Thirteen New World populations of Megachile rotundata and M. apicalis and
two Old World populations of M. rotundata were analyzed at 23 enzyme loci using
cellulose acetate electrophoresis. Conventional and G- or C-banded karyotypes were
also examined in these populations. The principal findings are (1) No differences
were found in the level of heterozygosity between haplodiploid Megachile and that of
other diploid insects. This is the first record showing the mean heterozygosity in the
hymenopteran genus to be consistent with the mean of most other diploid insects. (2)
There was no difference in the level of heterozygosity nor the percent polymorphic
loci between males and females, and heterozygotes was discovered in males of the
two megachilid species studied. (3) The heterozygosity levels among New World
populations of M. rotundata and M. apicalis were similar, but both were more than
twice that of Old World rotundata analyzed. This is consistent with the expectations
of the founder-event models of both Carson and Templeton. (4) FST, the amount of
genetic differentiation among populations, was greater among New World populations
of apicalis sampled than among those of rotundata. The extensive commercialization
in rotundata may have tempered interpopulation differences which might had
occurred had the species been undisturbed. (5) Wrights "isolation by distance" model
is inapplicable to either of the two Megachile species. In rotundata, the high gene
flow level suggests that human commercial action may effectively disrupt any
opportunity for the development of locally adapted populations through selection. In
apicalis, little gene flow is present among the populations which is expected by both
Carson and Templeton models. The absence of any clinal pattern in apicalis probably
better reflects Templeton's transilience model. We believe that the random alteration
of major alleles, implicit in transilience, more readily accounts for the distinct local
populations we found in apicalis. (6) Chromosomal data suggest that both pericentric
inversions and deletions have been involved in karyotype evolution of the two species
and a primitive karyotype is proposed based on its ubiquitousness in all populations of
both species. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/37250 |
| Date | 28 September 1992 |
| Creators | Chen, Xiaoshe |
| Contributors | Stephen, William P. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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