Karyological, morphological, and phylogenetic diversification in Leucocoryne Lindl (Allioideae, Amaryllidaceae)

Abstract

The genus Leucocoryne (Amaryllidaceae) comprises approximately 15 species and is the only genus of the tribe Ipheieae endemic to the western region of Chile in sclerophyll and arid winter-rainfall biomes in the Andes. To better understand the karyotype diversification of this genus, nine species of Leucocoryne were analyzed in terms of their chromosome number and morphology, CMA and DAPI heterochromatic bands, distribution of rDNA sites, and their molecular phylogenetic relationships. Based on phylogenetic analyses Leucocoryne was divided in four clades: I (L. alliacea and L. conferta); II (L. dimorphopetala and L. narcisoides); III (L. coquimbensis, L. macropetala, L. appendiculata, L. talinensis, L. angustipetala, L. purpurea, and L. violacescens); and IV (L. vittata, L. ixioides, L. foetida, and L. pauciflora). The species were diploids with 2n = 10 (6M + 4A) or tetraploids with 2n = 18 (14M + 4A)/2n = 19 (13M + 6A). 45S rDNA sites were co-localized with CMA+/DAPI− bands on the short arms of acrocentric chromosomes in all species. 5S rDNA sites were observed on one, two, or four pairs of metacentric chromosomes per species. Estimations of the ancestral karyotype suggest that 2n = 10 (6M + 2A) with one 5S rDNA site per monoploid complement was the plesiomorphic condition of the genus Leucocoryne. Increases in number of 5S rDNA sites in the same species associated with biome shifts from sclerophyll to arid winter-rainfall region occurred independently in clade II and clade III. The two species of clade II retained the six fertile stamens (plesiomorphic condition) in contrast to the other Leucocoryne species that reduced to only three functional stamens. Based on these findings, we discuss the role of environmental change on the diversification of this group.