Scale‐dependent post‐establishment spread and genetic diversity in an invading mollusc in South America

Abstract

Aims Our study aimed to characterize the dispersal dynamics and population genetic structure of the introduced golden mussel Limnoperna fortunei throughout its invaded range in South America and to determine how different dispersal methods, that is, human‐mediated dispersal and downstream natural dispersal, contribute to genetic variation among populations. Location Paraná–Uruguay–Río de la Plata watershed in Argentina, Brazil, Paraguay and Uruguay. Methods We performed genetic analyses based on a comprehensive sampling strategy encompassing 22 populations (N = 712) throughout the invaded range in South America, using the mitochondrial cytochrome c oxidase subunit I (COI) gene and eight polymorphic nuclear microsatellites. We employed both population genetics and phylogenetic analyses to clarify the dispersal dynamics and population genetic structure. Results We detected relatively high genetic differentiation between populations (FST = −0.041 to 0.111 for COI, −0.060 to 0.108 for microsatellites) at both fine and large geographical scales. Bayesian clustering and three‐dimensional factorial correspondence analyses consistently revealed two genetically distinct clusters, highlighting genetic discontinuities in the invaded range. Results of all genetic analyses suggest ship‐mediated ‘jump’ dispersal as the dominant mode of spread of golden mussels in South America, while downstream natural dispersal has had limited effects on contemporary genetic patterns. Main conclusions Our study provides new evidence that post‐establishment dispersal dynamics and genetic patterns vary across geographical scales. While ship‐mediated ‘jump’ dispersal dominates post‐establishment spread of golden mussels in South America, once colonies become established in upstream locations, larvae produced may be advected downstream to infill patchy distributions. Moreover, genetic structuring at fine geographical scales, especially within the same drainages, suggests a further detailed understanding of dynamics of larval dispersal and settlement in different water systems. Knowledge of the mechanisms by which post‐establishment spread occurs can, in some cases, be used to limit dispersal of golden mussels and other introduced species.

Genetic Diversity in Introduced Golden Mussel Populations Corresponds to Vector Activity

“…The low genetic differentiation between TW1 and TW2 indicates similar source(s) or high gene flow within Taiwan. Long-distance or “jump” dispersal of L. fortunei , to upstream areas due to ship-mediated translocation appears responsible for the patchy post-establishment spread of the species in South America [47], [70]. Higher genetic differentiation among introduced populations in Asia relative to those in South America may be linked to the presence of geographical barriers between countries in Asia (e.g.…”

“…All sequences that contained ambiguous sites were subsequently sequenced with the forward primer. We genotyped all populations at eight microsatellite loci [47]. Fragment analysis was performed using an ABI 3130XL automated sequencer with GeneScan™–500 LIZ™ size standard.…”

Snakes on an island: independent introductions have different potentials for invasion

“…For example, biotic factors such as 'enemy release' (a lack of disease or predators in the introduced location) may result in populations in non-native ranges doing better than would be expected for the species (Liu and Stiling 2006); while abiotic factors, such as climate, would limit where the species could survive. Environmental heterogeneity could mean that within the same species, the patterns and dynamics of colonization and expansion would vary in different ranges (Bock et al 2011) and across different spatial scales (Zhan et al 2012). Finally, a species may respond to novel habitats with adaptive changes (Bohn et al 2004;Feiner et al 2012).…”

Invasion genetics of the Pacific oyster Crassostrea gigas in the British Isles inferred from microsatellite and mitochondrial markers

“…Audzijonyte et al 2008;Hayes et al 2008;Kajita et al 2012) have been widely used in such studies, including in combination (e.g. Neilson and Stepien 2011;Zhan et al 2012).…”