In Hot Pursuit: Fluctuating Mating System and Sexual Selection in Sand Lizards

Abstract

A changing climate is expected to have profound effects on many aspects of ectotherm biology. We report on a decade-long study of free-ranging sand lizards (Lacerta agilis), exposed to an increasing mean mating season temperature and with known operational sex ratios. We assessed year-to-year variation in sexual selection on body size and postcopulatory sperm competition and cryptic female choice. Higher temperature was not linked to strength of sexual selection on body mass, but operational sex ratio (more males) did increase the strength of sexual selection on body size. Elevated temperature increased mating rate and number of sires per clutch with positive effects on offspring fitness. In years when the "quality" of a female's partners was more variable (in standard errors of a male sexual ornament), clutches showed less multiple paternity. This agrees with prior laboratory trials in which females exercised stronger cryptic female choice when male quality varied more. An increased number of sires contributing to within-clutch paternity decreased the risk of having malformed offspring. Ultimately, such variation may contribute to highly dynamic and shifting selection mosaics in the wild, with potential implications for the evolutionary ecology of mating systems and population responses to rapidly changing environmental conditions. K E Y W O R D S : Climate change, mating system, multiple paternity, operational sex ratio, temperature.

Effects of night-time warming on temperate ectotherm reproduction: potential fitness benefits of climate change for side-blotched lizards

“…However, the present study is one of the first to verify experimentally the responses of temperate ectotherms to ongoing climate change (see also Chamaillé-Jammes et al, 2006;Huey et al, 2009;Olsson et al, 2010), and to test the effects of asymmetric changes to diurnal temperature range. Based on our results, we conclude that these effects are primarily beneficial for this population of northern lizards, and predict that future changes will continue to benefit the reproduction, growth and survival of individuals at this site.…”

“…A positive relationship between warmer incubation temperatures and hatchling size has been observed in multiple other lizard species, including both oviparous and viviparous species (Shine, 2004;Shine and Harlow, 1993;Wapstra, 2000;Dubey and Shine, 2011). In general, the effects of climate warming are predicted to increase fitness in temperate ectotherms because of the limitations imposed by current environmental temperatures in seasonal environments (Bradshaw et al, 2004;Deutsch et al, 2008;Huey et al, 2009) (see also Olsson et al, 2010). Thus, we hypothesize that asymmetric warming during the breeding season will increase the fitness of temperate ectotherms by advancing the timing of reproduction, increasing the rate of embryonic development and producing larger hatchlings with a subsequent survival advantage.…”

Environment-Dependent Sexual Selection: Bateman’s Parameters under Varying Levels of Food Availability

“…Over the last decade there has been growing evidence that the strength of sexual selection varies in space and time. This is mainly supported by studies demonstrating fluctuating selection gradients of sexually selected traits over several reproductive events, such as those documented for birds (Chaine and Lyon 2008;Robinson et al 2012), reptiles (Olsson et al 2011), and fish (Wacker et al 2014). Another line of empirical evidence for among-and withinspecies variation of the strength of sexual selection comes from studies using metrics derived from Bateman's three principles (Bateman 1948), including the variance in reproductive success (opportunity for selection), the variance in mating success (opportunity for sexual selection), and the slope of an ordinary least squares regression of reproductive success on mating success (Bateman gradient;Arnold 1994;Jones 2009).…”

Faithful or not: direct and indirect effects of climate on extra-pair paternities in a population of Alpine marmots

“…Indeed, females generally engage in extrapair copulations to obtain genetic benefits for their offspring and, as a consequence, improve their fitness [61]. In sand lizards, the mean number of fathers per clutch is higher in warmer years [14], and offspring from multiple sired clutches present less malformations and show enhanced first year survival [14,62]. By constraining EPP opportunities at the annual level, climate conditions are likely to shape the genetic characteristics of the population and its annual variability through both changes in female mate choice and effective population size and could have profound implications on the direction and strength of sexual selection.…”