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

OVIEDO DIEGO, MARIELA; MATTONI, ALFREDO; PERETTI, ALFREDO

Davis, California

Congreso; 2022 AAS Annual Meeting; 2022

American Arachnological Society

Courtship behavior is a critical component of pre-copulatory isolation. Both sexes exchangemultiple signals to assess the specific identity and the mate’s quality, so courtship behaviors and theresponse to them may experience different selective pressures. In sympatric areas, the correct sexualrecognition among conspecifics is critical to prevent heterospecific mating ensuring reproductiveisolation. However, the recognition can fail, leading to heterospecific mating and processes likereproductive interference (RI). Scorpions have a wide repertoire of sexual courtship behaviors. Herewe focused particularly on "female resistance" (FR) (pulling against the male or not moving in themale’s direction during the “promenade” phase). This behavior has been ruled out as amanifestation of sexual conflict in scorpions, being more likely to arise in a mate choice frameworkas a mechanism to assess male quality. However, to date, FR has not been analyzed inheterospecific courtships where this behavior can act as a barrier contributing to reproductiveisolation. Here we assessed the FR in conspecific and heterospecific courtships of two sympatricscorpion species from central Argentina: Urophonius brachycentrus -UB- and Urophoniusachalensis -UA-. Given that these species had RI in pheromone chemical attraction, a matingsystem with scramble competition, and that there is a high chance of encounters betweenheterospecifics, we expect that FR constitutes a selective filter to prevent the culmination ofheterospecific mating. We predict that success in these mating is less likely than in conspecificmating due to behavioral filters as FR, which it’s related to interaction networks that are moredisorganized and less linear. We collected specimens in the field and performed mating trials in thelaboratory in arenas with randomly selected couples: (a) conspecific crosses: UA n=70 , UB n=41 ;(b) heterospecific crosses: ♂UA♀UB n=51 ; ♂UB♀UA n=25. We recorded sexual encounters andconsidered successful mating if sperm transfer is completed. We quantified the duration andfrequency of FR and compared these parameters between conspecific and heterospecific courtshipsusing GLMs in R. Complementarily, we performed an analysis of interaction networks with Gephi,analyzing the linearity and modularity of conspecific and heterospecific courtships and wecompared these parameters with a Mann-Whitney U-test. We found that heterospecific mating wasless successful than conspecific mating, with sperm transfer occurring in only 8% (♂UA♀UB) and18% (♂UB♀UA) of sequences (p=0.004). Compared to conspecific ones, heterospecific courtshipshad almost three 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 in many cases, the pair loosenedtheir pedipalps and the courtship was finished or continued but in a disorganized way, giving rise toless linear and more modular interaction networks (p=0.036). We provide evidence that FR is a veryplastic behavior, which can be modulated according to the mate´s specific identity. Our resultsconfirm that FR could be considered as a behavioral isolating mechanism in heterospecific mating.However, FR represents a partial barrier so we discuss the costs of RI and the use of multiple pre-and post-copulatory barriers in these species.