It is self-evident that intentional production of hybrids
can be immensely informative with respect to specific hypotheses
or general evolutionary questions. For example, Doug McElroy and
I crossed _Labeotropheus fulleborni_ X _Pseudotropheus zebra_ to
examine development and expression of jaw phenotype; our analyses
(Copeia 1993:933) suggested that hybrids can develop unique
morphologies outside of the range displayed by their parents.
The production of hybrids from known parents under controlled
conditions can help address questions about the genetic underpin-
nings of behavior and morphology, though for haplochromines, I
think it unlikely that such studies will provide insight into the
mechanics of speciation. The relatively small number of eggs and
high variance in fecundity in these fishes may confound attempts
to measure selective differentials unless proper replication and
controls are in place.
Regarding _Cichlasoma minckleyi_ , my students and I estab-
lished conspecificity of trophic morphs beyond reasonable doubt
by demonstrating random mating in situ (Evolution 36:658); that
study corroborated the earlier insight of Dick Sage and Bob
Selander who examined the problem using allozyme markers. The
genetics underlying morphology in these beasts is unresolved;
Jeff Taylor and I did some preliminary experiments several years
ago, but critical crosses of molariform X papilliform morphs were
not completed. Indeed, the experiments still need to be done.
Note that it is clear from a fair number of studies on both New
and Old World cichlids that diet can alter pharyngeal dentition.
Finally, it is important to understand that while the genetics
underlying pharyngeal morphology in these fishes is of general
interest, is not necessary that it be known in order to resolve
the issue of specific status.
Irv
Irv Kornfield
Dept. of Zoology net: irvk at maine.maine.edu
University of Maine tel: 207-581-2548
Orono, ME 04469-5751 fax: 207-581-2537
USA ftp: 130.111.57.31