Geographic variation in life-history and reproductive traits is frequently assumed to reflect localized, genetically based adaptation to the environment. In this study, I examine variation in the reproductive characters of house wrens breeding at two elevations in Colorado during the 1985-1987 breeding seasons. Egg and nestling transplant experiments were performed in an attempt to discover the relative contributions of environmental and genetic factors to the observed variation between sites. / Wrens breeding at low (1100 m) and high (3000 m) elevations differ in a number of reproductive characters. Wrens breeding at the high-elevation site initiated egg laying later in the season, produced larger clutches containing bigger eggs, and incubated them longer than did wrens breeding at the low-elevation site. Nestling periods were also longer at high elevation. Reproductive success (number of chicks fledged/eggs laid) was 0.5 young higher at the high site. Chicks hatched from high-site eggs were larger than were low-site chicks. This size difference was maintained throughout the nestling period. / Patterns of within-population variation in traits differed between elevations. At the low site, fitness-related traits, such as clutch size and reproductive output, were strongly influenced by date of initiation. Reproductive success was greatest for early, above-modal-sized clutches. At the high site, hatching failures associated with above-modal-sized clutches significantly reduced reproductive output. There, modal-sized clutches initiated late in the season produced the most young. / In experiments in which eggs were transplanted between sites, incubation times shifted toward those of the foster population. Although nest environment influenced incubation period, transplanted eggs rarely hatched in synchrony with eggs originating in the foster nest. In nestling-transplant experiments, chicks reared at the high-elevation site showed greater weight gain and tarsus growth than did their sibs reared at the low elevation, but, genetically unrelated chicks reared together did not differ significantly in growth. Observed differences between natural populations in embryo and nestling development are, partly, attributable to the direct effect of environmental differences. / Source: Dissertation Abstracts International, Volume: 54-07, Section: B, page: 3444. / Major Professor: Frances Crews James. / Thesis (Ph.D.)--The Florida State University, 1993.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76980 |
| Contributors | Milinkovich, Dona Jean., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 184 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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