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.

岛屿殖民事件往往伴随快速的形态分化。本研究报道了两例此前未被认知的、与热带森林覆盖岛屿殖民相关的显著形态变化与生态位转移事件。这些演化变化曾掩盖了一个关键事实：来自印尼布鲁岛的鸣禽马丹加鸟（Madanga ruficollis），以及几内亚湾圣多美岛的圣多美短尾鸟（Amaurocichla bocagii），实则为鹡鸰科（Motacillidae，即鹨与鹡鸰）的森林适应性类群。研究表明，马丹加鸟的分化主要体现在羽色层面，这或是其在全新树栖生态位中提升伪装能力的选择结果；而由于该类群已对新生态位存在预适应，其余形态变化所受的选择压力或许较弱。与之相反，本研究认为圣多美短尾鸟的生态位转变同时引发了形态结构与羽色两方面的分化。