An acquisition trade-off with fast growth in a fish,the medaka <Emphasis Type="Italic">Oryzias latipes</Emphasis>: why do low-latitude ectotherms grow more slowly?

In various ectotherms, it is well-known that high-latitude individuals grow faster at any temperature than do low-latitude individuals as an adaptation to shorter growing seasons. The submaximal growth of low-latitude ectotherms implies that there exist trade-offs with fast growth. Although there is accumulating evidence for latitudinal variation in growth capacity, however, few studies have demonstrated these trade-offs. In this study, using a freshwater fish Oryzias latipes as a model organism, we tested whether there is an acquisition trade-off in which the higher growth capacity of high-latitude individuals is realized by foraging more intensively, despite the risk of predation. Foraging experiments revealed that higher-latitude O. latipes juveniles captured more prey per unit time than lower-latitude juveniles at any temperature. In addition, predation experiments revealed that higher-latitude juveniles were more frequently killed by dragonfly larvae. Observations of swimming behaviors demonstrated that the higher vulnerability to predation in high-latitude O. latipes is probably caused by lower steady- and burst-swimming performances due to the larger meal size, and partially by reduced caution due to a greater willingness to forage. We conclude that acquisition trade-offs may be the primary constraint on growth evolution across latitudes among fishes. This implies that growth capacity evolves in response not only to the length of the growing season but also to predation pressures.     

Thermal constraints on embryonic development as a proximate cause for elevational range limits in two Mediterranean lacertid lizards

Local adaptation and range restrictions in alpine environments are central topics in biogeographic research with important implications for predicting impacts of global climate change on organisms. Temperature is strongly coupled to elevation and greatly affects life history traits of oviparous reptiles in mountain environments. Thus, species may encounter barriers for expanding their ranges if they are unable to adapt to the changing thermal conditions encountered along elevational gradients. We sought to determine whether thermal requirements for embryonic development provide a plausible explanation for elevational range limits of two species of lacertid lizards that have complementary elevational ranges in a Mediterranean mountain range (Psammodromus algirus is found at elevations below 1600 m and Iberolacerta cyreni is found at elevations above 1600 m). We combined experimental incubation of eggs in the laboratory with modelled estimates of nest temperature in the field. In both species, increasing temperature accelerated development and produced earlier hatching dates. The species associated with warmer environments (P. algirus) experienced an excessive hatching delay under the lowest incubation temperature. Moreover, newborns from eggs incubated at low temperatures showed poor body condition and very slow rates of postnatal growth. In contrast, eggs of the strictly alpine species I. cyreni exhibited shorter incubation periods than P. algirus that allowed hatching before the end of the active season even under low incubation temperatures. This was countered by lower reproductive success at higher temperatures, due to lower hatching rates and higher incidence of abnormal phenotypes. Elevational range limits of both species coincided well with threshold temperatures for deleterious effects on embryonic development. We suggest that incubation temperature is a major ecophysiological factor determining the elevational range limits of these oviparous lizards with predictable consequences for mountain distributions under future warmer climates.     

Preference and Performance in Plant–Herbivore Interactions across Latitude–A Study in U.S. Atlantic Salt Marshes

High-latitude plants are often more palatable to herbivores than low-latitude conspecifics. Does increased plant palatability lead to better herbivore performance? Our field and laboratory work investigated (A) whether high-latitude plants have traits indicating that they should be higher-quality foods for herbivores; (B) whether geographic differences in plant quality are more important than local adaptation of herbivores. We studied 3 plant species and 6 invertebrate herbivores in U.S. Atlantic Coast. Past studies had shown high-latitude individuals of these plants are more palatable than low-latitude conspecifics. We documented plant traits and herbivore performance (body size) in the field across latitude. We collected individuals from different latitudes for factorial (plant region x herbivore region) laboratory experiments, examining how herbivore performance was affected by plant region, herbivore region, and their interaction (i.e., local adaptation). Field surveys suggested high-latitude plants were likely of higher quality to herbivores. Leaf nitrogen content in all plant species increased toward high latitudes, consistent with lower leaf C/N and higher leaf chlorophyll content at high latitudes. Furthermore, leaf toughness decreased toward higher latitudes in 1 species. The body size of 4 herbivore species increased with latitude, consistent with high-latitude leaves being of higher quality, while 2 grasshopper species showed the opposite pattern, likely due to life-history constraints. In the laboratory, high-latitude plants supported better performance in 4 herbivore species (marginal in the 5th). The geographic region where herbivores were collected affected herbivore performance in all 6 species; however, the pattern was mixed, indicating a lack of local adaptation by herbivores to plants from their own geographic region. Our results suggest that more-palatable plants at high latitudes support better herbivore growth. Given that geographic origin of either plants or herbivores can affect herbivore performance, the nature of plant-herbivore interactions is likely to change if climate change “reshuffles” plant and herbivore populations across latitude.     

Does relaxed predation drive phenotypic divergence among insular populations?

The evolution of striking phenotypes on islands is a well‐known phenomenon, and there has been a long‐standing debate on the patterns of body size evolution on islands. The ecological causes driving divergence in insular populations are, however, poorly understood. Reduced predator fauna is expected to lower escape propensity, increase body size and relax selection for crypsis in small‐bodied, insular prey species. Here, we investigated whether escape behaviour, body size and dorsal coloration have diverged as predicted under predation release in spatially replicated islet and mainland populations of the lizard species Podarcis gaigeae. We show that islet lizards escape approaching observers at shorter distances and are larger than mainland lizards. Additionally, we found evidence for larger between‐population variation in body size among the islet populations than mainland populations. Moreover, islet populations are significantly more divergent in dorsal coloration and match their respective habitats poorer than mainland lizards. These results strongly suggest that predation release on islets has driven population divergence in phenotypic and behavioural traits and that selective release has affected both trait means and variances. Relaxed predation pressure is therefore likely to be one of the major ecological factors driving body size divergence on these islands.     

Adaptive responses to cool climate promotes persistence of a non-native lizard

Successful establishment and range expansion of non-native species often require rapid accommodation of novel environments. Here, we use common-garden experiments to demonstrate parallel adaptive evolutionary response to a cool climate in populations of wall lizards (Podarcis muralis) introduced from southern Europe into England. Low soil temperatures in the introduced range delay hatching, which generates directional selection for a shorter incubation period. Non-native lizards from two separate lineages have responded to this selection by retaining their embryos for longer before oviposition—hence reducing the time needed to complete embryogenesis in the nest—and by an increased developmental rate at low temperatures. This divergence mirrors local adaptation across latitudes and altitudes within widely distributed species and suggests that evolutionary responses to climate can be very rapid. When extrapolated to soil temperatures encountered in nests within the introduced range, embryo retention and faster developmental rate result in one to several weeks earlier emergence compared with the ancestral state. We show that this difference translates into substantial survival benefits for offspring. This should promote short- and long-term persistence of non-native populations, and ultimately enable expansion into areas that would be unattainable with incubation duration representative of the native range.     

Evolution of biometric and life‐history traits in lizards (Gallotia) from the Canary Islands

The aim was to study as to how biometric and life‐history traits of endemic lacertids in the Canary Islands (genus Gallotia) may have evolved, and possible factors affecting the diversification process of this taxon on successively appearing islands have been deduced. To that end, comparative analyses of sexual dimorphism and scaling of different body, head and life‐history traits to body size in 10 species/subspecies of Gallotia have been carried out. Both Felsenstein's independent contrasts and Huey and Bennett's ‘minimum evolution’ analyses show that male and female snout‐vent length (SVL) changed proportionally (sexual size dimorphism not changing with body size) throughout the evolution of these lizards and all within‐sex biometric traits have changed proportionally to SVL. Life‐history traits (size at sexual maturity, clutch size, hatchling SVL and mass, and life span) are highly correlated with adult female body size, the first two being the only traits with a positive allometry to female SVL. These results, together with the finding that the slope of hatchling SVL to female SVL regression was lower than that of SVL at maturity to female SVL, indicates that larger females reach maturity at a larger size, have larger clutches and, at the same time, have relatively smaller hatchlings than smaller females. There was no significant correlation between any pair of life‐history traits after statistically removing the effect of body size. As most traits changed proportionally to SVL, the major evolutionary change has been that of body size (a ca. threefold change between the largest and the smallest species), that is suggested to be the effect of variable ecological conditions faced by founder lizards in each island.     

Macroclimatic and maternal effects on the evolution of reproductive traits in lizards

Much of life‐history theory rests on fundamental assumptions about constraints on the acquisition and allocation of energy to growth and reproduction. In general, the allocation of energy to reproduction depends on maternal size, which in turn depends on environmental factors experienced throughout the life of the mother. Here, we used phylogenetic path analyses to evaluate competing hypotheses about the environmental and maternal drivers of reproductive traits in lizards. In doing so, we discovered that precipitation, rather than temperature, has shaped the evolution of the life history. Specifically, environments with greater rainfall have enabled the evolution of larger maternal size. In turn, these larger mothers produce larger clutches of larger offspring. However, annual precipitation has a negative direct effect on offspring size, despite the positive indirect effect mediated by maternal size. Possibly, the evolution of offspring size was driven by the need to conserve water in dry environments, because small organisms are particularly sensitive to water loss. Since we found that body size variation among lizards is related to a combination of climatic factors, mainly precipitation and perhaps primary production, our study challenges previous generalizations (e.g., temperature‐size rule and Bergmann''s rule) and suggests alternative mechanisms underlying the evolution of body size.     

Alternative intrapopulation life‐history strategies and their trade‐offs in an African annual fish

In ephemeral habitats, the same genotypes cope with unpredictable environmental conditions, favouring the evolution of developmental plasticity and alternative life‐history strategies (ALHS). We tested the existence of intrapopulation ALHS in an annual killifish, Nothobranchius furzeri, inhabiting temporary pools. The pools are either primary (persisting throughout the whole rainy season) or secondary (refilled after desiccation of the initial pool), representing alternative niches. The unpredictable conditions led to the evolution of reproductive bet‐hedging with asynchronous embryonic development. We used a common garden experiment to test whether the duration of embryonic period is associated with post‐embryonic life‐history traits. Fish with rapid embryonic development (secondary pool strategy, high risk of desiccation) produced phenotypes with more rapid life‐history traits than fish with slow embryonic development (primary pool strategy). The fast fish were smaller at hatching but had larger yolk sac reserves. Their post‐hatching growth was more rapid, and they matured earlier. Further, fast fish grew to a smaller body size and died earlier than slow fish. No differences in fecundity, propensity to mate or physiological ageing were found, demonstrating a combination of plastic responses and constraints. Such developmentally related within‐population plasticity in life history is exceptional among vertebrates.     

Life‐history differences across latitude in common side‐blotched lizards (Uta stansburiana)

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Life history patterns in lizards of the arid and semiarid zone of Australia

Summary Studies on the life histories and population dynamics of lizards in the semiarid/arid zone of Australia are reviewed to identify the influence of size (female mean snout-vent length), phylogeny (family effects) and ecological parameters on the evolution of life history traits of these species. Species producing more than one clutch per year are larger than single-clutched ones. In an ANCOVA, significant effects of size and phylogeny on clutch size and on age at sexual maturity were found. Microhabitat (arboreal, terrestrial, and subterranean life style) also had an effect on clutch size, but only mediated through a significant interaction with size. However, results of the ANCOVAs depend on the families and ecological parameters included in the analyses. Therefore, caution is necessary in interpreting or generalizing the results; in any case, size and phylogeny explain only a small percentage of the observed variation. Nevertheless, a direct comparison of a set of syntopic/paratopic desert lizards supports and extends the main conclusions of the ANCOVA. A significant but small phylogenetic effect was found, and arboreal microhabitat was associated with greater age at sexual maturity. Activity (diurnal versus nocturnal) influenced yearly mortalities and clutch frequencies. For both, microhabitat and activity, predation levels and size-dependent mortality were the likely selective factors causing these correlations. The demographic environment explains the paucity of duurnal lizard species with fixed clutch sizes in the semiarid/arid zone of Australia. Possible causes for the evolution of fixed clutch sizes are discussed.     

Patterns of interspecific variation in the heart rates of embryonic reptiles

New non-invasive technologies allow direct measurement of heart rates (and thus, developmental rates) of embryos. We applied these methods to a diverse array of oviparous reptiles (24 species of lizards, 18 snakes, 11 turtles, 1 crocodilian), to identify general influences on cardiac rates during embryogenesis. Heart rates increased with ambient temperature in all lineages, but (at the same temperature) were faster in lizards and turtles than in snakes and crocodilians. We analysed these data within a phylogenetic framework. Embryonic heart rates were faster in species with smaller adult sizes, smaller egg sizes, and shorter incubation periods. Phylogenetic changes in heart rates were negatively correlated with concurrent changes in adult body mass and residual incubation period among the lizards, snakes (especially within pythons) and crocodilians. The total number of embryonic heart beats between oviposition and hatching was lower in squamates than in turtles or the crocodilian. Within squamates, embryonic iguanians and gekkonids required more heartbeats to complete development than did embryos of the other squamate families that we tested. These differences plausibly reflect phylogenetic divergence in the proportion of embryogenesis completed before versus after laying.     

Landscape‐scale life‐history gradients in New Zealand freshwater fish

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Latitudinal population differentiation in phenology,life history and flower morphology in the perennial herb Lythrum salicaria

Abstract In plants with a wide distribution, phenological characters can be expected to vary clinally along climatic gradients, whereas other characters important for adaptation to local biotic and abiotic factors may vary in a more mosaic fashion. We used common‐garden experiments and controlled crosses to examine population differentiation in phenology, life history and morphology in the perennial herb Lythrum salicaria along a latitudinal transect through Sweden (57°N to 66°N). Northern populations initiated growth and flowering earlier, flowered for a shorter period, were shorter, produced more and larger winter buds, and were older at first reproduction than southern populations. Flower morphology varied significantly among populations, but was, with the exception of calyx length, not significantly related to latitude of origin. Survival in the common garden (at 63°49′N) was positively correlated with latitude of origin and the size and number of winter buds produced in the preceding year. The results suggest that the among‐population differences in phenology and life history have evolved in response to latitudinal variation in length of the growing season. Further studies are required to determine whether population differentiation in flower morphology is maintained by selection.     

Evolutionary divergence in life history traits among populations of the Lake Malawi cichlid fish Astatotilapia calliptera

During the early stages of adaptive radiation, populations diverge in life history traits such as egg size and growth rates, in addition to eco‐morphological and behavioral characteristics. However, there are few studies of life history divergence within ongoing adaptive radiations. Here, we studied Astatotilapia calliptera, a maternal mouthbrooding cichlid fish within the Lake Malawi haplochromine radiation. This species occupies a rich diversity of habitats, including the main body of Lake Malawi, as well as peripheral rivers and shallow lakes. We used common garden experiments to test for life history divergence among populations, focussing on clutch size, duration of incubation, egg mass, offspring size, and growth rates. In a first experiment, we found significant differences among populations in average clutch size and egg mass, and larger clutches were associated with smaller eggs. In a second experiment, we found significant differences among populations in brood size, duration of incubation, juvenile length when released, and growth rates. Larger broods were associated with smaller juveniles when released and shorter incubation times. Although juvenile growth rates differed between populations, these were not strongly related to initial size on release. Overall, differences in life history characters among populations were not predicted by major habitat classifications (Lake Malawi or peripheral habitats) or population genetic divergence (microsatellite‐based F_ST). We suggest that the observed patterns are consistent with local selective forces driving the observed patterns of trait divergence. The results provide strong evidence of evolutionary divergence and covariance of life history traits among populations within a radiating cichlid species, highlighting opportunities for further work to identify the processes driving the observed divergence.     

Thermal regimes during incubation do not affect mean selected temperatures of hatchling lizards (Bassiana duperreyi, Scincidae)

Incubation temperatures profoundly affect many phenotypic traits of squamate reptiles, and mean selected body temperatures of such animals also are plastic in response to environmental factors. Plausibly, then, incubation temperatures might affect hatchling thermoregulation, either via adaptation (i.e., populations that historically experience different nest conditions, also will diverge in hatchling thermoregulatory behaviour) or phenotypic plasticity (incubation temperatures directly modify hatchling behaviours). We tested this hypothesis with a montane scincid lizard (Bassiana duperreyi), using thermal-imaging methods to quantify temperatures (of both head and body) selected by hatchling lizards. The young lizards kept their heads cooler than their bodies, but mean selected temperatures did not differ among hatchlings from three populations with differing thermal regimes in natural nests, nor were they affected by thermal conditions during incubation. The conservatism of mean selected temperatures stands in strong contrast to the lability of many other phenotypic traits in response to incubation temperatures in this species.     

Geographic variation in avian incubation periods and parental influences on embryonic temperature

Theory predicts shorter embryonic periods in species with greater embryo mortality risk and smaller body size. Field studies of 80 passerine species on three continents yielded data that largely conflicted with theory; incubation (embryonic) periods were longer rather than shorter in smaller species, and egg (embryo) mortality risk explained some variation within regions, but did not explain larger differences in incubation periods among geographic regions. Incubation behavior of parents seems to explain these discrepancies. Bird embryos are effectively ectothermic and depend on warmth provided by parents sitting on the eggs to attain proper temperatures for development. Parents of smaller species, plus tropical and southern hemisphere species, commonly exhibited lower nest attentiveness (percent of time spent on the nest incubating) than larger and northern hemisphere species. Lower nest attentiveness produced cooler minimum and average embryonic temperatures that were correlated with longer incubation periods independent of nest predation risk or body size. We experimentally tested this correlation by swapping eggs of species with cool incubation temperatures with eggs of species with warm incubation temperatures and similar egg mass. Incubation periods changed (shortened or lengthened) as expected and verified the importance of egg temperature on development rate. Slower development resulting from cooler temperatures may simply be a cost imposed on embryos by parents and may not enhance offspring quality. At the same time, incubation periods of transferred eggs did not match host species and reflect intrinsic differences among species that may result from nest predation and other selection pressures. Thus, geographic variation in embryonic development may reflect more complex interactions than previously recognized.     

The first draft genome of Lophophorus: A step forward for Phasianidae genomic diversity and conservation

The monal genus (Lophophorus) is a branch of Phasianidae and its species inhabit the high-altitude mountains of the Qinghai-Tibet Plateau. The Chinese monal, L. lhuysii, is a threatened endemic bird of China that possesses high-altitude adaptability, diversity of plumage color and potentially low reproductive life history. This is the first study to describe the monal genome using next generation sequencing technology. The Chinese monal genome size is 1.01 Gb, with 16,940 protein-coding genes. Gene annotation yielded 100.93 Mb (9.97%) repeat elements, 785 ncRNA, 5,465,549 bp (0.54%) SSR and 15,550 (92%) genes in public databases. Compared to other birds and mammals, the genome evolution analysis showed numerous expanded gene families and positive selected genes involved in high-altitude adaptation, especially related to the adaptation of low temperature and hypoxia. Consequently, this gene data can be used to investigate the molecular evolution of high-altitude adaptation in future bird research. Our first published genome of the genus Lophophorus will be integral for the study of monal population genetic diversity and conservation, genomic evolution and Galliformes species differentiation in the Qinghai-Tibetan Plateau.     

Interpopulation variation in a fish predator drives evolutionary divergence in prey in lakes

Ecological factors are known to cause evolutionary diversification. Recent work has shown that evolution in strongly interacting predator species has reciprocal impacts on ecosystems. These divergent impacts of predators may alter the selective landscape and cause the evolution of prey. Yet, this link between intraspecific variation and evolution is unexplored. We compared the life history of a species of zooplankton (Daphnia ambigua) from lakes in New England in which the dominant planktivorous predator, the alewife (Alosa pseudoharengus), differs in feeding traits and migratory behaviour. Anadromous alewife (seasonal migrants) exhibit larger gapes, gill-raker spacing and target larger prey than landlocked alewife (year-round freshwater resident). In 'anadromous' lakes, Daphnia are abundant in the spring but extirpated by alewife predation in summer. Daphnia are rare year-round in 'landlocked' lakes. We show that Daphnia from lakes with anadromous alewife grew faster, matured earlier but at the same size and produced more offspring than Daphnia from lakes with landlocked or no alewife across multiple temperature and resource treatments. Our results are inconsistent with a response to size-selective predation but are better explained as an adaptation to colder temperatures and shorter periods of development (countergradient variation) mediated by seasonal alewife predation.     

The biology and life history of arctic populations of the littoral mite Ameronothrus lineatus (Acari, Oribatida)

The present study attempts to elucidate possible microevolutionary adaptations of life-history traits of high-latitude populations of the holarctic, littoral oribatid mite Ameronothrus lineatus by comparing arctic and temperate populations. Additionally, the paper provides an overview of the limited research on general ecology and population biology of arctic populations. In the Arctic the larviparous A. lineatus has a 5-year life cycle (larva-to-larva), and adults survive a further 2–3 years. High survival to maturity is consistent with a low lifetime reproductive output of ca. 20 larvae. The life history can be regarded as an extreme version of the typical oribatid life history. However, several life-history features suggest specific adaptations of arctic populations. In particular, the pre-moult resting stage is synchronized with the warmest part of the arctic summer, which shortens this vulnerable part of development. High reproductive investment by females at relatively low temperatures may represent a physiological adaptation to the cool arctic summer. Finally, prolonged cold exposure positively affects reproduction and survival the following summer, suggesting adaptation of the species to the highly seasonal arctic environment. On the other hand, the ability of all life-cycle stages to overwinter, and a flexible life history with the species being able to take advantage of favourable climatic conditions to accelerate development and larviposition, seem to be ancestral features. Thus, the success of A. lineatus in arctic habitats is probably attributable to a combination of derived and ancestral life-history traits. Studies of conspecific temperate populations are required to elucidate further local adaptations of arctic populations.     

Shifting latitudinal clines in avian body size correlate with global warming in Australian passerines

Intraspecific latitudinal clines in the body size of terrestrial vertebrates, where members of the same species are larger at higher latitudes, are widely interpreted as evidence for natural selection and adaptation to local climate. These clines are predicted to shift in response to climate change. We used museum specimens to measure changes in the body size of eight passerine bird species from south-eastern Australia over approximately the last 100 years. Four species showed significant decreases in body size (1.8–3.6% of wing length) and a shift in latitudinal cline over that period, and a meta-analysis demonstrated a consistent trend across all eight species. Southern high-latitude populations now display the body sizes typical of more northern populations pre-1950, equivalent to a 7° shift in latitude. Using ptilochronology, we found no evidence that these morphological changes were a plastic response to changes in nutrition, a likely non-genetic mechanism for the pattern observed. Our results demonstrate a generalized response by eight avian species to some major environmental change over the last 100 years or so, probably global warming.