Willem M. Roosenburg, Ph.D.

     My laboratory is involved in elucidating causal mechanisms of life history variation in vertebrates.   In particular I am interested in how variation in the physical environment affects organismal physiology, behavior, and population level processes.  I am also interested in the ecological consequences of environmental sex determination (ESD) and its effect on sex ratio and sex ratio evolution.  My approach combines field and laboratory experiments with   demography to study how ecological and historical processes produce variation within and among individuals, populations, and species.

     The corner stone of my research is a long-term mark-recapture study of the diamondback terrapin, Malaclemys terrapin.  My recent findings have discovered that the sex ratio of a cohort varies from year to year and correlates well with macroclimatic averages.   Interestingly, over a ten year period the average sex ratio among recruits approximates 1:1 suggesting that despite the tendency for ESD to bias sex ratios during a given year, balanced sex ratios occur within the reproductive lifetime of a female.  Additionally, I have found that females may have the ability to manipulate sex ratio through nest-site choice.  Nest-site decision that effect sex ratio may be based on the condition of the female's offspring, in which offspring fitness can covary with their sex.   Furthermore, I am interested in egg/offspring size variation and how the maternal contribution affects the fitness of juveniles and mothers.   Finally, I am interested in the conservation and management of long-lived vertebrates, particularly species with ESD.   Much of my recent work focuses on testing turtle-safe fishing devices and investigating the habitat requirements of organisms with ESD.

Selected References:

• Roosenburg, W. M. (In Press). Hypothesis Testing, Decision Theory, and Common Sense in Resource Management. Conservation Biology.

• Roosenburg, W. M. and J. P. Green. (In Press). Impact of a Bycatch Reduction Device on Terrapin (Malaclemys terrapin) and crab (Callinectes sapidus) capture in Crab Pots. Ecological Applications

• Roosenburg, W. M. K. L. Haley, and S. McGuire. (In Press). Habitat Selection and Movement of Diamondback Terapins, Malaclemys terrapin. Chelonian Conservation and Biology.

• Roosenburg, W. M. and P. E. Niewiarowski. 1998. Maternal Effects and the Maintenance of Environmnetal Sex Determination. In: T. Mousseau and C. Fox (eds.) Maternal Effects as Adaptations. Oxford University Press. pp. 307-322.

• Roosenburg, W. M. and A. E. Dunham. 1997. Clutch and egg size variation in the diamondback terrapin, Malaclemys terrapin. Copeia 1997:290-297.

• Roosenburg, W. M., W. Cresko, M. Modesitte, M. B. Robbins. 1997. Diamondback terrapin (Malaclemys terrapin) mortality in crab pots. Conservation Biology 11:1166-1172.