Sailfin mollies, Poecilia latipinna, display dramatic interdemic variation in average male body size. Size at maturity in sailfin mollies is a one locus Y-linked trait with a minimum of four alleles; males are the heterogametic sex and grow little after maturing. / Most of the variation in male size is expressed among local demes. I sampled from sixty molly populations from the eastern third of their range and found regional differences explain 6% of the total variation in male size, local differences 20%, and seasonal differences 5%. Furthermore, there is no correlation of habitat type to average male size or spread of male sizes. I constructed an index of the habitat experienced by each population through principal components analysis. The index proved to be uncorrelated with male size variation using Mantel's method. / I found sailfin mollies to have a high migration rate among demes such that stochastic population genetic processes are an unlikely explanation of their extensive local size variation. I determined this though a survey of allozyme variation at thirty presumptive loci. Approximately 20% of allozyme variation is among geographic regions, while only 3% of allozyme variation occurs within regions. / I have found both environmental and genetic bases for size variation through reciprocal transplant experiments conducted in field cages. Most of the genetic variation in size at maturity is present among family groups within demes. A laboratory factorial experiment allowed me to determine that male size at maturity is conserved across a range of temperatures, salinities, and food levels. Males matured later, but at the same size under relatively cool conditions. / The discrepancy in geographic variation of allozymes and size indicates selective intensities differ for these traits. I argue that this suggests selection shapes size variation. I found independent evidence for the operation of selection on size in my field experiment; relatively large fish at three weeks of age were more likely to survive to maturity under some conditions. Also, I reared large males in the lab from one population where large mollies have never been collected. The laboratory results exclude environmental influence as an explanation for this discrepancy. / Source: Dissertation Abstracts International, Volume: 47-12, Section: B, page: 4755. / Thesis (Ph.D.)--The Florida State University, 1986.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76009 |
| Contributors | TREXLER, JOEL C., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 193 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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