Abstract
Persistence of animals in urban habitats, a stark environmental contrast to natural habitats, can be explained through evaluating the mechanisms behind organism-habitat interactions. One of the most notable effects of urbanization is the change in structural habitat; vegetation is removed and modified, favoring large trees and adding artificial structures in cities, which may alter how organismal preferences for aspects of the habitat are realized. We evaluated the mechanisms by which structural habitat changes associated with urbanization alter the available vegetation and substrates on which two species of Anolis lizards perch in urban and natural forest sites in Miami, FL. We also experimentally assessed habitat preference in the lab to establish the mechanism behind habitat selection. We found that vegetation was broader in urban areas compared to natural habitats, and artificial structures in urban areas were more than twice the diameter of available natural perches. Lizards expressed their preference for broad perches by selecting broader vegetation and artificial structures compared to their availability in both habitats. With the increased availability of broad substrates in urban areas, perch diameters selected by lizards resulted in an expansion of this aspect of the structural habitat niche for both species. The two species differed, however, in other responses to altered urban habitats. Anolis cristatellus tended to avoid artificial substrates, whereas A. sagrei used both natural and artificial structures in proportion to their availabilities. This study provides a mechanistic explanation for how urbanization alters structural habitats, leading to niche expansion for organisms living in cities.
Highlights
Most species alive today have an evolutionary history that includes persisting through environmental changes and encountering novel habitats to some degree (Thompson, 2013).ongoing human-induced rapid environmental change (HIREC) is unprecedented in both its rate and magnitude of environmental change on this planet (Palumbi, 2001; Hobbs et al., 2006; Sih et al, 2011; Barnosky et al, 2012)
We found that lizard habitat preferences interact with habitat availability to drive the expansion of the structural habitat niche of anoles in urban areas (Fig. 4)
Other studies have observed expansion of the realized niche in response to HIREC, in the context of invasive species responding to novel climates in their non-native range (Holt et al, 2005; Broennimann et al, 2007; Fitzpatrick et al, 2007; Pearman et al, 2008; Tingley et al, 2014), but observations of niche expansion in urban environments are limited
Summary
Most species alive today have an evolutionary history that includes persisting through environmental changes and encountering novel habitats to some degree (Thompson, 2013).ongoing human-induced rapid environmental change (HIREC) is unprecedented in both its rate and magnitude of environmental change on this planet (Palumbi, 2001; Hobbs et al., 2006; Sih et al, 2011; Barnosky et al, 2012). To better understand how changing environmental conditions challenge the persistence of populations, we need mechanistic studies that quantify changes in niche dimensions due to global change (Shochat et al 2006; Sol et al.2013). Such studies should evaluate changes in resource availability in altered habitats, how organisms respond through their resource use and preferences, and if individuals experience any fitness consequences. This niche-based assessment should yield valuable insight into the role of niche dynamics (e.g. niche contraction or niche expansion) in determining whether populations persist under HIREC (Wingfield et al, 2011)
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