Income breeding and temperature-induced plasticity in reproductive traits in lizards

Abstract

SUMMARYWe used the northern grass lizard Takydromus septentrionalis as a model animal to examine the energy allocation strategy and whether body temperature can affect maternal reproductive traits in lizards. We maintained adult females collected from the field soon after winter dormancy under three thermal conditions (24.0±1.0°C, 28.0±1.0°C and 32.0±1.0°C) throughout the subsequent reproductive season, and then recorded their energy intake, digestive efficiency, body size and mass changes, and reproductive parameters. Manipulation of body temperature in reproducing females affected energy intake and several maternal reproductive characteristics. Females allocated energy to reproduction following the fulfillment of energetic requirements for metabolism and growth. The reduced energy availability for reproduction constrained females at low or high body temperatures to produce fewer and smaller eggs per season but had no role in influencing the number of eggs produced in single reproductive bouts. Females used currently acquired energy to fuel reproduction, and this strategy did not shift seasonally from the first to subsequent clutches. Our study supports the idea that the use of currently acquired energy for reproduction may be more widespread in ectotherms than thought before, and shows for the first time that egg size is thermally plastic in T. septentrionalis, where eggs produced in single reproductive bouts are believed to be well optimized for size.

Neither male gonadal androgens nor female reproductive costs drive development of sexual size dimorphism in lizards

“…a higher priority for energy allocation towards growth and maintenance rather than to reproduction (Luo et al, 2010). Additionally, the described results in P. picta males do not support the hypothesis that final structural size in reptiles is determined by energy availability for growth.…”

Thermal dependence of reproductive allocation in a tropical lizard

“…Among lizards, a similar pattern was reported in comparative studies of the genus Sceloporus (Angilletta et al, 2006). By contrast, grass lizards (Takydromus septentrionalis) produced the largest eggs at an intermediate temperature (Luo et al, 2010). This result might reflect differences between the life-histories of the grass lizard and the Madagascar ground gecko.…”

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

“…While this might indicate a difference in maternal investment, as there was no difference in RCM between experimental and control groups (Table1), we interpret these results as merely differences in allocation strategy (i.e. egg size versus number) possibly induced by experimental conditions (but see Luo et al, 2010). Another explanation for this result is that some factor, such as water content and hence egg mass, differed, but not maternal investment in yolk.…”

“…Thus, higher temperatures, even if they only occur at night, are capable of causing an increase in annual reproductive output independent of growing season length. Although other studies have reported decreases in reproductive output above optimal temperatures due to physiologic stress (Luo et al, 2010), asymmetric climate warming could increase mean environmental temperatures without surpassing a species' thermal maximum as temperatures in the lower portion of the distribution rise disproportionately. Our data suggest that this would allow for an overall increase in clutch frequency and possibly subsequent survival among temperate ectotherms, a pattern reported previously (Bradshaw et al, 2004).…”