Biology Reference
In-Depth Information
that now rivals its unique native flora in species richness (Wagner et al. 1990).
Many alien species (e.g.,
Clidemia hirta, Hedychium gardnerianum, Pennisetum
setaceum, Psidium cattleianum
) have become invasive over the last 150 years
(Stone et al. 1992).
Among these invaders is the small tree
Miconia calvescens
(Melastomataceae),
a native of Central and South America (Meyer and Florence 1996). Miconia's his-
tory of introduction into Hawaii has been thoroughly reviewed by Medeiros et al.
(1997), and we only summarize those events here. Most relevant to the failure to
eradicate this tree once it was detected in Hawaii is its known record of invasion in
French Polynesia, where it was introduced into a botanical garden in Tahiti in 1937.
It escaped, dispersal probably facilitated by birds that could carry its seeds to inac-
cessible sites on the craggy volcanoes on Tahiti and Moorea. The tree's tolerance
of light regimes inside the islands' native forests meant that it could not only persist
inside these forests (Fig. 3.4), but also that its rapid spread remained virtually unde-
tected, including in aerial photographs (J-Y Meyer, pers. comm.). Prospects for
Miconia's control, much less eradication, now seems daunting. Much of the forests
on Tahiti and Moorea is now dominated by
M. calvescens,
and the consequences of
this aggressive invader will almost certainly be played out in the future in a general
Fig. 3.4
(
a
)
Miconia calvescens
has been dispersed by birds and storms across much of Tahiti,
French Polynesia, including steep mountaintops; these sites are inaccessible by humans, thereby
virtually precluding Miconia removal. (
b
) Once Miconia invades native forest it soon totally
dominates the understory and eventually the overstory as well (Note the person in background is
largely obscured by Miconia juvenile plants) (photos by R.N. Mack)
