Abstract
Understanding the potential of animals to quickly respond to changing temperatures is imperative for predicting the effects of climate change on biodiversity. Ectotherms, such as insects, use behavioural thermoregulation to keep their body temperature within suitable limits. Behavioural thermoregulation may be particularly important at warm margins of species occurrence where populations are sensitive to increasing air temperatures. In the field, we studied thermal requirements and behavioural thermoregulation by microhabitat choice and by switching among daily activities in low-altitude populations of the Satyrinae butterflies Erebia aethiops, E. euryale and E. medusa. We compared the relationship of individual body temperature with air and microhabitat temperatures for the low-altitude Erebia species to our data on seven mountain species, including a high-altitude population of E. euryale, studied in the Alps. E. aethiops and the low-altitude population of E. euryale kept lower body temperatures than the other species and showed signs of overheating. Adults of a lowland species E. medusa seemed well adapted to warm climate of a subxerotherm locality. Temperature-dependence of different daily activities also differed between the three lowland populations and the mountain species. Overall, our results suggest that lowland species and populations of Erebia butterflies are likely more severely threatened by ongoing climate changes than mountain species. Because of the ability of butterflies to actively search for appropriate microclimate and different requirements of individual species, we highlight the importance of sustaining habitat heterogeneity to protect individual species and entire assemblages.
Introduction
Ongoing climate changes induce range shifts of many animals and plants [1, 2], however species responses to climate change are individualistic. Animals diversely adjust their behaviour [3, 4], phenology [5], acclimate [6] or adapt by rapid evolutionary changes [3, 7, 8]. These adaptive responses to environmental changes together contribute to the demarcation of current species distribution ranges and also induce diversification. Selective pressure of large environmental changes leads to shifts of allele frequencies of genes responsible for physiological functions [7] and creates a phylogenetic signal in genus-level phylogenies [9, 10].
At short time scales, behavioural plasticity of ectotherms enables them to keep their body temperature at the optimal level and thus to optimize functioning of their physiological processes [4]. Behavioural thermoregulation is mainly represented by changes in timing of daily activities or exploration of various (micro)habitats [11–13]. Especially, the ability to use locally suitable microhabitats facilitates species survival under ongoing climate change [4]. Ectotherms search for warmer microclimate at the cold margins [12, 14] and decrease activity or search for shade at the warm margins of occurrence [15–18]. The comparison of species responses at contrasting climatic range margins, such as low-vs. high-altitude margins, may empower effective targeting of conservation activities especially in declining species with limited potential for range shift [2, 19, 20].
Despite the great behavioural plasticity of many species, physiological constraints can block behavioural compensation of climate change. For example, tropical lizards of forest interior suffer from higher risk of overheating than their open-habitat congeners [21]. Under climate warming scenario, open-habitat species have a potential to explore novel habitat types in the forest interior by adjusting their microhabitat use while forest-dwellers have a little chance of doing so because they already occupy the coolest available microhabitats [21]. Despite many obvious advantages of behavioural plasticity as a fast way to respond to environmental changes [4], behavioural thermoregulation could also limit physiological adaptation, which is necessary for species’ long-term survival [6, 22, 23]. This so called Bogert effect has not yet been conclusively proven, but represents an important possibility with implications for predicting climate change effects.
Organisms living in high altitudes were among the first to attract considerable attention to the issues of species survival under climate change because of apparent range shifts along the altitudinal gradient [1, 24, 25]. However, recent studies report that lowland fauna seems to be even more sensitive to ongoing climate change then mountain one. Detailed studies of internal traits such as immune system [26], thermoregulation [21] or thermal limits [27] surprisingly report higher sensitivity of lowland species to increasing temperatures. Moreover, also extrinsic factors such as existence of extremely diverse (micro)habitats and topographies [2, 14, 28] or feasibility of uphill shifts along the altitudinal gradient [2], support long-term survival of species in mountains. On the contrary, lowlands provide more homogeneous environment, in addition, they are fully exposed to human activities such as agriculture, forestry or urbanization. In concordance, large comparative study by [2] showed that mountain assemblages are more stable, i.e. less vulnerable, than lowland ones in relation to climate change.
Here, we focus on thermal ecology and microclimate utilisation at high-and low-altitude margins of occurrence in adult butterflies of the genus Erebia. Alpine Erebia species are well adapted to extreme high-altitude environment, where they are able to maximize activity during short periods of favourable weather and they do not seem to be at risk of overheating in a warming environment [14]. However, the situation in aberrant lowland species of this mostly mountain genus is not known. Thus, we examined thermoregulatory strategies in adults of two lowland species at upper thermal margins of their occurrence and of a low-altitude mountain population of a montane-belt species. We compared our findings with data on seven alpine species reported in [14]. We report considerable differences in body temperatures, microhabitat utilisation, and contrasting temperature-dependence of different activities between low-and high-altitude butterflies. We discuss the role of behavioural thermoregulation for coping with ongoing climate change and conclude by a prediction that lowland species of Erebia butterflies will face more serious threat than their alpine relatives.
Materials and Methods
Study group and study sites
The genus Erebia Dalman, 1816 is a popular group in studies of eco-physiological adaptations [14, 29] and biogeography [30–32] as well a subject of increasing interest from the conservation perspective [14, 18, 33–36]. In our study, we compared thermoregulation of seven alpine species occurring at high altitudes in European Alps (see [14] for more details) with thermoregulation of a low-altitude population of a mountain species E. euryale (Esper, 1805) and two aberrant lowland species, E. aethiops (Esper, 1777) and E. medusa (Fabricius, 1787).
Mountain species
The seven alpine species Erebia alberganus (Prunner, 1798), E. euryale (Esper, 1805), E. ligea (Linnaeus, 1758), E. melampus (Fuessly, 1775), E. montana (de Prunner, 1798), E. pandrose (Borkhausen, 1788) and E. cassioides (Reiner and Hohenwarth, 1792) were studied in Austrian Alps, Tirol close to the town of Sölden in an altitude 1500-1800 m a.s.l. (see [14] for more details). All these species occur in montane and alpine vegetation belts [37]. Another, low-altitude population of E. euryale was studied in Šumava Mts., Czech Republic, close to Borová Lada village, in the area of a former village Zahrádky (13.68032°E,48.97362°N, altitude 930 m a.s.l.). E. euryale inhabits clearings and road margins within spruce forest in the area and was frequently observed nectaring on nearby pastures. The species E. euryale was thus represented by two populations; by a high-altitude population from Austrian Alps (E. euryale-Alps) and by a low-altitude population from Šumava Mts., Czech Republic (E. euryale-CZ).
Lowland species
E. aethiops and E. medusa inhabit a rather wide range of altitudes and occur also in mountains and sub-alpine zone [37]. Both lowland species originated during Miocene diversification of a European clade of the genus Erebia and they are members of a phylogenetically distinct species group [32]. Their conservation status is Least Concern for Europe [38], but both species experienced local declines throughout their ranges [39, 40] attributed to habitat alteration [18, 36]. Moreover, both species are hypothesized to be negatively affected by ongoing climate change [17, 41]. We studied their lowland populations in an ex-military area Vyšný in the vicinity of a town Český Krumlov, SW Czech Republic (48°49’N, 14°1’E, altitude 550 m). The area is formed by a mosaic of dry grasslands, shrubs and woodlands. Both species co-occur in this subxerotherm area, probably on their upper thermal limits. E. aethiops (flight period: mid-June to August) is a woodland species, which inhabits forest edges, small grassland patches and sparse woodlands within the area [17, 18], while E. medusa (flight period: May to mid-July) is found in more open habitats - xeric grasslands with scattered shrubs.
Measurements of body, microhabitat and air temperatures
Butterfly body temperature Tb was measured by a hypodermic micro-needle probe (0.3 mm in diameter) within 5 seconds after capture and values were recorded on Physitemp thermometer (model BAT-12) during August 2010 (E. aethiops), May 2012 (E.medusa), July 2012 (E. aethiops, E. euryale-CZ) and August 2012 (E. euryale-CZ). The alpine species were measured during their flight periods in 2010 and 2011 (see [14]). Butterflies were collected by a net during random walks within the study area during the entire daytime activity period (between 9 a.m. and 6 p.m.). During a measurement, a butterfly was shaded and the microprobe was inserted into its thorax. The same thermometer was used to measure microclimate Tm and air Ta temperatures. Microclimate temperature Tm was measured immediately after Tb measurement at the place where the butterfly was located before the capture (approximately 3 mm above substrate in the case of sitting or nectaring butterflies). Air temperature Ta was measured at 1.5 m above ground by a shaded thermometer. Further, we classified individual behaviour prior to capture into three categories: sitting, nectaring and flight. All data are on Czech butterflies are available in Supplementary File S1, data from Austria are available in [14] (Appendix A).
Data analyses
The aim of our analyses was to compare thermoregulation of related butterflies occurring in mountains and in lowlands. All analyses were conducted in R 3.0.2 [42]. First, we tested the dependence of body temperature Tb on microhabitat Tm and air Ta temperatures using Generalized Additive Models (GAMs) with cubic splines and maximal complexity of the fitted relationship set to k = 5 d.f. in mgcv 1.8-4 package for R [43]. The two relationships (Tb ∼ Ta and Tb ∼ Tm) were fitted for individual species (lowland and alpine populations of E. euryale were analysed separately). Next, to obtain standardized measures of species thermoregulatory abilities, we defined two related variables: body-to-air temperature excess Tb − Ta and body-to-microhabitat temperature excess Tb − Tm. Then, we modelled the dependence of Tb − Ta and Tm − Ta on centered values of Ta and Tm, respectively, by GAMs, again separately for the two E. euryale populations and the two lowland species. The values of Ta and Tm were centered by subtracting the mean values of Ta and Tm, respectively, to ensure biologically meaningful intercepts in the analyses (without centering, the intercepts would show the air or microhabitat temperature excess when Ta or Tm, respectively, is zero) and to remove possible slope–intercept correlation (see [14] for more details). Data on alpine species reported by [14] were re-analysed the same way to facilitate comparison with the lowland species (original conclusions of [14] were not affected).
We also searched for differences in active behavioural thermoregulation between lowland and mountain species. We estimated the difference between microhabitat and air temperatures Tm–Ta for settling and nectaring individuals (i.e. potentially actively thermoregulating) of each low-altitude and mountain species (separately for the two populations of E. euryale). Then, we used t-tests to test whether lowland species and E. euryale population also search for similarly warm microclimates as the alpine species [14].
Last, we tested how the proportion of settling, nectaring and flying individuals for individual species depends on air temperatures Ta using GAMs with quasibinomial distribution. This analysis was conducted for the three types of behaviour and all lowland and mountain species/populations separately.
Results
The two lowland species, E. medusa and E. aethiops, experienced higher maximal and higher minimal air temperatures Ta than the seven mountain species studied (Fig. 1, Fig. 2A, Table 1). Low-altitude population of E. euryale-CZ experienced similar maximal air temperatures Ta but ca 5°C higher minimal air temperatures Ta compared to the alpine population of E. euryale (Fig. 2A). In spite of these differences in experienced air temperatures Ta, experienced maximal microhabitat temperatures Tm did not differ in species across different altitudes (Fig. 2B). Thus, alpine species were able to detect warm microclimate to compensate for the experienced low air temperatures. Minimal microhabitat temperatures Tm were higher in the lowland species corresponding to generally warmer lowland environment. Body temperatures Tb increased approximately linearly with increasing air temperatures Ta as well as with increasing microhabitat temperatures Tm in all species (Fig. 1, Fig. 2A, 2B, Table 2). However, low altitude population of E. euryale-CZ and E. aethiops kept lower body temperatures Tb at similar air temperatures Ta than all other species, i.e. species from the Alps and also lowland E. medusa (Fig. 2A, 2B). Especially E. aethiops kept its body temperature only several °C above the air temperature Ta and had Tb almost equal to Ta at high Ta values (Fig. 1).
The inter-species thermoregulatory differences become more obvious if we compare - the dependence of body-to-air temperature excess Tb − Ta and body-to-microhabitat temperature excess Tb − Tm on air Ta and microhabitat Tm temperatures, respectively. The body-to-air temperature excess Tb–Ta at similar air temperatures Ta was lower in lowland E. aethiops and E. euryale-CZ compared to species from the Alps and lowland medusa (Fig. 2C). This suggests that the lowland population of E. euryale-CZ and E. aethiops had lower optima of body temperature and heated up less effectively, i.e. that they had lower tendency to heat up at given air temperatures Ta than the other species. Contrary, lowland E. medusa had thermoregulatory characteristics similar to the alpine species. Dependence of the body-to-air temperature excess Tb–Ta on air temperature Ta was nearly linear in species from the Alps and in E. medusa (Fig. 2). These species increased their body temperatures more at low than at high air temperatures, which suggest active thermoregulation by microclimate choice or body posture adjustment under low air temperatures. In E. euryale-CZ, the body-to-air temperature excess decreased with growing temperature linearly, but at high air temperatures, we observed abrupt enhancement of the body-to-air temperature excess; this might be a sign of overheating but the number of observations at high temperatures was rather low. In E. aethiops, we observed a hump-shaped dependence of the body-to-air temperature excess on air temperature. It slowly increased its body-to-air temperature excess Tb − Ta in a range of air temperatures 15-20° C and, after reaching the optimum around Ta = 21° C, its body-to-air temperature excess Tb – Ta decreased again (Fig. 2C). It seems, that E. aethiops thus has a narrow temperature range for activity compared to the other species.
Similarly as we observed for the dependence of the air temperature excess Tb − Ta on air temperatures Ta, E. aethiops showed a hump-shaped dependence of its microhabitat temperature excess Tb − Tm on microhabitat temperatures Tm it experienced. The relationship between Tb − Tm and Tm in the remaining species also paralleled our findings about the dependence of Tb − Ta on Ta (Fig. 1, Fig. 2, Table 2), which shows that the relationships reported did not arise from temperature-dependent microhabitat choice.
Regarding the thermoregulatory behaviour during sitting or nectaring, E. aethiops and the low-altitude population of E. euryale-CZ did not search for warm microclimates as much as the other species did (Fig. 3, Table 3). In E. medusa, the difference between microhabitat and air temperatures Tm − Ta during sitting and nectaring was more similar to the alpine species. Moreover, E. medusa explored microhabitat temperatures up to 32 ° C (Fig. 3C) and thus, it has the highest thermal tolerance to high temperatures from all species studied. Except of E. aethiops, Erebia species searched for warmer microclimates then ambient air temperatures, i.e. Tm > Ta (Fig. 3). E. aethiops explored microhabitats which were similarly warm as the air (Fig. 3B), suggesting heat-avoidance behaviour. High-altitude population of E. euryale searched for microhabitats on average 2.00 ° C warmer than the air, while its low-altitude population was found in microhabitats on average only 0.64 ° C warmer then the air.
Proportion of settling, nectaring or flying individuals was dependent on air temperature Ta at least for one of these behavioural categories in E. aethiops, E. euryale-Alps, E. ligea, E. montana and E. medusa (Table 3, Fig. 4). Settling (i.e. various forms of basking behavior and resting) was the most frequent behaviour under low air temperatures (Fig. 4). Frequency of nectaring increased with increasing air temperatures in species from the Alps, but displayed hump shape in E. aethiops and E. medusa. Frequency of flying was nearly constant in all species, with the exception of E. aethiops which displayed increase of the proportion of flying individuals with increasing air temperature.
Discussion
Thermoregulatory strategies at thermal margins
Behaviour has a potential to modify physiological responses to evolutionary pressures such as ongoing changes of climate [6, 44, 45]. Our results demonstrate that E. aethiops and E. medusa, two aberrant butterfly species of mostly cold-dwelling butterfly genus, diversified in their thermoregulatory strategies and also in their tolerance to high-temperatures, in E. medusa, or the lack of it, in E. aethiops (Fig. 2). We hypothesize that this differentiation of thermoregulatory strategies was driven by contrasting habitat preferences of the two lowland Erebia species, similarly as has been observed for Mediterranean cicadas [46, 47], tropical lizards [21] or mountain species of the genus Erebia [14]. E. aethiops, which inhabits heterogeneous forest-steppe environment [18], did not actively enhance its body temperature and suffered by overheating (see also [17]). Contrary, E. medusa, a grassland species, flourished in warm climate of the subxerotherm locality. It effectively heated up under low air temperatures and linearly enhanced its body temperature up to 39°C; i.e., higher than body temperatures of all its congeners we studied (see [14]). These differences illustrate that species with ancestral cold-climate preference [32] have the potential to adjust to environmental conditions in warm lowlands and that behavioural traits, such as habitat use, determine species thermal limits and affect their future perspectives under predicted climate warming.
Small ectotherms have to rely on behaviour such as shade seeking or decrease of activity to avoid overheating at their thermal margins [4]. E. aethiops, the species suffering by overheating, was frequently observed flying in the shadow of trees during the warmest part of the day [17]. In congruence, it was the only one of all Erebia species studied which showed a lack of selectivity for microhabitats warmer than air temperature (Fig. 3). This suggests heat-avoidance behaviour in E. aethiops. Furthermore, E. aethiops was the only Erebia species in which the proportion of flying individuals increased at the highest air temperatures (Fig. 4). We argue that this behaviour represents a tendency to actively decrease its body temperature by convective cooling in the shadow, which follows e.g. nectaring on warm sun-exposed flowers. In other words, its individuals probably had to fly more frequently between warm (to search for nectar sources or mates) and cold microhabitats (to decrease their body temperatures). During the lowest air temperatures experienced (15-20°C), E. aethiops mainly settled on vegetation. These air temperature are suitable for activity of the other Erebia species; alpine relatives were found in flight at temperatures as low as 12°C [14]. We argue, that settling during temperatures potentially suitable for activity was conditioned by resting in a colder microclimate under shrubs and trees [17] and by the absence of behavioural enhancement of body temperature in this species. E. aethiops started to nectar at mid-range of experienced temperatures (20-25°C) in congruence to the temperatures in which other Erebia species maximized their nectaring activities. However, both lowland species experienced much higher maximal temperatures (around 30°C) than their mountain congeners (Fig. 4). The extreme temperatures obviously limited nectaring of both lowland species. E. aethiops reached the peak of its nectaring activity around 24°C and E. medusa around 26°C; again, this difference between the lowland species should reflect their different thermal tolerances. The decrease of nectaring activities of the lowland species during the warmest periods of the day could be caused by desiccation of nectar or by the need of the butterflies to prevent overheating. Thus, the timing of diurnal activities contributes to the Erebia thermoregulation together with microhabitat choice [17, 48] and facilitates species survival on their range margins.
Behavioural thermoregulation and adaptation to climate changes
Long-term persistence in changing climate requires adaptation; i.e. adjustments of physiological mechanisms responsible for thermal tolerance of species. It is possible that behavioural thermoregulation, which is a potent short-term solution for dealing with a changing climate, constrains the adaptive potential of such plastic species [6, 22, 23]. Buckley et al. [6] provided evidence of this, so called Bogert effect, in lizards where they showed that populations from different parts of the lizard’s distribution have conserved preferred body temperature and thermal minima and maxima. This suggests that the lizards have limited potential to physiologically adapt to climate changes because their efficient behavioural thermoregulation buffers the selective pressure [6]. Erebia butterflies also thermoregulate behaviourally but their thermoregulatory strategies and preferred body temperatures are not conserved according to our data; i.e. individual species have different thermoregulatory requirements and we found no support for the Bogert effect in Erebia. This is indicative of high potential for evolutionary responses to climate change within the genus. In their detailed study of Anolis lizards, Munoz et al. [44] found that cold tolerance evolves faster than heat tolerance because selection on upper thermal limits is weakened by active thermoregulation more than selection on lower thermal limits. A possible explanation for the lack of conservatism of thermal ecology of Erebia species is that they need to feed on nectar and flowering plants are typically abundant in open sunny habitats which offer limited possibility for behavioural thermoregulation. This should create a selective pressure on the evolution of tolerance to higher temperatures in a warming climate. Moreover, butterflies of the genus Erebia conserved their extraordinary diversity in unstable temperate areas during extreme climatic fluctuations of Pleistocene [32] and thus, evolutionary plasticity of their thermal niches is a plausible mechanism facilitating their long-term survival.
Changing climatic conditions affect phenotypes of local populations [49] or higher taxonomical units [10, 21]. In Erebia butterflies, thermoregulation was affected also by local adjustments of geographically segregated populations. We noticed differences in thermal niches among the two populations of E. euryale. The low-altitude population E. euryale-CZ (900m a.s.l.) kept lower body temperatures Tb than the high-altitude population E. euryale-Alps (1800m a.s.l.) (Fig. 2). This suggest, that the lowland population is more “lazy” in its effort to heat up and waits with its activities for periods of the day with optimal air temperature. In a similar case in grasshoppers, Samietz et al. [50] found that individuals increased their body temperatures via mobility and basking more at higher altitudes and demonstrated that this was due to local adaptation. The observed difference between E. euryale populations could be caused by local adaptation or by phenotypic plasticity. Transplant or laboratory experiments are necessary to resolve the relative contributions of these interacting factors [50, 51]. Phenotypic plasticity of thermoregulaory mechanisms should facilitate species survival in unstable conditions, such as in temperate mountains during climatic oscillations, but on the other hand, it could block speciation and evolution of the thermal niche [6]. Local adaptation contributed to the evolution of thermoregulatory specialization in ectotherms such as lizards [21, 44, 52], grasshoppers [50] or butterflies [53, 54]. It is likely that this mechanism operates also in Erebia. It is important to note that main selective agents driving the evolution of thermoregulatory strategies are temperature extremes, rather than long-term means. In their review, [55] concluded that maximal temperatures seem to be more limiting than minimal temperatures in terrestrial ectotherms. In congruence, we noticed limitation by high ambient temperatures in E. aethiops and E. euryale adults. However, the effect of high temperatures may differ across developmental stages. The overwintering stages, larvae, are more likely to be affected by other factors associated with climate change such as changes of snow cover [29, 35]. The role of local adaptation and plasticity across all developmental stages [56] will be an important focus of future studies.
Habitat heterogeneity and species survival in a changing climate
On the example of Erebia butterflies we demonstrated the potential of behaviour for dealing with climatic changes. Erebia butterflies kept their thermal optima mainly by shifts in microhabitat exploration, but also by shifts in timing of daily activities. However, their survival under changing climate is primarily determined by availability of various microhabitats providing variety of microclimates. In lowland butterflies, habitat heterogeneity provided colder microclimates, whereas mountain species explored warmer microhabitats to enhance their body temperature [14]. Woodland resident E. aethiops [18], is more endangered by a combination of landscape homogenization and climate change in comparison to alpine species or E. medusa. It seems plausible, that woodland species are generally more sensitive to high temperatures because of their lower thermal optima [14] and lack of opportunities for adjusting to warming of their environment behaviourally by microhabitat shifts, e.g. by more intensive shade seeking [21]. It could be expected that under climate warming, E. medusa would retract to woodland edges and to woodland patches which provide shade. Indeed, the species inhabits these habitats in some parts of its range [39]. It remains to be tested whether local habitat preferences correlate with local climate.
Because of its heat tolerance and potential for habitat shifts, E. medusa will likely be less endangered by overheating during ongoing climatic change than E. aethiops. Nevertheless, our study focused on thermal strategies of adult stages, but the knowledge of dormant stages (in butterflies represented by larvae, pupae or eggs), which can not behaviourally thermoregulate, is necessary to reveal main selective pressures [45, 57, 58]. Still, the behaviour of active stages could predetermine environmental conditions experienced by dormant stages. For example, in a climate-sensitive butterfly Euphydryas editha, different populations experienced diverse thermal environments because of differences in adult phenology and egg placement by ovipositioning females [13]. Similarly, in Erebia butterflies the location of oviposition sites corresponding to female habitat choice can predetermine the conditions experienced by overwintering larvae. To target conservation activities for particular species, detailed knowledge of requirements of all developmental stages is necessary [56].
Habitat heterogeneity is a key to successful conservation of individual species and entire communities, because it maximises the chance of ecthoterms to find suitable microclimate and also to obtain resources needed for their activities. Lowland species are at risk from high temperatures, but they could shift into more shaded places in forests. However, the structure of forests in intensively used European landscapes often does not provide the required resources because the forests are too closed [18]. Because of species-specific responses to changes of environmental conditions [1, 19], habitat heterogeneity should mitigate the effect of climate change at the level of whole communities. Thus, active management supporting habitat heterogeneity could facilitate species survival under climate change [59]. Whereas mountain landscape provides heterogeneity by its rugged terrain, especially in their subalpine and alpine zones, lowlands are more prone to landscape homogenization [60], both because of more flat terrain and higher human pressure. Increased conservation management efforts should thus focus on low-altitude margins of species occurrence in montane zones and lowland areas.
Supporting Information
S1 Text
Raw data
The file contains measurements of body temperature, air temperature, microhabitat temperature, and behaviour prior to capture of Erebia aethiops, E. euryale, and E. medusa studied in the Czech Republic.
Acknowledgments
We would like to thank D. Novotný and J. Peltanová for help with data collection in the field and to M. Konvička for inspiring discussions on butterfly ecology and conservation. Both JK and IK are supported by the Czech Science Foundation (project GP14-10035P).
Footnotes
↵* irena.slamova{at}gmail.com