Using population genetics to match invasive Mesembryanthemum nodiflorum populations in North America to their origin

Invasive populations of the slenderleaf iceplant, Mesembryanthemum nodiflorum L., are problematicalong the west coast of North America. Evidence exists to support a southern Africanorigin of the plant, although there are populations in North Africa and the Mediterranean thatform part of its introduced range. There is interest in initiating a biological control programmefor the weed in its invaded range, but a clearer understanding of its invasion pathways andsources of origin is required. This study used both NextGen RADseq and fragment analysisISSR techniques to uncover the population structure and genetic diversity of M. nodiflorum inits native, introduced, and invaded ranges. The results supported a South African origin of M.nodiflorum based on a higher number of private alleles and overall genetic diversity. Humanmediateddispersal most likely introduced the plant to the Mediterranean Basin during the 1700sand 1800s via shipping lanes linking Australia and South Africa to Europe. Our results suggesta bridgehead effect, where a secondary invasion to North America from Mediterranean populationstook place. The high genetic similarity of the invaded range samples (California andMexico) to many of the introduced range populations (particularly to Tunisia) suggested thatat least two independent introduction events are likely to have taken place. The present resultssuggest that surveys for potential biocontrol agents for M. nodiflorum should be conducted inthe native South African distribution, where the greatest diversity of specialist natural enemiesare likely to be present. Additionally, any specialist natural enemies that could have been introducedwith the plant to the Mediterranean should also be considered, given the close geneticsimilarity between Mediterranean and invasive populations. The data in this repository contains the RADseq output for each sample used in the study.