Insights into the Biogeography and Polyploid Evolution of New Zealand Asplenium from Chloroplast DNA Sequence Data

Abstract

Nucleotide sequences of the chloroplast trnL-trnF intergenic spacer were obtained for 21 of the 22 indigenous Asplenium taxa presently recognized from New Zealand. Nucleotide sequences of the chloroplast rbcL gene were also obtained from eleven New Zealand species representative of the diversity found in the trnL-trnF intergenic spacer. Phylogenetic analyses of these chloroplast sequence data indicate that the Asplenium species of New Zealand are not monophyletic. More specifically, the Asplenium species participating in hybridization in New Zealand form a closely related ‘Austral’ group, whereas the non-hybridizing species have closer affinities to species from outside New Zealand. Within the Austral group, three well-supported sub-groups are recognized, represented by the species A. bulbiferum, A. flaccidum, and A. obtusatum. Dating analyses reject an 80 million year old vicariant origin for any of the Asplenium lineages in New Zealand, and the distributions of the many Asplenium species disjunct between New Zealand and elsewhere appear best explained by long-distance dispersal. The likely chloroplast/maternal parent for each of the New Zealand octoploid species is discussed.