Cogradient Variation Research Articles

Regional thermal variation in a coral reef fish.

How species respond to climate change will depend on the collective response of populations. Intraspecific variation in traits, evolved through genetic adaptation and phenotypic plasticity, can cause thermal performance curves to vary over species' distributions. Intraspecific variation within marine species has received relatively little attention due to the belief that marine systems lack dispersal barriers strong enough to promote locally adapted traits. Here we show that intraspecific variation is present between low- and high-latitude populations of a coral reef damselfish (Acanthochromis polyacanthus). Co-gradient variation was observed when examining aerobic physiology across a thermal gradient that reflected mean summer temperatures of high- and low-latitude regions, as well as projected future ocean temperatures (i.e. 27, 28.5, 30, 31.5°C). Whilst thermally sensitive, no significant differences were observed between high- and low-latitude regions when measuring immunocompetence, haematocrit and anaerobic enzyme activity. The presence of co-gradient variation suggests that dispersal limitations in marine systems can promote local adaptive responses; however, intraspecific variation may not be ubiquitous amongst traits. Identifying locally adapted traits amongst populations remains necessary to accurately project species responses to climate change and identify differences in adaptive potential.

Standard metabolic rate variation among New Zealand Orthoptera

Standard metabolic rates (SMR) of ectotherms reflect the energetic cost of self-maintenance and thus provide important information about life-history strategies of organisms. We examined variation in SMR among fifteen species of New Zealand orthopteran. These species represent a heterogeneous group with a wide geographic distribution, differing morphologies and life histories. Gathering original data on morphological and physiological traits of individual species is a first step towards understanding existing variability. Individual metabolic rates of ectotherms are one of the first traits to respond to climate change. Baseline SMR datasets are valuable for modeling current species distributions and their responses to a changing climate. At higher latitudes, the average environmental temperature decreases. The pattern that cold-adapted ectotherms display higher SMR at colder temperatures and greater thermal sensitivity to compensate for lower temperatures and the shorter growing and reproductive seasons is predicted from the metabolic cold adaptation (MCA) hypothesis. We predict higher SMR for the orthopteran species found at higher latitudes. We further compared the index of thermal sensitivity Q10 per species. We used closed-system respirometry to measure SMR, at two test temperatures (4 °C and 14 °C), for the fifteen species acclimated to the same conditions. As expected, we found significant differences in SMR among species. The rate of oxygen consumption was positively correlated with body mass. Our findings do not support the MCA hypothesis. In fact, we found evidence of co-gradient variation in SMR, whereby insects from higher elevations and latitudes presented lower SMR. We discuss our findings in relation to life histories and ecology of each species. The novel physiological data presented will aid in understanding potential responses of these unusual species to changing climatic conditions in Aotearoa/New Zealand.

Differentiation of Developmental Pathways Results in Different Life-History Patterns between the High and Low Latitudinal Populations in the Asian Corn Borer.

Individual insects often exhibit two alternative pathways of non-diapausing and diapausing developments. Yet, most studies have focused on the latitudinal variation in life-history traits for non-diapausing individuals. No study has examined the differences in life history traits between non-diapausing and diapausing individuals along a latitudinal gradient. We used six different geographical populations of Ostrinia furnacalis to examine the latitudinal variation in life-history traits between non-diapausing and diapausing individuals in terms of their sex ratio, larval and pupal developmental times, pupal weight, growth rate, adult weight and weight loss, and sexual size dimorphism. The results showed that latitudinal variation in life-history traits for both non-diapausing and diapausing individuals exhibited a sawtooth pattern, but the life-history pattern of the two alternative developmental pathways was significantly different between the high and low latitudes. For the non-diapausing pathway, the high-latitudinal populations showed a significantly shorter larval developmental time, higher growth rate and greater body weight than the low-latitudinal populations, suggesting countergradient variation. Conversely, in the diapausing pathway, the high-latitudinal populations had longer larval developmental times, lower growth rates and relatively smaller body weights than the low-latitudinal populations, suggesting cogradient variation. We also found that in the high-latitudinal populations, larvae in the non-diapausing pathway had shorter developmental time and higher body weight, whereas larval developmental time of the low-latitudinal populations was longer and the body weight was smaller. The relationship between larval developmental time and pupal weight was also different between the two developmental pathways. These results provide new insights into the evolution of life-history traits in this moth.

Large genetic divergence underpins cryptic local adaptation across ecological and evolutionary gradients.

Environmentally covarying local adaptation is a form of cryptic local adaptation in which the covariance of the genetic and environmental effects on a phenotype obscures the divergence between locally adapted genotypes. Here, we systematically document the magnitude and drivers of the genetic effect (VG) for two forms of environmentally covarying local adaptation: counter- and cogradient variation. Using a hierarchical Bayesian meta-analysis, we calculated the overall effect size of VG as 1.05 and 2.13 for populations exhibiting countergradient or cogradient variation, respectively. These results indicate that the genetic contribution to phenotypic variation represents a 1.05 to 2.13 s.d. change in trait value between the most disparate populations depending on if populations are expressing counter- or cogradient variation. We also found that while there was substantial variance among abiotic and biotic covariates, the covariates with the largest mean effects were temperature (2.41) and gamete size (2.81). Our results demonstrate the pervasiveness and large genetic effects underlying environmentally covarying local adaptation in wild populations and highlight the importance of accounting for these effects in future studies.

Environment and phenology shape local adaptation in thermal performance.

Populations within species often exhibit variation in traits that reflect local adaptation and further shape existing adaptive potential for species to respond to climate change. However, our mechanistic understanding of how the environment shapes trait variation remains poor. Here, we used common garden experiments to quantify thermal performance in eight populations of the marine snail Urosalpinx cinerea across thermal gradients on the Atlantic and the Pacific coasts of North America. We then evaluated the relationship between thermal performance and environmental metrics derived from time-series data. Our results reveal a novel pattern of 'mixed' trait performance adaptation, where thermal optima were positively correlated with spawning temperature (cogradient variation), while maximum trait performance was negatively correlated with season length (countergradient variation). This counterintuitive pattern probably arises because of phenological shifts in the spawning season, whereby 'cold' populations delay spawning until later in the year when temperatures are warmer compared to 'warm' populations that spawn earlier in the year when temperatures are cooler. Our results show that variation in thermal performance can be shaped by multiple facets of the environment and are linked to organismal phenology and natural history. Understanding the impacts of climate change on organisms, therefore, requires the knowledge of how climate change will alter different aspects of the thermal environment.

Metabolic cold adaptation in the Asiatic toad: intraspecific comparison along an altitudinal gradient.

The metabolic cold adaptation (MCA) hypothesis predicts an increase in metabolic rate and thermal sensitivity of poikilotherms from cold environments as compared to those from warm environments, when measured under standardized conditions. This compensatory response is also expected to evolve in life history and behavioral traits if the reductions in these phenotypic traits at low temperature involves in a reduction in fitness. We investigated the extent to which the level of energy intake (measured as feeding rate), energy turnover (measured as standard metabolic rate, SMR) and the energy budget (energy allocation to growth and physical activity) are influenced by climatic conditions in three populations of the Asiatic toad (Bufo gargarizans) distributed across an altitudinal gradient of 1350m in the Qionglai Mountains of Western China. We found a similar thermal reaction norm of SMR at both population and individual levels; therefore, the data did not support the MCA hypothesis. However, there was a co-gradient variation (CoGV) for mass change rate in which the high and medium altitudinal populations displayed slower mass change rates than their counterparts from low altitudes. Moreover, this CoGV pattern was accompanied by a low feeding rate and high physical activity for the high- and medium-altitude populations. Our results highlight that adjustments in energy intake and energy allocation to behaviors, but not energy allocation to metabolism of maintenance, could act as an energetic strategy to accommodate the varied growth efficiency in Asiatic toads along an altitudinal gradient.

Differences in spatial versus temporal reaction norms for spring and autumn phenological events

For species to stay temporally tuned to their environment, they use cues such as the accumulation of degree-days. The relationships between the timing of a phenological event in a population and its environmental cue can be described by a population-level reaction norm. Variation in reaction norms along environmental gradients may either intensify the environmental effects on timing (cogradient variation) or attenuate the effects (countergradient variation). To resolve spatial and seasonal variation in species' response, we use a unique dataset of 91 taxa and 178 phenological events observed across a network of 472 monitoring sites, spread across the nations of the former Soviet Union. We show that compared to local rates of advancement of phenological events with the advancement of temperature-related cues (i.e., variation within site over years), spatial variation in reaction norms tend to accentuate responses in spring (cogradient variation) and attenuate them in autumn (countergradient variation). As a result, among-population variation in the timing of events is greater in spring and less in autumn than if all populations followed the same reaction norm regardless of location. Despite such signs of local adaptation, overall phenotypic plasticity was not sufficient for phenological events to keep exact pace with their cues-the earlier the year, the more did the timing of the phenological event lag behind the timing of the cue. Overall, these patterns suggest that differences in the spatial versus temporal reaction norms will affect species' response to climate change in opposite ways in spring and autumn.

Adaptation potential of the copepod Eurytemora affinis to a future warmer Baltic Sea.

To predict effects of global change on zooplankton populations, it is important to understand how present species adapt to temperature and how they respond to stressors interacting with temperature. Here, we ask if the calanoid copepod Eurytemora affinis from the Baltic Sea can adapt to future climate warming. Populations were sampled at sites with different temperatures. Full sibling families were reared in the laboratory and used in two common garden experiments (a) populations crossed over three temperature treatments 12, 17, and 22.5°C and (b) populations crossed over temperature in interaction with salinity and algae of different food quality. Genetic correlations of the full siblings’ development time were not different from zero between 12°C and the two higher temperatures 17 and 22.5°C, but positively correlated between 17 and 22.5°C. Hence, a population at 12°C is unlikely to adapt to warmer temperature, while a population at ≥17°C can adapt to an even higher temperature, that is, 22.5°C. In agreement with the genetic correlations, the population from the warmest site of origin had comparably shorter development time at high temperature than the populations from colder sites, that is, a cogradient variation. The population with the shortest development time at 22.5°C had in comparison lower survival on low quality food, illustrating a cost of short development time. Our results suggest that populations from warmer environments can at present indirectly adapt to a future warmer Baltic Sea, whereas populations from colder areas show reduced adaptation potential to high temperatures, simply because they experience an environment that is too cold.

Plasticity to drought and ecotypic differentiation in populations of a crop wild relative

Populations of widely distributed species often exhibit geographic variation in functional traits in response to environmental heterogeneity. Such trait variation may be the result of different adaptive mechanisms, including genetically based differentiation, phenotypic plasticity or a combination of both. Disentangling the genetic and environmental components of trait variation may be particularly interesting in crop wild relatives, since they may provide unique reservoirs of genetic diversity for crop improvement. In this study, we assessed ecotypic differentiation and patterns of plasticity to drought in populations of Lupinus angustifolius, a Mediterranean crop wild relative, from two climatically distinct regions in the Iberian Peninsula. Using an outdoor common garden, we compared phenotypic responses of inbred maternal families to two ecologically meaningful water availability treatments (drought and high-moisture). We measured 18 different functional traits related to growth, morphology, phenology and reproduction. Plants in the drought treatment grew less, had lower leaf chlorophyll content and photochemical efficiency, but also reproduced faster, produced larger seeds and altered leaflet morphology through increased leaflet thickness, higher leaflet dry matter content and lower specific leaf area. We also found significant differences between regions that likely reflect adaptation to climatically distinct environments, with populations from the south showing a faster onset of reproduction, higher leaf thickness and higher seed size, consistent with the drier conditions experienced in southern sites. Plasticity to drought was in most cases in the same direction as quantitative genetic differentiation (i.e. cogradient variation), providing evidence of the adaptive value of the plastic change. Our results show that both genetic differentiation and plasticity can generate adaptive phenotypic variation in L. angustifolius, and help to identify potentially valuable genetic resources to incorporate into breeding programmes.

Evolution of geographic variation in thermal performance curves in the face of climate change and implications for biotic interactions.

We review the recent literature on geographic variation in insect thermal performance curves (TPCs). Despite strong thermal differences, there is often no change in TPCs across geographic gradients. When shifts occur, these are mostly vertical (indicating an overall shift in performance across temperatures, that is, countergradient or cogradient variation) and less horizontal (reflecting thermal adaptation). Based on this, using a space-for-time substitution approach, we generated likely evolutionary scenarios of TPC evolution to simulate the outcome of biotic interactions under future warming. We illustrate how taking evolution of the TPCs into account may strongly impact the predicted outcome of biotic interactions under climate warming. Importantly, both the type and the magnitude of the TPC shift was identified to be crucial to determine who will be winners and losers of biotic interactions.

Contrasting patterns of taxonomic, phylogenetic and functional variation along a Costa Rican altitudinal gradient in the plant family Melastomataceae

Abstract:The functional composition of plant communities in montane regions has been studied for decades, and most recent analyses find that environmentally favourable landscapes at lower altitudes tend to be dominated by species with resource-acquisitive traits, while more resource-conservative taxa dominate higher-altitude communities. However, it is unclear the extent to which this pattern is driven by co-gradient variation within clades or changes in clade representation across the gradient. To test for co-gradient variation, species composition, phylogenetic structure and functional traits were quantified for 97 species within the plant family Melastomataceae at five locations across a 2500-m altitudinal gradient along Volcán Barva in Costa Rica. Average melastome leaf force to punch, specific leaf area and leaf size vary with altitude, while four other functional traits do not. Taxonomic dissimilarity between communities was correlated with altitudinal difference, while phylogenetic dissimilarity was correlated with altitudinal dissimilarity only when measured with a metric that emphasizes shallow turnover of the tips of the phylogeny. These results highlight how species turnover may be more pronounced than functional or phylogenetic variation along altitudinal gradients. In addition, these results highlight the conservation value of lowland tropical forests, which here harbour a disproportionate amount of phylogenetic and functional diversity.

Variation in life-history traits of European anchovy along a latitudinal gradient: a bioenergetics modelling approach

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 617-618:95-112 (2019) - DOI: https://doi.org/10.3354/meps12574 Variation in life-history traits of European anchovy along a latitudinal gradient: a bioenergetics modelling approach Martin Huret1,*, Kostas Tsiaras2, Ute Daewel3, Morten D. Skogen4, Paul Gatti1, Pierre Petitgas5, Stelios Somarakis6 1Ifremer, STH/LBH, 29280 Plouzané, France 2Hellenic Centre for Marine Research, Anavyssos, Greece 3Helmholtz Centre Geesthacht, Institute of Coastal Research, 21502 Geesthacht, Germany 4Institute of Marine Research, 5817 Bergen, Norway 5Ifremer, EMH, 44311 Nantes, France 6Hellenic Centre for Marine Research, Heraklion, Greece *Corresponding author: martin.huret@ifremer.frAdvance View was available online July 17, 2018 ABSTRACT: Anchovy Engraulis encrasicolus distribution in European waters spans from the Mediterranean Sea to the North Sea, and is expected to expand further north with global warming. Observations from the eastern Mediterranean (North Aegean Sea), the Bay of Biscay and the North Sea reveal latitudinal differences in growth, maximum size, fecundity and timing of reproduction. We set up a mechanistic framework combining a bioenergetics model with regional physical-biogeochemical models providing temperature and zooplankton biomass to investigate the underlying mechanisms of variation in these traits. The bioenergetics model, based on the Dynamic Energy Budget theory and initially calibrated in the Bay of Biscay, was used to simulate growth and reproduction patterns. Environment partly explained the increased growth rate and larger body size towards the north. However, regional calibration of the maximum assimilation rate was necessary to obtain the best model fit. This suggests a genetic adaptation, with a pattern of cogradient variation with increasing resource towards the north, in addition to a countergradient thermal adaptation. Overall, the seasonal energy dynamics supports the pattern of body-size scaling with latitude, i.e. food-limited growth but low maintenance costs in the warm Aegean Sea, and larger size in the North Sea allowing sufficient storage capacity for overwintering. Further, the model suggests a synchronisation of reproductive timing with environmental seasonality as a trade-off between thresholds of temperature and reserves for spawning and overwintering, respectively. Finally, low temperature, short productive and spawning seasons, and insufficient reserves for overwintering appear to be current limitations for an expansion of anchovy to the Norwegian Sea. KEY WORDS: Engraulis encrasicolus · Countergradient variation · Growth · Reproduction · Dynamic Energy Budget theory · Bay of Biscay · Aegean Sea · North Sea Full text in pdf format PreviousNextCite this article as: Huret M, Tsiaras K, Daewel U, Skogen MD, Gatti P, Petitgas P, Somarakis S (2019) Variation in life-history traits of European anchovy along a latitudinal gradient: a bioenergetics modelling approach. Mar Ecol Prog Ser 617-618:95-112. https://doi.org/10.3354/meps12574 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 617-618. Online publication date: May 16, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Latitudinal cogradient variation of development time and growth rate and a negative latitudinal body weight cline in a widely distributed cabbage beetle.

The evolutionary and phenotypic responses to environmental gradients are often assumed to be the same, a phenomenon known as “cogradient variation”. However, only a few insect species display cogradient variation in physiological traits along a latitudinal gradient. We found evidence for such a response in the examination of the life history traits of the cabbage beetle Colaphellus bowringi from 6 different geographical populations at 16, 19, 22, 24, 26 and 28°C. Our results showed that larval and pupal development times significantly decreased as rearing temperature increased, and that growth rates were positively correlated with temperature. Body weight tended to decrease with increasing temperature, consistent with the general pattern in ectothermic animals. Larval development time was positively correlated with latitude, whereas the growth rate decreased as latitude increased, showing an example of latitudinal cogradient variation. Body weight significantly decreased with increasing latitude in a stepwise manner, showing a negative latitudinal body weight cline. Females were significantly larger than males, consistent with the female biased sex dimorphism in insects. Body weight tended to decrease with increasing rearing temperature, whereas the differences in sexual size dimorphism (SSD) tended to decrease with increasing body weight, which biased our results toward acceptance of Rensch’s rule. We found that weight loss was an important regulator of SSD, and because male pupae lost significantly more weight at metamorphosis than female pupae, SSD was greater in adults than in pupae. Overall, our data provide a new example that a latitudinal cogradient variation in physiological traits is associated with a negative latitudinal body weight cline.

Divergence of gastropod life history in contrasting thermal environments in a geothermal lake.

Experiments using natural populations have provided mixed support for thermal adaptation models, probably because the conditions are often confounded with additional environmental factors like seasonality. The contrasting geothermal environments within Lake Mývatn, northern Iceland, provide a unique opportunity to evaluate thermal adaptation models using closely located natural populations. We conducted laboratory common garden and field reciprocal transplant experiments to investigate how thermal origin influences the life history of Radix balthica snails originating from stable cold (6°C), stable warm (23°C) thermal environments or from areas with seasonal temperature variation. Supporting thermal optimality models, warm-origin snails survived poorly at 6°C in the common garden experiment and better than cold-origin and seasonal-origin snails in the warm habitat in the reciprocal transplant experiment. Contrary to thermal adaptation models, growth rate in both experiments was highest in the warm populations irrespective of temperature, indicating cogradient variation. The optimal temperatures for growth and reproduction were similar irrespective of origin, but cold-origin snails always had the lowest performance, and seasonal-origin snails often performed at an intermediate level compared to snails originating in either stable environment. Our results indicate that central life-history traits can differ in their mode of evolution, with survival following the predictions of thermal optimality models, whereas ecological constraints have shaped the evolution of growth rates in local populations.

Co-gradient variation in growth rate and development time of a broadly distributed butterfly.

Widespread species often show geographic variation in thermally-sensitive traits, providing insight into how species respond to shifts in temperature through time. Such patterns may arise from phenotypic plasticity, genetic adaptation, or their interaction. In some cases, the effects of genotype and temperature may act together to reduce, or to exacerbate, phenotypic variation in fitness-related traits across varying thermal environments. We find evidence for such interactions in life-history traits of Heteronympha merope, a butterfly distributed across a broad latitudinal gradient in south-eastern Australia. We show that body size in this butterfly is negatively related to developmental temperature in the laboratory, in accordance with the temperature-size rule, but not in the field, despite very strong temperature gradients. A common garden experiment on larval thermal responses, spanning the environmental extremes of H. merope's distribution, revealed that butterflies from low latitude (warmer climate) populations have relatively fast intrinsic growth and development rates compared to those from cooler climates. These synergistic effects of genotype and temperature across the landscape (co-gradient variation) are likely to accentuate phenotypic variation in these traits, and this interaction must be accounted for when predicting how H. merope will respond to temperature change through time. These results highlight the importance of understanding how variation in life-history traits may arise in response to environmental change. Without this knowledge, we may fail to detect whether organisms are tracking environmental change, and if they are, whether it is by plasticity, adaptation or both.

Sperm plasticity to seawater temperatures in Atlantic cod Gadus morhua is affected more by population origin than individual environmental exposure

Atlantic cod is a key species of the North Atlantic ecosystem whose distribution will likely be affected by climate change. Although general temperature effects on reproduction are known, there is a dearth of information on population and individual level life history and repro- ductive plasticity responses to temperature change. We tested the hypothesis that the sperm of Atlantic cod of different genetic backgrounds (southern versus more northerly Newfoundland and Labrador) and of different environmental histories (reared in indoor tanks and fed a forage diet versus reared in sea cages and fed pellets) have different average plastic responses to tempera- ture. Male reproductive performance was examined at 4 temperatures by measuring sperm swim- ming characteristics at 10 and 30 s after motility activation. Genetic origin had a larger effect on sperm swimming characteristics than past environmental history. Moreover, groups derived from the southern population exhibited a more pronounced positive mean reaction norm than the group derived from the Newfoundland and Labrador population. This represents an example of cogradient variation as genotypes accentuate the thermal phenotypic plasticity. Even though there were differences between the groups in sperm swimming characteristics, this is unlikely sufficient to affect successful reproduction at the temperatures tested unless under sperm compe- tition. Thus, sperm performance should not be a limiting factor for reproduction under predicted increases in sea surface temperatures.

Genetic divergence in forest trees: understanding the consequences of climate change

Summary Predicted climate change is heading in many respects into untested environmental conditions for trees and to the reshuffling of species distributions. We explore the consequences that these changes are likely to have on population differentiation of adaptive traits. Superimposed on the spatial redistribution of the species, will there be a redistribution of their genetic variation? We base our predictions on a conceptual framework, whose elements are the extant differentiation, and the predicted divergent evolution of populations along purposely chosen altitudinal/latitudinal gradients. We consider simultaneously phenotypic and genetic divergence, but emphasize genetically driven population differentiation. We illustrate phenotypic and genetic patterns of variation with examples from well‐studied northern and southern hemisphere tree genera Quercus and Eucalyptus. Most phenotypic traits show very large in situ clinal variation with variation in altitude or latitude. Genetic clines detected in common gardens usually follow the observed in situ phenotypic clines, reflecting cogradient variation. Rare counter gradients have also been detected, where phenotypic and genetic clines exhibit opposing signs. These patterns suggest that plasticity and selection contributed in most cases synergistically to the extant differentiation. We anticipate that microevolutionary processes will be different along environmental gradients. At the leading edge, availability of newly suitable habitats will trigger migration favouring genotypes equipped with colonists attributes. At the rear edges of the distribution, populations will be submitted to strong selective pressures favouring genotypes capable of withstanding drought and heat stress. Central populations will benefit from the plastic response of trees that will temporarily compensate for the maladaptation, until genetic adaptive variation will be restored by gene flow, mutation or recombination. We make predictions about future differentiation along environmental gradients, by highlighting traits that are likely to diverge, the rate at which differentiation will take place, and the role of gene flow and hybridization. We envisage that parallel selection may maintain differentiation at extant levels, whereas divergent selection will promote substantial differentiation for traits facilitating adaptation to contrasting conditions along the environmental gradient. We anticipate that genetic divergence may occur very rapidly and will be enhanced by the multilocus architecture of most adaptive traits.

Absence of countergradient and cogradient variation in an oceanic silverside, the California grunion Leuresthes tenuis

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 461:175-186 (2012) - DOI: https://doi.org/10.3354/meps09802 Absence of countergradient and cogradient variation in an oceanic silverside, the California grunion Leuresthes tenuis Elizabeth E. Brown*, Hannes Baumann, David O. Conover School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 11794-5000, USA *Email: eeb3780@gmail.com ABSTRACT: Spatial adaptations that maximize a species’ fitness in its local environment, particularly in the form of countergradient variation (CnGV = genotypic influences counteract environmental effects on trait variation) and cogradient variation (CoGV = genotypic influences accentuate environmental plasticity), have been documented in many estuarine and anadromous fishes. However, their prevalence in more oceanic fishes, where extensive gene flow and reduced environmental selection may preclude local adaptation, remains unclear. If oceanic species lack genetic structure, they may be limited in their ability to adapt to global climate change. We examined the potential for adaptation in oceanic fishes by testing whether an oceanic silverside, the California grunion Leuresthes tenuis, displays CnGV in growth capacity and CoGV in vertebral number across a latitudinal gradient as found in estuarine silversides. Common garden experiments revealed that reaction norms for growth in response to temperature differed little among 3 L. tenuis populations from different latitudes. Growth rates of wild adult L. tenuis measured from scale analysis suggested that growth may be slightly faster at more southern latitudes, likely due to environmental variation. Mean vertebral number in wild L. tenuis, determined from radio-graphs, were nearly identical for all populations. Overall, our results did not provide evidence for spatial adaptations in these traits of L. tenuis, in contrast to the strong patterns of latitudinal trait adaptation in other, more estuarine silversides. This study provides support for the finding that higher gene flow levels and weaker environmental selection pressures of oceanic species limit local adaptation. KEY WORDS: Latitudinal gradient · Gene flow · Adaptation · Growth capacity · Vertebral number · Climate change · Environmental selection Full text in pdf format PreviousNextCite this article as: Brown EE, Baumann H, Conover DO (2012) Absence of countergradient and cogradient variation in an oceanic silverside, the California grunion Leuresthes tenuis . Mar Ecol Prog Ser 461:175-186. https://doi.org/10.3354/meps09802 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 461. Online publication date: August 08, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Life-History Variation with Respect to Experienced Thermal Environments in the Lizard,Eremiasmultiocellata(Lacertidae)

We compared adult size, female reproductive traits, and offspring phenotypes between multiocellated racerunners (Eremias multiocellata) from two thermally different sites (populations) in Inner Mongolia (North China): the colder one in Wulatehouqi (WQ) and the warmer one in Dalateqi (DQ). Both adults and neonates were smaller in the colder site. Females from the two sites both produced a single litter of 2-5 young per season, and did not differ in allocation of energy to reproduction after accounting for differences in body size. Female neonates had more ventral scales than did males, and the WQ neonates had fewer ventral scales than did the DQ neonates. The WQ neonates were slower than the DQ neonates. When body length was normalized across populations, we found that (1) hindlimb length correlated positively with sprint speed in both WQ and DQ neonates, (2) forelimb length correlated positively with sprint speed only in the DQ neonates, and (3) tail length correlated positively with sprint speed only in the WQ neonates. Hindlimb length played a more important role in locomotion than did tail length or forelimb length. Though differing in size and morphology, neonates from the two sites did not differ in early growth and survival under identical laboratory conditions. Our data are consistent with many studies that have shown countergradient variation in physiological traits (growth rate and reproductive output) and cogradient variation in morphological traits.

Local adaptation occurs along altitudinal gradient despite the existence of gene flow in the alpine plant species Festuca eskia

Summary 1 Alpine plant species are particularly vulnerable to climate change. Therefore, estimating the adaptive potential of alpine species is of vital importance for determining their future viability. In alpine plants, adaptive potential depends on (i) altitudinal genetic differentiation among populations, combined with gene flow along an altitudinal gradient; (ii) phenotypic plasticity for the traits under selection and (iii) co-gradient variation between genetic and environmental influences on these traits. 2 The adaptive potential of Festuca eskia Ramond (Poaceae), a perennial alpine grass common in the Pyrenean Mountains, was examined in this study. A reciprocal transplant experiment involving 180 individuals along three altitudinal gradients (from 1500 to 2500 m) was established, and survival, functional and reproductive traits were recorded. In addition, four neutral sequence-tagged site and simple sequence repeat molecular markers were chosen to estimate gene flow among populations. 3 Genetic differentiation attributable to selection was detected in all traits between populations along the altitudinal gradient despite the existence of restricted gene flow. For traits directly related to fitness, local altitudinal adaptation was clearly evident. The patterns of local adaptation suggested that selection patterns differed along an altitudinal gradient. Selection for reproductive output was predominant at low altitudes, whereas differential survivorship was observed at higher altitudes. 4 Genetic differentiation with increasing altitude resulted in reduced plant stature and reproductive output but increased specific leaf area (SLA). This increased SLA at higher altitude is interpreted as a resource acquisition strategy. 5 Phenotypic plasticity was seen in all traits at the population level. Evidence of co-gradient variation between genetic differentiation and plastic response was found for all traits except SLA, suggesting that adaptive phenotypic plasticity operates in F. eskia. 6 Synthesis. Local adaptation occurs in F. eskia. It involves different adaptive traits according to the altitude. Such differentiation occurs at a small scale along altitudinal gradients despite the existence of gene flow and phenotypic plasticity. The coexistence of genetic differentiation, gene flow and phenotypic plasticity along altitudinal gradients provides an adaptive potential for F. eskia to successfully adapt to climate change.