Husak Jerry F, Fox Stanley F
Department of Zoology, Oklahoma State University, Stillwater, Oklahoma 74078, USA.
Evolution. 2006 Sep;60(9):1888-95.
To understand how selection acts on performance capacity, the ecological role of the performance trait being measured must be determined. Knowing if and when an animal uses maximal performance capacity may give insight into what specific selective pressures may be acting on performance, because individuals are expected to use close to maximal capacity only in contexts important to survival or reproductive success. Furthermore, if an ecological context is important, poor performers are expected to compensate behaviorally. To understand the relative roles of natural and sexual selection on maximal sprint speed capacity we measured maximal sprint speed of collared lizards (Crotaphytus collaris) in the laboratory and field-realized sprint speed for the same individuals in three different contexts (foraging, escaping a predator, and responding to a rival intruder). Females used closer to maximal speed while escaping predators than in the other contexts. Adult males, on the other hand, used closer to maximal speed while responding to an unfamiliar male intruder tethered within their territory. Sprint speeds during foraging attempts were far below maximal capacity for all lizards. Yearlings appeared to compensate for having lower absolute maximal capacity by using a greater percentage of their maximal capacity while foraging and escaping predators than did adults of either sex. We also found evidence for compensation within age and sex classes, where slower individuals used a greater percentage of their maximal capacity than faster individuals. However, this was true only while foraging and escaping predators and not while responding to a rival. Collared lizards appeared to choose microhabitats near refugia such that maximal speed was not necessary to escape predators. Although natural selection for predator avoidance cannot be ruled out as a selective force acting on locomotor performance in collared lizards, intrasexual selection for territory maintenance may be more important for territorial males.
为了理解选择如何作用于性能容量，必须确定所测量的性能特征的生态作用。了解动物是否以及何时使用最大性能容量，可能有助于洞察哪些特定的选择压力可能作用于性能，因为预计个体仅在对生存或繁殖成功至关重要的情况下才会使用接近最大容量。此外，如果一个生态环境很重要，表现不佳的个体预计会通过行为进行补偿。为了理解自然选择和性选择对最大冲刺速度容量的相对作用，我们在实验室中测量了领鞭蜥（Crotaphytus collaris）的最大冲刺速度，并在三种不同情境（觅食、逃避捕食者和应对竞争对手入侵者）下测量了相同个体在野外实现的冲刺速度。雌性在逃避捕食者时比在其他情境下更接近使用最大速度。另一方面，成年雄性在应对被拴在其领地内的陌生雄性入侵者时更接近使用最大速度。所有蜥蜴在觅食尝试期间的冲刺速度都远低于最大容量。一岁幼蜥似乎通过在觅食和逃避捕食者时比任何性别的成年蜥蜴使用更大比例的最大容量，来弥补其较低的绝对最大容量。我们还发现了在年龄和性别类别内存在补偿的证据，即速度较慢的个体比速度较快的个体使用更大比例的最大容量。然而，这仅在觅食和逃避捕食者时成立，而在应对竞争对手时则不然。领鞭蜥似乎会选择避难所附近的微生境，这样就不需要最大速度来逃避捕食者。虽然不能排除为避免被捕食而进行的自然选择作为作用于领鞭蜥运动性能的选择力量，但对于领地雄性来说，为维持领地而进行的同性选择可能更为重要。
