Males make mistakes but females call the shots: female resistance as a partial reproductive isolating mechanism in scorpions

OVIEDO DIEGO, M.; MATTONI, C. I.; PERETTI, A. V.

California, Davis USA.

Congreso; 2022 American Arachnological Society Meeting; 2022

American Arachnological Society

Courtship behavior is a critical component ofpre-copulatory isolation. Both sexes exchange multiple signals to assess thequality of their mate and their specific identity, so courtship behaviors andthe response to them may experience different selective pressures. In sympatricareas, the correct sexual recognition among conspecifics is critical to ensurereproductive isolation. However, the recognition can fail,leading to heterospecific matings and processes like reproductive interference(RI). Scorpions have a wide repertoire of courthsip sexual behaviors, althoughhere we focused particularly on "female resistance" (FR) (pullingagainst the male or not moving in the direction proposed by the male). Thisbehavior has been ruled out as a manifestation of sexual conflict in scorpions,being more likely to arise in a mate choice framework as a mechanism to assessmale quality. However, to date, FR has not been analyzed in heterospecificcourtships where this behavior can act as a filter contributing to reproductiveisolation. Here we assessed the FR in conspecific and heterospecific courtshipsof two sympatric and synchronous scorpion species from central Argentina: Urophoniusbrachycentrus -UB- and Urophonius achalensis -UA-. Given that thesespecies had RI in pheromone chemical attraction, a mating system with scramblecompetition and that there is a high chance of encounters between heterospecifics,we expect that FR constitutes a selective filter to prevent the culmination of intercrosses.We predict that successuful intercrosses are less likely than conspecificmatings due to behavioral filters as FR, which it’s related with interactionnetworks more disorganized and less linear. We collected specimens in the fieldand performed mating trials in the laboratory in arenas with randomly selectedcouples: (a) conspecific crosses: UA n=70 , UB n=41 ; (b) heterospecificcrosses: ♂UA♀UB n=51 ; ♂UB♀UA n=25. We recorded sexual encounters andconsidered successful mating if sperm transfer occurred correctly. Wequantified the duration and frequency of FR and we compared these parametersbetween conspecific and heterospecific courtships using GLMs in R.Complementarily, we performed an analysis of interaction networks with Gephi,analyzing the linearity and modularity of conspecific and heterospecificcourtships and we compared these parameters with a Mann-Whitney U-test. Wefound that intercrosses were less successful than conspecific matings, withsperm transfer occurring in only 8% (♂UA♀UB) and 18% (♂UB♀UA) of matings(p=0.004). Compared to conspecific ones, heterospecific courtships had almostthree times more FR events (p=0.037) and a longer duration of these events(p=0.037). Consequently, heterospecific courtships were longer (p=0.041) and inmany cases, the pair loosened their pedipalps and the courtship was finished orcontinued but in a disorganized way, giving rise to less linear and more modularinteraction networks (p=0.036). We provided evidence that FR is a very plasticbehavior, which can be different according to the mate's specific identity. Ourresults confirm that FR could be considered as a behavioral filter in intercrossesalthough it is important to note that FR was only a partial barrier so we willdiscuss the costs of RI and the use of more than one pre- and post-copulatorybarrier in these species.