Data from: Dramatic niche shifts and morphological change in two insular bird species

Colonizations of islands are often associated with rapid morphological divergence. We present two previously unrecognized cases of dramatic morphological change and niche shifts in connection with colonization of tropical forest-covered islands. These evolutionary changes have concealed the fact that the passerine birds madanga, Madanga ruficollis, from Buru, Indonesia, and São Tomé shorttail, Amaurocichla bocagii, from São Tomé, Gulf of Guinea, are forest-adapted members of the family Motacillidae (pipits and wagtails). We show that Madanga has diverged mainly in plumage, which may be the result of selection for improved camouflage in its new arboreal niche, while selection pressures for other morphological changes have probably been weak owing to preadaptations for the novel niche. By contrast, we suggest that Amaurocichla's niche change has led to divergence in both structure and plumage.

岛屿物种定殖事件往往与快速的形态分化密切相关。本研究报道了两起此前未被认知的、与热带森林覆盖岛屿定殖相关的剧烈形态变化与生态位转变案例。这些演化过程曾掩盖了一个核心事实：来自印尼布鲁岛的雀形目鸟类madanga（Madanga ruficollis），以及来自几内亚湾圣多美岛的圣多美短尾雀（Amaurocichla bocagii），实则均为鹡鸰科（Motacillidae，鹨与鹡鸰类）中适应森林生境的类群。研究表明，madanga主要在羽色层面发生分化，这或许是其在全新树栖生态位中提升伪装能力的选择压力所致；而由于该类群对新生境已具备预适应特征，其他形态性状的选择压力大概率较为微弱。与之形成鲜明对比的是，本研究提出，Amaurocichla的生态位转变使其在躯体结构与羽色两个维度均产生了分化。