Graduation Year


Document Type




Degree Name

Master of Science (M.S.)

Degree Granting Department

Biology (Integrative Biology)

Major Professor

Deby L. Cassill, Ph.D.

Committee Member

Michelle Green, Ph.D.

Committee Member

Catherine Macdonald, Ph.D.

Committee Member

Melanie Riedinger-Whitmore, Ph.D.


conservation biology, evolutionary ecology, maternal risk-management, recovery index


Every generation, breeding females and males repopulate ecosystems with the next generation of offspring. Two models link maternal investments in offspring size and number to natural selection processes. In unstable resource environments, bet-hedging models predict a conservative tradeoff in maternal investments resulting in moderate egg size and clutch size within a given range of sizes for a given species. r/K selection models make predictions on maternal investments across species. In unstable resource environments, r-selected species invest in large broods of small offspring. In stable environments, K-selected species invest in small broods of large offspring. The maternal risk management model predicts that weak-selection environments select for small broods or small offspring; unstable resource environments select for large offspring independent of brood size; high predation environments select for large brood size independent of offspring size. Elasmobranchs, exhibiting a variety of reproductive strategies are a model group for testing maternal investment models. In this study, I show maternal investments were consistent with the predictions of the maternal risk management model. Pup size and litter size were independent. Prey size, a proxy for unstable resource environments, was a predictor of female size and pup size, but not litter size. Predation was a strong predictor of litter size, but not pup size. In summary, I discuss the potential for maternal risk management as a unified model of life-history adaptations and its value to conservation initiatives.

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Biology Commons