Diversity, Endemism, and Extinction in the Flora and Vegetation of New Caledonia
Diversity and Endemism by Vegetation Type and Substrate
Levels of diversity and endemism vary subtantially among New Caledonia's three principal vegetation types (Morat 1993).
The moist evergreen forests are the richest; the maquis vegetation has a somewhat less diverse flora; whereas the sclerophyllous forests are comparatively less diverse and have fewer endemics, although this probably reflects at least in part the fact that this formation has been reduced to a number of small, isolated stands, many of which have been partially degraded (Jaffré et al., 1993; Bouchet et al., 1995; see also below).
The richness of the moist evergreen forests is even more evident when compared with the estimated original area of each of the main vegetation types on Grande Terre. The moist evergreen forests not only have more species than the other formations, but they also occupied substantially less area prior to human impact, giving them a much higher number of species per 1000 km² of original cover. Even though this indicator probably underestimates the original richness of the sclerophyllous forests, as indicated above, floristic diversity was no doubt lower than that of the maquis, and almost surely did not approach that of the moist evergreen forests.
Levels of endemism also differ between ultrabasic and non-ultrabasic substrates, regardless of vegetation (Jaffré et al., 1987; Morat, 1993). Although the total number of angiosperm and gymnosperm species occurring in the two main formations that are present on both kinds of substrate is essentially identical, the percentage of endemism is much higher on ultrabasics than elsewhere. This pattern is also evident at the generic level.
Perhaps even more remarkable is the fact that among the 1,176 species that occur exclusively on ultrabasics (37.5% of the total flora), fully 98.0% are endemic to New Caledonia; 72 genera (9.4% of those present in the territory) are also restricted to these highly selective substrates, of which 52.8% (38 genera in all) are also New Caledonian endemics.
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