Genetic Variation And Gene Flow In Fragmented Populations Of The Endangered Amargosa Vole Microtus Californicus Scirpensis

Author : Rachel H. Toczydlowski
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (112 download)

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Download or read book Genetic and Phenotypic Differentiation in [Impatiens Capensis] Meerb. in Riverine Networks written by Rachel H. Toczydlowski and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Anthropogenic activities continue to erode and fragment habitats, creating a patchwork landscape that threatens the long-term persistence of many populations and some species. Subsequent genetic isolation, low genetic variation, and small effective population sizes can increase inbreeding or otherwise limit adaptive potential of populations. However, genetic isolation can also facilitate local adaptation by restricting the introduction of maladapted alleles and homogenization of the regional gene pool. In this dissertation, I seek to understand how gene flow, adaptive divergence, and inbreeding interact in natural populations subject to habitat fragmentation. I studied patterns of phenotypic and molecular genetic variation and divergence within and among populations of Impatiens capensis, a common, native, annual herb with a mixed mating system. I focused on 12 populations occurring in small, remnant, floodplain forests, marshes, and lowland forests that were surrounded by an agricultural/urban matrix. These study populations were nested within four river systems divided between two major watersheds in Wisconsin, USA. I genotyped 24-25 individuals in each population at 12,856 SNPs using genotyping-by-sequencing to characterize patterns of molecular genetic differentiation among these populations and identified potential landscape drivers of differentiation. Genetic isolation and drift appear to play a strong role in structuring these populations. Limited gene flow may occur along rivers, but overall population differentiation was high (FST = 0.32). Population-level inbreeding (FIS = 0.2-0.9) was higher in smaller, more isolated populations. I next investigated how plasticity and potentially adaptive genetic differentiation interact to drive patterns of phenotypic differentiation by comparing morphological and reproductive traits of maternal plants within wild populations to those of their self-fertilized progeny grown in a common garden. Populations showed strong phenotypic divergence in their home environments but converged considerably in the common garden. Nevertheless, differences in morphology, survival, and reproduction remained. Phenotypic differentiation covaried with environmental gradients in expected ways suggesting both adaptive plasticity and local adaptation. Finally, I studied how maternal and progeny fitness relate to variation in individual, maternal, and population-level inbreeding. Progeny from chasmogamous seeds (CH - potentially outcrossed) were larger and produced more seed capsules than progeny from cleistogamous seeds (CL - selfed) in the common garden demonstrating inbreeding depression. In outbred populations, reproductive output increased with maternal heterozygosity, as expected, but this relationship reversed in more inbred populations, both for mothers in their home environments and for their progeny in the common garden. These results suggest inbred I. capensis populations have only a limited capacity to purge (or fully fix) their genetic load. In rapidly changing environments, species must migrate or genetically adapt. Habitat fragmentation limits both processes, potentially compromising the ability of species to persist in fragmented landscapes.