A matter of time! : time dependent mating decisions in the common lizard, zootoca vivipara

Abstract

Life-history theory predicts that reproductive traits and behavioral strategies displayed by an organism should vary strategically with respect to the intrinsic and extrinsic conditions it is exposed to. Condition-dependent strategies may allow an individual to enhance its reproductive success, a crucial component of Darwinian fitness. Such strategies are predicted to vary with mate availability and the time of mate encounter, which may determine Darwinian fitness, especially in species where reproduction is restricted to annually defined seasons. Moreover, an individual’s intrinsic conditions (e.g., its reproductive stage) at the time of encounter, may determine its mating propensity. It may thus be beneficial to adjust mating decisions, including mate acceptance thresholds and the amount of resources invested into an accepted mate, in response to when mates are encountered.

Studies that determine how the timing of mate encounter affects individual mating decisions are currently scarce. In this thesis we experimentally investigate whether and how mating decisions are affected by the time of mate encounter, and determine the consequences of potential strategies on reproductive success, using the common lizard, Zootoca vivipara, as a model species. Effects of the time of mate encounter on mating propensity, the degree of mate choice expressed, investment during mating, and the production of multiple seasonal broods are demonstrated. The results point to strategic, time dependent, mating decisions, which can importantly affect an individual’s reproductive success. Moreover, they provide evidence that the detected mating decisions may mitigate predicted negative effects of reduced mate encounter on reproduction and, ultimately, on population viability.

The findings demonstrate that time dependent strategies may allow individuals to increase reproductive success and they might be more important in low-density populations. Processes such as habitat fragmentation and climate change affect population density, and thus can have negative effects on reproductive success and population viability. Moreover, temporal variation in mate availability exists in a wide range of species. Therefore, the results presented in this thesis may contribute to improving predictions of how species may respond to changes in population demography and climate change, and could provide crucial insight for conservation efforts.