The blue lizard spandrel and the island syndrome

摘要: Many small vertebrates on islands grow larger, mature later, lay smaller clutches/litters, and are less sexually dimorphic aggressive than their mainland relatives. This set of observations is referred to as the 'Island Syndrome'. The syndrome linked high population density islands. We predicted that when low and/or fluctuating insular may evolve correlated trait shifts running opposite Island Syndrome, which we collectively refer 'reversed island syndrome' (RIS) hypothesis. On proximate level, hypothesized RIS caused by increased activity levels in melanocortin receptors. Melanocortins postranslational products proopiomelanocortin gene, controls pleiotropically pigmentation, aggressiveness, sexual activity, food intake vertebrates. tested hypothesis performing a number behavioral, genetic, ontogenetic tests blue colored variant Italian Wall lizard Podarcis sicula, living off Southern coast. this blue-colored was generally highly from one year next. In keeping with our predictions, lizards were more Insular males had wide, peramorphic heads. growth rate females slower rates individuals both sexes, males. Consequently, size shape dimorphism higher Island. As predicted, receptors much active population. have individuals, consistent be adaptive an unpredictable environment such Licosa sexes spent time basking suspect by-product (spandrel) positive selection for melanocortins contend either or annually result environmental unpredictability, it advantageous behave aggressively, raise intake, allocate energy into reproduction.