Global patterns of reproductive and cytotype diversity in an invasive clonal plant

The reproductive systems of invasive species play a key role in determining their geographical distributions. Oxalis pes-caprae is a clonal, polyploid, heterostylous, plant native to South Africa, but now invasive in all major Mediterranean climatic regions. Here, we extend earlier surveys in the Western Mediterranean basin of floral morph ratios, reproductive traits and ploidy level to include populations from South Africa and introduced regions of Australia, California and Chile. We sampled a total of 104 populations, 33 in South Africa, 29 in Australia, 27 in California and 15 in Chile and collected data on floral morph representation (trimorphic, dimorphic, monomorphic), flower size, fruit set, and ploidy level using flow cytometry. There were significant differences among regions in floral morph structure of populations, reproductive traits and ploidy level. Populations in South Africa were exclusively tristylous and largely tetraploid (4x); Australian populations were mostly pentaploid (5x, 65.5%), comprised exclusively of the short-styled morph, with the remaining populations either dimorphic or trimorphic. Populations in California and Chile were comprised exclusively of the 5x short-styled morph. Fruit set varied dramatically among populations with no fruit produced in 5x populations. Our study demonstrates striking geographical variation among regions in reproductive systems ranging from a mixture of sexual and clonal reproduction in the native range to exclusively clonal propagation in some introduced regions. This variation is likely to have important consequences for local adaptation and should be considered in future management decisions of invasive populations.