Tests of life history theory are usually made by comparing clusters of traits among populations that are known or suspected to differ in some critical environmental factor. Many problems exist in these types of comparisons including obtaining accurate demographic information and identifying the unit of evolution in the field. Another area where there is a striking lack of information is on the genetic structure of life history traits. Little work has been done to separate phenotypic plasticity from genetic divergence, which would provide a basis on which selection can act. Selection is also assumed to work on each trait independently, although the occurrence of traits in specific groups might be based on complex genetic and environmental correlations. / Two populations of a local species of freshwater pulmonate gastropod, Physella hendersoni ariomus (Clench) were selected for investigation of the environmental and genetic contributions to observed life history characteristics. These populations were found to differ in size at first reproduction, fecundity, population density and size class distribution. Physico-chemical characteristics of the two habitats also varied in the levels of dissolved oxygen, dissolved calcium carbonate, pH and constancy of water temperature. / Further analyses indicated that both temperature and population source have a significant effect on the expression of life history traits for these populations. Through the use of inbred lines, the phenotypic, genetic and environmental contributions to life history traits were further delineated. Heritabilities of life history traits for these populations were generally low, and a moderate amount of non-additive genetic variance was found for estimates of growth and fecundity. Genetic correlations between size at first reproduction and later fecundity shifted in both magnitude and direction depending upon the environment in which they were measured. Phenotypic and environmental correlations between traits were generally positive and were also strongly influenced by the immediate environment. / The genetic structure of life history traits in these populations is consistent with that predicted for traits that have been subjected to strong directional selection, implicit in life history theory. The genetic divergence between these populations can therefore be attributed, at least in part, to divergent selection pressures. / Source: Dissertation Abstracts International, Volume: 48-08, Section: B, page: 2181. / Thesis (Ph.D.)--The Florida State University, 1987.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76152 |
| Contributors | GRAY, SUSAN., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 142 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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