Is the Evolution of Viviparity Accompanied by a Relative Increase in Maternal Abdomen Size in Lizards?

Abstract

Female reptiles with viviparous reproduction should leave space for their eggs that reach the maximum mass and volume in the oviducts. Is the evolution of viviparity accompanied by a relative increase in maternal abdomen size, thus allowing viviparous females to increase the amount of space for eggs? To answer this question, we compared morphology and reproductive output between oviparous and viviparous species using three pairs of lizards, which included two Eremias, two Eutropis and two Phrynocephalus species with different reproductive modes. The two lizards in each pair differed morphologically, but were similar in the patterns of sexual dimorphism in abdomen and head sizes and the rates at which reproductive output increased with maternal body and abdomen sizes. Postpartum females were heavier in viviparous species, suggesting that the strategy adopted by females to allocate energy towards competing demands differs between oviparous and viviparous species. Reproductive output was increased in one viviparous species, but decreased in the other two, as compared with congeneric oviparous species. The space requirement for eggs did not differ between oviparous and viviparous females in one species pair, but was greater in viviparous females in the other two pairs greater in relative clutch mass and relative litter mass. In the two Phrynocephalus species, viviparous females produced heavier clutches than did oviparous females not by increasing the relative size of the abdomen, but by being more full of eggs. In none of the three species pairs was the maternal abdomen size greater in the viviparous species after accounting for body size. Our data show that the evolution of viviparity is not accompanied by a relative increase in maternal abdomen size in lizards. Future work could usefully investigate other lineages of lizards to determine whether our results are generalisable to all lizards.

Variation of Reproductive Traits and Female Body Size in the Most Widely-Ranging Terrestrial Reptile: Testing the Effects of Reproductive Mode, Lineage, and Climate

“…Although this pattern of offspring size variation is in line with the ‘volume constraint hypothesis’ (Prediction 1a), this pattern was not common in previous studies. It was reported in none of the other two reproductively bimodal lizard species (Qualls and Shine 1995; Smith and Shine 1997) and in only two of the 7 lizard and snake genera in which oviparous and viviparous species were compared (Guillette 1982; Shine 1987; Medina and Ibargüengoytía 2010; Sun et al 2012; Yang et al 2012). …”

“…Maternal size, climate, and ancestry (phylogenetic history) were identified as important predictors of variation in reptilian reproductive traits across related species and/or within species (e.g., Bauwens and Díaz-Uriarte 1997; Brandt and Navas 2011; Díaz et al 2012). Theory and some empirical studies (e.g., Qualls and Shine 1995; Sun et al 2012) suggest that reproductive mode (egg-laying vs. live-bearing) can also influence life-history traits in reptiles.…”

“…progressive retention of eggs in utero throughout embryogenesis) offers an opportunity to test several predictions of life-history theory, in particular the hypothesis that female reproductive output is constrained by abdomen volume (Qualls and Shine 1995; Du et al 2005). At later stages of the embryo development, the eggs increase substantially in their mass and volume due primarily to the uptake of water (Guillette 1982; Qualls and Shine 1995; Sun et al 2012; and references therein). In typical oviparous species, this swelling occurs after oviposition and does not burden the female.…”

“…These predicted responses do not exclude one another, but each of them may have fitness costs. Only few studies compared life-history traits in conspecific populations (Qualls and Shine 1995; Smith and Shine 1997; Lindtke et al 2010) or related species (Guillette 1982; Shine 1987; Medina and Ibargüengoytía 2010; Sun et al 2012; Yang et al 2012) which differ in reproductive mode. Their results showed no clearly consistent pattern.…”

Age‐related reproduction of female Mongolian racerunners (Eremias argus; Lacertidae): Evidence of reproductive senescence

“…From these findings, we conclude that the reproductive maturation hypothesis applies not only to clutch size but also to clutch mass in E. argus. The explanation for why clutch size and clutch mass were greater in larger/older females at least partly lies in that, as in other lizards (Bleu, Massot, Haussy, & Meylan, 2012;Du, 2006;Finkel & Holbrook, 2000;Goodman, Hudson, Isaac, & Schwarzkopf, 2009;Olsson, Shine, Wapstra, Ujvari, & Madsen, 2002;Shine, 1992;Vitt & Congdon, 1978), the amount of abdominal space available to hold the clutch and/or the ability to acquire energy for reproduction is greater in larger/older females of E. argus (Luo et al, 2010;Sun et al, 2012;Sun et al, 2013).…”