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改变，可催生快速的适应性变化。例如，为修建水电大坝（hydroelectric dams）而淹没大片区域，会将山顶变为孤岛，使残存种群陷入全新的环境中。本研究报道了巴西塞拉多（Brazilian Cerrado，全球生物多样性热点区域）境内，5座此类人工新形成岛屿与周边5处大陆样地中，食白蚁壁虎阿玛拉鳞趾虎（Gymnodactylus amarali）的形态与食性差异。岛屿种群的平均猎物体型及食性猎物体型宽度均显著大于大陆种群，这一结果符合预期——因为原本栖息于此的4种同样捕食白蚁、但更偏好大型猎物的大型蜥蜴物种已在岛屿上灭绝。此外，相较于大陆种群，岛屿种群的头部相对体长比例更大；更大的头部更适配所捕食的大型猎物，且头部比例偏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。研究强烈指向平行形态演化现象，因为有证据表明，在淹没造岛之前，未来将成为岛屿的样地与大陆样地的头部相对比例并无差异。雌雄个体均表现出岛屿种群头部相对比例更大的趋势，因此岛屿与大陆样地间的形态差异，不太可能是由岛屿上更为激烈的雄性间配偶竞争所导致的。因此，本研究发现了一个响应人类灾难性扰动的快速（至多15年）独立平行适应性演化案例。