[Taxacom] an interesting paper on Long Distance Dispersal
watling at hawaii.edu
Wed Jul 4 12:41:16 CDT 2018
Apropos the recent discussion re dispersal vs vicariance. As a recent paper
in PeerJ makes clear, the size of the dispersing organism matters. As does
mobility, and a host of other factors.
In the case of tardigrades it was long assumed that wind was the major
dispersion agent, but the authors demonstrate, as much as one likely can,
that bird feathers are an effective agent for something as small as a
Not a too-likely method for primates other than in sci-fi stories(!).
Primates probably could wander long distances, but why would they?
Especially if their needs are being met where they are. In which case
rafting on continental chunks might be what carries them around.
But I think bird feathers also work for seeds of some species, and
something as unusual as terrestrial amphipods. In Hawaii, some animals,
such as terrestrial amphipods have no likelihood of dispersing over the sea
on rafts or other floating objects because of their osmotic intolerance to
sea water. On the other hand, we also know that certain marine taxa, such
as cumaceans, which are small benthic crustaceans with almost no swimming
ability and no larvae, have not made it to Hawaii. Most likely that is
because they could only get there by travelling along the bottom, meaning
they would have to crawl through the abyss.... not going to happen,
temperature and pressure. But 3 species of cumaceans have now made it, most
likely in ship ballast water.
As with cumaceans, shallow water octocorals, a regular feature of most
tropical coral reefs, are essentially absent from Hawaii. There are a few
(maybe 4?) species of very small soft corals that can be found in shallow
pools or in water a few meters deep. But the normal reef habitat has no
octocorals. However, at depths greater than about 350 m, octocorals become
abundant and diverse, exceeding more than 100 species, and inhabiting
depths to over 3000 m. So the deep sea species have made it, easily, but
the shallow species have not. Low dispersal capability in the latter, and
long distance larvae in the former?
In the end, I think the debate needs to be more carefully circumscribed
with respect to the organisms. And, from where I sit, I see both
panbiogeography and LDD each explaining some patterns.
Professor, Dept. of Biology
216 Edmondson Hall
University of Hawaii at Manoa
Honolulu, HI 96822
e-mail: watling at hawaii.edu
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