Somatic And Genital Traits Show Reproductive Character Displacement In Two Sympatric Scorpion Species

OVIEDO-DIEGO, MARIELA; MATTONI, CAMILO I.; PERETTI, ALFREDO V.

Cleveland

Congreso; Evolution; 2022

American Society of Naturalists, the Society for the Study of Evolution, and the Society of Systematic Biologists

When two related species coexist in sympatry and reproduce synchronously, sexual attraction, mating and even hybridization between heterospecifics can occur, a phenomenon called reproductive interference (RI). In the face of this, certain key morphological traits in the reproduction of these species can be differentiated in sympatry to avoid the success of heterospecific sexual interactions and some of their associated costs. This mechanism is known as reproductive character displacement (RCD) and would allow species to coexist in sympatry. RCD manifests as a morphological shift in certain characters, resulting in species being more different in sympatry than in allopatry. The interaction between two scorpion species from central Argentina, Urophonius brachycentrus and U. achalensis (Bothriuridae) is an ideal model to evaluate the presence of RCD, since in addition to being sympatric and synchronous, they show chemical sexual attraction and heterospecific mating in the laboratory. We compared the relative size and shape of multiplesexual traits involved in courtship and sperm transfer in males and females from sympatric and allopatric populations using both classical and geometric morphometric and geometric morphometry (Landmarks, Semilandmarks, and Fourier analysis). We found asymmetric RCD (only in U. brachycentrus) of several key male sexual characters for courtship success (pedipalp and apophysis shape), and for sperm transfer (hemispermatophore lamella shape, size of capsular lobe). This would evidence the existence of a possible mechanism to avoid heterospecific mating success and hybridization, although it would not alleviate the costs associated with encountering heterospecific mates. Individuals of U. brachycentrus suffered an increase in size due to the sympatric zone being at lower temperatures and higher altitude than the allopatric zone, which was evidenced by a convergence pattern. We will discuss these results, together with information on chemical communication and behavior in heterospecific encounters, in order to draw conclusions about the presence of RI, asymmetric RCD and itsconsequences in the mating system of these scorpion species.