Divergent habitat use of two urban lizard species

Faunal responses to anthropogenic habitat modification represent an important aspect of global change. In Puerto Rico, two species of arboreal lizard, Anolis cristatellus and A. stratulus, are commonly encountered in urban areas, yet seem to use the urban habitat in different ways. In this study, we quantified differences in habitat use between these two species in an urban setting. For each species, we measured habitat use and preference, and the niche space of each taxon, with respect to manmade features of the urban environment. To measure niche space of these species in an urban environment, we collected data from a total of six urban sites across four different municipalities on the island of Puerto Rico. We quantified relative abundance of both species, their habitat use, and the available habitat in the environment to measure both microhabitat preference in an urban setting, as well as niche partitioning between the two different lizards. Overall, we found that the two species utilize different portions of the urban habitat. Anolis stratulus tends to use more “natural” portions of the urban environment (i.e., trees and other cultivated vegetation), whereas A. cristatellus more frequently uses anthropogenic structures. We also found that aspects of habitat discrimination in urban areas mirror a pattern measured in prior studies for forested sites in which A. stratulus was found to perch higher than A. cristatellus and preferred lower temperatures and greater canopy cover. In our study, we found that the multivariate niche space occupied by A. stratulus did not differ from the available niche space in natural portions of the urban environment and in turn represented a subset of the niche space occupied by A. cristatellus. The unique niche space occupied by A. cristatellus corresponds to manmade aspects of the urban environment generally not utilized by A. stratulus. Our results demonstrate that some species are merely tolerant of urbanization while others utilize urban habitats in novel ways. This finding has implications for long-term persistence in urban habitats and suggests that loss of natural habitat elements may lead to nonrandom species extirpations as urbanization intensifies. © 2017 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd

Evolutionary Effects of Urbanization on the Tropical Lizard Genus Anolis

Urbanization is a dimension of global change with significant ecological and evolutionary consequences that will continue to grow in its importance as we increasingly transform natural areas for our use. I hypothesize that urban persistent animals, specifically neotropical lizards in the genus Anolis (anoles), face novel selection pressures leading to shifts in habitat use and phenotype. In my dissertation, I first explore how the altered urban environment has impacted habitat use. I demonstrate that of two commonly encountered urban anoles in Puerto Rico, only one (Anolis cristatellus) exploits anthropogenic habitat where it is likely exposed to unique selective pressures as it expands its niche space. Among these altered selective pressures are predation and intraspecific competition, evidenced by differences in injury rates between environments. This in turn sets the stage for rapid adaptive change. I find that urban A. cristatellus show predictable and heritable shifts in functionally relevant traits between forest and urban populations and furthermore that these traits have consequences for locomotor performance in the urban environment. This helps provide a mechanistic understanding of the natural selection that is likely responsible for measured phenotypic changes between environments. Finally, I consider responses to urbanization from a broader perspective by examining the pattern of tolerance to urban areas across all Caribbean anoles. This final analysis indicates that species adapted to hotter and drier environments may be pre-adapted to urban environments and that related species share similar tolerance to urbanization. This could result in non-random species loss as urbanization progresses. In sum, my research sheds light on the complex ecological and evolutionary ways in which tropical lizards have responded and may be adapting to anthropogenic global change

Colas de la ciudad: autotomía caudal en el lagarto tropical, anolis cristatellus, en áreas urbanas y naturales de Puerto Rico

Urbanization creates drastic changes in habitat and presents considerable challenges and new sources of predation to urban-dwelling herpetofauna. Research on lizards has documented increased rates of mortality in urban areas due to generalist predators such as raccoons, feral cats, and domestic animals. Caudal autotomy (self-amputation of the tail) is a defense mechanism used to escape predation in a wide range and large number of lizard species. The tail is autotomized to evade capture, and in most species with autotomy, the tail is regenerated partially or completely. Caudal autotomy can be used as an indirect measure of predation environment; however, few prior studies have used lizard caudal autotomy to measure the predation environment of urban areas. We compared caudal autotomy rates in the Puerto Rican crested anole, Anolis cristatellus, between urban and natural sites in four Puerto Rican municipalities. Across all municipalities, we found the frequency of caudal autotomy and regeneration to be consistently, significantly higher in urban than in natural areas. Our findings suggest that differences exist in the predation regime experienced by lizards in urban and natural habitats across the island of Puerto Rico. At this time, however, we are not able to identify the specific nature of the difference in predation regime between sites. The difference in autotomy rate that we found may be driven by higher predation pressure in urban areas, differences in the predator assemblage between sites, or simply lower predator efficiency in urban habitats

Linking locomotor performance to morphological shifts in urban lizards

Urban habitats are drastically modified from their natural state, creating unique challenges and selection pressures for organisms that reside in them. We compared locomotor performance of Anolis lizards from urban and forest habitats on tracks differing in angle and substrate, and found that using artificial substrates came at a cost: lizards ran substantially slower and frequently lost traction on man-made surfaces compared to bark. We found that various morphological traits were positively correlated with sprint speed and that these same traits were significantly larger in urban compared to forest lizards. We found that urban lizards ran faster on both man-made and natural surfaces, suggesting similar mechanisms improve locomotor performance on both classes of substrate. Thus, lizards in urban areas may be under selection to run faster on all flat surfaces, while forest lizards face competing demands of running, jumping and clinging to narrow perches. Novel locomotor challenges posed by urban habitats likely have fitness consequences for lizards that cannot effectively use manmade surfaces, providing a mechanistic basis for observed phenotypic shifts in urban populations of this species. © 2018 The Author(s) Published by the Royal Society. All rights reserved

Linking locomotor performance to morphological shifts in urban lizards

Urban habitats are drastically modified from their natural state, creating unique challenges and selection pressures for organisms that reside in them. We compared locomotor performance of Anolis lizards from urban and forest habitats on tracks differing in angle and substrate, and found that using artificial substrates came at a cost: lizards ran substantially slower and frequently lost traction on man-made surfaces compared to bark. We found that various morphological traits were positively correlated with sprint speed and that these same traits were significantly larger in urban compared to forest lizards. We found that urban lizards ran faster on both man-made and natural surfaces, suggesting similar mechanisms improve locomotor performance on both classes of substrate. Thus, lizards in urban areas may be under selection to run faster on all flat surfaces, while forest lizards face competing demands of running, jumping and clinging to narrow perches. Novel locomotor challenges posed by urban habitats likely have fitness consequences for lizards that cannot effectively use manmade surfaces, providing a mechanistic basis for observed phenotypic shifts in urban populations of this species. © 2018 The Author(s) Published by the Royal Society. All rights reserved

Data from: Linking locomotor performance to morphological shifts in urban lizards

Urban habitats are drastically modified from their natural state, creating unique challenges and selection pressures for organisms that reside in them. We compared locomotor performance of Anolis lizards from urban and forest habitats on tracks differing in angle and substrate, and found that using artificial substrates came at a cost: lizards ran substantially slower and frequently lost traction on man-made surfaces compared to bark. We found that various morphological traits were positively correlated with sprint speed and that these same traits were significantly larger in urban compared to forest lizards. We found that urban lizards ran faster on both man-made and natural surfaces, suggesting similar mechanisms improve locomotor performance on both classes of substrate. Thus, lizards in urban areas may be under selection to run faster on all flat surfaces, while forest lizards face competing demands of running, jumping, and clinging to narrow perches. Novel locomotor challenges posed by urban habitats likely have fitness consequences for lizards that cannot effectively use man-made surfaces, providing a mechanistic basis for observed phenotypic shifts in urban populations of this species

Data from: Divergent habitat use of two urban lizard species

Faunal responses to anthropogenic habitat modification represent an important aspect of global change. In Puerto Rico, two species of arboreal lizard, Anolis cristatellus and A. stratulus, are commonly encountered in urban areas, yet seem to use the urban habitat in different ways. In this study, we quantified differences in habitat use between these two species in an urban setting. For each species, we measured habitat use and preference, and the niche space of each taxon, with respect to manmade features of the urban environment. To measure niche space of these species in an urban environment, we collected data from a total of six urban sites across four different municipalities on the island of Puerto Rico. We quantified relative abundance of both species, their habitat use, and the available habitat in the environment to measure both microhabitat preference in an urban setting, as well as niche partitioning between the two different lizards. Overall, we found that the two species utilize different portions of the urban habitat. Anolis stratulus tends to use more “natural” portions of the urban environment (i.e., trees and other cultivated vegetation), whereas A. cristatellus more frequently uses anthropogenic structures. We also found that aspects of habitat discrimination in urban areas mirror a pattern measured in prior studies for forested sites in which A. stratulus was found to perch higher than A. cristatellus and preferred lower temperatures and greater canopy cover. In our study, we found that the multivariate niche space occupied by A. stratulus did not differ from the available niche space in natural portions of the urban environment and in turn represented a subset of the niche space occupied by A. cristatellus. The unique niche space occupied by A. cristatellus corresponds to manmade aspects of the urban environment generally not utilized by A. stratulus. Our results demonstrate that some species are merely tolerant of urbanization while others utilize urban habitats in novel ways. This finding has implications for long-term persistence in urban habitats and suggests that loss of natural habitat elements may lead to nonrandom species extirpations as urbanization intensifies

Divergent habitat use of two urban lizard species

Faunal responses to anthropogenic habitat modification represent an important aspect of global change. In Puerto Rico, two species of arboreal lizard, Anolis cristatellus and A. stratulus, are commonly encountered in urban areas, yet seem to use the urban habitat in different ways. In this study, we quantified differences in habitat use between these two species in an urban setting. For each species, we measured habitat use and preference, and the niche space of each taxon, with respect to manmade features of the urban environment. To measure niche space of these species in an urban environment, we collected data from a total of six urban sites across four different municipalities on the island of Puerto Rico. We quantified relative abundance of both species, their habitat use, and the available habitat in the environment to measure both microhabitat preference in an urban setting, as well as niche partitioning between the two different lizards. Overall, we found that the two species utilize different portions of the urban habitat. Anolis stratulus tends to use more “natural” portions of the urban environment (i.e., trees and other cultivated vegetation), whereas A. cristatellus more frequently uses anthropogenic structures. We also found that aspects of habitat discrimination in urban areas mirror a pattern measured in prior studies for forested sites in which A. stratulus was found to perch higher than A. cristatellus and preferred lower temperatures and greater canopy cover. In our study, we found that the multivariate niche space occupied by A. stratulus did not differ from the available niche space in natural portions of the urban environment and in turn represented a subset of the niche space occupied by A. cristatellus. The unique niche space occupied by A. cristatellus corresponds to manmade aspects of the urban environment generally not utilized by A. stratulus. Our results demonstrate that some species are merely tolerant of urbanization while others utilize urban habitats in novel ways. This finding has implications for long-term persistence in urban habitats and suggests that loss of natural habitat elements may lead to nonrandom species extirpations as urbanization intensifies. © 2017 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd

Winchell_etal_urbanhabitatuse_JEE17

Habitat data from Winchell et al. "Divergent Habitat Use of Two Urban Lizard Species"