dmark@acsu.buffalo.edu (David Mark) (09/14/90)
In article <1201@cluster.cs.su.oz.au> andrewt@cluster.cs.su.oz (Andrew Taylor) writes: > >It seems to me this only helps in the easy case. If the ranges of two >populations overlap but they never interbreed then you call them separate >species. But what does the A.O.U do if the ranges don't overlap (common >in Australia) and surely it doesn't declare two populations to be >the same species just because interbreeding has been recorded? > >Andrew The A[merican].O.U. uses a complicated set of criteria related to interbreeding or potential interbreedings: for populations which overlap in the wild in their breedings ranges, there is a complicated set of criteria, based on Ernst Meyer's work. To simplify, if both parental genotypes occur throughout the zone of overlap, then they do not lump them, no matter how much interbreeding there is. (The best case I know: Larus glaucescens [Glaucous-winged Gull] and L. occidentalis [Western G.] interbreed freely all along the coast of the State of Washington, and hybrid pairs even produce more offspring per pair than 'pure' pairs, yet they are not lumped because both parental types occur throughout.) If there is a 'blending' zone of all hybrids, then they are lumped. For allopatric (non-overlaping) populations, the ornithologists use behavior (especially vocal these days) and habitat, and other circumstantial evidence to make a conjecture on what would happen if their breeding ranges came in contact. Thus Florida Scrub Jays are currently in the same species as western US populations, but the two small nuthatches of the pines (Brown-headed in the east; Pygmy in the west) are separate. Etc. For allopatric populations, species status is very hypothetical. David Mark dmark@acsu.buffalo.edu