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Macroecological constraints of colour and size in North American dragonflies and their evolutionary implications

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Abstract

Recent compilations of large scale physiological data and progress in spatial statistics have led to a renewed interest in some of macroecologies most fundamental questions. Although the investigation of physiological characteristics (traits) among species has been subject to several studies, their geographic variation owing to ambient conditions remains still a topic of debate. Being less able to control their thermal budget actively, some ectotherms show characteristics that influence heat gain (absorption) and heat conservation. In this study surface colouration (skin reflectance) and body size of North American dragonflies, both traits of major functional significance, were investigated with regard to their spatial patterns, environmental determinants and phylogenetic structure. As the colouration of 1373 dragonfly assemblages (representing 153 species) in North America tend to be more dark towards regions with cold conditions/less solar irradiance, the predictions of thermal melanism hypothesis (TMH) could be confirmed. In contrast, average body size decreased towards cold/moist conditions. Furthermore, phylogenetic eigenvector regression revealed a significant difference in the degree of manifestation among long and recent term adaptations of colour and size. A strong correlation with phylogeny suggests that especially the thermal environment may have played a crucial role in the genetic constitution of recent North American dragonflies and thus their historic distribution. During approximately 300 million years of evolution, adjustments in these traits probably mediated the diversification of lighter-coloured ancestors and initially qualified them to colonize other then the subtropic conditions, in which odonates originate.
Macroecological constraints of colour and size
in North American dragonflies and their evolutionary implications
Stefan Pinkert
September 11, 2013
Abstract
Recent compilations of large scale physiological data and progress in spatial statistics have led to a renewed interest
in some of macroecologies most fundamental questions. Although the investigation of physiological characteristics
(traits) among species has been subject to several studies, their geographic variation owing to ambient conditions
remains still a topic of debate. Being less able to control their thermal budget actively, some ectotherms show
characteristics that influence heat gain (absorption) and heat conservation. In this study surface colouration (skin
reflectance) and body size of North American dragonflies, both traits of major functional significance, were in-
vestigated with regard to their spatial patterns, environmental determinants and phylogenetic structure. As the
colouration of 1373 dragonfly assemblages (representing 153 species) in North America tend to be more dark to-
wards regions with cold conditions/less solar irradiance, the predictions of thermal melanism hypothesis (TMH)
could be confirmed. In contrast, average body size decreased towards cold/moist conditions. Furthermore, phy-
logenetic eigenvector regression revealed a significant difference in the degree of manifestation among long and
recent term adaptations of colour and size. A strong correlation with phylogeny suggests that especially the thermal
environment may have played a crucial role in the genetic constitution of recent North American dragonflies and
thus their historic distribution. During approximately 300 million years of evolution, adjustments in these traits
probably mediated the diversification of lighter-coloured ancestors and initially qualified them to colonize other
then the subtropic conditions, in which odonates originate.
Introduction
To explain global patterns in species distribution,
macroecology in its most simplified perspective, fo-
cuses on the determination of environmental constraints
to which species are liable (Chown and Gaston 2008).
Within the last decades, this strategy is applied increas-
ingly to predict future species ranges for conservation
efforts and invasive species research (Beaumont et al.
2005;Ara´
ujo et al. 2005;Pearman et al. 2008;Carvalho
et al. 2010). However, the ways in which absolute tol-
erance limits determine the edges of species ranges are
still poorly understood (perhaps caused by difficulties in
data collection; Sexton et al. 2009). To shed light upon
the fundamental processes underlying these tolerance,
the physiological traits that influence species perfor-
mance and fitness frequently have attracted the interest
of ecologists (McVey 1984;Lawton 1999;Clusella-
Trullas et al. 2008). It is assumed that restricted by
environmental constraints habitat-binding will lead to
faunal assemblages in space with similar niche require-
ments (niche conservatism hypothesis; Desdevises et al.
2003;Fukami et al. 2005), which ultimately tend to be
manifested in life history traits and genetic constitu-
tion (Wiens and Graham 2005). Given enough genetic
variation, edge populations may even be able to adapt
to conditions beyond their original selection regime
(Antonovics 1976). Such trait adjustments (adaptations)
occur within all hierarchical levels and are considered
to be the most potent force for diversification (Ackerly
2004;Gienapp et al. 2008;Johnston and Bennett 2008).
Only few ”rules” exist in ecology describing such
general or large-scale, biogeographic pattern of animal
traits (Lawton 1999;Olalla-T´
arraga 2011). Most of
them focus on endotherms, but all of them indirectly
address energy allocation. Since size is a metric prin-
cipally relatively easy to measure, the volume to body
surface ratio is up to now by far the most recognized em-
pirical generalization in biogeography (Lawton 1999).
However, its tendency depends on the thermal manage-
ment strategy and behaviour of the investigated taxo-
nomic group (Shelomi 2012;Lawton 1999). Based on
1
common physical principles, the assumption that lower
cooling coefficients (larger bodies) are advantageous
in regions with lower temperatures (e.g. high altitudes
with strong winds) is obviously valid (Bergmann 1848;
Chown and Gaston 2010;Pincheira-Donoso 2010), but
de facto hundreds of studies focusing on ectotherm taxa
resulted in controversial signals (no/decrease/increase
in body size toward cold regions - ”Bergmann-like”
pattern; reviewed in Shelomi 2012). There is evidence
that body size is partially related to environmental con-
ditions, but especially intermediate sized insects seem
to be subject to different mechanisms of thermoregula-
tion (Sformo and Doak 2006;Meiri and Thomas 2007).
Recent studies concerning the role of consistent oc-
currence of darker individuals between closely related
species and its influence on the thermal budged in ec-
totherms (referred to as ”thermal melanism” (TMH);
Gates 1980), propose indeed a promising alternative
hypothesis. The latter basically states that in regions
with lower temperatures and less insolation, dark phe-
notypes of ectotherm species should benefit from en-
hanced absorption (of a wide spectrum) compared to
lighter-coloured species (Lusis 1961;Clusella-Trullas
et al. 2008), resulting in higher equilibrium tempera-
ture and heating rate (Samejima and Tsubaki 2010).
On the contrary, species inhabiting warmer climates
need enhanced skin reflectance to decrease heat load
and avoid overheating. Given the profound influence
of body temperature on most of the physiological pro-
cesses (Hochachka et al. 2001), heliotherm ectotherms
like dragonflies will benefit from enhanced metabolic
rate (Willmer 1991) and prolonged diurnal as well as
annual activity in terms of higher reproductive success
(fitness) (May 1977;Brakefield 1984;Huey and King-
solver 1989).
Although previous studies on the subject of vari-
ation in trait distribution support the essentials (Brake-
field 1984;Clusella-Trullas et al. 2008; Zeuss et al.
in prep.), both phylogenetic and geographic dimensions
are times too small and provide limited value to interpret
the general situation (Diniz-Filho et al. 2007). Latitudes
for example only approximate the conditions along a
cline and therefore drastically reduce the heterogeneity
of the observed pattern. To test for a general validity,
in this study a grid-based approach is applied, which
in contrast to interspecific (or midpoint) approaches al-
lows to retain the spatial nature in all its facets (Olalla-
Tarraga et al. 2010).
The North American continent forms a vast, rather
continuous landmass with primarily continental climate,
which gradually changes to subtropic conditions in the
south of the United States. Compared to other con-
tinents, relatively linear gradients of temperature and
humidity extend across enormous distances, with the
great ranges of the Rocky Mountains and the Sierra
Nevada in the west, adding another dimension. In con-
trast to Europe the mountain ranges are longitudinally
oriented and thereby allowed species to re-immigrate
easily after local extinction (Dumont et al. 2005;Heiser
and Schmitt 2010). The evolutionary implications of
these natural barriers are quite profoundly understood
and may provide subsequently further insights in possi-
ble phylogenetic mechanisms. As Olalla-T´
arraga et al.
(2006) compared the pattern of body size of these two
continents, already definite differences in the explana-
tory power of environmental variables where found.
Being similar in its approach and techniques, a study by
Zeuss et al. (in prep.) on European odonates enables us
to evaluate the results of their analysis as well between
continents.
Up to now only a few animal taxa are studied
in such detailed and broad spectrum to finally provide
a sufficient basis for challenging the thermal melanism
hypothesis on both empirical and theoretical grounds. In
this regard, Odonata provide some very suitable biolog-
ical advantages. The order Odonata, commonly known
as dragonflies (Anisoptera and Epiophlebiidae) and
damselflies (Zygoptera), currently includes more than
5700 species (Kalkman et al. 2008). Thanks to their bril-
liant, colourful appearance dragonflies enjoy worldwide
popularity among avocational entomologists and scien-
tists (Lemelin 2007). As one result we are rather aware
of their diversity and functional importance in aquatic
and terrestrial systems (e.g. mosquito agents; Jenk-
ins 1964 and predators of rice pests; Yasumatsu et al.
1975). Beside their role in pest management the linkage
to freshwater ecosystems is frequently used to indicate
threatened humid habitats, yet coincidentally dragon-
flies themselves are as well in the focus of conservation
efforts (Kalkman et al. 2008). Compared to other taxa,
they are easy to recognize and to differentiate so distri-
bution ranges are well known and documented (in some
cases even cumulative; see www.OdonataCentral.com).
Particularly in the Holarctic they were subject to several
ecological, behavioural, physiological, and evolutionary
studies (see Corbet 2004 and sources therein).
Probably originated in the tropics, odonates
now inhabit nearly all faunistic-kingdoms, from the
semideserts of Algeria to the Arctic regions of Alaska
(Donnelly 2004;Samraoui et al. 2010). In over 300 mil-
lion years of evolution (estimated by TimeTree; Hedges
et al. 2006) their primitive phenotype has been subject to
only minor obvious changes (compared to Protodonata,
an ancient sister group) and remained conserved even
when the super continent Pangea has divided and condi-
tions drastically have changed (May 1982). This fact is
important for two reasons: i) Species have to be similar-
shaped in order to compare their body size (otherwise
physics differ). ii) If the shape of a certain species
does not vary while the environmental conditions do,
2
other traits probably compensate in terms of thermal
adaptation. Thus Legendre and Legendre (1998) argue
that phylogenetic relationship has to be implemented,
as these autocorrelation structures represent an impor-
tant source of information rather than a source of error.
Consequently, I herein use phylogenetic eigenvector re-
gression to address the evolutionary implications more
specifically.
This in mind I aim to describe the geographic varia-
tion of body size as well as surface colouration and
examine their relation to ambient environmental and
geophysical conditions in North American dragonfly
assemblages. Further reasonable modifications, based
on phaenological properties of annual irradiance and
the phylogenetic structure of both traits, are applied to
increase the biological validity of these relations.
Material and Methods
ENVIRONMENTAL INFORMATION
Initially, a set of 19 biologically relevant climate
variables, derived from interpolated monthly tempera-
ture/precipitation values and one physical variable (Al-
titude), was downloaded from WorldClim.org (Hijmans
et al. 2005; accessed 12 March 2013). These bio-
climatic variables represent annual trends, seasonality,
and extreme or limiting environmental factors and can
be divided into two main categories. Eleven of them
are associated with the ambient temperature, namely:
annual mean temperature (AMT), mean diurnal range
(mean of monthly (max temp - min temp; MDR),
isothermality ((MDR/TAR) * 100); IT), temperature
annual range (MaxTWaM-MinTCM; TAR), tempera-
ture seasonality (standard deviation *100; TS), mean
temperature of wettest quarter (MTWeQ), mean tem-
perature of driest quarter (MTDQ), mean temperature
of warmest quarter (MTWaQ), mean temperature of
coldest quarter (MTCQ), max temperature of warmest
month (MaxTWaM), and min temperature of coldest
month (MinTCM). Eight variables are associated with
precipitation and humidity: annual precipitation (AP),
precipitation seasonality (Coefficient of Variation; PS),
precipitation of wettest quarter (PWeQ), precipitation
of driest quarter (PDQ), precipitation of warmest quar-
ter (PWaQ), precipitation of coldest quarter (PCQ), pre-
cipitation of wettest month (PWeM), and precipitation
of driest month (PDM). Using the Zonalstats Plugin
for QuantumGIS Version 1.8.0 (Quantum GIS Develop-
ment Team 2013), mean values of these current condi-
tion records (1950 to 2000) with a resolution of 2,5 arc-
minutes (major radius= 6378137 m at the equator and
semi-minor axis6 356 752.314 245 m; NIMA 2000)
were calculated for a polygon mask-layer, with a spatial
extent of S: 24, N: 72, W: -168, E: -52, containing 5567
square grid-cells each with an edge length of one degree
(EPSG:4326).
In addition to mean annual irradiance (Annual), the
variable ”mean irradiance of the emergence period” (Ir-
rad. ep.) was generated based on the mean monthly
horizontal irradiance (kWh m2d1;NASA/SSE 2006)
of the time of most active pre-emergence development,
between the spring equinox and the solstice (Wissinger
1988), extended by the following three months. These
six months are assumed to be a proxy for the main fly-
ing/mating period of most of the dragonflies species.
Increased diurnal activity during this time should di-
rectly result in enhanced reproductive success (Huey
and Kingsolver 1989).
OCCURRENCE INFORMATION
Occurrence records used in this analysis were kindly
provided by community members of OdonataCen-
tral.org. They assembled over 190.000 entries of primar-
ily the North American continent from several books,
projects, and private records. Due to the heterogene-
ity of sampling methods within this dataset it was nec-
essary to align the grid-based (half-degree) occurrence
data in the Canadian territories and the county-centroid
records in the United States. With several very small
counties in the eastern and some vast counties in the
western USA, private observations with explicit coor-
dinates became very important to retain the spatial cov-
erage. The same regular one-degree grid as previously
described was used to convert all relevant observations
into presence/absence information of this resolution.
This seamed to be the most circumspect variant to deal
with such an inconsistent resolution, although it overes-
timated Canadian occurrence data slightly and underes-
timated US-American. Because the number of species
available as drawings is very limited and Central Amer-
ican countries as well as damselflies were excluded,
records were reduced to about 49.000 entries. Further
computing was accomplished with R Version 2.15.1 (R
Development Core Team 2012). Importing and convert-
ing geographical data was done with package “rgdal”
(Revelle 2013). To adjust geographical coordinates of
the grid cell centroids I used package ”sp” (Pebesma
et al. 2013). Package ”ClassInt” (Bivand 2012) was
used to classify data into intervals for trait categories in
cartographic illustrations. Classification intervals were
based on quantiles (same number of grid cells in each
class).
TRAIT INFORMATION
To extract the characteristic colouration of the anal-
ysed species, lateral drawings of male individuals were
scanned within a 24 bit sRGB colour-space and a
resolution of 1200 dpi. If necessary trait informations
3
of subspecies were averaged to a representative value
for each species. 153 species of dragonflies from ”Drag-
onflies of North America” (Needham et al. 2000) were
extracted. Background, wings, and legs as well as an-
tenna were clipped manually by using the implemented
tools of Photoshop CS6. Based on these uncompressed
Portable Network Graphic files (PNG), 8bit grey-values
were calculated as the mean of the red, green, and blue
channel and averaged to one representative modulus for
the colour of each species on a scale from 0 (represent-
ing absolute black) to 255 (absolute white). The re-
quired functions are provided by the R Package EBIm-
age (Pau et al. 2012). In addition to surface coloura-
tion the lateral area of each individual was extracted by
automatically counting the pixels of their illustrations
and scaling them up to square centimetres. I used this
characteristic as a proxy for ”body size”, a direct func-
tion of heat gain (minimum body temperature for flight;
May 1976).
PRINCIPAL COMPONENT ANALYSIS
Although the selected environmental variables men-
tioned before are all by themselves informative, it is
very likely that most of them, especially within each
category, are intercorrelated. Therefore, a principal
component analysis was applied to evaluate the quan-
titative dependence of the variables (Hotelling 1933;
Abdi and Williams 2010) and to determine the most
explanatory constraints to which dragonfly species are
liable. Package ”psych” (Revelle 2013) was used to
display the pattern of similarity within each category
and create new orthogonal variables, called principal
components (loadings and spatial pattern attached in
Appendix 1). Reduced to a two-dimensional subspace
these vectors, corresponding to the largest eigenvalues
(>1), per definition have different directions and com-
prise the majority of the proportion of variance (Ther-
mal environment: PC1= 0.55, PC2= 0.32; Precipitation:
PC1= 0.70, PC2= 0.18) within all variables of this class
(Wold et al. 1987). Thus, they will contain the most use-
ful information (for the objective of this study) related
to the surface colouration and body size of each spatial
assemblage.
PHYLOGENETIC EIGENVECTOR REGRESSION
A PVR was used to evaluate the phylogenetic struc-
ture of both surface colouration and body size measured
across species. Because these traits were expected to
be partially collinear with phylogeny the total variance
of them was decoupled into a phylogenetic (P) and a
specific (S) component. Most commonly, collinearity
is intrinsic, meaning that collinear variables are differ-
ent manifestations of the same underlying, and in some
cases, immeasurable process (Dormann 2012). In this
case an adaptive significance of both traits in the evo-
lution of dragonflies was assumed. The P component
represents the predicted part based on ancestral rela-
tionships (long term), whereas the model residuals (S)
express the part of the variation that is unique and inde-
pendently distributed among species (recent ecological
adaptation; Diniz-Filho et al. 2011). Due to the lack of
a comprehensive phylogeny of North American dragon-
flies the works of Dumont et al. (2005), Misof et al.
(2001), Fleck et al. (2008), and taxonomic informa-
tion from catalogueoflife.org (Tol et al. 2013) were com-
piled. Based on this structure a pairwise distance ma-
trix with grey-value and body size as dependent variable
was calculated, respectively (composed tree attached in
Appendix 6). For the multiple linear regression model
five highly significant (p <0.01) phylogenetic eigen-
vectors, correlated with grey-value and four correlated
with body size were used, respectively, to finally calcu-
late the proportions of each component. Branch lengths
were estimated according to Grafen (1989) and calcula-
tions were performed in R with the package ”adephylo”
version 1.1-1 (Jombart and Dray 2010).
ASSEMBLAGE APPROACH
Following the approach for spatial analyses of body size
at the assemblage level (see Blackburn and Hawkins
2004;Diniz-Filho et al. 2007;Olalla-Tarraga et al. 2010;
Rodr´
ıguez et al. 2008; illustrated by Diniz-Filho et al.
2009), the variables ”P colouration”, ”S colouration”,
”P body size” and ”S body size” were generated by cal-
culating the arithmetic means of the P and S compo-
nents of each species represented in the grid-cell. Sub-
sequently, these mean values per grid were regressed
against environmental factors in a geographic context.
Results
GEOGRAPHIC VARIATION IN COLOUR AND SIZE
The mean grey-value and mean body size of 153 species
in North America were divided into an ancestral pre-
dicted (P) part, containing 32% (adj. r2) and 56%, re-
spectively, and a specific (S) part, containing 67% and
43%, respectively.
The signal for the ancestral predicted (P) compo-
nent of the geographical variation in surface coloura-
tion was most strongly positive correlated with the first
thermal component, which explained 29% (adj. r2), as
well as trained (monthly) and untrained (annual) irra-
diance, which explained 25% and 18% of the variance,
respectively (Tab. 1). I found no significant correla-
tion with the second precipitation component. The sec-
ond thermal and first precipitation component had minor
explanatory power but where still highly significant (p-
value <0.001) positive correlated with the P component
4
of colouration. Although altitude explained only about
2% (adj. r2) the analytical methods used in this work
were able to display its relationship to a rapid change in
environmental conditions quite detailed with respect to
the geographic context (Fig. 1). In contrast, the specific
(S) component was not correlated with the first thermal
component and slightly significant negative correlated
with the untrained (annual) irradiance. All other vari-
ables that describe thermal conditions (adj. r2of T PC
2: 2%), precipitation (P PC 1: 3%, P PC 2: 2%), and
geophysical ambient (Altitude: 2%, Irrad. ep.: 2%) had
only minor explanatory power but where still highly sig-
nificant (p-value <0.001) correlated with the variation
of the S component (Tab. 1). Darkest assemblages of
dragonfly species were found in the most poleward re-
gions and with an extend along the Great Lakes and the
mountain ranges, such as the Rocky Mountains as well
as the Sierra Nevada in the western and the Appalachi-
ans in the eastern United States (regions cooler in aver-
age; see loadings in Appendix 1). Meanwhile lighter-
coloured assemblages were found in southern regions
with a spatial extend along the Great Plains in the con-
tinental center as well as the Great Basin region in the
west. The mean specific (S) component of colouration
shows large negative deviations from ancestral predicted
surface colouration at the west coast and Florida as well
as in the western mountain ranges and the Appalachians
(Fig. 1).
The ancestral predicted (P) component of the
geographical variation in body size was highly signifi-
cant correlated with the first thermal component, which
explained 13% (adj. r2), the first precipitation com-
ponent, which explained 11%, and altitude which ex-
plained 11% of the variance observed in a univariate
least square regression (Tab. 1). The spatial distribution
of body size was not correlated with the second thermal
component and only slightly but highly significant cor-
related with the second precipitation component, which
explained 3% (adj. r2), as well as trained (monthly) and
untrained (annual) irradiance, which explained 4% and
9% of the variation, respectively. As compared, the spe-
cific (S) component was not correlated with the second
thermal component and the first precipitation compo-
nent. Most strongly positively correlated was the first
thermal component explaining 11% (adj. r2), altitude
explaining 10%, and trained as well as untrained irra-
diance explaining 14% and 14%, respectively (Tab. 1).
The second precipitation component (adj. r2of P PC
2: 2%) had only minor explanatory power but was still
highest significantly (p-value <0.001) negatively cor-
related with the variation in the specific (S) component
of body size. The faunal assemblages with smallest size
on average were found in subarctic and continental re-
gions and in the northern Rocky Mountains, while their
size tend to increase towards North America’s south-
east tracing the shapes of the Great Plains (Fig. 1). This
pattern tends to emerge more explicit when the ances-
tral predicted (P) component of mean body size is ob-
served. The variation in the specific (S) component de-
viates similar but less distinct, with the largest negative
deviations towards the north and east of North America
(Fig. 1).
Table 1: Results from univariate least-squares regressions between principal components of thermal environment
and precipitation, as well as altitude, monthly irradiance during the emergence period, annual irradiance, and
mean ancestral predicted (P) and specific (S) component, respectively. Components are based on mean surface
colouration (8bit grey-value; 0-255) and body size (lateral area; cm2) per regular one degree grid-cell of 153
dragonfly species in North America. Variable abbreviations and composition are described in Section Material and
Methods; Plots are attached in Appendix 2.
Colouration P component Body size P component
Intercept±SE Slope±SE R-squared P-value Intercept±SE Slope±SE R-squared P-value
T PC 1 103.27±0.07 1.557±0.066 0.29 <0.001 2.50±0.01 0.070±0.005 0.13 <0.001
T PC 2 103.27±0.08 0.325±0.077 0.01 <0.001 2.50±0.01 0.003±0.005 0 0.622
P PC 1 103.27±0.08 0.325±0.077 0.01 <0.001 2.50±0.01 0.067±0.005 0.11 <0.001
P PC 2 103.27±0.08 0.070±0.078 0 0.371 2.50±0.01 -0.034±0.005 0.03 <0.001
Altitude 103.70±0.11 -6.1e-04±1.3e-04 0.02 <0.001 2.57±0.01 -1.0e-04±8.3e-06 0.11 <0.001
Irrad. ep. 94.83±0.49 1.596±0.092 0.18 <0.001 2.24±0.04 0.050±0.007 0.04 <0.001
Annual 96.45±0.33 1.791±0.084 0.25 <0.001 2.22±0.02 0.072±0.006 0.09 <0.001
S component S component
T PC 1 -3.93±0.18 0.056±0.176 0 0.750 0.05±0.02 0.102±0.008 0.11 <0.001
T PC 2 -3.93±0.17 -0.824±0.175 0.02 <0.001 0.05±0.01 -0.018±0.008 0 0.026
P PC 1 -3.93±0.17 1.155±0.173 0.03 <0.001 0.05±0.01 -0.017±0.008 0 0.034
P PC 2 -3.93±0.17 -0.896±0.174 0.02 <0.001 0.05±0.01 0.044±0.008 0.02 <0.001
Altitude -2.99±0.25 -0.0015±0.0003 0.02 <0.001 -0.05±0.01 1.6e-04±1.3e-05 0.10 <0.001
Irrad. ep. 1.75±1.21 -1.073±0.227 0.02 <0.001 -0.74±0.05 0.148±0.010 0.14 <0.001
Annual -1.89±0.85 -0.533±0.218 0 0.015 -0.49±0.04 0.142±0.009 0.14 <0.001
5
under 99.7
99.7 100.8
100.8 101.3
101.3 101.7
101.7 102
102 102.4
102.4 102.9
102.9 103.1
103.1 103.3
103.3 104.1
104.1 104.7
104.7 105.5
105.5 106.5
106.5 107.6
over 107.6
80°W110°W140°W 25°N
45°N
65°N
Colouration P component
under 2.34
2.34 2.37
2.37 2.37
2.37 2.38
2.38 2.39
2.39 2.39
2.39 2.41
2.41 2.44
2.44 2.49
2.49 2.54
2.54 2.59
2.59 2.66
2.66 2.73
2.73 2.82
over 2.82
80°W110°W140°W 25°N
45°N
65°N
Body size P component
under 13.8
13.8 10.1
10.1 8
8 6.7
6.7 5.5
5.5 4.6
4.6 3.7
3.7 3.1
3.1 2.4
2.4 1.7
1.7 0.9
0.9 0
0 1.6
1.6 5.1
over 5.1
80°W110°W140°W 25°N
45°N
65°N
S component
under 0.27
0.27 0.2
0.2 0.15
0.15 0.12
0.12 0.08
0.08 0.04
0.04 0.01
0.01 0.02
0.02 0.05
0.05 0.08
0.08 0.13
0.13 0.21
0.21 0.34
0.34 0.55
over 0.55
80°W110°W140°W 25°N
45°N
65°N
S component
Figure 1: Mean ancestral predicted (P) and mean specific (S) component per regular one degree grid-cell (CRS: WGS84/EPSG: 4326) of surface colouration (8bit
grey-value; absolute black (0) to white (255)) and body size (lateral area; cm2) of 153 dragonfly species in North America. Note within both P components the tendency
of a increase in darkness/decrease in body size towards north and the accent of North America’s geophysical structure (Great Lakes and Appalachians in the NE, Great
Plains in the SE, and amidst the Rocky Mountains and the Sierra Nevada in the E, the Great Basin Desert). Meanwhile S components deviate especially among the
mountain ranges of western North America.
6
PERIODICITY IN ANNUAL IRRADIANCE
Adjusted R-squared values of the correlation between
mean monthly horizontal irradiance and mean ances-
tral predicted component (P) of surface colouration and
body size, respectively, exhibits a decrease of explained
variance towards the solstice (around June 21st) and in-
creased again afterwards (Fig. 2). In contrast, adjusted
R-squared values from the specific (S) component of
surface colouration increased towards the solstice but
were just correlated with four of twelve months. Ad-
justed R-squared values of the correlation with the spe-
cific (S) component of size were subject to just minor
fluctuations during the year.
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0.00
0.05
0.10
0.15
0.20
0.25
0.30
S Component
P Component
Colouration
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
0.00
0.05
0.10
0.15
0.20
0.25
0.30
Body size
Figure 2: Adjusted R-squared values of the correlation between mean monthly horizontal irradiance (kWh m2
d1) per grid-cell, and mean ancestral predicted (P) and specific (S) surface colouration (8bit grey-value; 0-255)
and body size (lateral area; cm2), respectively, of 153 dragonflies species in North America. Vertical lines mark
the period of the most active pre-emergence development referring to the variable ”Irrad. ep.”. Note the decrease
of explanatory power in the mean ancestral predicted (P) component of both traits during these months.
Discussion
My results indicate that spatial variation in surface
colouration of North American dragonfly assemblages
is consistent with the predictions of TMH, as the mean
darkness decreases from cold regions with less solar ir-
radiance towards those with warm conditions and high
solar irradiance. By generating phylogenetic eigen-
vectors (PVR), I found a considerable proportion of
this signal to be firmly conserved within the phyloge-
netic structure. Since dragonflies are assumed to be
originated in the subtropic conditions of carbonifer-
ous Pangea, this signal can be interpreted as long-term
adaptations in colour to changing (tendentially colder)
environment (May 1982;Parrish 1993). Thus, sur-
face colouration may have initially qualified dragonflies
to colonize even the subpolar conditions some extant
species now inhabit (Donnelly 2004), by mediating the
diversification of lighter-coloured ancestors. Still the
ancestral predicted (P) component explained only 32%
(adj. r2) of the mean grey-value of all dragonfly assem-
blages. However, I am convinced these indications are
profoundly promising and will certainly improve when
species-level information is included. Nonetheless, due
to a lack of DNA sequences even the genus-level struc-
ture used in this analysis is a synthesis of several works
and not exclusively based on phylogenetic propinquity.
In some cases the integration of merely a single species
would be necessary to elongate the structure and refine
the distances within a complete genus. On that account
the minor correlation between environmental conditions
and the S component of colour can be explained, too.
Further it is important to note that this unique species
level variation technically includes the systematic er-
ror of several sources as well (Ives et al. 2007; e.g.
unprecise clipping, intraspecific differences in coloura-
tion: age and ecotyp’s; Corbet 2004). By the claim
to use currently available data (originally collected for
several different applications) of multiple empiric di-
mensions (geographic and phylogenetic), I had limited
capabilities at disposal to visualize such effects. For
instance, spatial pattern of higher resolution, like micro-
habitats (e.g. south oriented slopes), cannot be dis-
played accurately at such large scales and were hence a
cluster of deviation. Consequently, one can observe that
S components of both traits tend to deviate from their
expectation especially in high altitudes (Fig. 1).
The ancestral predicted part of body size exhibits a
clear pattern of spatial variation, which can be described
as converse to the assumptions Bergmann (1848) ex-
pressed regarding the volume-body surface ratio in
mammals. Indeed the mean P body size in faunal assem-
blages tend to be smaller in cool/dry regions compared
to those with warm/moist conditions. This signal and
its determinants remained consistent whether the an-
cestral predicted or specific component was considered.
7
Unexpectedly, my results indicate that small species
occur in areas with low precipitation, which stands in
contrast to the predictions of a pattern related to respi-
ratory water-loss (Davis et al. 2000). Intuitively, small-
bodied species should have an advantage compared to
large ones, as less surface means less respiration (Addo-
Bediako et al. 2001). Simultaneously however, drag-
onflies may benefit from increased heating and greater
diversification rates in cold regions (Ismail et al. 2012).
Another explanation for such a pattern might be the
obligate connection of dragonfly larvae to aquatic sys-
tems and the availability of macrozoobentos, on which
they feed. This indeed is a vivid example for the com-
plexity, continuity and trade-off character among these
performance traits that finally form a species’ niche.
This abstract trait, the niche, is effectively a function
of several organismal characteristics (e.g. thermoreg-
ulation by locomotion and other behavioural strategies
like ”wing-wirring”; May 1976 or posture; Tracy et al.
1979). Due to the sampling methods of this study, it
was only possible to trace the currently realized niche.
In other words the distribution information certainly
includes human impact and several other biotic fac-
tors on dragonfly distribution ranges as well, which
consequently underestimates influence of abiotic deter-
minates (Sober´
on 2007). Yet environmental conditions
were found to be relatively important constraints (niche
requirements) to which species are liable and which are
ultimately reflected by their physiological adjustments.
Since calculations of phylogenetic autocorrelation were
based on the same structure, it was in fact surprising to
find a significant difference in the degree of manifes-
tation of phylogeny within colour and size. Although
I cannot trace it in detail with this dataset, the results
indicate that dragonflies adapt more fast to changing
ambient (thermal) conditions in terms of mean body
size (P:56% adj. r2= 0.127/S:43% adj. r2= 0.114) than
in terms of mean colouration (P:32% adj. r2= 0.305/S:
67% adj. r2= 0.015). Field studies and experimental
manipulations of body size directly confirm this con-
nection between size divergence and the build-up of
reproductive isolation (McKinnon et al. 2004). Thus
size-associative mating seems to be a very general ten-
dency, which causes a relatively rapid manifestation of
differences between populations. On the other hand,
variation in the S component of colouration (herein
species-level) is probably mediated by several biotic
mechanism and thereby relatively conserved. Informa-
tion on females should be included to test this assump-
tion, since they are principally less influenced by sexual
selection, while size and performance will influences
their reproduction more direct (e.g. egg load; McVey
1984,Corbet 2004). Nonetheless, it is very likely that
the rapid biodiversity loss of the last decades reflect at
least partially the velocity upon which species are able
to realize such physiological adjustments (Wiens et al.
2010).
Since extreme fluctuations in the intensity of di-
urnal irradiance (e.g. 24h daylight in Arctic summer)
during the year will engender a underestimation of the
correlation between colour and mean annual irradiance,
I included a modification of this variable. Within the
six months of main flying-/mating- activity (Irrad. ep.;
Fig. 2), between spring and autumn equinox, heat gain
was expected to be most relevant. Interestingly enough
the results show a decrease in explanatory power during
this period. Contrary to the expectation species seem
to be especially adapted to months with relatively less
irradiance. This seems explicable, for one of the most
direct benefits of thermoregulatory features (adaptive
melanism) is a prolonged annual activity (May 1977).
However, it is important to highlight that this pattern is
attributable to the spatial allocation of the processed as-
semblages (see loadings in Appendix 1). On that note it
becomes important that body size as well as colouration
have been found to be non-linearly related with tem-
perature, and boosting approaches were able to display
thresholds marking clear shits regarding the quality of
this relationship (Rodr´
ıguez et al. 2008; Zeuss et al. in
prep.). In all of these examples, cold regions (months
with less irradiance) seem to carry this signal, which
highlights again the evolutionary significance of both
traits in regard to thermal environment.
Thanks to the work of Olalla-T´
arraga et al. (2006)
and Zeuss et al. (in prep.) I was capable to compare
some facets of these results in a larger geographic con-
text. Former was able to show the same pattern of a
poleward decline in body size for snakes and lizards
(heliotherms) as well, in Europe and North America.
Although the method and species differ, the geographic
pattern of body size variation that accents and its deter-
minants were very similar to the one I was able to dis-
play (additional patterns displaying raw values of both
traits are attached in Appendix 3). The latter too, found
the states of TMH to be valid for European Odonata.
Compared between both continents, the proportion of
variance described by thermal environment was notably
larger in Europe than in North America. Regarding
colouration, such a more detailed pattern could be sim-
ply the consequence of a broader taxonomic spectrum.
While Zeuss et al. (in prep.) analysed trait information
of the entire set (107) of European species, illustrations
of the North American Odonata species are relatively
rare. Furthermore, the integration of new, mostly digital
sources remains a problem. Although ”The Dragonflies
of North America” by Needham et al. (2000) comprises
153 species (in total 484; OdonataCentral.org) of one
of the main suborders, the illustrations of at least three
genera are completely absent in the first Edition (Macro-
8
mia,Libellula). One of them, the genus Leucorrhinia,
is distributed nearly exclusively in the northern parts
of the continent. Thus, these species may not simply
contribute to the cover, by integrating additional 30.000
entries, but to the strength of a signal conditional to
thermal melanism.
However, even more relevant is probably the bio-
geographic history of both continents. Although the
environmental conditions and most of the genera are
relatively similar, they principally experienced rather
different colonisation by those. Results on latitudi-
nal clines in body size of mammals have found to be,
at least indirectly, a product of continuous colonization
(species-turnover), parallel to the exposition of glaciated
areas (Diniz-Filho et al. 2009). As PVR accounts for
such cases there is a good reason to assume that geo-
physical barriers can increase the selective pressure to-
wards taxa with a trait constitution to adapt beyond
these. Since the mountain chains of North America a
priori allow such movement (S-N orientation), this fact
indeed could be a potent explanation for a less strong
correlation with thermal environment compared to Eu-
rope, but a relatively high degree of manifestation of
thermal melanism within the phylogenetic structure.
Nonetheless the relation between colour and size,
respectively, and their abiotic constraints remains un-
doubtedly sufficient to be detectable even above the im-
mense background variation that must exist on such
broad scales. This finally solidifies the generality and
evolutionary significance of both characteristics for the
spatial distribution of dragonfly species.
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Appendix:1 Analysis Principal components
Table 2: Results from principal component analysis of the categories thermal environment and precipitation.
Loadings highlighted in bold contain the major proportion of variance of each included variable. Abbreviations
are described in Section Material and Methods.
Thermal environment Precipitation
Variables PC 1 PC 2 Variables PC 1 PC 2
AMT 0.972 AP 0.992
MDR 0.509 0.732 PS 0.870 0.475
IT 0.801 0.320 PWeQ 0.896 -0.395
TAR -0.478 0.858 PDQ -0.433 0.832
TS 0.762 0.623 PWaQ 0.882 0.455
MTWeQ 0.834 -0.534 PCQ 0.918 -0.360
MTDQ -0.256 0.957 PWeM 0.733
MTWaQ 0.416 0.570 PDM 0.850 0.220
MTCQ 0.809 -0.393
MaxTWaM 0.819 0.486
MinTCM 0.917 -0.383
Annual 0.899
SS loadings 6.565 3.830 SS loadings 5.611 1.475
Proportion Variance 0.547 0.319 Proportion Variance 0.701 0.184
Cumulative Variance 0.547 0.866 Cumulative Variance 0.701 0.886
under 1.4
1.4 1.1
1.1 0.9
0.9 0.7
0.7 0.5
0.5 0.3
0.3 0.1
0.1 0.1
0.1 0.3
0.3 0.5
0.5 0.7
0.7 1
1 1.3
1.3 1.6
over 1.6
80°W110°W140°W 25°N
45°N
65°N
Thermal environment PC 1
under 1.1
1.1 1
1 0.8
0.8 0.7
0.7 0.6
0.6 0.5
0.5 0.3
0.3 0.1
0.1 0.2
0.2 0.4
0.4 0.7
0.7 1
1 1.3
1.3 1.7
over 1.7
80°W110°W140°W 25°N
45°N
65°N
Precipitation PC 1
under 1.8
1.8 0.9
0.9 0.4
0.4 0.2
0.2 0
0 0.1
0.1 0.2
0.2 0.3
0.3 0.5
0.5 0.6
0.6 0.7
0.7 0.8
0.8 0.9
0.9 1
over 1
80°W110°W140°W 25°N
45°N
65°N
PC 2
under 1.2
1.2 1
1 0.8
0.8 0.6
0.6 0.5
0.5 0.3
0.3 0.2
0.2 0
0 0.2
0.2 0.4
0.4 0.6
0.6 0.8
0.8 1
1 1.2
over 1.2
80°W110°W140°W 25°N
45°N
65°N
PC 2
Figure 3: Distribution patterns of the scores within each principal component per regular on degree grid-cell (CRS:
WGS84/EPSG: 4326), displayed for the extend of this analysis.
13
Appendix:2 Data Correlations
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21 0 1 2
95 100 105 110 115 120
R² = 0.29, p < 0.001
Thermal environment PC 1
Mean P component
Colouration
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4321 0 1
95 100 105 110 115 120
R² = 0.01, p < 0.001
Thermal environment PC 2
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1 0 1 2 3 4
95 100 105 110 115 120
R² = 0.01, p < 0.001
Pricipitation PC 1
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2 0 2 4 6
95 100 105 110 115 120
R² = 0, p = 0.371
Pricipitation PC 2
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0 500 1000 1500 2000 2500 3000
95 100 105 110 115 120
R² = 0.02, p < 0.001
Altitude
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4.0 4.5 5.0 5.5 6.0 6.5 7.0
95 100 105 110 115 120
R² = 0.18, p < 0.001
Irrad. ep.
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2.5 3.0 3.5 4.0 4.5 5.0 5.5
95 100 105 110 115 120
R² = 0.25, p < 0.001
Annual
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21 0 1 2
30 20 10 0 10 20
R² = 0, p = 0.750
Mean S component
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4321 0 1
30 20 10 0 10 20
R² = 0.02, p < 0.001
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1 0 1 2 3 4
30 20 10 0 10 20
R² = 0.03, p < 0.001
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2 0 2 4 6
30 20 10 0 10 20
R² = 0.02, p < 0.001
0 500 1000 1500 2000 2500 3000
30 20 10 0 10 20
R² = 0.02, p < 0.001
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4.0 4.5 5.0 5.5 6.0 6.5 7.0
30 20 10 0 10 20
R² = 0.02, p < 0.001
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2.5 3.0 3.5 4.0 4.5 5.0 5.5
30 20 10 0 10 20
R² = 0, p = 0.015
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21 0 1 2
2.0 2.5 3.0 3.5
R² = 0.13, p < 0.001
Mean P component
Size
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4321 0 1
2.0 2.5 3.0 3.5
R² = 0, p = 0.622
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1 0 1 2 3 4
2.0 2.5 3.0 3.5
R² = 0.11, p < 0.001
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2 0 2 4 6
2.0 2.5 3.0 3.5
R² = 0.03, p < 0.001
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0 500 1000 1500 2000 2500 3000
2.0 2.5 3.0 3.5
R² = 0.11, p < 0.001
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4.0 4.5 5.0 5.5 6.0 6.5 7.0
2.0 2.5 3.0 3.5
R² = 0.04, p < 0.001
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2.5 3.0 3.5 4.0 4.5 5.0 5.5
2.0 2.5 3.0 3.5
R² = 0.09, p < 0.001
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21 0 1 2
1.0 0.5 0.0 0.5 1.0 1.5 2.0
R² = 0.11, p < 0.001
Mean S component
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4321 0 1
1.0 0.5 0.0 0.5 1.0 1.5 2.0
R² = 0, p = 0.026
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1 0 1 2 3 4
1.0 0.5 0.0 0.5 1.0 1.5 2.0
R² = 0, p = 0.034
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2 0 2 4 6
1.0 0.5 0.0 0.5 1.0 1.5 2.0
R² = 0.02, p < 0.001
0 500 1000 1500 2000 2500 3000
1.0 0.5 0.0 0.5 1.0 1.5 2.0
R² = 0.10, p < 0.001
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4.0 4.5 5.0 5.5 6.0 6.5 7.0
1.0 0.5 0.0 0.5 1.0 1.5 2.0
R² = 0.14, p < 0.001
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2.5 3.0 3.5 4.0 4.5 5.0 5.5
1.0 0.5 0.0 0.5 1.0 1.5 2.0
R² = 0.14, p < 0.001
Figure 4: Results from univariate least-squares regressions between principal components of thermal environment and precipitation, as well as altitude, monthly
irradiance during the emergence period, annual irradiance, and mean ancestral predicted (P) and specific (S) component, respectively. Components are based on mean
surface colouration (8bit grey-value; 0-255) and body size (lateral area; cm2) per regular one degree grid-cell of 153 dragonfly species in North America.
14
Appendix:3 Data Patterns of mean raw colour and size
under 89
89 92.3
92.3 94.5
94.5 96.1
96.1 97.4
97.4 98.4
98.4 99.3
99.3 100.1
100.1 100.9
100.9 101.9
101.9 103.1
103.1 104.5
104.5 106.2
106.2 108.9
over 108.9
80°W110°W140°W 25°N
45°N
65°N
Colouration Raw
under 2.1
2.1 2.2
2.2 2.26
2.26 2.33
2.33 2.4
2.4 2.45
2.45 2.5
2.5 2.55
2.55 2.61
2.61 2.67
2.67 2.74
2.74 2.8
2.8 2.91
2.91 3.09
over 3.09
80°W110°W140°W 25°N
45°N
65°N
Body size Raw
Figure 5: Mean raw surface colouration (8bit grey-value; absolute black (0) to white (255)) and body size (lateral
area; cm2) per regular one degree grid-cell (CRS: WGS84/EPSG: 4326) of 153 dragonfly species in North America.
Note within both traits the tendency of a increase in darkness/decrease in body size towards north and especially
within colouration the accent of North America’s geophysical structure (Great Lakes and Appalachians in the NE,
Great Plains in the SE, and amidst the Rocky Mountains and the Sierra Nevada in the E, the Great Basin Desert).
15
Appendix:4 Data List of species
1 Aeshna canadensis 61 Gomphaeschna antilope 121 Progomphus borealis
2 Aeshna clepsydra 62 Gomphaeschna furcillata 122 Progomphus obscurus
3 Aeshna constricta 63 Gomphus abbreviatus 123 Remartinia luteipennis
4 Aeshna eremita 64 Gomphus adelphus 124 Rhionaeschna californica
5 Aeshna interrupta 65 Gomphus apomyius 125 Rhionaeschna multicolor
6 Aeshna juncea 66 Gomphus australis 126 Rhionaeschna psilus
7 Aeshna palmata 67 Gomphus borealis 127 Somatochlora albicincta
8 Aeshna persephone 68 Gomphus cavillaris 128 Somatochlora calverti
9 Aeshna septentrionalis 69 Gomphus consanguis 129 Somatochlora cingulata
10 Aeshna sitchensis 70 Gomphus descriptus 130 Somatochlora elongata
11 Aeshna subarctica 71 Gomphus dilatatus 131 Somatochlora ensigera
12 Aeshna tuberculifera 72 Gomphus diminutus 132 Somatochlora filosa
13 Aeshna umbrosa 73 Gomphus exilis 133 Somatochlora forcipata
14 Aeshna verticalis 74 Gomphus externus 134 Somatochlora franklini
15 Aeshna walkeri 75 Gomphus fraternus 135 Somatochlora georgiana
16 Anax amazili 76 Gomphus geminatus 136 Somatochlora hineana
17 Anax junius 77 Gomphus graslinellus 137 Somatochlora hudsonica
18 Anax longipes 78 Gomphus hodgesi 138 Somatochlora incurvata
19 Anax walsinghami 79 Gomphus hybridus 139 Somatochlora kennedyi
20 Aphylla angustifolia 80 Gomphus kurilis 140 Somatochlora linearis
21 Aphylla protracta 81 Gomphus lineatifrons 141 Somatochlora minor
22 Aphylla williamsoni 82 Gomphus lividus 142 Somatochlora sahlbergi
23 Arigomphus furcifer 83 Gomphus lynnae 143 Somatochlora semicircularis
24 Arigomphus lentulus 84 Gomphus militaris 144 Somatochlora tenebrosa
25 Arigomphus maxwelli 85 Gomphus minutus 145 Somatochlora walshii
26 Arigomphus pallidus 86 Gomphus modestus 146 Somatochlora whitehousei
27 Arigomphus submedianus 87 Gomphus ozarkensis 147 Somatochlora williamsoni
28 Arigomphus villosipes 88 Gomphus parvidens 148 Stylogomphus albistylus
29 Basiaeschna janata 89 Gomphus quadricolor 149 Stylurus amnicola
30 Boyeria grafiana 90 Gomphus rogersi 150 Stylurus intricatus
31 Boyeria vinosa 91 Gomphus septima 151 Stylurus ivae
32 Cordulegaster bilineata 92 Gomphus vastus 152 Stylurus laurae
33 Cordulegaster diadema 93 Gomphus ventricosus 153 Stylurus notatus
34 Cordulegaster diastatops 94 Gomphus viridifrons 154 Stylurus olivaceus
35 Cordulegaster dorsalis deserticola 95 Gynacantha nervosa 155 Stylurus plagiatus
36 Cordulegaster dorsalis dorsalis 96 Hagenius brevistylus 156 Stylurus potulentus
37 Cordulegaster erronea 97 Lanthus parvulus 157 Stylurus scudderi
38 Cordulegaster maculata (northern) 98 Lanthus vernalis 158 Stylurus spiniceps
39 Cordulegaster maculata (southern) 99 Nasiaeschna pentacantha 159 Triacanthagyna trifida
40 Cordulegaster maculata 100 Octogomphus specularis
41 Cordulegaster obliqua fasciata 101 Ophiogomphus acuminatus
42 Cordulegaster obliqua olbiqua 102 Ophiogomphus aspersus
43 Cordulegaster sayi 103 Ophiogomphus australis
44 Cordulia shurtleffii 104 Ophiogomphus bison
45 Coryphaeschna adnexa 105 Ophiogomphus carolus
46 Coryphaeschna ingens 106 Ophiogomphus colubrinus
47 Coryphaeschna viriditas 107 Ophiogomphus howei
48 Dorocordulia lepida 108 Ophiogomphus incurvatus
49 Dorocordulia libera 109 Ophiogomphus mainensis
50 Dromogomphus armatus 110 Ophiogomphus morrisoni
51 Dromogomphus spinosus 111 Ophiogomphus occidentis
52 Dromogomphus spoliatus 112 Ophiogomphus rupinsulensis
53 Epiaeschna heros 113 Ophiogomphus severus montanus
54 Erpetogomphus compositus 114 Ophiogomphus severus severus
55 Erpetogomphus crotalinus 115 Ophiogomphus westfalli
56 Erpetogomphus designatus 116 Oplonaeschna armata
57 Erpetogomphus eutainia 117 Phyllogomphoides albrighti
58 Erpetogomphus heterodon 118 Phyllogomphoides stigmatus
59 Erpetogomphus lampropeltis natrix 119 Progomphus alachuensis
60 Erpetogomphus lampropeltis 120 Progomphus bellei
16
Appendix:5 Analysis Species plate
142 3 586 7 91210 11 13 1614 15
1917 18 20 2321 22 2624 25 27 3028 29 31 32
35
33 34 36 39
37 38 42
40 41 43 4644 45 47 48
5149 50 52 55
53 54 58
56 57 59 62
60 61 63 64
6765 66 68 7169 70 7472 73 75 7876 77 79 80
1:0,5= 4cm
17
Appendix:6 Data Species plate
8381 82 8684 85 87 9088 89 91 92 9593 94 96
9997 98 102100 101 103 106104 105 107 108 111109 110 112
115113 114 116 117 120118 119 121 124122 123 125 128126 127
131
129 130 132 133 136134 135 137 140138 139 141 144142 143
147
145
146 148 149 152150 151 153 156154 155 157 158 159
1:0,5= 4cm
Figure 6: Colour images of the 153 processed dragonfly species from Needham et al. 2000. The image-numbers
refer to the list of species in Appendix 4. Image size has been changed in a 1 to 0,5 ratio, visible in the scale above.
18
Appendix:7 Data Phylogenetic structure
Figure 7: Ultrametric, phylogenetic structure of 153 dragonfly species in North America, compiled from different
molecular works (Dumont et al. 2005,Misof et al. 2001,Fleck et al. 2008) and taxonomic information (catalogue-
oflife.org;Tol et al. 2013). Branch colours on the tree represent the families: Gomphidae (green), Corduliidae
(red), and Cordulegastridae (orange).
19
... Recent studies on North American (Hassall 2012;Pinkert 2013), European , African (Clausnitzer et al., 2012;Pinkert et al., 2020;Deacon et al., 2021), and Brazilian Odonata (Miguel et al., under review) highlight a strong decrease of species richness with increasing latitude, a common biodiversity pattern known as the latitudinal diversity gradient. Although the centers of endemism and species richness in Odonata remain to be rigorously empirically assessed at the global scale, continent-wide studies ; see also Corser et al., 2014) and qualitative assessments generally highlight the tropical rain forests of central and East Africa (particularly Gabon and Uganda), Southeast Asia (particularly Yunnan and Myanmar), and the Neotropics (particularly the Amazons, Panama, and Yucatan Peninsula). ...
... Ectotherms, therefore, evolved adaptations to the temperature regime in which they live. From a physiological perspective, strong arguments exist that variation in the color lightness and body size of species are of fundamental importance to regulate the heat gain and loss in insects (reviewed in Pinkert 2019). Larger species retain body heat more efficiently than smaller species owing to their lower surface-area-to-volume ratio, and darker colored species heat up faster than lighter colored species because they absorb more solar radiation (e.g. ...
... Acquah-Lamptey et al., 2020). Other benefits of melanization include enhanced immunocompetence of larger species and enhanced pathogen resistance (Gloger's rule) as well as UV protection (Pinkert 2019). In addition, traits such as body and wing sizes tend to correlate, at least loosely, with species' dispersal ability or propensity (Chapter 24). ...
Chapter
This research-level text documents the latest advances in odonate biology and relates these to a broader ecological and evolutionary research agenda. Despite being one of the smallest insect orders, dragonflies offer a number of advantages for both laboratory and field studies. In fact, they continue to make a crucial contribution to the advancement of our broader understanding of insect ecology and evolution. This new edition provides a critical summary of the major advances in these fields. Contributions from many of the leading researchers in dragonfly biology offer new perspectives and paradigms as well as additional unpublished data. The editors have carefully assembled a mix of theoretical and applied chapters (including those addressing conservation and monitoring) as well as a balance of emerging (e.g. molecular evolution) and established research topics, providing suggestions for future study in each case. This accessible text is not about dragonflies per se, but rather an essential source of knowledge that describes how different sets of evolutionary and ecological principles/ideas have been tested on a particular taxon. This second edition of Dragonflies and Damselflies is suitable for graduate students and researchers in entomology, evolutionary biology, population and behavioral ecology, community ecology, and conservation biology. It will be of particular interest and use to those working on insects and an indispensable reference text for odonate biologists.
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