Sexual Competition, Coercive Mating and Mate Assessment in the One‐Sided Livebearer, Jenynsia multidentata: Are They Predictive of Sexual Dimorphism?

• DOI: 10.1046/j.1439-0310.2000.00620.x
• Publication Date: 2003-03-11T20:16:35Z
• Authors: Angelo Bisazza; Silvia Manfredi; Andrea Pilastro
• Keywords: Sexual dimorphism; Antagonistic Coevolution; Operational sex ratio

Abstract We investigated the mechanisms of sexual selection operating on body size in one‐sided livebearer ( Jenynsia multidentata ), a small fish characterized by male dwarfism. Mating is coercive: males approach females from behind and try to thrust their copulatory organ at female genital pore. Females counter males' mating attempts either swimming away or attacking them. tested hypothesis that components favouring (sexual coercion) were more effective than those large (male competition mate choice). When alone, had significantly higher success males. The proportion successful was also positively correlated with size. two competed for same female, significant advantage over one. With 1 : sex ratio, large‐male vanished because each tended follow different female. Large males, however, preferentially defended females, thus compelling engage smaller, less fecund females. Males did not discriminate between gravid non‐gravid but preferred larger This preference disappeared when much smaller probably relation risk being eaten injured In choice chamber, male‐deprived sperm storage depleted remained close showed individuals, behaviour observed non‐deprived Nonetheless, placed aquarium, all avoidance aggression. Struggling may represent way which assesses skill endurance