Mourão M A N, Peixoto P E C
Programa de Pós-Graduação em Ecologia e Recursos Naturais, Universidade Federal do Ceará, Ceará, Brazil Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis, Brasília CEP 70818-900, Distrito Federal, Brazil
Departamento de Ciências Biológicas, Universidade Estadual de Feira de Santana, Feira de Santana CEP 44036-900, Bahia, Brazil
J Insect Sci. 2014;14:89. doi: 10.1093/jis/14.1.89.
Males of many animal species show intraspecific disputes for mating territories that range from displays without physical contact to physical fights with risk of injury. This variation motivated the proposition of different models that suggest possible rules used by rivals to decide the contest winner. To evaluate those models, it is necessary to identify how males behave during the fight and the individual attributes that determine their fighting ability (resource holding potential). For this, males of the dragonfly Macrothemis imitans (Karsch) (Odonata: Libellulidae) were used to evaluate two hypotheses conditioned on the occurrence of physical contact during the fight: if the contests occur with physical contact, features related to size should determine male resource holding potential, and if males do not exhibit physical contact during the contests, features that confer greater endurance should determine resource holding potential. To assess these hypotheses, we collected males that had ownership of territories (resident males) and males that occupied the territory after we removed the resident males (substitute males). After the capture, the resident and substitute males were transferred to the laboratory for measurements of wing area, dry weight, thoracic muscle mass, and fat content. The results showed that resident males do not differ in any measured trait from substitutes. Because the fights occur with physical contact, it is intriguing that resident males do not possess higher fighting capacity than intruders. Perhaps physical contact does not incur high costs during the fight, and other asymmetries, such as motivation associated with prior residency of the disputed territory, determine the contest winner.
许多动物物种的雄性会为争夺交配领地而进行种内争斗，这些争斗的形式多样，从无身体接触的展示到可能导致受伤风险的肢体搏斗。这种差异促使人们提出了不同的模型，这些模型暗示了竞争对手用来决定比赛胜负的可能规则。为了评估这些模型，有必要确定雄性在争斗过程中的行为方式以及决定其战斗能力（资源占有潜力）的个体属性。为此，人们利用雄性模仿大蜻（Macrothemis imitans (Karsch)，蜻蜓目：蜻科）来评估两个基于争斗中是否发生身体接触的假设：如果争斗发生身体接触，与体型相关的特征应决定雄性的资源占有潜力；如果雄性在争斗中不表现出身体接触，赋予更高耐力的特征应决定资源占有潜力。为了评估这些假设，我们收集了拥有领地的雄性（常住雄性）以及在我们移除常住雄性后占据该领地的雄性（替代雄性）。捕获后，将常住雄性和替代雄性转移到实验室，测量它们的翅面积、干重、胸肌质量和脂肪含量。结果表明，常住雄性在任何测量特征上与替代雄性均无差异。由于争斗会发生身体接触，常住雄性的战斗能力并不比入侵者高，这一点很耐人寻味。也许身体接触在争斗过程中不会带来高昂成本，而其他不对称因素，比如与争议领地先前居住权相关的动机，决定了比赛的胜负。
