Rebouças Raoni, da Silva Hélio Ricardo, Solé Mirco
Programa de Pós-Graduação em Ciências Biológicas-Biologia Animal, Universidade Federal do Espírito Santo. Avenida Fernando Ferrari, Vitória, Espírito Santo, Brazil.
Laboratório de Herpetologia, Universidade Federal Rural do Rio de Janeiro. Caixa Postal, Seropédica-Rio de Janeiro, Brazil.
PLoS One. 2018 Jan 11;13(1):e0190153. doi: 10.1371/journal.pone.0190153. eCollection 2018.
Island Rule postulated that individuals on islands tend to dwarfism when individuals from mainland populations are large and to gigantism when mainland populations present small individuals. There has been much discussion about this rule, but only few studies were carried out aiming to reveal this pattern for anurans. Our study focused on measuring the size of individuals on islands and to find a possible pattern of size modification for insular anurans. Individuals were collected on continental islands, measured and compared to mainland populations. We selected four species with different natural history aspects during these analyses. Island parameters were compared to size of individuals in order to find an explanation to size modification. Three of the four species presented size shifting on islands. Ololygon trapicheiroi and Adenomera marmorata showed dwarfism, Boana albomarginata showed gigantism and in Thoropa miliaris there was no evident size modification. Allometric analysis also revealed differential modification, which might be a result of different selective pressures on islands in respect of mainland populations. Regression model explained most of the size modification in B. albomarginata, but not for the other species. Our results indicate that previous assumptions, usually proposed for mammals from older islands, do not fit to the anurans studied here. We support the assumption that size modification on islands are population-specific. Hence, in B. albomarginata some factor associated to competition, living area and isolation time might likely be responsible for gigantism on islands.
岛屿法则假定，当来自大陆种群的个体体型较大时，岛屿上的个体往往会出现侏儒化；而当大陆种群的个体体型较小时，岛屿上的个体则会出现巨型化。关于这一法则已经有很多讨论，但针对两栖动物揭示这种模式的研究却很少。我们的研究重点是测量岛屿上个体的大小，并寻找岛屿两栖动物大小变化的可能模式。在大陆岛屿上收集个体，进行测量并与大陆种群进行比较。在这些分析过程中，我们选择了四个具有不同自然历史特征的物种。将岛屿参数与个体大小进行比较，以便找到大小变化的解释。四个物种中有三个在岛屿上出现了大小变化。特拉皮切罗伊姬蛙和大理石短头蟾表现出侏儒化，白边雨蛙表现出巨型化，而粒疣角蟾没有明显的大小变化。异速生长分析也揭示了差异变化，这可能是岛屿上相对于大陆种群存在不同选择压力的结果。回归模型解释了白边雨蛙大部分的大小变化，但对其他物种不适用。我们的结果表明，通常针对古老岛屿上的哺乳动物提出的先前假设并不适用于这里所研究的两栖动物。我们支持岛屿上大小变化具有种群特异性的假设。因此，在白边雨蛙中，一些与竞争、生存区域和隔离时间相关的因素可能是导致其在岛屿上出现巨型化的原因。
