Data from: Lizards on newly created islands independently and rapidly adapt in morphology and diet

Rapid adaptive changes can result from the drastic alterations humans impose on ecosystems. For example, flooding large areas for hydroelectric dams converts mountaintops into islands and leaves surviving populations in a new environment. We report differences in morphology and diet of the termite-eating gecko Gymnodactylus amarali between five such newly created islands and five nearby mainland sites located in the Brazilian Cerrado, a biodiversity hotspot. Mean prey size and dietary prey-size breadth were larger on islands than mainlands, expected because four larger lizard species that also consume termites, but presumably prefer larger prey, went extinct on the islands. In addition, island populations had larger heads relative to their body length than mainland populations; larger heads are more suited to the larger prey taken, and disproportionately larger heads allow that functional advantage without an increase in energetic requirements resulting from larger body size. Parallel morphological evolution is strongly suggested, because there are indications that, before flooding, relative head size did not differ between future island and future mainland sites. Females and males showed the same trend of relatively larger heads on islands, so the difference between island and mainland sites is unlikely to be due to greater male–male competition for mates on islands. We thus discovered a very fast (at most 15 y) case of independent parallel adaptive change in response to catastrophic human disturbance.

人类对生态系统施加的剧烈扰动，可引发快速的适应性演化。例如，为修建水电站大坝而淹没大片区域，会将山顶改造为孤岛，使残存种群置身于全新的环境之中。本研究报道了巴西塞拉多（Brazilian Cerrado，全球生物多样性热点地区）内5座此类人工新形成岛屿，与周边5处大陆样地之间，食白蚁壁虎（Gymnodactylus amarali）的形态学与饮食特征差异。岛屿样地的平均猎物体型与猎物体型食性广度均大于大陆样地，这一结果符合预期：另有4种同样捕食白蚁的大型蜥蜴物种已在岛屿上灭绝，而这些物种大概率偏好更大体型的猎物。此外，相较于大陆种群，岛屿种群的头部相对于体长的比例更大；更大的头部更适配所捕食的大型猎物，且头部比例的超常增大，可在不增加因体型增大带来的能量需求的前提下，获得这一功能优势。研究强烈提示存在平行形态演化：有证据表明，在淹没发生前，未来将成为岛屿的样地与未来的大陆样地之间，头部相对体型的比例并无差异。雌性与雄性个体均表现出岛屿种群头部比例更大的相同趋势，因此岛屿与大陆样地间的差异，不太可能由岛屿上更为激烈的雄性配偶竞争所致。综上，本研究发现了一个极为快速（至多15年）的、响应人类灾难性扰动的独立平行适应性演化案例。