No abstract

The urban heat island effect, where urban areas exhibit higher temperatures than less‐developed suburban and natural habitats, occurs in cities across the globe and is well understood from a physical perspective and at broad spatial scales. However, very little is known about how thermal variation caused by urbanization influences the ability of organisms to live in cities. Ectotherms are sensitive to environmental changes that affect thermal conditions, and therefore, increased urban temperatures may pose significant challenges to thermoregulation and alter temperature‐dependent activity. To evaluate whether these changes to the thermal environment affect the persistence and dispersal of ectothermic species in urban areas, we studied two species of Anolis lizards (Anolis cristatellus and Anolis sagrei) introduced to Miami‐Dade County, FL, USA, where they occur in both urban and natural habitats. We calculated canopy openness and measured operative temperature (Te), which estimates the distribution of body temperatures in a non‐thermoregulating population, in four urban and four natural sites. We also captured lizards throughout the day and recorded their internal body temperature (Tb). We found that urban areas had more open canopies and higher Te compared to natural habitats. Laboratory trials showed that A. cristatellus preferred lower temperatures than A. sagrei. Urban sites currently occupied by each species appear to lower thermoregulatory costs for both species, but only A. sagreihad field Tb that were more often within their preferred temperature range in urban habitats compared to natural areas. Furthermore, based on available Te within each species' preferred temperature range, urban sites with only A. sagrei appear less suitable for A. cristatellus, whereas natural sites with only A. cristatellus are less suitable for A. sagrei. These results highlight how the thermal properties of urban areas contribute to patterns of persistence and dispersal, particularly relevant for studying species invasions worldwide.

Summary As animals move through their environments, they encounter a variety of substrates, which have important effects on their locomotor performance. Habitat modification can alter the types of substrates available for locomotion. In particular, many types of artificial substrates have been added to urban areas, but effects of these novel surfaces on animal locomotion are little known. In this study, we assessed locomotor performance of two Anolis lizard species (A. cristatellus and A. stratulus) on substrates that varied in inclination and surface roughness. Rough substrates represented the tree trunks and branches typically used in natural forest habitats, whereas smooth, vertical substrates captured the qualities of artificial surfaces, such as posts and walls, available in human‐modified habitats. We then observed habitat use to test the habitat constraint hypothesis – that lizards should more frequently occupy portions of the habitat in which they perform better. Increased inclination and decreased surface roughness caused lizards to run slower. Both A. cristatellus and A. stratulus ran slowest on the smooth, vertical surface, and A. cristatellus often slipped and fell on this surface. In contrast to predictions, both species frequently used smooth, vertical substrates in the wild. Anolis cristatellus occupied artificial substrates 73% of the time in human‐modified habitats despite performing worse than A. stratulus on the smooth, vertical track. We therefore rejected the habitat constraint hypothesis for anoles in these human‐modified habitats. Despite overall poor performance on the smooth, vertical track, A. cristatellus had a significant morphology–performance relationship that supports the prediction that selection should favour smaller lizards with relatively longer limbs in human‐modified habitats. The smaller bodied A. stratulus performed better than A. cristatellus on smooth, vertical substrates and therefore may not be exposed to the same selective pressures. We contend that habitat modification by humans may alter morphology‐performance–habitat use relationships found in natural habitats. This may lead to changes in selective pressures for some species, which may influence their ability to occupy human‐modified habitats such as cities.

. (2013). Sexual dimorphisms in habitat-specific morphology and behavior in the green anole lizard. Journal Of Zoology, 290(2), 135-142. doi:10.1111/jzo.12020 Sexual dimorphisms in habitat-specific morphology and behavior in the green anole lizard AbstractSpecies that occur in variable environments often exhibit morphological and behavioral traits that are specific to local habitats. Because the ability to move effectively is closely associated with structural habitat, locomotor traits may be particularly sensitive to fine-scale habitat differences. Anolis lizards provide an excellent opportunity to study the relationship between locomotion and natural perch use in the field, as laboratory studies have demonstrated that lizards that use broader perches develop longer limbs and have higher sprint speeds. We examined Anolis carolinensis (the green anole) in three habitats in close proximity. Our goals were to determine whether habitat-specific differences in hindlimb and toe morphologies occurred in a population in which perch size was variable but not manipulated, whether locomotor behaviors were associated with these morphologies, and whether habitat-specific traits differed between the sexes. We found that while juveniles in the three habitats did not differ in limb or toe morphology, adult females using broader perches had relatively longer limbs than females using narrower perches. Females also differed in toe length across habitats, but not in relation to perch diameter. Males, in contrast, exhibited differing growth patterns (allometry) in these traits, and marginal differences in locomotor behavior. Together, these results suggest that sex-specific responses in morphology and behavior, consistent with experimental observations of phenotypic plasticity, provide a mechanism for refining local habitat use.

preference 8 2 ABSTRACT 9Persistence of animals in urban habitats, a stark environmental contrast to natural 10 habitats, can be explained through evaluating the mechanisms behind organism-habitat 11 interactions. One of the most notable effects of urbanization is the change in structural habitat; 12 vegetation is removed and modified, favoring large trees and adding artificial structures in cities, 13 which may alter how organismal preferences for aspects of the habitat are realized. We evaluated 14 the mechanisms by which structural habitat changes associated with urbanization alter the 15 available vegetation and substrates on which two species of Anolis lizards perch in urban and 16 natural forest sites in Miami, FL. We also experimentally assessed habitat preference in the lab 17 to establish the mechanism behind habitat selection. We found that vegetation was broader in 18 urban areas compared to natural habitats, and artificial structures in urban areas were more than 19 twice the diameter of available natural perches. Lizards expressed their preference for broad 20 perches by selecting broader vegetation and artificial structures compared to their availability in 21 both habitats. With the increased availability of broad substrates in urban areas, perch diameters 22 selected by lizards resulted in an expansion of this aspect of the structural habitat niche for both 23 species. The two species differed, however, in other responses to altered urban habitats. Anolis 24 cristatellus tended to avoid artificial substrates, whereas A. sagrei used both natural and artificial 25 structures in proportion to their availabilities. This study provides a mechanistic explanation for 26 how urbanization alters structural habitats, leading to niche expansion for organisms living in 27 cities.28