MAINTENANCE OF AN ALTERNATIVE REPRODUCTIVE STRATEGY IN THE SWORDTAIL Xiphophorus multilineatus A) Intellectual Merit - Individuals of the same sex and same species are expected to solve the problems of surviving and reproducing in a similar way. However, males of the same species can not only look very different, but have very different strategies for surviving and reproducing. These differences are known as alternative reproductive strategies". The main objective of this project is to examine the maintenance of the intriguing diversity of behaviors and morphologies found within individuals of the same sex. Three mechanisms are commonly proposed to maintain alternative reproductive strategies: negative frequency-dependent selection, variation in ecological factors, and variation in female preference for different types of males between subpopulations. This study will test the relative importance of these different mechanisms and their interactions in the swordtail fish Xiphophorus multilineatus. This species represents a unique system in which to examine the mechanisms maintaining alternative reproductive strategies since the genetic basis for the alternative reproductive strategies in this species are known, and it is possible to know a male's genetic makeup by examining his size and pigment patterns. This project will determine if the alternative reproductive strategies in X. multilineatus are maintained by negative frequency dependent-selection by examining the relative fertilization success of the two strategies (sneakers that mature early and sneak copulations and flashers that mature late and court females) under different relative frequencies in controlled laboratory experiments. This project will determine how variation in predation (high predation selects for small males in some places while low predation selects for large males in others) and variation in female preference (some populations have strong female preferences for large males, others do not) across natural subpopulations influences the fertilization success of the two types of males. Finally, the degree of gene flow between the subpopulations will be studied using molecular techniques, as it is important to know if these populations are exchanging genes to determine whether the differences in predation and/or female preferences across subpopulations could be acting to maintain the alternative reproductive strategies at the global population level. B) Broader Impact - The broader impacts resulting from this project will include the training of one postdoctoral fellow (Co-PI), one graduate student and several undergraduate students at Ohio University. In addition, this research will establish a long-term collaboration designed to study fish populations in the field (in Mexico, once the Co-PI returns to his country) and in the lab (in Ohio University), ultimately stimulating the development of evolutionary studies in the country of origin.
