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120 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY
phantopus are common associates. Megalapteryx didinus,
however, also is common, especially in hill sites, which reflects
the presence of upland shrubland habitats, as this species dominates
subalpine Holocene deposits. In central Otago, the smaller
carinates are better represented in late-Holocene deposits
than in older deposits, but, even so, they are not easily compared
with those of other eastern areas because they do not include
faunas accumulated by predators. As in Eastern faunas,
Euryanas finschi is abundant, Sceloglaux albifacies, parakeets
{Cyanoramphus spp.), New Zealand Snipe {Coenocorypha
aucklandica), Gallinula hodgenorum, New Zealand Pigeon
{Hemiphaga novaeseelandiae), and Coturnix novaezelandiae
are common, Cnemiornis calcitrans is present, and Gallirallus
australis and Apteryx spp. are relatively rare. Nestor notabilis
is more abundant than in other regions, which also reflects the
presence of substantial areas of upland habitat.
The Anomalopteryx assemblage characterized rimu-dominated
podocarp forests of the west coast and central North Island
and the beech forests of Takaka Hill and Mt. Cookson during
the Holocene. This observation supports the contention of Graham
(1992) that vegetation structure may be more important to
some animals than the species composition of the vegetation.
Although these areas differed markedly floristically, they presented
a common structure of a continuous closed canopy that
excluded significant areas of grassland and shrubland.
THE QUESTION OF PLEISTOCENE EXTINCTIONS
OF MEGAFAUNA
The faunal turnover at the end of the glacial period in New
Zealand has considerable international relevance to the worldwide
debate on the cause or causes of Pleistocene extinctions
of megafauna, whether climate-induced or attributable to overkill
by humans (Martin and Klein, 1984; Graham, 1986). The
term megafauna has been defined in various ways, although
most definitions encompass the larger species (Martin and
Klein, 1984). In Australia, megafauna is often used for all species
that went extinct in the late Pleistocene, regardless of size
(Murray, 1991). In New Zealand, as elsewhere in the world,
larger species were more susceptible to extinction, with all terrestrial
birds greater than two kilograms becoming extinct
(Cassels, 1984). The faunal changes documented for western
areas of the South Island (Worthy, 1993a; Worthy and Holdaway,
1993) demonstrate that in New Zealand there were extinctions
at the end of the Pleistocene, but they were only regional
in extent. These are equivalent to the faunal shifts
commonly related to past climatic changes in Quaternary faunas
of Australia (Lundelius, 1983) and North America (Graham,
1987, 1992; Graham and Grimm, 1990).
The warming climate in New Zealand produced habitats
characterized by continuous tracts of closed-canopy forest for
which the members of the Euryapteryx assemblage were not
adapted, and so they were displaced by the Anomalopteryx as­
semblage. Such faunal shifts support the environmental
change/habitat destruction hypothesis advocated as causal for
North American Pleistocene extinctions (Graham, 1986). In
New Zealand, however, all known species survived into the
last millenium, with local adjustments in range. The Euryapteryx
assemblage was restricted to the areas of grassland, shrubland,
and forest mosaics that persisted east of the Southern
Alps. Their continued survival in these areas could be considered
an accident of geography because the Alps create a rainshadow,
hence the dry conditions necessary to maintain this
vegetational mosaic. But this is not the only reason because in
the North Island and along the Southland coast, the ecotonal
dunelands present a fundamentally similar vegetation structure,
albeit in very small areas, sufficient for the survival of the
dominant Otiran species alongside members of the Anomalopteryx
assemblage. Also, the past survival of these species
through several glacial-interglacial cycles suggests that they
were not at risk of extinction in this last cycle. All moas, indeed
all of New Zealand's Late Quaternary terrestrial species that
eventually became extinct, did so only after humans arrived,
about 800 to 1000 years ago (Anderson, 1991).
In North America, greater habitat heterogeneity during the
glacial and late glacial is associated with faunas of higher species
diversity than those of the Holocene, so the loss of this
habitat variety may have contributed to megafaunal extinctions
(Graham, 1985, 1986). In New Zealand, although the members
of the Euryapteryx assemblage lived in the areas of most heterogenous
habitat, the greatest species diversity was achieved not
in glacial times but rather during the late Holocene, when the
warm-temperate forest element populated the forest segments
of this mosaic. It may be equally valid to argue that, in a landscape
that was otherwise forested, the species with requirements
for grassland and shrubland habitats found refuge in
these mosaics. That all members of the Euryapteryx assemblage
became extinct seems to support the concept that the loss
of habitat heterogeneity was important in the extinction event.
Countering this, however, is the fact that many members of the
Anomalopteryx assemblage also became extinct.
The presence of heterogenous habitats are not implicitly a
glacial/late glacial phenomenon, as inferred for North America
by Graham (1992), but are rather a function of water availability
and ecotonal habitats. That species with preferences for open
areas, such as grassland, closed forests, or forest margins, can
all find available habitat in such areas contributes to high species
diversity. In New Zealand, forest remnants in the vegetational
mosaics probably provided the source from which the
members of the Anomalopteryx assemblage spread to dominate
the faunas of the new closed-canopy forests of the Holocene.
Conversely, at an earlier stage of the glacial-interglacial cycle,
the Euryapteryx assemblage spread from remnant mosaic habitats
existing in the last interglacial to dominate the open glacial
landscapes.