Evidence for habitat partitioning based on adaptation to environmental light in a pair of sympatric lizard species

Abstract

Terrestrial habitats exhibit a variety of light environments. If species exhibit evolutionary adaptations of their visual system or signals to habitat light conditions, then these conditions can directly influence the structure of communities. We evaluated habitat light characteristics and visual-signal design in a pair of sympatric species of lizards: Anolis cooki and Anolis cristatellus. We found that each species occupies a distinct microhabitat with respect to light intensity and spectral quality. We measured the relative retinal spectral sensitivity and found significant differences between the species that correlate with differences in habitat spectral quality. We measured the spectral reflectance of the dewlaps (colourful throat fans used in communication), and found that the A. cooki dewlap reflects little ultraviolet (UV), while that of A. cristatellus reflects strongly in the UV. For both species downwelling light (irradiance) is rich in UV. However the background light (radiance) is rich in UV for A. cooki, but low in UV for A. cristatellus. Thus, the dewlap of each species creates a high contrast with the background in the UV. Our findings strongly suggest that these two species are partitioning their habitat through specializations of the visual system and signal design to microhabitat light conditions.

A performance-based cost to honest signalling in male green anole lizards (Anolis carolinensis)

“…If displaying in any or all of these contexts incurs fitness costs through, for example, increased likelihood of predation, then dewlap size might possibly be constrained by receiver-independent costs, regardless of the cost of bite force expression. Indeed, studies of visual signalling in particular suggest that dewlaps play an important role in general anole ecology in contexts besides sexual selection [72,73]. Furthermore, Irschick et al [47] showed that individual male dewlaps decrease in size in both the field and the laboratory following the cessation of major breeding activity in a New Orleans A. carolinensis population, suggesting that there may indeed be some cost to bearing large dewlaps.…”

Alert signals enhance animal communication in “noisy” environments

“…How animals minimize the effects of environmental degradation on signal propagation is a classic focus of communication research (1)(2)(3) and is often central to understanding the way animals communicate (4)(5)(6) and interact with each other (7)(8)(9). Signal detection theory (10) and empirical studies (3) show that simple signal components suffer lower rates of environmental attenuation than more complex, information-rich components.…”

The Anoles of Soroa: Aspects of Their Ecological Relationships

“…Percent displaying is the percentage of time a lizard was dewlapping, head bobbing, or performing some other social display behavior. Data for A. barbatus are taken from Leal and Losos (2000); these data were collected for both males and females, including some subadults, and do not include information on moves per minute.…”

“…The literature on resource partitioning in tropical lizard communities suggests that the use of different perch sites and microhabitats with different irradiance and thermal properties often allows sympatric species to avoid intense interspecific competition (Schoener and Gorman, 1968;Schoener, 1977;Heatwole, 1982;Williams, 1983;Jenssen et al, 1988;Hertz, 1991;Losos, 1992;Powell et al, 1996;Leal and Fleishman, 2002). Martínez Reyes (1995) found 11 anole species at Soroa and noted that most of them perched on tree trunks or shrubs.…”