Office: Mueller Laboratory, room 508
BA 2007 University of Pennsylvania
MES 2008 University of Pennsylvania
PhD 2013 Penn State University
Every organism must make high-impact decisions in order to reproduce. Deciding when, where, and with whom to mate can easily “make or break” an individual’s seasonal or even lifetime fitness. The diversity of mate choice strategies apparent in nature implies that species have optimized their behavior for these important decisions. I am interested in learning why individuals choose the mates they do under the particular ecological conditions common to their species. Specifically, I would like to better understand if and how individuals modify their reproductive strategies in response to social or environmental pressure, to maintain maximum fitness in the face of constraints.
Reproductive behaviors and phenotypes are extremely relevant to species’ ecology, as organisms are required to advertise for mates and provide for offspring despite challenging environments filled with predation, competition, and limited resources. In spite of these challenges, some individuals are highly prolific. Why do these individuals “win” the reproductive game, and not others? What makes their strategies better? Better understanding these questions may help inform why contemporary reproductive strategies evolved in the ways they did, and in what capacity species may be able to adapt their reproductive strategies in a changing environment.
I primarily use two excellent study organisms in my research of sexual selection and strategy: fence lizards (Sceloporus undulatus) and wood frogs (Rana sylvatica). Individuals from both species typically have multiple mates over a lifetime, males compete over access to females, and females do not receive direct (i.e. material) benefits from their mates. In many ways, these study species embody the typical Darwinian stereotypes of males and females—coy females and combative males. However, these species differ in their operational sex ratios, their degrees of male-male competition, and their abilities for individuals to make mate choice decisions. Fence lizards reproduce throughout a season, females may mate multiply and can store sperm from previous matings, and my research suggests that females even make mate choice decisions on male traits. On the other hand, wood frogs are “explosive breeders” and all reproductive activity is conducted during a two week period. This frenzy of breeding results in scramble competition, where little to no mate choice is exercised. Even when given the opportunity in the absence of male-male competition, my research suggests that male frogs do not choose the mates that might significantly increase their fitness.
Please visit the research page on my personal website to
learn more about my current research, and about my
past research projects.
Swierk, L. and T. Langkilde. 2013. Bearded ladies: Females suffer fitness consequences when bearing male traits. Biology Letters 9: 20130644.
Swierk, L. and T. Langkilde. 2013. Sizing-up the competition: Factors modulating male display behavior during mate competition. Ethology 119: 948-959.
Swierk, L., A. Myers, and T. Langkilde. 2013. Male mate preference is influenced by both female behaviour and morphology. Animal Behaviour 85: 1451-1457.
Brossman, K.H., B.E. Carlson, L. Swierk and T. Langkilde. 2013. Aquatic tail size carries over to the terrestrial phase without impairing locomotion in adult eastern red-spotted newts (Notophthalmus v. viridescens). Canadian Journal of Zoology 91: 7-12.
Swierk, L., M. Ridgway, and T. Langkilde. 2012. Female lizards discriminate between potential reproductive partners using multiple male traits when territory cues are absent. Behavioral Ecology and Sociobiology 66: 1033-1043.
Swierk, L. 2012. Rana sylvatica (Wood Frog): Larval duration. Herpetological Bulletin 119: 39.
Swierk, L. and Langkilde, T. 2009. Micronutrient input into a mangrove ecosystem in Jobos Bay, Puerto Rico, by the exotic green iguana Iguana iguana. Current Zoology 55: 435-438