Mating behaviour and male mate choice in Tribolium castaneum (Coleoptera, Tenebrionidae)

Mate choice by males has received less attention than female choice, despite the recognition that males can incur non-trivial reproductive costs through mating. In this study we investigate male mate choice in the red flour beetle, Tribolium castaneum. We determine whether mate beetles have evolved sensitivity that enables them to discriminate between females and we then examine how males discriminate between females that present different reproductive potentials. Recently-emerged adult females are immature, and we investigate when egg-laying maturity develops, and whether male mating attempts with immature females provide reproductive pay-offs. We show that males are the sex most likely to initiate mating attempts (more than 85% of male-female contacts are male-initiated). Therefore, we test male mating initiations when presented with choices between: (i) immature and mature virgin females; (ii) mature virgin females and previously mated mature females; and (iii) mature females previously mated either with different male or with the test males. Last male sperm precedence exists in T. castaneum and females are polyandrous. Matings with immature females are therefore likely to generate lower fertilization successes than matings with mature females. Furthermore, males are likely to achieve higher total fertilization success when they mate if they precede a rival male's sperm than if they precede their own sperm. Accordingly, we find that: (i) males copulate more frequently with mature, than with immature females; (ii) males do differentiate between virgin and mated females; and (iii) males prefer females that have been inseminated by a different male to those previously inseminated by the test males themselves. The results demonstrate that male T. castaneum recognise female status, display mate choice, and prefer to inseminate females which provide greater reproductive potential.