New Zealand Journal of Botany abstracts
B00013Received 8 May 2000; accepted 18 October 2000
Comparison of the flora and vegetation of the southern Andes and New
Zealand
PETER WARDLE
Landcare Research
P.O. Box 69
Lincoln, New Zealand
email:wardlep@landcare.cri.nz
CECILIA EZCURRA
Universidad Nacional del Comahue
Bariloche, Argentina
CARLOS RAMíREZ
Universidad Austral de Chile
Valdivia, Chile
STEVE WAGSTAFF
Landcare Research
P.O. Box 69
Lincoln, New Zealand
Abstract The annual range of temperatures in the southern
Andes is similar to that in New Zealand, although they are cooler at comparable
latitudes. South of 45deg.S in Chile the precipitation regime is also similar
to New Zealand, but northwards and also east of the Andes there is an
increasing period of summer dryness. There are corresponding similarities in
vegetation, especially in evergreen
Nothofagus forests, tussock
grassland in eastern rain shadows, and cushion bogs. Deciduous
Nothofagus species are absent from New Zealand, but dominate widely in
drier and colder environments of the southern Andes.
In the southern Andes deciduous Nothofagus forms the subalpine forest
and krummholz although, in the northern part of the region, there is also
Araucaria araucana growing as erect, emergent trees. Volcanic eruptions
may lower the tree limit so that it intersects with evergreen Nothofagus
forest. In New Zealand, evergreen Nothofagus species, which are less
cold-resistant than the deciduous Andean species, form most tree limits,
and a belt dominated by tall Chionochloa tussocks intervenes between
forest and low-growing alpine vegetation. The absence of very hardy tree
species in the New Zealand mountains may be related to isolation and late
uplift.
Extrapolation to tree limit indicates southern Andean warmest-month mean
temperatures from around 7deg.C in northern localities to only 5.7deg.C at
55deg.S, compared with 10deg.C which prevails in New Zealand. Since tree limit
altitudes in the Southern Andes exceed those of New Zealand by at least
250 m, this indicates that in temperature terms New Zealand tree limits
are 550 m lower than those of the southern Andes, corresponding with
summer isotherms 3.3deg.C warmer.
Vascular species were listed from equivalent vegetation types in the southern
Andes and New Zealand, including forest, rain-shadow grassland, alpine,
coastal, swamp, lake-edge, and bog vegetation, and also from communities near
the upper tree limit without close equivalents, notably deciduous forest in the
Andes and Chionochloa grassland in New Zealand. Phytogeographic
categories were assigned to all species, genera, and families. These were
grouped as shared-austral, shared with wider distributions, "realm-endemic"
confined to either South America or Australasia, and non-shared with wider
distributions.
About 90% of the 465 species listed from the southern Andes and 522 listed
from New Zealand are realm-endemics. Forty species or closely related pairs of
species are shared, nearly half of these being coastal. Among genera,
realm-endemics are the largest element overall and exceed 30% in forests of
both regions and in New Zealand subalpine, grassland, alpine, successional, and
bog vegetation. Shared genera that extend to north temperate regions form the
next most important, reaching over 40% in southern Andean swamp and New Zealand
coastal samples. Shared genera with austral distributions reach 21-32% in all
New Zealand vegetation classes and southern Andean bog, compared with 5-20% in
other southern Andean vegetation classes. They contribute disproportionately to
the physiognomic similarities between the two regions, notably in
Nothofagus forests and bogs.
Non-shared genera with austral or subtropical distributions are most numerous
in forest samples from each region. Non-shared genera with north temperate
distributions constitute only 2% in New Zealand, contrasting with the southern
Andes where they constitute 19% overall and 20-29% in subalpine, grassland,
alpine, successional, and coastal vegetation. Distribution of families among
phytogeographic categories is similar to that of genera, except that more are
shared-widespread and fewer are shared-austral and realm-endemic.
Sequencing of the gene rbcL for pairs of taxa in shared-austral genera
and for populations of Hebe salicifolia yields divergence estimates
ranging from 130 ± 75 to 7 ± 4 million years. Divergences among
tree species in shared genera may predate the separation of Australasia from
Antarctica and South America, but not the separation of New Zealand from
Australia. Taxa of open habitats show the most recent divergences, and their
presence in both regions demands some mode of transoceanic dispersal. Possibly
as late as the Pliocene, this may have involved a partly vegetated Antarctica.
Keywords climate; DNA sequencing; evolutionary divergence;
New Zealand; Nothofagus; phytogeographic category; southern Andes;
taxonomic rank; tree limit; vegetation
New Zealand Journal of Botany, 2001, Vol. 39: 69-108
0028-825X/00/3901-0069 $7.00 (c) The Royal Society of New Zealand 2001
PDF file of entire paper: medium quality (12480K); (scanned from paper original: notes about this process)
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