AbstractThe last 30 years have seen major advances in our understanding of the evolution of cooperation-traits that have evolved because of the benefit they provide other individuals. In contrast, we have been much less successful in determining the consequences of cooperation for long-term ecological and evolutionary change. Studies of birds, insects, and bacteria suggest that cooperation has major consequences for fundamental features of life, such as ecological niche range, genetic variation within species, and rates of species diversification. However, the role of cooperation in driving these changes is largely limited to hypotheses, as we lack both data and a general theoretical framework. We synthesize the progress that has been made and highlight the major gaps in our understanding for future study.

Baumard and André (2025) have suggested that cultural dynamics can be studied as a form of ecology. This provides a simpler unified approach to explaining cultural evolution, within the context of human behavioiur being shaped by natural selection. We briefly expand on two points: (1) why inclusive fitness represents our most general answer to what organisms are selected to maximise; (2) the potential for using existing eco-evolutionary theory methods to model cultural evolution.

Interspecific pollen transfer (IPT), the pollen movement between plant species via shared pollinators, reduces the reproductive success of pollen‐recipient plants due to hybridization with heterospecific pollen grains. As a result, IPT hinders coexistence of sympatric, co‐flowering species by reducing their reproductive success. IPT likely exerts selective pressure on plant reproductive systems, particularly on sex allocation (resource investment to pollen versus ovules). However, the influence of IPT on the evolutionary dynamics of sex allocation and associated ecological processes remains poorly understood. Here, we explore how the female costs incurred by IPT affect the co‐evolution and coexistence dynamics of two plant species. To address this, we construct a mathematical model capturing interactions between two plant species through pollen transfer and resource competition, and reduced fertilization caused by IPT. Our analysis focuses on a scenario where an invasive species with female‐biased sex allocation enters a habitat occupied by a resident species with evolutionarily stable, equal sex allocation (Fisherian sex allocation). Using adaptive dynamics theory, we demonstrated that, irrespective of IPT strength, natural selection drives both species toward equal sex allocation, consistent with the Fisherian sex allocation theory. We present two key predictions of eco‐evolutionary outcomes. First, when the impacts of IPT are comparable for both species, the resulting eco‐evolutionary dynamics lead to their stable coexistence. In contrast, if IPT from the invasive species is disproportionately stronger than IPT from the resident species, the invasive species' evolutionary shift from female‐biased to equal sex allocation drives the resident species to extinction. Since local mate competition in small populations can favour female‐biased sex allocation, our results suggest that invasive species experiencing reduced local mate competition may drive resident species to extinction. Our findings underscore the intricate role of IPT‐driven sex allocation evolution in shaping coexistence of closely related plant species.

A fundamental problem in ecology is understanding the changes in species composition among sites (i.e. beta-diversity). It is unclear how spatial heterogeneity in species occupancy across sites shapes patterns of beta-diversity. To address this question, we develop probabilistic models that consider two spatial or temporal sites, where presence probabilities vary both among species and between the sites. We derive analytical and approximate formulae for the expectation of pairwise beta-diversity. Using a graphical tool, stochastic incidence plots (SIPs), which depict the presence probabilities in two sites along species labels, we develop a means to conceptualize the heterogeneity in presence probabilities: the steepness or unevenness of SIPs reflects species-level heterogeneity, while the degree of overlap between SIPs indicates site-level heterogeneity. We find that when SIPs completely overlap (i.e. two sites have the same presence probability for each species), flat SIPs - with all species having the same presence probability - maximize the expected beta-diversity. We refer to this prediction as the 'transfer principle for beta'. Second, using SIPs and the probabilistic method in a two-species scenario, we demonstrate that beta-diversity is lower when SIPs are parallel compared to when they are anti-parallel. We also find that this prediction is consistent with the well-known checkerboard pattern in incidence matrices. Finally, we apply the method to the species distribution models for five woodpecker species in Switzerland, showing that their spatial distributions will change significantly. Overall, this work improves our understanding of how pairwise beta-diversity responds to occupancy heterogeneity.

Interspecific pollen transfer (IPT), the movement of pollen grains between different plant species by sharing pollinators, incurs costs (fitness reduction) for seed production. IPT thereby reduces the reproductive success of co-flowering plants sharing pollinators, thus preventing their coexistence. However, the impact of IPT on the evolutionary dynamics and evolution-mediated ecological dynamics of sex allocation resource investment to pollen versus ovules) is poorly understood. Here, we investigate the consequences of the female costs incurred by IPT for the co-evolution and coexistence of two plants, by using a mathematical model where two plant species interact with each other via resource competition, pollen movements within and between species, and reduced fertilization due to IPT. The ecological situation we consider here is that an invasive species with female-biased sex allocation immigrates into a habitat of a resident species whose sex allocation is evolutionarily maintained at Fisherian sex allocation (FSA). By using adaptive dynamics theory, we found that regardless of the strength of IPT, natural selection favours the equal allocation to pollen grains and ovules (FSA) for both species. If the mutual impact of IPT on two species is similar in magnitude, we find that the eco-evolutionary dynamics can lead to their stable coexistence. In contrast, when only the invasive species negatively impacts the resident species through IPT, the evolution in invasive species from female-biased sex allocation to FSA causes the extinction of the resident species. Given that local mate competition in small populations is expected to result in female-based sex allocation, our finding suggests that if invasive species are relaxed from local mate competition, they may drive the resident species to extinction. Our study highlights the importance and complexity of the evolution of biased sex allocation driven by IPT to understand the coexistence of closely related plant species. ### Competing Interest Statement The authors have declared no competing interest.

Understanding how community assembly during the initial faunization phases determines the difference in species richness is a fundamental question in ecology. However, there are few predictions for when and to what degree the differences in species richness between subcommunities will emerge. Here, we investigate the expectation of richness difference in a pair of subcommunities, assuming that species may have different and independent presence probabilities. We then introduce several indices and examine how expected richness difference is determined by the indices. We found that (i) species differences (the average of species presence probabilities in two subcommunities divided by the total presence probability) have inconsistent effects on richness difference; (ii) the degree of spatial heterogeneity (average of differences in species presence probabilities in two subcommunities across species) may, but not always, have a good predictive ability for richness difference; and (iii) the absolute difference in average presence probabilities (site-suitability difference) has robust predictive ability for richness difference unless richness difference is very small. This work provides a theoretical framework for predicting and analyzing species richness difference from presence-absence data based on null models.

Biodiversity describes the variety of organisms on planet earth. Ecologists have long hoped for a synthesis between analyses of biodiversity and analyses of biotic interactions among species, such as predation, competition and mutualism. However, it is often unclear how to connect details of these interactions with complex modern analyses of biodiversity. To resolve this gap, we propose a unification of models of biotic interactions and measurements of diversity. We show that analyses of biodiversity obscure details about biotic interactions. For example, identical changes in biodiversity can arise from predation, competition or mutualism. Our approach indicates that traditional models of community assembly miss key facets of diversity change. Instead, we suggest that analyses of diversity change should focus on partitions, which measure mechanisms that directly shape changes in diversity, notably species level selection and immigration, rather than traditional analyses of biotic interactions.

Understanding how the spatial variation in species composition (beta-diversity) varies with biotic and abiotic conditions is one of the ultimate goals in biology. Theory predicts that beta-diversity is a consequence of two factors, species-level differences (defined as the variations among species in the probabilities that species are present in the landscape) and spatial heterogeneity (defined as the difference, between two sites, in the probabilities with which species are present). At present, however, the importance of each factor is unclear. Here, we take a probabilistic and combinatorial approach to examine the effects of species differences and spatial heterogeneity on the degree to which species assemblages in two spatial locations differ in species compositions. We first derived analytical and approximation formulae of the expectation and variance of the pairwise beta-diversity, based on the assumption that the presence probabilities of species are independent of each other. Though it seems intuitive that greater species differences leads to greater beta-diversity, our methods predict that the reverse is likely to occur under some circumstances; strikingly, when space is homogeneous, beta-diversity decreases with increasing species differences. This prediction suggests that policy making for increasing species traits-variation would, without adequately managing environmental heterogeneity, induce biotic homogeneization, resulting in undesired outcomes. Second, we illustrate our method using data from five woodpecker species in Switzerland, showing that the woodpecker species’ joint distributions change considerably with time, and also that such changes are basically explained by the changes in the incidences of some of the species. The new framework can improve our understanding of how pairwise beta-diversity responds to species differences and spatial heterogeneity.### Competing Interest StatementThe authors have declared no competing interest.

Ecological and evolutionary processes show various population dynamics depending on internal interactions and environmental changes. While crucial in predicting biological processes, discovering general relations for such nonlinear dynamics has remained a challenge. Here, we derive a universal information-theoretical constraint on a broad class of nonlinear dynamical systems represented as population dynamics. The constraint is interpreted as a generalization of Fisher’s fundamental theorem of natural selection. Furthermore, the constraint indicates nontrivial bounds for the speed of critical relaxation around bifurcation points, which we argue are universally determined only by the type of bifurcation. Our theory is verified for an evolutionary model and an epidemiological model, which exhibit the transcritical bifurcation, as well as for an ecological model, which undergoes limit-cycle oscillation. This work paves a way to predict biological dynamics in light of information theory, by providing fundamental relations in nonequilibrium statistical mechanics of nonlinear systems.

ABSTRACTEcologists have long recognized that the losses and gains in local species abundances can either decrease or increase spatial beta diversity, phenomena often referred to as biotic homogenization and differentiation, respectively. However, quantifying such dynamic impacts of species abundances on beta diversity has remained a methodological challenge.Here, we develop a numerical method to additively partition the temporal changes in beta diversity into distinct components that reflect the losses and gains in local species abundances. Our method is based on Ružička and Bray–Curtis indices and the normalized abundance-based Whittaker’s beta diversity. The temporal changes in these measures are partitioned into components that represent biotic homogenization and differentiation driven by abundance losses and gains at both species and community levels.Application of the method to a Swedish fish community dataset revealed decreases in beta diversity between 1990 and 2018. The homogenization of fish communities was explained by gains, but not losses, in species abundances across sites. Species-level partitioning further showed that the homogenization was largely caused by the increased population sizes of a particular species in sites where it was already present.The results highlight that our partitioning method effectively identifies local population and community processes embedded in regional biodiversity patterns. We believe that explicit analyses of the losses and gains in species abundances should bring deeper insights into the dynamics of beta diversity.

Negative interspecific mating interactions, known as reproductive interference, can hamper species coexistence in a local patch and promote niche partitioning or geographical segregation of closely related species. Conspecific sperm precedence (CSP), which occurs when females that have mated with both conspecific and heterospecific males preferentially use conspecific sperm for fertilization, might contribute to species coexistence by mitigating the costs of interspecific mating and hybridization. We discussed whether two species exhibiting CSP can coexist in a local environment in the presence of reproductive interference. First, using a behaviorally explicit mathematical model, we demonstrated that two species characterized by negative mating interactions are unlikely to coexist because the costs of reproductive interference, such as loss of mating opportunity with conspecific partners, are inevitably incurred when individuals of both species are present. Second, we experimentally examined differences in mating activity and preference in two Harmonia ladybird species known to exhibit CSP. These behavioral differences may lead to local extinction of H. yedoensis because of reproductive interference by H. axyridis. This prediction is consistent with field observations that H. axyridis uses various food sources and habitats whereas H. yedoensis is confined to a less preferred prey item and a pine tree habitat. Finally, by a comparative approach, we observed that niche partitioning or parapatric distribution, but not sympatric coexistence in the same habitat, is maintained between species with CSP belonging to a wide range of taxa, including vertebrates and invertebrates living in aquatic or terrestrial environments. Taken together, it is possible that reproductive interference may destabilize local coexistence even in closely related species that exhibit CSP.

Hamilton's local mate competition theory provided an explanation for extraordinary female-biased sex ratios in a range of organisms. When mating takes place locally, in structured populations, a female-biased sex ratio is favored to reduce competition between related males, and to provide more mates for males. However, there are a number of wasp species in which the sex ratios appear to more female biased than predicted by Hamilton's theory. It has been hypothesized that the additional female bias in these wasp species results from cooperative interactions between females. We investigated theoretically the extent to which cooperation between related females can interact with local mate competition to favor even more female-biased sex ratios. We found that (i) cooperation between females can lead to sex ratios that are more female biased than predicted by local competition theory alone, and (ii) sex ratios can be more female biased when the cooperation occurs from offspring to mothers before dispersal, rather than cooperation between siblings after dispersal. Our models formally confirm the verbal predictions made in previous experimental studies, which could be applied to a range of organisms. Specifically, cooperation can help explain sex ratio biases in Sclerodermus and Melittobia wasps, although quantitative comparisons between predictions and data suggest that some additional factors may be operating.

Pollinator‐mediated reproductive interference can occur when two or more plant species share the same pollinators. Recent studies have suggested that prior autonomous selfing mitigates reproductive interference, potentially facilitating coexistence even in the absence of pollination niche partitioning (i.e. the pre‐emptive selfing hypothesis). However, whether the evolution of prior selfing promotes coexistence, in the context of the eco‐evolutionary dynamics of population size, selfing rates and inbreeding depression, remains poorly understood. We constructed an individual‐based model to examine the conditions under which the evolution of prior selfing promotes coexistence in the context of mutual reproductive interference. In the model, two plant species compete by way of mutual reproductive interference, and both have the potential to evolve the capacity for prior autonomous selfing. We expected that purging of deleterious mutations might result in evolutionary rescue, assuming that the strength of inbreeding depression declines as the population selfing rate increases; this would enable inferior competitors to maintain population density through the evolution of prior selfing. Our simulation demonstrated that evolution of prior selfing may promote coexistence, whereas reproductive interference in the absence of such evolution results in competitive exclusion. We found that lower pollinator availability is likely to favour rapid evolutionary shifts to higher prior selfing rates, thereby neutralising the negative effects of reproductive interference in both species. When the strength of inbreeding depression decreased with an increase in the population‐level selfing rate, moderate pollinator availability resulted in long‐term coexistence in which relative abundance‐dependent selection on the prior selfing rate served to intermittently maintain the population density of the inferior competitor. Synthesis . We demonstrate that the evolution of prior selfing may increase population growth rates of inferior competitors and may consequently promote long‐term coexistence via an evolutionary rescue. This constitutes a novel mechanism explaining the co‐evolutionary coexistence of closely related plant species without niche partitioning, and is consistent with recent studies reporting that closely related species with mixed mating systems can co‐occur sympatrically, even under conditions of mutual reproductive interference.

The last two decades have witnessed unprecedented changes in beta diversity, the spatial variation in species composition, from local to global scales. However, analytical challenges have hampered empirical ecologists from quantifying the extinction and colonisation processes behind these changing beta diversity patterns. Here, we develop a novel numerical method to additively partition the temporal changes in beta diversity into components that reflect local extinctions and colonisations. By applying this method to empirical datasets, we revealed spatiotemporal community dynamics that were otherwise undetectable. In mature forests, we found that local extinctions resulted in tree communities becoming more spatially heterogeneous, while colonisations simultaneously caused them to homogenise. In coral communities, we detected non-random community disassembly and reassembly following an environmental perturbation, with a temporally varying balance between extinctions and colonisations. Partitioning the dynamic processes that underlie beta diversity can provide more mechanistic insights into the spatiotemporal organisation of biodiversity.

The puzzling sex ratio behavior of Melittobia wasps has long posed one of the greatest questions in the field of sex allocation. Laboratory experiments have found that, in contrast to the predictions of theory and the behavior of numerous other organisms, Melittobia females do not produce fewer female-biased offspring sex ratios when more females lay eggs on a patch. We solve this puzzle by showing that, in nature, females of Melittobia australica have a sophisticated sex ratio behavior, in which their strategy also depends on whether they have dispersed from the patch where they emerged. When females have not dispersed, they lay eggs with close relatives, which keeps local mate competition high even with multiple females, and therefore, they are selected to produce consistently female-biased sex ratios. Laboratory experiments mimic these conditions. In contrast, when females disperse, they interact with nonrelatives, and thus adjust their sex ratio depending on the number of females laying eggs. Consequently, females appear to use dispersal status as an indirect cue of relatedness and whether they should adjust their sex ratio in response to the number of females laying eggs on the patch.

Evolutionary ecological theory suggests that selection arising from interactions with conspecifics, such as sexual and kin selection, may result in evolution of intraspecific conflicts and evolutionary 'tragedy of the commons'. Here, we propose that such an evolution of conspecific conflicts may affect population dynamics in a way that enhances species coexistence. Empirical evidence and theoretical models suggest that more abundant species is more susceptible to invasion of 'selfish' individuals that increase their own reproductive success at the expense of population growth (intraspecific adaptation load). The density-dependent intraspecific adaptation load gives rise to a self-regulation mechanism at the population level, and stabilizes species coexistence at the community level by negative frequency-dependence.

Determining whether pollination occurs competitively or rather facilitatively among co‐flowering plants is a central question in plant reproductive ecology. Kobayashi [2018; Journal of Ecology 107 : 1433–1438] theoretically investigated the scenario in which intraspecific pollen tube competition (male–male competition) can lead to regulation of population growth due to reduced female success. Kobayashi (2018) showed that evolutionary dynamics in intraspecific pollen tube competition can reduce female success and consequently generate negative density‐dependence of population growth, which allows for numerous species to coexist in a spatially subdivided metacommunity. Kobayashi (2018) hypothesized that trait evolution driven by sexual selection may maintain biodiversity. However, the models proposed by Kobayashi (2018) allow for the assumptions to be relaxed; he assumed: (i) fully global seed dispersal (instead of limited dispersal, albeit the spatial subdivision), (ii) fully local pollination (i.e., pollination occurred exclusively within patches), (iii) selfing rate was exactly proportionate (i.e., pollen grains distributed equally among all individuals within a patch, irrespective of their parental origins), (iv) haploid mode of inheritance, and most importantly, (v) each individual was mutually competitive, rather than facilitative for pollination. Here, I extend the models of Kobayashi (2018) and show that when I relax assumptions (i)–(v), facilitativeness, as opposed to competitiveness, is more likely to be favoured by selection. The present results are attributed to kin selection in gametopythic competition among relatives in spatially subdivided populations. If facilitativeness for pollination is favoured by kin selection, then the premise that the evolution of pollen traits can generate negative density‐dependence does not necessarily follow. I also discuss the potential mechanisms by which pollen phenotypes can either strengthen or attenuate intraspecific and interspecific competition.

The scandalous sex ratio behaviour of Melittobia wasps has long posed one of the greatest problems for the field of sex allocation. In contrast to the predictions of theory, and the behaviour of numerous other organisms, laboratory experiments have found that Melittobia females do not produce less female-biased offspring sex ratios when more females lay eggs on a patch. We resolve this scandal, by showing that, in nature, females of M. australica have sophisticated sex ratio behaviour, where their strategy also depends upon whether they have dispersed from the patch where they emerged. When females have not dispersed, they will be laying eggs with close relatives, which keeps local mate competition high, even with multiple females, and so they are selected to produce consistently female-biased sex ratios. Laboratory experiments mimic these conditions. In contrast, when females disperse, they will be interacting with non-relatives, and so they adjust their sex ratio depending upon the number of females laying eggs. Consequently, females appear to use dispersal status as an indirect cue of relatedness, and whether they should adjust their sex ratio in response to the number of females laying eggs on the patch.### Competing Interest StatementThe authors have declared no competing interest.

AbstractThe scandalous sex ratio behaviour ofMelittobiawasps has long posed one of the greatest problems for the field of sex allocation. In contrast to the predictions of theory, and the behaviour of numerous other organisms, laboratory experiments have found thatMelittobiafemales do not produce less female-biased offspring sex ratios when more females lay eggs on a patch. We resolve this scandal, by showing that, in nature, females ofM. australicahave sophisticated sex ratio behaviour, where their strategy also depends upon whether they have dispersed from the patch where they emerged. When females have not dispersed, they will be laying eggs with close relatives, which keeps local mate competition high, even with multiple females, and so they are selected to produce consistently female-biased sex ratios. Laboratory experiments mimic these conditions. In contrast, when females disperse, they will be interacting with non-relatives, and so they adjust their sex ratio depending upon the number of females laying eggs. Consequently, females appear to use dispersal status as an indirect cue of relatedness, and whether they should adjust their sex ratio in response to the number of females laying eggs on the patch.