Population Dynamics and Evolutionary History of the Weedy VineIpomoea hederaceain North America

Abstract

Disentangling the historical evolutionary processes that contribute to patterns of phenotypic and genetic variation is important for understanding contemporary patterns of both traits of interest and genetic diversity of a species. Ipomoea hederacea is a self-compatible species whose geographic origin is contested, and previous work suggests that although there are signals of adaptation (significant leaf shape and flowering time clines), no population structure or neutral genetic differentiation of I. hederacea populations was detected. Here, we use DNA sequence data to characterize patterns of genetic variation to establish a more detailed understanding of the current and historical processes that may have generated the patterns of genetic variation in this species. We resequenced ca. 5000 bp across 7 genes for 192 individuals taken from 24 populations in North America. Our results indicate that North American I. hederacea populations are ubiquitously genetically depauperate, and patterns of nucleotide diversity are consistent with population expansion. Contrary to previous findings, we discovered significant population subdivision and isolation-by-distance, but genetic structure was spatially discontinuous, potentially implicating long-distance dispersal. We further found significant genetic differentiation at sequenced loci but nearly fourfold stronger differentiation at the leaf shape locus, strengthening evidence that the leaf shape locus is under divergent selection. We propose that North American I. hederacea has experienced a recent founder event, and/or population dynamics are best described by a metapopulation model (high turnover and dispersal), leading to low genetic diversity and a patchy genetic distribution.

A test of the reproductive assurance hypothesis inIpomoea hederacea: does inbreeding depression counteract the benefits of self‐pollination?

“…The low values of ID found in this study, as well as in U.S. populations of I. hederacea, also support this idea (Hull-Sanders et al, 2005). Annual morning glory species that occur in human-disturbed habitats possibly occur as metapopulations, with population dynamics involving frequent colonization and extinction events and distinct genetic structuring, as was demonstrated for eastern U.S. populations of I. hederacea (Campitelli and Stinchcombe, 2014). In such a context, both RA and ID should be relevant to the maintenance of morning glory populations.…”

The geographic mosaic of herbicide resistance evolution in the common morning glory, Ipomoea purpurea: Evidence for resistance hotspots and low genetic differentiation across the landscape

“…Thus, the Southeastern USA in particular may have experienced repeated re-introduction and establishment of this species, following which subsequent range expansion or colonization into more northern areas occurred. Perhaps the presence of some genetic structure and yet evidence for migration and admixture between populations of this species is due to the re-introduction of a limited but variable pool of germplasm, a scenario similar to that posited for I. purpurea's sister species, I. hederacea (Campitelli and Stinchcombe 2014 ). The Carolinas (specifically NC) have a relatively high density of populations of I. purpurea compared to other states—and populations within this range contain all of the genotypes that we detected in our survey, suggesting NC as a possible source for subsequent introductions into other areas of the Southeastern and the Midwestern USA.…”

WhoGEM: an admixture-based prediction machine accurately predicts quantitative functional traits in plants

“…Building on these frameworks, we place our studies of genetic and phenotypic variation into a geographical context. This can provide powerful insights into how historical events, patterns of migration, and natural selection have led to genetic distinctions between various present-day populations [20–22].…”