New Zealand Journal of Botany abstracts
Evolution of the New Zealand vascular flora: regional and
provincial patterns of richness, radiation, and endemism
Geoffrey Rogers
Science & Research Unit
Science, Technology and Information Services
Department of Conservation
P.O. Box 5244
Dunedin, New Zealand
Susan Walker
Landcare Research
Private Bag 1930
Dunedin, New Zealand
Abstract Analysis of species richness, radiation,
and endemism in 171 list-regions and 19 botanical provinces of the New
Zealand botanical region indicates that the Late Cenozoic radiation of
the New Zealand vascular flora has produced divergent phylogenetic
trends in regional and provincial floras. Floristic richness at all
taxonomic levels is strongly determined by land area. After accounting
for area, most exceptionally species-rich list-regions occur
immediately east of the South Island main divide, on calcareous
substrates in West Nelson, or on several central North Island ranges.
Depauperate floras are predominantly in the south on Auckland and
Campbell Islands, and four Central Otago and two Southland ranges or
basins. Family and genus richness decrease with latitude, but it
appears that there has been compensatory radiation from a few
herbaceous families in southern island and upland floras, so that
species richness shows no latitudinal trend. We present a measure of
aggregate regional endemism that is comparable between list-regions and
provinces of different floristic richness. Offshore island groups are
the most insular floras, with exceptionally high endemism across
different taxonomic ranks; northern island floras have high degrees of
family and genus endemism and high phylogenetic diversity, while the
subantarctic island floras have high species endemism and high
radiation. In contrast, mainland botanical provinces all show average
levels of regional endemism after correcting for species richness. With
the exception of gymnosperms, the most New Zealand-endemic plant groups
have the most narrow regional distributions. We discuss latitudinal
patterns of endemism among plant groups in terms of dispersal and
adaptation. Land protection measures will achieve different
phylogenetic outcomes in different landscapes across the New Zealand
botanical region.
Keywords New Zealand; species richness;
biogeography; endemism; radiation
B02069; Received 24 October 2002; accepted 20 January 2005; Online
publication date 5 May 2005
New Zealand Journal of Botany, 2005, Vol. 43: 381–414
0028–825X/05/4302–0381 © The Royal Society of New Zealand 2005
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