Behavioural ecology of tropical cave cockroaches: preliminary field studies with evolutionary implications

Tropical troglobites are unlikely to have evolved from troglophiles isolated by climatic extremes, because the latter were not subjected to the severe temperatures that their temperate counterparts endured during the Pleistocene. If pre‐adapted forms enter tropical caves directly and undergo adaptive shifts, it is possible that they do so in search of a moist substrate. the present study is the first field test of this hypothesis. the preference of the tropical troglophile Paratemnopteryx sp. (Blattodea: Blattellidae) for moist leaves compared with dry leaves was studied in a tropical cave. the relative attractiveness of leaves in leaf litter traps was compared at a range of different relative humidities in the cave. the relative attractiveness of wet leaves was found to increase as the cave atmosphere became progressively drier towards the cave entrance. I suggest that some tropical troglophiles seek the wet leaf litter available in caves, and that they may remain in deep caves which provide this resource without climatic isolation events keeping them there. This finding lends empirical support to the idea that many species from the great variety of tropical organisms invade caves, resulting in what has recently been shown to be a tropical cave fauna relatively rich in troglobites.