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opencc-zeroJun 2020View details →

Data from: Distinct cold tolerance traits independently vary across genotypes in Drosophila melanogaster

The ability to cope with low temperature is a critical adaptation in thermally variable environments. Cold hardiness is comprised of several traits, including minimum temperatures for growth and activity, ability to survive severe cold, and ability to recover normal function after cold subsides. Across species, these traits are correlated and share physiological mechanisms, suggesting they were shaped by shared evolutionary processes. However, the extent cold hardiness traits and their associated mechanisms covary within populations has not been assessed. We measured five cold hardiness traits – critical thermal minimum (CTmin), chill coma recovery (CCR), acute and chronic cold tolerance, and cold-induced changes in locomotor behavior – along with cold-induced expression of two genes with known roles in cold hardiness (Heat Shock Protein 70 and Frost) – across 12 lines of D. melanogaster derived from a single population. We observed significant genetic variation in all traits, but few correlated across genotypes, and these correlations were sex-dependent. Further, cold-induced gene expression varied by genotype, but there was no evidence supporting our hypothesis that cold-hardy lines would have either higher baseline expression or induction of stress genes. These results suggest cold hardiness traits possess unique mechanisms and may have the capacity to evolve independently.

opencc-zeroJun 2020View details →

Independent evolutionary changes in fine-root traits among main clades during the diversification of seed plants

Rationale: Changes in fine-root morphology are typically associated with transitions from the ancestral arbuscular mycorrhizal (AM) to the alternative ectomycorrhizal (ECM) or non-mycorrhizal (NM) associations. However, the modifications in root morphology may also coincide with new modifications in leaf hydraulics and growth habit during angiosperm diversification. These hypotheses have not been evaluated concurrently, which limits our understanding of the causes of fine-root evolution. Methods: To explore the evolution of fine-root systems, we assembled a 600+ species database to reconstruct historical changes in seed plants over time. We utilize ancestral reconstruction approaches together with phylogenetically informed comparative analyses to test whether changes in fine-root traits were most strongly associated with mycorrhizal affiliation, leaf hydraulics or growth form. Key Results: Our findings show significant shifts in root diameter, specific root length and root tissue density as angiosperms diversified, largely independent from leaf changes or mycorrhizal affiliation. Growth form was the only factor associated with fine-root traits in statistical models including mycorrhizal association and leaf venation, suggesting substantial modifications in fine-root morphology during transitions from woody to non-woody habits. Conclusion: Divergences in fine-root systems were crucial in the evolution of seed plant lineages, with important implications for ecological processes in terrestrial ecosystems.

zenodo36/100

Complex multi-trait responses to multivariate environmental cues in a seasonal butterfly

Dataset for 'Complex multi-trait responses to multivariate environmental cues in a seasonal butterfly'.

opencc-by-4.0Jul 2020View details →

Data from: The effectiveness of pseudomagic traits in promoting divergence and enhancing local adaptation

The first file contains the code necessary to generate figures in the style of Fig 1 of the associated manuscript. These figures show the divergence between both ecological traits and mating traits by the strength of mating preference. Different panels correspond to different rates of recombination between these loci that control these types of traits. Files S1 and S2 are Mathematica versions of the corresponding files in the Supplementary Information of the paper.

Seaweed functional diversity revisited: confronting traditional groups with quantitative traits

1. Macroalgal (seaweed) beds and forests fuel coastal ecosystems and are rapidly reorganising under global change, but quantifying their functional structure still relies on binning species into coarse groups on the assumption that they adequately capture relevant underlying traits. 2. To interrogate this 'group gambit', we measured 12 traits relating to competitive dominance and resource economics across 95 macroalgal species collected from the UK and widespread on North-East Atlantic rocky shores. We assessed the amount of trait variation explained by commonly-used traditional groups – (i) two schemes based on gross morphology and anatomy and (ii) two categorisations of vertical space use – and examined species reclassification into post hoc, so-called emergent groups arising from the functional trait dataset. We then offer an alternative, emergent grouping scheme of macroalgal functional diversity. 3. (i) Morphology and anatomy-based groups explained slightly more than a third of multivariate trait expression with considerable group overlap (i.e. low precision) and extensive mismatch with underlying trait expression (i.e. low accuracy). (ii) Categorisations of vertical space use accounted for about a quarter of multivariate trait expression with considerable group overlap. Nonetheless, turf species tended to display attributes of opportunistic forms. (iii) A nine-group emergent scheme provided a highly explanatory and parsimonious alternative to traditional functional groupings. 4. Synthesis: Our analysis using a comprehensive dataset of directly measured functional traits revealed a general mismatch between traditional groups and underlying traits, highlighting the deficiencies of the group gambit in macroalgae. While existing grouping schemes may allow first order approximations, they risk considerable loss of information at the trait and, potentially, ecosystem levels. Instead, we call for further development of a trait-based approach to macroalgal functional ecology to capture unfolding community and ecosystem changes with greater accuracy and generality.

Data from: Change in sexual signalling traits outruns morphological divergence across an ecological gradient in the post‐glacial radiation of the songbird genus Junco

The relative roles of natural and sexual selection in promoting evolutionary lineage divergence remains controversial and difficult to assess in natural systems. Local adaptation through natural selection is known to play a central role in promoting evolutionary divergence, yet secondary sexual traits can vary widely among species in recent radiations, suggesting that sexual selection may also be important in the early stages of speciation. Here we compare rates of divergence in ecologically relevant traits (morphology) and sexually selected signaling traits (coloration) relative to neutral structure in genome-wide molecular markers, and examine patterns of variation in sexual dichromatism to explore the roles of natural and sexual selection in the diversification of the songbird genus Junco (Aves: Passerellidae). Juncos include divergent lineages in Central America and several dark-eyed junco (J. hyemalis) lineages that diversified recently as the group recolonized North America following the last glacial maximum (c.a. 18,000 years ago). We found an accelerated rate of divergence in sexually selected characters relative to ecologically relevant traits. Moreover, sexual dichromatism measurements suggested a positive relationship between the degree of color divergence and the strength of sexual selection when controlling for neutral genetic distance. We also found a positive correlation between dichromatism and latitude, which coincides with the geographic axis of decreasing lineage age in juncos but also with a steep ecological gradient. Finally, we found significant associations between genome-wide variants linked to functional genes and proxies of both sexual and natural selection. These results suggest that the joint effects of sexual and ecological selection have played a prominent role in the junco radiation.

Divergent adaptations in resource-use traits explain how pikas thrive on the roof of the world

Life in extreme environments is possible through multilevel adaptations to physical and biotic stresses. At high elevations, species face numerous challenges, besides low oxygen levels, but previous studies have focused on genetic and physiological adaptations to chronic hypoxia while overlooking other key strategies for thriving in alpine landscapes. Here, we investigate resource-use trait adaptations to extreme elevations using pikas as a model, lagomorphs distributed up to 6200 metres and reaching maximum diversity on the Qinghai-Tibet plateau, the highest plateau on Earth. Specifically, we assess cranial evolution in pikas using geometric morphometric and phylogenetic comparative techniques to determine whether adaptations among high-elevation biota shown at the molecular and physiological levels also occur in resource-use traits. We further explore the roles of two contrasting lifestyles (burrowing and rocky-dwelling) in cranial evolution. We found that alpine species exhibit striking phenotypic specialization to distinct microhabitats. Contrary to physiological and genetic adaptive convergence, we show that the cranium has undergone adaptive divergence likely reflecting past resource competition in highlands and long-term association with alpine landscapes. Our analyses also reveal that the evolution of burrowing lifestyle allows high-elevation pikas to explore novel niches and boosts their phenotypic diversification. In addition to cold and hypoxia tolerance, high cranial specialization, the appearance of burrowing habits, and strong niche separation explain how pikas overcome alpine stresses and flourish on the highest plateau on Earth. By contrast, when moving to spatially complex and heterogeneous vegetation zonation, pikas exhibit generalist skull forms able to exploit diverse habitats. These findings mirror previously reported intraspecific patterns in mammals, suggesting a general morphological response in resource-exploiting traits to cope with distinct selection pressures across elevation zones. Phenotypic diversity is further constrained by rocky habitats, resulting in convergent skulls. Our study highlights that adaptations to extreme environments occur at multiple levels of organization, but can lead to distinct evolutionary paths depending on which selective forces they respond to. The evolution of burrowing behaviour represents a landmark in the evolutionary history of pikas. We further show that rocky habitats impose strong ecological pressures, leading to convergent responses in resource-use traits, which is rarely documented in mammals.

Data from: Cost of an elaborate trait: a tradeoff between attracting females and maintaining a clean ornament

Many sexually selected ornaments and weapons are elaborations of an animal's outer body surface, including long feathers, colorful skin, and rigid outgrowths. The time and energy required to keep these traits clean, attractive, and in good condition for signaling may represent an important, but understudied cost of bearing a sexually selected trait. Male fiddler crabs possess an enlarged and brightly colored claw that is used both as a weapon to fight with rival males and also as an ornament to court females. Here, we demonstrate that males benefit from grooming because females prefer males with clean claws over dirty claws, but also that the time spent grooming detracts from the amount of time available for courting females. Males therefore face a temporal tradeoff between attracting the attention of females and maintaining a clean claw. Our study provides rare evidence of the importance of grooming for mediating sexual interactions in an invertebrate, indicating that sexual selection has likely shaped the evolution of self-maintenance behaviors across a broad range of taxa.

Data from: The stronger, the better – trait hierarchy is driving alien species interaction

Multiple invaders commonly co-occur in native ecosystems and in some cases have been shown to facilitate each other thus exacerbating impacts on native species, while in other cases one invader may reduce the impact of another due to competition. We therefore aimed at identifying mechanisms driving alien species interactions. We conducted a common garden experiment investigating all pairwise combinations of 20 alien annual plant species in Germany. We first tested whether competition or facilitation occurred more often. Secondly, we determined whether individual traits, hierarchical or absolute trait distances, multivariate trait or phylogenetic distance explained alien plant interactions best. Thirdly, we assessed whether accounting for trait plasticity explains plant performance better than species-level trait averages. While the magnitude of interspecific competition compared to intraspecific competition was on average larger across the 190 alien species combinations, interspecific facilitation still occurred in 24% of cases. Interactions could be better explained by hierarchical trait distances which reflect competitive ability, compared to phylogenetic and multivariate trait distance (reflecting niche differences). This finding supports criticisms about the applicability of testing limiting similarity versus environmental filtering and the community phylogenetic approach. Specifically, when growing taller and having a lower specific leaf area than the co-occurring alien neighbour, biomass and seed number of individuals in mixture increased compared to growing alone. Effects of seed mass, root:shoot ratio and flowering time depended on the performance measure. In contrast to recent suggestions, accounting for trait plasticity did not necessarily explain plant performance better than models using species-level trait averages. These results advance our fundamental understanding of trait-interaction relationships, strengthening recent findings on the importance of competitive hierarchy in shaping interactions and community structure. In particular, applying these concepts to the novel case of alien-alien interactions, is crucial given the continuing accumulation of alien species around the globe.

Data from: Along with intraspecific functional trait variation, individual performance is key to resolving community assembly processes

<ol> <li>Species contributing high proportions to community biomass strongly influence ecosystem processes within the community. Studies have shown that dominant species may serve as nurse plants, helping to ensure biomass stability of the subordinate species under stress conditions. The question is widely debated as to whether either niche differentiation or neutral processes drive the net outcome of plant interactions within a subordinate plant community. To answer this question, requires precise estimates of individual variation in functional traits and performance.</li> <li>In a five-year mesocosm experiment, the functional responses of a subordinate plant community to the removal of the dominant species were evaluated across two drought-stress scenarios. Small scale (i.e., large pots) wetland communities were constructed comprising one dominant species (Carex elata) and three subordinate species. Removal of the dominant species allowed evaluation of the net effects of drought and interspecific interactions. We estimated the functional divergences for three traits (specific leaf area, leaf dry matter content and height growth allocation) and compared these with performance differences quantified individually. This enabled distinctions to be made between deterministic (i.e., niche differentiation) and neutral processes driving the drought response of the subordinate community.</li> <li>We showed that the dominant species decreased relative performance differences within the subordinate plant community under conditions of permanent drought stress. These changes were associated with the convergence of traits related to resource acquisition and growth. The dominant species equalised species performance differences by supressing relatively drought-tolerant species with low competitive ability and by supporting the less drought-tolerant species with relatively high competitive ability. Meanwhile, under conditions of interannual drought, the subordinate species likely coexisted due to differentiation in resource-use strategies and the interaction with the dominant species.</li> <li>Inclusion of individual variation in performance with a functional trait approach provides valuable insights into the processes structuring plant communities. Ours is the first study to provide evidence that subordinate species exposed to drought may coexist via neutral processes arising from their interactions with the dominant species, leading to functional convergence of traits associated with the trade-off between stress tolerance and competitive ability.</li> </ol>

Data from: Between predators and parasitoids: complex interactions among shelter traits, predation, and parasitism in a shelter-building caterpillar community

<ol> <li>Shelter building is widespread in the animal world and such shelters often influence the success of their builders. Shelters built by caterpillars influence the likelihood of attacks by natural enemies, but how particular shelter traits influence caterpillar survival is not known. Furthermore, the differential effects of certain shelter traits on some natural enemies, such as predators, may lead to "enemy-free space" for other natural enemies (parasitoids). The parasitoid enemy-free space hypothesis has not been directly tested for shelter-building caterpillars.</li> <li>To understand how shelter traits influence caterpillar survival, shelter traits, predation, and parasitism were measured simultaneously for 24 caterpillar morphospecies (1465 caterpillars) in a tropical dry forest and analyzed in a phylogenetic context.</li> <li>Shelter type, shelter openness, and whether shelters accumulated frass had different amounts of phylogenetic signal, with frass accumulation displaying the most and shelter openness the least.</li> <li>All three traits affected the frequency with which caterpillar species experienced predation. Predation was elevated in two shelter types (leaf folds and leaf rolls) compared to cut-and-fold shelters. Combinations of shelter openness and frass accumulation also affected predation, with closed frass-free shelters having the lowest predation and closed frass-filled shelters having the highest.</li> <li>Parasitism was not affected by shelter traits but was strongly correlated with evolutionary history and negatively correlated with predation.</li> <li>These results confirm a trade-off between predation and parasitism and demonstrate that predation can be more frequent than parasitism. Different shelter types result in different amounts of predation. These defensive shelter traits and their effectiveness also vary phylogenetically. Together, our results suggest that predation and parasitism determine the success of shelter-building caterpillars, and that success is a function of the specific shelter they construct. More generally, our results demonstrate the importance of considering the effects of defensive traits on both predators and parasitoids when investigating interactions between herbivores and natural enemies.</li> </ol>

opencc-zeroJan 2020View details →

Data from: Drivers of plant traits that allow survival in wetlands

<ol> <li>Plants have developed a suite of traits to survive the anaerobic and anoxic soil conditions in wetlands. Previous studies on wetland plant adaptive traits have focused mainly on physiological aspects under experimental conditions, or compared the trait expression of the local species pool. Thus, a comprehensive analysis of potential factors driving wetland plant adaptive traits under natural environmental conditions is still missing.</li> <li>In this study, we analysed three important wetland adaptive traits, i.e. root porosity, root/shoot ratio and underwater photosynthetic rate, to explore driving factors using a newly compiled dataset of wetland plants. Based on 21 studies at 38 sites across different biomes, we found that root porosity was affected by an interaction of temperature and hydrological regime; root:shoot ratio was affected by temperature, precipitation and habitat type; and underwater photosynthetic rate was affected by precipitation and life form. This suggests that a variety of driving mechanisms affect the expression of different adaptive traits.</li> <li>The quantitative relationships we observed between the adaptive traits and their driving factors will be a useful reference for future global methane and denitrification modelling studies. Our results also stress that besides the traditionally emphasized hydrological driving factors, other factors at several spatial scales should also be taken into consideration in the context of future functional wetland ecology.</li> </ol>

On the effect of asymmetrical trait inheritance on models of trait evolution

Current phylogenetic comparative methods modelling quantitative trait evolution generally assume that, during speciation, phenotypes are inherited identically between the two daughter species. This, however, neglects the fact that species consist of a set of individuals, each bearing its own trait value. Indeed, because descendent populations after speciation are samples of a parent population, we can expect their mean phenotypes to randomly differ from one another potentially generating a ``jump'' of mean phenotypes due to asymmetrical trait inheritance at cladogenesis. Here, we aim to clarify the effect of asymmetrical trait inheritance at speciation on macroevolutionary analyses, focusing on model testing and parameter estimation using some of the most common models of quantitative trait evolution. We developed an individual-based simulation framework in which the evolution of species phenotypes is determined by trait changes at the individual level accumulating across generations and cladogenesis occurs then by separation of subsets of the individuals into new lineages. Through simulations, we assess the magnitude of phenotypic jumps at cladogenesis under different modes of trait inheritance at speciation. We show that even small jumps can strongly alter both the results of model selection and parameter estimations, potentially affecting the biological interpretation of the estimated mode of evolution of a trait. Our results call for caution when interpreting analyses of trait evolution, while highlighting the importance of testing a wide range of alternative models. In the light of our findings, we propose that future methodological advances in comparative methods should more explicitly model the intra-specific variability around species mean phenotypes and how it is inherited at speciation.

opencc-by-4.0Aug 2020View details →

zenodo36/100

Density-dependent natural selection mediates harvest-induced trait changes

Rapid life-history changes caused by size-selective harvesting are often interpreted as a response to direct harvest selection against a large body size. However, similar trait changes may result from a harvest-induced relaxation of natural selection for a large body size via density-dependent selection. Here, we show evidence of such density-dependent selection favouring large-bodied individuals at high population densities, in replicated pond populations of medaka fish. Harvesting, in contrast, selected medaka directly against a large body size and, in parallel, decreased medaka population densities. Five years of harvesting were enough for harvested and unharvested medaka populations to inherit the classically-predicted trait differences, whereby harvested medaka grew slower and matured earlier than unharvested medaka. We demonstrate that this life-history divergence was not driven by direct harvest selection for a smaller body size in harvested populations, but by density-dependent natural selection for a larger body size in unharvested populations.

Root trait responses to drought are more heterogeneous than leaf trait responses

Drought can strongly modify plant diversity and ecosystem processes. As droughts are expected to intensify in the future, it is important to better understand plant responses to this global driver. Root traits are an overlooked but powerful predictor of plant responses to drought because they are in direct contact with the soil environment and are responsible for taking up nutrients and water. Here, we determine which root traits are sensitive to drought and the magnitude of that response. We also tested whether root trait relationships with shoot biomass are affected by drought and to what extent all these responses depend on plant species identity. To do so, we conducted a glasshouse experiment with 24 plant species grown in pots (10 replicates per species), which included grasses, forbs and legumes. All replicates were well watered during the first month and then half of them were kept under drought (30 % water holding capacity (WHC)), with the other half serving as control (70 % WHC). After two months of treatment, leaf and root traits were measured. Leaf traits had a strong and more uniform response to drought compared to root traits. Root trait responses were variable and differed among plant species. Overall, grasses and several forbs had increased root diameter with drought while forbs had decreased specific root surface area (SRSA) and specific root length (SRL). Increase of root diameter and reduction of root elongation or sacrificing fine roots are different strategies that may promote nutrient and water acquisition, depending on plant species identity. Our results identify changes in root morphological traits as mechanisms to likely tolerate drought and highlight that, although such drought responses are species-specific, they are phylogenetically clustered.

How butterflies keep their cool: physical and ecological traits influence thermoregulatory ability and population trends.

Understanding which factors influence the ability of individuals to respond to changing temperatures is fundamental to species conservation under climate change. We investigated how a community of butterflies responded to fine-scale changes in air temperature, and whether species-specific responses were predicted by ecological or morphological traits. Using data collected across a UK reserve network, we investigated the ability of 29 butterfly species to buffer thoracic temperature against changes in air temperature. First, we tested whether differences were attributable to taxonomic family, morphology or habitat association. We then investigated the relative importance of two buffering mechanisms: behavioural thermoregulation versus fine-scale microclimate selection. Finally, we tested whether species' responses to changing temperatures predicted their population trends from a UK-wide dataset. We found significant interspecific variation in buffering ability, which varied between families and increased with wing length. We also found interspecific differences in the relative importance of the two buffering mechanisms, with species relying on microclimate selection suffering larger population declines over the last 40 years than those that could alter their temperature behaviourally. Our results highlight the importance of understanding how different species respond to fine-scale temperature variation, and the value of taking microclimate into account in conservation management to ensure favourable conditions are maintained for temperature-sensitive species.

Data from: Addition of nitrogen to canopy versus understory has different effects on leaf traits of understory plants in a subtropical evergreen broad–leaved forest

Atmospheric nitrogen (N) deposition has substantial effects on forest ecosystems. The effects of N deposition on understory plants have been simulated by spraying N on the forest floor. Such understory addition of N (UAN) might simulate atmospheric N deposition in a biased manner, because it bypasses the canopy. We compared the effects of UAN and canopy addition of N (CAN) at 0, 25, and 50 kg N ha–1 year–1 on specific leaf area (SLA), leaf construction costs (CC), concentrations of leaf carbon ([C]), nitrogen ([N]), phosphorus ([P]), minerals ([Mineral]), nitrate ([NO3-]), lignin ([Lignin]), lipids ([Lipid]), organic acids ([OA]), soluble phenolics ([SP]), total non-structural carbohydrates ([TNC]), and total structural carbohydrates ([TSC]) in six dominant understory species in a subtropical evergreen forest after five years of N treatments. We found that leaf CC, [C], [Lignin], [OA], [TNC] and [TSC] were significantly affected by N-addition approach and rate, but leaf [P] and [Lipid] were affected by N-addition approach and N-addition rate, respectively; leaf CC, [C], [P], [OA], and [TNC] were significantly lower under UAN than under CAN, but leaf [TSC] and [Lignin] were significantly higher and lower, respectively, under UAN than under CAN at 50 kg N ha–1 year–1; the decline of leaf [C] and [Lignin] contributed to the significantly lower leaf CC under UAN than under CAN. Synthesis. We show that canopy and understory N addition exerted significantly different effects on leaf traits of understory plants. The results indicate that understory plants in subtropical forest respond differently to understory addition of N from those to atmospheric deposition of N. Further studies are warranted to evaluate the unbiased ecological processes and functions of forest ecosystem responding to atmospheric N deposition via both canopy and understory N addition experiments over a longer term.

Integrating floral trait and flowering time distribution patterns help reveal a more dynamic nature of co-flowering community assembly processes

Species' floral traits and flowering times are known to be the major drivers of pollinator-mediated plant-plant interactions in diverse co-flowering communities. However, their simultaneous role in mediating plant community assembly and plant-pollinator interactions is still poorly understood. Since not all species flower at the same time, inference of facilitative and competitive interactions based on floral trait distribution patterns should account for fine phenological structure (intensity of flowering overlap) within co-flowering communities. Such an approach may also help reveal the simultaneous action of competitive and facilitative interactions in structuring co-flowering communities. Here we used modularity within a co-flowering network context, as a novel approach to detect convergent and/or over-dispersed patterns in floral trait distribution and pollinator sharing. Specifically, we evaluate differences in floral trait and pollinator distribution patterns within (high temporal flowering overlap) and among co-flowering modules (low temporal flowering overlap). We further evaluate the consistency of observed floral trait and pollinator sharing distribution patterns across space (three geographic regions) and time (dry and rainy seasons). We found that floral trait similarity was significantly higher in plant species within co-flowering modules than in species among them. This suggests pollinator facilitation may lead to floral trait convergence, but only within co-flowering modules. However, our results also revealed seasonal and spatial shifts in the underlying interactions (facilitation or competition) driving co-flowering assembly, suggesting that the prevalent dominant interactions are not static. Synthesis: Overall, we provide strong evidence showing that the use of flowering time and floral trait distribution alone may be insufficient to fully uncover the role of pollinator-mediated interactions in community assembly. Integrating this information along with patterns of pollinator sharing will greatly help reveal the simultaneous action of facilitative and competitive pollinator-mediated interactions in co-flowering communities. The spatial and temporal variation in flowering and trait distribution patterns observed further emphasize the importance of adopting a more dynamic view of community assembly processes.

Heatwave effects on the behavior and life history traits of sedentary antlions

Research on the behavioral responses of animals to extreme weather events, such as heatwaves, is lacking even though their frequency and intensity in nature are increasing. Here, we investigated the behavioral response to a simulated heatwave in two species of antlions (Neuroptera: Myrmeleontidae). These insects spend the majority of their lives as larvae and live in sandy areas suitable for a trap-building hunting strategy. We used larvae of Myrmeleon bore and Euroleon nostras, which are characterized by different microhabitat preferences – sunlit in the case of M. bore and shaded in the case of E. nostras. Larvae were exposed to fluctuating temperatures (40ºC for 10 hours daily and 25ºC for the remaining time) or a constant temperature (25ºC) for an entire week. We found increased mortality of larvae under heat. We detected a reduction in the hunting activity of larvae under heat, which corresponded to changes in the body mass of individuals. Furthermore, we found long-term consequences of the simulated heatwave, as it prolonged the time larvae needed to molt. These effects were pronounced in the case of E. nostras but did not occur or were less pronounced in the case of M. bore, suggesting that microhabitat-specific selective pressures dictate how well antlions handle heatwaves. We thus present results demonstrating the connection between behavior and the subsequent changes to fitness-relevant traits in the context of a simulated heatwave. These results illustrate how even closely related species may react differently to the same event.

Data for Analysis of Keystone Predation - trait based or driven by extrinsic processes?

Keystone predation can be a determinant of community structure, including species diversity, but factors underlying "keystoneness" have been minimally explored. Using the system in which the original keystone, the sea star Pisaster ochraceus, was discovered, we focused on two potential (but overlapping) determinants of keystoneness: intrinsic traits or state variables of the species (e.g., size, density), and extrinsic environmental parameters (e.g., prey productivity) that may provide conditions favorable for keystone predator evolution. Using a comparative-experimental approach, with repeated field experiments at multiple sites across a variable coastal environment, we tested predation rates, or how quickly predators consumed prey, and predation effects, or community response to predator presence or absence. We tested five hypotheses: (H1) predation rates and effects will vary in space but not time; (H2) per population predation rates will vary primarily with individual traits and population variables; (HJHH3) per capita predation rates will vary only with individual traits; (H4) predation effects will vary with traits, variables, and external drivers; and (H5) as predicted by the keystone predation hypothesis, diversity will vary unimodally with predation pressure. As hypothesized, predation rates differed among sites but not over time (H1), and in caging exclusion experiments, predation effect varied with both intrinsic and extrinsic factors (H4). Unexpectedly, predation rates varied with both intrinsic and extrinsic (H2, per population), or only with extrinsic (H3, per capita) factors. Further, in large-plot exclusion experiments, predation effect was most closely associated with individual traits (contra H4). Finally, taxon diversity varied unimodally with proxies of predation pressure (sessile prey abundance) and was sensitive to extrinsic factors (mussel growth, temperature, and upwelling) (H5). Hence, keystoneness depended on predator individual traits, predator population variables, and environmental parameters. However, temporal differences in caging experiments suggested that environmental characteristics underlying prey dynamics may be preeminent. Compared to prior experiments, predation was weaker with low prey input compared to periods with high prey input. Collectively, our results suggest that keystone predator evolution depends on the coalescence of species-specific characteristics, and environmental parameters favoring high prey productivity. Our approach may be a model for future studies exploring the generality of keystoneness.