Variation in life history traits: temperature as modulator of parental investment along an altitudinal gradient

PAOLA L. SASSI; JOSEFINA MENÉNDEZ; FERNANDA CUEVAS

Iguazú

Congreso; VI Reunión Binacional de Ecología; 2016

Asociación Argentina de Ecología- Sociedad de Ecología de Chile

Variation in life history traits, shaped by intrinsic and extrinsic factors, gives place to alternative strategies. Temperature is a powerful driver of the eventual variation in parental investment. Keeping an adequate energy balance implies behavioral and physiological adjustments to the thermal environment, especially during reproductive events. Furthermore, ambient temperature affects the availability of energy and nutrients in the environment. Thus, spatial-temporal climate variations directly impact the allocation of resources to reproduction and consequently the fitness of organisms. Diverse hypotheses explain the way in which temperature will affect animals? investment in reproduction. Classical views assume central and external limits to energy acquisition. Hence, relatively poor scenarios in terms of food availability or highly demanding cold conditions entail trade-offs to parental investment. Nevertheless, it has been recently proposed that endotherms face limits to energy use due to the amount of heat generated in metabolic processes. Since heat dissipation depends on the temperature differential between the body and the environment, a low ambient temperature would enable endotherms to undergo higher metabolic costs than a warmer one, for instance by investing resources in reproduction. Our research addresses the study of reproductive parameters in Phyllotis xanthopygus, a rodent species broadly distributed in the Central Andes. Across an elevation gradient between 1700 and 3100 m asl, we report that litter size is comparatively greater in pregnant females collected at higher elevations. To explore the role that ambient temperature could perform on this pattern, we breed individuals in the laboratory under two thermal treatments. With no changes in the litter size, the pups? weight was greater at lower temperature, in agreement with predictions of increased lactation. Although this result does not replicate that of the altitude pattern, it is consistent with a reproductive investment possibly favored under low ambient temperatures at high elevation. It remains to inquire whether the number of reproductive events per female varies across sites linked to seasonality, which could compensate differences in litter size. Our findings are congruent with an evolutionary history at high altitude and cold environments, and suggest possible challenges for the species to cope with the current global warming.