numbers game or counting

[Kenelm Philip]

Mike Gochfeld inquired:

> Judging from the Azure problem, how would you distinguish (based on field
> data)  two non-overlapping, morphologically distinct "species", from one
> bi-voltine species exhibiting polyphenism.

If all you had was a series of counts from one site, showing clearly-sep-
arated flights (like so: _____/\_______/\_____) I would say you needed
additional data.  :-)

In the case of the Interior Alaska _chariclea_/_'titania'_ problem, the
situation is different. First, there is, at all sites, a bit of
overlap of the flights, with worn _chariclea_ flying with fresh _'titania'_.
Second, up here these are all single brooded species, and in any case there
isn't enough time for the _chariclea_ to produce another brood which
emerges as _'titania'_. In addition, the _chariclea_ flies in odd-numbered
years only, while the _'titania'_ flies every year. Hard to get _that_
pattern from a bi-voltine species!

In Interior Alaska _chariclea_ (normally a late-summer species in the
tundra on the North Slope) emerges earlier at lower elevations, showing up
in mid-summer in tundra just above treeline, and in early summer in the
taiga. _B. 'titania'_ is limited to the taiga and flies in late summer.
If the _'titania'_ were a second brood of _chariclea_, produce only at
lower elevations, it wouldn't have time to feed up and emerge in _early_
summer next year. And the odd-year _chariclea_ flight cannot be explained
by having it arise from _'titania'_.

Although it was at one site (Goldstream, near Fairbanks) that I first
observed this situation, we now have observations of _chariclea_ flying
earlier than _'titania'_ in a number of locations in Interior and south-
central Alaska taiga. At all of these sites, there is a little overlap
between the two flights:
                                 /\  /-----\
                 _chariclea_    /  \/       \  _'titania'_
			_______/___/\________\______

I see no way of explaining all this as a single bi-voltine species.

							Ken Philip




 
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