Gene Flow Disruption and Population Declines in a Soil Arthropod in Fragmented Habitats.

The intensification of land use over past millennia has accelerated habitat loss and fragmentation. This is hypothesized to lead to reductions in population sizes and restrictions in gene flow, processes that amplify genetic drift with profound negative impacts on species and populations. However, empirical data on the population genetic impacts of habitat fragmentation remain limited, particularly for presumed abundant species such as insects.

Perspectives on mating-system evolution: comparing concepts in plants and animals.

The study of mating systems, defined as the distribution of who mates with whom and how often in a sexually reproducing population, forms a core pillar of evolution research due to their effects on many evolutionary phenomena. Historically, the "mating system" has either been used to refer to the rate of self-fertilization or to the formation of mating pairs between individuals of distinct sexes. Consequently, these two types of mating systems have tended to be studied separately rather than jointly.

The genomic consequences and persistence of sociality in spiders.

In cooperatively breeding social animals, a few individuals account for all reproduction. In some taxa, sociality is accompanied by a transition from outcrossing to inbreeding. In concert, these traits reduce effective population size, potentially rendering transitions to sociality "evolutionarily dead-ends.

A modified iChip for cultivation of bacteria in arid environments.

Antimicrobial resistance is an ever-increasing problem for human health, and with only a few novel antimicrobials discovered in recent decades, an extraordinary effort is needed to circumvent this crisis. A promising source of new microbial-derived antimicrobial compounds resides in the large fraction of microbes that are not readily cultured by standard cultivation. It has previously been shown that nests of the social spider contain a diverse bacterial community, where only a small fraction of the microbes could be recovered by standard cultivation.

Exploring changes in social spider DNA methylation profiles in all cytosine contexts following infection.

Living at high density and with low genetic diversity are factors that should both increase the susceptibility of organisms to disease. Therefore, group living organisms, especially those that are inbred, should be especially vulnerable to infection and therefore have particular strategies to cope with infection. Phenotypic plasticity, underpinned by epigenetic changes, could allow group living organisms to rapidly respond to infection challenges.

The relationship between neutral genetic diversity and performance in wild arthropod populations.

Larger effective populations (Ne) are characterized by higher genetic diversity, which is expected to predict population performance (average individual performance that influences fitness). Empirical studies of the relationship between neutral diversity and performance mostly represent species with small Ne, while there is limited data from the species-rich and ecologically important arthropods that are assumed to have large Ne but are threatened by massive declines. We performed a systematic literature search and used meta-analytical models to test the prediction of a positive association between neutral genetic diversity and performance in wild arthropods.

Molecular Mechanisms of Temperature Tolerance Plasticity in an Arthropod.

How species thrive in a wide range of environments is a major focus of evolutionary biology. For many species, limited genetic diversity or gene flow among habitats means that phenotypic plasticity must play an important role in their capacity to tolerate environmental heterogeneity and to colonize new habitats. However, we have a limited understanding of the molecular components that govern plasticity in ecologically relevant phenotypes.

Impact of pre-copulatory sexual cannibalism on genetic diversity and efficacy of selection.

Factors that increase reproductive variance among individuals act to reduce effective population size (Ne), which accelerates the loss of genetic diversity and decreases the efficacy of purifying selection. These factors include sexual cannibalism, offspring investment and mating system. Pre-copulatory sexual cannibalism, where the female consumes the male prior to mating, exacerbates this effect.

Does ecological drift explain variation in microbiome composition among groups in a social host species?

Within a given species, considerable inter-individual, spatial, and temporal variation in the composition of the host microbiome exists. In group-living animals, social interactions homogenize microbiome composition among group members, nevertheless divergence in microbiome composition among related groups arise. Such variation can result from deterministic and stochastic processes.

Social transmission of bacterial symbionts homogenizes the microbiome within and across generations of group-living spiders.

Disentangling modes and fidelity of symbiont transmission are key for understanding host-symbiont associations in wild populations. In group-living animals, social transmission may evolve to ensure high-fidelity transmission of symbionts, since non-reproducing helpers constitute a dead-end for vertical transmission. We investigated symbiont transmission in the social spider Stegodyphus dumicola, which lives in family groups where the majority of females are non-reproducing helpers, females feed offspring by regurgitation, and individuals feed communally on insect prey.

Impaired immune function accompanies social evolution in spiders.

An efficient immune system is essential to the survival of many animals. Sociality increases risk of pathogen transmission, which should select for enhanced immune function. However, two hypotheses instead predict a weakened immune function: relaxed selection caused by social immunity/protection, and reduced efficacy of selection due to inbreeding, reproductive skew and female bias in social species that reduce effective population size and accelerate genetic drift.

Eco-evolutionary extinction and recolonization dynamics reduce genetic load and increase time to extinction in highly inbred populations.

Understanding how genetic and ecological effects can interact to shape genetic loads within and across local populations is key to understanding ongoing persistence of systems that should otherwise be susceptible to extinction through mutational meltdown. Classic theory predicts short persistence times for metapopulations comprising small local populations with low connectivity, due to accumulation of deleterious mutations. Yet, some such systems have persisted over evolutionary time, implying the existence of mechanisms that allow metapopulations to avoid mutational meltdown.

Adapting to climate with limited genetic diversity: Nucleotide, DNA methylation and microbiome variation among populations of the social spider Stegodyphus dumicola.

Understanding the role of genetic and nongenetic variants in modulating phenotypes is central to our knowledge of adaptive responses to local conditions and environmental change, particularly in species with such low population genetic diversity that it is likely to limit their evolutionary potential. A first step towards uncovering the molecular mechanisms underlying population-specific responses to the environment is to carry out environmental association studies. We associated climatic variation with genetic, epigenetic and microbiome variation in populations of a social spider with extremely low standing genetic diversity.

Antimicrobial volatiles emitted by members of the nest microbiome of social spiders.

Microbes produce and respond to a range of structurally and functionally diverse volatiles. Many microbial volatiles have antimicrobial properties. Since volatiles can diffuse through complex 3D systems like spider nests, they are promising pathogen protection for social arthropods.

The role of inter-individual intolerance in group cohesion and the transition to sociality in spiders.

Conspecific tolerance is key for maintaining group cohesion in animals. Understanding shifts from conspecific tolerance to intolerance is therefore important for understanding transitions to sociality. Subsocial species disperse to a solitary lifestyle after a gregarious juvenile phase and display conspecific intolerance as adults as a mechanism to maintain a solitary living.

Sperm competition intensity affects sperm precedence patterns in a polyandrous gift-giving spider.

Sperm competition drives traits that enhance fertilization success. The amount of sperm transferred relative to competitors is key for attaining paternity. Female reproductive morphology and male mating order may also influence fertilization, however the outcome for sperm precedence under intense sperm competition remains poorly understood.

Temporal and spatial microbiome dynamics across natural populations of the social spider Stegodyphus dumicola.

Host-symbiont interactions may form obligatory or facultative associations that are context dependent. Long-term studies on microbiome composition from wild populations should assess the temporal and spatial dynamics of host-microbe associations. We characterized the temporal and spatial variation in the bacterial microbiome composition in six populations of the social spider Stegodyphus dumicola for 2.

Host Plant Availability and Nest-Site Selection of the Social Spider Pocock, 1898 (Eresidae).

An animals' habitat defines the resources that are available for its use, such as host plants or food sources, and the use of these resources are critical for optimizing fitness. Spiders are abundant in all terrestrial habitats and are often associated with vegetation, which may provide structure for anchoring capture webs, attract insect prey, or provide protective function. Social spiders construct sedentary communal silk nests on host plants, but we know little about whether and how they make nest-site decisions.

Avoiding the tragedy of the commons: Improved group-feeding performance in kin groups maintains foraging cooperation in subsocial Stegodyphus africanus spiders (Araneae, Eresidae).

Cooperation involving shared resource systems is prone to 'the tragedy of the commons', where individuals act in their own self-interest to exploit the resource in a manner that is detrimental to the common good of all group members. Directing cooperation towards kin provides a solution to this problem and predicts the differential performance depending on the relatedness of group members. In subsocial spiders, juveniles live in transient groups that cooperate in hunting and communal feeding.

Macronutrient niches and field limitation in a woodland assemblage of harvestmen.

Description of animals' trophic niches helps us understand interactions between species in biological communities that are not easily observed. Analyses of macronutrient niches, that is, the range of macronutrient (protein:lipid:carbohydrate) ratios selected by generalist feeders, may be a useful alternative approach to inter-species comparisons of diets, especially within taxonomic assemblages of predators where species with similar nutritional requirements are likely to accept similar types of prey. Here we analysed the macronutritional niches of a woodland assemblage of seven harvestman species, all supposed to be predators with omnivorous tendencies.

The myth of antibiotic spider silk.

Spider silk is frequently attributed antimicrobial properties. This notion is based on studies reporting antimicrobial activity (AMA) of spider silk; however, close inspection of these studies reveals that the evidence is conflicting, and at best anecdotal. We performed a systematic study of antimicrobial properties of different silk types from seven species across the spider phylogeny.

Antimicrobial Compounds in the Volatilome of Social Spider Communities.

Social arthropods such as termites, ants, and bees are among others the most successful animal groups on earth. However, social arthropods face an elevated risk of infections due to the dense colony structure, which facilitates pathogen transmission. An interesting hypothesis is that social arthropods are protected by chemical compounds produced by the arthropods themselves, microbial symbionts, or plants they associate with.

Evidence for genetic isolation and local adaptation in the field cricket Gryllus campestris.

Understanding how species can thrive in a range of environments is a central challenge for evolutionary ecology. There is strong evidence for local adaptation along large-scale ecological clines in insects. However, potential adaptation among neighbouring populations differing in their environment has been studied much less.

The bacterial and fungal nest microbiomes in populations of the social spider Stegodyphus dumicola.

Social spiders of the species Stegodyphus dumicola live in communal nests with hundreds of individuals and are characterized by extremely low species-wide genetic diversity. The lack of genetic diversity in combination with group living imposes a potential threat for infection by pathogens. We therefore proposed that specific microbial symbionts inhabiting the spider nests may provide antimicrobial defense.

An antimicrobial Staphylococcus sciuri with broad temperature and salt spectrum isolated from the surface of the African social spider, Stegodyphus dumicola.

Some social arthropods engage in mutualistic symbiosis with antimicrobial compound-producing microorganisms that provide protection against pathogens. Social spiders live in communal nests and contain specific endosymbionts with unknown function. Bacteria are also found on the spiders' surface, including prevalent staphylococci, which may have protective potential.