The phylogenetic relationship in the Lachenalia pusilla group

[摘要] English: The geophytic genus Lachenalia Jacq.f.ex Murray is the largest genus (consists about 133 species, Duncan (2012)) in the tribe Massonieae. It is the most complex and advanced genus within the tribe Massonieae (sub-­‐family Hyacinthoideae) (Pfosser et al. 2003). This highly morphological and chromosomal variable genus, is endemic to the south-­‐western winter rainfall regions of Southern Africa with few exceptions and has been recorded in the literature as early as the 17th century (1787 Jacquin). The genus Lachenalia has commercial value as a garden pot plant or for cut flowers. From as early as the 1990s, the ARC started a breeding programme with the aims to improve and increase the international market potential of this plant. There is a correlation between species' basic chromosome number, molecular systematics and cross-­‐ability, thus (1) based on molecular systematics, species with the same basic chromosome number group together on the phylogenetic tree and (2) species in the same group have higher cross-­‐ability. Several authors revised the classification and grouping of Lachenalia species. However, the inventory of the species and species delimitation is not yet complete. Frequently, different species within the genus Lachenalia are treated under the same name (species can be mis-­‐identified and then recognised as a different species, i.e., L. pallida) or one plant is distributed between different names (i.e. L. pallida). This error results in a highly heterogeneous and polymorphic genus that forms polymers or high homoplastic phylogenetic trees. Species with x = 7 are ancestral species from which other species evolved. T 80 The evolutional relationship of x = 9, 10 and 13 species, plus x = 7 and 8 prostrate and geoflora like species (Lachenalia pusilla group) was tested using molecular phylogenetic markers (ITS, rbcL, trnL-­‐F and psbA-­‐trnH). Species with x = 7 (group x = 7), x = 8 (group x = 8), x = 11 (group x = 11) and subspecies Polyxena (Polyxena group) formed monophyletic clades. The majority species from the Lachenalia pusilla group are scattered between the other groups. The Lachenalia pusilla group may be a hybridization product of Lachenalia species with different basic numbers, and/or with their closest Lachenalia relative (possibly with the genus Massonia). Incongruence test performed on two BI trees of the plastid dataset (trnL-­‐F) and nucleus dataset (ITS2) (Tanglegram) suggested a hybrid evolution of the Lachenalia pusilla group. Evolution of the Lachenalia pusilla group (species with x = 9, 10 and 13) plus certain x = 7 and x = 8 species by means of hybridization was also supported by reticulate analyse (NJ tree). This study suggested a reticulate evolution of the Lachenalia pusilla group (x = 9, 10 and 13) and few taxon with x = 7 and 8. Previous studies recommended multiple gene phylogenetic analysis for better Lachenalia species resolution. However, due to high incongruence between datasets, multiple gene analysis does not provide better answers for Lachenalia classification. Genomic in situ hybridization, reticulate analysis and other phylogenetic methods can results in better species delimitation of Lachenalia.

[发布机构] University of the Free State