Transatlantic invasion routes and adaptive potential in North American populations of the invasive glossy buckthorn,Frangula alnus

Abstract

Background and Aims Many invasive species severely threaten native biodiversity and ecosystem functioning. One of the most prominent questions in invasion genetics is how invasive populations can overcome genetic founder effects to establish stable populations after colonization of new habitats. High native genetic diversity and multiple introductions are expected to increase genetic diversity and adaptive potential in the invasive range. Our aim was to identify the European source populations of Frangula alnus (glossy buckthorn), an ornamental and highly invasive woody species that was deliberately introduced into North America at the end of the 18th century. A second aim of this study was to assess the adaptive potential as an explanation for the invasion success of this species.Methods Using a set of annotated single-nucleotide polymorphisms (SNPs) that were assigned a putative function based on sequence comparison with model species, a total of 38 native European and 21 invasive North American populations were subjected to distance-based structure and assignment analyses combined with population genomic tools. Genetic diversity at SNPs with ecologically relevant functions was considered as a proxy for adaptive potential.Key Results Patterns of invasion coincided with early modern transatlantic trading routes. Multiple introductions through transatlantic trade from a limited number of European port regions to American urban areas led to the establishment of bridgehead populations with high allelic richness and expected heterozygosity, allowing continuous secondary migration to natural areas.Conclusions Targeted eradication of the urban populations, where the highest genetic diversity and adaptive potential were observed, offers a promising strategy to arrest further invasion of native American prairies and forests.

Bridgehead Effects and Role of Adaptive Evolution in Invasive Populations

“…The second study suggested that increased genetic diversity, instead of reduced genetic diversity, may have conferred greater adaptive potential in a population of glossy buckthorn introduced from a bridgehead region [29]. Due to admixture resulting from several primary introductions, the bridgehead population had high allelic richness at loci with putative ecological functions.…”

“…Two studies suggested that genetic changes could underlie greater invasiveness of bridgehead populations [13,29]. However, none of these have demonstrated a causal link between the trait change and invasion success and cannot exclude that other processes have played a role in observed trait changes.…”

Unravelling the global invasion routes of a worldwide invader, the red swamp crayfish (Procambarus clarkii)

“…Biological invasions today are perceived as major components of global change, with severe negative environmental (Blackburn et al., ; Jeschke et al., ; Simberloff et al., ) and socio‐economic impacts (Vilà et al., ). To manage invasive species, it is of vital importance to identify invasion routes (De Kort, Mergeay, Jacquemyn, & Honnay, ). However, most knowledge about the transport routes of invasive species is based on historical and observational data, which are usually scarce, confusing, and sometimes inaccurate (Haydar, ; Roman, ).…”

Factors limiting the success of invasive glossy buckthorn (Frangula alnus) in New Hampshire’s eastern white pine – hardwood forests

“…One particularly damaging invasive plant is glossy buckthorn (Frangula alnus, hereafter "buckthorn"), a shrub native to Europe that has spread throughout southeastern Canada and the eastern United States (Catling andPorebski 1994, De Kort et al 2016). Similar to many invasive shrubs, buckthorn was introduced to North America in the late 18 th and early 19 th century during a period of high maritime transatlantic trade of plants from Europe to eastern North America (De Kort et al 2016). During this time, there was extensive buckthorn trade in urban ports, such as New York, which increased the genetic diversity of these populations in the United States.…”

“…During this time, there was extensive buckthorn trade in urban ports, such as New York, which increased the genetic diversity of these populations in the United States. The high genetic diversity prevented a bottleneck effect and allowed for buckthorn to adapt quickly to rural locations and eventually spread to natural areas successfully (De Kort et al 2016). In these areas, disturbances such habitat fragmentation due to road construction and timber harvesting (Moser et al 2016) have supported the spread of invasive plants.…”