Analysis of ancestry heterozygosity suggests that hybrid incompatibilities in threespine stickleback are environment dependent

Hybrid incompatibilities occur when interactions between opposite ancestry alleles at different loci reduce the fitness of hybrids. Most work on incompatibilities has focused on those that are “intrinsic,” meaning they affect viability and sterility in the laboratory. Theory predicts that ecological selection can also underlie hybrid incompatibilities, but tests of this hypothesis using sequence data are scarce. In this article, we compiled genetic data for F2 hybrid crosses between divergent populations of threespine stickleback fish (Gasterosteus aculeatus L.) that were born and raised in either the field (seminatural experimental ponds) or the laboratory (aquaria). Because selection against incompatibilities results in elevated ancestry heterozygosity, we tested the prediction that ancestry heterozygosity will be higher in pond-raised fish compared to those raised in aquaria. We found that ancestry heterozygosity was elevated by approximately 3% in crosses raised in ponds compared to those raised in aquaria. Additional analyses support a phenotypic basis for incompatibility and suggest that environment-specific single-locus heterozygote advantage is not the cause of selection on ancestry heterozygosity. Our study provides evidence that, in stickleback, a coarse—albeit indirect—signal of environment-dependent hybrid incompatibility is reliably detectable and suggests that extrinsic incompatibilities can evolve before intrinsic incompatibilities.

Host exposure to symbionts and ecological drift generate divergence in parasite community assembly

The initial colonization of a host by symbionts, ranging from parasites to mutualists, can generate priority effects that alter within-host interactions and the trajectory of parasite community assembly. At the same time, variation in parasite communities among hosts can also stem from stochastic processes. Community ecology theory posits that multiple processes (e.g. dispersal, selection and drift) interact to generate variation in community structure, but these processes are rarely considered simultaneously during community assembly. To test the role of these processes in a parasite community, we experimentally simulated dispersal of three symbionts by factorially inoculating individual plants of tall fescue with two foliar fungal parasites, Colletotrichum cereale and Rhizoctonia solani, and a hypothesized mutualist endophyte, Epichloë coenophiala. We then tracked parasite infections longitudinally in the field. After the initial inoculations, hosts were exposed to a common pool of parasites in the field, which we expected to cause parasite communities to converge towards a similar community state. To test for convergence, we analyzed individual hosts parasite community trajectories in multivariate space. In contrast to our expectation, there was no signal of convergence. Instead, parasite community trajectories generally diverged over time between treatment groups and the magnitude of divergence depended on the symbiont species inoculated. Parasite communities of hosts that were inoculated with only the mutualist, Epichloë, showed significant trends of divergence relative to all other symbiont inoculation treatments. In contrast, hosts inoculated with only Rhizoctonia did not exhibit clear trends of divergence when compared to other parasite inoculations. Further, co-inoculation with both parasite species resulted in faster rates of divergence and greater temporal change in parasite communities relative to hosts inoculated with only the parasite Colletotrichum. As predicted by existing theory, parasite communities showed evidence of drift during the beginning of the experiment, which contributed to among-host divergence in parasite community structure. Overall, these data provide evidence that initial dispersal of symbionts produced persistent changes in parasite community structure via ecological selection, that drift was important during the early stages of parasite community assembly, and together, dispersal, selection and drift resulted in parasite community divergence.

Microbiome stability and structure is governed by host phylogeny over diet and geography in woodrats (Neotoma spp.)

The microbiome is critical for host survival and fitness, but gaps remain in our understanding of how this symbiotic community is structured. Despite evidence that related hosts often harbor similar bacterial communities, it is unclear whether this pattern is due to genetic similarities between hosts or to common ecological selection pressures. Here, using herbivorous rodents in the genus Neotoma, we quantify how geography, diet, and host genetics, alongside neutral processes, influence microbiome structure and stability under natural and captive conditions. Using bacterial and plant metabarcoding, we first characterized dietary and microbiome compositions for animals from 25 populations, representing seven species from 19 sites across the southwestern United States. We then brought wild animals into captivity, reducing the influence of environmental variation. In nature, geography, diet, and phylogeny collectively explained ∼50% of observed microbiome variation. Diet and microbiome diversity were correlated, with different toxin-enriched diets selecting for distinct microbial symbionts. Although diet and geography influenced natural microbiome structure, the effects of host phylogeny were stronger for both wild and captive animals. In captivity, gut microbiomes were altered; however, responses were species specific, indicating again that host genetic background is the most significant predictor of microbiome composition and stability. In captivity, diet effects declined and the effects of host genetic similarity increased. By bridging a critical divide between studies in wild and captive animals, this work underscores the extent to which genetics shape microbiome structure and stability in closely related hosts.

Ecology dictates the value of memory for foraging bees

Summary“Ecological intelligence” hypotheses posit that the benefits of cognitive investment vary with foraging ecology, and provide a key framework for understanding the evolution of animal learning and memory1–4. However, although certain ecological selection pressures have been found to correlate with brain or neural region size5–8, empirical evidence to show that any specific cognitive trait is useful in certain environments but not others is currently lacking. Here, we assay the short-term memory of bumblebee (Bombus terrestris audax) workers from 25 identically reared colonies, before allowing each colony to forage in a landscape where forage availability varies seasonally. Through analysis of the bees’ lifetime foraging careers, comprising >1700 foraging trips over two years, we show that performance on a task designed to test short-term memory predicts individual foraging efficiency – a fitness proxy that is key to colony reproductive output – in plentiful spring foraging conditions. However, this relationship is reversed during the summer floral dearth, when the costs of cognitive investment may outweigh the benefits. Our results provide evidence that the value of a cognitive trait depends upon the prevailing ecological conditions and suggest that temporal changes in that environment could place contrasting selection pressures on memory within a single species.

Fundamentals for forage crop breeding and seed production in Russia

Plant breeding and seed production of new generation fodder crops is the groundwork for creating a fodder base for livestock production in sufficient quantities. The Federal Williams Research Center of Forage Production and Agroecology founded in 2018 based on of the All-Russia Williams Fodder Research Institute and other scientific institutions is the largest and most comprehensive center in the field of food production. It develops new techniques and methods for creating initial seed material based on a wide use of genetics, biotechnology, microbiology, immunology, ecology, biogeocenology, and cell selection. During the existence of the Fodder Research Institute and its experimental stations, up to 300 varieties of feed crops were created, which occupied leading positions in the production of fodder in meadows, pastures, and hayfields. Eighty-five modern varieties of fodder crops of the latest generation are widely used and zoned in all regions of Russia. However, the destroyed system of elite and commercial seed production does not allow these varieties to take their rightful place in fodder production, and the market still possesses a large share of non-varietal and mass scale reproduction seeds. In addition, imported seeds brought to the Russian market are often disguised as lawn varieties to reduce the cost and simplify their entry to the market. In this way, 107 varieties of winter ryegrass (Lolium perenne L.), 47 varieties of cane fescue (Festuca arundinacea Schreb.), 21 varieties of creeping clover (Trifolium repens L.), etc. appeared in Russia. In such circumstances, the attention of the Williams Center is focused on the development of techniques and methods for creating fundamentally new varieties based on its own research in genetics, biotechnology, immunology, and ecological selection. Much attention is paid to expanding the network of research stations throughout Russia in order to revive the system of elite seed growing, especially in the regions with the most favorable climate for growing seeds of particular crops. A seed production center was organized as a branch of the Williams Center at the end of 2020. In the future, it is planned to create a united coordinated interdepartmental complex for the breeding of fodder crops in accordance with the regional needs of animal husbandry.

Genetic evidence for environment-dependent hybrid incompatibilities in threespine stickleback

Hybrid incompatibilities occur when interactions between opposite-ancestry alleles at different loci reduce the fitness of hybrids. Most work on incompatibilities has focused on those that are 'intrinsic', meaning they affect viability and sterility in the laboratory. Theory predicts that ecological selection can also underlie hybrid incompatibilities, but tests of this hypothesis are scarce. In this article, we compiled genetic data for F2 hybrid crosses between divergent populations of threespine stickleback fish (Gasterosteus aculeatus L.) that were born and raised in either the field (semi-natural experimental ponds) or the laboratory (aquaria). We tested for differences in excess heterozygosity between these two environments at ancestry informative loci—a genetic signature of selection against incompatibilities. We found that excess ancestry heterozygosity was elevated by approximately 3% in crosses raised in ponds compared to those raised in aquaria. Previous results from F1 hybrids in the field suggest that pond-specific (single-locus) heterosis is unlikely to explain this finding. Our study suggests that, in stickleback, a coarse signal of environment-dependent hybrid incompatibilities is reliably detectable and that extrinsic incompatibilities have evolved before intrinsic incompatibilities.

Non-parallel morphological divergence following colonization of a new host plant

Divergent ecological selection may diversify populations of the same species evolving in different niches. However, for adaptation to result in speciation, the ecologically divergent populations have to experience at least some degree of reproductive isolation. While ecological selection pressures in similar environments are expected to result in convergent adaptation, sexually selected traits may diverge in different directions in different locations. Here, we use a host shift in the phytophagous peacock fly Tephritis conura, with both host races represented in two geographically separate areas, East and West of the Baltic Sea, to investigate convergence in morphological adaptations. We asked i) if there are consistent morphological adaptations to a host plant shift and ii) if the adaptations to secondary sympatry with the alternate host race are consistent across contact zones. We found low, albeit significant, divergence between host races, but only a few traits, including the female ovipositor, were consistently different. Interestingly, co-existence with the other host race significantly increased the degree of morphological divergence, but the patterns of divergence were not consistent across the two sympatric contact zones. Thus, local stochastic fixation or reinforcement could generate trait divergence, and evidence from additional sources is hence needed to conclude whether divergence is adaptive.

Dynamics of the Causes Of Crime: a Life-Course Application of Situational Action Theory for the Transition from Adolescence to Adulthood

Purpose According to the Developmental Ecological Action Model (DEA) of the situational action theory (SAT), changes in crime rates over the life-course are explained through personal (moral) maturation and socio-ecological selection. This assumption is empirically tested by comparing results for the conditioning effect of the principle of moral correspondence (as an essential part of SAT’s perception-choice process) on crime rates for the transition from adolescence to adulthood. Methods Comparing two waves of a German longitudinal study (CrimoC, 17 and 26 years old, n = 1738), a series of logistic and multinomial logistic regressions and ensuing estimated transition probabilities capture the cross-sectional but also developmental processes involved. Additionally, the CrimoC study offers a differential analysis of offending scales, separating offenses into youth and adult crimes. Results The principle’s conditioning effect on crime could be replicated at both times. We can observe a general trend of individual transitions, which correspond to predicted personal maturation and socio-ecological selection. The transitions correlate with the expected reduction in crime rates over time. Males and females show comparable results. The separation into different offending scales yielded tentative insights. Conclusion We found stability in the mechanisms leading to crime as proffered by SAT and DEA across time. Personal (moral) maturation and socio-ecological selection are likely to be the driving forces behind reducing crime in adulthood. Future research needs to explain in detail how life-course events influence these factors. Considering adult crimes in the analysis is a promising endeavor that warrants further investigation.

A new piece in the puzzle for the riverine slugs of the Acochlidiidae (Gastropoda: Panpulmonata: Acochlidimorpha) helps tracing steps of their freshwater invasion

Gastropods (slugs and snails) are prominent and species-rich faunal elements in marine and terrestrial habitats of the tropics. While several clades of snails inhabit freshwater systems, slugs are extremely rare in freshwater: only the centimeter-sized Acochlidiidae, with currently three genera, contain more than one species and live in the lower reaches of island streams in an area comprising Eastern Indonesia, Fiji, and Palau. Where known, the species of this unique group are specialized predators of other amphidromous snails’ egg capsules (Neritidae) and their reproductive biology and adaptations to life in freshwater are complex. Acochlidiidae are thus of special interest for evolutionary biology and ecology. We here describe a new genus of unusually bluish-green acochlidiid to date known only from a single locality on the island of Ambon, Indonesia. Previous molecular data found this charismatic species to link slender Strubellia slugs with broad and flattened Acochlidium and Palliohedyle. We establish Wallacellia siputbiru n. gen. n. sp., the “blue slug” in Bahasa Indonesia, by using scanning electron microscopy of cuticular elements, light microscopy of serial semithin histological sections of the soft body, and 3D reconstruction of all organ systems based on these sections. Special structures of this seemingly rare endemic species include the enlarged kidney and the huge copulatory organ. Our data now clarify that, in the invasion of freshwater habitats in Acochlidiidae, sexual selection (the anterior three-part copulatory organ) preceded ecological selection (posterior flattened habitus with branched or multiplied internal organs).