Natural variation and conservation of Lepidium sisymbrioides Hook, f. and L. solandri Kirk (Brassicaceae) in South Island, New Zealand, based on morphological and DNA sequence data

Abstract

The South Island, New Zealand, endemics Lepidium sisymbrioides and L. solandri are accepted at species rank. L. solandri Kirk is reinstated and includes L. matau Petrie in synonymy, and L. kawarau is reduced to synonymy of L. sisymbrioides. Twenty‐nine floral and vegetative morphological characters were measured and used for analyses of character variation and principal components analysis. Leaf characters proved to be the most useful in distinguishing between L. sisymbrioides and L. solandri, with 12 of the 15 leaf characters having significantly different means. Only 7 of the 14 floral characters included in the study have significantly different means. In comparison to L. solandri, L. sisymbrioides has longer and narrower terminal and primary pinnae and cauline leaves, more secondary pinnae and cauline leaf lobes, less hairy sepals and ovaries, narrower ovaries, and shorter filaments. L. sisymbrioides occurs on rock outcrops in the upper Manuherikia, Waitaki, and Kawarau river valleys. L. solandri grows mainly on alluvium and outwash gravels in semi‐arid parts of inland Canterbury and Central Otago. DNA sequence data from ITS, ETS, and trnL‐trnF markers were used to examine phylogenetic patterns in L. sisymbrioides and L. solandri, and the related species L. kirkii, L. naufragorum, and L. tenuicaule. There is substantial variation in these markers in L. sisymbrioides and L. solandri, and this is considered to be due to introgression from other species of Lepidium, such as L. kirkii and L. tenuicaule. Much of the variation in the ETS sequences occurs in samples of L. sisymbrioides and L. solandri from the Manuherikia River valley, and this can be attributed to geneflow with the sympatric L. kirkii. Lepidium sisymbrioides and L. solandri are considered to be “Acutely Threatened, Nationally Endangered” using the New Zealand threatened plant classification criteria. In this assessment both species are considered to be data poor. Further field survey for new populations is required.