Phylogenetic relationships in the extreme polyploid complex of the New Zealand genus Leptinella (Compositae: Anthemideae) based on AFLP data

Abstract

AbstractAFLP fingerprinting for 236 individuals from 75 populations and 31 taxa of the Southern Hemisphere genus Leptinella (Compositae: Anthemideae) was carried out in order to infer the evolutionary relationships among the New Zealand representatives of the genus and to compare the results with sequence–based phylogenetic reconstructions for the genus. The New Zealand–based clade of the genus is characterised by the formation of an impressive polyploid complex with ploidy levels reaching from 4x to 24x. We observe a tripartition of taxa into species groups that correspond to species assemblages also found in the sequence–based reconstructions: A basal, presumably paraphyletic stock of tetraploid species (AFLP cluster A) corresponding to the morphologically defined Leptinella subg. Radiata is connected through one of its sub–clusters (A1, the L. minor group) with a monophyletic group of two clusters (B and C) with a sister–group relationship. While AFLP cluster B remained on the tetraploid level, clusters A and C form ploidy series reaching the levels of 16x and 24x, respectively. The lack of intermediate AFLP genotypes demonstrates that polyploidisation has occurred independently in the two clusters forming the L. pectinata/L. pyrethrifolia assemblage (cluster A2) in L. subg. Radiata and the L. dioica assemblage (clusters C1 and C2) in L. subg. Leptinella. The joint consideration of sequence–based reconstructions and AFLP fingerprint patterns further allows the formulation of an evolutionary hypothesis for the genus that tries to explain differentiation processes in a temporal and geographic framework: The available data argue for a Late Miocene (ca. 5–10 Ma) establishment of Leptinella in New Zealand and its further differentiation on the tetraploid level throughout the Pliocene and the Early Pleistocene, followed by extensive polyploidisation cycles caused by the climatic oscillations of the Pleistocene.