Lizard species distributions and habitat occupation along an urban gradient in Tucson, Arizona, USA

Despite expanding human populations in metropolitan areas world-wide, habitat relationships of lizards have seldom been examined along urban gradients. We tested three hypotheses addressing lizard species distributions, site occupation, and assemblage organization along the urban gradient in Tucson, Arizona, USA. One hundred twenty-nine random sampling plots were distributed from undisturbed-natural land beyond the boundary of development to highly developed land within the city. We recorded lizard species abundances and 19 variables describing habitat physiognomy, floristics, and spatial relationships of native remnant and developed land parcels in each plot. We ordinated lizard species and habitat data in a canonical correspondence analysis, and tested significance of relationships in a Monte Carlo randomization test. We then tested effects of individual habitat features on site occupation by lizards using a presence-absence transformation of lizard abundance data and multiple logistic regression. Both species distributions and site occupation were influenced by factors describing habitat physiognomy, floristics, and landscape spatial relationships. Finally, we examined total abundance, number of species, and evenness across five categories describing increasing residential density. All three measures of assemblage organization peaked at low-moderate levels of development, and declined markedly as residential density increased beyond moderate levels. Distinct attributes of urban development influence lizard species distributions, site occupation, and assemblage organization. Attention to these attributes will allow land developers to mitigate the effects of future urban development on lizard populations. (C) 2000 Elsevier Science Ltd. All rights reserved.