Data from: Are all forms of defense lost on islands? Persistence of an indirect defensive trait in six island colonists from New Zealand

The loss of defense hypothesis posits that island colonizers experience a release from predation on the mainland and subsequently lose their defensive adaptations. However, while support for the hypothesis from direct defensive traits is abundant, far less is known about indirect defensive traits. Leaf domatia are cave-like structures produced on the underside of leaves that facilitate an indirect defensive interaction with predaceous and microbivorous mites. I tested the loss of defense hypothesis in six domatia-bearing taxa inhabiting New Zealand and its offshore islands. No support for the loss of defense hypothesis was found. Changes in domatia investment were instead associated with changes in leaf size – a trait that has been repeatedly observed to undergo rapid evolution on islands. Overall results suggest that not all types of defense are lost on islands.

防御缺失假说（loss of defense hypothesis）提出，岛屿拓殖物种在大陆环境中会摆脱捕食压力，随后逐渐丧失其防御适应性。尽管直接防御性状为该假说提供了大量支持证据，但学界对间接防御性状的相关认知仍较为匮乏。叶穴（leaf domatia）是生于叶片下表面的洞穴状结构，可与捕食性和食微螨类形成间接防御互作。本研究针对栖息于新西兰及其离岸岛屿的6种具叶穴类群，对防御缺失假说进行了检验。研究未发现支持该假说的证据；叶穴投入量的变化反而与叶片大小的改变相关——叶片大小这一性状在岛屿上的快速演化已被多次观测到。综合结果表明，并非所有类型的防御性状都会在岛屿环境中丧失。