[Taxacom] Tonga-Hunga Ha'apai & biogeography

[John Grehan]

The recent eruption of Tonga-Hunga Ha'apai is a reminder of the tectonic
processes operating in the long term persistence of taxa on volcanic
islands. In this case the volcano is part of a system of volcanoes along
the Tonga Trench. Periodic eruptions are essential for the long term
persistence of islands that allow for the concurrent persistence of animal
and plant life. When new volcanoes generate sufficiently  long-lived
islands they are going to be colonized by whatever organisms can encompass
the new landscape within their distribution range (i.e. they have the
necessary means of dispersal). What will happen is that colonization takes
place by organisms already present in the local region. That way, when
older islands erode or subside, animal and plant life survive on the new
habitat. Organisms that form metapopulations involving more than one island
are more likely to survive in the long run (just as true for continental
biota that occupy multiple habitat islands). Its a dicey process, but the
biogeographic patterns suggest that many taxa involving Tonga and other
oceanic islands have persisted this way for tens of millions of years, in
this case from the time the subduction zone rolled back from its former
position along  the East Gondwana coastline.

John Grehan