The impacts of evolutionary and human mediated dispersal mechanisms on invasion success in Solanaceae

Abstract

Understanding the mechanisms behind the dispersal and evolution of agricultural weeds is critical for the development of appropriate weed management strategies and protection of the world's food supply. However, little is known about the evolution of weed species in agricultural environments or the impacts of human-mediated dispersal on the evolutionary potential of these species. To gain a deeper understanding of the evolution and evolutionary potential of weeds in agricultural environments, I use a population genetics approach to investigate the genetic diversity of two non-native, invasive Solanum species that are problematic in agricultural systems (Solanum elaeagnifolium and S. torvum). I focus on three key questions: 1) do population structure and differentiation exist, 2) what is the level of genetic diversity present, and; 3) has the evolutionary potential of these species been diminished in non-native regions post introduction? Overall, results indicate the level of genetic diversity was comparable throughout each species' range; genetic population differentiation and structure existed; and adverse effects due to founding events were not evident. To address the need for appropriate weed management and protection of the world's food supply I explore two practical strategies. First, I examine non-native Solanum species found in agricultural settings. Specifically, I assess whether Silverleaf nightshade (Solanum elaeagnifolium), a non-native agricultural weed, is more likely associated with a specific crop type than other non-native Solanum species in California. To answer this question, I utilize cropland data layers (CDLs) and a geographical information system-based (GIS) spatial correlation approach to determine weed-crop correlations. I describe these associations as likely indicators of primary dispersal mechanisms of unwanted species. Second, I utilize the premise of DNA barcoding to develop a molecular means of distinguishing between four Solanum species on the Hawaii Noxious Weed List and their close relatives. I suggest two molecular techniques that provide easily recognizable patterns that represent a unique DNA profile for each of the four focal species examined.