> Despite this, response to song is a good prima facie guide to
> conspecificity
> or otherwise. And it's often the quickest thing you can detect. If
> you get
> no response, then you need to start studying other evidence.
>
To digress for a moment to flying mammals ... I've been analysing the
variations in calls (dialects or phonotypes) of Common Bentwing-bats
(Miniopterus schreibersii) in Australia. I identified clear "eastern"
and "western" dialects, with a bit of a complex mess in the isolated Top
End population. Belinda Cardinal in her BSc (Hons) from Deakin
University looked at mitochondrial DNA characteristics in the bats where
I had identified dialects, and confirmed significant "genetic
differences" between the eastern and western groups. There are some
morphological and behavioural data which further back this up. These
two phonotypes are probably in the process of speciating either side of
a divide roughly placed at Melbourne in Victoria. The western phonotype
is based on maternity cave sites at Warrnambool (Vic) and Naracoorte
(South Aust), and the eastern phonotype from East Gippsland all the way
up to North Queensland. It's tempting to see the Basalt Plains of
western Victoria as having split off a part of the previously continuous
population. So the dialects in all liklihood are not the isolating
mechanism, but something that developed after the split of the
population. Furthermore the dialects are in orientation/foraging,
ultrasonic echolocatory calls - bats make a range of audible social
sounds which are largely unstudied. The echolocatory calls are
nonetheless useful cues to something else going on, as John has
suggested.
It's here that the digression returns to birds, because the site
fidelity of Bentwing-bats to particular maternity caves is analogous to
the site fidelity of particular albatrosses to particular breeding
islands.
I hope that adds to the general confusion!
Cheers, Lawrie
Lawrie Conole
Fitzroy North, Victoria, Australia
37°46'57"S 144°58'45"E
http://www.users.bigpond.com/ocoineoil/
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