Patterns of Genetic Diversity in Highly Invasive Species: Cogongrass (Imperata cylindrica) Expansion in the Invaded Range of the Southern United States (US).

Rima D Lucardi,Lisa E Wallace,Gary N Ervin

doi:10.3390/plants9040423

Abstract

The spatial expansions of invasive organisms in the novel range are generally expected to follow an isolation-by-distance relationship (IBD) if the invasion is biologically driven; however, many invasions are facilitated anthropogenically. This research focused on the extant expansion patterns of cogongrass (Imperata cylindrica). Cogongrass is a widespread invasive species throughout the southern United States (US). Patterns of infestation vary among US states. Cogongrass is pyrogenic, and its invasion threatens softwood (Pinus spp.) plantations, a substantial economic market for this US region. Over 600 individuals were sampled from seven invaded US states, using amplified fragment length polymorphisms (AFLPs) to assess genetic diversity and population structure. We suspected that differences in historical management efforts among US states influenced differences in genetic diversity and structure. We detected two genetic lineages at the highest level of analysis. One genetic lineage was locally restricted, whereas the other was found throughout the study region. Admixed individuals were found in all US states and consistently co-occurred with the dominant lineage, suggesting that secondary contact and hybridization may have facilitated expansion. The widespread prevalence of only one of the two detected genetic lineages suggests a primary genetic lineage responsible for on-going population expansion in the US.

Highlights

Biological invasions continue to increase during this era of increased global connectivity [1], while research has sought to understand the biological mechanisms which contribute to novel invasion success or the failure to establish or expand beyond incipient populations [2]
The amplified fragment length polymorphisms (AFLPs) analysis resulted in 2057 polymorphic loci from 676 cogongrass individuals
The majority of individuals sampled for this work were assigned with a 90% or greater probability to the AL-type lineage (Figure 2)

Summary

Introduction

Biological invasions continue to increase during this era of increased global connectivity [1], while research has sought to understand the biological mechanisms which contribute to novel invasion success or the failure to establish or expand beyond incipient populations [2]. Plants 2020, 9, 423 patches, novel dispersal routes and/or mechanisms) in the spread and establishment of invasive plants [14,15,16]. For many weedy plant species, human activities influence inter-patch connectivity by creating new habitats and by enhancing dispersal [17,18,19,20]. Long-distance dispersal can increase the overall rates of spread, and has the potential to influence the population’s genetic structure by facilitating intraspecific hybridization among independent novel introductions or through the homogenization of a regional population of a particular plant invader

Methods

Results

Conclusion