Systematics/Phytogeography / Taxonomie/ Section
Wagstaff, Steven J. , Heenan, Peter B. , Molloy, Brian P. J. , Tate, Jennifer A. , deLange, Peter J. .
Hybridization in New Zealand Hoheria (Malvaceae) and its evolutionary and ecological significance.
Hybridization is a prominent feature of insular floras. It is important evolutionary process that helps new immigrants overcome the deleterious effects of a genetic bottleneck when they first become established on an island archipelago. We investigated the ecological and evolutionary significance of hybridization in the New Zealand endemic genus Hoheria. The genus includes seven species that form a monophyletic group along with Plagianthus (+ the monotypic Australian genera, Asterotrichion and Gynatrix). The clade is nested among Australian species of Lawrencia, which suggests that it arrived in New Zealand by long distance dispersal, then diversified from a single founding population. Interspecific hybrids of Hoheria are common in disturbed areas where the species ranges overlap. We employed Principal Components Analysis of morphological data and Parsimony and Splitstree analyses of DNA sequences to infer relationships. The PCA analysis recovered four discrete groups corresponding to H. angustifolia H. glabrata, H. lyallii and a fourth heterogeneous group comprised of H. populnea, H. equitum, H. sexstylosus, plus several putative hybrids. There was little sequence divergence in either the ITS or the trnK/matK sequences of Hoheria; in fact many of the individuals in our survey had identical sequences. Interestingly the ITS sequences also exhibited overlapping heteromorphic sites in putative hybrids. The inclusion of hybrids with the corresponding conflicting phylogenetic signal confounded our attempts to recover well supported monophyletic groups. However the relationships were more clearly resolved when the putative hybrids were excluded from the analysis. Hybridization networks also revealed incompatible signals in the data, but recovered well-supported groups that diverged from a central boxy network. Although the species of Hoheria are isolated by their ecological preferences or geographical distributions, it appears the internal mechanisms of reproductive isolation are weak. Our results have important implications for conservation and vegetation restoration, and these are briefly discussed.
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New Zealand Plant Names Database
Phylogeny of New Zealand Plants
Flora of New Zealand Series
1 - Landcare Research, Allan Herbarium, P.O. Box 69, Lincoln, 8152, New Zealand
2 - Allan Herbarium, Landcare Research, PO Box 40, Lincoln, 7640, New Zealand
3 - Allan Herbarium, Landcare Research, PO Box 40, Lincoln, 7640, New Zealand
4 - Massey University, Institute of Molecular BioSciences, Private Bag 11222, Science Tower D, Riddet Road, Palmerston North, New Zealand
5 - Department of Conservation, Science and Research Unit, PO Box 68908, Newton, Auckland, New Zealand
Presentation Type: Oral Paper:Papers for Sections
Location: Room 5/Woodward
Date: Tuesday, July 29th, 2008
Time: 2:00 PM