Female mate assessment tactics in a subsocial desert beetle: a test of Janetos’ models

Abstract

The subsocial desert tenebrionid beetle Parastizopus armaticeps is monogamous and nocturnal, with division of labour and female mate selection for large male body size. Mate choice is time-constrained and must take place during the night following sporadic heavy rainfall since pairs can only dig breeding burrows when the sand is moist. Beetles court in small, widely-separated groups. The four tactics proposed by JANETOS (1980), through which females could assess potential mates before coming to a decision, were tested experimentally. Approximately 20% of females adopted the “fixed-threshold” tactic to assess males, all others opting for the “best of n males” tactic. These tactics are considered to be the most advantageous ones when time is limited and the number of prospective mates that can be assessed low, as is the case for P. armaticeps. Females used multiple assessments in “the best of n males tactic”, suggesting that evaluation is constrained by female information retention and integration ability, one of the constraints on sequential comparisons. This tactic also has the highest expected fitness benefits.