Pearson David, Shine Richard, Williams Andrew
Department of Conservation and Land Management, PO Box 51, Wanneroo, WA, 6065, Australia.
School of Biological Sciences A08, University of Sydney, NSW 2006, Australia.
Oecologia. 2002 May;131(3):418-426. doi: 10.1007/s00442-002-0917-5. Epub 2002 May 1.
Unusually among reptiles, Australian carpet pythons (Morelia spilota) display substantial geographic variation in mating systems and sexual size dimorphism. We studied a population of the south-western subspecies (M. s. imbricata) of this widely distributed taxon, on Garden Island near Perth, Western Australia. Our data greatly expand the range of variation previously documented for populations of this species. Unlike eastern Australian populations where sex differences in mean adult body size are relatively minor [<10% in snout-vent length (SVL), <30% in mass], female M. s. imbricata grow to over twice the length and more than 10 times the mass of adult males. Mean adult size averages 104 cm SVL (305 g) for males versus 214 cm SVL (3.9 kg) for females. This sex difference is a consequence of cessation in growth by males, in turn due to a reduced rate of feeding. Males display low feeding rates even in captivity, suggesting that their "dwarf" sizes reflect genetic control rather than local prey availability. Observations of free-ranging snakes suggest that males do not engage in overt agonistic interactions during the mating season, and that larger body size does not enhance male mating success. These results fit well with previous interpretations of the relationship between mating systems and sexual size dimorphism in snakes, including other populations of carpet pythons. M.s. spilota displays the greatest geographic variation in sexual size dimorphism yet recorded for any vertebrate species.
与其他爬行动物不同的是，澳大利亚地毯蟒（Morelia spilota）在交配系统和两性体型差异方面表现出显著的地理变异。我们研究了这个广泛分布的分类单元的西南亚种（M. s. imbricata）在西澳大利亚珀斯附近花园岛上的一个种群。我们的数据极大地扩展了该物种种群先前记录的变异范围。与澳大利亚东部种群不同，东部种群成年个体平均体型的性别差异相对较小[吻肛长度（SVL）<10%，体重<30%]，而M. s. imbricata雌性个体的体长超过成年雄性个体的两倍，体重超过10倍以上。成年雄性个体平均SVL为104厘米（305克），而成年雌性个体平均SVL为214厘米（3.9千克）。这种性别差异是雄性个体生长停止的结果，而生长停止又是由于摄食率降低所致。即使在圈养环境中，雄性个体的摄食率也很低，这表明它们的“矮小”体型反映的是基因控制，而非当地猎物的可获得性。对自由放养蛇类的观察表明，雄性个体在交配季节不进行明显的争斗互动，而且体型较大并不能提高雄性个体的交配成功率。这些结果与之前对蛇类交配系统和两性体型差异之间关系的解释非常吻合，包括地毯蟒的其他种群。M.s. spilota在两性体型差异方面表现出有记录以来任何脊椎动物物种中最大的地理变异。
