Physiology complements population structure of two endemic log-dwelling beetles

Given rapid, global land modification and the likelihood of major global climate changes, it is becoming increasingly important to understand the physiological limits and capabilities of species to allow more accurate prediction of species' distributions under different scenarios of climate and landscape management. We studied whether the different habitat requirements of two species of tenebrionid beetles in temperate eucalypt forest could explain their patterns of dispersal and gene flow by applying flow-through respirometry to analysis of their physiological responses to different, ecologically relevant temperatures. Both Adelium calosomoides and Apasis puncticeps showed sensitivity to increasing temperatures (in terms of water loss), but Ap. puncticeps lost more water per unit of CO₂ produced than did Ad. calosomoides. Recovery time from chill coma was also significantly longer for Ap. puncticeps than Ad. calosomoides. This supported prior qualitative assessment that Ap. puncticeps is more of a habitat specialist than Ad. calosomoides, at least concerning the critical factor of moisture requirements, and is consistent with stronger population genetic patterning and inferred low mobility of Ap. puncticeps. Despite its relatively lower mobility as deduced from population genetic structure, Ap. puncticeps walked four times faster than Ad. calosomoides in a laboratory assay, indicating that, for these species, mobility and gene flow are influenced more by physiological limitations than by speed.