Microgeographical adaptation corresponds to elevational distributions of congeneric montane grasshoppers.

Local adaptation can occur at small spatial scales relative to the dispersal capacity of species. Alpine ecosystems have sharp environmental clines that offer an opportunity to investigate the effects of fine-scale shifts in species' niche breadth on adaptive genetic processes. Here we examine two grasshopper species endemic to the Australian Alps (Kosciuscola spp.) that differ in elevational niche breadth: one broader, K. usitatus (1400-2200 m), and one narrower, K. tristis (1600-2000 m). We examine signatures of selection with respect to environmental and morphological variables in two mountain regions using FST outlier tests and environmental association analyses (EAAs) applied to single nucleotide polymorphism (SNP) data (K. usitatus: 9017 SNPs, n = 130; K. tristis: 7363 SNPs, n = 135). Stronger genetic structure was found in the more narrowly distributed K. tristis, which showed almost twice the number of SNPs under putative selection (10.8%) compared with K. usitatus (5.3%). When examining SNPs in common across species (n = 3058), 260 SNPs (8.5%) were outliers shared across species, and these were mostly associated with elevation, a proxy for temperature, suggesting parallel adaptive processes in response to climatic drivers. Additive polygenic scores (an estimate of the cumulative signal of selection across all candidate loci) were nonlinearly and positively correlated with elevation in both species. However, a steeper correlation in K. tristis indicated a stronger signal of spatially varying selection towards higher elevations. Our study illustrates that the niche breadth of co-occurring and related species distributed along the same environmental cline is associated with differences in patterns of microgeographical adaptation.

Sperm Storage in a Family-Living Lizard, the Tree Skink (Egernia striolata).

The ability to produce viable offspring without recently mating, either through sperm storage or parthenogenesis, can provide fitness advantages under a suite of challenging ecological scenarios. Using genetic analysis, we demonstrate that 3 wild-caught female Tree Skinks (Egernia striolata) reproduced in captivity with no access to males for over a year, and that this is best explained by sperm storage. To the best of our knowledge, this is the first time female sperm storage has been documented in any monogamous family-living reptile, including social Australian egerniine skinks (from the subfamily Egerniinae). Furthermore, by using paternal reconstruction of genotypes we show that captive-born offspring produced by the same females in the preceding year, presumably without sperm storage, were sired by different males. We qualitatively compared aspects of these females' mates and offspring between years. The parents of each litter were unrelated, but paternal and offspring genotypes from litters resulting from stored sperm were more heterozygous than those inferred to be from recent matings. Family-living egerniine skinks generally have low rates of multiple paternity, yet our study suggests that female sperm storage, potentially from outside social partners, offers the real possibility of benefits. Possible benefits include increasing genetic compatibility of mates and avoiding inbreeding depression via cryptic female choice. Sperm storage in Tree Skinks, a family-living lizard with a monogamous mating system, suggests that females may bet-hedge through extra-pair copulation with more heterozygous males, reinforcing the idea that females could have more control on reproductive outcomes than previously thought.

The evolution of polymorphism in the warning coloration of the Amazonian poison frog Adelphobates galactonotus.

While intraspecific variation in aposematic signals can be selected for by different predatory responses, their evolution is also contingent on other processes shaping genetic variation. We evaluate the relative contributions of selection, geographic isolation, and random genetic drift to the evolution of aposematic color polymorphism in the poison frog Adelphobates galactonotus, distributed throughout eastern Brazilian Amazonia. Dorsal coloration was measured for 111 individuals and genetic data were obtained from 220 individuals at two mitochondrial genes (mtDNA) and 7963 Single Nucleotide Polymorphisms (SNPs). Four color categories were described (brown, blue, yellow, orange) and our models of frog and bird visual systems indicated that each color was distinguishable for these taxa. Using outlier and correlative analyses we found no compelling genetic evidence for color being under divergent selection. A time-calibrated mtDNA tree suggests that the present distribution of dorsal coloration resulted from processes occurring during the Pleistocene. Separate phylogenies based on SNPs and mtDNA resolved the same well supported clades, each containing different colored populations. Ancestral character state analysis provided some evidence for evolutionary transitions in color type. Genetic structure was more strongly associated with geographic features, than color category, suggesting that the distribution of color is explained by localized processes. Evidence for geographic isolation together with estimates of low effective population size implicates drift as playing a key role in color diversification. Our results highlight the relevance of considering the neutral processes involved with the evolution of traits with important fitness consequences.

The Influence of Environmental Variation on the Genetic Structure of a Poison Frog Distributed Across Continuous Amazonian Rainforest.

Biogeographic barriers such as rivers have been shown to shape spatial patterns of biodiversity in the Amazon basin, yet relatively little is known about the distribution of genetic variation across continuous rainforest. Here, we characterize the genetic structure of the brilliant-thighed poison frog (Allobates femoralis) across an 880-km-long transect along the Purus-Madeira interfluve south of the Amazon river, based on 64 individuals genotyped at 7609 single-nucleotide polymorphism (SNP) loci. A population tree and clustering analyses revealed 4 distinct genetic groups, one of which was strongly divergent. These genetic groups were concomitant with femoral spot coloration differences, which was intermediate within a zone of admixture between two of the groups. The location of these genetic groups did not consistently correspond to current ecological transitions between major forest types. A multimodel approach to quantify the relative influence of isolation-by-geographic distance (IBD) and isolation-by-environmental resistance (IBR) nevertheless revealed that, in addition to a strong signal of IBD, spatial genetic differentiation was explained by IBR primarily linked to dry season intensity (r2 = 8.4%) and canopy cover (r2 = 6.4%). We show significant phylogenetic divergence in the absence of obvious biogeographical barriers and that finer-scaled measures of genetic structure are associated with environmental variables also known to predict the density of A. femoralis.

Detection of environmental and morphological adaptation despite high landscape genetic connectivity in a pest grasshopper (Phaulacridium vittatum).

Widespread species that exhibit both high gene flow and the capacity to occupy heterogeneous environments make excellent models for examining local selection processes along environmental gradients. Here we evaluate the influence of temperature and landscape variables on genetic connectivity and signatures of local adaptation in Phaulacridium vittatum, a widespread agricultural pest grasshopper, endemic to Australia. With sampling across a 900-km latitudinal gradient, we genotyped 185 P. vittatum from 19 sites at 11,408 single nucleotide polymorphisms (SNPs) using ddRAD sequencing. Despite high gene flow across sites (pairwise FST  = 0.0003-0.08), landscape genetic resistance modelling identified a positive nonlinear effect of mean annual temperature on genetic connectivity. Urban areas and water bodies had a greater influence on genetic distance among sites than pasture, agricultural areas and forest. Together, FST outlier tests and environmental association analysis (EAA) detected 242 unique SNPs under putative selection, with the highest numbers associated with latitude, mean annual temperature and body size. A combination of landscape genetic connectivity analysis together with EAA identified mean annual temperature as a key driver of both neutral gene flow and environmental selection processes. Gene annotation of putatively adaptive SNPs matched with gene functions for olfaction, metabolic detoxification and ultraviolet light shielding. Our results imply that this widespread agricultural pest has the potential to spread and adapt under shifting temperature regimes and land cover change.

The search for loci under selection: trends, biases and progress.

Detecting genetic variants under selection using FST outlier analysis (OA) and environmental association analyses (EAAs) are popular approaches that provide insight into the genetic basis of local adaptation. Despite the frequent use of OA and EAA approaches and their increasing attractiveness for detecting signatures of selection, their application to field-based empirical data have not been synthesized. Here, we review 66 empirical studies that use Single Nucleotide Polymorphisms (SNPs) in OA and EAA. We report trends and biases across biological systems, sequencing methods, approaches, parameters, environmental variables and their influence on detecting signatures of selection. We found striking variability in both the use and reporting of environmental data and statistical parameters. For example, linkage disequilibrium among SNPs and numbers of unique SNP associations identified with EAA were rarely reported. The proportion of putatively adaptive SNPs detected varied widely among studies, and decreased with the number of SNPs analysed. We found that genomic sampling effort had a greater impact than biological sampling effort on the proportion of identified SNPs under selection. OA identified a higher proportion of outliers when more individuals were sampled, but this was not the case for EAA. To facilitate repeatability, interpretation and synthesis of studies detecting selection, we recommend that future studies consistently report geographical coordinates, environmental data, model parameters, linkage disequilibrium, and measures of genetic structure. Identifying standards for how OA and EAA studies are designed and reported will aid future transparency and comparability of SNP-based selection studies and help to progress landscape and evolutionary genomics.

Geographic vocal variation and perceptual discrimination abilities in male Australian sea lions.

Vocal characteristics can vary among and within populations. In species with geographic variation in the structure of vocalizations, individuals may have the ability to discriminate between calls from local and non-local individuals. The ability to distinguish differences in acoustic signals is likely to have a significant influence on the outcome of social interactions between individuals, including potentially mate selection and breeding success. Pinnipeds (seals, fur seals, sea lions and walruses) are highly vocal yet the Australian sea lion (Neophoca cinerea) is the only eared seal known to show geographic vocal variation in male barks. Barks are produced in many social interactions and encode sufficient information for both individual and colony identity to be discriminable. Yet until now, whether males could themselves discriminate these bark differences was unclear. We performed playback experiments in four breeding colonies to investigate whether males can discriminate local from non-local barks. Overall, males responded more strongly to barks from their own colony compared to barks from other colonies regardless of whether those other colonies were close or distant. Competition for females is high in Australian sea lions, but mating periods are asynchronous across colonies. The ability to correctly assess whether a male is from the same colony, thus representing a potential competitor for mates, or merely a visitor from elsewhere, may influence how males interact with others. Given the high cost of fighting, the ability to discern competitors may influence the nature of male-male interactions and ultimately influence how they allocate reproductive effort.

Under the weather?-The direct effects of climate warming on a threatened desert lizard are mediated by their activity phase and burrow system.

For ectotherms such as lizards, the importance of behavioural thermoregulation in avoiding thermal extremes is well-established and is increasingly acknowledged in modern studies of climate warming and its impacts. Less appreciated and understood are the buffering roles of retreat sites and activity phase, in part because of logistical challenges of studying below-ground activity. Burrowing and nocturnal activity are key behavioural adaptations that have enabled a diverse range of reptiles to survive extreme environmental temperatures within hot desert regions. Yet, the direct impact of recent global warming on activity potential has been hypothesised to have caused extinctions in desert lizards, including the Australian arid zone skink Liopholis kintorei. We test the relevance of this hypothesis through a detailed characterisation of the above- and below-ground thermal and hydric microclimates available to, and used by, L. kintorei. We integrate operative temperatures with observed body temperatures to construct daily activity budgets, including the inference of subterranean behaviour. We then assess the likelihood that contemporary and future local extinctions in this species, and those of similar burrowing habits, could be explained by the direct effects of warming on its activity budget and exposure to thermal extremes. We found that L. kintorei spent only 4% of its time active on the surface, primarily at dusk, and that overall potential surface activity will be increased, not restricted, with climate warming. The burrow system provides an exceptional buffer to current and future maximum extremes of temperature (≈40°C reduction from potential surface temperatures), and desiccation (burrows near 100% humidity). Therefore, any climate warming impacts on this species are likely to be indirect. Our findings reflect the general buffering capacity of underground microclimates, therefore, our conclusions for L. kintorei are more generally applicable to nocturnal and crepuscular ectotherms, and highlight the need to consider the buffering properties of retreat sites and activity phase when forecasting climate change impacts.

Morphological Variation Tracks Environmental Gradients in an Agricultural Pest, Phaulacridium vittatum (Orthoptera: Acrididae).

Invertebrate pests often show high morphological variation and wide environmental tolerances. Knowledge of how phenotypic variation is associated with environmental heterogeneity can elucidate the processes underpinning these patterns. Here we examine morphological variation and relative abundance along environmental gradients in a widespread agricultural pest, native to Australia, the wingless grasshopper Phaulacridium vittatum (Sjöstedt). We test for correlations between body size, wing presence, and stripe polymorphism with environmental variables. Using multiple regression and mixed-effects modeling, body size and stripe polymorphism were positively associated with solar radiation, and wing presence was positively associated with foliage projective cover (FPC). There were no associations between body size or morphological traits with relative abundance. However, relative abundance was positively associated with latitude, soil moisture, and wind speed, but was negatively associated with FPC. Therefore, sites with low relative abundance and high forest cover were more likely to contain winged individuals. Overall, our results suggest that environmental and climatic conditions strongly influence the relative abundance and the distribution of morphotypes in P. vittatum, which is likely to affect dispersal and fitness in different landscapes. This knowledge is useful for informing how environmental change might influence the future spread and impact of this agricultural pest.

Contrasting Patterns of Gene Flow for Amazonian Snakes That Actively Forage and Those That Wait in Ambush.

Knowledge of genetic structure, geographic distance and environmental heterogeneity can be used to identify environmental features and natural history traits that influence dispersal and gene flow. Foraging mode is a trait that might predict dispersal capacity in snakes, because actively foragers typically have greater movement rates than ambush predators. Here, we test the hypothesis that 2 actively foraging snakes have higher levels of gene flow than 2 ambush predators. We evaluated these 4 co-distributed species of snakes in the Brazilian Amazon. Snakes were sampled along an 880 km transect from the central to the southwest of the Amazon basin, which covered a mosaic of vegetation types and seasonal differences in climate. We analyzed thousands of single nucleotide polymorphisms to compare patterns of neutral gene flow based on isolation by geographic distance (IBD) and environmental resistance (IBR). We show that IBD and IBR were only evident in ambush predators, implying lower levels of dispersal than the active foragers. Therefore, gene flow was high enough in the active foragers analyzed here to prevent any build-up of spatial genotypic structure with respect to geographic distance and environmental heterogeneity.

Environmental DNA highlights the influence of salinity and agricultural run-off on coastal fish assemblages in the Great Barrier Reef region.

Agricultural run-off in Australia's Mackay-Whitsunday region is a major source of nutrient and pesticide pollution to coastal and inshore ecosystems of the Great Barrier Reef. While the effects of run-off are well documented for the region's coral and seagrass habitats, the ecological impacts on estuaries, the direct recipients of run-off, are less known. This is particularly true for fish communities, which are shaped by the physico-chemical properties of coastal waterways that vary greatly in tropical regions. To address this knowledge gap, we used environmental DNA (eDNA) metabarcoding to examine fish assemblages at four locations (three estuaries and a harbour) subjected to varying levels of agricultural run-off during a wet and dry season. Pesticide and nutrient concentrations were markedly elevated during the sampled wet season with the influx of freshwater and agricultural run-off. Fish taxa richness significantly decreased in all three estuaries (F = 164.73, P = <0.001), along with pronounced changes in community composition (F = 46.68, P = 0.001) associated with environmental variables (largely salinity: 27.48% contribution to total variance). In contrast, the nearby Mackay Harbour exhibited a far more stable community structure, with no marked changes in fish assemblages observed between the sampled seasons. Among the four sampled locations, variation in fish community composition was more pronounced within the wet season (F = 2.5, P = 0.001). Notably, variation in the wet season was significantly correlated with agricultural contaminants (phosphorus: 6.25%, pesticides: 5.22%) alongside environmental variables (salinity: 5.61%, DOC: 5.57%). Historically contaminated and relatively unimpacted estuaries each demonstrated distinct fish communities, reflecting their associated catchment use. Our findings emphasise that while seasonal effects play a key role in shaping the community structure of fish in this region, agricultural contaminants are also important contributors in estuarine systems.

Bat species assemblage predicts coronavirus prevalence.

Anthropogenic disturbances and the subsequent loss of biodiversity are altering species abundances and communities. Since species vary in their pathogen competence, spatio-temporal changes in host assemblages may lead to changes in disease dynamics. We explore how longitudinal changes in bat species assemblages affect the disease dynamics of coronaviruses (CoVs) in more than 2300 cave-dwelling bats captured over two years from five caves in Ghana. This reveals uneven CoV infection patterns between closely related species, with the alpha-CoV 229E-like and SARS-related beta-CoV 2b emerging as multi-host pathogens. Prevalence and infection likelihood for both phylogenetically distinct CoVs is influenced by the abundance of competent species and naïve subadults. Broadly, bat species vary in CoV competence, and highly competent species are more common in less diverse communities, leading to increased CoV prevalence in less diverse bat assemblages. In line with the One Health framework, our work supports the notion that biodiversity conservation may be the most proactive measure to prevent the spread of pathogens with zoonotic potential.

Frequency of multiple paternity in gummy shark, Mustelus antarcticus, and rig, Mustelus lenticulatus, and the implications of mate encounter rate, postcopulatory influences, and reproductive mode.

Elasmobranchs (sharks and rays) show an amazing diversity of reproductive modes and behaviors. Multiple paternity (MP) has been identified in all species where more than 1 litter has been investigated; yet neither direct nor indirect benefits from MP have been determined in elasmobranchs. This has led to the suggestion that MP in this group may simply be a product of convenience polyandry with variation in the frequency of MP driven by differences in mate encounter rates. Here, we use molecular markers to investigate polyandry and MP in 2 closely related and commercially important species of shark, Mustelus antarcticus and Mustelus lenticulatus. In total, 328 M. antarcticus embryos originating from 29 different mothers and 75 M. lenticulatus embryos originating from 19 different mothers were genotyped using 8 microsatellite loci. We find that MP occurs in both species. However, in both species, the majority of litters were sired by a single father. Our results do not support increased fecundity per se as a driver of MP. Further, our results do not suggest that high population densities with resulting high mate encounter rates generated by breeding aggregations necessarily lead to high frequencies of MP. Importantly, we note evidence of reproductive skew within polyandrous litters, which is a predicted outcome of postcopulatory mechanisms.

Genetic divergence, speciation and biogeography of Mustelus (sharks) in the central Indo-Pacific and Australasia.

The shark genus Mustelus is speciose, commercially important and systematically troublesome. We use a molecular approach combining inter and intra-specific data to investigate Mustelus species in the central Indo-Pacific and Australasia. Our analysis supports two Mustelus clades, one comprising species with no white spots and a placental reproductive mode and a second clade of white spotted, aplacental species. Levels of genetic divergence are low, especially among species in the white spotted, aplacental clade and this should be taken into account when employing molecular data to delineate species. Our data support the hypothesis of a radiation following dispersal from a northern hemisphere ancestor. Molecular dating suggests that localised speciation in Australasia may have occurred during the Pleistocene. We propose that some of the difficulties associated with Mustelus systematics relate to a recent radiation, particularly in the Australasian region.

Antimicrobial strength increases with group size: implications for social evolution.

We hypothesize that aggregations of animals are likely to attract pathogenic micro-organisms and that this is especially the case for semisocial and eusocial insects where selection ultimately led to group sizes in the thousands or even millions, attracting the epithet 'superorganism'. Here, we analyse antimicrobial strength, per individual, in eight thrips species (Insecta: Thysanoptera) that present increasing innate group sizes and show that species with the largest group size (100-700) had the strongest antimicrobials, those with smaller groups (10-80) had lower antimicrobial activity, while solitary species showed none. Species with large innate group sizes showed strong antimicrobial activity while the semisocial species showed no activity until group size increased sufficiently to make activity detectable. The eusocial species behaved in a similar way, with detectable activity appearing once group size exceeded 120. These analyses show that antimicrobial strength is determined by innate group size. This suggests that the evolution of sociality that, by definition, increases group size, may have had particular requirements for defences against microbial pathogens. Thus, increase in group size, accompanied by increased antibiotic strength, may have been a critical factor determining the 'point of no return', early in the evolution of social insects, beyond which the evolution of social anatomical and morphological traits was irreversible. Our data suggest that traits that increase group size in general are accompanied by increased antimicrobial strength and that this was critical for transitions from solitary to social and eusocial organization.

Social Barriers in Ecological Landscapes: The Social Resistance Hypothesis.

Across animal societies, individuals invest time and energy in social interactions. The social landscape that emerges from these interactions can then generate barriers that limit the ability of individuals to disperse to, and reproduce in, groups or populations. Therefore, social barriers can contribute to the difference between the physical capacity for movement through the habitat and subsequent gene flow. We call this contributing effect 'social resistance'. We propose that social resistance can act as an agent of selection on key life-history strategies and promote the evolution of social strategies that facilitate effective dispersal. By linking landscape genetics and social behaviour, the social resistance hypothesis generates predictions integrating dispersal, connectivity, and life-history evolution.

Conservation prioritization can resolve the flagship species conundrum.

Conservation strategies based on charismatic flagship species, such as tigers, lions, and elephants, successfully attract funding from individuals and corporate donors. However, critics of this species-focused approach argue it wastes resources and often does not benefit broader biodiversity. If true, then the best way of raising conservation funds excludes the best way of spending it. Here we show that this conundrum can be resolved, and that the flagship species approach does not impede cost-effective conservation. Through a tailored prioritization approach, we identify places containing flagship species while also maximizing global biodiversity representation (based on 19,616 terrestrial and freshwater species). We then compare these results to scenarios that only maximized biodiversity representation, and demonstrate that our flagship-based approach achieves 79-89% of our objective. This provides strong evidence that prudently selected flagships can both raise funds for conservation and help target where these resources are best spent to conserve biodiversity.

Chemical and genetic defenses against disease in insect societies.

The colonies of ants, bees, wasps and termites, the social insects, consist of large numbers of closely related individuals; circumstances ideal for contagious diseases. Antimicrobial assays of these animals have demonstrated a wide variety of chemical defenses against both bacteria and fungi that can be broadly classified as either external antiseptic compounds or internal immune molecules. Reducing the disease risks inherent in colonies of social insects is also achieved by behaviors, such as multiple mating or dispersal, that lower genetic relatedness both within- and among colonies. The interactions between social insects and their pathogens are complex, as illustrated by some ants that require antimicrobial and behavioral defenses against highly specialized fungi, such as those in the genus Cordyceps that attack larvae and adults and species in the genus Escovopsis that attack their food supplies. Studies of these defenses, especially in ants, have revealed remarkably sophisticated immune systems, including peptides induced by, and specific to, individual bacterial strains. The latter may be the result of the recruitment by the ants of antibiotic-producing bacteria but the extent of such three-way interactions remains unknown. There is strong experimental evidence that the evolution of sociality required dramatic increases in antimicrobial defenses and that microbes have been powerful selective agents. The antimicrobial chemicals and the insect-killing fungi may be useful in medicine and agriculture, respectively.

An enhanced miniaturized assay for antimicrobial prospecting.

Bioprospecting for novel antimicrobials increasingly relies on extremely small samples unsuitable for conventional bulk extraction and assay. We developed a microtitre plate assay for minimal amounts of test materials which is rapid, extremely sensitive, allows time-course analysis and reduces false negatives. Developed for the analyses of antimicrobial sensitivity and resistance, the technique is appropriate for assays where source materials are scarce.

Monogamous sperm storage and permanent worker sterility in a long-lived ambrosia beetle.

The lifetime monogamy hypothesis claims that the evolution of permanently unmated worker castes always requires maximal full-sibling relatedness to be established first. The long-lived diploid ambrosia beetle Austroplatypus incompertus (Schedl) is known to be highly social, but whether it has lifetime sterile castes has remained unclear. Here we show that the gallery systems of this beetle inside the heartwood of live Eucalyptus trees are always inhabited by a single core family, consisting of a lifetime-inseminated mother, permanently unmated daughter workers, and immatures that are always full siblings to each other and their adult caretakers. Overall sex ratios are even. Males always disperse and only survive as stored sperm, but female offspring either disperse to mate and found their own colony or assume unmated worker roles, probably surviving for many years without any reproductive potential because tarsal loss precludes later dispersal. A well-supported Platypodinae phylogeny has allowed us to infer that parental monogamy evolved before a lifetime-unmated worker caste emerged, confirming the prediction that monogamy and full-sibling relatedness are necessary conditions for the evolution of such workers. The initially very challenging but ultimately long-term stable nesting habitat in live trees appears to have provided the crucial benefit/cost factor for maintaining selection for permanently sterile workers after strict monogamy and lifetime sperm storage had become established in this curculionid coleopteran lineage.