Mary H. Lee

CURRENT RESEARCH

Predators can induce a wide range of antipredatory responses in larval amphibians to reduce predation.  For example, prey can change their morphology, physiology, life history, or behavior in response to the presence of a predator.  However, some responses which reduce detection by a predator may increase fitness costs.  For example, behaviors such as reducing activity, shifting microhabitat use, and spending more time in a refuge may increase fitness costs by inhibiting thermoregulation, reducing resource acquisition, and increasing competition for resources by concentrating prey in one area.  In larval amphibians, these costs may result in smaller sizes at metamorphosis, which is correlated with low survivorship after metamorphosis and smaller size at reproductive age.   My research investigates this survival and growth trade-off in tadpoles of the African clawed frog, Xenopus laevis.  This is a unique system in that the most detrimental predator to the tadpoles is probably adult frogs of the same species, thus I use post-metamorphic conspecific frogs as the predator.  Current projects include determining the behavioral and morphological responses of tadpoles towards cannibalism, determining the cues which elicit such responses, determining the fitness costs of the antipredatory responses, and determining if there are any evolutionary adaptations to lessen fitness costs.

STUDY ORGANISM

The African clawed frog, Xenopus laevis, is aquatic during all life stages and thus lives in the same habitat as its young.  Xenopus laevis is native to sub-Saharan Africa where it is abundant and found in virtually all bodies of water including rivers, lakes, dams, swamps, ditches, and wells.  They can tolerate a wide range of water chemistry (nutrient levels, pH, and salinity), and thrive in man-made habitats.  They are such good colonizers that a number of feral populations have been established around the world due to human introduction through use in human pregnancy diagnosis, research laboratories, and the pet trade.  Feral populations have been found in the U.K., Germany, Netherlands, Chile, Ascension Islands, and in 11 U.S. states.  Populations in California have become so successful that attempts have been made at eliminating X. laevis.  These attempts have been unsuccessful and the population has been deemed as uncontrollable.  The success of this species can be attributed to the ability of adults to move over land and colonize highly disturbed areas before prey are available and competitors and predators appear.  It is believed that cannibalism enables adults to survive food shortages and establish new habitats.  Their high reproductive rate leads to large populations of tadpoles that feed on seasonal algal blooms.  Those tadpoles, in turn, are exploited as prey by adult frogs.  Field studies of both native and feral populations have found post-metamorphic frogs of all sizes to cannibalize eggs and tadpoles.  When tadpoles were taken as food, they usually made up the bulk of the diet.  In the closely related X. clivii, there is evidence that some populations exist entirely on conspecific tadpoles.  It is currently unknown how cannibalism effects the mortality rates or alters the population dynamics of X. laevis, and how tadpoles have responded to the potential selection pressure resulting from conspecific predation.

Tinsley, R. C. and H. R. Kobel.  1996.  The biology of Xenopus.  Oxford Univeristy Press, Oxford.

LINKS

Some links to my CV and pictures of some really neat places I've been.....

Curriculum vitae

Costa Rica trip 2002

India trip 2003                          

Illinois Herps                               

My zoo

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