Phenotypic divergence during the invasion of Phyla canescens in Australia and France: evidence for selection‐driven evolution

Abstract

Rapid adaptive evolution has been advocated as a mechanism that promotes invasion. Demonstrating adaptive evolution in invasive species requires rigorous analysis of phenotypic shifts driven by selection. Here, we document selection-driven evolution of Phyla canescens, an Argentine weed, in two invaded regions (Australia and France). Invasive populations possessed similar or higher diversity than native populations, and displayed mixed lineages from different sources, suggesting that genetic bottlenecks in both countries might have been alleviated by multiple introductions. Compared to native populations, Australian populations displayed more investment in sexual reproduction, whereas French populations possessed enhanced vegetative reproduction and growth. We partitioned evolutionary forces (selection vs. stochastic events) using two independent methods. Results of both analyses suggest that the pattern of molecular and phenotypic variability among regions was consistent with selection-driven evolution, rather than stochastic events. Our findings indicate that selection has shaped the evolution of P. canescens in two different invaded regions.

Influence of invasion history on rapid morphological divergence across island populations of an exotic bird

“…There are now several examples of marked divergence in genetic or phenotypic traits between two or more exotic populations (Egizi, Fefferman, & Fonseca, 2015; Freed, Conant, & Fleischer, 1987; Lucek, Sivasundar, & Seehausen, 2014; Phillimore et al., 2008; Westley, Conway, & Fleming, 2012; Xu et al., 2010). Such differences can be explained by in situ adaptation to local biological and environmental conditions, or from events that occurred within the species’ invasion history (e.g., Allendorf & Lundquist, 2003; Dlugosch & Parker, 2008a; Keller & Taylor, 2008).…”

The Phylogeny and Biogeography of Phyla nodiflora (Verbenaceae) Reveals Native and Invasive Lineages throughout the World

“…Greene. Phyla canescens is a highly invasive herb in Australia [18,[47][48][49] whereas P. cuneifolia, P. fructicosa and P. lanceolata are not listed as occurring in Australia (Australia's Virtual Herbarium, accessed 26 February 2017). The taxa outside of Australia with the closest native range to P. nodiflora include the Latin American P. canescens, P. betulifolia (Kunth) Greene and P. fructicosa (= P. nodiflora var.…”

“…First, it confirms that it is native in many parts of the world where its status had previously been considered exotic (e.g., Australia, [8]; South Africa, [83]). Second, exotic lineages could become invasive in their own right, as P. canescens has already done in Australia [48,49], although there is currently limited evidence of it doing so. Finally, native and exotic lineages could potentially interbreed, threatening the integrity of native lineages.…”

Is Rapid Adaptive Evolution Important in Successful Invasions?

“…Another study controlling for neutral evolution has found that both adaptive evolution and colonization history have infl uenced the generation of phenotypic clines in two introduced species of Silene in North America (Keller et al 2009 ). Recently, Xu et al (2010) demonstrated that adaptive evolution was responsible for phenotypic divergence between the native range of Phyla canescens and two different invaded regions. Although these excellent studies highlight that adaptive evolution can drive phenotypic divergence within and between the ranges of invasive species, they do not elucidate the type of genetic variation underlying ecologically relevant traits.…”

“…QTL mapping with RAD tags in controlled crosses of freshwater and sity between the native and introduced range of invasive species (reviewed in Dlugosch & Parker 2008a ). Recently, there has been a surge of interest in investigating adaptive evolution in invasive species (Maron et al 2004 ;Keller & Taylor 2008 ;Prentis et al 2008 ), yet many studies have not adequately controlled for neutral evolutionary processes (but see Maron et al 2004 ;Keller et al 2009 ;Colautti et al 2010 ;Xu et al 2010 ). Several methods exist to determine whether adaptive evolution is responsible for rapid phenotypic change in biological invasions, while controlling for neutral evolution, phenotypic plasticity and preadaptation.…”