 1990) and over-wintering dormant
buds, called hibernacula (Figure 8). The soil seed bank
may be especially important in recolonization following
disturbance (Jacquemart et al. 2003). Hibernacula are
formed beginning in July and consist of two to eight
spirally inrolled leaves wrapped in divided stipules.
Over winter the remains of the previous summer’s
leaves surround the hibernacula. The onset of cold
temperatures triggers dormancy, and warm temperatures
rejuvenate growth (Crowder et al. 1990).
Mycorrhizal relationships
Vesicular-arbuscular mycorrhiza are reported
from a study in Czechoslovakia (Mejstrik 1976).
Hybridization
Hybridization within the Droseraceae appears
fairly common and has been used to explain the origin

20 21
of several Drosera species. Wood (1955) hypothesized
that D. anglica originated as a hybrid between D.
linearis and D. rotundifolia. However, a recent
comparison of oral structure nds no evidence to
support this assertion (Murza and Davis 2003).
Where they co-occur, Drosera rotundifolia has
been shown to hybridize with D. anglica (Hulten 1968).
The resulting hybrid, Drosera x obovata Mert. & Koch,
is sterile and exhibits morphology intermediate between
the parent species (Wood 1955, Schnell 2002). Since no
other species of Drosera are present in Colorado, where
all known occurrences of D. rotundifolia in Region 2
exist, hybrids are unlikely (NatureServe 2004).
Demography
The only demographic data available for Drosera
rotundifolia in Region 2 are the estimates of the number
of individuals in the Grand County occurrences, which
are addressed in the above Population trends section.
Figure 7. Seed germination of Drosera rotundifolia in relation to burial depth. Modied from Cambell and Rochefort
(2003), used with permission.
Figure 8. Hibernacula of Drosera rotundifolia. Photograph by D. Rice, used with permission.
100
80
60
40
20
0
5 10 15 20
Germination (%)
Burial depth (mm)

20 21
Mortality of Drosera rotundifolia is strongly size
dependent; it is high for seedlings, low for the smallest
mature rosettes, and high for the largest mature rosettes.
In a Norwegian population of D. rotundifolia, more
than half of the plants were seedlings, and seedling
mortality ranged from 45 to 85 percent (Nordbakken
et al. 2004). This high mortality likely resulted from
the very shallow roots of the seedlings being unable to
acquire sufcient water from a dynamic water table. In
addition to the ability of rosettes to become established,
another important population growth factor for D.
rotundifolia is the ability of mature plants to survive.
Since mature plants live up to ve years and rosette size
is positively correlated with age (Crowder et al. 1990),
high mortality rates in large individuals probably occur
because they have reached their maximum lifespan.
Larger plants produce most of the viable seed (i.e.,
fecundity is positively correlated with rosette size).
During the ve years of observation in the Norwegian
study, mortality and fecundity varied greatly between
years. Temporal variation was much greater than
variation along the studied gradients of depth to water
table and peat-producing ability (similar to primary
productivity) (Nordbakken et al. 2004).
Life history characteristics
We have identied four main life stages for
Drosera rotundifolia: seed, seedling, mature plant, and
vegetative propagule. In addition to these four primary
stages are two dormant (or cryptic) phases, the soil seed
bank and the overwintering hibernacula. The transitions
between these six life stages are depicted in Figure
9, which summarizes the life stages and processes
discussed in the preceding sections. Since rst-year
seedlings do not reproduce (Nordbakken et al. 2004),
they must spend one year growing and overwintering
(as hibernacula) and then re-emerge as mature plants
capable of reproduction.
Ecological inuences on survival and
reproduction
Within fen and bog settings where Drosera
rotundifolia occurs, temporal and spatial uctuations
in water availability and competition with other plants
can signicantly inuence on the growth and survival
of the species. In a Norwegian study of D. rotundifolia,
temporal variation in climate had a more signicant
inuence on population growth rate than plant position
along two major environmental gradients, depth to
water table (DWT; Figure 10) and peat production
ability (PPA; Figure 10). The low growth rate during
the second one-year-period (OYP 2; 1996-1997) was
caused by higher mortality of mature rosettes and
lower than normal fecundity, apparently brought about
by unfavorable climatic conditions. These conditions
included two growing season months (May and August,
1997) with over 200 percent of normal precipitation.
It is possible that such increases in water may dilute
what little nutrients are available to bog and fen plants
and thus reduce their tness. Wetter than average years
may also increase the depth and duration of inundation
and lead to ooding-related mortality, such as anoxia.
Additionally, cooler than normal temperatures may
reduce the availability of insect prey (Nordbakken et
al. 2004).
Figure 9. Life cycle diagram for Drosera rotundifolia.

22 23
Nordbakken et al. (2004) found signicant
differences in growth rates along both of the
environmental gradients although they were less
important than the previously mentioned temporal
variation. Moderately-productive peatlands (PPA
classes 2 and 3) appear to be the most favorable classes
within the gradient because they represent the optimal
balance between water supply (which is less regulated
in low productivity sites with poor capillary rise) and
burial by Sphagnum moss growth in highly productive
sites. The low population growth rate of Drosera
rotundifolia in the moderately shallow water table class
(DWT class 2; 5.7 to 8.5 cm) indicates its sensitivity to
inundation in hollows. The signicantly higher growth
rate on hummocks with deeper water tables (DWT class
4; 13.4 to 43.0 cm) shows a preference to sites within
the capillary fringe.
The episodic occurrence of unfavorable climate
conditions regulated Drosera rotundifolia growth
in ombrotrophic bogs. Occurrences only rarely and
locally reached sufcient concentrations where density-
dependent birth and mortality rates regulated population
size (Nordbakken et al. 2004).
Genetic characteristics and concerns
Drosera rotundifolia chromosomes (2n = 20)
can be extracted using a relatively simple technique
(Bekesiova et al. 1999). The ability to isolate the specic
genes that produce agriculturally useful traits and
medically important chemicals underscores the need for
a better understanding of the natural genetic variability
within and among populations of D. rotundifolia, in
order to preserve critical genetic resources (Kamarainen
et al. 2003).
Genes from Drosera rotundifolia have been used
to genetically engineer carnivorous traits in potato
plants (Associated Press 1999) with the hope that the
trapping tentacles will provide both pest protection and
extra nitrogen for agricultural species. However, the
signicant physiological costs to the plant of growing
and maintaining such specialized structures may
outweigh their benets (Ellison and Gotelli 2001).
Drosera rotundifolia produces the chemicals
7-methyljuglone and plumbagin, both of which
are napthaquinones. The specic function of these
secondary compounds in D. rotundifolia is unknown,
but napthaquinones are known to be antifungal,
antibiotic, antiviral, and allelopathic (Gu et al. 2004).
For humans, these compounds have potential for use
in chemotherapy, but they may be carcinogenic. The
chemicals create superoxides, which are toxic to certain
bio-molecules. It is unclear whether 7-methyljuglone
and plumbagin have a great enough margin of safety
for pharmacological use, so they have been nominated
for further medical study (National Institute of Health
2000). Extracts from D. rotundifolia and other Drosera
species have long traditions of use as folk medicines.
A preliminary study on the genetic variability of
Drosera rotundifolia indicates little genetic variation
within and between three Colorado occurrences and one
from California (Cohu 2003). The lack of variability
within occurrences is expected for species whose
primary mode of reproduction is asexual, such as D.
rotundifolia, due to a lack of genetic recombination.
The lack of variability between the Colorado
occurrences and the distal and disjunct occurrence
in California may indicate that these occurrences are
Figure 10. Population growth rate (λ, +99% condence intervals) for each of four one-year-periods (OYP1-OYP4)
and quartiles for depth to water table (DWT) and peat production ability (PPA). Source Nordbakken et al. (2004),
used with permission.

22 23
the peripheral remnants of a once-larger and more
connected metapopulation. Peripheral populations at
the extremes of a species’ spatial range can exhibit very
low genetic diversity within peripheral populations and
between other peripheral populations (Durka 1999).
Commercially available specimens of Drosera
rotundifolia exhibited much greater genetic diversity
than any of the plants sampled from natural populations
(Table 2). This indicates that greater diversity occurs
within D. rotundifolia’s range, and broader genetic
sampling could reveal patterns of diversity that may
illuminate the ancestry and origins of the occurrences in
Region 2 (Cohu 2004).
Factors limiting survival and reproduction
Climatic conditions (i.e., moisture, temperature)
are the primary controls of Drosera rotundifolia
population size and growth. Populations are rarely and
only locally regulated by density-dependent recruitment
and mortality rates (Nordbakken et al. 2004). Numerous
studies have conrmed the importance of prey as a
limiting factor for various tness parameters (Thum
1988, Thum 1989a, Krafft and Handel 1991, Thoren
and Karlsson 1998).
Community and ecosystem ecology
General habitat characteristics
Drosera rotundifolia is an obligate wetland
species that requires continuously moist or saturated
soils and is found in sites with shallow water table depths
(Reed 1988). The roots cannot tolerate desiccation, and
the rooting zone (<6 cm below ground surface) must
remain moist to saturated. Drosera rotundifolia can
withstand ground frost with its leaves uncurled, and
this occurs often within its boreal distribution (Crowder
et al. 1990). Throughout its range, D. rotundifolia is
typically found in nutrient poor peatlands including
ombrotrophic (rain-fed) bogs, poor fens, and along the
margins of acidic ponds (Juniper et al. 1989, Crowder
et al. 1990, Schnell 2002). Although typically occurring
in acidic environments, the species is also known from
intermediate-rich and extreme-rich fens, which have
circumneutral to slightly basic pH, and occasionally
from wetlands with mineral, as opposed to organic,
substrates (Szumigalski and Bayley 1997). The species
occurs in both continental and maritime climates
(Haslam 1965, Glaser 1987, Hotes et al. 2001). The
plant prefers full sun but can survive in some shade.
Shaded individuals growing within Sphagnum moss
mats do not form rosettes but have long axes (Crowder
et al. 1990).
True bogs, which are ombrogenous (rain
generated) and ombrotrophic, are hydrologically
supported solely by precipitation and receive nutrients
largely through wet and dry atmospheric deposition.
Consequently, these habitats are oligotrophic with
respect to nutrient availability and support species
adapted to acidic, nutrient-poor conditions (Damman
1986, Crum 1988, Vitt et al. 1995). Sphagnum moss
species typically dominate the ground cover (Glaser
et al. 1981, Andrus 1986), and their ability to actively
exchange ions is a signicant control on the pH,
nutrient availability, and oristic composition of most
bogs and fens (Andrus 1986, Mitsch and Gosselink
2000). Because of the relatively warm and dry climate
in Region 2, peatlands form only where sufcient
groundwater or surface water maintains saturated soil
conditions throughout the summer (Cooper 1996).
Thus, no true bogs occur in Region 2. However,
Sphagnum-dominated fens are found in the region, and
these share many oristic elements with ombrotrophic
bogs and poor fens, including the occasional presence
of Drosera rotundifolia.
A broad scale assessment of fens in the
Sierra Nevada of California indicated that Drosera
rotundifolia is much more common there than in
Table 2. Genetic variability at 13 loci of Drosera rotundifolia from Colorado and California occurrences, where
n = sample size; A = average number of alleles per locus; P = percentage of polymorphic loci; Ho = observed
heterozygosity; He = expected heterozygosity. Source: Cohu (2004), used with permission.
Occurrence nA P HoHe
Gunnison County, Colorado 30 1.08 0.0 0.08 0.04
Central Colorado 30 1.08 0.0 0.08 0.04
Northern Colorado 30 1.08 0.0 0.08 0.04
California 30 1.08 0.0 0.08 0.04
Purchased plants 30 1.08 0.0 0.23 0.12

24 25
Region 2 (Cooper and Wolf unpublished data). In
addition, D. rotundifolia occurred more frequently
in northern and lower elevation California fens that
received higher annual precipitation (Figure 11).
The precipitation distribution of the Sierra Nevada is
strongly skewed towards winter snow, with less than
10 percent of the total annual precipitation occurring
in summer, a marked contrast to the Rocky Mountains
where summer rain may be abundant.
Since Drosera rotundifolia is intolerant of
desiccation, it survives only in sites with stable
groundwater inputs that maintain water tables
near the soil surface. Winter snow and summer
rain recharge hillslope aquifers, which discharge
consistently throughout long, warm summers. The
abundance of D. rotundifolia occurrences that
ourish during the mostly rainless Sierra Nevada
summer underscores the species’ restriction to sites
with constant groundwater discharge.
The four principal landform congurations that
produce groundwater discharge systems capable of
supporting fens in mountain regions of the western
United States are discrete hillslope springs, upwelling
springs, closed basins, and open-basin hillslopes.
At discrete springs, groundwater is discharged on
hillslopes where a fracture system or bedrock contact
is exposed at the surface. If the springs are associated
with a sufciently large aquifer, the discharge may
be perennially stable and support a fen (Figure
12). Upwelling springs often form at or near the toe
of hillslopes where coalescing groundwater ow
paths cause water to reach the ground surface. If fen
vegetation completely overgrows and contains an
upwelling spring, the vertical hydraulic pressure of
the emerging water will be held by the entwined mat
of roots and peat, forming a spring mound (Figure 13).
In closed basins where groundwater discharge collects
in a lake, oating vegetation mats can form, starting at
the lakeshore or on fallen logs and encroaching inward.
Fens may grow a short distance up the shore slope if
the capillary fringe and/or upslope springs provide
sufcient perennial water (Figure 14). Finally, fens
most commonly form on sloping surfaces near the base
of hillslopes where groundwater discharge coalesces but
does not form a perennial lake. Hillslope aquifers, often
in unconsolidated material such as talus or glacial till,
may store sufcient groundwater to produce a steady,
diffuse discharge that supports fen formation (Figure
15). The Jackson County site 1 and Grand County
Drosera rotundifolia occurrences grow on oating
mats in closed basins (Figure 14) while the Gunnison
County occurrence is located in an open-basin sloping
fen (Figure 15).
Ellenberg indicator values (IV) are a rating
system relating species afnities for particular
environmental characteristics such as light, nutrients,
and water availability. European ecologists commonly
use this approach. In a comprehensive assessment of
the British ora, Hill et al. (1999) characterized Drosera
rotundifolia as an indicator of wet (IV = 9 out of 12) and
nitrogen-decient (IV = 1 out of 9) sites. With regard
to pH, D. rotundifolia occurred in acid sites, but not
exclusively, giving the species an IV of 2 out of 9 for
soil reaction (Hill et al. 1999).
Elevation Precipitation Lattitude
Elevation (m) and precip (mm)
0
500
1000
1500
2000
2500
3000
3500
Degrees of lattitude
34
36
38
40
42
D. rotundifolia absent
D. rotundifolia present
Figure 11. Boxplot comparison of environmental variables in Sierra Nevada fens where Drosera rotundifolia was
present and absent.

24 25
Figure 12. Illustration of hillslope fens associated with a bedrock contact (shown in cutout) or a bedrock fracture
(indicated by dashed red line).
Figure 13. Illustration of upwelling groundwater at the toe of a hillslope supporting a spring mound fen.
Figure 14. Illustration of a closed basin where groundwater feeds a lake that supports a oating mat fen.

26 27
Substrate characteristics and microhabitats
Throughout the world Drosera rotundifolia
occurs on peat, particularly on living Sphagnum moss,
but it can occur on oating logs or damp acidic sand
near ponds or streams (Swales 1975, Crowder et al.
1990). Drosera rotundifolia in Region 2 occurs only on
living Sphagnum moss and peat generated by Sphagnum
moss. Moderately productive peat is most favorable
because it represents the optimal balance between water
supply and overgrowth by associated species, notably
Sphagnum moss (Nordbakken et al. 2004).
Within individual wetland complexes, Drosera
rotundifolia has been shown to occur in a range of
microhabitats characterized by particular physiochemical
and oristic characteristics. For example, in northern
Minnesota, which contains extensive and diverse
peatlands, D. rotundifolia occurs in a variety of habitats
including non-forested bogs, poor fen margins, strings,
and tree island habitats (Glaser 1987).
Region 2 habitat characteristics
In Region 2, Drosera rotundifolia is known from
two primary habitat types, sloping iron fens and oating
mats around small ponds. Iron fens are rare (˜ 10 known)
in the region, and only the Gunnison County fen supports
D. rotundifolia. This iron fen, located on the south slope
of a meta-sedimentary mountain in Gunnison County,
was the rst location where D. rotundifolia was found
in this region. There has been some speculation that
these plants were introduced during the 20th century.
However, the discovery of other occurrences in
Colorado and the recent work comparing the genetics of
D. rotundifolia in Colorado and California occurrences
(Cohu 2003) have claried this issue; D. rotundifolia is
certainly native in Colorado.
A water track in the Gunnison County iron fen
contains numerous, small, unvegetated pools, and
strings dominated by Carex aquatilis and Sphagnum
angustifolium (Figure 16). Small Drosera rotundifolia
occurrences are found here in areas within a nearly
continuous cover of S. angustifolium and S. mbriatum
(Cooper 2003), which both tolerate and produce strongly
acidic waters (Andrus 1986, Crum 1988). While in most
fens and bogs the acidic conditions are produced by
Sphagnum cation exchange capacity or the abundant
organic acids, in iron fens, the acids are produced by the
oxidation of iron pyrite in the watershed. Thus, iron fens
have highly acid (pH 3.0 to 4.0) water sources, and this
external source of acids controls site water chemistry.
The other three conrmed Colorado Drosera
rotundifolia occurrences, Jackson County sites 1 and 2,
and Grand County, grow on oating or poorly anchored
Sphagnum mats on pond margins (Figure 17, Figure
18). Floating mats rise and fall, with pond water levels
maintaining the water table within the mat throughout
the year. The oating mat is typically created by
Sphagnum mosses, as well as the roots of species such as
Carex limosa, C. lasiocarpa, Menyanthes trifoliata, and
Comarum palustre, all of which are rare in Colorado.
Floating mats are highly susceptible to degrad-
ation and only develop in small ponds that do not
have signicant wave action. They are isolated from
valley margins and do not directly receive inowing
groundwater. Capillary rise from the pond water
saturates oating mats, and their peat has very slow
water ux rates. Thus, the inux of mineral ions and
nutrients is very low, and Sphagnum mosses can create
localized acid conditions, even where the fen’s water
sources are neutral in pH.
Floating mats are also isolated from mineral
sediment inputs resulting from hillslope erosion, further
limiting the ion and nutrient delivery processes. Very
few species are adapted to this perennially saturated,
and ion and nutrient poor acid environment, creating
relatively little competition for Drosera rotundifolia.
Figure 15. Illustration of sloping fen that formed where groundwater ow is concentrated.

26 27
Figure 16. Photograph of the Gunnison County fen, Gunnison National Forest. Photograph by D. Cooper.
Figure 17. Example of the type of oating mat habitat that supports Drosera rotundifolia at the Grand County fen.
Photograph by J. Rocchio, used with permission.
Figure 18. Floating mat at Jackson County site 1. Photograph by B. Neely, used with permission.
Some oating mats are close enough to forest margins
that falling trees may reach the mats; these do provide
habitat for upland or other wetland plants.
The Drosera rotundifolia occurrence at Jackson
County site 1 is conned to a small area on raised
Sphagnum mats. Plants were observed within areas
of standing water, as well as at drier sites at the
western fen edge. No plants were found in areas of
tall Carex-dominated vegetation; instead plants are
conned to open, sunny locations (Cohu personal
communication 2004).
Water and peat chemistry
The importance of fens to regional and local
biodiversity is well known. Fens support many rare plant
and animal species, and unique communities (Cooper

28 29
1991, Fertig and Jones 1992, Cooper 1996, Cooper and
Sanderson 1997). The mineral ions and nutrients upon
which fen plants depend are supplied by their water
sources. Consequently, the geochemistry of bedrock
and quaternary deposits in contributing watersheds are
key controls of the fen pH and nutrient and ion delivery
(Glaser et al. 1981, Windell et al. 1986, Chee and Vitt
1989). Watersheds with limestone, dolomite, or shale
bedrock produce water that is basic in reaction (pH 7.0
to 8.5; Cooper 1996, Chapman et al. 2003), while those
composed of granitic or metamorphic rocks produce
acidic waters (Cooper and Andrus 1994).
The Gunnison County site provides a key
example of the importance of watershed geology on fen
water chemistry. This iron fen is one of approximately
10 iron fens known in the southern Rocky Mountains
(Cooper 2003). The watershed supporting the fen and
its Drosera rotundifolia occurrence is composed of
pyrite rich bedrock and talus, which, when oxidized,
forms sulfuric acid. Surface water and groundwater
owing into the fen from the upslope watershed
have exceptionally low pH values for Region 2 fens
(Figure 19). Groundwater and surface water in the
vicinity of the D. rotundifolia occurrences have a pH
of approximately 3.2 to 3.9 (Figure 19). In contrast,
groundwater discharging upward from a shale rich
lateral glacial moraine on which the fen sits has a
pH >6.0, demonstrating the complex interaction of
multiple surface and groundwater sources that may
occur in fens.
At the Gunnison County fen, the acid water
dissolves soluble metals, thus making the water
ion rich. Although iron fens may be high in certain
cations, they are still very nutrient poor with respect
to the major elements required by plants (i.e., nitrogen,
phosphorus, potassium).
While bogs and poor fens have acidic waters,
their water supply is primarily or solely rainwater,
which has low concentrations of ions. In addition,
the acids in bogs and poor fens are produced during
cation exchange by Sphagnum mosses (Cooper et al.
2002). However, bogs and poor fens support many of
the same acidic water- and soil-tolerant plant species
as iron fens, including S. fuscum, S. angustifolium, S.
russowii, S. mbriatum, Carex aquatilis, C. utriculata,
Betula glandulosa, Drosera rotundifolia, Vaccinium
scoparium, Calamagrostis canadensis, Pinus contorta,
and Picea engelmannii (Cooper 2003).
Figure 19. pH values from groundwater monitoring wells established across the fen in Gunnison County. Drosera
rotundifolia occurrences are concentrated near wells 3 and 5. Source: Cooper (2003), used with permission.
pH
Well
1 2 3 4 5 6 7
5.0
4.5
4.0
3.5
3.0
09/21/2002
07/01/2003
08/21/2003

28 29
Table 3. Comparison of water pH, calcium (Ca2+) and magnesium (Mg2+) ion concentrations (mg/L) measured in
wetlands with Drosera rotundifolia.
Study location Source pH Ca2+ Mg2+
Region 2 (Colorado)
Grand County Rocchio and Stevens 2004 5.6-6.8 Not available Not available
Gunnison County Cooper 2003 3.6-4.4 13.5-27.3 3.5-7.3
North America
Maine Anderson and Davis 1997 4.3 0.6 0.02
Alberta Chee and Vitt 1989 5.3-7.1 19.5-22.1 4.3-5.3
Labrador Wells 1996 3.9-5.0 1.8-6.0 Not available
California Cooper and Wolf unpublished data 5.0-7.4 1.0-35.4 0.1-16.7
Wisconsin Frolik 1941 4.5-7.0 Not available Not available
Minnesota Glaser et al. 1990 4.6-5.3 3.0 Not available
New York Motzkin 1994 6.5 22 Not available
Ontario Sjors 1963 4.1-5.4 2.0 0.5
Alberta Szumigalski and Bayley 1997 5.68-6.57 8.0-22.5 3.6-6.6
Alberta Szumigalski and Bayley 1997 7.8-8.4 57.8-114.5 21.4-39.9
Alberta Vitt et al. 1975 5.2 2.3 0.4
Europe
Sweden Hanslin and Karlsson 1996 4.6 Not available Not available
England Crowder et al. 1990 3.5-6.6 1.2-22 1.2-5.0
England Haslam 1965 6-7.5 30 (30-39) Not available
Netherlands Wassen and Barendregt 1992 5.5-6.5 16 (7-25) Not available
Sweden Gunnarsson et al. 2002 3.9-4.9 Not available Not available
Water chemistry data from elsewhere in the world
indicate that Drosera rotundifolia favors acidic and
low nutrient habitats, but there are exceptions (Table
3). A Norwegian study found that pH of extracted
pore waters usually range from 3.5 and 4.5, but may
be as high as 6.6 (Nordbakken et al. 2004). Cation
concentrations were generally low in fens supporting
D. rotundifolia occurrences in California, but there was
considerable variability (Figure 20). Fens in California
without D. rotundifolia were similarly variable and
generally low in cation concentrations (Cooper and
Wolf unpublished data).
Wetland hydrology
In nutrient-poor peatlands, the water table
gradient is by far the most important internal
determinant of species composition (Nordbakken et
al. 2004). Of signicant, but lesser importance, are the
peat productivity gradient (Nordbakken et al. 2004)
and grazing intensity (Cooper et al. 2001). More than
80 percent of Drosera rotundifolia plants were found
where the median water table depth was 8.9 cm (range
= 3 to 15 cm), and the plants preferred sites towards the
high end of the peat productivity gradient (Nordbakken
et al. 2004). A study of a weakly minerotrophic
montane fen in the southern Alps also demonstrated a
strong correlation between water table depth and the
presence of D. rotundifolia (Figure 21; Bragazza and
Gerdol 1996). They only found D. rotundifolia along a
relatively narrow range of water table depths, from 0 to
24 cm, while the species was present along a wide range
of pH values.
Drosera rotundifolia individuals can survive
complete inundation for several weeks (Crowder et
al. 1990), but they do not grow in sites with perennial
standing water. Germination and growth generally start
while the peatland surface is covered by melt water in
the spring. In oating mat sites, which represent the
primary environment supporting Region 2 occurrences,
hydrologic conditions are typically fairly stable despite
uctuations in lake levels, as the mat is capable of
oating up or down.

30 31
No DROTDROT
mg/L
50
40
30
20
10
0
Ca
Mg
Na
K
Figure 20. Box plots of water chemistry parameters comparing Sierra Nevada fens with Drosera rotundifolia (number
of locations, n = 22) and without D. rotundifolia (n = 39). Source: Cooper and Wolf unpublished data, used with
permission.
Figure 21. Response surface for Drosera rotundifolia along water table and pH gradients in an Italian poor fen. Values
on the vertical scale indicate predicted cover along a 10-point scale, calculated using observed cover value. Source:
Bragazza and Gerdol (1996), used with permission.

30 31
A similar hydrologic environment is present at
the Gunnison County fen. At this site, the water table
is near the surface throughout the growing season and
exhibits small annual variation (Figure 22). Although
no hydrologic data are available for the other Region 2
occurrences, they all occur on floating peat mats, and
so presumably water tables are consistently near the
soil surface.
Vegetation associations and associated plant
species
Species composition of oating mats varies but
typically includes Sphagnum mosses (principally S.
squarrosum, S. teres, and S. mbriatum), sedges (e.g.,
Carex limosa, C. lasiocarpa), and herbaceous dicots
(e.g., Menyanthes trifoliata, Comarum palustre).
Dominant species at the fen in Grand County include
Carex lasiocarpa, Sphagnum spp., Comarum palustris,
Carex interior, C. buxbaumii, and C. magellanica
(Rocchio and Stevens 2004).
Although typically associated with acidic
wetland types such as bogs and poor fens, Drosera
rotundifolia has been documented in rich fens as well.
For example, Motzkin (1994) found D. rotundifolia
in a calcareous fen associated with Carex lasiocarpa,
Myrica gale, Potentilla fruticosa, Peltandra virginica,
and Cladium mariscoides. Dominant bryophytes
Figure 22. Monitoring well and piezometer data from well 5 in the Gunnison County fen, demonstrating the stable
water table and inuence of groundwater on fen hydrology. Source: Cooper (2003), used with permission.
included Campylium stellatum, Calliergonella spp.,
and Sphagnum spp. Species in wetlands supporting
D. rotundifolia occurrences are listed in Table 4, but
it should be noted that some species might not occur in
microsites with D. rotundifolia.
Competitors and relationship to habitat
In peatlands, where Drosera rotundifolia
occurs with Sphagnum moss, competition for sunlight
can signicantly affect the size and distribution of
D. rotundifolia plants. While the small size of D.
rotundifolia plants reduces their demand for resources,
it also makes them particularly sensitive to drought and
burial by Sphagnum growth (Nordbakken et al. 2004).
Drosera rotundifolia can tolerate some shading but does
not survive in dense shade (Crowder et al. 1990).
The encroachment of Alnus spp. (alder) and
Frangula alnus (alder buckthorn) shrubs (63 to
100 percent canopy coverage) decreased sunlight
reaching a Croatian fen and caused a shift from
Rhynchospora alba and Drosera rotundifolia
dominance to Sphagnum subsecundum and Molinia
caerulea (Hrsak 1996). Although A. incana ssp.
tenuifolia (alder) are common in Region 2, they are
rarely associated with the fen types supporting D.
rotundifolia (Cooper personal observation).

32 33
Table 4. Common vegetation associates reported from wetlands supporting Drosera rotundifolia.
Study location Source Associated species
Region 2 (Colorado)
Gunnison County Cooper 2003 Sphagnum angustifolium, S. fuscum, S. russowii, S. mbriatum, Carex
aquatilis, C. utriculata, C. viridis, Betula glandulosa, Vaccinium
scoparium, Calamagrostis canadensis, Eriophorum angustifolium,
Pinus contorta, Picea engelmannii.
Grand County Rocchio and Stevens 2004 Carex lasiocarpa, Comarum palustre, Carex vesicaria, Sphagnum spp.
North America
New Hampshire Atkinson 1984 Eriophorum angustifolium, Narthecum ossifragum, Sphagnum
papillosum
California Engelhardt 1998 Sphagnum fuscum, Drosera anglica
Wisconsin Frolik 1941 Menyanthes trifoliata, Kalmia polifolia, Vaccinium spp., Sarracenia
purpurea, Eriophorum virginicum, Andromeda glaucophylla,
Chamaedaphne calyculata
Minnesota Glaser et al. 1990 Scirpus hudsonianus, Cladium mariscoides, Parnassia palustris,
Menyanthes trifoliata, Muhlenbergia glomerata, Scirpus cespitosus,
Carex lasiocarpa, Drosera anglica, D. intermedia, Carex livida,
Utricularia intermedia
New York Motzkin 1994 Carex lasiocarpa, Cladium mariscoides, Sarracenia purpurea,
Vaccinium macrocarpon, Menyanthes trifoliata, Campylium stellatum
Alberta Szumigalski and Bayley 1997 Scirpus cespitosus, Scorpidium scorpioides, Drepanocladus revolvens,
Tomenthypnum nitens
Europe
Sweden Foster and Fritz 1987 Carex rostrata, Scirpus cespitosus, Eriophorum angustifolium, Pinus
sylvestris
Sweden Hanslin and Karlsson 1996 Sphagnum spp., Rubus chamaemorus, Betula nana, Vaccinium
microcarpum, Empetrum hermaphroditum, Andromeda polifolia
England Haslam 1965 Schoenus nigricans, Carex elata, Betula spp., Cladium mariscus,
Epipactis palustris
Netherlands Wassen and Barendregt 1992 Carex echinita, Carex lasiocarpa, Potentilla erecta, Eriophorum
angustifolium, Sphagnum magellanicum, Sphagnum palustre
England Wheeler 1980 Juncus actiorus, Pedicularis sylvatica, Serratula tinctoria,
Calypogeia ssa, Cephalozia bicuspidata, Dicranella heteromalla,
Lepidozia setacea, Pohlia nutans. Erica tetralix, Nordus stricta,
Calluma vulgaris, Aulacomnium palustre, Calluna vulgaris, Erica
tetralix
Competition for growth-limiting mineral nutrients
in Sphagnum peatlands strongly inuences community
structure and species diversity. When fertilized, S.
fuscum responded by an increase in the height of its
green parts. Drosera rotundifolia also responded to
S. fuscum fertilization with an increase in height of
the vertical stem that connects the leaf rosettes of two
successive years’ growth. Thus, D. rotundifolia avoided
being overgrown and shaded by matching Sphagnum’s
vertical growth (Svensson 1995).
The ability of Drosera rotundifolia to capture and
retain insects leads to competition for critical nutrients
within occurrences and between carnivorous plants and
insect predators. In addition to the competition between
D. rotundifolia plants for limited insect resources
(Gibson 1991), ants have been observed robbing food
from the leaves of D. rotundifolia. In one study, only
29 percent of added ies remained on D. rotundifolia
leaves for more than 24 hours (Thum 1989b). Ants
showed higher activity in the warmer, sunnier, and
elevated microhabitat of D. rotundifolia compared to
that of D. intermedia. Larger plants were better than
smaller ones in retaining added ies. The advantage
of plundering appears to be greater for the ants than
the danger of being caught. The prey collected from

32 33
D. rotundifolia may be an important source of food for
peatland-dwelling ants (Thum 1989b).
Herbivores and relationship to habitat
There are few studies of herbivory on Drosera,
and none specic to D. rotundifolia in Region 2. In an
occurrence of D. capillaris in Florida, caterpillars of a
plume moth (Trichoptilus parvulus) have been found
feeding on the leaf blades, glands, and dead insects
trapped by the plant (Eisner and Shepherd 1965).
However, it is unlikely that invertebrates specialize
in consuming D. rotundifolia since occurrences are
localized and productivity of plants and occurrences
is low. However, generalist herbivores may
opportunistically utilize the plant. Drosera rotundifolia
is commonly eaten by moose on the Kenai Peninsula
of Alaska in late May and June when it is in its
preowering and early flowering stages (LeResche
and Davis 1973). Trampling effects due to large
herbivores, such as moose, elk, deer or non-native
ungulates, are likely more signicant than the impacts
of direct herbivory.
Parasites and disease
An aphid, Aphis audax Hille Ris Lambers (likely
the same as A. trichoglochinis Theobald), is known to
infest Drosera rotundifolia and was described as a pest
in the Netherlands. Whether this aphid occurs in Region
2 is unknown. There are no records of disease, but both
seeds and seedlings are attacked by fungi in culture
(Crowder et al. 1990). The large distance between
Region 2 D. rotundifolia occurrences and the lack of
effective vectors for pathogens suggest that, if present,
the effects of pathogens and parasites are small.
Symbiotic and mutualistic interactions
There are no documented examples of symbiotic
or mutualistic relationships between Drosera
rotundifolia and other organisms, except for a reference
to mycorrhizal fungi (see above). The plants are
sometimes found covered by lamentous algae, notably
Zygogonum ericetorum Kutzing, which can provide a
good medium for its germinating seeds (Nordbakken et
al. 2004).
CONSERVATION
Threats
Historically, many peatlands in Region 2 were
ditched and drained in order to create “productive
land” and to increase site suitability for cattle grazing
(Cooper et al. 1998, Johnson 2000). In addition to
these direct impacts, a variety of additional factors
have affected peatlands and presumably altered
peatland species composition. Some statistics are
available on historical rates of wetland loss at national
and state levels (Tiner 1984, Dahl 1990); however,
none of these studies have addressed changes in
peatland abundance and distribution – the wetland
type critical for Drosera rotundifolia.
Direct hydrologic alteration, such as dewatering
through ditching, fundamentally changes the ecological
properties of impacted wetlands and reduces their
suitability for obligate wetland species such as Drosera
rotundifolia. Consequently, direct hydrologic alteration
represents the single greatest historic and current threat
to D. rotundifolia occurrences, and protection of water
resources in fens is of utmost importance to preserving
the viability of the species.
At the same time, since fens are supported in large
part by groundwater, a variety of actions outside of their
immediate area can alter habitat hydrologic regimes,
sediment budgets, or water chemistry, with potentially
signicant ramications for wetland-dependent species.
The water balance of individual basins supporting
peatlands varies as a function of precipitation inputs,
evaporation and transpiration losses, and the amount
of water stored as groundwater (Mitsch and Gosselink
2000). Vegetation in surrounding uplands inuences this
balance through effects on transpiration and interception
of rain or snow, which is susceptible to subsequent loss
through evaporation or sublimation (Kauffman et al.
1997). Thus, any natural or anthropogenic process that
signicantly alters upland vegetation, for example re
or timber harvest, can impact nearby wetlands.
Timber harvest
Changes in basin vegetation cover can alter
surface runoff from basins through effects on
evapotranspiration rates and snowpack accumulation
patterns. Tree canopy removal in a Colorado subalpine
watershed increased precipitation reaching the forest
oor by approximately 40 percent and increased peak
snowpack water equivalent by more than 35 percent
(Stottlemyer and Troendle 1999, Stottlemyer and
Troendle 2001). Logging, whether clearcutting or partial
thinning, typically results in increased annual and peak
streamow in logged watersheds (Troendle and King
1987). Although the effects of increased water yield
and surface inows to peatlands are difcult to predict,

34 35
any changes in fen hydrologic regimes can potentially
produce negative effects on fen vegetation.
Increased water yield from upland portions of
peatland watersheds could generate wetter conditions,
perennially ooding microsites required by Drosera
rotundifolia. In addition, since fens in the southern
Rocky Mountains form only in physically stable
locations where stream erosion and sediment deposition
are limited, increased sediment yields resulting from the
removal of upland vegetation could increase mineral
sediment uxes to fens and therefore negatively impact
peat formation, nutrient dynamics, and water table
depths, any of which could affect D. rotundifolia.
Most water derived from snowmelt passes
through subalpine watersheds not as surface flow,
but rather as subsurface flow where soil processes
can signicantly alter its chemistry (Stottlemyer
and Troendle 1999). As a result, altered snowpack
accumulation and melt rates due to changes in upland
vegetation cover can affect water chemistry in a variety
of ways. For example, Stottlemyer and Troendle (1999)
observed signicant increases in the average snowpack
Ca2+, NO3
- and NH4
+ content, and increased K+, Ca2+,
SO4
2-, NO3-, and HCO3- flux in shallow subsurface
ows following logging treatments. The effects of
these changes in surface and subsurface flows on peat
chemistry and the consequential potential effects on
wetland flora are unknown.
Fire
The indirect effects of fire occurring in uplands
adjacent to fens supporting Drosera rotundifolia
occurrences are likely similar to those of mechanical
harvest, including increased water and sediment yield
and changes in water chemistry. As with logging,
the magnitude of these changes relative to pre-re
conditions should decrease over time as the density
and cover of upland vegetation increases (Troendle and
King 1985). Since fire has been a natural component
of Rocky Mountain landscapes for millennia (Fall
1997), D. rotundifolia is not likely to be strongly
inuenced by fire patterns that are within the natural
range of variability.
A natural re regime may play an important role
in maintaining open fen ecosystems by burning tree
and shrub species that may otherwise encroach and
shade fens (Schnell 2002). Although there are few data
available for soil temperature and re duration mortality
thresholds for Drosera rotundifolia, the species has been
characterized as tolerant of and even opportunistically
dependent on low-temperature res; it has even been
found colonizing recently burned peat (Brewer 1999).
Since fens typically remain saturated throughout
the year, their ability to support res is low relative
to drier upland areas. In addition, re return intervals
characteristic of the subalpine forests surrounding
Region 2 fens are relatively long compared to many
boreal landscapes (Cooper and Van Haveren 1994,
Sherriff et al. 2001), suggesting that re has had, at
most, an episodic role in the population dynamics of the
region’s Drosera rotundifolia occurrences.
Signicant departure from historic mean re
return interval could lead to a degradation of Drosera
rotundifolia habitat. A reduction of re return interval
due to more frequent burning could result in an
increase in both water and sediment yield within a
given watershed while an increase in re return interval
may reduce water yield and lead to the encroachment
of woody plants into fens. In addition to these direct
impacts on water availability and shading, longer
re return intervals may increase the probability of a
high severity re, which may have exaggerated direct
and indirect impacts within a watershed. Since D.
rotundifolia requires a narrow range of water table
depths and is sensitive to shading and burial, any
signicant change in re frequency has the potential to
inuence the suitability of affected wetlands to support
D. rotundifolia.
Roads and trails
Roads, and to a lesser degree, trail networks can
have signicant effects on local and watershed-scale
hydrologic processes, and can therefore have indirect
impacts on fens supporting Drosera rotundifolia
occurrences. Roads, trails, and their associated
engineering structures such as culverts and ditches can
alter natural drainage patterns, reduce interception and
inltration rates due to the removal of vegetation and
soil compaction, and alter the hydrologic response of
basins to both annual snowmelt runoff episodes and
isolated convective storm events (Jones 2000, Forman
and Sperling 2002). Increased overland ow typically
results in a more rapid and extreme hydrologic response
to precipitation events, potentially increasing erosion or
sediment transport and deposition in affected systems.
Road and trail networks can have a variety
of additional effects on wetlands, including the
introduction of pollutants and the alteration of water
chemistry (e.g., conductivity, cation concentrations,
pH) due to road dust, increased sediment deposition,

34 35
and chemicals used in road maintenance such as deicing
agents, magnesium chloride, or other dust abatement
chemicals (Wilcox 1986, Trombulak and Frissell
2000). Since the road density near Region 2 Drosera
rotundifolia occurrences is relatively low, these impacts
likely represent a minor threat to these occurrences, but
there are no data available to support this assessment.
However, if road densities increase, introduction of
sediment and other foreign material to peatlands could
negatively impact D. rotundifolia.
Because most Region 2 Drosera rotundifolia
occurrences are found on oating mats, an environment
less likely to be strongly affected by pulses of water
or sediment than sites located along fen margins, the
effects of altered watershed hydrologic processes
(i.e., water yield and sediment transport) due to roads
and trails on D. rotundifolia may be modest. More
signicant, perhaps, is the increased possibility of a
denser road network intercepting and diverting spring
discharge that feeds into fens.
The increased disturbance and access resulting
from roads and trails can indirectly affect wetlands by
promoting the spread of non-native plants (Parendes
and Jones 2000) and by providing easier human access
(Gelbard and Belnap 2003). Several exotic species
are capable of invading wetlands, particularly those
which have been altered hydrologically (Wilcox 1995).
However, even in disturbed wetlands, weeds have
not been observed in the wet and acidic microsites
supporting Drosera rotundifolia occurrences,
suggesting that this specic effect is likely to be minor.
Roads and trails facilitate human access to fens and may
increase anthropogenic disturbance and the likelihood of
discovery of D. rotundifolia occurrences by collectors.
Although USFS regulations prohibit driving in
peatlands, damage from off-highway vehicles (OHVs)
has been documented. An example is the September
2000 “mudfest” near the Roosevelt National Forest
in Colorado, where several hundred OHVs caused
severe damage to a fen complex. In addition, OHV
use in or near wetlands may contribute pollutants
from inefcient combustion and engine emissions
(Havlick 2002). Though certainly a factor contributing
to the degradation of some fens, there is no evidence to
suggest a direct threat to Region 2 Drosera rotundifolia
occurrences from OHV use. However, even a single
OHV could cause signicant damage if driven directly
onto a D. rotundifolia occurrence.
Peat extraction
Because of its high porosity and water holding
capacity, peat has a variety of horticultural and
agricultural applications, including use as a lawn and
garden soil amendment and for turf maintenance on
golf courses. Industrial applications include use as a
ltration medium for waste-water and sewage efuents
and, in its dehydrated form, as an absorbent for fuel
and oil spills on both land and water (World Energy
Council 2004).
Sites possessing the necessary hydrologic
conditions for peat accumulation are fairly rare in
Region 2 because of its relatively dry climate (Chimner
and Cooper 2003). Indeed, with the exception of
the northern Great Lakes region and portions of the
northeastern United States and the Atlantic seaboard,
peatlands form only a small component of the total land
cover nationally. Not surprisingly then, peat production
in the United States is small relative to global production.
In 2002, for instance, the United States produced 642
metric tons of peat, less than 3 percent of world peat
production (DiFrancesco and Jasinski 2005).
In Colorado there are currently three active peat-
mining claims, which cover a total of 47.7 hectares of
land, and 17 inactive claims. None of these 20 claims are
within the three counties that have Drosera rotundifolia
occurrences (Colorado Division of Minerals and
Geology 2006).
The large energy output of peat has made it an
attractive source of energy, at least locally in areas
supporting large peatlands. However, interest in the
United States in developing peat resources for energy
purposes has diminished since its peak in the 1970’s,
due in part to the relatively low price of natural gas and
oil, and the development of environmental regulations
protecting wetlands. Although no reliable statistics are
available, peat production for agricultural, horticultural,
and energy uses in Region 2 is likely small due to the
availability of inexpensive imports from outside of
the region (primarily Canada) and various regulations
limiting peatland development. Consequently, peat
mining currently appears to represent a minor threat to
known Drosera occurrences in the region. However, the
recent rise in oil prices has fueled a shift in the focus of
national and local energy policy towards other sources
of energy. If the new focus were to include peat and if
peat mining were to resume, it would represent a serious
threat to D. rotundifolia.

36 37
Mineral development
Mineral extraction activities, including hard
rock mining and oil and natural gas extraction, do
not appear to pose an imminent threat to Drosera
rotundifolia occurrences, with the likely exception of
the Gunnison County fen population. Areas upslope
of the fen have been mined, and more extensive
molybdenum deposits are known to occur. The inow
of acidic groundwater critical to maintaining the low pH
required by D. rotundifolia and other rare acidiphiles
such as Sphagnum balticum could be reduced if large-
scale mining resumes, and this could cause a shift in the
fen’s hydrogeochemical balance towards the less acidic
groundwater discharged from the underlying lateral
moraine (Figure 23; Cooper et al. 2002, Cooper 2003).
Livestock and native ungulate grazing
The effects of livestock grazing on Drosera
rotundifolia, at both the individual and community
levels, are largely unknown. Drosera rotundifolia has
been shown to respond positively to some forms of
disturbance, likely due to its high light requirements
and relatively poor competitive ability. For example,
a mowing treatment in a Belgian rich fen, designed to
simulate the effects of early-season grazing, resulted in
a signicant increase in the frequency of D. rotundifolia
(Vyvey 1992). Since the oating mat environments
characteristic of Region 2 D. rotundifolia occurrences
are perennially wet, livestock may use them somewhat
less. However, even modest livestock use can punch
holes through the oating mat and destroy the root and
rhizome systems of plants that form it. Since oating
mat plants are all slow growing, this can expose soils to
oxidation and result in peat loss.
Native ungulates can also have signicant effects
on wetlands and possibly impact Drosera rotundifolia
occurrences. Moose and/or elk trampling was also
noted at the Grand County fen, and local levels of
ungulate use appear higher than historic use, based
on observations of willow browse patterns (Popovich
personal communication 2004).
Recreational impacts
Recreational impacts to fens are typically due
to trampling. Users include fisherman, native plant
enthusiasts, and hikers that come to the edge of
oating mats to enjoy the open views, reections,
unusual colors, and to attempt fishing. The Grand
County fen was recently acquired by the Arapaho
National Forest and opened to recreational use. A rapid
increase in visitor trafc has occurred since this fen
was written up in an area hiking guide, and this has
led to severe trampling in areas that support a large
Drosera rotundifolia occurrence (Figure 24; Cooper
personal observation).
Visitation from hikers and campers has also been
identied as a potential threat for the Jackson County
site 1 occurrence (Proctor personal communication
2004). The area supporting Drosera rotundifolia occurs
Figure 23. Schematic cross-section of the Gunnison County fen supporting Drosera rotundifolia. Groundwater
discharging into the fen from the bedrock of the meta-sedimentary mountain to the north (right side of the gure)
is strongly acidic. However, the fen has formed upon a lateral moraine composed of circumnuetral and alkaline
till derived from the West Elk Mountains, from which it receives inputs of groundwater with high pH. Since D.
rotundifolia appears to be limited to the sites with low pH, any signicant hydrologic alterations reducing the inux
of acidic groundwater from the meta-sedimentary mountain, such as mining of known molybdenum deposits, could
drastically alter the suitability of the site for the species.

36 37
Figure 24. Effects of trampling from recreational users on the oating mat of the fen in Grand County. Steve
Popovich, botanist for the Araphaho-Roosevelt National Forest is looking at the brown, exposed peat. (Photograph by
D. Cooper, September 3, 2004, used with permission).

38 39
within 20 m of a frequently used hiking trail and is less
than  km from a developed campground, making
access particularly easy.
The Gunnison County fen receives moderately
high recreational and educational use from locals,
researchers, and tourists (Cooper personal observation).
There are no documented impacts on Drosera
rotundifolia from winter recreation such as cross county
skiing, snowshoeing, or snowmobiling. However,
compaction of accumulated snow from winter
recreation has the potential to impact the species by
causing later spring melt and altered peat temperatures,
effectively reducing the length of the growing season
for plants (Cooper unpublished data). Winter recreation,
snowmobiling in particular, has been identied as a
potential threat to D. rotundifolia occurrences on the
Routt and Arapaho national forests (Popovich and
Proctor personal communication 2004).
Over-collection
Human use of Drosera species for medicinal
purposes has a long and interesting history. The
‘perpetual dew’ of sundews has long been valued as an
herbal remedy for a wide variety of ailments. Accounts
from as early as the 16th century document the use of
Drosera-based tinctures to treat such varied maladies
as “consumption, swooning, and faintness of harte”
(William Turner 1568, cited in Juniper et al. 1989).
Additional historical accounts describe its use as an
aphrodisiac and as a remedy for complaints of old age,
arteriosclerosis, corns and warts, whooping cough,
and small pox (Juniper et al. 1989). Modern herbalists
prescribe D. rotundifolia as a diuretic, a laxative, and
a treatment for a variety of kidney, stomach, and liver
problems. The potential value of D. rotundifolia as an
herbal remedy may create an incentive for collection,
particularly as commercial markets exist for D.
rotundifolia tinctures and compounds. Although no
documented occurrences of collections for this purpose
are known from Region 2, the limited distribution and
abundance of D. rotundifolia suggest that collection
could represent a serious threat.
In addition to their use as herbal remedies,
Drosera species have long held the interest of botanists
and horticulturists because of their unique biology and
carnivorous habit. There is an active trade in carnivorous
plant species, and several organizations such as the
International Carnivorous Plant Society exist to support
the culture of carnivorous plants. Through advocacy
and support for research and conservation, carnivorous
plant enthusiasts clearly benet the species they love.
However, it is conceivable that individuals could collect
wild occurrences, with serious negative consequences.
The Colorado occurrences of D. rotundifolia are small
enough that they could be over-collected in a single
harvest visit.
In response to the threat posed by over-collection
of sensitive plants, the Montana State Legislature
and USFS Regions 1 and 4 have adopted a collection
moratorium on six medicinally popular plants, including
all species of Drosera (National Forest Service 1999).
Exotic species
Although exotic species are generally recognized
as one of the principle threats to the integrity of
ecological systems (Mack et al. 2000, Crooks 2002),
there is no evidence to suggest that Drosera rotundifolia
is directly threatened by exotic species within Region 2.
None of the state or county-listed noxious weed species
listed in Colorado are noted in habitat descriptions of
known occurrences (Cooper 2003, Rocchio and Stevens
2004). Although exotics such as Canada thistle (Cirsium
arvensis) may invade fens (Blumenthal and Jordan
2001), this is typically associated with hydrologic
alterations such as ditching. In addition, the iron fen
and oating mat environments supporting Region 2 D.
rotundifolia occurrences do not appear conducive to
weed invasion.
Atmospheric deposition of pollutants
In nutrient-poor environments, Drosera
rotundifolia may have a competitive advantage over
co-occurring species due to its ability to assimilate
nitrogen from invertebrates (Thum 1986, Stewart
and Nilsen 1992, Nordbakken et al. 2004), and as a
consequence, it may be vulnerable to the increased
deposition of airborne nitrogen observed in portions
of Region 2 (Svensson 1995). A wide variety of
ecological responses have been shown to result from
nitrogen deposition, but no studies have focused on fens
specically. Although large areas of land are exposed to
low levels of atmospheric nitrogen deposition, hotspots
of elevated nitrogen deposition occur downwind of
large metropolitan centers or signicant agricultural
operations (Fenn et al. 2003). Consequently, nitrate
concentrations in surface waters west of the Continental
Divide have generally been found to be lower than those
in surface waters east of the Divide. However, elevated
amounts of atmospheric nitrogen deposition have been

38 39
observed in the Mt. Zirkel Wilderness on the Routt
National Forest, which is near several D. rotundifolia
occurrences (Burns 2002).
Climate change
Given the role of climate as a primary control
on the majority of hydrogeomorphic, biogeochemical,
and ecological processes, large-scale climatic shifts,
whether due to natural or anthropogenic forces, may
have profound effects on the structure and function
of the wetlands supporting Drosera rotundifolia.
Potential changes include altered plant community
composition and productivity, changes in disturbance
regimes, and modication of key hydrologic
variables (Hogenbirk and Wein 1991, Naiman and
Turner 2000, Brinson and Malvarez 2002, Moore
2002, Poff et al. 2002). Both positive and negative
feedback are possible, complicating predictions of
individual species or community and ecosystem
responses (Weltzin et al. 2000).
Because of their strong dependence on watershed-
scale hydrologic processes, wetlands, and fens in
particular, may be especially sensitive to major shifts
in either temperature or precipitation. The sensitivity
of Drosera rotundifolia to desiccation suggests that the
warmer regional temperatures predicted under some
global climate change scenarios (U.S. Environmental
Protection Agency 1998) may adversely affect the
species. Increased precipitation, called for by some
models, may offset the negative hydrologic effects of
warmer temperatures, but still have a negative effect on
the viability of D. rotundifolia occurrences by shifting
the delicate balance between D. rotundifolia and its
competitors (Nordbakken et al. 2004). For instance,
Moore (2002) found that production of graminoids and
herbaceous dicots increased in response to rising water
table elevation; this higher productivity could result
in greater competition between D. rotundifolia and
associated vegetation.
Ultimately, the most important climatic factor
inuencing the future of peatlands in the region is
likely to be the spatial and temporal patterns of future
precipitation (Moore 2002). Because of the region’s
climate, areas capable of accumulating peat are rare
on the landscape and rates of peat formation are slow,
approximately 20 cm per 1000 years (Chimner et al.
2002, Chimner and Cooper 2003). The disjunct nature
of Region 2 Drosera rotundifolia occurrences, widely
separated from other occurrences and suitable habitats,
suggests that the fate of the species in the region
is intimately tied to that of the wetlands presently
supporting it – the conclusion reached for other rare fen
species in the region (Cooper 1991).
Assessment of threats to Region 2 Drosera
rotundifolia populations
In Table 5, we present a qualitative assessment
of the importance of different threats to known Region
2 Drosera rotundifolia populations. Unfortunately, few
data are available from which to condently make these
evaluations. Assessments should therefore be viewed as
initial hypotheses in need of more research.
Conservation Status of Drosera
rotundifolia in Region 2
Drosera rotundifolia has been given sensitive
status in Region 2 principally because of its rarity and
Table 5. Estimates of the relative importance of various threats to USDA Forest Service Region 2 Drosera rotundifolia
occurrences. The map key corresponds to occurrences presented in Figure 5. The signicance of threats are qualitatively
assessed as either high (H - threat imminent or ongoing), intermediate (I - not imminent or ongoing, but signicant
chance of future impact), or low (L - no apparent present impact, small likelihood of future threat). Question marks are
used where there is no information available to make an assessment.
Threats
Map key
Logging/
re
Roads/
trails Mining Grazing
Exotic
species
Direct hydrologic
alteration
Climate change/
Pollution
Recreational
impacts
1 L I L L L L I I
2 L I L L L L I I
3 ? ? ? L ? L I I
4 ? ? ? L ? L I I
5 L H L I L L I H
6 ? ? ? ? ? ? ? ?
7 I I H H L I I H

40 41
the sensitivity of its habitat to alteration. However,
there are insufcient data available to make conclusive
statements regarding trends in the abundance of D.
rotundifolia within Region 2. Because occurrences
are so small and isolated, periodic drought during
the Holocene may have led to local extirpation of D.
rotundifolia occurrences in areas in Region 2 where D.
rotundifolia does not now occur. Extirpation could also
occur as a natural byproduct of successional changes
associated with terrestrialization of basin fens. As ponds
with oating mat fens gradually ll in with organic and
mineral sediment, the oating mat becomes a solid peat
body dominated by tall Carex spp. that can outcompete
D. rotundifolia.
There is still uncertainty as to the specic
origin of Region 2 Drosera rotundifolia occurrences.
However, the global distribution for D. rotundifolia
mirrors that of many other subalpine and alpine species
in the southern Rocky Mountains, suggesting a similar
biogeographic origin (Cooper et al. 2002, Weber
2003). Weber (2003) argued that the contemporary
high mountain ora has been in place since Tertiary
times, and that it predates the modern boreal oras.
His hypothesis, based on the distributions of a variety
of vascular and cryptogamic species, is contrary to
the generally accepted concept articulated by Axlerod
and Raven (1985), which suggests that many disjunct
subalpine and alpine species in the region originated by
migration from northern sources during major glacial
periods or from the upward migration of pre-adapted
lowland taxa. Instead, Weber (2003) suggests, “the
major mountain masses of the Northern Hemisphere
have been populated by modern species of plants
dating from the Tertiary, these mountain masses were
formerly sufciently well-connected, possibly over
larger land connections across what is now the arctic
region, to permit large areas for many species, and that
present endemism has come about through restrictions
of the formerly extensive ranges”. Although Weber’s
discussion does not specically address D. rotundifolia,
this species’ distribution is similar to many of the
examples he cites, and if his hypothesis is correct, then
it is likely that D. rotundifolia has been present in the
region for far longer than what was suggested by earlier
biogeographic theories.
Regardless of their origin, the small number and
highly disjunct nature of Region 2 occurrences, the fens
supporting them, and the limited dispersal distances
that are likely typical for Drosera species, suggest that
existing occurrences require protection and no new
occurrences are likely to form. Although diminutive,
D. rotundifolia are distinctive plants and not likely to
be overlooked or misidentied in botanical surveys,
as is common for many Carex species and bryophytes.
However, since no systematic survey of Region 2
fens has been conducted, it is certainly possible that
additional undocumented occurrences could be found.
The recent discovery of the occurrence in Grand County
serves as an example (Rocchio and Stevens 2004). As a
consequence, all fens need to be carefully evaluated for
the presence of D. rotundifolia prior to signicant shifts
in management.
The primary functional elements of Drosera
rotundifolia’s habitat that need to be conserved in
order to ensure the persistence of the species are the
hydrologic regime, the integrity of the peat body, and
the lack of mineral sediment or nutrient deposition.
Since the hydrologic regime represents the single
greatest inuence on fen ecology, actions with the
potential to alter water and sediment ux into fens,
such as trail cutting, road building, forest harvesting,
prescribed re, or water diversions, need to be critically
evaluated early in project planning, and effects should
be monitored following implementation.
Relatively long-term, stable hydrologic
processes support fens and the plants that grow in
them, including Drosera rotundifolia. This hydrologic
stability leads to stable rates of primary production
and decomposition the net results of which are
accumulations of peat. Because peat accumulation
rates in the Rocky Mountains are approximately 20
cm per millennium (Chimner et al. 2002, Ford et
al. 2002), the presence of signicant peat bodies
indicates relatively constant physical and hydrologic
conditions over thousands of years. This suggests that
fens supporting Region 2 D. rotundifolia occurrences
may be relatively resilient to small to intermediate
disturbances in the surrounding landscape.
However, activities within fens that disrupt
microsite stability, such as the heavy trampling at
the Grand County fen, can have serious impacts on
localized Drosera rotundifolia occurrences. Although
these impacts may not jeopardize the long-term
functioning of the fen as a whole, given such slow
rates of peat accumulation, the direct, local impacts
may be a signicant source of mortality within the D.
rotundifolia occurrence.
The physical characteristics of the peat body
help to maintain the necessary range of capillarity,
bulk density, and water holding capacity to produce
the edaphic, hydrologic, and geochemical conditions
necessary for peatland vegetation such as Drosera

40 41
rotundifolia. Even small amounts of mineral sediment
deposition within a fen can exceed the slow rate of
peat accumulation and rapidly change the physical
character of the peat body. Given the slow rates of peat
accumulation, a single signicant sedimentation event
could affect surface vegetation for centuries.
Likewise, small inputs of nutrients, especially
nitrogen, from aerial deposition or livestock excrement,
can dramatically change the nutrient balance in the
characteristically nutrient-poor peatland habitats
that support Drosera rotundifolia. Any signicant
fertilizing effect from a nutrient source would favor
more generalist competitors over the carnivorous fen
specialist, D. rotundifolia.
Management of Drosera rotundifolia
in Region 2
Implications and potential conservation
elements
First and foremost, maintaining the integrity of
the fens supporting Region 2 Drosera rotundifolia
occurrences is essential to ensuring the long-term
survival of the species in the region. Specically,
this includes minimizing anthropogenic impacts to
hydrologic, sediment, and disturbance regimes that
result from management actions. Since fens in the
region and their sensitivity to anthropogenic impacts
are generally poorly understood, basic hydrologic and
vegetation data need to be collected prior to, during, and
following any signicant change in management.
Since perennial groundwater inow is the critical
driver of the hydrologic and geochemical processes
leading to peat formation, maintaining the hydrologic
integrity of basins surrounding fens supporting Drosera
rotundifolia occurrences is critical. The Gunnison
County fen provides a good example. Pollen and peat
stratigraphy evidence suggest that the Gunnison County
fen is over 8,000 years old (Fall 1997). The unique
hydrologic, geochemical, and ecological environment
found in this site has served as a refugium for several
rare species, including D. rotundifolia (Cooper 2003).
As discussed in the Threats section of this assessment,
the ultimate persistence of these species depends upon
maintaining stable inows of acidic water from the
watershed. Any reduction in this water source, as might
occur if areas upslope are mined, would likely increase
the inuence of circumneutral water discharging into
the fen, thereby altering the geochemical conditions of
the site and decreasing the viability of the habitat for
acidophiles (Figure 23). Since Region 2 occurrences
of D. rotundifolia are so isolated from one another, the
potential for replenishment of these unique occurrences,
if lost, is very low.
In addition to minimizing hydrologic alterations,
management actions that result in physical trampling
of peatlands that support Drosera rotundifolia need
to be avoided. For instance, dramatic population
declines at the Grand County site between 2003 and
2004, coincident with a steep increase in human use,
highlight the importance of maintaining the integrity
of peat bodies supporting D. rotundifolia occurrences.
The potential long-term trend towards greater native
ungulate use at the site may also threaten the integrity
of oating mats supporting D. rotundifolia. Though the
relative importance of human foot trafc, ungulate use,
and interannual climate variation is not known, foot and
hoof prints are clearly having an impact on the site.
Tools and practices
Field checking of unveried Drosera rotundifolia
occurrences is important to the conservation of the
species as knowledge of its distribution and abundance
is critical to management decisions and monitoring
efforts. Identication of potential habitat is also
fundamentally important since it may reveal previously
unknown occurrences as well as dene the areas where
extirpated occurrences may have existed. An important
conservation tool available to the USFS is the continued
listing of D. rotundifolia as a sensitive species.
Designation of the fens that support D. rotundifolia in
Region 2 as Research Natural Areas, Botanical Special
Interest Areas, or other special areas may help to initiate
necessary information gathering efforts. In addition,
these designations may confer land use and activity
restrictions that could be benecial to the long-term
viability of the species.
Applying management tools to known impacts
on the hydrology, peat body integrity, or sediment and
nutrient balance at fens supporting Drosera rotundifolia
may both improve the conditions of the occurrences and
provide the opportunity for monitoring the response of
the species to changes in human activity. Closing or
rerouting trails that are producing qualitative impacts
to the D. rotundifolia occurrences at present may
help to reduce damage from trampling and collecting.
Placement of signs at occurrences that instruct visitors
about the detrimental effects to fens and vegetation may
reduce careless trampling, or it may draw the attention
of collectors to the site. Terminating grazing permits or
fencing off livestock access to fens with D. rotundifolia
may reduce both physical impacts to the peat body and

42 43
nutrient additions from excrement. Acquiring all water
rights for the water sources of the fens that support D.
rotundifolia would ensure that the USFS regulates all
relevant water diversions.
An evaluation of forest harvesting, mining,
road maintenance, water diversion, and other land
management activities within the watersheds containing
Drosera rotundifolia occurrences may offer other
insights into opportunities to monitor the response of
the species to changes in activity level. Implementation
of these management tools may generate valuable
information and are likely to benet D. rotundifolia and
the fen habitats that support it.
Availability of reliable restoration methods
There are few studies of fen restoration in the
Rocky Mountain region. However, the limited research
that has been conducted suggests that restoration of
fen vegetation is contingent upon effective restoration
of wetland hydrology (Cooper et al. 1998, Cooper and
MacDonald 1999). Typically this requires removing
obstacles or diversions in the groundwater ow systems
that support fens. Unfortunately, few studies have
identied suitable plant propagation and establishment
approaches for peatland species, and apparently none
for Drosera rotundifolia.
Information Needs and Research
Priorities
All Drosera rotundifolia occurrences in Region
2 were discovered within the past few decades,
demonstrating the importance of surveying fen habitats
for this species. Based on distributional similarities
to other subalpine and alpine oristic elements in the
region, it is likely that the species was at one time more
widely distributed than at the present. As a consequence,
there may be yet more occurrences awaiting discovery.
A broad regional inventory of fens would be of great
value, increasing our understanding of D. rotundifolia’s
distribution and conservation status. Since fens
support a large number of rare species in addition to
D. rotundifolia, such a broad-scale effort would also
signicantly benet our overall understanding of
biodiversity in the region.
Remote sensing data, such as color infrared
and natural color aerial photographs, in conjunction
with existing land cover and vegetation data sets
available on many national forests, could be used to
identify potential habitat. Remotely-sensed products
such as high resolution hyperspectral imagery offer
additional powerful means of identifying wetlands
and could be useful for stratifying wetlands on
the basis of their hydrology and vegetation. The
oating mats characteristic of the majority of Region
2 Drosera rotundifolia occurrences exhibit distinct
spectral signatures and could be readily identied for
eld inventory.
Since most existing records lack data regarding
population size, comprehensive demographic surveys
of known occurrences need to be conducted in order
to better evaluate the current status of Drosera
rotundifolia occurrences and to provide baseline
data critical for future monitoring efforts. Previously
surveyed occurrences need to be periodically
monitored in order to identify potential trends in
abundance and distribution.
A variety of methods could be used in surveying
efforts. Although qualitative methods such as
photopoints can provide useful indicators of broad
changes to habitat (e.g., major drying or ooding of
wetlands, woody plant encroachment), quantitative
methods of estimating occurrences are far more
reliable for developing initial population estimates and
for estimating population trends. Although Drosera
rotundifolia is easily identied anytime during the
growing season, monitoring visits timed to coincide
with owering and fruiting would provide additional
information important for population modeling.
It is also of critical importance that more
environmental data be collected for fens supporting
Region 2 occurrences of Drosera rotundifolia. Of
particular importance are hydrologic and geochemical
characterizations of sites that are known to support the
species. Wetland hydrologic regime is the principal
variable governing the functioning of fens and their
dependent flora. More data are needed to characterize
seasonal and annual water table fluctuations in relation
to surface and groundwater inputs and climatic
uctuations. A more thorough and comprehensive
understanding of the hydrogeologic setting of fens
supporting D. rotundifolia occurrences is also
important since this would provide key information
needed to assess how management activities carried
out in the broader watershed may affect fen hydrology
and water chemistry.
Because of the small number of Region 2
occurrences and their disjunct distribution, issues of
genetic integrity need to be addressed by future research
conservation strategies. Each of the fens supporting
Region 2 occurrences has a unique developmental

42 43
history driven in large part by their specic
hydrogeochemical and climatic setting. Although
preliminary studies indicate that Region 2 occurrences
are extremely similar genetically (Cohu 2003), it is still
possible that individual occurrences may contain unique
alleles, and occurrence extirpation might result in the
loss of important genetic diversity.
Because of the large importance of physical
drivers on wetland function, personnel knowledgeable
about wetland hydrology are an essential part of teams
evaluating the implications of different management
activities on fens. Their input, along with that of a
botanist or plant ecologist, is critical in developing
ecological models, identifying targets and threats, and
developing management and monitoring plans. The
effects of management need to be evaluated in relation
to key ecological factors, and these factors need to be
assessed at multiple spatial scales.
Since heavy foot trafc occurs at the Grand
County fen, a long-term analysis is needed to determine
the effects of trampling on Drosera rotundifolia.
This would include an annual census and an analysis
of the soil seed bank. It is critical to understand the
characteristics of D. rotundifolia seed production,
dispersal, and storage in soils, and how trampling
inuences these processes.

44 45
DEFINITIONS
Adaxial – nearest to or facing toward the axis of an organ or organism; “the upper side of a leaf is known as the adaxial
surface” [syn: ventral] [ant: abaxial].
Adventitious – of, or belonging to, a structure that develops in an unusual place (e.g., adventitious roots).
Allochthonous – originating from outside the system; not formed on–site.
Androecium – the stamens of a ower considered as a group.
Anoxia – a pathological deciency of oxygen.
Anther – pollen-bearing structure part of stamen.
Axillary – located in an axil (the upper angle between the stem and a lateral organ, such as a leaf).
Bog – an ombrotrophic peatland (i.e., one deriving water and nutrients solely from precipitation); typically acidic and
dominated by Sphagnum mosses.
Calyx – the collective term for sepals.
Capillary fringe – that zone of soil immediately above the water table that acts like a sponge, sucking water up from
the underlying water table and retaining this water somewhat tenaciously; soil pores act like capillary tubes.
Chasmogamous – of, or relating to, a ower that opens to allow for pollination.
Corolla – portion of ower comprised of petals.
Cymose – having a usually at–topped ower cluster in which the main and branch stems each end in a ower that
opens before those below it or to its side.
Dehiscent – the spontaneous opening at maturity of a plant structure (e.g., fruit, anther, sporangium) to release its
contents.
Dormancy – a period of growth inactivity in plants observed even when suitable environmental conditions for growth
are present.
Endangered – a species, subspecies, or variety likely to become extinct in the foreseeable future throughout all of its
range or extirpated in a signicant portion of its range.
Entire – having a margin that lacks any serrations.
Extrorse – facing outward.
Fen – a minerotrophic peatland (i.e., one deriving water and nutrients from groundwater that has been in contact with
mineral substrate); typically more basic and contain more cations than bogs.
Fugacious – withering or dropping off early.
G1/S1 ranking – critically imperiled globally or subnationally because of extreme rarity (ve or fewer occurrences or
very few remaining individuals) or because of some factor making it especially vulnerable to extinction (NatureServe
2004).
G2/S2 ranking – imperiled globally or subnationally because of rarity (6 to 20 occurrences) or because of factors
demonstrably making a species vulnerable to extinction (NatureServe 2004).
G3/S3 ranking – vulnerable globally or subnationally throughout its range or found locally in a restricted range (21 to
100 occurrences) or because of other factors making it vulnerable to extinction (NatureServe 2004).
G4/S4 ranking – apparently secure globally or subnationally, though it may be quite rare in parts of its range,
especially at the periphery (NatureServe 2004).
G5/S5 ranking – demonstrably secure globally or subnationally, though it may be quite rare in parts of its range,
especially at the periphery.

44 45
Glabrous – lacking hairs, trichomes, or glands; smooth.
Gynoecium – the female reproductive organs of a ower; the pistil or pistils considered as a group.
Herbaceous – plant lacking an aboveground persistent woody stem.
Hibernacula – dormant, overwintering, (hibernating) leaf buds of Drosera rotundifolia.
Holarctic – of, relating to, or being the zoogeographic region that includes the northern areas of the earth and is
divided into Nearctic and Palearctic regions.
Holotype – the single specimen designated as the type of a species by the original author at the time the species name
and description was published.
Hybridization – the result of a genetic cross between two species.
Hypocotyl – the part of the axis of a plant embryo or seedling plant that is below the cotyledons.
Hyponasty – an upward bending of leaves or other plant parts, resulting from growth of the lower side.
Iron fens – fens characterized by acidic, iron-rich water that is derived from groundwater sources in contact with iron
pyrite-rich rock.
Lectotype – a specimen chosen by a later researcher to serve as the primary type. It is chosen from among the
specimens available to the original author of a name when the holotype was either lost or destroyed, or when no
holotype was designated.
Loculicidally – (“Loculicidal”): longitudinally dehiscent along the capsule wall between the partitions of the locule,
as in the fruits of irises and lilies.
Mycorrhiza – a fungus involved in a symbiotic association with plant roots.
Obovate – egg-shaped, with the narrower end near the point of attachment.
Obtuse – blunt, with sides coming together at an angle greater than 90 degrees.
Oceania – the islands of the southern, western, and central Pacic Ocean, including Melanesia, Micronesia, and
Polynesia. The term is sometimes extended to encompass Australia, New Zealand, and the Malay Archipelago.
Oligotrophic – lacking in plant nutrients and having a large amount of dissolved oxygen throughout; used of a pond
or lake.
Ombrogenous – having rain as its only source of water.
Ombrotrophic – term referring to wetlands hydrologically supported by precipitation alone.
Peatland – any one of several different wetland types that accumulates partially decomposed organic matter (peat).
Poor fen – weakly minerotrophic, acidic peatland with pH ranging from 3.8 to 5.7.
Pistil – the seed-producing organ of a ower, consisting of a stigma, style, and ovary.
Pollen – the male spores in an anther.
Population Viability Analysis – an evaluation to determine the minimum number of plants needed to perpetuate
a species into the future, the factors that affect that number, and current population trends for the species being
evaluated.
Propagule – unit capable of creating a new individual; can be sexual (e.g., seed) or asexual/vegetative.
Pubescent – bearing hairs.
Recruitment – the addition of new individuals to a new size or age class.
Rosette – radial arrangement of leaves, typically originating at a basal position.
Scape – erect leaess ower stalk growing directly from the ground as in a tulip [syn: ower stalk].

46 47
Sensitive species – species of concern designated by the USDA Forest Service due to downward trends in population
numbers, density, or habitat capability.
Sepals – a segment of the calyx.
Sigmoid-fusiform – doubly curved, like the letter S, and tapering at each end (spindle–shaped).
Spatulate – spoon-shaped.
Stamen – the pollen-producing organs of a ower.
Superoxides – highly reactive compounds produced when oxygen is reduced by a single electron. In biological
systems, they may be generated during the normal catalytic function of a number of enzymes and during the oxidation
of hemoglobin to methemoglobin. In living organisms, superoxide dismutase protects the cell from the deleterious
effects of superoxide.
Talus – accumulation of coarse rock debris, often at the base of cliffs, or steep slopes.
Tentacular – of, relating to, or resembling tentacles
Testa – the often thick or hard outer coat of a seed.
Threatened – a species, subspecies, or variety in danger of becoming endangered within the foreseeable future
throughout all or a signicant portion of its range.
Water track – a zone in which minerotropic water is channeled across the body of a peatland.

46 47
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