Out on a limb: the differential effect of substrate diameter on acceleration capacity inAnolislizards

Abstract

How animals manage to effectively move around in complex arboreal environments is intriguing. Not only may perch density and inter-perch distance vary dramatically, but when moving about on, or in between trees, animals will come across a wide range of substrates differing in inclination, texture and diameter. Since different structural elements within the arboreal habitat pose different functional demands on the locomotor system, arboreal habitats are typically regarded as complex environments that are difficult to exploit. A wide diversity of organisms, however, seems capable of doing so, and examples of arboreal species exist for most tetrapod taxa (e.g. amphibians, reptiles, birds, mammals), many of which show distinct morphological and/or behavioural specializations to an arboreal lifestyle, such as the prehensile tail in monkeys (Lemelin, 1995), toe pads in frogs (Hanna and Barnes, 1991) and geckos (e.g. Autumn and Peattie, 2002), or the walking gait and prehensile feet in chameleons (Peterson, 1984) and didelphids (e.g. Lemelin et al., 2003).However, despite these specializations, locomotor performance will not be optimized on all substrates simultaneously. For instance, differences in inclination (e.g. Huey and Hertz, 1982;Huey and Hertz, 1984;Vilensky et al., 1994;Farley, 1997;Irschick and Jayne, 1998;Vanhooydonck and Van Damme, 2001), substrate width (e.g. Losos and Sinervo, 1989;Sinervo and Losos, 1991;Losos et al., 1993;Losos and Irschick, 1996;Bonser, 1999;Dunbar and Badam, 2000;Schmitt, 2003;Stevens, 2003;Lammers and Biknevicius, 2004;Demes et al., 2006) and texture (e.g. Zani, 2000;Claussen et al., 2002;Dai et al., 2002;Kerdok et al., 2002;Vanhooydonck et al., 2005) have all been shown to affect locomotor performance traits in a wide range of organisms. Even more so, some structural elements are known to mediate performance trade-offs. Substrate size, for instance, plays a mediating role in the trade-off between stability and speed. Whereas on broad surfaces (e.g. on the ground) high sprint speed can be attained without detrimentally affecting stability, on narrow surfaces (e.g. branches) high stability leads to decreased sprint performance (Peterson, 1984;Cartmill, 1985;Losos and Sinervo, 1989; Sinervo and Losos, 1991; Losos etWe investigated how substrate diameter affects acceleration performance in three Anolis lizard species (A. sagrei, A. carolinensis and A. valencienni), representing three different ecomorphs (trunk-ground, trunk-crown, and twig, respectively). We did so by measuring maximal acceleration capacity of the three species on a broad and narrow dowel. In addition to acceleration capacity, we quantified maximal sprint speed on both dowels. Both acceleration capacity and sprint speed are affected by substrate diameter, but the way in which they are, differs among species. Acceleration capacity in the trunk-ground anole, A. sagrei, was least affected by dowel diameter, whereas it was greatly reduced on the narrow dowel in the twig anole, A. valencienni. Sprint speed on the narrow dow...

Perch diameter and branching patterns have interactive effects on the locomotion and path choice of anole lizards

“…Some anoles sprinting on cylinders require more than 0.2s to attain maximal speed (Vanhooydonck et al, 2006), which corresponds to one or two strides for the species in our study (Fig.8). In an extreme case, even if a lizard accelerated to maximal speed (with a constant acceleration) within a single stride and paused just an instant after each stride, it could not exceed an overall average speed equal to one-half its maximal speed.…”

How forelimb and hindlimb function changes with incline and perch diameter in the green anole,Anolis carolinensis

“…Narrower perches increase the chance of falling by constraining foot placement to a narrower base of support (Cartmill, 1985;Preuschoft, 2002), and often result in decreased performance (Losos and Sinervo, 1989;Losos and Irschick, 1996;Vanhooydonck et al, 2006a; but see Schmidt and Fischer, 2010). This is likely a result of kinematic changes necessary for increased stability; lowering the Limb function changes in Anolis CoM by adopting a crouched/sprawled posture through greater limb flexion (Peterson, 1984;Schmitt, 1994;Higham and Jayne, 2004a;Franz et al, 2005;Schmidt and Fischer, 2010) and increasing duty factor (Lammers and Biknevicius, 2004;Franz et al, 2005;Lammers, 2007;Gálvez-López et al, 2011) reduce peak vertical forces and are common strategies for dealing with narrow substrates in a range of vertebrate taxa.…”

“…In particular, the evolution, morphology, and locomotor behavior and performance of Anolis ecomorphs, in relation to habitat structure, have been studied extensively (Pounds, 1988;Losos and Sinervo, 1989;Losos, 1990a;Losos, 1990b;Losos, 1994;Losos and Irschick, 1996;Irschick and Losos, 1999;Higham et al, 2001;Perry et al, 2004;Toro et al, 2004;Vanhooydonck et al, 2006a). However, only a single study has examined three-dimensional kinematics of the hindlimb in response to these challenges (Spezzano and Jayne, 2004).…”

Total recoil: perch compliance alters jumping performance and kinematics in green anole lizards (Anolis carolinensis)

“…Although these studies are representative of aspects of locomotion of many animals, few studies have directly addressed the locomotor challenges of animals that inhabit structurally complex arboreal habitats, with some exceptions (e.g. Bonser, 1999;Spezzano and Jayne, 2004;Vanhooydonck et al, 2006). For arboreal animals, the interaction between individuals and their habitat can be complex because of the variability in perch characteristics, such as diameter, length, angle and compliance (Irschick and Losos, 1999;Mattingly and Jayne, 2004).…”

“…For example, there are 400+ species of Anolis lizards, the majority of which use a variety of arboreal habitats and regularly use jumping to move around (Irschick and Losos, 1999). Anole ecology and locomotion has been widely studied (Calsbeek and Irschick, 2007;Irschick and Losos, 1999;Losos and Sinervo, 1989;Spezzano and Jayne, 2004;Vanhooydonck et al, 2006), although one anole species has been particularly well studied in terms of jumping, namely the green anole, A. carolinensis Voigt 1832 (Bels et al, 1992;Gillis et al, 2009;Kuo et al, 2011;Losos and Irschick, 1996;Toro et al, 2003;Vanhooydonck et al, 2005). However, the effect of perch compliance on this species, or any small (<65g) species, is unknown.…”