Reproduction and survival strategies in various animals: Assumptions and predictions of adaptational hypotheses.

Several related theories that predict optimal reproductive and survival strategies are examined in detail. First, theories regarding the evolution of sex determination in reptiles are analyzed. Then, various optimal egg size theories and their assumptions are examined, utilizing data from numerous taxa. Tests of a prominent offspring sex allocation theory are also reported. Finally, results of predator-prey experiments are analyzed. Allozyme data are used to test criticisms of two recently proposed theories that purport to explain interspecific patterns of sex determination mode in reptiles. Phylogenetic analyses suggests that change between modes is common, thus the current pattern is not due to simple conservation of ancestral mode. Temperature-dependent differential fitness remains the most plausible hypothesis, although there are few data that are clearly supportive. Longevity is estimated in a small group of geckos (Phelsuma) with both sex determination modes. Contrary to predictions, there is apparently little difference in longevity between species with different modes. Turtles appear to fit the explicit assumptions of optimal egg size models particularly well, yet they do not support the models' predictions. There are numerous implicit assumptions of the models. A strong correlation between body size and egg size is demonstrated using meta-analysis. If this correlation has a genetic basis, selection may not be able to act on egg size without also affecting body size. One prediction from sex-allocation theory is that under certain conditions, females with above-average levels of resources bias their offspring sex ratio towards sons. Results reported here demonstrate that white-tailed deer (Odocoileus virginianus) behave according to this theory, while a fruit fly (Drosophila melanogaster) does not. It is suggested that Drosophila may not have the ability to adjust offspring sex ratio, an ability assumed by the theory. The relationship between tail autotomy, body size, and risk of predation in the gecko Coleonyx variegatus is examined experimentally. Contrary to both predictions based on field observations and the findings of previous researchers, neither factor appeared to influence capture success by the night snake (Hypsiglena torquata).PhDBiological SciencesEcologyZoologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/129426/2/9513309.pd