Rapid growth reduces cold resistance: evidence from latitudinal variation in growth rate, cold resistance and stress proteins

Background

Physiological costs of rapid growth may contribute to the observation thatorganisms typically grow at submaximal rates. Although, it has beenhypothesized that faster growing individuals would do worse in dealing withsuboptimal temperatures, this type of cost has never been exploredempirically. Furthermore, the mechanistic basis of the physiological costsof rapid growth is largely unexplored.

Methodology/Principal Finding

Larvae of the damselfly Ischnura elegans from two univoltinenorthern and two multivoltine southern populations were reared at threetemperatures and after emergence given a cold shock. Cold resistance,measured by chill coma recovery times in the adult stage, was lower in thesouthern populations. The faster larval growth rates in the southernpopulations contributed to this latitudinal pattern in cold resistance. Inaccordance with their assumed role in cold resistance, Hsp70 levels werelower in the southern populations, and faster growing larvae had lower Hsp70levels. Yet, individual variation in Hsp70 levels did not explain variationin cold resistance.

Conclusions/Significance

We provide evidence for a novel cost of rapid growth: reduced coldresistance. Our results indicate that the reduced cold resistance insouthern populations of animals that change voltinism along the latitudinalgradient may not entirely be explained by thermal selection perse but also by the costs of time constraint-induced highergrowth rates. This also illustrates that stressors imposed in the larvalstage may carry over and shape fitness in the adult stage and highlights theimportance of physiological costs in the evolution of life-histories atmacro-scales.