title: 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.
authors.affiliation: Australian Centre for Evolutionary Biology and Biodiversity, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Eleanor E
authors.initials: EE
authors.lastname: Dormontt
authors.affiliation: School of Biological Sciences, Flinders University, Adelaide, South Australia, Australia; Evolutionary Biology Unit, South Australian Museum, Adelaide, South Australia, Australia.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Gardner
authors.affiliation: Australian Centre for Evolutionary Biology and Biodiversity, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Martin F
authors.initials: MF
authors.lastname: Breed
authors.affiliation: Centre for Invasion Biology, University of KwaZulu-Natal, Pietermaritzburg, South Africa.
authors.forename: James G
authors.initials: JG
authors.lastname: Rodger
authors.affiliation: School of Earth, Environmental and Biological Sciences, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Prentis
authors.affiliation: Australian Centre for Evolutionary Biology and Biodiversity, University of Adelaide, Adelaide, South Australia, Australia.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lowe
mesh_terms: D001315:Australia; D002467:Cell Nucleus / Q000235:genetics; D018742:DNA, Chloroplast / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics*; D014644:Genetic Variation; D049673:History, 20th Century; D058865:Introduced Species / Q000266:history*; D018895:Microsatellite Repeats; D008957:Models, Genetic; D058974:Phylogeography; D057685:Plant Weeds / Q000235:genetics*; D012674:Senecio / Q000235:genetics*; D013019:South Africa
chemical_list: D018742:DNA, Chloroplast; D018744:DNA, Plant