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Data from: Variation in plant functional traits is best explained by the species identity: stability of trait based species ranking across meadow management regimes

1. It is commonly assumed in trait-based studies that plant functional traits are species-specific, being more variable among species than among different environmental conditions. If the environment affects traits it is assumed that species react in a similar direction and conserve the functional distances. The rank of species based on the trait values is then unchanged, which justifies the use of species trait averages from database values. Such assumptions of species specificity are, however, increasingly disputed by studies showing overall high intraspecific trait variability. 2. To test the species specificity and ranking stability of functional traits we sampled plant individuals of almost all species (66 in total) within each plot of a long term (19 years) land use management experiment, which comprised a factorial combination of fertilization, mowing and removal of the dominant species Molinia caerulea in an oligotrophic wet meadow in the Czech Republic. Plant individuals were measured for eight commonly used traits: height, leaf dry matter content (LDMC), specific leaf area (SLA), leaf δ13C content, leaf carbon content, leaf δ15N content, and leaf nitrogen content. Height, LDMC, and SLA were also extracted from the LEDA trait database for comparison. 3. Species identity consistently explained the largest portion of trait variability (40%-68%). Land use managements had a considerably lower effect (0.4%-9% of explained trait variability for individual traits). The species trait averages computed for each land use management regime separately were mutually correlated, showing the stable trait-based species ranking. Ranking stability of species trait averages was observed despite land use management changing absolute trait values and despite the tremendous intraspecific trait variability (causing substantial overlap of trait values for different species). For all treatments our measured species averages for LDMC and SLA were also stably ranked with species averages from the LEDA database. 4. Synthesis. Our results showed that species conserve the functional distances in different environmental conditions from where they were measured. Species trait averages can describe general trends in functional composition, although averaging reduces the ecologically interesting information of the intraspecific trait variability.

opencc-zeroDec 2015View details →

Data from: Development of a genomic resource and quantitative trait loci mapping of male calling traits in the lesser wax moth, Achroia grisella

In the study of sexual selection among insects, the Lesser Waxmoth, Achroia grisella (Lepidoptera: Pyralidae), has been one of the more intensively studied species over the past 20 years. Studies have focused on how the male calling song functions in pair formation and on the quantitative genetics of male song characters and female preference for the song. Recent QTL studies have attempted to elucidate the genetic architecture of male song and female preference traits using AFLP markers. We continued these QTL studies using SNP markers derived from an EST library that allowed us to measure both DNA sequence variation and map loci with respect to the lepidopteran genome. We report that the level of sequence variation within A. grisella is typical among other Lepidoptera that have been examined, and that comparison with the Bombyx mori genome shows that macrosynteny is conserved. Our QTL map shows that a QTL for a male song trait, pulse-pair rate, is situated on the Z chromosome, a prediction for sexually selected traits in Lepidoptera. Our findings will be useful for future studies of genetic architecture of this model species and may help identify the genetics associated with the evolution of its novel acoustic communication.

opencc-zeroJun 2019View details →

Data from: The loss of functional diversity: a detrimental influence of landscape-scale deforestation on tree reproductive traits

1. Agricultural activities such as crop production and cattle ranching are rapidly replacing forests worldwide, especially in the tropics. Resulting forest loss can adversely affect biodiversity in many ways, including trajectories of community reassembly, community composition, forest structural profiles, and taxonomic diversity. Yet, effects of forest loss on specific ecosystem functions remain limited. Processes closely linked with tree reproduction, such as pollination and seed dispersal are of paramount importance for many ecological functions in tropical forests. Disruption in these processes is known to delay or change forest regeneration, diversity, and structural dynamics. 2. To explore how reproductive and dispersal traits are being altered by landscape-scale deforestation, we surveyed and compiled trait data for tree communities in 20 tropical Atlantic rainforest remnants in northeastern Brazil, across a gradient of deforested landscapes, each retaining 3 to 93% forest cover. 3. The functional richness of reproductive plant attributes decreased as the amount of forest cover decreased, while divergence increased along the same gradient. Loss of forest cover disproportionately affected certain dispersal and reproductive attributes, with most heavily impacted functional attributes including: brief flowering duration, hermaphrodite sexual system, and zoochoric dispersal mode. We identified a clear threshold at 25-30% of forest cover, below which, reproductive attributes disappeared more quickly than expect from forest remnants. 4. Synthesis. Deforestation may impair tree community functional diversity, particularly by decreasing the number of functions and increasing certain functional reproductive attributes that are particularly successful in disturbed habitats. Under scenarios of extensive deforestation, changes to reproductive and dispersal trait profile of forest communities suggest that profound modifications in the availability of floral and seed resources are likely to be substantial. Such extensive changes to food supply of pollinating and dispersing animals suggest carry-over effects to the fauna of these important forest systems.

Data from: Variation in growth and defence traits among plant populations at different elevations: implications for adaptation to climate change

Alpine plants occurring at high elevation are vulnerable to ongoing climate change, yet relatively little is known about the potential for high‐elevation species to adapt to changing environmental conditions. In particular, the extent to which high‐elevation plants will be able to resist predicted increases in the intensity of biotic interactions, such as herbivory, remains unclear. Species distributed across broad elevational ranges provide an opportunity to investigate evolutionary mechanisms and traits involved in adaptation to varying abiotic and biotic environments. This study focused on the perennial alpine plant Arabis alpina and combined field surveys and climate‐chamber experiments to test for intraspecific genetic divergence in traits related to growth and defence against herbivores. We screened multiple populations from low, intermediate and high elevations across a broad geographic area, characterising differences in growth form, leaf structural traits, palatability for herbivores and defensive chemistry. We then quantified the proportion of variation explained by elevation and population‐level effects. Our results document within‐species genetic divergence in multiple traits relevant for adaptation to the different abiotic and biotic pressures experienced at low and high elevations. Rates of herbivore damage declined with increasing elevation in the field, but plants from high‐ and intermediate‐elevation populations were generally more palatable for specialist herbivores than those from low‐elevation populations in feeding assays. Elevational clines were also observed in several glucosinolate defence compounds, and leaf herbivory more strongly induced glucosinolates in plants from high‐elevation populations than in those from low‐elevation populations. Leaf trichome density and growth form also diverged among populations contributing to growth‐defence phenotypes associated with different elevations. However, populations from similar elevations often differed significantly in both growth and defence‐related traits, with trait variation often better explained by population‐level effects than by elevation alone. Synthesis: Arabis alpina exhibits patterns of genetic variation in growth and defence traits consistent with adaptation to different elevations. However, populations from similar elevations also diverged in many of these ecologically relevant traits. Together, the extent of the observed trait variation suggests that this alpine species has considerable potential to adapt to a changing biotic environment.

Data from: Latitudinal variation and coevolutionary diversification of sexually dimorphic traits in the false blister beetle Oedemera sexualis

Sexual traits are subject to evolutionary forces that maximize reproductive benefits and minimize survival costs, both of which can depend on environmental conditions. Latitude explains substantial variation in environmental conditions. However, little is known about the relationship between sexual trait variation and latitude, although body size often correlates with latitude. We examined latitudinal variation in male and female sexual traits in 22 populations of the false blister beetle Oedemera sexualis in the Japanese Archipelago. Males possess massive hind legs that function as a female‐grasping apparatus, while females possess slender hind legs that are used to dislodge mounting males. Morphometric analyses revealed that male and female body size (elytron length), length and width of the hind femur and tibia, and allometric slopes of these four hind leg dimensions differed significantly among populations. Of these, three traits showed latitudinal variation, namely, male hind femur was stouter; female hind tibia was slenderer, and female body was smaller at lower latitudes than at higher latitudes. Hind leg sizes and shapes, as measured by principal component analysis of these four hind leg dimensions in each sex, covaried significantly between sexes, suggesting coevolutionary diversification in sexual traits. Covariation between sexes was weaker when variation in these traits with latitude was removed. These results suggest that coevolutionary diversification between male and female sexual traits is mediated by environmental conditions that vary with latitude.

Data from: Trait correlation network analysis identifies biomass allocation traits and stem specific length as hub traits in herbaceous perennial plants

Correlations among plant traits often reflect important trade‐offs or allometric relationships in biological functions like carbon gain, support, water uptake, and reproduction that are associated with different plant organs. Whether trait correlations can be aggregated to "spectra" or "leading dimensions," whether these dimensions are consistent across plant organs, spatial scale, and growth forms are still open questions. To illustrate the current state of knowledge, we constructed a network of published trait correlations associated with the "leaf economics spectrum," "biomass allocation dimension," "seed dimension," and carbon and nitrogen concentrations. This literature‐based network was compared to a network based on a dataset of 23 traits from 2,530 individuals of 126 plant species from 381 plots in Northwest Europe. The observed network comprised more significant correlations than the literature‐based network. Network centrality measures showed that size traits such as the mass of leaf, stem, below‐ground, and reproductive tissues and plant height were the most central traits in the network, confirming the importance of allometric relationships in herbaceous plants. Stem mass and stem‐specific length were "hub" traits correlated with most traits. Environmental selection of hub traits may affect the whole phenotype. In contrast to the literature‐based network, SLA and leaf N were of minor importance. Based on cluster analysis and subsequent PCAs of the resulting trait clusters, we found a "size" module, a "seed" module, two modules representing C and N concentrations in plant organs, and a "partitioning" module representing organ mass fractions. A module representing the plant economics spectrum did not emerge. Synthesis. Although we found support for several trait dimensions, the observed trait network deviated significantly from current knowledge, suggesting that previous studies have overlooked trait coordination at the whole‐plant level. Furthermore, network analysis suggests that stem traits have a stronger regulatory role in herbaceous plants than leaf traits.

opencc-zeroDec 2012View details →

Data from: A brood parasite selects for its own egg traits

Many brood parasitic birds lay eggs that mimic their hosts' eggs in appearance. This typically arises from selection from discriminating hosts that reject eggs which differ from their own. However, selection on parasitic eggs may also arise from parasites themselves, since it should pay a laying parasitic female to detect and destroy another parasitic egg previously laid in the same host nest by a different female. In this study, I experimentally test the source of selection on greater honeyguide egg size and shape, which is correlated with that of its several host species, all of which breed in dark holes. Its commonest host species did not discriminate against experimental eggs that differed from their own in size and shape, but laying female honeyguides preferentially punctured experimental eggs more than host or control eggs. This should improve offspring survival given that multiple parasitism by this species is common, and that honeyguide chicks kill all other nest occupants. Hence, selection on egg size in greater honeyguides parasitising bee-eaters is imposed not by host defences, but by interference competition among parasites themselves.

opencc-zeroDec 2013View details →

Data from: Differentiating the evolution of female song and male-female duets in the New World blackbirds: can tropical natural history traits explain duet evolution?

Female bird song and combined vocal duets of mated pairs are both frequently associated with tropical, monogamous, sedentary natural histories. Little is known, however, about what selects for duetting behavior versus female song. Female song likely preceded duet evolution and could drive apparent relationships between duets and these natural histories. We compared the evolution of female song and male-female duets in the New World blackbirds (Icteridae) by investigating patterns of gains and losses of both traits and their relationships with breeding latitude, mating system, nesting pattern, and migratory behavior. We found that duets evolved only in lineages in which female song was likely ancestral. Both female song and duets were correlated with tropical breeding, social monogamy, territorial nesting, and sedentary behavior when all taxa were included; however, correlations between duets and these natural history traits disappeared when comparisons were limited to taxa with female song. Also, likelihood values supported stronger relationships between the natural history traits and female song than between these traits and duets. Our results suggest that the natural histories thought to favor the evolution of duetting may in fact be associated with female song and that additional selection pressures are responsible for the evolution of duets.

Data from: Contemporary ecological interactions improve models of past trait evolution

Despite the fact that natural selection underlies both traits and interactions, evolutionary models often neglect that ecological interactions may, and in many cases do, influence the evolution of traits. Here, we explore the interdependence of ecological interactions and functional traits in the pollination associations of hawkmoths and flowering plants. Specifically, we develop an adaptation of the Ornstein-Uhlenbeck model of trait evolution that allows us to study the influence of plant corolla depth and observed hawkmoth-plant interactions on the evolution of hawkmoth proboscis length. Across diverse modelling scenarios, we find that the inclusion of contemporary interactions can provide a better description of trait evolution than the null expectation. Moreover, we show that the pollination interactions provide more-likely models of hawkmoth trait evolution when interactions are considered at increasingly fine-scale groups of hawkmoths. Finally, we demonstrate how the results of best-fit modelling approaches can implicitly support the association between interactions and trait evolution that our method explicitly examines. In showing that contemporary interactions can provide insight into the historical evolution of hawkmoth proboscis length, we demonstrate the clear utility of incorporating additional ecological information to models designed to study past trait evolution.

opencc-zeroDec 2016View details →

Data from: Intraspecific variability and reaction norms of forest understory plant species traits

1.Trait-based models of ecological communities typically assume intraspecific variation in functional traits is not important, though such variation can change species trait rankings along gradients in resources and environmental conditions, and thus influence community structure and function. 2. We examined the degree of intraspecific relative to interspecific variation, and reaction norms of 11 functional traits for 57 forest understory plant species, including: intrinsic water-use efficiency (iWUE), Δ15N, 5 leaf traits, 2 stem traits and 2 root traits along gradients in light, nitrogen, moisture and understory cover. 3. Our results indicate that interspecific trait variation exceeded intraspecific variation by at least 50% for most, but not all traits. Intraspecific variation in Δ15N, iWUE, leaf nitrogen content and root traits was high (47-70%) compared with most leaf traits and stem traits (13-38%). 4. Δ15N varied primarily along gradients in abiotic conditions, while light and understory cover were relatively less important. iWUE was related primarily to light transmission, reflecting increases in photosynthesis relative to stomatal conductance. Leaf traits varied mainly as a function of light availability, with some reaction norms depending on understory cover. Plant height increased with understory cover, while stem specific density was related primarily to light. Resources, environmental conditions and understory cover did not contribute strongly to the observed variation in root traits. 5. Gradients in resources, environmental conditions and competition all appear to control intraspecific variability in most traits to some extent. However, our results suggest that species cross-over (i.e., trait rank reversals) along the gradients measured here are generally not a concern. 6. Intraspecific variability in understory plant species traits can be considerable. However, trait data collected under a narrow range of environmental conditions appears sufficient to establish species rankings and scale between community and ecosystem levels using trait-based models. Investigators may therefore focus on obtaining a sufficient sample size within a single set of conditions rather than characterizing trait variation across entire gradients in order to optimize sampling efforts.

opencc-zeroDec 2016View details →

Data from: Life history traits and functional processes generate multiple pathways to ecological stability

Stability contributes to the persistence of ecological communities, yet the interactions among different stabilizing forces are poorly understood. We assembled mesocosms with an algal resource and 1-8 different clones of the consumer Daphnia ambigua and tracked algal and Daphnia abundances through time. We then fitted coupled ordinary differential equations (ODEs) to the consumer-resource time series. We show that variation in different components of stability (local stability and the magnitude of population fluctuations) across mesocosms arises through variation in life history traits and the functional processes represented by ODE model parameters. Local stability was enhanced by increased algal growth rate and Daphnia mortality and foraging rate. Population fluctuations were dampened by high Daphnia conversion efficiency and lower interaction strengths, low algal growth rate, high Daphnia death rate, and low Daphnia foraging. These results indicate that 1) stability in consumer-resource systems may arise through the net effect of multiple related stabilizing pathways, and 2) different aspects of stability can vary independently and may respond in opposite directions to the same forces.

opencc-zeroDec 2010View details →

Data from: Hybridization alters early life-history traits and increases plant colonization success in a novel region

Hybridization is hypothesized to promote invasiveness, but empirical tests comparing the performance of hybrid versus parental taxa in novel regions are lacking. We experimentally compared colonization ability of populations of wild radish (Raphanus raphanistrum) versus populations of advanced-generation hybrids between wild and cultivated radish (R. sativus) in a southeast Texas pasture, well beyond the known invasive range of hybrid radish. We also manipulated the strength of interspecific competition to better generalize across variable environments. In both competitive environments, hybrid populations produced at least three times more seeds than wild radish populations, a distinction that was driven by greater hybrid seedling emergence, earlier hybrid emergence and more hybrid seedlings surviving to flower, rather than by greater individual fecundity. Flowering duration in hybrids was less negatively affected by competition than it was in wild radishes, while early emergence was associated with subsequent high seed output in both biotypes. Our data show that hybridization can enhance colonization success in a novel region, and, by comparison with previous studies, that the life-history traits enhancing hybrid success can differ across regions, even for lineages originating from the same hybridization event. These results imply a much larger arena for hybrid success than previously appreciated.

opencc-zeroDec 2013View details →

Data from: Sexually antagonistic association between paternal phenotype and offspring viability reinforces total selection on a sexually selected trait

The evolution of conspicuous sexually selected traits, such as horns or antlers, has fascinated biologists for more than a century. Elaborate traits can only evolve if they substantially increase reproduction, because they probably incur survival costs to the bearer. Total selection on these traits, however, includes sexual selection on sires and viability selection on offspring and can be influenced by changes in each of these components. Non-random associations between paternal phenotype and offspring viability may thus affect total selection on sexually selected traits. Long-term data on wild bighorn sheep (Ovis canadensis) provide the first evidence in nature that association between paternal phenotype and lamb viability strengthens total selection on horn size of adult rams, a sexually selected trait. The association of paternal horn length and offspring viability was sexually antagonistic: long-horned males sired sons with high viability but daughters of low viability. These results shed new light on the evolutionary dynamics of an iconic sexually selected trait and have important implications for sustainable wildlife management.

Data from: Optimising trait and source selection for explaining occurrence and abundance changes: a case study using British Butterflies

Functional traits that define the ecological role of an organism are increasingly being used to determine and predict responses to environmental change. Functional trait analyses of butterflies remain underexplored compared with other taxa, such as plants. Previous works using butterfly functional traits have not comprehensively addressed issues about the quality of trait data sets used and the relative predictive power of different trait types. We compare the consistency of trait descriptions between six widely used trait sources for the British butterfly fauna. We analysed consistency of trait sources using Fleiss's kappa and ICC. PCA was used to produce species ordinations, comparing outputs to examine which trait sets were better at explaining recent species range and abundance changes within the UK. There was a large range in congruence values for specific traits between sources. No single source can be relied upon to produce accurate trait information for British butterflies. Most trait sets are poor predictors of abundance and occurrence changes but are better at predicting current occurrence. An extensive trait set, supplementing biotope-related traits with explicit resource-based information recovers more informative ecological classifications and models than those primarily based on life-history traits or biotope descriptors. Smaller trait sets do, however, recover the specialist-generalist continuum. We conclude that analyses of distribution and abundance changes that rely on traits are highly dependent on trait source and trait type. For butterflies, traits that are based on measures of biotope occupancy should be avoided in explaining changes of abundance and distribution. Including trait information that describes their resource requirements is essential for such analyses.

opencc-zeroDec 2012View details →

Data from: Both male and female novel traits promote the correlated evolution of genitalia between the sexes in an arthropod

The correlated evolution of genitalia between sexes has been demonstrated in many taxa. However, it remains unclear whether female rather than male genitalia can play a key role in the correlated evolution of male and female genitalia. We conducted an extensive cross-population analysis of the divergence patterns of genital structures, weights of whole genital organs and the bodies of both sexes, and male genital length in a group of xystodesmid millipedes showing diverse genital morphologies. We demonstrate that the correlated evolution of male and female genitalia toward exaggerated states has occurred in the millipedes, which have evolved novel traits in both males (forceps-like gonopods) and females (retractable bellows). Enlargement and elongation of forceps-like gonopods may be advantageous in sperm competition, whereas enlargement and elongation of the bellows may facilitate acceptance/rejection of insemination for ensuring the female's fitness. These male and female genital parts have affected the correlated evolution in the opposite sex, resulting in diversification and exaggeration of genital morphology. Our study suggests that evolutionary novel traits in not only males but also in females could play an important role in the correlated evolution of genitalia between the sexes.

Data from: Trait patterns of epiphytes compared to other plant life forms along a tropical elevation gradient

Compared to other plant life forms, epiphytes remain understudied. Understanding the responses of epiphytes to changing environmental conditions is necessary to predict changes in ecosystem functioning especially in subtropical and tropical regions. We investigated the functional traits of epiphytes along a large elevation gradient on Mount Kilimanjaro, Tanzania. We measured traits of co-occurring trees and terrestrial non-tree life forms, and compared changes in community-weighted means of traits (CWM) and trait spread, the range of observed trait values. We chose traits linked to growth and persistence: leaf area, specific leaf area, leaf dry matter content, stem specific density, plant height, leaf carbon, leaf nitrogen, and leaf phosphorus. For most traits, differences in community-weighted means between life forms exceeded differences within life forms along the elevation gradient. Many CWM showed linear changes with elevation, but no response and unimodal patterns were also frequent. This was best explained by temperature, or a combination of temperature with precipitation or humidity, indicating effects of these factors on the distribution of epiphytic and non-epiphytic species. Trait spread did not change with elevation in nearly half of the traits, but hump-shaped patterns were also common, probably a result of weaker environmental filtering in the gradient center. The magnitude of trait spread, i.e. the variability between species of the same life form within communities, was highest for terrestrial non-trees. Excluding ferns from the analyses lead to marked differences in trait patterns for epiphytes, as ferns made up 59 % of the epiphytic species, while playing a minor role in the other groups. The observed differences can be explained by a dichotomy in epiphytic life strategies, with tough-leaved xero-tolerant species on one side and succulent soft-leaved species on the other. However, the influence of phylogeny was lower than expected from the taxonomic composition of the three life form groups. Our results emphasize that environmental constraints act upon functional traits of epiphytes, trees and terrestrial non-trees. The differences in trait expressions, arguably adaptations of the different life forms, need to be taken into account in conservation contexts as well as when modeling the effects of global change on ecosystems.

opencc-zeroDec 2014View details →

Data from: Life history traits and phenotypic selection among sunflower crop-wild hybrids and their wild counterpart: implications for crop allele introgression

Hybridization produces strong evolutionary forces. In hybrid zones, selection can differentially occur on traits and selection intensities may differ among hybrid generations. Understanding these dynamics in crop-wild hybrid zones can clarify crop-like traits likely to introgress into wild populations and the particular hybrid generations through which introgression proceeds. In a field experiment with four crop-wild hybrid Helianthus annuus (sunflower) cross types, we measured growth and life history traits and performed phenotypic selection analysis on early season traits to ascertain the likelihood, and routes, of crop allele introgression into wild sunflower populations. All cross types overwintered, emerged in the spring, and survived until flowering, indicating no early life history barriers to crop allele introgression. While selection indirectly favored earlier seedling emergence and taller early season seedlings, direct selection only favored greater early season leaf length. Further, there was cross type variation in the intensity of selection operating on leaf length. Thus, introgression of multiple early season crop-like traits, due to direct selection for greater early season leaf length, should not be impeded by any cross type and may proceed at different rates among generations. In sum, alleles underlying early season sunflower crop-like traits are likely to introgress into wild sunflower populations.

Data from: Evidence for contemporary and historical gene flow between guppy populations in different watersheds, with a test for associations with adaptive traits

In dendritic river systems, gene flow is expected to occur primarily within watersheds. Yet, rare cross‐watershed transfers can also occur, whether mediated by (often historical) geological events or (often contemporary) human activities. We explored these events and their potential evolutionary consequences by analyzing patterns of neutral genetic variation (microsatellites) and adaptive phenotypic variation (male color) in wild guppies (Poecilia reticulata) distributed across two watersheds in northern Trinidad. We found the expected signatures of within‐watershed gene flow; yet we also inferred at least two instances of cross‐watershed gene flow—one in the upstream reaches and one further downstream. The upstream cross‐watershed event appears to be very recent (41 ± 13 years), suggesting dispersal via recent flooding or undocumented human‐mediated transport. The downstream cross‐watershed event appears to be considerably older (577 ± 265 years), suggesting a role for rare geological or climatological events. Alongside these strong signatures of both contemporary and historical gene flow, we found little evidence of impacts on presumably adaptive phenotypic differentiation, except perhaps in the one instance of very recent cross‐watershed gene flow. Selection in this system seems to overpower gene flow—at least on the spatiotemporal scales investigated here.

opencc-zeroDec 2016View details →

Data from: Population density and structure drive differential investment in pre- and postmating sexual traits in frogs

Sexual selection theory predicts a trade-off between premating (ornaments and armaments) and postmating (testes and ejaculates) sexual traits, assuming that growing and maintaining these traits is costly and that total reproductive investments are limited. The number of males in competition, the reproductive gains from investing in premating sexual traits, and the level of sperm competition are all predicted to influence how males allocate their finite resources to these traits. Yet, empirical examination of these predictions is currently scarce. Here, we studied relative expenditure on pre- and postmating sexual traits among frog species varying in their population density, operational sex ratio and the number of competing males for each clutch of eggs. We found that the intensifying struggle to monopolize fertilizations as more and more males clasp the same female to fertilize her eggs shifts male reproductive investment toward sperm production and away from male weaponry. This shift, which is mediated by population density and the associated level of male–male competition, likely also explains the trade-off between pre- and postmating sexual traits in our much broader sample of anuran species. Our results highlight the power of such a multi-level approach in resolving the evolution of traits and allocation trade-offs.