Genetic Bottlenecks in Time and Space: Reconstructing Invasions from Contemporary and Historical Collections

Abstract

Herbarium accession data offer a useful historical botanical perspective and have been used to track the spread of plant invasions through time and space. Nevertheless, few studies have utilised this resource for genetic analysis to reconstruct a more complete picture of historical invasion dynamics, including the occurrence of separate introduction events. In this study, we combined nuclear and chloroplast microsatellite analyses of contemporary and historical collections of Senecio madagascariensis, a globally invasive weed first introduced to Australia c. 1918 from its native South Africa. Analysis of nuclear microsatellites, together with temporal spread data and simulations of herbarium voucher sampling, revealed distinct introductions to south-eastern Australia and mid-eastern Australia. Genetic diversity of the south-eastern invasive population was lower than in the native range, but higher than in the mid-eastern invasion. In the invasive range, despite its low resolution, our chloroplast microsatellite data revealed the occurrence of new haplotypes over time, probably as the result of subsequent introduction(s) to Australia from the native range during the latter half of the 20th century. Our work demonstrates how molecular studies of contemporary and historical field collections can be combined to reconstruct a more complete picture of the invasion history of introduced taxa. Further, our study indicates that a survey of contemporary samples only (as undertaken for the majority of invasive species studies) would be insufficient to identify potential source populations and occurrence of multiple introductions.

Invasive Rosa rugosa populations outperform native populations, but some populations have greater invasive potential than others

“…In Northwest Europe, R. rugosa often forms dominant, large, and dense scrub that excludes, at a local scale, native species 25,26 . Unlike many invasive species that harbour lower genetic diversity in their invasive range than their native range 27–29 , European R. rugosa populations show similar levels of expected heterozygosity ( H e ) as native populations in the Far East of Russia, East Asia and northern Japan 30,31 .…”

Invasion history of Cardamine hirsuta in Japan inferred from genetic analyses of herbarium specimens and current populations

“…So far, relatively few studies have performed combined analyses of the genotypic information from both currently existing populations and herbarium specimens (Saltonstall 2002;Hutchinson et al 2003;Lelong et al 2007;Dormontt et al 2014). These specimens are useful for reconstructing the invasion history of Japan.…”

Occasional hybridization between a native and invasiveSeneciospecies in Australia is unlikely to contribute to invasive success

“…Senecio madagascariensis is a diploid plant, initially introduced to south-eastern Australia from the KwaZulu-Natal province of South Africa in the early part of the 20th century ( Radford et al, 2000 ). Molecular analysis of contemporary and historical field collections has pointed to at least two separate introductions ( Dormontt et al, 2014 ). Senecio pinnatifolius (previously S. lautus ) is a tetraploid plant native to Australia.…”