Long-term effects of anthropogenic habitat disturbance on a lizard assemblage inhabiting coastal dunes in Argentina Laura E. Vega, Patricio J. Bellagamba, and Lee A. Fitzgerald Abstract: We studied abundance and habitat use in two species of Liolaemus (Squamata: Tropiduridae) at a coastal dune site in eastern Argentina before and 7 years after a road was built at the site. Before disturbance, lizards exhib- ited similar abundances and a wide segregation in microhabitat use. Liolaemus multimaculatus used flat dunes scarcely covered by Spartina ciliata, while Liolaemus gracilis used the grass Panicum racemosum as cover. After disturbance, the mean number of L. multimaculatus detected by month was significantly less than that observed in the predisturbance period, owing to a drastic reduction in S. ciliata microhabitat patches. The mean number of L. gracilis was similar to that seen during the first period. These differences were clearly linked to habitat loss at the site. We concluded that human impact on the habitat structure of foredunes induced changes in the structure of the lizard assemblage, including shifts in the relative abundance of species and the proportional use of their preferred microhabitats. Résumé : Nous avons étudié l’abondance et l’utilisation de l’habitat chez deux espèces de Liolaemus (Squamata : Tro- piduridae) sur le site d’une dune côtière de l’est de l’Argentine, avant et 7 ans après la construction d’une route à cet endroit. Avant la perturbation, les lézards des deux espèces étaient tout aussi abondants et il y avait ségrégation des deux dans différents microhabitats. Liolaemus multimaculatus utilisait les dunes plates à peine couvertes de Spartina ci- liata, alors que Liolaemus gracilis utilisait les zones couvertes de plantes herbacées Panicum racemosum. Après la per- turbation, le nombre moyen de L. multimaculatus repérés chaque mois était significativement moins élevé qu’avant la perturbation à cause de la réduction considérable des microhabitats à S. ciliata. Le nombre moyen de L. gracilis a peu changé après la perturbation. Ces différences sont directement attribuables à la perte d’habitat sur le site. Nous con- cluons que l’impact de la perturbation d’origine humaine sur la structure de l’habitat des avant-dunes a entraîné des modifications des associations de lézards, notamment des changements dans l’abondance relative des espèces et dans l’utilisation proportionnelle des habitats préférés. [Traduit par la Rédaction] 1660 Vega et al. Introduction Human activities along the northern Atlantic coast of Ar- gentina have led to an increase in coastal erosion (Isla and Villar 1992). The major causes of “anthropogenic erosion” are urban development (Bertola et al. 1999), inadequate beach management (Isla et al. 1994), and sand mining (Farenga et al. 1992; Isla 1992). The pressure of urban development, specifically the building of roads and houses within 150 m of the high-tide mark, leads to the abrupt eradication of dunes or sets up barriers that alter the dynamic sand ex- change. Inevitably, the dunes slowly waste away (Echeverría 1987; F.I. Isla and M.C. Villar 2 ). Urban pressure, along with the cultivation of exotic plants to stabilize the dunes and the establishment of tourist facilities on the coast of Buenos Aires Province, Argentina, have led to a continuous process of habitat loss and fragmentation. This pattern has been re- peated in many other coastal areas of the world (Sorensen et al. 1992). The ecological consequences of coastal dune degradation for small vertebrates, particularly ecological interactions among arenicolous lizards, are generally unknown. Two studies have reported effects of coastal habitat alteration on the herpeto- fauna in South America. Gudynas (1989) described the as- semblage of reptiles and amphibians in an altered site, and Rocha and Bergallo (1992) found that a gradual reduction in beach vegetation over 10 years was accompanied by a de- cline in the population of Liolaemus lutzae in southeastern Brazil. Dune lizard assemblages in Buenos Aires Province contain up to four species, one of which is endemic to coastal dunes. Previous work (Vega 1994) showed that these species differ in their preference for structural microhabitat charac- teristics and in exhibiting a high degree of spatial segrega- tion in sympatry. Studies on the effects of habitat disturbance on reptiles in Argentina are lacking, as are studies in which a before-and- Can. J. Zool. 78: 1653–1660 (2000) © 2000 NRC Canada 1653 Received November 11, 1999. Accepted April 28, 2000. L.E. Vega. Facultad de Ciencias Exactas y Naturales, Departamento de Biología, Universidad Nacional de Mar del Plata, Funes 3250, 7600 Mar del Plata, Argentina. P.J. Bellagamba. Subsecretaría de Medio Ambiente, Municipalidad de General Pueyrredón, La Rioja 1650, 7600 Mar del Plata, Argentina. L.A. Fitzgerald. 1 Department of Wildlife and Fisheries Sciences, Texas Cooperative Wildlife Collection, Texas A&M University, College Station, TX 77843-2258, USA. 1 Author to whom all correspondence should be addressed (e-mail: lfitzgerald@tamu.edu). 2 Isla, F.I., and Villar, M.C. 1992. Ambiente costero : Pacto Ecológico. Informe inédito del convenio Universidad Nacional Mar del Plata—Cámara de Diputados de la Provincia de Buenos Aires, Argentina, unpublished report.