AICME II abstracts

Behaviour-mediated population dynamics

Role of mate search, mate choice and divorce rate in population dynamics of sexually reproducing species Ludˇek Berec1 and David S. Boukal2 . Evolution of sexuality and various implications of sexual reproduction are currently in focus of both empiricists and theoreticians. In many animals, successful reproduction requires paired individuals and there exist numerous ways pairs are being formed and maintained. Three major processes play a significant role in pair dynamics: mate search, mate choice, and breakup of established pairs. Many animals are known to avoid or reduce reproduction with mates belonging to incompatible or non-preferred phenotypes [4]. Also, animals vary widely in their fidelity; in some birds individuals tend to maintain life-long pair bonds, whereas in other species they experience many partners during their reproductive lifespan [3]. Mate search, mate choice and divorce behaviour are apparently intertwined. It is now believed and partly supported by evidence that divorce is an adaptive strategy of an individual to improve its reproductive success [2]. Mate choice is also tightly related to efficiency of mate search; actively searching individuals may locate many more potential mates than passive ones in a given time interval, and thus secure population survival at much lower numbers or densities [1]. Finally, intuition suggests that the lower the divorce rate of an individual, the more carefully it should choose these partners in order to secure that its genes pass to the future generations. Needless to say, these processes have certainly evolved together and strongly shaped the currently observed mating systems. 1

Department of Theoretical Biology, Institute of Entomology, Academy of Sciences of the Czech Republic, and Faculty of Biological Sciences, University of South Bohemia, ˇ Braniˇsovsk´ a 31, 37005 Cesk´ e Budˇejovice, Czech Republic (e-mail: [email protected]). 2 Department of Theoretical Biology, Institute of Entomology, Academy of Sciences of the Czech Republic, and Faculty of Biological Sciences, University of South Bohemia, ˇ Braniˇsovsk´ a 31, 37005 Cesk´ e Budˇejovice, Czech Republic (e-mail: [email protected]).

01-Ber-a

Behaviour-mediated population dynamics

AICME II abstracts

We examine how the process of mate search, degree of mate choice and degree of mate fidelity may interact to affect long-term population dynamics in a sexually reproducing species. In particular, we address the following questions: Is degree of mate choice limited by or limiting for degree of mate fidelity? How does mate search shape this relationship? How do other life history details affect mating behaviour? We develop a spatially explicit, individual-based model of a sexually reproducing population with single (i.e. unpaired) males, single females, and pairs as focal individuals. Both this model and its non-spatial approximation give rise to the Allee effect due to lack of mating possibilities, and sufficiently small/sparse populations always go extinct. We quantify combinations of divorce rate and mate choice under which populations survive or go extinct for high initial sizes. We thus show that there exist ecological constraints for possible (co)evolution of mate choice and pair maintenance behaviour. Our models also suggest that colonial species with active mate search may allow for higher divorce rates to survive than less colonial animals that search for their mates randomly, and that short-lived species should be either less promiscuous or less choosy when accepting mates to equate population-dynamic performance of long-lived ones.

References [1] L. Berec, D. S. Boukal & M. Berec, 2001, Linking the Allee effect, sexual reproduction and temperature-dependent sex determination via spatial dynamics, American Naturalist, 157, 217–230. [2] S. Choudhury, 1995, Divorce in birds: a review of the hypotheses, Animal Behaviour , 50, 413–429. [3] F. Dubois, F. C´ezilly & M. Pagel, 1998, Mate fidelity and coloniality in waterbirds: a comparative analysis, Oecologia, 116, 433–440. [4] A. P. Møller & S. Legendre, 2001, Allee effect, sexual selection and demographic stochasticity, Oikos 92, 27–34.

01-Ber-b