The Evolutionary History of New Zealand Deschampsia Is Marked by Long-Distance Dispersal, Endemism, and Hybridization

Abstract

The contrasting evolutionary histories of endemic versus related cosmopolitan species provide avenues to understand the spatial drivers and limitations of biodiversity. Here, we investigated the evolutionary history of three New Zealand endemic Deschampsia species, and how they are related to cosmopolitan D. cespitosa. We used RADseq to test species delimitations, infer a dated species tree, and investigate gene flow patterns between the New Zealand endemics and the D. cespitosa populations of New Zealand, Australia and Korea. Whole plastid DNA analysis was performed on a larger worldwide sampling. Morphometrics of selected characters were applied to New Zealand sampling. Our RADseq review of over 55 Mbp showed the endemics as genetically well-defined from each other. Their last common ancestor with D. cespitosa lived during the last ten MY. The New Zealand D. cespitosa appears in a clade with Australian and Korean samples. Whole plastid DNA analysis revealed the endemics as members of a southern hemisphere clade, excluding the extant D. cespitosa of New Zealand. Both data provided strong evidence for hybridization between D. cespitosa and D. chapmanii. Our findings provide evidence for at least two migration events of the genus Deschampsia to New Zealand and hybridization between D. cespitosa and endemic taxa.

Genome-wide data reveal bi-direction and asymmetrical hybridization origin of a fern species Microlepia matthewii

“…The result of admixture analyses for K = 2 didn’t agree with the phylogenetic tree, as the M. marginata complex separated first, and M. hancei , M. calvescens and M. matthewii clustered together in another group. In many studies, the first run of structure at K = 2 tends to be the earliest of the two major branches to be separated or not genetically mixed (e.g., Yi et al., 2023 ) and often exists as the optimal K (e.g., Chattopadhyay et al., 2019 ; Xue et al., 2021 ; Encinas-Viso et al., 2022 ) because there are generally much longer branch lengths between the two main clades than within them. However, in this study, M. calvescens did not cluster with its closest relative on the phylogenetic tree, M. marginata , but instead with M. hancei at K = 2.…”