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We tend to think that sexual reproduction is a harmonious process in which males and females cooperate in order to increase the number of their descendants. Nevertheless, this is not always the case. During the reproductive process both males and females may have different reproductive interests; for instance, in some cases males may desert their offspring in order to mate again. This behaviour can be seen as disadvantageous for these males, since it may reduce the probability of survival of its offspring. However, these “disadvantageous” behaviours may be passed on from parents to offspring. The disparity in the reproductive interests between the sexes was formally termed “sexual conflict” by Geoff Parker in 1979.
Deserting the offspring may be advantageous for the deserting parent, but it usually is disadvantageous for the parent left providing all the care. The deserting parent will have more time to find a new partner, which will increase his/her reproductive success. The parent left providing all the care will have to spend a considerable amount of energy, as he/she will have to provide the care of both parents and will not have time to re-mate until the offspring are mature enough. In the long term, both males and females will not agree on the number of copulations or partners. This, in turn, will shape the mating system (or systems) exhibited by a given species.
The studies that have investigated the selective forces that shape a given mating system lay on the grounds of evolutionary- biology and ecology. Several theories have been proposed to explain the occurrence of a given mating system, and these are still at the core of the interests of modern evolutionary biology.
As of today, a multidisciplinary team of researchers from several universities have been gathered in order to investigate and provide answers to the evolution and variation in the mating systems of certain groups of animals (birds and insects). The team is formed by Medardo Cruz López, Martín A. Serrano-Meneses (both from the Universidad Autónoma de Tlaxcala, Mexico), Raúl Cueva (Universidad Nacional Autónoma de México, Mexico), Tamás Székely (University of Bath, UK) and Clemens Küpper (University of Harvard, USA).
Medardo Cruz López is currently an MSc. student in the Biological Sciences program, at the Centro Tlaxcala de Biología de la Conducta (Universidad Autónoma de Tlaxcala), under the supervision of Martín A. Serrano-Meneses. The model Medardo is using to investigate the selective forces that shape mating systems is the Snowy plover (Charadrius nivosus), a small shorebird that may exhibit up to three mating systems within a single population! Monogamous breeding couples remain together over a reproductive season and both provide parental care. Under polygyny, males have more than one partner and they leave females to provide all the care to the chicks. Finally, under polyandry, females have more than one partner and they leave males to provide all the care to the chicks.
Five years ago (2006-2010) we started working on a Snowy plover population located at the Bahía de Ceuta, Sinaloa, Mexico. Every reproductive season, from 2006, Medardo and Clemens work at Ceuta and gather data on the characteristics of breeding individuals, the number of chicks they produce, how many of these survive, what parent provides most of the care, how much care the parent provides, among other data. Medardo and Clemens also obtain morphological data, such as tarsus size, wing size, body weight and photographs of the ornaments of every individual. Up to 95% of the individuals of this population have been ringed; therefore it has been possible to track the life histories of most individuals and to accurately manage data. With our datasets we aim to generate a number of research studies and to investigate in depth the traits that determine the mating systems adopted by this species.
