[Odonata-l] Meadowhawks: two species in close proximity? -
Fri, 27 Jun 2003 09:56:26 -0700
Your second meadowhawk is also Sympetrum ambiguum, in my opinion. S.
vicinum has no black markings on the sides of the abdomen and no real
pattern on the sides of the thorax. So you had one species
coexisting there! However, it's almost the rule in Sympetrum to
find more than one species in a wetland, at least at higher latitudes
where there are more species - I've seen that in late summer in
Europe, Asia, and North America.
In Washington we often find up to 3 or 4 species occurring together.
They consist of species that breed in ephemeral ponds (internum,
obtrusum, pallipes) and those that breed in more permanent ponds and
lakes (corruptum, costiferum, danae, illotum, madidum, occidentale,
vicinum), but sometimes these two types of habitats are adjacent, so
at times you can find 5 or more in the same place. We often find
them interspersed around a wetland in ways that defy understanding of
any ecological or behavioral differences among the species. There
are some differences in perch sites of mature males at the water,
e.g., pallipes prefer to perch up in the shade in shrubs and trees
more than do internum and obtrusum, which are more likely to be out
in the open in marsh vegetation. S. costiferum males perch over open
water, danae back in the vegetation where they occur together.
Immature individuals seem thoroughly mixed when away from the water.
S. corruptum is a migrant, S. illotum a spring or multi-brooded
species, while the others emerge in summer and breed in fall. One
interesting question is why Sympetrum is such a northern group,
diversity decreasing sharpy as you proceed south through the US.
Sympetrum season is barely starting here.
>My thanks to all who have replied on this matter. It is interesting
>to note that the referred-to papers seem to emphasize differences in
>perch selection when two Sympetrum (or is it Sympetra?) species
>coexist; the thing that struck me as odd in my case was that the two
>dragons seemed to be using the same microhabitat. I've put pics of
>them at the bottom of this web page:
>- maybe my ID is wrong, in which case all this is moot....
Dennis Paulson, Director phone 253-879-3798
Slater Museum of Natural History fax 253-879-3352
University of Puget Sound e-mail firstname.lastname@example.org
1500 N. Warner, #1088
Tacoma, WA 98416-1088