[Taxacom] Fwd: Woodpeckers, primates, as well as the Wallace Line gauntlet
michael.heads at yahoo.com
Sun May 29 21:42:55 CDT 2011
In 99% of plant and animal taxa, all of the individuals have dispersed to their current location. Colonial organisms are an exception because not all the individuals have dispersed.
The interesting point with albatrosses, spore plants, marine invertebrates etc. is that you wouldn't predict their highly structured distributions based on their means of dispersal. For example, the discovery since 2000 of so much structure in marine groups came as a complete surprise and catalyzed a paradigm shift in marine biology and conservation. The particular mechanisms of homing or site fidelity differ greatly between groups. But they exist, and this means that the rifting of an island arc into two parts, for example, can eventually cause allopatric differentiation in marine invertebrates, albatrosses, etc. The birds *could* fly to the other islands, where their sister-group is, but they don't, because of ecology, behavior or whatever. The phylogenetic break between the seabirds of one island and those of another did not develop by a freak chance dispersal event that the birds could only manage once.
Wellington, New Zealand.
My papers on biogeography are at: http://tiny.cc/RiUE0
--- On Mon, 30/5/11, Kenneth Kinman <kennethkinman at webtv.net> wrote:
From: Kenneth Kinman <kennethkinman at webtv.net>
Subject: [Taxacom] Fwd: Woodpeckers, primates, as well as the Wallace Line gauntlet
To: taxacom at mailman.nhm.ku.edu
Received: Monday, 30 May, 2011, 1:11 PM
Although I was mentioned further along in your post, I will only
respond to the first paragraph (that is all the time I have tonight).
First, I don't understand why you make an exception for colonial
organisms. Although they cannot disperse very far vegetatively, they
can often disperse large distances through sexual reproduction.
As for albatrosses, I agree that they may have extremely large
feeding ranges, but reproductive needs (nesting sites, etc.) are very
limiting. It is sort of like salmon compelled to return to their
birthplace to spawn. Whether it is quite as chemically-based as salmon,
albatrosses generally return to a home-base to breed. This reproductive
bottle-neck limits dispersal at that crucial part of their life cycle.
Monarch butterflies are somewhat limited for a different reason.
Their reproductive range is actually relatively widespread in eastern
North America, but it is their particular needs for a limited wintering
ground that keeps them from dispersing further.
It only takes one restriction in one particular part of the life
cycle to keep dispersal in check. Think of it as an "evolutionary" weak
link. Albatrosses may be able to range far and wide when not
reproducing, but that critical time of reproduction for a species limits
them to a very limited breeding range. Whether this is due to predation
of chicks, availability of nesting sites, food sources to feed the
chicks, or other factors (or all of the above), it puts limits on the
dispersal of the species. So that is my answer to your questions: "Why?
Michael Heads wrote:
Every individual of every plant and animal (except in colonial
organisms) has dispersed to where it is now. The problem lies in
integrating that process - normal physical movement - with other
processes in phylogeny and geography, especially range expansion and
vicariance. The physical movement of individuals may have little or
nothing to do with the distribution pattern of their clade. Jim
pointed out the paradox in ferns and marine groups with pelagic
larvae, and many other authors have discussed the
problem. Individual albatrosses fly around the world at the drop of
a hat, and yet the clades have very precise, allopatric, locally
endemic, breeding ranges. Why? How?
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