Senecio madagascariensis Poir. in South America: Evidence for multiple introductions

BREM, MARTA CAROLINA; ROBLEDO DOBLADEZ, GERMÁN ARIEL; DEMATTEIS, BRUNO; COULLERI, JUAN PABLO

BIOLOGICAL INVASIONS

SPRINGER

Lugar: Berlin; Año: 2024

1387-3547

Studies on the genetic variation in invasive species can shed light on the dynamics of invasion history from both ecological and evolutionary perspectives. This study aimed to identify the origin of the South American populations of Senecio madagascariensis, estimate the number of introduction events of this invasive species in the subcontinent, and understand the evolutionary forces at play in the invasive range. To achieve these objectives, we characterized fireweed South American populations using internal transcribed spacer (ITS) and microsatellite markers. Based on the ITS data, we established that two invasive waves occurred in South America. The first wave, originating exclusively from South Africa, reached Argentina in the 1940s. The second wave occurred in the 1990s, reached northeastern Argentina, Brazil, and Uruguay. Populations belonging to this second wave share genetic homology with samples from Australia, the Hawaiian Islands, and South Africa. This is further supported by Bayesian and frequency-based analyses of microsatellites, which revealed a genetic structure with two major clusters corresponding to the two invasive waves. Moreover, these two clusters showed significant genetic distance, driven by patterns of local adaptation and gene flow between members of each cluster but less among them. All the evidence recollected shows that S. madagascariensis would be a super invader species. Spatial analyses also revealed a high correlation between genetic and geographical distances. Estimates of "first-generation migrants" suggest that contemporary dispersal occurs more frequently at smaller than at larger spatial, indicating that this species primarily spreads through a stratified strategy.