Heritable variation in host quality as measured through an ectoparasite's performance

Male mating preference in an ixodid tick

Background

Mate choice is a fundamental element of sexual selection and has the potential to shape the evolution of traits. Mate choice based on body size has been shown to be a common trait in several arthropod species. In hard ticks, a taxon of medical and veterinary importance, engorgement weight is positively correlated with reproductive output but it is unknown whether adult males show mate choice. Here, we experimentally investigated whether males (i) use chemical cues to choose their mating partner, (ii) consistently choose for the same female individual and (iii) prefer females with highest weight after feeding.

Methods

We used two experimental setups which allowed chemical communication between ticks: (i) a horizontal tube preventing physical contact with the female and (ii) an arena where tactile cues were allowed. In total, we tested 62 different triads in 124 tests (66 tests in the horizontal tube and 58 in the arena) composed of one male that could choose between two engorged females. Specifically, we tested 42 triads in the tube and 46 in the arena; 24 triads were repeatedly tested in the tube while 38 triads were tested in both setups.

Results

We found no preference for individual or heavier females in either setup. However, in the horizontal tube setup, males significantly preferred females that were not visited by them in the previous test.

Conclusions

Our results suggest a lack of male mate choice despite heavier females having higher fecundity. However, future studies should take into account that males may recognize the potential mating partners they previously met.

Graphical Abstract

Digest: Great tits and their ticks: Life-history traits affect tick fitness

Ectoparasites such as ticks face many challenges to reproduce. They must maximize the size of their blood meal while avoiding being removed by their host. In a new study, Fracasso and colleagues followed the fate of individual ticks to determine which life-history traits impact tick fitness. Their findings reveal a complex interplay between numerous parameters, including feeding time and engorgement weight. The situation is likely even more complicated when considering vector-borne pathogens.