Ms. Mcclone et al., Endemism, species selection and the origin and distribution of the vascular plant flora of New Zealand, J BIOGEOGR, 28(2), 2001, pp. 199-216
Aim To evaluate competing views on the origin and distribution of the New Z
ealand flora by testing the hypothesis that the geographical distribution o
f species is unrelated to ecological traits such as habitat requirements an
d dispersal capabilities.
Location The New Zealand archipelago.
Methods An analysis of the factors correlated with distribution and endemis
m for alpine plants within New Zealand, and for the New Zealand biota as a
whole.
Results Woody plants are highly endemic; nonendemic plants tend to be herba
ceous and are concentrated among the highly dispersible ferns and fern alli
es, orchids and wetland plants. These groups make up 32% of the total flora
but contribute 78% of nonendemics. Alpine plants with wide spatial distrib
ution tend to have greater altitudinal ranges, a broader habitat preference
and better dispersal ability.
Main conclusions Most vascular plants reached New Zealand by long-distance
transoceanic dispersal, probably during the Late Miocene to early Pleistoce
ne period. During the Miocene and Pliocene, similar climates and landscapes
to those of Australia and northern island groups, and highly invasible ter
rain, permitted dispersal of woody plants. Cooling climates and formation o
f a more mountainous, more compact landscape after that time reduced disper
sal of woody plants and favoured herbaceous, wetland and highly dispersible
plant groups. The prominence of dispersal has led to intense selective imm
igration, and is responsible for many characteristic features of the flora.
Species selection by glacial-interglacial cycles has restricted acquisitio
n or retention of cool or arid climate adaptations, particularly in the low
land flora. Endemic and range disjunction patterns in the New Zealand mainl
and are not, in general, directly caused by Pliocene inundations or the fau
lting and associated horizontal displacement of terrain that has continued
since the Miocene. They have arisen mainly through Pleistocene extinctions,
speciation and dispersal, and some patterns are strongly linked to repeate
d glaciation. Endemic centres are associated with differentiated terrain an
d climates providing isolation, distinctive environments, and habitat conti
nuity conducive to speciation.