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The genic capture hypothesis, where sexually selected traits capture genetic variation in condition and the condition reflects genome-wide mutation load, stands to explain the presence of abundant genetic variation underlying sexually selected traits. Here we test this hypothesis by applying bidirectional selection to male mating success for 14 generations in replicate populations of Drosophila melanogaster . We then resequenced the genomes of flies from each population. Consistent with the central predictions of the genic capture hypothesis, we show that genetic variance decreased with success selection and increased with failure selection, providing evidence for purifying sexual selection. This pattern was distributed across the genome and no consistent molecular pathways were associated with divergence, consistent with condition being the target of selection. Together, our results provide molecular evidence suggesting that strong sexual selection erodes genetic variation, and that genome-wide mutation-selection balance contributes to its maintenance. Females are choosy about their mates, which should erode genetic diversity but in practice does not. Here, selection and genomic resequencing of Drosophila supports the hypothesis that this paradox can be explained by sexually selected traits reflecting genetic variation in condition.

Little is known about the extent of genetic connectivity along continuous coastlines in manta rays, or whether site visitation is influenced by relatedness. Such information is pertinent to defining population boundaries and understanding localized dispersal patterns and behaviour. Here, we use 3057 genome-wide single-nucleotide polymorphisms (SNPs) to evaluate population genetic structure and assess the levels of relatedness at aggregation sites of reef manta rays (Mobula alfredi) in southern Mozambique (n = 114). Contrary to indications of limited dispersal along the southern Mozambican coastline inferred from photo-identification and telemetry studies, our results show no evidence of population structure (non-significant FST < 0.001) for M. alfredi along this coast. We also found no evidence that individuals sampled at the same site were more related than expected by chance for males, females or across both sexes, suggesting that kinship may not influence visitation patterns at these sites. We estimated the effective population size (Ne) of this population to be 375 (95% CI = 369–380). Comparison to a distant eastern Indian Ocean site (Western Australia, n = 15) revealed strong genetic differentiation between Mozambique and Western Australia (FST = 0.377), identifying the Indian Ocean basin as a barrier to dispersal. Our findings show that genetic connectivity in M. alfredi extends for several hundred kilometres along continuous coastlines. We therefore recommend that the population in Mozambique be considered a discrete management unit, and future conservation plans should prioritize integrated strategies along the entire southern coastline.

Understanding the genetic basis of reproductive isolation is a long-standing goal of speciation research. In recently diverged populations, genealogical discordance may reveal genes and genomic regions that contribute to the speciation process. Previous work has shown that conspecific colonies of Acropora that spawn in different seasons (spring and autumn) are associated with highly diverged lineages of the phylogenetic marker PaxC. Here, we used 10 034 single-nucleotide polymorphisms to generate a genome-wide phylogeny and compared it with gene genealogies from the PaxC intron and the mtDNA Control Region in 20 species of Acropora, including three species with spring- and autumn-spawning cohorts. The PaxC phylogeny separated conspecific autumn and spring spawners into different genetic clusters in all three species; however, this pattern was not supported in two of the three species at the genome level, suggesting a selective connection between PaxC and reproductive timing in Acropora corals. This genome-wide phylogeny provides an improved foundation for resolving phylogenetic relationships in Acropora and, combined with PaxC, provides a fascinating platform for future research into regions of the genome that influence reproductive isolation and speciation in corals.

A detailed understanding of the genetic structure of populations and an accurate interpretation of processes driving contemporary patterns of gene flow are fundamental to successful spatial conservation management. The field of seascape genetics seeks to incorporate environmental variables and processes into analyses of population genetic data to improve our understanding of forces driving genetic divergence in the marine environment. Information about barriers to gene flow (such as ocean currents) is used to define a resistance surface to predict the spatial genetic structure of populations and explain deviations from the widely applied isolation-by-distance model. The majority of seascape approaches to date have been applied to linear coastal systems or at large spatial scales (more than 250 km), with very few applied to complex systems at regional spatial scales (less than 100 km). Here, we apply a seascape genetics approach to a peripheral population of the broadcast-spawning coral Acropora spicifera across the Houtman Abrolhos Islands, a high-latitude complex coral reef system off the central coast of Western Australia. We coupled population genetic data from a panel of microsatellite DNA markers with a biophysical dispersal model to test whether oceanographic processes could explain patterns of genetic divergence. We identified significant variation in allele frequencies over distances of less than 10 km, with significant differentiation occurring between adjacent sites but not between the most geographically distant ones. Recruitment probabilities between sites based on simulated larval dispersal were projected into a measure of resistance to connectivity that was significantly correlated with patterns of genetic divergence, demonstrating that patterns of spatial genetic structure are a function of restrictions to gene flow imposed by oceanographic currents. This study advances our understanding of the role of larval dispersal on the fine-scale genetic structure of coral populations across a complex island system and applies a methodological framework that can be tailored to suit a variety of marine organisms with a range of life-history characteristics.

The degree of connectivity across ecosystems is a key determinant of resilience, directly influencing recovery potential after disturbance and long‐term ecosystem stability. In reef‐building corals, there is added complexity to these processes because both the coral host and their symbiotic dinoflagellates determine resilience. Given these complexities, we investigated the connectivity of a broadcast spawning coral and its associated algal symbiont communities along the Ningaloo Reef Marine Park and Muiron Island Management Area. Using reduced representation sequencing and DNA metabarcoding in 158 colonies of Acropora cf. tenuis across 14 sampling sites, we detected significant spatial genetic structure in the coral host consistent with a pattern of isolation by distance (IBD). Spatial Autocorrelation analyses revealed that the genetic neighbourhood extends up to 50 km suggesting that this coral species has multiple demographically independent populations across Ningaloo Reef. Symbiont communities were dominated by Cladocopium and followed a similar IBD pattern of between‐site differences in community composition. We did not identify a significant correlation between host genetic diversity and symbiont community diversity at the colony level. However, spatial patterns of genetic differentiation between sample sites for the host and symbiont community composition were significantly associated suggesting that connectivity along a fringing reef system for both coral hosts and their symbionts is driven by similar biogeographic factors. We explored fine‐scale patterns of connectivity and symbiont associations across the Ningaloo reefscape to inform on post‐disturbance recovery, larval dispersal capabilities, and recruitment dynamics. We detected low but significant population genetic structure among sample sites spread across Ningaloo Reef with the highest diversity in southern sites. There is substantial evidence of isolation by distance, with an increasing signal of genetic differentiation with increasing geographic distance between sites. Interestingly, symbiont ITS2 metabarcoding revealed a positive association between coral genetic differentiation and symbiont community dissimilarity across sites, indicating that both are structured by shared biogeographic drivers.

Translocated populations must adapt to their new environment to survive. A key aspect of survival for insects is the maintenance of water balance. It is thought that insects can adapt to dry environments by adjusting their cuticular hydrocarbon (CHC) profile to reduce water loss, though there is limited empirical support for this, and studies generally focus on other roles of CHCs, such as chemical communication. We tested for phenotypic adaptation in introduced populations of the Mediterranean dung beetle Onthophagus taurus, which have become established along a climatic gradient from dry northern to wet southern locations in southwestern Australia. We compared CHC profiles and desiccation resistance between northern and southern populations of the species. To quantify desiccation resistance, we measured both the rate of weight loss and time until death in beetles incubated at 35 °C. We tested for associations between these measures of desiccation resistance and CHC profiles, which were obtained through gas chromatography mass spectrometry. The abundance of CHCs was positively associated with desiccation resistance, and individuals that underwent the desiccation treatment produced a greater quantity of several CHC compounds indicating their ability to plastically adjust their CHC profile in response to desiccation stress. However, northern populations did not produce more CHCs than southern populations, and southern populations were better able to tolerate desiccation. Our results suggest that CHCs are an important component of desiccation resistance in O. taurus. However, the lack of evidence for local adaptation to the drier northern climate suggests there may be constraints to increasing desiccation resistance, and demonstrates the importance of considering local environmental conditions before translocating populations to new locations.

Species translocations are increasingly being used in conservation and for biological control. The success of a translocation can be strongly influenced by the evolutionary processes occurring during the early phase of the introduction and the subsequent spread to new regions. In this study, morphological variation and population genetic structure were assessed in the African dung beetle Digitonthophagus gazella, a species that was intentionally introduced to Australia for biological control in 1968 and subsequently spread widely across the northern part of the continent. A dataset based on 1594 neutral single nucleotide polymorphism (SNP) loci that were genotyped in 187 individuals from 12 sites revealed significant genetic divergences between sites (global FST = 0.118) and provides evidence of restricted gene flow among established populations at small to moderate spatial scales (74–500 km). Geometric morphometric analyses revealed significant divergence among populations in the shape of the foretibia, a trait ecologically important for tunnelling in soil and dung. Moreover, phenotypic divergence in this trait for both sexes was significantly higher than genetic differentiation at selectively neutral loci (PST > FST), suggesting that directional selection is contributing to the phenotypic divergences among populations. Our study shows how population structure can establish quickly in an introduced species and highlights the importance of considering local adaptation when performing translocations on established populations. Species translocations for conservation and biological control can be influenced by evolutionary processes occurring during the initial introduction and subsequent spread. This study assessed the morphological variation and population genetic structure of the African dung beetle, Digitonthophagus gazella, introduced to Australia in 1968, using data from 1594 SNP loci genotyped in 187 individuals from 12 sites. The findings revealed significant genetic divergence and restricted gene flow among populations, as well as significant phenotypic divergence in a key morphological trait due to directional selection, emphasising the importance of local adaptation in translocation efforts.

Physiological plasticity is fundamental for resisting environmental change. As climate change accelerates and environmental stressors become more frequent, understanding how habitat‐forming species shift their physiology to match their environment is essential for predicting broader ecosystem responses. In this study, we examined whether prior exposure to sub‐bleaching heat stress influenced the gene expression responses to a subsequent thermal challenge in a common reef‐building coral. We primed Acropora corals from the World Heritage‐listed Ningaloo Reef (WHNR) to acute (24 h) sub‐bleaching temperatures (+5°C from the mean monthly maximum MMM, 32°C) before subjecting them to a more intense thermal challenge (+6°C from MMM, 33°C), and assessed the physiological and transcriptional responses in both naïve (no prior preconditioning) and primed corals compared to controls. Both groups mounted large gene expression responses to heat stress (33°C), which returned to baseline after a recovery period (16 h) at control temperatures (27°C, MMM), with no visible signs of physiological stress. However, primed corals showed a dampened stress response relative to naïve corals, marked by a 28% decline in differentially expressed genes and an overall reduction in intensity of expression of those genes compared to controls. Similar patterns were observed in the symbiotic partners, which showed a dampened response within the primed corals compared to the controls, despite no detectable declines in photosynthetic performance within either treatment. Our results show that short‐term preconditioning of corals is associated with transcriptional dampening of key stress response genes, and that corals are capable of rapid transcriptional recovery and resilience to recurrent heat stress. (a) Experimental design. Corals from 10 genotypes were distributed across two experimental blocks, each containing nine flow‐through tanks. Fragments from five genotypes were placed in each tank. (b) Temperature profiles and sampling time points in the heat stress assay, demonstrating ramp up from control conditions (27ºC, MMM) to the preconditioning treatment (33ºC) and the thermal challenge treatment (34ºC). Naïve treatment is shown in orange, the primed treatment in red and the control in blue. Sampling time points are indicated with dashed vertical lines: ‘T1’ represents the start of the thermal challenge, ‘T2’ represents the end of the heating hold and ‘T3’ represents the end of the recovery period. A single replicate tank of each temperature treatment (containing 5 colony fragments) from each experimental block (n = 2) was sampled at each time point.

Intraspecific colour polymorphisms have been the focus of numerous studies, yet processes affecting melanism in the marine environment remain poorly understood. Arguably, the most prominent example of melanism in marine species occurs in manta rays (Mobula birostris and Mobula alfredi). Here, we use long-term photo identification catalogues to document the frequency variation of melanism across Indo-Pacific manta ray populations and test for evidence of selection by predation acting on colour morph variants. We use mark–recapture modelling to compare survivorship of typical and melanistic colour morphs in three M. alfredi populations and assess the relationship between frequency variation and geographical distance. While there were large differences in melanism frequencies among populations of both species (0–40.70%), apparent survival estimates revealed no difference in survivorship between colour morphs. We found a significant association between phenotypic and geographical distance in M. birostris, but not in M. alfredi. Our results suggest that melanism is not under selection by predation in the tested M. alfredi populations, and that frequency differences across populations of both species are a consequence of neutral genetic processes. As genetic colour polymorphisms are often subjected to complex selection mechanisms, our findings only begin to elucidate the underlying evolutionary processes responsible for the maintenance and frequency variation of melanism in manta ray populations.

Translocating individuals from multiple source populations is one way to bolster genetic variation and avoid inbreeding in newly established populations. However, mixing isolated populations, especially from islands, can potentially lead to outbreeding depression and/or assortative mating, which may limit interbreeding between source populations. Here, we investigated genetic consequences of mixing individuals from two island populations of the dibbler (Parantechinus apicalis) in an island translocation. Despite a high level of genetic divergence between the source populations (FST ranges 0.33–0.64), and significant differences in body size, individuals with different ancestries were able to successfully interbreed in captivity and in the wild. However, the genetic contributions from each source population were unequal initially despite each of the source populations contributing an equal number of founders. Mating success of captive animals based on the pedigree suggests that this bias toward one source population was due to founder mortality and the mating success of younger and heavier animals. Nevertheless, genetic contributions in the translocated population became equal over time with no parental purebreds, suggesting an extreme excess of hybrids across multiple years. While genetic variation in the translocated population was comparable or higher than the source populations, the increase was short‐lived. Genetic composition of captive animals may not reflect what happens in the wild. These changes post‐translocation highlight the need for continued genetic monitoring.