Abstract
Food availability significantly affects an animal's energy metabolism, and thus its phenotype, survival, and reproduction. Maternal and offspring responses to food conditions are critical for understanding population dynamics and life-history evolution of a species. In this study, we conducted food manipulation experiments in field enclosures to identify the effect of food restriction on female reproductive traits and postpartum body condition, as well as on hatchling phenotypes, in a lacertid viviparous lizard from the Inner Mongolian desert steppe of China. Females under low-food availability treatment (LFT) had poorer immune function and body condition compared with those under high-food availability treatment (HFT). The food availability treatments significantly affected the litter size and litter mass of the females, but not their gestation period in captivity or brood success, or the body size, sprint speed, and sex ratio of the neonates. Females from the LFT group had smaller litter sizes and, therefore, lower litter mass than those from the HFT group. These results suggest that female racerunners facing food restriction lay fewer offspring with unchanged body size and locomotor performance, and incur a cost in the form of poor postpartum body condition and immune function. The flexibility of maternal responses to variable food availability represents an important life strategy that could enhance the resistance of lizards to unpredictable environmental change.
Highlights
In nature, the food available to an animal exhibits spatiotemporal variation, significantly affecting its energy metabolism and its phenotype, survival, and reproduction (Acheampong et al, 2011; Douhard et al, 2014; Du, 2006; Hoy et al, 2016)
We aimed to address the following questions: (1) How does female reproductive investment respond to food restriction? (2) Does food restriction affect postpartum body condition of females? (3) How does maternal food restriction influence neonate phenotypes?
The postpartum body conditions were worse for females in the low-food availability treatment (LFT) group than for those in the high-food availability treatment (HFT) group (F1,24=7.928, P=0.010) (Figure 1A), initial body condition did not differ between the two food treatment groups (F1,24=1.162, P=0.292)
Summary
The food available to an animal exhibits spatiotemporal variation, significantly affecting its energy metabolism and its phenotype, survival, and reproduction (Acheampong et al, 2011; Douhard et al, 2014; Du, 2006; Hoy et al, 2016). Food availability affects maternal fitnessrelated traits (e.g. body size, growth, and reproduction), but might induce phenotypic variations in offspring (Ballinger & Congdon, 1980; Hillesheim & Stearns, 1991; Jones et al, 2015; Vaissi & Sharifi, 2016). A mother has to decide on energy allocation for multiple tasks, such as maintenance, growth, and reproduction, leading to important life-history tradeoffs (e.g., maintenance vs reproduction) (Hegemann et al, 2013; Rollinson & Rowe, 2016); for instance, the tropical house wren (Troglodytes aedon) decreases parental reproductive investment (i.e. nestling feeding frequency), but does not alter self-maintenance (metabolic rate and body condition) when the cost of activity increases during reproduction (Tieleman et al, 2008). The “optimal egg size theory” assumes that one optimal egg size is appropriate under certain
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