Parsing variance by marker type: Testing biogeographic hypotheses and differential contribution of historical processes to population structure in a desert lizard.

A fundamental goal of population genetic studies is to identify historical biogeographic patterns and understand the processes that generate them. However, localized demographic events can skew population genetic inference. Assessing populations with multiple types of genetic markers, each with unique mutation rates and responses to changes in population size, can help to identify potentially confounding population-specific demographic processes. Here, we compared population structure and connectivity inferred from microsatellites and restriction site-associated DNA loci among 17 populations of an arid-specialist lizard, the desert night lizard, Xantusia vigilis, in central California to test among historical processes structuring population genetic diversity. We found that both marker types yielded generally concordant insights into population genetic structure including a major phylogenetic break maintained between two populations separated by less than 10 km, suggesting that either marker type could be used to understand generalized demographic patterns across the region for management purposes. However, we also found that the effects of demography on marker discordance could be used to elucidate population histories and distinguish among competing biogeographic hypotheses. Our results suggest that comparisons of within-population diversity across marker types provide powerful opportunities for leveraging marker discordance, particularly for understanding the creation and maintenance of contact zones among clades.

Metabolically similar cohorts of bacteria exhibit strong cooccurrence patterns with diet items and eukaryotic microbes in lizard guts.

Gut microbiomes perform essential services for their hosts, including helping them to digest food and manage pathogens and parasites. Performing these services requires a diverse and constantly changing set of metabolic functions from the bacteria in the microbiome. The metabolic repertoire of the microbiome is ultimately dependent on the outcomes of the ecological interactions of its member microbes, as these interactions in part determine the taxonomic composition of the microbiome. The ecological processes that underpin the microbiome's ability to handle a variety of metabolic challenges might involve rapid turnover of the gut microbiome in response to new metabolic challenges, or it might entail maintaining sufficient diversity in the microbiome that any new metabolic demands can be met from an existing set of bacteria. To differentiate between these scenarios, we examine the gut bacteria and resident eukaryotes of two generalist-insectivore lizards, while simultaneously identifying the arthropod prey each lizard was digesting at the time of sampling. We find that the cohorts of bacteria that occur significantly more or less often than expected with arthropod diet items or eukaryotes include bacterial species that are highly similar to each other metabolically. This pattern in the bacterial microbiome could represent an early step in the taxonomic shifts in bacterial microbiome that occur when host lineages change their diet niche over evolutionary timescales.

Anolis lizards as biocontrol agents in mainland and island agroecosystems.

Our knowledge of ecological interactions that bolster ecosystem function and productivity has broad applications to the management of agricultural systems. Studies suggest that the presence of generalist predators in agricultural landscapes leads to a decrease in the abundance of herbivorous pests, but our understanding of how these interactions vary across taxa and along gradients of management intensity and eco-geographic space remains incomplete. In this study, we assessed the functional response and biocontrol potential of a highly ubiquitous insectivore (lizards in the genus Anolis) on the world's most important coffee pest, the coffee berry borer (Hypothalemus hampei). We conducted field surveys and laboratory experiments to examine the impact of land-use intensification on species richness and abundance of anoles and the capacity of anoles to reduce berry borer infestations in mainland and island coffee systems. Our results show that anoles significantly reduce coffee infestation rates in laboratory settings (Mexico, p = .03, F = 5.13 df = 1, 35; Puerto Rico, p = .014, F = 8.82, df = 1, 10) and are capable of consuming coffee berry borers in high abundance. Additionally, diversified agroecosystems bolster anole abundance, while high-intensity practices, including the reduction of vegetation complexity and the application of agrochemicals were associated with reduced anole abundance. The results of this study provide supporting evidence of the positive impact of generalist predators on the control of crop pests in agricultural landscapes, and the role of diversified agroecosystems in sustaining both functionally diverse communities and crop production in tropical agroecosystems.

From endogenous to exogenous pattern formation: Invasive plant species changes the spatial distribution of a native ant.

Invasive species are a significant threat to global biodiversity, but our understanding of how invasive species impact native communities across space and time remains limited. Based on observations in an old field in Southeast Michigan spanning 35 years, our study documents significant impacts of habitat change, likely driven by the invasion of the shrub, Elaeagnus umbellata, on the nest distribution patterns and population demographics of a native ant species, Formica obscuripes. Landcover change in aerial photographs indicates that E. umbellata expanded aggressively, transforming a large proportion of the original open field into dense shrubland. By comparing the ant's landcover preferences before and after the invasion, we demonstrate that this species experienced a significant unfavorable change in its foraging areas. We also find that shrub landcover significantly moderates aggression between nests, suggesting nests are more related where there is more E. umbellata. This may represent a shift in reproductive strategy from queen flights, reported in the past, to asexual nest budding. Our results suggest that E. umbellata may affect the spatial distribution of F. obscuripes by shifting the drivers of nest pattern formation from an endogenous process (queen flights), which led to a uniform pattern, to a process that is both endogenous (nest budding) and exogenous (loss of preferred habitat), resulting in a significantly different clustered pattern. The number and sizes of F. obscuripes nests in our study site are projected to decrease in the next 40 years, although further study of this population's colony structures is needed to understand the extent of this decrease. Elaeagnus umbellata is a common invasive shrub, and similar impacts on native species might occur in its invasive range, or in areas with similar shrub invasions.