hybrids and genera

Michael Gochfeld gochfeld at eohsi.rutgers.edu
Sat Apr 29 21:26:04 EDT 2000

"If they are close enough to produce hybrids they are the same genera". 

For what it's worth, there was a lot of discussion at one time about 
intra-generic vs inter-generic hybridization in hummingbirds. The 
argument was made that selection for intra-specific mate recognition had 
been "perfected" to reduce or avoid hybridizing with closely related 
species. However, since hybridization among more distantly related 
species may have been too infrequent to be selected against, you were 
more likely to encounter intergeneric hybrids since there were 
behavioral or other mechanisms to avoid intrageneric hybridization. 

It sounds more far-fetched now than it did then (circa 30 years ago), 
but at least it is a countervailing argument to the one mentioned above. 

Since there are no rigid biologic criteria for whether to raise 
Pterouris, Heraclides, etc to generic level or treat them as subgenera, 
 it must hinge on how an individual systematist views them. I'll hazard 
a guess that if one is really a lifelong specialist on a particular 
group, they are more likely to be impressed by the subtle differences 
among its members (hence more likely to elevate to the generic level), 
while to those who look at a whole fauna, the differences between a 
Tiger and Giant and a Spicebush Swallowtail, may not seem to warrant 
generic recognition. 

I also remember a discussion circa early 1970's about whether there was 
some optimum number of species for a genus (i.e. whether too big a genus 
was unwieldy and whether monotypic genera were a waste).  

M Gochfeld 

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