The evolution of jumping performance in Caribbean Anolis lizards: solutions to biomechanical trade-offs.

ABSTRACT

Adaptationist theory predicts that species will evolve functional specializations for occupying different ecological niches. However, whereas performance traits are often complex, most comparative functional studies examine only simple measures of performance (e.g., sprint speed). Here we examine multiple facets of jumping biomechanics in 12 species of Caribbean Anolis lizards. These 12 species represent six ecomorphs, which are distinct ecological and morphological entities that have independently evolved on different Caribbean islands. We first show that the optimal angles for jumping maximum horizontal distances range from 39 degrees to 42 degrees, but the average jump angle of the 12 species is about 36 degrees. Interestingly, these "suboptimal" jumping angles result in only a small decrement in jump distance but substantial savings in flight duration and jump height. Further, our data show that the two key variables associated with increased jumping velocity (hindlimb length and takeoff acceleration) are independent of one another. Thus, there are two possible ways to achieve superior jumping capabilities to evolve more muscular limbs--as stronger legs will produce more force and, hence, more acceleration--or evolve longer limbs. Our data show that anole species face trade-offs that prevent them from simultaneously optimizing different aspects of jumping ability but that they appear to have evolved behaviors that partially overcome these trade-offs.