Contrasting age structures in cave cricket populations: patterns and significance

1. Adaptation to life in caves, as a seasonally constant environment, is expected to affect several life history traits. In this paper we investigate the age structure and phenology of twenty-seven Dolichopoda cave cricket populations from artificial and natural caves subjected to different environmental regimes and to different availability of food resources. 2. Morphometric data clearly revealed the occurrence of different age structures and phenology, basically indicating two contrasting patterns. 3. In artificial caves, which have been colonized by Dolichopoda only in historical times and where food resources and climate are chiefly dependent upon surface environment, age structure was seasonal. In contrast, in most natural caves, where cricket colonization appears to be much older and stability of both climatic parameters and trophic resources is higher, age structure was diverse and aseasonal. 4. However, a seasonal age structure also occurs in natural caves characterized by either recent origin or by a low temperature regime. This suggests that age structure in Dolichopoda is influenced by historical factors, stability of food resources and also by environmental stress.