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Abstract
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.
Highlights
Urbanization is one of the greatest sources of habitat change in the modern era
With a population of 3,725,789 (93.8% of which reside in urban areas; U.S Census Bureau 2012), Puerto Rico’s urban areas include low-density urbanization, midsize cities dominated by suburban communities, and sprawling metropolitan areas with little to no remaining natural habitat and more than a million residents (e.g., Metropolitan San Juan)
We sampled abundance by slowly walking through the habitat for a minimum of 3 hr without retracing our path between 8 a.m. and 7 p.m. Because these species vary in their habitat use throughout the day in natural forest habitats (Hertz, 1992; Nicholson et al, 2005) and in urban habitats (Avilés-Rodríguez unpublished data), surveys were conducted at different times of the day with at least one site surveyed during each daylight hour (Figure 2b)
Summary
Urbanization is one of the greatest sources of habitat change in the modern era. Urban areas occupy a large and expanding fraction of the landscape worldwide and are expected to increase in extent and intensity in coming years (Forman, 2014; United Nations 2012). Other species found in urban habitats have fully embraced their newfound milieu, utilize anthropogenic resources extensively, and may even achieve higher population growth rates and densities in urban areas than at natural sites These species are referred to as “synanthropic,” “urbanophilic,” or “urban exploiters” (Forman, 2014; Grant et al, 2011; McKinney, 2006). With a population of 3,725,789 (93.8% of which reside in urban areas; U.S Census Bureau 2012), Puerto Rico’s urban areas include low-density urbanization (such as rural communities), midsize cities dominated by suburban communities, and sprawling metropolitan areas with little to no remaining natural habitat and more than a million residents (e.g., Metropolitan San Juan) This intense land modification and the pressures associated with human presence have resulted in a decline of many native plant and animal species (Koenig, 1953; Miller & Lugo, 2009). This type of natural history information can aid conservation in urban areas by identifying the minimum habitat requirements of native species and the potential for urban persistence and adaptation
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