Experimental litter size reduction reveals costs of gestation and delayed effects on offspring in a viviparous lizard

Abstract

Experimental studies have often been employed to study costs of reproduction, but rarely to study costs of gestation. Disentangling the relative importance of each stage of the reproductive cycle should help to assess the costs and benefits of different reproductive strategies. To that end, we experimentally reduced litter size during gestation in a viviparous lizard. We measured physiological and behavioural parameters during gestation and shortly after parturition, as well as survival and growth of females and their offspring. This study showed four major results. First, the experimental litter size reduction did not significantly affect the cellular immune response, the metabolism and the survival of adult females. Second, females with reduced litter size decreased their basking time. Third, these females also had an increased postpartum body condition. As postpartum body condition is positively related to future reproduction, this result indicates a gestation cost. Fourth, even though offspring from experimentally reduced litters had similar weight and size at birth as other offspring, their growth rate after birth was significantly increased. This shows the existence of a maternal effect during gestation with delayed consequences. This experimental study demonstrates that there are some costs to gestation, but it also suggests that some classical trade-offs associated with reproduction may not be explained by gestation costs.

Influence of reproductive mode on metabolic costs of reproduction: insight from the bimodal lizard Zootoca vivipara

“…Clarifying the energy implications of reproductive mode is a vital component in understanding selective pressures behind the evolution of viviparity (Shine and Schwarzkopf, 1992;Qualls and Shine, 1998;Bleu et al, 2012). Herein, we used the reproductively bimodal lizard Z. vivipara to compare the metabolic costs of reproduction between oviparous and viviparous individuals.…”

Parental experience of a risky environment leads to improved offspring growth rate

“…Investment in current reproduction such as production of a heavier litter must incur a cost for females, otherwise mothers from the control group would have produced large offspring as well. Production of larger pups can sometimes lead to a reduction in future fecundity or survival of mothers (Oksanen et al, 2002;Bleu et al, 2012). Overall, we suggest that our results can be interpreted as an adaptive parental strategy, preparing offspring for a pathogen-rich environment by influencing their growth and size.…”

Selection for increased maternal body volume does not differ between two Scincella lizards with different reproductive modes

“…Reproductive output is lower in S. reevesii than in S. modesta, but selection for increased maternal body volume does not differ between the two lizards with different reproductive modes. The reasons why female S. reevesii do not compensate for their lower reproductive output by increasing overall body size, or by increasing relative abdomen size, are currently unknown, but gestation costs such as increased metabolism (Angilletta and Sears, 2000), decreased locomotor capacity (Miles et al, 2000), impaired immune function (Ilmonen et al, 2003), reduced growth (Cox et al, 2010) and decreased postpartum body condition (Bleu et al, 2011) cannot be precluded as an important factor. Future work should investigate whether an adaptive reduction of reproductive output will enhance fitness in viviparous females.…”