Pesticide concentrations in a threatened freshwater turtle (Emys orbicularis): Seasonal and annual variation in the Camargue wetland, France

Wetlands are among the most threatened ecosystems on the planet and pollution is a major factor causing the decline of wetland biodiversity. Despite the increasing use of pesticides, their fate and effects on freshwater reptiles remain largely unknown. We studied the European pond turtle (Emys orbicularis), a long-lived species at risk with a high exposure potential to pesticides. Between 2018 and 2020, we measured 29 pesticides and metabolites in 408 blood samples of turtles from two populations in the Camargue wetland (France). We were able to quantify 24 compounds and at least one pesticide or one degradation product in 62.5% of samples. Pesticide occurrences and concentrations were low, except for a herbicide widely used in rice cultivation and locally detected in water: bentazone that reached high blood concentrations in E. orbicularis. The occurrence and the concentration of pesticides in E. orbicularis blood depended mainly on the site and the sampling date in relation to pesticide application. Individual characteristics (sex, age, body condition) did not explain the occurrence or the concentration of pesticides found in turtle blood. Assessing the exposure of aquatic wildlife to a cocktail of currently-used pesticides is a first and crucial step before studying their effects at the individual and population levels.

Effects of temperature heterogeneity on freshwater turtle habitat selection at their northern range limit

Environmental temperature is a crucial resource for ectotherms, affecting their physiology, behaviour and fitness. To maintain body temperatures within a suitable performance range, ectotherms select thermally-favourable locations, but this selection may be challenging in environments with high spatio-temporal heterogeneity. We assessed thermal habitat selection in two freshwater turtles (Emydoidea blandingii; Chrysemys picta) within a thermally heterogeneous environment at two spatial scales (selection of home ranges within the landscape, selection of locations within home ranges) and across seasons, by comparing temperatures at turtle locations vs. those available in the environment. Turtles selected warmer locations compared to those available in aquatic and terrestrial habitats only within home ranges, but did not show any temperature preferences when selecting home ranges at the larger scale. Turtles selected locations that were less thermally-variable than their surroundings, both at the home range scale and within home ranges. Thermal habitat selection was strongest during colder and more thermally-variable pre-nesting season compared to later periods. Despite differences in thermal mass between species, both species responded similarly to temperature variation. We conclude that freshwater turtles at their northern range margin select suitable microclimates within the suite of conditions that are naturally available.

Phylogenetic relationships of the North American catfishes (Ictaluridae, Siluriformes): Investigating the origins and parallel evolution of the troglobitic species

Insular habitats have played an important role in developing evolutionary theory, including natural selection and island biogeography. Caves are insular habitats that place extreme selective pressures on organisms due to the absence of light and food scarcity. Therefore, cave organisms present an excellent opportunity for studying colonization and speciation in response to the unique abiotic conditions that require extreme adaptations. One vertebrate family, the North American catfishes (Ictaluridae), includes four troglobitic species that inhabit the karst region bordering the western Gulf of Mexico. The phylogenetic relationships of these species have been contentious, and conflicting hypotheses have been proposed to explain their origins. The purpose of our study was to construct a time-calibrated phylogeny of Ictaluridae using first-occurrence fossil data and the largest molecular dataset on the group to date. We test the hypothesis that troglobitic ictalurids have evolved in parallel, thus resulting from repeated cave colonization events. We found that Prietella lundbergi is sister to surface-dwelling Ictalurus and that Prietella phreatophila + Trogloglanis pattersoni are sister to surface-dwelling Ameiurus, suggesting that ictalurids colonized subterranean habitats at least twice in evolutionary history. The sister relationship between Prietella phreatophila and Trogloglanis pattersoni may indicate that these two species diverged from a common ancestor following a subterranean dispersal event between Texas and Coahuila aquifers. We recovered Prietella as a polyphyletic genus and recommend P. lundbergi be removed from this genus. With respect to Ameiurus, we found evidence for a potentially undescribed species sister to A. platycephalus, which warrants further investigation of Atlantic and Gulf slope Ameiurus species. In Ictalurus, we identified shallow divergence between I. dugesii and I. ochoterenai, I. australis and I. mexicanus, and I. furcatus and I. meridionalis, indicating a need to reexamine the validity of each species. Lastly, we propose minor revisions to the intrageneric classification of Noturus including the restriction of subgenus Schilbeodes to N. gyrinus (type species), N. lachneri, N. leptacanthus, and N. nocturnus.

Do roads affect the abundance of garter (Thamnophis sirtalis) and redbelly snakes (Storeria occipitomaculata)?

The greatest driver of the current biodiversity crisis is habitat loss. Roads are a major contributor to habitat loss because they destroy and fragment habitat, in addition to causing direct mortality. Animals may respond to roads either by avoiding them, thus leading to population isolation, or by attempting to cross them, thus potentially leading to increased mortality and, if so, also to population isolation. We studied the impact of road density on abundance of two snake species: redbelly snakes ( Storeria occipitomaculata Storer, 1839) and garter snakes ( Thamnophis sirtalis Linnaeus, 1758) around Ottawa, Canada. We hypothesized that roads are detrimental to snake populations due to road avoidance and mortality. Therefore, we predicted that snakes should be less abundant at sites with higher road density in their surroundings. We deployed cover boards at 28 sites along a gradient of road density in 2020 and 2021. We visited sites weekly, counted the number of individuals of both species, and measured snout–vent length (SVL) of all individuals captured. We captured fewer garter snakes at sites surrounded by more roads and fewer redbelly snakes at sites surrounded by more urban habitat. Snakes at sites surrounded by more roads were not smaller. The effects of roads and urbanization on the number of snakes were modest, but indicate decreasing population sizes that could lead to loss of ecological function.

Developing a classification system to assign activity states to two species of freshwater turtles

Research in ecology often requires robust assessment of animal behaviour, but classifying behavioural patterns in free-ranging animals and in natural environments can be especially challenging. New miniaturised bio-logging devices such as accelerometers are increasingly available to record animal behaviour remotely, and thereby address the gap in knowledge related to behaviour of free-ranging animals. However, validation of these data is rarely conducted and classification model transferability across closely-related species is often not tested. Here, we validated accelerometer and water sensor data to classify activity states in two free-ranging freshwater turtle species (Blanding's turtle, Emydoidea blandingii, and Painted turtle, Chrysemys picta). First, using only accelerometer data, we developed a decision tree to separate motion from motionless states, and second, we included water sensor data to classify the animal as being motionless or in-motion on land or in water. We found that accelerometers separated in-motion from motionless behaviour with > 83% accuracy, whereas models also including water sensor data predicted states in terrestrial and aquatic locations with > 77% accuracy. Despite differences in values separating activity states between the two species, we found high model transferability allowing cross-species application of classification models. Note that reducing sampling frequency did not affect predictive accuracy of our models up to a sampling frequency of 0.0625 Hz. We conclude that the use of accelerometers in animal research is promising, but requires prior data validation and development of robust classification models, and whenever possible cross-species assessment should be conducted to establish model generalisability.

Effects of landscape composition on wetland occupancy by Blanding’s Turtles (Emydoidea blandingii) as determined by environmental DNA and visual surveys

Habitat loss and degradation have led to the extinction of many species worldwide. The endangered Blanding’s Turtle (Emydoidea blandingii (Holbrook, 1838)), a semi-aquatic freshwater turtle, occupies a wide range of wetlands and landscapes primarily in southeastern Canada and the Great Lakes region of the United States. We explored whether the probability of wetland occupancy by Blanding’s Turtles is affected by the surrounding landscape. We used visual surveys, environmental DNA, and Atlas data to document the presence of Blanding’s Turtles in wetlands in Ottawa, Ontario, Canada. We tabulated landscape composition at multiple scales surrounding the wetlands to determine whether landscape composition can predict wetland occupancy. Generally, wetlands surrounded by forest and other undisturbed lands were most likely to harbour Blanding’s Turtles, whereas those surrounded by more human-disturbed lands were least likely to harbour Blanding’s Turtles. Larger wetlands and a high proportion of wetlands in the surrounding landscape also increased the probability of occupancy by Blanding’s Turtles. Finally, older wetlands were more likely to be occupied by Blanding’s Turtles. The ability to estimate a species’ probability of occupancy can aid in conservation efforts, such as critical habitat delineation.

Determinants of Legacy Persistent Organic Pollutant Levels in the European Pond Turtle (Emys orbicularis) in the Camargue Wetland, France

Many banned persistent organic pollutants (POPs) remain for decades in the aquatic environment and can have harmful effects on long-lived predators because of their high bioaccumulation and biomagnification potentials. We investigated the occurrence and levels of 18 polychlorinated biphenyls (PCBs) and 16 organochlorine pesticides in European pond turtles (n = 174) from April to July 2018 in the Camargue wetland, France. Although the Camargue was highly contaminated in previous decades, plasma occurrence and levels of POPs were very low: we were able to quantify only 3 of the 34 compounds we analyzed in >10% of the turtles. The burdens from POPs did not differ between males and females and were uncorrelated with sampling date and body mass. We observed differences in POP burdens between turtles from the 2 sampling sites. One possible explanation is that the sampling sites were in different agricultural hydraulic systems: plasma occurrence and levels were higher for PCB-52 and hexachlorobenzene in turtles captured in drainage channels and for PCB-153 at the site that receives irrigation. Finally, the occurrence and levels of PCB-153 in turtles increased with age, likely because of bioaccumulation and much higher exposure 20 to 30 yr ago than now. Environ Toxicol Chem 2021;40:2261-2268. © 2021 SETAC.

Phylogenetic analysis of macroecological patterns of home range area in snakes

A home range is the area animals use to carry out routine activities such as mating, foraging, and caring for young. Thus, the area of a home range is an important indicator of an animal's behavioural and energetic requirements. While several studies have identified the factors that influence home range area (HRA), none of them has investigated global patterns of HRA among and within snake species. Here, we used a phylogenetic mixed model to determine which factors influence HRA in 51 snake species. We analysed 200 HRA estimates to test the influence of body mass, sex, age, diet, precipitation, latitude, winter and summer temperature, while controlling for the duration of the study and sample size. We found that males had larger HRA than females, that adults had larger HRA than juveniles, and that snake species with fish-based diets had smaller HRA than snake species with terrestrial vertebrate-based and invertebrate-based diets. We also found that HRA tended to increase as mean winter temperature decreases and tended to decrease with precipitation. After accounting for these factors, the phylogenetic heritability of HRA in snakes was low (0.21 ± 0.14). Determining the factors that dictate macroecological patterns of space use has important management implications in an era of rapid climate change.

Partial support for food availability and thermal quality as drivers of density and area used in Yarrow’s Spiny Lizards (Sceloporus jarrovii)

Contrary to traditional models, habitat selection in ectotherms may be chiefly based on a habitat’s thermal properties rather than its food availability, due to their physiological dependence on environmental temperature. We tested two hypotheses: that microhabitat use in ectotherms is driven by food availability and that it is driven by thermoregulatory requirements. We predicted that the density of lizards would increase and the mean area used would decrease with the natural arthropod (food) availability (or thermal quality) of a plot, as well as after experimentally increasing plot arthropod availability (or thermal quality). We established two plots in each of four treatments (food-supplemented, shaded, food-supplemented and shaded, and control) on a talus slope in Arizona, USA. We measured the density and area used in Yarrow’s Spiny Lizards (Sceloporus jarrovii Cope in Yarrow, 1875) before and after manipulations, and determined whether lizard density and area used were related to natural arthropod availability or thermal quality at the surface and in retreat sites. Density and area used were unaffected by the manipulations, but both increased with natural arthropod availability and decreased with higher thermal quality in retreat sites. These results provide partial support for both food availability and thermal quality as drivers of density and microhabitat use in S. jarrovii.

The impact of ectoparasitism on thermoregulation in Yarrow’s Spiny Lizards (Sceloporus jarrovii)

Parasites are ubiquitous and can have large impacts on the fitness of their hosts. The effects of ectoparasites on physiology, behaviour, and immune function suggest that they could be part of the factors which impact thermoregulation. We tested the hypothesis that ectoparasites impact thermoregulation in Yarrow’s Spiny Lizards (Sceloporus jarrovii Cope in Yarrow, 1875) living along an elevational gradient. We predicted a positive association between ectoparasite load and body temperature (Tb), and a negative association between ectoparasite load and effectiveness of thermoregulation (de – db index). We also predicted that the impacts of ectoparasites would be greatest at high elevation where thermal quality of the environment is low because the costs of thermoregulation increase with elevation and these costs can impact thermal immune responses. We found a significant association between the number of chiggers (Trombiculoidea) harboured by lizards and Tb that depended on elevation, but no association between ectoparasite load and de – db index. The mean chigger infection rate was associated with a ΔTb of +0.18 °C at low elevation (consistent with fever) and of –1.07 °C at high elevation (consistent with hypothermia). These findings suggest that parasitism by chiggers impacts lizard Tb in a way that depends on environmental thermal quality.

Ornate tree lizards (Urosaurus ornatus) thermoregulate less accurately in habitats of high thermal quality

Temperature plays a critical role for ectotherm performance and thus for fitness. Ectotherms, since unable to regulate their body temperature internally, use behavioural thermoregulation to maintain their body temperature within a range that maximizes performance. According to the cost-benefit model of thermoregulation, investment into thermoregulation is dictated by the trade-off between the costs and benefits of thermoregulating. The thermal quality of the environment is a major cost of thermoregulation because it directly affects the amount of time and energy that must be invested by an individual to achieve and maintain an optimal body temperature. Thus, in habitats of poor thermal quality, lizards should thermoregulate less. Using Urosaurus ornatus living at 10 sites each straddling two adjacent habitats (wash and upland), we tested the hypothesis that investment in thermoregulation is dependent on the thermal quality of the habitat. We found that the wash habitat had higher thermal quality indicated by a longer duration when optimal body temperatures could be reached. Lizards had more accurate body temperatures in the upland despite its poorer thermal quality. These results suggest that discrepancies in thermal quality between adjacent habitats affect investment in thermoregulation by lizards, but in a direction opposite to the main prediction of the cost-benefit model of thermoregulation.

Body size, not age, predicts parasite load in Clark’s Spiny Lizards (Sceloporus clarkii)

Determining the factors that influence parasite load is a fundamental goal of parasitology. Body size often influences parasite load in reptiles, but it is unclear whether higher levels of parasitism are a result of greater surface area of individuals (a function of size) or of longer periods of exposure to parasites (a function of age). Using skeletochronology in a wild population of Clark’s Spiny Lizards (Sceloporus clarkii Baird and Girard, 1852), we tested the hypotheses that (i) larger individuals have higher parasite loads due to increased surface area available for colonization by parasites and their vectors and that (ii) older individuals have higher parasite loads because they have had longer exposure to parasites and their vectors. Males harboured more ectoparasites than females. Males and females differed in how body size influenced chigger (Acari: Trombiculidae) load; larger males harboured more chiggers than smaller males, but this was not the case in females. Age did not affect ectoparasite load in either sex. These results emphasize the importance of disentangling the effects of size and age in models of parasitism to gain a clearer understanding of intraspecific variation in parasite load.

Geographic variation in body size and sexual size dimorphism of North American Ratsnakes (Pantherophis spp. s.l.)

Because body size affects nearly all facets of an organism’s life history, ecologists have long been interested in large-scale patterns of body-size variation, as well as why those large-scale patterns often differ between sexes. We explored body-size variation across the range of the sexually dimorphic Ratsnake complex (species of the genus Pantherophis Fitzinger, 1843 s.l.; formerly Elaphe obsoleta (Say in James, 1823)) in North America. We specifically explored whether variation in body size followed latitudinal patterns or varied with climatic variables. We found that body size did not conform to a climatic or latitudinal gradient, but instead, some of the populations with the largest snakes occurred near the core of the geographic range and some with the smallest occurred near the northern, western, and southern peripheries of the range. Males averaged 14% larger than females, although the degree of sexual size dimorphism varied between populations (range: 2%–25%). There was a weak trend for male body size to change in relation to temperature, whereas female body size did not. Our results indicate that relationships between climate and an ectotherm’s body size are more complicated than linear latitudinal clines and likely differ for males and females.

Tree lizard (Urosaurus ornatus) growth decreases with population density, but increases with habitat quality

Habitat selection models can explain spatial patterns in the relative abundance of animals in different habitats based on the assumption that fitness declines as density in a habitat increases. Ectotherms, such as lizards, may not follow predictions of density-dependent habitat selection models because temperature, which is unaffected by density, strongly influences their habitat selection. If competition for limited resources decreases fitness, then crowding should cause a decrease in body size and growth rates. We used skeletochronology and body size data from tree lizards (Urosaurus ornatus) at six sites that each spanned two habitats varying in quality to test the hypothesis that habitat selection is density dependent because growth is limited by competition for resources and by habitat quality. First, we tested that the maximum body size of lizards decreased with higher densities in a habitat by comparing growth between sites. Second, we tested whether body size and growth were higher in the habitat with more resources by controlling for density in a habitat and comparing growth between habitats in different sites. We found evidence of density-dependent growth in females, but not in males. Females in more crowded sites reached a smaller maximum size. Females in the higher quality habitat also grew larger than females in the lower quality habitat after controlling for differences in density between the habitats. Therefore, we found partial support for our hypothesis that competition for resources limits growth and causes density-dependent habitat selection.

Experimental removal reveals only weak interspecific competition between two coexisting lizards

Competition for resources is an important mechanism that shapes ecological communities. Interspecific competition can affect habitat selection, fitness, and abundance in animals. We used a removal experiment and mark–recapture to test the hypothesis that competition with the larger and more abundant Striped Plateau Lizard (Sceloporus virgatus H.M. Smith, 1938) limits habitat selection, fitness, and abundance in Ornate Tree Lizards (Urosaurus ornatus (Baird in Baird and Girard, 1852)). Ornate Tree Lizards in the plots where Striped Plateau Lizards were removed switched between habitat types more frequently and moved farther than Ornate Tree Lizards in control plots. However, there were no significant changes in the relative densities of Ornate Tree Lizards in each habitat type or in microhabitat use. We also found no changes in growth rates, survival, or abundance of Ornate Tree Lizards in response to the removal of Striped Plateau Lizards. Our results suggest that interspecific competition was not strong enough to limit habitat use or abundance of Ornate Tree Lizards. Perhaps interspecific competition is weak between coexisting species when resource levels are not severely depleted. Therefore, it is important to consider environmental conditions when assessing the importance of interspecific competition.

Support for the thermal coadaptation hypothesis from the growth rates of Sceloporus jarrovii lizards

The thermal coadaptation hypothesis posits that ectotherms thermoregulate behaviorally to maintain body temperatures (T_b) that maximize performance, such as net energy gain. Huey's (1982) energetics model describes how food availability and T_b interact to affect net energy gain. We tested the thermal coadaptation hypothesis and Huey's energetics model with growth rates of juvenile Yarrow's spiny lizards (Sceloporus jarrovii). We compared the preferred (selected) T_b range (T_sel) of lizards in high and low energy states to their optimal temperature (T_o) for growth over nine weeks, and determined whether the T_o for growth depended on food availability. We also measured the same lizards' resting metabolic rate at five T_bs to test the energetics model assumptions that metabolic cost increases exponentially with T_b and does not differ between energy states. The T_sel of lizards on both diets overlapped with the T_o for growth. The assumptions of the energetics model were verified, but the T_o for net energy gain did not depend on food availability. Therefore, we found support for the thermal coadaptation hypothesis. We did not find support for the energetics model, but this may have been due to low statistical power.

A test of the thermal coadaptation hypothesis with ultimate measures of fitness in flour beetles

Whole-organism performance of ectotherms depends on body temperature, which is tightly linked to environmental temperatures. Individuals attempting to optimize fitness must thus select appropriate temperatures. The thermal coadaptation hypothesis posits that T_o for traits closely linked to fitness should match temperatures selected by a species (T_set) and should coevolve with T_set. T_o may mismatch T_set if the thermal reaction norm for fitness is asymmetric. In this study, we examined six traits related to fitness in red and in confused flour beetles (Tribolium castaneum and T. confusum, respectively), including longevity, lifetime reproductive success, reproductive rate, and development time at four temperatures between 23 and 32°C. For reproductive traits, T_o matched T_set whereas for longevity T_o was lower than T_set. Tribolium species have a strongly r-selected life history strategy, therefore reproductive traits are likely more tightly linked to fitness than longevity due to high predation rates at early life stages. We therefore provide support for the thermal coadaptation hypothesis for reproductive traits that are tightly linked to fitness. Our results highlight the importance of knowing the relationships of traits to fitness when studying thermal physiology.

Do ectotherms partition thermal resources? We still do not know

Partitioning of the niche space is a mechanism used to explain the coexistence of similar species. Ectotherms have variable body temperatures and their body temperatures influence performance and, ultimately, fitness. Therefore, many ectotherms use behavioral thermoregulation to avoid reduced capacities associated with body temperatures far from the optimal temperature for performance. Several authors have proposed that thermal niche partitioning in response to interspecific competition is a mechanism that allows the coexistence of similar species of ectotherms. We reviewed studies on thermal resource partitioning to evaluate the evidence for this hypothesis. In almost all studies, there was insufficient evidence to conclude unequivocally that thermal resource partitioning allowed species coexistence. Future studies should include sites where species are sympatric and sites where they are allopatric to rule out alternative mechanisms that cause differences in thermal traits between coexisting species. There is evidence of conservatism in the evolution of most thermal traits across a wide range of taxa, but thermal performance curves and preferred temperatures do respond to strong selection under laboratory conditions. Thus, there is potential for selection to act on thermal traits in response to interspecific competition. Nevertheless, more stringent tests of the thermal resource partitioning hypothesis are required before we can assess whether it is widespread in communities of ectotherms in nature.

Faecal corticosterone metabolite concentrations are not a good predictor of habitat suitability for common gartersnakes

Measuring habitat suitability is important in conservation and in wildlife management. Measuring the abundance or presence-absence of a species in various habitats is not sufficient to measure habitat suitability because these metrics can be poor predictors of population success. Therefore, having some measure of population success is essential in assessing habitat suitability, but estimating population success is difficult. Identifying suitable proxies for population success could thus be beneficial. We examined whether faecal corticosterone metabolite (fCM) concentrations could be used as a proxy for habitat suitability in common gartersnakes (Thamnophis sirtalis). We conducted a validation study and confirmed that fCM concentrations indeed reflect circulating corticosterone concentrations. We estimated abundance, reproductive output and growth rate of gartersnakes in field and in forest habitat and we also measured fCM concentrations of gartersnakes from these same habitats. Common gartersnakes were more abundant and had higher reproductive outputs and higher growth rates in field habitat than in forest habitat, but fCM concentrations did not differ between the same two habitats. Our results suggest either that fCM concentrations are not a useful metric of habitat suitability in common gartersnakes or that the difference in suitability between the two habitats was too small to induce changes in fCM concentrations. Incorporating fitness metrics in estimates of habitat suitability is important, but these metrics of fitness have to be sensitive enough to vary between habitats.

A stringent test of the thermal coadaptation hypothesis in flour beetles

Whole-organism performance depends on body temperature and ectotherms have variable body temperatures. The thermal coadaptation hypothesis posits that thermal reaction norms have coevolved with thermal preference such that organisms attain optimal performance under a narrow range of body temperatures commonly experienced in the wild. Since thermal reaction norms are often similar, researchers interested in the effects of temperature on fitness often use one easily measured thermal reaction norm, such as locomotor performance, and assume it is a good proxy for fitness when testing the thermal coadaptation hypothesis. The extent to which this assumption holds, however, is often untested. In this study, we provide a stringent test of the thermal coadaptation hypothesis in red and in confused flour beetles by comparing the thermal reaction norm for reproductive output to the preferred body temperature range. We also test the assumption that locomotor performance can serve as a proxy for the thermal reaction norm for reproductive output, a more ultimate index of fitness. In both species, we measured the number of eggs laid, righting time, and sprint speed at eight temperatures, as well as the thermal preference in a thermal gradient. The number of eggs laid increased with female sprint speed and with male righting time, and all three performances had similar thermal reaction norms, with 80% of the maximum achieved between 23 and 37°C. Red flour beetles had preferred body temperatures that matched the optimal temperature for performance; confused flour beetles had lower preferred body temperature than the optimal temperature for performance. We found support for the assumption that locomotor performance can serve as a proxy for reproductive output in flour beetles, but we only found evidence for thermal coadaptation in one of the two species.

Postglacial recolonization in a cold climate specialist in western Europe: patterns of genetic diversity in the adder (Vipera berus) support the central-marginal hypothesis

Understanding the impact of postglacial recolonization on genetic diversity is essential in explaining current patterns of genetic variation. The central-marginal hypothesis (CMH) predicts a reduction in genetic diversity from the core of the distribution to peripheral populations, as well as reduced connectivity between peripheral populations. While the CMH has received considerable empirical support, its broad applicability is still debated and alternative hypotheses predict different spatial patterns of genetic diversity. Using microsatellite markers, we analysed the genetic diversity of the adder (Vipera berus) in western Europe to reconstruct postglacial recolonization. Approximate Bayesian Computation (ABC) analyses suggested a postglacial recolonization from two routes: a western route from the Atlantic Coast up to Belgium and a central route from the Massif Central to the Alps. This cold-adapted species likely used two isolated glacial refugia in southern France, in permafrost-free areas during the last glacial maximum. Adder populations further from putative glacial refugia had lower genetic diversity and reduced connectivity; therefore, our results support the predictions of the CMH. Our study also illustrates the utility of highly variable nuclear markers, such as microsatellites, and ABC to test competing recolonization hypotheses.

High temperature intensifies negative density dependence of fitness in red flour beetles

Competition for food, space, or other depletable resources has strong impacts on the fitness of organisms and can lead to a pattern known as negative density dependence, where fitness decreases as population density increases. Yet, many resources that have strong impacts on fitness are nondepletable (e.g., moisture or temperature). How do these nondepletable resources interact with depletable resources to modify negative density dependence? We tested the hypothesis that negative density dependence is modulated by temperature in red flour beetles and tested the prediction that the strength of negative density dependence should decrease as temperature decreases. We measured the number of eggs laid, offspring development time, and the number of offspring that reached maturity at three temperatures and two food treatment combinations as we simultaneously manipulated adult population density. We demonstrated that low temperatures weaken negative density dependence in the number of eggs laid; this pattern was most evident when food was abundant. Density had no effect on development time, but low temperatures increased development time. The percent of eggs that emerged as adults decreased with both density and temperature and increased with food. Temperature, an abiotic driver, can thus modulate density-dependent processes in ectotherms. Therefore, models of population growth for ectotherms should incorporate the effects of temperature.

Testosterone, body size, and sexual signals predict parasite load in Yarrow’s Spiny Lizards (Sceloporus jarrovii)

Parasite load significantly impacts host health and fitness and may vary substantially among individuals within a population. The immunocompetence handicap hypothesis posits that sexual signals are honest indicators of male quality because they are maintained by testosterone, an immunosuppressant that yields higher parasite loads. Additionally, testosterone may influence parasite load by increasing activity levels. We examined these two hypotheses in a wild population of Yarrow’s Spiny Lizards (Sceloporus jarrovii Cope, 1875) in Arizona. We (i) compared fecal testosterone levels to ectoparasite and haemoparasite loads, (ii) tested if sexual signals (total coloured area, aggression, and head size), locomotor activity, and body size correlated with testosterone levels, and (iii) compared sexual signals, locomotor activity, and body size to parasite load. Ectoparasite loads increased with total coloured area and tended to increase with testosterone, but this latter relationship was only nearly significant. Parasite loads increased with body size. Thus, we found some support for the immunocompetence handicap hypothesis and none for the activity hypothesis. Our results are consistent with an alternative hypothesis that larger individuals have more parasites because they have more surface area and (or) have had longer to accumulate parasites. Future studies should examine the relative contributions of testosterone and glucocorticoids in driving variation in parasite loads.

Spring peepers Pseudacris crucifer modify their call structure in response to noise

Acoustic interference can impede effective communication that is important for survival and reproduction of animals. In response to acoustic interference, some animals can improve signalling efficacy by altering the structure of their signals. In this study, we played artificial noise to 46 male spring peepers Pseudacris crucifer, on their breeding grounds, and tested whether the noise affected the duration, call rate, and peak frequency of their advertisement calls. We used two experimental noise treatments that masked either the high- or low-frequency components of an average advertisement call; this allowed us to evaluate whether frogs adaptively shift the peak frequency of their calls away from both types of interference. Our playback treatments caused spring peepers to produce shorter calls, and the high-frequency noise treatment caused them to lower the frequency of their calls immediately after the noise ceased. Call rate did not change in response to playback. Consistent with previous studies, ambient temperature was inversely related to call duration and positively related to call rate. We conclude that noise affects the structure of spring peeper advertisement calls, and that spring peepers therefore have a mechanism for altering signal structure in response to noise. Future studies should test if other types of noise, such as biotic or anthropogenic noise, have similar effects on call structure, and if the observed changes to call structure enhance or impair communication in noisy environments [Current Zoology 60 (4): 438–448, 2014].

More sires may enhance offspring fitness in Northern Map Turtles (Graptemys geographica)

Sexual selection theory predicts that males should be promiscuous to maximize their reproductive success, while females should be choosy. Yet females of many taxa often produce progeny sired by multiple males, indicating that promiscuity can be important for the reproductive success of females. Promiscuity may enhance the fitness of females if it increases the genetic quality, or the genetic variety, and thus the viability of their offspring. We quantified the number of sires per clutch in a population of Northern Map Turtles (Graptemys geographica (LeSueur, 1817)) in Lake Opinicon, Ontario, Canada, and tested whether the number of sires affects several metrics of viability in hatchlings. Based on the most conservative estimate, at least 71% of clutches in this population are sired by multiple males, but there was no evidence that larger clutches are sired by more males. Clutches sired by more males had higher hatching success and survival, but the differences were not statistically significant. We did not find any effect of the number of sires on hatchling morphology or locomotor performance. Collectively, our results partially support the hypothesis that promiscuity can increase the reproductive success of female Northern Map Turtles.