Biogeography & relationships

[Robert Mesibov]

Tom DiBenedetto:

"The first one concerned
 > reticulation evolution in a Tasmanian conifer genus. The evidence comes
 > from total-genome DNA fragment analysis and from geographical mapping: the
 > putative hybrid occurs only where the putative parents are sympatric.
 > Imagine for a moment that the putative hybrid had instead been found in New
 > Zealand. New hypothesis, maybe?
As to the mechanisms of how the evolutionary event happened, yes - maybe.
But a
new hypothesis as to the relationships - no, not necessarily. If the
character evidence
indicated that a newly discovered New Zealand species were actually a
hybrid of two
Tasman species, would you advocate denying that conclusion simply because you
could not immediately envision how the hybrid got to New Zealand?"

No! The relationship story is unaffected, but the evolutionary picture is
dramatically different. The phylogenetic hypothesis that the hybrid is a
recent one arising in Tasmania goes out the window, and a new one pops up
showing the hybrid arising maybe 100 my ago before Australia/Tasmania split
from New Zealand. This is important for phylogeny seen as a history of
evolutionary events, but obviously unimportant for phylogeny seen as an
abstract of that history, i.e. as timeless relationships.

Dr Robert Mesibov
Honorary Research Associate
Queen Victoria Museum and Art Gallery
Home contact: PO Box 101, Penguin, Tasmania, Australia 7316
(03) 64371195; 61 3 64371195