High food abundance permits the evolution of placentotrophy: evidence from a placental lizard, Pseudemoia entrecasteauxii

Mechanisms of reproductive allocation are major determinants of fitness because embryos cannot complete development without receiving sufficient nutrition from their parents. The nourishment of offspring via placentae (placentotrophy) has evolved repeatedly in vertebrates, including multiple times in squamate reptiles (lizards and snakes). Placentotrophy has been suggested to evolve only if food is sufficiently abundant throughout gestation to allow successful embryogenesis. If scarcity of food prevents successful embryogenesis, females should recoup nutrients allocated to embryos via abortion, reabsorption, and/or cannibalism. We tested these hypotheses in the placentotrophic Southern Grass Skink, Pseudemoia entrecasteauxii. We fed females one of four diets (high constant, high variable, low constant, and low variable) during gestation, and tested the effects of both food amount and schedule of feeding on developmental success, cannibalism rate, placental nutrient transport, offspr...

繁殖分配机制是决定生物适合度的关键因素，因为胚胎若无法从亲本处获得充足营养，便无法完成发育。通过胎盘为子代提供营养的胎盘营养（placentotrophy）策略，在脊椎动物中已多次独立演化，有鳞目爬行动物（蜥蜴与蛇类）便曾多次演化出该策略。此前研究认为，仅当妊娠期内食物资源足够充足，可支持胚胎成功发育时，胎盘营养策略才会演化；若食物匮乏导致胚胎无法顺利发育，雌性个体可通过流产、胚胎重吸收或同类相食的方式，回收原本分配给胚胎的营养物质。我们以胎盘营养型物种南方草石龙子（Pseudemoia entrecasteauxii）为研究对象，对上述假说进行了验证。本研究在妊娠期为雌性个体提供四种日粮处理：高恒定日粮、高波动日粮、低恒定日粮与低波动日粮，并检验了食物总量与饲喂节律对胚胎发育成功率、同类相食率、胎盘营养转运以及子代（原文未完整收尾）的影响。