Biology subjects

Dlugosch, K. M.

Publications and source records attributed to Dlugosch, K. M..

4 recordsLinked to original sources

bioRxiv2018

Expansion history and environmental suitability shape effective population size in a plant invasion

The margins of an expanding range are predicted to be challenging environments for adaptation. Marginal populations should often experience low effective population sizes (Ne) where genetic drift is high due to demographic expansion and/or census population size is low due to unfavorable environmental conditions. Nevertheless, invasive species demonstrate increasing evidence of rapid evolution and potential adaptation to novel environments encountered during colonization, calling into question whether significant reductions in Ne are realized during range expansions in nature. Here we report one of the first empirical tests of the joint effects of expansion dynamics and environment on effective population size variation during invasive range expansion. We estimate contemporary values of Ne using rates of linkage disequilibrium among genome-wide markers within introduced populations of the highly invasive plant Centaurea solstitialis (yellow starthistle) in North America (California, USA), as well as in native European populations. As predicted, we find that Ne within the invasion is positively correlated with both expansion history (time since founding) and habitat quality (abiotic climate). History and environment had independent additive effects with similar effect sizes, supporting an important role of both factors in this invasion. These results support theoretical expectations for the population genetics of range expansion, though whether these processes can ultimately arrest the spread of an invasive species remains an open question.

ecology↗

bioRxiv2017

Variation in the oxidative burst in response to wounding and bacterial infection among native and invading genotypes of yellow starthistle (Centaurea solstitialis)

O_LIPremise of the study: Invasive plants may leave enemies behind when they colonize a new habitat, allowing selection to favor increased investment in growth and/or reproduction over defensive traits. Previous studies have identified reduced diversity of potential bacterial pathogens and evolutionary increases in growth and reproduction in invading populations of yellow starthistle (Centaurea solstitialis). This study leverages a recently developed high-throughput assay of immune function to test for evidence of a trade-off between increased growth and defense against bacterial pathogens in yellow starthistles invasion of California (USA).\nC_LIO_LIMethods: Seven bacterial strains were cultured from infected leaf tissue in the native range. Healthy leaf tissue from five native European collections and six invading collections were exposed to these native bacterial strains. A standardized assay of peroxidase activity was used measure the oxidative burst immune response to pathogen recognition by the leaf. Immune responses were compared to plant growth within and between ranges to assess evidence for a trade-off.\nC_LIO_LIKey Results: Plant genotypes from the native range demonstrated a higher immune response to bacterial strains than did invading genotypes, consistent with a trade-off with plant growth across regions. The same trade-off was also apparent across genotypes from the native range, but not across genotypes from the invaded range.\nC_LIO_LIConclusions: Our results provide evidence that increased growth in a highly invasive plant species may come at a cost to immune function, consistent with the hypothesis that escape from enemies can provide opportunities for shifts in resource allocation that favor the proliferation of non-native species.\nC_LI

plant biology↗

bioRxiv2017

The Prevalence And Benefits Of Admixture During Species Invasions: A Role For Epistasis?

Species introductions often bring together genetically divergent source populations, resulting in genetic admixture. This geographic reshuffling of diversity has the potential to generate favorable new genetic combinations, facilitating the establishment and invasive spread of introduced populations. Observational support for the superior performance of admixed introductions has been mixed, however, and the broad importance of admixture to invasion questioned. Under most underlying mechanisms, admixtures benefits should be expected to increasewith greater divergence among and lower genetic diversity within source populations. We use a literature survey to quantify the prevalence of admixture and evaluate whether it occurrs under circumstances predicted to be mostbeneficial to introduced species. We find that 39% of species are reported to be admixed when introduced. Admixed introductions come from sources with a wide range of genetic variation, but are disproportionately absent where there is high genetic divergence among native populations. We discuss multiple potential explanations for these patterns, but note that negative epistatic interactions should be expected at high divergence amongpopulations (outbreeding depression). As a case study, we experimentally cross source populations differing in divergence in the invasive plant Centaurea solstitialis. We find many positive (heterotic) interactions, but fitness benefits decline and are ultimately negative at high source divergence, with patterns suggestingcyto-nuclear epistasis. We conclude that admixture is common in species introductions and often happens under conditions expected to be beneficial to invaders, but that these conditions may be constrained by predictable negativegenetic interactions, potentially explaining conflicting evidence for admixture's benefits to invasion.

evolutionary biology↗

bioRxiv2017

Escape from bacterial diversity: potential enemy release in invading yellow starthistle (Centaurea solstitialis) microbiomes

O_LIInvasive species could benefit from introduction to locations with favorable species interactions. Microbiomes are an important source of interactions that vary across regions. We examine whether bacterial communities could explain more favorable microbial interactions in highly invasive populations of yellow starthistle.\nC_LIO_LIWe sequenced amplicons of prokaryotic 16S rRNA genes to characterize bacterial community composition in the phyllosphere, ectorhizosphere, and endorhizosphere of plants from seven invading populations in California, USA and eight native populations in Europe. We tested for differentiation of microbiomes by geography, plant compartment, and plant genotype.\nC_LIO_LIBacterial communities differed significantly between native and invaded ranges within plant compartments, with consistently lower diversity in plants from the invaded range. Genera containing known plant pathogens also showed lower diversity in invaded range plants. The diversity of bacteria in roots was positively correlated with plant genotype diversity within both ranges, but this relationship did not explain microbial differences between ranges.\nC_LIO_LIOur findings reveal changes in the composition and diversity of bacterial interactions in invading plants, consistent with observations of altered soil interactions in this invasion. These results call for further study of the sources of variation in microbiomes and the potential for bacteria to facilitate invasion success.\nC_LI

plant biology↗