Tropical organisms colonizing temperate environments face reduced average temperatures and dramatic thermal fluctuations. Theoretical models postulate that thermal specialization should be favored either when little environmental variation is experienced within generations or when among-generation variation is small relative to within-generation variation. To test these predictions, we studied six temperate species of damselflies differing in latitudinal distribution. We developed a computer model simulating how organisms experience environmental variation (accounting for diapause and voltinism) and performed a laboratory experiment assaying thermal sensitivities of growth rates. The computer model showed opposing latitudinal trends in among- and within-generation thermal variability: within-generation thermal variability decreased toward higher latitudes, whereas relative levels of among-generation thermal variability peaked at midlatitudes (where a shift in voltinism occurred). The growth experiment showed that low-latitude species were more thermally generalized than mid- and high-latitude species, supporting the prediction that generalists are favored under high levels of within-generation variation. Northern species had steeper, near-exponential reaction norms suggestive of thermal specialization. However, they had strikingly high thermal optima and grew very slowly over most of the thermal range they are expected to experience in the field. This observation is at present difficult to explain. These results highlight the importance of considering interactions between life history and environmental variation when deriving expectations of thermal adaptation.

Although a growing number of studies have documented the evolution of adult dispersal-related traits at the range edge of poleward-expanding species, we know little about evolutionary changes in immune function or traits expressed by nondispersing larvae. We investigated differentiation in larval (growth and development) and adult traits (immune function and flight-related traits) between replicated core and edge populations of the poleward-moving damselfly Coenagrion scitulum. These traits were measured on individuals reared in a common garden experiment at two different food levels, as allocation trade-offs may be easier to detect under energy shortage. Edge individuals had a faster larval life history (growth and development rates), a higher adult immune function and a nearly significant higher relative flight muscle mass. Most of the differentiation between core and edge populations remained and edge populations had a higher relative flight muscle mass when corrected for latitude-specific thermal regimes, and hence could likely be attributed to the range expansion process per se. We here for the first time document a higher immune function in individuals at the expansion front of a poleward-expanding species and documented the rarely investigated evolution of faster life histories during range expansion. The rapid multivariate evolution in these ecological relevant traits between edge and core populations is expected to translate into changed ecological interactions and therefore has the potential to generate novel eco-evolutionary dynamics at the expansion front.

Genetic differentiation and phenotypic plasticity in growth rates along latitudinal gradients may benefit our understanding of latitudinal compensating mechanisms in life history patterns. Here we explore latitudinal compensatory growth mechanisms with respect to photoperiod in northern and southern populations of two damselfly species, Coenagrion puella and C. pulchellum. In addition we compared size of field‐collected adults from southern and northern populations. Eggs from females in copulating tandems were collected at two or three localities for each species in each geographic region. Eggs were transported to the laboratory and the experiment started when the eggs hatched. The role of photoperiod on the expression of larval growth rate was evaluated under controlled laboratory conditions. Both species had lower growth rate when reared in the northern photoperiod, which is counter to expectations if species use photoperiodic cues to trigger compensatory growth. Instead, both species displayed countergradient variation in growth rates, which probably enable northern populations to compensate for the shorter growth season in the north. The smaller size of field‐collected adults from northern populations also supports the view that these species compensate for the shorter growth season by investing in growth and development but accomplish this at the expense of decreased final size.

The increase in temperature as consequence of the recent global warming has been reported to generate new ice-free areas in the Antarctic continent, propitiating the colonization and spread of plant populations. Consequently, antarctic vascular plants have been observed extending their southern distribution. But as the environmental conditions toward southern localities are progressively far apart from these species' physiological optimum, the colonization of new sites and ecophysiological responses could be decreased. However, if processes of local adaptation are the main cause of the observed southern expansion, those populations could appear constrained to respond positively to the expected global warming. Using individuals from the southern tip of South America, the South Shetland Islands and the Antarctic Peninsula, we assess with a long term experiment (3 years) under controlled conditions if the responsiveness of Colobanthus quitensis populations to the expected global warming, is related with their different foliar traits and photoprotective mechanisms along their latitudinal gradient. In addition, we tested if the release of the stress condition by the global warming in theses cold environments increase the ecophysiological performance. For this, we describe the latitudinal pattern of net photosynthetic capacity, biomass accumulation, and number of flowers under current and future temperatures-by warming-respective to each site of origin after three growing seasons. Overall, was showed a clinal trend was found in the foliar traits and photoprotective mechanisms in the evaluated C. quitensis populations. On the other hand, an asymmetric response to warming was observed for southern populations in all ecophysiological traits evaluated, suggesting that low temperature is limiting the performance of C. quitensis populations, mainly in those from southern. Our results suggest that under a global warming scenario those plant populations that inhabiting cold zones at high latitudes could be improved in their ecophysiological PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.3069v1 | CC BY 4.0 Open Access | rec performance, enhancing the size of populations or their spread. PeerJ Preprints | https://doi.org/10.7287/peerj.preprints.3069v1 | CC BY 4.0 Open Access | rec ABSTRACT 22 The increase in temperature as consequence of the recent global warming has been reported to generate 23 new ice-free areas in the Antarctic continent, propitiating the colonization and spread of plant 24 populations. Consequently, Antarctic vascular plants have been observed extending their southern 25 distribution. But, as the environmental conditions toward southern localities become progressively more 26 departed from the species' physiological optimum, the ecophysiological responses and survival to the 27 expected global warming could be reduced. However, if processes of local adaptation are the main cause 28 of the observed southern expansion, those populations could appear constrained to respond positively to 29 the expec...