Content uploaded by Vincent R. Farallo
Author content
All content in this area was uploaded by Vincent R. Farallo on Jul 26, 2016
Content may be subject to copyright.
The Importance of Microhabitat: A Comparison of Two Microendemic Species
of Plethodon to the Widespread P. cinereus
Vincent R. Farallo
1
and Donald B. Miles
1
Understanding the role of microhabitats in the ecology of plethodontid salamanders is of utmost importance in the
light of recent climate change. Plethodontid species are inherently susceptible to rising temperatures and drier
conditions as they utilize cutaneous respiration. Furthermore, many species of plethodontid salamanders have
restricted ranges, including species limited to single mountain tops, increasing the consequences of environmental
change as their ability to disperse is limited. In this study we compare microhabitat data for a broadly distributed
salamander species, Plethodon cinereus, and two microendemic species P. sherando and P. hubrichti. Our analyses evaluate
two hypotheses. First, each of these species occupies microhabitat that differs from the available habitat. Second,
microhabitat selection of the two microendemic species diverges from the widespread P. cinereus. In addition to testing
these hypotheses, we provide additional data to highlight the importance of quantifying thermal microhabitats at
different scales. Both P. cinereus and P. sherando were found in microhabitats that differed from randomly selected
microhabitats. Moreover, P. cinereus occurred in habitats with high relative humidity and cooler air temperatures,
whereas P. sherando occurred in habitats with warmer air temperatures but cooler substrate temperatures. These
results suggest that habitat selection may play a role in the persistence of the range of P. sherando in contact zones with
P. cinereus. Our data suggest that there may be habitat use differences between P. cinereus and P. hubrichti, but a limited
sample size prevents us from making any firm conclusions. We also demonstrated variation in temperatures available in
different microhabitats, which highlights the need to better understand microhabitat use as well as how these
microhabitats will be affected by climate change.
Amajor question in ecology concerns the factors that
determine the distribution of species (Brown, 1984;
Rosenzweig, 1995; Werner et al., 2014). Abiotic and
biotic factors may jointly interact to generate a mosaic of
environments that structure the potential distribution of a
species.Formanyspecies(particularlyinectotherms),
climate and abiotic conditions may be the primary drivers
of a species distribution (Davis and Shaw, 2001; McCarty,
2001; Walther et al., 2002). Characterizing a species distri-
bution has taken on new urgency as ecologists and
conservation biologists struggle to predict biotic responses
to climate change.
Most analyses of species distributions focus on a niche-
theoretical framework to elucidate the factors constraining
habitat occupancy of a species (Werner et al., 2014).
However, this approach emphasizes habitat characteristics
in coarse detail in order to use modern statistical methods to
predict a species range using occurrence data. Species
distributional models that use species presence data in
conjunction with an ensemble of environmental data have
been used to predict species responses to changing climates
(Fitzpatrick et al., 2013). Recent methods have incorporated
physiological and energetic data to refine (Kearney and
Porter, 2004, 2009) and predict species ranges (e.g., Buckley
et al., 2010).
Macroscale models of species distributions may provide the
ability to forecast the distribution of widespread species.
However, modeling the niche characteristics of microen-
demic species requires abiotic and biotic data at a finer
resolution. A first step entails quantifying those factors
affecting the performance of a species. Moreover, the
selection of variables should include environmental aspects
that are likely to affect a species population growth rate. In
ectothermic organisms, linking habitat variation to popula-
tion growth rates can be accomplished by modeling how the
thermal environment affects physiological performance.
Because performance is known to influence key components
of fitness (e.g., growth, survivorship, and reproduction),
quantifying those environmental attributes that may deter-
mine the ability of an individual to attain a physiologically
active temperature is a first step. Huey (1991) presented a
schema illustrating how the abiotic environment may
impinge on an organism’s fitness via T
b
. We have modified
the schema to include cutaneous water loss, combined with
T
b
, as ‘‘filters’’ which can impact an organism’s fitness.
Jointly, these two variables may affect physiological capaci-
ties, such as locomotor performance (e.g., Preest and Pough,
1989; Titon et al., 2010). Individual variation in physiolog-
ical performance has fitness consequences by affecting
growth rates (Sinervo, 1990), survivorship (Miles, 2004),
mating opportunities (Robson and Miles, 2000), and fecun-
dity (Stahlschmidt et al., 2013).
Plethodontid salamanders as a model system.—Plethodontid
salamanders are one of the most abundant vertebrates in
forests of the eastern United States (Semlitsch et al., 2014).
This group of salamanders has a critical role in regulating
invertebrate detritivores (Walton, 2005, 2013; Walton et al.,
2006). They also function as energy capacitors through
storage of nutrients in forest ecosystems (Hickerson et al.,
2012; Semlitsch et al., 2014). Thus, plethodontid salaman-
ders serve as a key indicators of forest health because of their
sensitivity to habitat disturbances and ease of sampling
(Welsh and Droege, 2001).
The habitat requirements for plethodontid salamanders are
structured by several physiological constraints as illustrated
by Huey (1991; Fig. 1). First, a primary physiological feature
of Plethodon salamanders is their reliance on cutaneous
respiration. Consequently, individuals require cool and moist
habitat to persist (Spotila, 1972; Gatz et al., 1975; Wells,
2007). The second attribute of Plethodon salamanders is their
nocturnal activity period, which limits their chance of
1
Ohio University, Department of Biological Sciences, 107 Irvine Hall, Athens, Ohio 45701; Email: (VRF) vfarallo@gmail.com. Send reprint
requests to VRF.
Submitted: 4 December 2014. Accepted: 11 June 2015. Associate Editor: R. M. Bonett.
Ó2016 by the American Society of Ichthyologists and Herpetologists DOI: 10.1643/CE-14-219 Published online: 17 March 2016
Copeia 104, No. 1, 2016, 67–77
overheating, but also means that any active thermoregula-
tion they utilize must involve exploiting microhabitats
which have been heated at different rates during the day.
Most plethodontids are imprecise thermoregulators (Feder,
1982), but there is evidence that species may select
temperatures through habitat selection. Broadly, Plethodon
salamanders can move vertically in the soil through the use
of burrows and natural crevices created by rocky substrates to
find appropriate moisture and temperature (Diefenbacher,
2007; Caceres-Charneco and Ransom, 2010; Drake et al.,
2012). This vertical movement allows them to persist when
surface conditions are not ideal, including using below
ground refugia during cold winter months (Grizzell, 1949;
Caldwell and Jones, 1973; Caldwell, 1975; Hoff, 1977) as well
as when surface conditions are too dry or warm during the
rest of the year (Stebbins, 1954; Houck, 1977; Camp, 1988).
The requirement for thermally appropriate microhabitats is
especially important in light of the planet’s changing
climate. There is predicted to be substantial loss of suitable
habitat as a result of climate change (Milanovich et al., 2010).
Salamanders are especially vulnerable to habitat changes.
Their physiological requirements for cool and moist habitat
may drive dispersal to higher elevations until suitable habitat
is no longer available. Therefore, climate change is expected
to have detrimental impacts on these high elevation species
(Raxworthy et al., 2008; Xu et al., 2009). Species range shifts
have already occurred as a result of climate change (Walther
et al., 2002; Parmesan, 2006). Some salamander species have
shown a decline in body size, presumably in response to
climate change (Caruso et al., 2014), which could impact the
habitat they are able to utilize or cause changes in
interspecific competion. Additionally, similar to the potential
impacts of climate change, other disturbances that alter the
forest floor habitat have been shown to be detrimental to
salamander populations (Gibbs, 1998; Hocking et al., 2013).
One advantage that amphibians, as well as other small
ectotherms, have is that they are capable of utilizing
microhabitat refugia, which may help mitigate the effects
of climate change (Seebacher and Alford, 2002; Shoo et al.,
2011). In addition to temperature, amphibians also need to
regulate moisture, making microhabitats especially critical
for maintaining physiological performance (Spotila, 1972).
Microhabitat refugia include leaf litter and cover objects,
such as rocks, woody debris, or other substrates that buffer
against warm, dry, or both habitats (Jaeger, 1972; Grover,
1998; McKenny et al., 2006; Patrick et al., 2006). Time since
last rain has been shown to improve the quality of
microhabitats (e.g., increasing moisture on the forest floor)
and increase surface activity of P. serratus (O’Donnell et al.,
2014). Quantifying how microhabitats are affected by
regional scale climate variables as well as the conditions in
which salamanders exploit microhabitat refugia will facilitate
predictions regarding potential changes to species distribu-
tion or ecology.
Plethodontid salamanders are characterized by having
small home ranges; however, individuals within a population
may utilize a diverse array of microhabitats within a small
area, including arboreal substrates (Jaeger, 1978; Trauth et al.,
2000; Regester and Samoray, 2002; Niemiller, 2005), various
types of cover objects (Jaeger et al., 1982; Mathis, 1990), and
burrows below the forest floor (Diefenbacher, 2007; Caceres-
Charneco and Ransom, 2010; Drake et al., 2012). Therefore,
determining detectability is important when attempting to
assess the status of populations which will be further
enhanced by increasing our knowledge of microhabitat use
(Bailey et al., 2004a, 2004b, 2004c; Dodd and Dorazio, 2004;
MacKenzie et al., 2004). Previous studies have assessed the
habitat associations of widespread plethodontids (Gibbs,
1998; Hocking et al., 2013; Peterman et al., 2013). However,
we have scant information regarding specific ecological
requirements of many microendemic salamander species.
The absence of key data on habitat requirements complicates
our ability to assess population status and predict the
consequences of anthropogenic disturbance.
The primary goal of this study is to assess the microhabitat
use of two microendemic species whose natural history is
largely unknown: the Peaks of Otter Salamander (P. hubrichti)
and the Big Levels Salamander (P. sherando). We use these
data to compare with the closely related and widespread
congener, the Eastern Red-backed Salamander (P. cinereus).
The distribution of P. cinereus spans over 1.8 million km
2
(Fig.
2) and completely surrounds the range of both micro-
endemic species, but includes only a narrow area of sympatry
with both species (Highton, 2004; Kniowski and Reich-
enbach, 2009). Plethodon hubrichti is hypothesized to be the
sister taxon to P. nettingi (Highton et al., 2012), another
endemic Plethodon. However, P. hubrichti is also hypothesized
to be more closely related to P. cinereus than P. sherando,
whereas P. sherando is the sister taxon to P. serratus, the
Southern Red-backed Salamander (Bayer et al., 2012).
Interestingly, the range of P. sherando is completely surround-
ed by P. cinereus, while P. serratus is found over 370 km from P.
sherando. Both microendemic species have restricted ranges
of ~36 km
2
and ~49 km
2
for P. sherando and P. hubrichti,
respectively (Fig. 2). The restricted ranges of these species and
their high elevation habitats make them vulnerable to
Fig. 1. The distribution of a pletho-
dontid salamander species is affected
by the habitat characteristics, such as
ambient temperature and hydric en-
vironments that optimize short-term
physiological performance. Variation
in these two categories can affect
population dynamics via their influ-
ence on key fitness traits, such as
growth, survivorship, and reproduc-
tion. Modified from Huey (1991).
68 Copeia 104, No. 1, 2016
population declines from climatic warming. Warmer and
drier environments at low elevations will force most
movement toward even higher elevation habitats. Further-
more, both of their ranges are encompassed by P. cinereus,
which means any expansion or change in the geographic
distribution of the microendemics as a consequence of
climate change may create a challenge for population
persistence through competition. For example, P. cinereus is
thought to have contributed to the decline of the Cheat
Mountain Salamander (P. nettingi) in the past 30 years as a
result of the former species exhibiting an upward shift in
elevation and increasing in abundance (Kroschel et al.,
2014). Character displacement also occurs in areas where
another species, P. hoffmani, is sympatric with P. cinereus,
indicating that competition occurs between small bodied
Plethodon (Jaeger et al., 2002). Despite the potential threats to
both species, little is known about either species’ ecology.
Kniowski and Reichenbach (2009) conducted a general
assessment of sympatric populations of P. hubrichti and P.
cinereus, while Mitchell et al. (1996) and Reichenbach and
Sattler (2007) showed that clear cutting of forests had a
negative effect on populations of P. h u b r i c h t i .Toour
knowledge, no studies have addressed the ecology of P.
sherando. Furthermore, no studies have assessed detailed
habitat use, such as soil moisture, relative humidity, and
temperature of microhabitats for either of the microendemic
species. In order to assess the potential impacts of climate
change on species with highly restricted ranges, we need a
better understanding of how species utilize habitat at a
biologically realistic scale.
We test two hypotheses in this study. First, do the three
species exhibit a preference for habitat characteristics that
differs from the available habitat? Second, do the microhab-
itats used by the microendemic species overlap with the
preference exhibited by the widespread species, P. cinereus?
We predict that the widespread species, P. cinereus, should
exhibit less selectivity than either of the microendemics. This
prediction is based on the premise that P. cinereus is expected
to be a habitat generalist that exploits multiple types of
habitats. Furthermore, the microendemics are predicted to
have specialized habitat preferences and exhibit limited
overlap with that of P. cinereus. We also comment on the
role of microhabitats as potential refugia from climate
change. Finally, we suggest additional avenues of research
that would enhance our knowledge of these microendemic
plethodontids and enhance predictions regarding their
vulnerability to climate change.
MATERIALS AND METHODS
Field sites.—We measured microhabitat variables at 39
localities throughout the Appalachian Mountains and foot-
hills within the range of Plethodon cinereus (35), P. sherando
(2), and P. hubrichti (2) between 8 June 2012 and 18 October
2014. Each locality consisted of an area of 1 km
2
. At each
locality we searched sites for salamanders using time
constraint surveys of 1 person hour each and haphazard
searching. Surveys were conducted during the day when
salamanders are under cover and in the evening when they
are active. We completed a total of 99 surveys, with each
locality being surveyed between 1–5 times. Field sites for
Plethodon cinereus were located between 39.68and 36.08
latitude and represented the southern half of the species
range. This latitudinal band is comparable with the distribu-
tion of the two microendemic species from Virginia.
Microhabitat measurements.—We collected microhabitat data
at the capture location of each salamander. We also obtained
habitat data at ten randomly chosen points within the search
area. The random points were selected to provide informa-
tion on the availability of each microhabitat category
included in our study. All random points were found by
using a random number generator to determine a compass
bearing and then walking ten meters in that direction. In
addition to the systematic collection of random points, we
also included points ten meters in a random direction from
presence points and also under cover objects within 1 m
2
areas around presence points where salamanders were found.
Each random absence point represents a location that did not
have a salamander present during our survey. We do not
Fig. 2. Distributions of Plethodon
cinereus,P. sherando, and P. hubrich-
ti taken from IUCN Redlist (www.
iucnredlist.org). The inset map in the
top left corner contains the range of P.
cinereus and also denotes with a
black rectangle the extent of the main
map within the US.
Farallo and Miles—Microhabitat of microendemics 69
mean to imply that no salamander ever occurs at our absence
points, but rather that a salamander is not present and
surface active under the current microhabitat conditions.
These sampling methods ensured that we located salaman-
ders in as many surface active microhabitat locations as
possible as well as thoroughly sampling microhabitats
available for them to potentially utilize. During surveys we
collected ecologically relevant environmental data for ple-
thodontid salamanders that rely on cutaneous respiration.
Air temperature (60.58C) and relative humidity (63%) were
both recorded 1 m from the ground using a Kestral 3500
weather meter and digital psychrometer. We used measure-
ments at 1 m because these are comparable to broad scale
climatic data (e.g., WorldClim). We recorded soil temperature
using either a ThermaPlus thermocouple meter or an infrared
thermometer (IRT) with a high sensitivity probe (60.58C;
Thermoworks Inc.). We measured the temperature of the
ground and substrate surface with an infrared thermometer
(60.68C; Thermoworks Inc.). We measured soil moisture
using a HydroSense II (63%; Campbell Scientific Inc.). Soil
moisture and temperature probes were all inserted at
approximately a 458angle. Our microhabitat sample consist-
ed of 152 presence and 839 absence points (991 total).
We also placed iButton temperature loggers (Model:
DS1922L, Embedded Data Systems) at various microhabitats
at a site in Perry County, Ohio within habitat of P. cinereus.
The loggers were placed in five locations, 50 cm above
ground, ground level, and 10, 20, and 30 cm below ground
level from 14 July though 24 August 2012. We used these
data to quantify the temporal change in the thermal
environment.
Statistical analyses.—We classified each site into one of eight
categories. The first three categories were the capture
locations for each of the focal species, another three
categories included the random points within the range of
each of the focal species, and the final two categories
consisted of random points within the range of P. cinereus
but located within 10 km of the range of P. sherando or P.
hubrichti.
In order to visualize differences in habitat among these
categories, we utilized non-metric multidimensional scaling
and plotted the 95% confidence ellipses. We used a
Generalized Linear Mixed Models (GLMM) from the R
package lme4 (Bates et al., 2014) with site treated as random
factor and the habitat characteristics as predictor variables to
determine if each species utilized the microhabitat variables
different from what was available. We also compared the
parameter estimates to infer whether each species used
similar habitat variables. Prior to running the GLMM, we
screened the data for evidence of multicollinearity by
examining the pairwise correlations among all variables.
None of the correlations exceeded 0.70, suggesting multi-
collinearity is not likely to affect the results of the GLMM. We
used the function ‘‘dredge’’ from the package MuMIn
(Barto ´
n, 2013) to compare all possible subset models out of
the possible models using a saturated model as the initial
model. The ‘‘dredge’’ function uses AICc scores to select the
best reduced model from the original saturated model. The
marginal R
2GLMM
was also calculated for each model using a
modified method of Nakagawa and Schielzeth (2013; see
Johnson, 2014) using the best supported model for each
species. If there are significant differences in habitat use for
specific microhabitat variables at presence sites compared to
absence sites, the marginal R
2
provides an indication of the
microhabitat variables selected by each species. Comparison
of significant microhabitat variables for each species assists in
determining the potential mechanisms for the absence of
overlap between these microendemic species and the
widespread P. cinereus. All statistical analyses were conducted
using the program R (ver. 2.15; R Core Team, 2012).
RESULTS
Variation in microhabitat traits.—Analysis of the microhabitat
characteristics by the NMDS revealed substantial variation
across all groups. The first axis described a soil temperature
and soil moisture gradient. Points on the positive pole
consisted of sites with high soil temperatures and low soil
moisture (Table 1); whereas, points positioned on the
positive end of the second axis have high above ground
relative humidity and points towards the negative pole had
high values for air temperature (1 m above ground) and
below ground soil temperatures (Table 1). The first axis
separated P. sherando from P. cinereus and P. hubrichti (Fig. 3),
which suggests the former species tolerates warmer and drier
soil surfaces. The second axis positioned P. hubrichti and P.
Table 1. The correlation of environmental variables to the two NMDS
axes.
NMDS 1 NMDS 2
Air temperature 0.328 0.556
Soil temperature 0.546 0.336
Ground temperature 0.263 0.571
Soil moisture 0.926 0.045
Relative humidity 0.270 0.752
Fig. 3. Results from a non-metric multidimensional scaling analysis of
microhabitat data. The 95% confidence ellipses are presented for the
capture points for Plethodon cinereus,P. sherando, and P. hubrichti (3),
random points within the sample plot for each species (3), and random
points that are within 10 km of the range of P. sherando and P.
hubrichti (2). The first axis describes soil temperature and soil moisture.
Ellipses on the positive pole consisted of sites with high soil
temperatures and low soil moisture. The second axis describes relative
humidity as well as air and soil temperature. Ellipses positioned on the
positive end of the second axis have high relative humidity, and ellipses
towards the negative pole had high values for air temperature (1 m
above ground) and below ground soil temperatures.
70 Copeia 104, No. 1, 2016
sherando at the negative part of the habitat gradient and P.
cinereus in the positive zone. Thus, P. cinereus occupied sites
with higher relative humidity and lower temperatures. Both
P. hubrichti and P. sherando occurred in sites with warmer
temperatures. Examination of the 95% confidence ellipses
reveals that there is some overlap in the microhabitat
variables that characterize the capture sites for the three
salamanders. An analysis of distance (function ADONIS)
found significant differences between P. cinereus and P.
sherando (F
1,136
¼303.74, P¼0.024) but no difference
between P. cinereus and P. hubrichti (F
1,111
¼8.274, P¼0.75).
The widespread P. cinereus showed no overlap between the
ellipses for the capture and random points. In contrast, both
microendemic species exhibited variable amounts of overlap
between the capture and random points. The ellipses for P.
hubrichti almost completely overlapped, although the orien-
tation of the random and capture ellipses differed. The
random points for P. sherando overlapped with the capture
points but not as extensively as P. hubrichti. Note that the size
of the confidence ellipses for P. cinereus are smaller than
either microendemic species. There is also a striking
concordance between the confidence ellipses for P. cinereus
and P. sherando. This suggests that although the species
occupy environments with similar habitat structure, they are
selecting divergent microhabitat features. Finally, the two
categories that included random points at sites within the
range of P. cinereus but directly adjacent to random points of
P. sherando and P. hubrichti were positioned away from both
the capture points for the three salamander species and their
associated random points.
GLMM analysis.—We applied a generalized linear mixed
model to determine which habitat variables predict the
presence of each species. Because of the limited number of
capture points for P. hubrichti, we did not include the species
in the GLMM analysis. However, we present the patterns for
habitat use as a comparison with the remaining species. We
detected significant differences between the habitat charac-
teristics of capture sites and random points for both P.
cinereus and P. sherando (Table 2). The best model for P.
cinereus (marginal R
2GLMM
¼76%) included two significant
variables (ground temperature and relative humidity). The
best model for P. sherando (marginal R
2GLMM
¼41%) involved
three variables (air temperature, soil temperature, and ground
temperature). Plethodon cinereus was found at significantly
cooler ground temperature and lower relative humidity than
what was available (Fig. 4). Plethodon sherando was found at
areas with significantly higher air temperature and lower
ground and soil temperatures (Fig. 4). Although the GLMM
found no difference in soil moisture used by any of the
species compared to what was available, P. sherando was
found in areas on average with 2% higher soil moisture.
Temporal change of microhabitats.—The thermal characteris-
tics of below ground microhabitats exhibited remarkable
consistency in both mean values throughout the day (Fig.
5A) and over the entire period of deployment (Fig. 5B).
Moreover, the logger positioned 50 cm above ground had a
temperature range of 9.68C between the hourly minimum
and maximum temperatures over the course of an average
24-hour period, which was the highest value found among
all sites (Fig. 5A). Notably, the logger 30 cm below ground
only spanned 0.28C on average over a 24-hour period (Fig.
5A). When considering the temperatures experienced
throughout the entire deployment, the logger 10 cm below
ground only varied 8.58C with the logger at 30 cm below
ground staying within 5.08C throughout the 41 days (Fig.
5B). In contrast, the logger at ground level spanned 25.08C,
and the logger at 50 cm above ground had the greatest
temperature range of 29.68C (Fig. 5B).
DISCUSSION
We found Plethodon cinereus and P. sherando utilize signifi-
cantly different microhabitats than what is available,
indicating that, at least when they are at the surface, they
are seeking out specific habitats. In contrast, P. hubrichti
showed substantial overlap between the habitat characteris-
tics at the site of capture and the random points. All three
species exhibited variable amounts of overlap with each
other in the microhabitat space. Furthermore, different
microhabitat variables seemed to be important for each
species. Although we could not include P. hubrichti in a
GLMM analysis, the species does not appear to exploit
habitats that differ from the available habitat characteristics.
Plethodon hubrichti also appears to utilize different habitat
than P. cinereus based on our NMDS results; however, our
statistical analysis did not support this conclusion. Given the
low number of capture points for P. hubrichti, these results are
tentative and require additional sampling while potentially
including variables not included in this study, such as
vegetation or soil characteristics.
The distribution of P. sherando includes only a small area of
sympatry with P. cinereus (Highton, 2004). Our results suggest
that the species are utilizing different microhabitats. One
potential explanation for this pattern is that competition is
structuring the habitat differences. Many species of Plethodon
exhibit territoriality, often defending cover objects from
other conspecifics (Jaeger and Forester, 1993; Mathis et al.,
1995). However, some species exhibit territorial behaviors
Table 2. The results of Generalized Linear Mixed Models comparing the habitat variables that best predict the presence sites of Plethodon cinereus
and P. sherando. Parameter estimates and their standard error are presented. Values in bold indicates P,0.05; — indicates that a variable was not
included in the best model for that species.
Species
Plethodon cinereus Plethodon sherando
Parameter estimate Standard error Parameter estimate Standard error
Air temperature 0.067 0.046 1.904 2.255
Soil temperature — — 0.761 0.165
Ground temperature 0.381 0.059 0.968 0.206
Soil moisture ————
Relative humidity 0.047 0.008 ——
Farallo and Miles—Microhabitat of microendemics 71
towards heterospecifics which can result in one species
excluding the other from specific habitats (Jaeger, 1971;
Anthony et al., 1997; Griffis and Jaeger, 1998). Furthermore,
Jaeger et al. (2002) showed character displacement occurs in
areas of sympatry between P. cinereus and P. hoffmani.In
addition, the GLMM analyses revealed that the habitat traits
predicting the occurrence of both species differed. This
heterogeneity in microhabitat selection is also consistent
with morphological differences between the species. The
microendemic species P. sherando is morphologically distinct,
having a larger head and longer limbs (Highton, 2004). These
morphological features may enhance the ability of P.
sherando to access thermally and hydrically favorable micro-
habitats. Within the small range of P. sherando, there is a high
density of large rocky substrates that extend below ground
level (Farallo, pers. obs.). We have observed areas where P.
cinereus are found in soil dominated habitat, but in an area
immediately adjacent where rocky habitat is dominant, P.
sherando have been found (Farallo, pers. obs.). The use of
rocky substrates has been associated with long limbs in
Australian skinks (Goodman et al., 2008). Longer limbs may
allow P. sherando better access to preferred microhabitats
available in open pockets within rocky crevices below the
forest floor. However, limb length may entail a trade-off by
limiting access to preferred thermal microhabitats that are
dominated by soil and finer substrates. Davis and Pauly
(2011) observed larger heads in a group of Western Slimy
Salamanders (P. albagula) that routinely use subterranean
karst habitat when compared to populations that are more
likely to utilize terrestrial habitat. Plethodon sherando has a
larger head than P. cinereus which may have an unforeseen
benefit when utilizing these rocky underground habitats.
There may also be morphological traits that are plastic, such
as vertebrae number resulting in variable levels of elongation,
allowing populations to better exploit different habitat
conditions (Jockusch, 1997). Additional studies to quantify
the performance differences of P. s h e r a n d o when using
subterranean environments could determine the role of
limbs in habitat selection. Furthermore, limited data are
available for microhabitat temperatures and moisture levels
in below ground refugia.
A key question in biogeography and conservation biology
is what determines the heterogeneity in species distributions,
especially microendemic species. One potential explanation
for the limited range of P. sherando and P. hubrichti is that P.
cinereus typically outcompetes other small-bodied species of
Fig. 4. Comparison of microhabitat
variables for Plethodon cinereus,P.
sherando, and P. hubrichti at capture
sites (dark gray) and absence points
(light gray). Values are means6stan-
dard error.
72 Copeia 104, No. 1, 2016
Fig. 5. Temporal fluctuation in temperature recorded at five different microhabitats in Perry County, Ohio. (A) Diurnal variation in mean at each
microhabitat. (B) Seasonal variation in temperature between 14 July and 24 August 2012.
Farallo and Miles—Microhabitat of microendemics 73
Plethodon (Jaeger, 1970, 1972; Adams and Rohlf, 2000; Jaeger
et al., 2002; Kroschel et al., 2014). The ability of P. cinereus to
thrive in a broad array of forest habitats results in other
microendemic species being restricted to specific types of
habitat where they are able to gain a competitive advantage.
Conversely, in lab based behavioral trials, P. hubrichti is more
aggressive than P. cinereus (Arif et al., 2007), but it appears
that P. hubrichti is restricted by abiotic factors (Arif et al.,
2007) which results in their small range despite being
competitively superior to P. cinereus. However, these results
do not take into account microhabitat use as well as
behavioral interactions that may be affected by differences
in microhabitat. The laboratory behavioral trials were
performed under standardized conditions, and they only
included climatic data as abiotic factors. These results
certainly provide possibilities for the restricted range of P.
hubrichti and their interactions with P. cinereus; however,
understanding how P. hubrichti utilizes microhabitat and
consequently how they interact with P. cinereus when in
those specific microhabitats will most likely provide a more
complete understanding of their restricted range.
Our results partially support this pattern of habitat
differentiation. The position of the 95% confidence ellipses
for both P. sherando and P. hubrichti are significantly shifted
away from P. cinereus. However, comparisons of the micro-
habitat characteristics between capture and random points
for P. hubrichti exhibited substantial overlap, suggesting the
species is not selective, at least given our limited data.
Plethodon sherando shows little overlap between occupied and
random points. The species tends to favor warmer habitats
that have cooler ground and soil temperatures. Interestingly,
the microhabitat features of the random points for P. cinereus
and P. sherando occupy similar sections of the microhabitat
space defined by the NMDS analysis. In contrast, P. sherando
inhabits forested environments that are similar to P. cinereus
but has different thermal requirements. Our results empha-
size the need to include behavioral and ecological traits to
enhance our ability to determine how changes to habitat will
affect species persistence.
The thermal data derived from the deployment of data-
loggers provide a key pattern. We deployed the dataloggers
during summer months when P. cinereus is not engaged in
surface activity at low elevations. However, the thermal data
demonstrate the consistency of below ground temperatures.
Salamanders are able to seek refuge in microhabitats that
provide a nearly constant temperature by venturing only 10
cm below ground. It is also very likely that a similar effect
would be seen under leaf litter. Although this was not
measured by our data loggers, we have seen striking
differences in temperatures above and below leaf litter,
including a 34.28C difference at a field site in West Virginia
where salamanders were present under leaf litter (54.28C
above leaf litter and 20.08C below leaf litter; unpubl.).
Another factor not measured by our data loggers is relative
humidity within underground retreats which may provide
pockets of higher humidity levels.
Our results revealed critical gaps in information that must
be addressed in order to mitigate potential impacts of climate
change on salamander populations. Given the numerous
microendemic species whose distributions are limited to high
elevation habitats, the potential for dispersal to thermally
favorable microclimates is unlikely. Determination of the
exploitation of below ground microhabitats by salamanders
enhances our ability to design and implement new habitat
studies. If salamanders are able to thrive with minimal or no
surface activity, including sufficient food acquisition and
mating success, then habitat studies need to shift to include
their below ground habitats. However, if the ability of
salamanders to feed and mate requires surface activity, then
research should focus on the impacts of climate change on
these surface habitats even if they are only used for short
periods of time.
ACKNOWLEDGMENTS
We thank the George Washington and Jefferson, Wayne,
Pisgah, Monongahela, and Cherokee National Forests, Great
Smoky Mountains (GRSM-2012-SCI-1098) and Blue Ridge
Parkway National Parks (BLRI-2-12-SCI-0024), and the states
of Ohio (Wild Animal Permit 17-03), West Virginia (Scientific
Collecting Permit 2014.007), North Carolina (Wildlife
Collections License 14-SC00604), Tennessee (Scientific Col-
lection Permit 3696), and Virginia (Scientific Collection
Permit 050025) for permission to access field sites. We also
thank C. Wheeler, W. Ternes, S. Lora, M. Etheridge, K.
Warack, and R. Wier for assistance in the field. Funding for
this study was provided in part by the Society for the Study
of Evolution, The Explorers Club, American Philosophical
Society, and the Ohio University Student Enhancement
Award. Field work was made possible by the Ohio University
Graduate College Fellowship and the Ohio Center for
Ecology and Evolutionary Studies Fellowship. All work was
approved by the Ohio University Animal Care and Use
Committee (13-L-012). DBM was supported by NSF grant
1241848.
LITERATURE CITED
Adams, D. C., and F. J. Rohlf. 2000. Ecological character
displacement in Plethodon: biomechanical differences
found from a geometric morphometric study. Proceedings
of the National Academy of Sciences of the United States of
America 97:4106–4111.
Anthony, C. D., J. A. Wicknick, and R. G. Jaeger. 1997.
Social interactions in two sympatric salamanders: effec-
tiveness of a highly aggressive strategy. Behaviour 134:71–
88.
Arif, S., D. C. Adams, and J. A. Wicknick. 2007. Bioclimatic
modelling, morphology, and behaviour reveal alternative
mechanisms regulating the distributions of two parapatric
salamander species. Evolutionary Ecology Research 9:843–
854.
Bailey, L. L., T. R. Simons, and K. H. Pollock. 2004a.
Estimating detection probability parameters for Plethodon
salamanders using the robust capture-recapture design.
Journal of Wildlife Management 68:1–13.
Bailey, L. L., T. R. Simons, and K. H. Pollock. 2004b.
Estimating site occupancy and species detection probabil-
ity parameters for terrestrial salamanders. Ecological Ap-
plications 14:692–702.
Bailey, L. L., T. R. Simons, and K. H. Pollock. 2004c. Spatial
and temporal variation in detection probability of Pletho-
don salamanders using the robust capture-recapture design.
Journal of Wildlife Management 68:14–24.
Barto ´
n, K. 2013. Package ‘MuMIn’. http://cran.r-project.org/
web/packages/MuMIn/index.html
Bates, D., M. Maechler, B. Bolker, and S. Walker. 2014.
lme4: linear mixed-effects models using Eigen and S4. R
package version 1.1-7. http://cran.r-project.org/package¼
lme4
74 Copeia 104, No. 1, 2016
Bayer, C. S. O., A. M. Sackman, K. Bezold, P. R. Cabe, and
D. M. Marsh. 2012. Conservation genetics of an endemic
mountaintop salamander with an extremely limited range.
Conservation Genetics 13:443–454.
Brown, J. H. 1984. On the relationship between abundance
and distribution of species. The American Naturalist 124:
255–279.
Buckley, L. B., M. C. Urban, M. J. Angilletta, L. G. Crozier,
L. J. Rissler, and M. W. Sears. 2010. Can mechanism
inform species’ distribution models? Ecology Letters 13:
1041–1054.
Caceres-Charneco, R. I., and T. S. Ransom. 2010. The
influence of habitat provisioning: use of earthworm
burrows by the terrestrial salamander, Plethodon cinereus.
Population Ecology 52:517–526.
Caldwell, R. S. 1975. Observations on the winter activity of
the red-backed salamander, Plethodon cinereus, in Indiana.
Herpetologica 31:21–22.
Caldwell, R. S., and G. S. Jones. 1973. Winter congregations
of Plethodon cinereus in ant mounds, with notes on their
food habits. American Midland Naturalist 90:482–485.
Camp, C. D. 1988. Aspects of the life history of the Southern
Red-back Salamander Plethodon serratus Grobman in the
Southeast United States. American Midland Naturalist 119:
93–100.
Caruso, N. M., M. W. Sears, D. C. Adams, and K. R. Lips.
2014. Widespread rapid reductions in body size of adult
salamanders in response to climate change. Global Change
Biology 20:1751–1759.
Davis, D. R., and G. B. Pauly. 2011. Morphological variation
among populations of the Western Slimy Salamander on
the Edwards Plateau of Central Texas. Copeia 2011:103–
112.
Davis, M. B., and R. G. Shaw. 2001. Range shifts and
adaptive responses to Quaternary climate change. Science
292:673–679.
Diefenbacher, E. H. 2007. Plethodon glutinosus (Slimy
Salamander). Burrowing behavior. Herpetological Review
38:67–68.
Dodd, C. K., and R. M. Dorazio. 2004. Using counts to
simultaneously estimate abundance and detection proba-
bilities in a salamander community. Herpetologica 60:468–
478.
Drake, D. L., K. O’Donnell, and B. Ousterhout. 2012.
Plethodon serratus (southern red-backed salamander). Cica-
da burrow use. Herpetological Review 43:318–319.
Feder, M. E. 1982. Thermal ecology of Neotropical lungless
salamanders (Amphibia: Plethodontidae): environmental
temperatures and behavioral responses. Ecology 63:1665–
1674.
Fitzpatrick, M. C., N. J. Gotelli, and A. M. Ellison. 2013.
MaxEnt versus MaxLike: empirical comparisons with ant
species distributions. Ecosphere 4:art55.
Gatz, R. N., E. C. Crawford, and J. Piiper. 1975. Kinetics of
inert-gas equilibration in an exclusively skin-breathing
salamander, Desmognathus fuscus. Respiration Physiology
24:15–29.
Gibbs, J. P. 1998. Distribution of woodland amphibians
along a forest fragmentation gradient. Landscape Ecology
13:263–268.
Goodman, B. A., D. B. Miles, and L. Schwarzkopf. 2008.
Life on the rocks: habitat use drives morphological and
performance evolution in lizards. Ecology 89:3462–3471.
Griffis, M. R., and R. G. Jaeger. 1998. Competition leads to
an extinction-prone species of salamander: interspecific
territoriality in a metapopulation. Ecology 79:2494–2502.
Grizzell, R. A. 1949. The hibernation site of three snakes and
a salamander. Copeia 1949:231–232.
Grover, M. C. 1998. Influence of cover and moisture on
abundances of the terrestrial salamanders Plethodon cinereus
and Plethodon glutinosus. Journal of Herpetology 32:489–
497.
Hickerson, C. M., C. D. Anthony, and M. B. Walton. 2012.
Interactions among forest-floor guild members in structur-
ally simple microhabitats. American Midland Naturalist
168:30–42.
Highton, R. 2004. A new species of woodland salamander of
the Plethodon cinereus group from the Blue Ridge Moun-
tains of Virginia. Jefersoniana 14:1–22.
Highton, R., A. P. Hastings, C. Palmer, R. Watts, C. A. Hass,
M. Culver, and S. J. Arnold. 2012. Concurrent speciation
in the eastern woodland salamanders (genus Plethodon):
DNA sequences of the complete albumin nuclear and
partial mitochondrial 12s genes. Molecular Phylogenetics
and Evolution 63:278–290.
Hocking, D. J., G. M. Connette, C. A. Conner, B. R.
Scheffers, S. E. Pittman, W. E. Peterman, and R. D.
Semlitsch. 2013. Effects of experimental forest manage-
ment on a terrestrial, woodland salamander in Missouri.
Forest Ecology and Management 287:32–39.
Hoff, J. G. 1977. A Massachusetts hibernation site of the red-
backed salamander, Plethodon cinereus. Herpetological Re-
view 8:33.
Houck, L. D. 1977. Life history patterns and reproductive
biology of neotropical salamanders, p. 43–72. In: The
Reproductive Biology of Amphibians. D. H. Taylora and S.
I. Guttman (eds.). Plenum Press, New York.
Huey, R. B. 1991. Physiological consequences of habitat
selection. American Naturalist 137:S91–S115.
Jaeger, R. G. 1970. Potential extinction through competition
between two species of terrestrial salamanders. Evolution
24:632–642.
Jaeger, R. G. 1971. Competitive exclusion as a factor
influencing distributions of two species of terrestrial
salamanders. Ecology 52:632–637.
Jaeger, R. G. 1972. Food as a limited resource in competition
between two species of terrestrial salamanders. Ecology 53:
535–546.
Jaeger, R. G. 1978. Plant climbing by salamanders: periodic
availability of plant-dwelling prey. Copeia 1978:686–691.
Jaeger, R. G., and D. C. Forester. 1993. Social behavior of
plethodontid salamanders. Herpetologica 49:163–175.
Jaeger,R.G.,D.Kalvarsky,andN.Shimizu.1982.
Territorial behavior of the red-backed salamander: expul-
sion of intruders. Animal Behaviour 30:490–496.
Jaeger, R. G., E. D. Prosen, and D. C. Adams. 2002.
Character displacement and aggression in two species of
terrestrial salamanders. Copeia 2002:391–401.
Jockusch, E. L. 1997. Geographic variation and phenotypic
plasticity of number of trunk vertebrae in slender sala-
manders, Batrachoseps (Caudata: Plethodontidae). Evolu-
tion 51:1966–1982.
Johnson, P. C. D. 2014. Extension of Nakagawa & Schiel-
zeth’s R
2
GLMM to random slopes models. Methods in
Ecology and Evolution 5:944–946.
Kearney, M., and W. P. Porter. 2004. Mapping the
fundamental niche: physiology, climate, and the distribu-
tion of a nocturnal lizard. Ecology 85:3119–3131.
Farallo and Miles—Microhabitat of microendemics 75
Kearney, M., and W. Porter. 2009. Mechanistic niche
modelling: combining physiological and spatial data to
predict species’ ranges. Ecology Letters 12:334–350.
Kniowski, A., and N. Reichenbach. 2009. The ecology of
the peaks of otter salamander (Plethodon hubrichti)in
sympatry with the eastern red-backed salamander (Pletho-
don cinereus). Herpetological Conservation and Biology 4:
285–294.
Kroschel, W. A., W. B. Sutton, C. J. W. Mcclure, and T. K.
Pauley. 2014. Decline of the Cheat Mountain Salamander
over a 32-year period and the potential influence of
competition from a sympatric species. Journal of Herpe-
tology 48:415–422.
MacKenzie, D. I., L. L. Bailey, and J. D. Nichols. 2004.
Investigating species co-occurrence patterns when species
are detected imperfectly. Journal of Animal Ecology 73:
546–555.
Mathis, A. 1990. Territoriality in a terrestrial salamander: the
influence of resource quality and body size. Behaviour 112:
162–175.
Mathis, A., R. G. Jaeger, W. H. Keen, P. K. Ducey, S. C.
Walls, and B. W. Buchanan. 1995. Aggression and
territoriality by salamanders and a comparison with the
territorial behavior of frogs, p. 633–676. In: Amphibian
Biology, Vol. 2: Social Behaviour. H. Heatwole and B. K.
Sullivan (eds.). Surrey Beatty and Sons, Chipping Norton,
New South Wales, Australia.
McCarty, J. P. 2001. Ecological consequences of recent
climate change. Conservation Biology 15:320–331.
McKenny, H. C., W. S. Keeton, and T. M. Donovan. 2006.
Effects of structural complexity enhancement on eastern
red-backed salamander (Plethodon cinereus) populations in
northern hardwood forests. Forest Ecology and Manage-
ment 230:186–196.
Milanovich, J. R., W. E. Peterman, N. P. Nibbelink, and J.
C. Maerz. 2010. Projected loss of a salamander diversity
hotspot as a consequence of projected global climate
change. PLOS ONE 5:e12189.
Miles, D. B. 2004. The race goes to the swift: fitness
consequences of variation in sprint performance in
juvenile lizards. Evolutionary Ecology Research 6:63–75.
Mitchell, C., J. A. Wicknick, and C. D. Anthony. 1996.
Effects of timber harvesting practices on peaks of otter
salamander (Plethodon hubrichti) populations. Amphibian
and Reptile Conservation 1:15–19.
Nakagawa, S., and H. Schielzeth. 2013. A general and
simple method for obtaining R
2
from generalized linear
mixed-effects models. Methods in Ecology and Evolution
4:133–142.
Niemiller, M. L. 2005. Pseudotriton ruber ruber (Northern
red salamander). Tree climbing. Herpetological Review 36:
52.
O’Donnell, K. M., F. R. Thompson, and R. D. Semlitsch.
2014. Predicting variation in microhabitat utilization of
terrestrial salamanders. Herpetologica 70:259–265.
Parmesan, C. 2006. Ecological and evolutionary responses to
recent climate change. Annual Review of Ecology Evolu-
tion and Systematics 37:637–669.
Patrick, D. A., M. L. Hunter, Jr., and A. J. K. Calhoun. 2006.
Effects of experimental forestry treatments on a Maine
amphibian community. Forest Ecology and Management
234:323–332.
Peterman, W. E., J. L. Locke, and R. D. Semlitsch. 2013.
Spatial and temporal patterns of water loss in heteroge-
neous landscapes: using plaster models as amphibian
analogues. Canadian Journal of Zoology 91:135–140.
Preest,M.R.,andF.H.Pough.1989. Interaction of
temperature and hydration on locomotion of toads.
Functional Ecology 3:693–700.
R Core Team. 2012. R: a language and environment for
statistical computing. R Foundation for Statistical Com-
puting, Vienna, Austria. https://www.R-project.org
Raxworthy, C. J., R. G. Pearson, N. Rabibisoa, A. M.
Rakotondrazafy, J.-B. Ramanamanjato, A. P. Raselima-
nana, S. Wu, R. A. Nussbaum, and D. A. Stone. 2008.
Extinction vulnerability of tropical montane endemism
from warming and upslope displacement: a preliminary
appraisal for the highest massif in Madagascar. Global
Change Biology 14:1703–1720.
Regester, K. J., and S. T. Samoray. 2002. Plethodon glutinosus
(slimy salamander). Tree climbing. Herpetological Review
33:45.
Reichenbach, N., and P. Sattler. 2007. Effects of timbering
on Plethodon hubrichti over twelve years. Journal of
Herpetology 41:622–629.
Robson, M. A., and D. B. Miles. 2000. Locomotor perfor-
mance and dominance in male Tree Lizards, Urosaurus
ornatus. Functional Ecology 14:338–344.
Rosenzweig, M. L. 1995. Species Diversity in Space and
Time. Cambridge University Press, Cambridge, U.K.
Seebacher, F., and R. A. Alford. 2002. Shelter microhabitats
determine body temperature and dehydration rates of a
terrestrial amphibian (Bufo marinus). Journal of Herpetol-
ogy 36:69–75.
Semlitsch, R. D., K. M. O’Donnell, and F. R. Thompson.
2014. Abundance, biomass production, nutrient content,
and the possible role of terrestrial salamanders in Missouri
Ozark forest ecosystems. Canadian Journal of Zoology 92:
997–1004.
Shoo, L. P., D. H. Olson, S. K. Mcmenamin, K. A. Murray,
M. Van Sluys, M. A. Donnelly, D. Stratford, J. Terhivuo,
A. Merino-Viteri, S. M. Herbert, P. J. Bishop, P. S. Corn, L.
Dovey, R. A. Griffiths, K. Lowe, M. Mahony, H.
Mccallum, J. D. Shuker, C. Simpkins, L. F. Skerratt, S.
E. Williams, and J.-M. Hero. 2011. Engineering a future
for amphibians under climate change. Journal of Applied
Ecology 48:487–492.
Sinervo, B. 1990. Evolution of thermal physiology and
growth rate between populations of the western fence
lizard Sceloporus occidentalis. Oecologia 83:228–237.
Spotila, J. R. 1972. Role of temperature and water in the
ecology of lungless salamanders. Ecological Monographs
42:95–125.
Stahlschmidt, Z. R., O. Lourdais, S. Lorioux, M. W. Butler,
J. R. Davis, K. Salin, Y. Voituron, and D. F. Denardo.
2013. Morphological and physiological changes during
reproduction and their relationships to reproductive
performance in a capital breeder. Physiological Biochem-
istry and Zoology 86:398–409.
Stebbins, R. C. 1954. Natural history of the salamanders of
the plethodontid genus Ensatina. University of California
Publications in Zoology 54:47–124.
Titon, B., Jr., C. A. Navas, J. Jim, and F. R. Gomes. 2010.
Water balance and locomotor performance in three species
of neotropical toads that differ in geographical distribu-
tion. Comparative Biochemistry and Physiology Part A
Molecular & Integrative Physiology 156:129–135.
Trauth, S. E., M. L. Mccallum, B. J. Ball, and V. E. Hoffman.
2000. Caudata: Plethodon caddoensis (Caddo Mountain
76 Copeia 104, No. 1, 2016
Salamander) and Plethodon serratus (Southern Redback
Salamander). Nocturnal climbing activity. Herpetological
Review 31:232–233.
Walther, G.-R., E. Post, P. Convey, A. Menzel, C. Parmesan,
T. J. C. Beebee, J.-M. Fromentin, O. Hoegh-Guldberg,
and F. Bairlein. 2002. Ecological responses to recent
climate change. Nature 416:389–395.
Walton, B. M. 2005. Salamanders in forest-floor food webs:
environmental heterogeneity affects the strength of top-
down effects. Pedobiologia 49:381–393.
Walton, B. M. 2013. Top-down regulation of litter inverte-
brates by a terrestrial salamander. Herpetologica 69:127–
146.
Walton, B. M., D. Tsatiris, and M. Rivera-Sostre. 2006.
Salamanders in forest-floor food webs: invertebrate species
composition influences top-down effects. Pedobiologia 50:
313–321.
Wells, K. D. 2007. The Ecology and Behavior of Amphibians.
University of Chicago Press, Chicago.
Welsh, H. H., and S. Droege. 2001. A case for using
plethodontid salamanders for monitoring biodiversity
and ecosystem integrity of North American forests.
Conservation Biology 15:558–569.
Werner, E. E., C. J. Davis, D. K. Skelly, R. A. Relyea, M. F.
Benard, and S. J. Mccauley. 2014. Cross-scale interactions
and the distribution-abundance relationship. PLOS ONE 9:
e97387.
Xu, J., R. E. Grumbine, A. Shrestha, M. Eriksson, X. Yang,
Y. Wang, and A. Wilkes. 2009. The melting Himalayas:
cascading effects of climate change on water, biodiversity,
and livelihoods. Conservation Biology 23:520–530.
Farallo and Miles—Microhabitat of microendemics 77
