Both life‐history plasticity and local adaptation will shape range‐wide responses to climate warming in the tundra plant Silene acaulis

Many predictions of how climate change will impact biodiversity have focused on range shifts using species‐wide climate tolerances, an approach that ignores the demographic mechanisms that enable species to attain broad geographic distributions. But these mechanisms matter, as responses to climate change could fundamentally differ depending on the contributions of life‐history plasticity vs. local adaptation to species‐wide climate tolerances. In particular, if local adaptation to climate is strong, populations across a species’ range—not only those at the trailing range edge—could decline sharply with global climate change. Indeed, faster rates of climate change in many high latitude regions could combine with local adaptation to generate sharper declines well away from trailing edges. Combining 15 years of demographic data from field populations across North America with growth chamber warming experiments, we show that growth and survival in a widespread tundra plant show compensatory responses to warming throughout the species’ latitudinal range, buffering overall performance across a range of temperatures. However, populations also differ in their temperature responses, consistent with adaptation to local climate, especially growing season temperature. In particular, warming begins to negatively impact plant growth at cooler temperatures for plants from colder, northern populations than for those from warmer, southern populations, both in the field and in growth chambers. Furthermore, the individuals and maternal families with the fastest growth also have the lowest water use efficiency at all temperatures, suggesting that a trade‐off between growth and water use efficiency could further constrain responses to forecasted warming and drying. Taken together, these results suggest that populations throughout species’ ranges could be at risk of decline with continued climate change, and that the focus on trailing edge populations risks overlooking the largest potential impacts of climate change on species’ abundance and distribution.     

The ecological success of a social parasite increases with manipulation of collective host behaviour

Many parasites alter the behaviour of their host to their own advantage, yet hosts often vary in their susceptibility to manipulation. The ecological and evolutionary implications of such variation can be profound, as resistant host populations may suffer lower parasite pressures than those susceptible to manipulation. To test this prediction, we assessed parasite‐induced aggressive behaviours across 16 populations of two Temnothorax ant species, many of which harbour the slavemaker ant Protomognathus americanus. This social parasite uses its Dufour's gland secretions to manipulate its hosts into attacking nestmates, which may deter defenders away from itself during invasion. We indeed find that colonies that were manipulated into attacking their Dufour‐treated nestmates were less aggressive towards the slavemaker than those that did not show slavemaker‐induced nestmate attack. Slavemakers benefited from altering their hosts’ aggression, as both the likelihood that slavemakers survived host encounters and slavemaker prevalence in ant communities increased with slavemaker‐induced nestmate attack. Finally, we show that Temnothorax longispinosus colonies were more susceptible to manipulation than Temnothorax curvispinosus colonies. This explains why T. curvispinosus colonies responded with more aggression towards invading slavemakers, why they were less likely to let slavemakers escape and why they were less frequently parasitized by the slavemaker than T. longispinosus. Our findings highlight that large‐scale geographic variation in resistance to manipulation can have important implications for the prevalence and host preference of parasites.     

Macrogeographic variation of a pond predator's top-down effects in a common garden environment

Geographic variation in species behavior and life history has been well documented in biology. Species with wide geographic distributions (i.e., across a continent) but small home ranges (i.e., <1 km²) likely experience wide variability in abiotic environments across the entirety of their range, possibly exhibiting strong local adaptation. Understanding variation across a large geographic scale is especially important when considering species that have strong ecological importance, such as keystone species. Yet, few studies have compared the potential cascading ecological effects of a predator with a keystone role in at least part of its range. To understand how keystone ability in pond food webs can vary across a large geographic range, we conducted an artificial pond experiment with a known keystone predator in at least part of its range, the marbled salamander (Ambystoma opacum). To do so, we collected size-matched salamander larvae from three geographically distant populations (>650 km apart) in Ohio, Mississippi, and North Carolina and placed them in mesocosms with a suite of spring breeding amphibian prey species. We observed differential survival of some prey species leading to differences in spring-breeding amphibian diversity among the three predator populations, indicating that keystone predation may vary at a geographic scale. Prey diversity was lowest with predators from northern (Ohio) populations of salamanders. Further understanding of large-scale variability in ecologically important predators and the potential effects of translocating wide-ranging ambystomatid species is needed to direct future conservation efforts and preserve biodiversity.     

The roles of geography and founder effects in promoting host‐associated differentiation in the generalist bogus yucca moth Prodoxus decipiens

There is ample evidence that host shifts in plant‐feeding insects have been instrumental in generating the enormous diversity of insects. Changes in host use can cause host‐associated differentiation (HAD) among populations that may lead to reproductive isolation and eventual speciation. The importance of geography in facilitating this process remains controversial. We examined the geographic context of HAD in the wide‐ranging generalist yucca moth Prodoxus decipiens. Previous work demonstrated HAD among sympatric moth populations feeding on two different Yucca species occurring on the barrier islands of North Carolina, USA. We assessed the genetic structure of P. decipiens across its entire geographic and host range to determine whether HAD is widespread in this generalist herbivore. Population genetic analyses of microsatellite and mtDNA sequence data across the entire range showed genetic structuring with respect to host use and geography. In particular, genetic differentiation was relatively strong between mainland populations and those on the barrier islands of North Carolina. Finer scale analyses, however, among sympatric populations using different host plant species only showed significant clustering based on host use for populations on the barrier islands. Mainland populations did not form population clusters based on host plant use. Reduced genetic diversity in the barrier island populations, especially on the derived host, suggests that founder effects may have been instrumental in facilitating HAD. In general, results suggest that the interplay of local adaptation, geography and demography can determine the tempo of HAD. We argue that future studies should include comprehensive surveys across a wide range of environmental and geographic conditions to elucidate the contribution of various processes to HAD.     

Competitive success of southern populations of Betula pendula and Sorbus aucuparia under simulated southern climate experiment in the subarctic

Global warming has been commonly accepted to facilitate species’ range shifts across latitudes. Cross‐latitudinal transplantations support this; many tree species can well adapt to new geographical areas. However, these studies fail to capture species’ adaptations to new light environment because the experiments were not designed to explicitly separate species’ responses to light and temperature. Here we tested reaction norms of tree seedlings in reciprocal transplantations 1,000 km apart from each other at two latitudes (60°N and 69°N). In contrast to past studies, we exposed our experimental plants to same temperature in both sites (temperature of 60°N growing site is recorded to adjust temperature of 69°N site in real time via Internet connection) while light environment (photoperiod, light quality) remained ambient. Shoot elongation and autumn coloration were studied in seedlings of two deciduous trees (Betula pendula and Sorbus aucuparia), which were expected to respond differently to day length. Sorbus as a member of Rosaceae family was assumed to be indifferent to photoperiod, while Betula responds strongly to day length. We hypothesized that (1) southern and northern populations of both species perform differently; (2) southern populations perform better in both sites; (3) autumn phenology of southern populations may delay in the northern site; (4) and Sorbus aucuparia is less dependent on light environment. According to the hypotheses, shoot elongation of northern population was inherently low in both species. An evolutionary consequence of this may be a competitive success of southern populations under warming climate. Southern population of B. pendula was delayed in autumn coloration, but not in growth cessation. Sorbus aucuparia was less responsive to light environment. The results suggest that light provides selection pressure in range shifts, but the response is species dependent.     

Substantial variation in the timing of pollen production reduces reproductive synchrony between distant populations of Pinus sylvestris L. in Scotland

The ability of a population to genetically adapt to a changing environment is contingent not only on the level of existing genetic variation within that population, but also on the gene flow received from differently adapted populations. Effective pollen‐mediated gene flow among plant populations requires synchrony of flowering. Therefore differences in timing of flowering among genetically divergent populations may reduce their ability to adapt to environmental change. To determine whether gene flow among differently adapted populations of native Scots pine (Pinus sylvestris) in Scotland was restricted by differences in their flowering phenology, we measured timing of pollen release among populations spanning a steep environmental gradient over three consecutive seasons (2014–2016). Results showed that, over a distance of 137 km, there were as many as 15.8 days’ difference among populations for the predicted timing of peak pollen shedding, with the earliest development in the warmer west of the country. There was much variation between years, with the earliest development and least synchrony in the warmest year (2014) and latest development and greatest synchrony in the coolest year (2015). Timing was negatively correlated with results from a common‐garden experiment, indicative of a pattern of countergradient variation. We conclude that the observed differences in reproductive synchrony were sufficient to limit gene flow via pollen between populations of P. sylvestris at opposite ends of the environmental gradient across Scotland. We also hypothesize that continually warming, or asymmetrically warming spring temperatures will decrease reproductive synchrony among pine populations.     

Upward ant distribution shift corresponds with minimum,not maximum,temperature tolerance

Rapid climate change may prompt species distribution shifts upward and poleward, but species movement in itself is not sufficient to establish climate causation. Other dynamics, such as disturbance history, may prompt species distribution shifts resembling those expected from rapid climate change. Links between species distributions, regional climate trends and physiological mechanism are needed to convincingly establish climate‐induced species shifts. We examine a 38‐year shift (1974–2012) in an elevation ecotone between two closely related ant species, Aphaenogaster picea and A. rudis. Even though A. picea and A. rudis are closely related with North American distributions that sometimes overlap, they also exhibit local‐ and regional‐scale differences in temperature requirements so that A. rudis is more southerly and inhabits lower elevations whereas A. picea is more northerly and inhabits high elevations. We find considerable movement by the warm‐habitat species upward in elevation between 1974 and 2012 with A. rudis, replacing the cold‐habitat species, A. picea, along the southern edge of the Appalachian Mountain chain in north Georgia, USA. Concomitant with the distribution shifts, regional mean and maximum temperatures remain steady (1974–2012), but minimum temperatures increase. We collect individuals from the study sites and subject them to thermal tolerance testing in a controlled setting and find that maximum and minimum temperature acclimatization occurs along the elevation gradient in both species, but A. rudis consistently becomes physiologically incapacitated at minimum and maximum temperatures 2 °C higher than A. picea. These results indicate that rising minimum temperatures allow A. rudis to move upward in elevation and displace A. picea. Given that Aphaenogaster ants are the dominant woodland seed dispersers in eastern deciduous forests, and that their thermal tolerances drive distinct differences in temperature‐cued synchrony with early blooming plants, these climate responses not only impact ant‐ant interactions, but might have wide implications for ant‐plant interactions.     

Climate warming will reduce growth and survival of Scots pine except in the far north

Tree growth and survival were assessed in 283 populations of Scots pine ( Pinus sylvestris L.) originating from a broad geographic range and grown at 90 common-garden experimental sites across Europe, and in 101 populations grown at 14 sites in North America. Growth and survival were analysed in response to climatic transfer distance, the difference in mean annual temperature (MAT) between the site and the population origin. Differences among populations at each site, and across sites for regional groups of populations, were related to climate transfer distance, but in opposite ways in the northern vs. southern parts of the species range. Climate transfers equivalent to warming by 1–4 °C markedly increased the survival of populations in northern Europe (≥ 62°N, < 2 °C MAT) and modestly increased height growth ≥ 57°N but decreased survival at < 62°N and modestly decreased height growth at < 54°N latitude in Europe. Thus, even modest climate warming will likely influence Scots pine survival and growth, but in distinct ways in different parts of the species range.     

Comparative <Emphasis Type="Italic">in vitro</Emphasis> germination ecology of <Emphasis Type="Italic">Calopogon tuberosus</Emphasis> var. <Emphasis Type="Italic">tuberosus</Emphasis> (Orchidaceae) across its geographic range

Seed responses to temperature are often essential to the study of germination ecology, but the ecological role of temperature in orchid seed germination remains uncertain. The response of orchid seeds to cold stratification have been studied, but the exact physiological role remains unclear. No studies exist that compare the effects of either cold stratification or temperature on germination among distant populations of the same species. In two separate experiments, the role of temperature (25, 22/11, 27/15, 29/19, 33/24°C) and chilling at 10°C on in vitro seed germination were investigated using distant populations of Calopogon tuberosus var. tuberosus. Cooler temperatures promoted germination of Michigan seeds; warmer temperatures promoted germination of South Carolina and north central Florida seeds. South Florida seed germination was highest under both warm and cool temperatures. More advanced seedling development generally occurred at higher temperatures with the exception of south Florida seedlings, in which the warmest temperature suppressed development. Fluctuating diurnal temperatures were more beneficial for germination compared to constant temperatures. Cold stratification had a positive effect on germination among all populations, but South Carolina seeds required the longest chilling treatments to obtain maximum germination. Results from the cold stratification experiment indicate that a physiological dormancy is present, but the degree of dormancy varies across the species range. The variable responses among populations may indicate ecotypic differentiation.     

Climate adaptation is not enough: warming does not facilitate success of southern tundra plant populations in the high Arctic

Rapidly rising temperatures are expected to cause latitudinal and elevational range shifts as species track their optimal climate north and upward. However, a lack of adaptation to environmental conditions other than climate – for example photoperiod, biotic interactions, or edaphic conditions – might limit the success of immigrants in a new location despite hospitable climatic conditions. Here, we present one of the first direct experimental tests of the hypothesis that warmer temperatures at northern latitudes will confer a fitness advantage to southern immigrants relative to native populations. As rates of warming in the Arctic are more than double the global average, understanding the impacts of warming in Arctic ecosystems is especially urgent. We established experimentally warmed and nonwarmed common garden plots at Alexandra Fiord, Ellesmere Island in the Canadian High Arctic with seeds of two forb species (Oxyria digyna and Papaver radicatum) originating from three to five populations at different latitudes across the Arctic. We found that plants from the local populations generally had higher survival and obtained a greater maximum size than foreign individuals, regardless of warming treatment. Phenological traits varied with latitude of the source population, such that southern populations demonstrated substantially delayed leaf‐out and senescence relative to northern populations. Our results suggest that environmental conditions other than temperature may influence the ability of foreign populations and species to establish at more northerly latitudes as the climate warms, potentially leading to lags in northward range shifts for some species.     

Beyond a warming fingerprint: individualistic biogeographic responses to heterogeneous climate change in California

Understanding recent biogeographic responses to climate change is fundamental for improving our predictions of likely future responses and guiding conservation planning at both local and global scales. Studies of observed biogeographic responses to 20th century climate change have principally examined effects related to ubiquitous increases in temperature – collectively termed a warming fingerprint. Although the importance of changes in other aspects of climate – particularly precipitation and water availability – is widely acknowledged from a theoretical standpoint and supported by paleontological evidence, we lack a practical understanding of how these changes interact with temperature to drive biogeographic responses. Further complicating matters, differences in life history and ecological attributes may lead species to respond differently to the same changes in climate. Here, we examine whether recent biogeographic patterns across California are consistent with a warming fingerprint. We describe how various components of climate have changed regionally in California during the 20th century and review empirical evidence of biogeographic responses to these changes, particularly elevational range shifts. Many responses to climate change do not appear to be consistent with a warming fingerprint, with downslope shifts in elevation being as common as upslope shifts across a number of taxa and many demographic and community responses being inconsistent with upslope shifts. We identify a number of potential direct and indirect mechanisms for these responses, including the influence of aspects of climate change other than temperature (e.g., the shifting seasonal balance of energy and water availability), differences in each taxon's sensitivity to climate change, trophic interactions, and land‐use change. Finally, we highlight the need to move beyond a warming fingerprint in studies of biogeographic responses by considering a more multifaceted view of climate, emphasizing local‐scale effects, and including a priori knowledge of relevant natural history for the taxa and regions under study.     

Cranial variation in geographically widespread dwarf gerbil Gerbillus nanus (Gerbillinae,Rodentia) populations: Isolation by distance versus adaptation to local environments

The dwarf gerbil (Gerbillus nanus) is broadly distributed in Asia, with a range that encompasses altitudinally diverse terrain, including two major mountain ranges. Previous studies have shown this species to be generally varied across its geographic range, both genetically and morphologically. Physical barriers (e.g. mountains) and geographic distance (i.e. isolation by distance [IBD]) are expected to reduce dispersal rates, and consequently could lead to cranial morphological differentiation among populations. Adaptation to local environments is also expected to lead to cranial morphological differentiation among populations. Here, I test these hypotheses by examining variation in cranial shape and size across the geographic distribution of G. nanus using geometric morphometric analysis. Based on a sample of 473 specimens from throughout its distribution, G. nanus populations do not seem to show biologically meaningful variation in cranial shape. Cranial size, on the other hand, did show geographic variation—yet, this variation does not seem to show strong patterns of IBD nor adaptation to local environments, which could indicate that the geographic variation in the cranial size of G. nanus populations may be accounted for by factors unexamined in this study.     

Assessing the sensitivity of bivalve populations to global warming using an individual‐based modelling approach

Climate change exposes benthic species populations in coastal ecosystems to a combination of different stressors (e.g., warming, acidification and eutrophication), threatening the sustainability of the ecological functions they provide. Thermal stress appears to be one of the strongest drivers impacting marine ecosystems, acting across a wide range of scales, from individual metabolic performances to geographic distribution of populations. Accounting for and integrating the response of species functional traits to thermal stress is therefore a necessary step in predicting how populations will respond to the warming expected in coming decades. Here, we developed an individual‐based population model using a mechanistic formulation of metabolic processes within the framework of the dynamic energy budget theory. Through a large number of simulations, we assessed the sensitivity of population growth potential to thermal stress and food conditions based on a climate projection scenario (Representative Concentration Pathway; RCP8.5: no reduction of greenhouse gas emissions). We focused on three bivalve species with contrasting thermal tolerance ranges and distinct distribution ranges along 5,000 km of coastline in the NE Atlantic: the Pacific oyster (Magallana gigas), and two mussel species: Mytilus edulis and Mytilus galloprovincialis. Our results suggest substantial and contrasting changes within species depending on local temperature and food concentration. Reproductive phenology appeared to be a core process driving the responses of the populations, and these patterns were closely related to species thermal tolerances. The nonlinear relationship we found between individual life‐history traits and response at the population level emphasizes the need to consider the interactions resulting from upscaling across different levels of biological organisation. These results underline the importance of a process‐based understanding of benthic population response to seawater warming, which will be necessary for forward planning of resource management and strategies for conservation and adaptation to environmental changes.     

Prairie plant phenology driven more by temperature than moisture in climate manipulations across a latitudinal gradient in the Pacific Northwest,USA

Plant phenology will likely shift with climate change, but how temperature and/or moisture regimes will control phenological responses is not well understood. This is particularly true in Mediterranean climate ecosystems where the warmest temperatures and greatest moisture availability are seasonally asynchronous. We examined plant phenological responses at both the population and community levels to four climate treatments (control, warming, drought, and warming plus additional precipitation) embedded within three prairies across a 520 km latitudinal Mediterranean climate gradient within the Pacific Northwest, USA. At the population level, we monitored flowering and abundances in spring 2017 of eight range‐restricted focal species planted both within and north of their current ranges. At the community level, we used normalized difference vegetation index (NDVI) measured from fall 2016 to summer 2018 to estimate peak live biomass, senescence, seasonal patterns, and growing season length. We found that warming exerted a stronger control than our moisture manipulations on phenology at both the population and community levels. Warming advanced flowering regardless of whether a species was within or beyond its current range. Importantly, many of our focal species had low abundances, particularly in the south, suggesting that establishment, in addition to phenological shifts, may be a strong constraint on their future viability. At the community level, warming advanced the date of peak biomass regardless of site or year. The date of senescence advanced regardless of year for the southern and central sites but only in 2018 for the northern site. Growing season length contracted due to warming at the southern and central sites (~3 weeks) but was unaffected at the northern site. Our results emphasize that future temperature changes may exert strong influence on the timing of a variety of plant phenological events, especially those events that occur when temperature is most limiting, even in seasonally water‐limited Mediterranean ecosystems.     

The geographic structure of morphological variation in eight species of fiddler crabs (Ocypodidae: genus Uca) from the eastern United States and Mexico

Species with larger geographic distributions are more likely to encounter a greater variety of environmental conditions and barriers to gene flow than geographically‐restricted species. Thus, even closely‐related species with similar life‐history strategies might vary in degree and geographic structure of variation if they differ in geographic range size. In the present study, we investigated this using samples collected across the geographic ranges of eight species of fiddler crabs (Crustacea: Uca) from the Atlantic and Gulf coasts of North America. Morphological variation in the carapace was assessed using geometric morphometric analysis of 945 specimens. Although the eight Uca species exhibit different degrees of intraspecific variation, widespread species do not necessarily exhibit more intraspecific or geographic variation in carapace morphology. Instead, species with more intraspecific variation show stronger morphological divergence among populations. This morphological divergence is partly a result of allometric growth coupled with differences in maximum body size among populations. On average, 10% of total within‐species variation is attributable to allometry. Possible drivers of the remaining morphological differences among populations include gene flow mediated by ocean currents and plastic responses to various environmental stimuli, with isolation‐by‐distance playing a less important role. The results obtained indicate that morphological divergence among populations can occur over shorter distances than expected based on dispersal potential. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 248–270.     

Foraging by forest ants under experimental climatic warming: a test at two sites

Climatic warming is altering the behavior of individuals and the composition of communities. However, recent studies have shown that the impact of warming on ectotherms varies geographically: species at warmer sites where environmental temperatures are closer to their upper critical thermal limits are more likely to be negatively impacted by warming than are species inhabiting relatively cooler sites. We used a large‐scale experimental temperature manipulation to warm intact forest ant assemblages in the field and examine the impacts of chronic warming on foraging at a southern (North Carolina) and northern (Massachusetts) site in eastern North America. We examined the influence of temperature on the abundance and recruitment of foragers as well as the number of different species observed foraging. Finally, we examined the relationship between the mean temperature at which a species was found foraging and the critical thermal maximum temperature of that species, relating functional traits to behavior. We found that forager abundance and richness were related to the experimental increase in temperature at the southern site, but not the northern site. Additionally, individual species responded differently to temperature: some species foraged more under warmer conditions, whereas others foraged less. Importantly, these species‐specific responses were related to functional traits of species (at least at the Duke Forest site). Species with higher critical thermal maxima had greater forager densities at higher temperatures than did species with lower critical thermal maxima. Our results indicate that while climatic warming may alter patterns of foraging activity in predictable ways, these shifts vary among species and between sites. More southerly sites and species with lower critical thermal maxima are likely to be at greater risk to ongoing climatic warming.     

Temperature alone does not explain phenological variation of diverse temperate plants under experimental warming

Anthropogenic climate change has altered temperate forest phenology, but how these trends will play out in the future is controversial. We measured the effect of experimental warming of 0.6–5.0 °C on the phenology of a diverse suite of 11 plant species in the deciduous forest understory (Duke Forest, North Carolina, USA) in a relatively warm year (2011) and a colder year (2013). Our primary goal was to dissect how temperature affects timing of spring budburst, flowering, and autumn leaf coloring for functional groups with different growth habits, phenological niches, and xylem anatomy. Warming advanced budburst of six deciduous woody species by 5–15 days and delayed leaf coloring by 18–21 days, resulting in an extension of the growing season by as much as 20–29 days. Spring temperature accumulation was strongly correlated with budburst date, but temperature alone cannot explain the diverse budburst responses observed among plant functional types. Ring‐porous trees showed a consistent temperature response pattern across years, suggesting these species are sensitive to photoperiod. Conversely, diffuse‐porous species responded differently between years, suggesting winter chilling may be more important in regulating budburst. Budburst of the ring‐porous Quercus alba responded nonlinearly to warming, suggesting evolutionary constraints may limit changes in phenology, and therefore productivity, in the future. Warming caused a divergence in flowering times among species in the forest community, resulting in a longer flowering season by 10‐16 days. Temperature was a good predictor of flowering for only four of the seven species studied here. Observations of interannual temperature variability overpredicted flowering responses in spring‐blooming species, relative to our warming experiment, and did not consistently predict even the direction of flowering shifts. Experiments that push temperatures beyond historic variation are indispensable for improving predictions of future changes in phenology.     

Coupling of respiration, nitrogen, and sugars underlies convergent temperature acclimation in Pinus banksiana across wide-ranging sites and populations

Patterns and mechanisms of short‐term temperature acclimation and long‐term climatic adaptation of respiration among intraspecific populations are poorly understood, but both are potentially important in constraining respiratory carbon flux to climate warming across large geographic scales, as well as influencing the metabolic fitness of populations. Herein we report on leaf dark respiration of 33‐year‐old trees of jack pine (Pinus banksiana Lamb.) grown in three contrasting North American common gardens (0.9, 4.6, and 7.9 °C, mean annual temperature) comprised of identical populations of wide‐ranging geographic origins. We tested whether respiration rates in this evergreen conifer acclimate to prevailing ambient air temperatures and differ among populations. At each of the common gardens, observed population differences in respiration rates measured at a standard temperature (20 °C) were comparatively small and largely unrelated to climate of seed‐source origin. In contrast, respiration in all populations exhibited seasonal acclimation at all sites. Specific respiration rates at 20 °C inversely tracked seasonal variation in ambient air temperature, increasing with cooler temperatures in fall and declining with warmer temperatures in spring and summer. Such responses were similar among populations and sites, thus providing a general predictive equation regarding temperature acclimation of respiration for the species. Temperature acclimation was associated with variation in nitrogen (N) and soluble carbohydrate concentrations, supporting a joint enzyme and substrate‐based model of respiratory acclimation. Regression analyses revealed convergent relationships between respiration and the combination of needle N and soluble carbohydrate concentrations and between N‐based respiration (R_N, μmol mol N^{? 1} s^{? 1}) and soluble carbohydrate concentrations, providing evidence for general predictive relationships across geographically diverse populations, seasons, and sites. Overall, these findings demonstrate that seasonal acclimation of respiration modulates rates of foliar respiratory carbon flux in a widely distributed evergreen species, and does so in a predictable way. Genetic differences in specific respiration rate appear less important than temperature acclimation in downregulating respiratory carbon fluxes with climate warming across wide‐ranging sites.     

Variable evolutionary response to regional climate change in a polymorphic species

The evolutionary response to regional and global climate change may vary in widespread polymorphic species, so predicting future genetic responses will require careful tracking of genetic variability in local populations. We surveyed chromosomal inversion polymorphisms in 25 populations of Drosophila robusta, many of which have been sampled repeatedly starting in the 1940s, 50s, and 60s up until 2007, across its range in the USA. Frequencies of some northerly, or cold‐adapted, gene arrangements have declined in the face of increasing temperatures, whereas frequencies of several southern, or warm‐adapted, gene arrangements were positively correlated with increasing temperature changes. Over a finer geographic scale, populations from the west‐central part of the species range from the Ozark Plateau, Ouachita mountains, and eastern Oklahoma showed genetic differentiation between south‐central Ozark and western Ozark/Ouachita regions that has persisted in the face of recent shifts in gene arrangement frequencies. Overall, populations of D. robusta exhibited dynamic genetic changes over time, with some populations shifting chromosome frequencies in just 10–15 years. Some temporal genetic shifts were widespread and significantly correlated with temperature increases, but regions of the genome marked by different gene arrangements have responded in different sections of the species range. In some parts of the species range, chromosome frequencies shifted but were not associated with changing temperatures, showed little or no temporal change, or temporal shifts stopped for temperature sensitive gene arrangements near fixation. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 702–718.     

Adaptation to host plants may prevent rapid insect responses to climate change

We must consider the role of multitrophic interactions when examining species' responses to climate change. Many plant species, particularly trees, are limited in their ability to shift their geographic ranges quickly under climate change. Consequently, for herbivorous insects, geographic mosaics of host plant specialization could prohibit range shifts and adaptation when insects become separated from suitable host plants. In this study, we examined larval growth and survival of an oak specialist butterfly (Erynnis propertius) on different oaks (Quercus spp.) that occur across its range to determine if individuals can switch host plants if they move into new areas under climate change. Individuals from Oregon and northern California, USA that feed on Q. garryana and Q. kelloggii in the field experienced increased mortality on Q. agrifolia, a southern species with low nutrient content. In contrast, populations from southern California that normally feed on Q. agrifolia performed well on Q. agrifolia and Q. garryana and poorly on the northern, high elevation Q. kelloggii. Therefore, colonization of southern E. propertius in higher elevations and some northern locales may be prohibited under climate change but latitudinal shifts to Q. garryana may be possible. Where shifts are precluded due to maladaptation to hosts, populations may not accrue warm‐adapted genotypes. Our study suggests that, when interacting species experience asynchronous range shifts, historical local adaptation may preclude populations from colonizing new locales under climate change.