Biology subjects

Knell, R. J.

Publications and source records attributed to Knell, R. J..

4 recordsLinked to original sources

bioRxiv2026

Population Resilience Under Environmental Deterioration in Socially Monogamous Systems with Mutual Mate Choice

Rapid environmental change and biodiversity loss make it increasingly important to identify factors influencing population extinction risk. Previous studies examining how mating systems can affect persistence of populations under environmental stress generally report higher extinction risks in monogamous than polygynous systems but have largely ignored extra-pair copulations (EPC) and paternity (EPP), despite the prevalence of genetic polyandry in socially monogamous species. Here, using an individual-based model, we study how EPP in socially monogamous systems affects population resilience under directional environmental change. We assume that in socially monogamous species, both sexes carry costly sexual ornaments, the elaboration of which depends on the strength of preference. The effect of EPPs on extinction risk depended on the strength of mate preference, population size, and the degree to which homozygosity affected fitness. Systems with EPCs are not simply intermediate in resilience between strict monogamy and polygyny: the preference strength interacts with mating system, leading to superior resilience of EPC systems compared to strictly monogamous and polygynous systems when choosiness and the negative consequences of heterozygosity loss are low, and EPP rates are high. However, this benefit was reduced in small populations due to faster loss of heterozygosity. At high choosiness, EPC systems exhibited lower resilience than socially polygynous choice systems because the higher reproductive skew of the latter system allowed them to adapt faster while not suffering from the demographic consequences of sexual signaling costs borne by females. Overall, our results suggest that EPCs can enhance population resilience when females obtain fertilizations from higher-condition extra-pair males compared to systems without EPC.

evolutionary biology↗

bioRxiv2026

Mating Systems and Evolutionary Rescue

Animal mating systems are hugely diverse, ranging from species where mating is essentially random to those exhibiting complex systems of mate choice by one or both sexes, with some species mating monogamously and others showing various degrees of promiscuity. There is now good evidence that if male signal traits are correlated with fitness, then polygynous female choice systems can show improved adaptation and persistence, but there has been little exploration of the ways that other types of mating systems modulate adaptation and evolutionary rescue. To address this, we developed an individual-based model that allows random mating, female-only choice, and mutual mate choice to be compared within both monogamous and polygynous frameworks and used it to explore how mating systems influence adaptive response, loss of heterozygosity, and extinction risk under changing environmental conditions. We find that mating system interacts with population size in determining extinction risk: because mate choice under polygyny lowers effective population size, accelerating the loss of heterozygosity, small polygynous populations with either mutual or female-only mate choice face higher extinction risks than randomly mating populations. In larger populations where inbreeding and genetic drift are less important, female-choice and mutual-choice polygynous systems show the greatest resilience to environmental change by allowing better-adapted males to dominate reproduction. Random mating populations show the lowest resilience to environmental change when populations are large and mutual-choice monogamous systems have intermediate resilience. Among polygynous systems, female-only choice leads to slower loss of heterozygosity and facilitates population resilience better than mutual mate choice. These findings demonstrate that mating systems can critically shape a populations ability to adapt to environmental change and alter extinction risks, emphasizing the need to consider mating systems in designing effective conservation strategies.

evolutionary biology↗

bioRxiv2025

Fighting Through the Heat: How Sexual Selection Influences Demography Under Recurrent Heatwaves

Sexual selection is a potent evolutionary force with complex effects. Strong sexual selection can enhance adaptation and reduce mutational load, while simultaneously reducing survival, or causing sexual conflict that reduces fitness for one or both sexes. Many populations today face not only gradual environmental changes but also extreme, short-term stress events like droughts or heatwaves. The combined effects of sexual and environmental selection on population demography during and after such events remain poorly understood, even though such combined effects could be crucial for the persistence of small, endangered populations under climate change. In this study, we investigated how sexual selection affects survival during environmental stress by manipulating the expression of an aggressive fighter morph in small populations of the male-dimorphic soil mite Sancassania berlesei, exposing some of these populations to recurrent periods of extreme heat and monitoring survival over eight generations. We found that heat exposure reduced survival, more severely in females than in males, and survival was lower in populations with higher fighter prevalence, but there was no interaction between temperature and fighter morph prevalence. Furthermore, survival declined across generations, and the decline was steeper in populations with lower prevalence of fighters, leading to the loss of their initial survival advantage by the last generation. T265625hree populations exposed to heat became extinct during the experiment, all from the reduced fighter expression treatment. Our findings imply that despite its cost to individual survival, sexual selection does not modulate population sensitivity to heatwaves over several generations. Furthermore, we demonstrate that these mortality costs of sexual selection are gradually compensated over successive generations, which could be a result of a more effective purging of inbreeding depression. Thus, while the additive effect of sexual selection and heatwaves on survival may increase demographic risks for bottlenecked populations in the short term, sexual selection may increase resilience of populations to prolonged bottlenecks.

evolutionary biology↗

bioRxiv2018

Metacommunity-scale biodiversity regulation and the self-organized emergence of macroecological patterns

There exist a number of key macroecological patterns whose ubiquity suggests the spatio-temporal structure of ecological communities is governed by some universal mechanisms. The nature of these mechanisms, however, remains poorly understood. Here we probe spatio-temporal patterns species richness and community composition using a simple metacommunity assembly model. Despite making no a priori assumptions regarding biotic spatial structure or the distribution of biomass across species, model metacommunities self-organize to reproduce well documented patterns including characteristic species abundance distributions, range size distributions and species area relations. Also in agreement with observations, species richness in our model attains an equilibrium despite continuous species turnover. Crucially, it is in the neighbourhood of the equilibrium that we observe the emergence of these key macroecological patterns. Biodiversity equilibria in models occur due to the onset of ecological structural instability, a population-dynamical mechanism. This strongly suggests a causal link between local community processes and macroecological phenomena.

ecology↗