Community structure of lizards in coastal sand dunes: a review of key resources use at local and regional scale

Abstract

Our current understanding of the communities and taxonomic assemblages has, in recent years, integrated processes at different spatial scales. Four species of closely-related Iguanian lizards coexist along the length of the pampean coastal sand dunes of Argentina in assemblages with different combinations that vary from two to four species, according to the locality. Our work examines community organization and species coexistence of these assemblages at two scales; at the local scale, we review and compare the use of biotic and abiotic resources by sand-dwelling lizards of two assemblages of the Southern Dune Barrier focusing on the space, time and food niche dimensions of the species. At regional scale, we examine habitat selection of the most recurrent and spread sand lizards along the whole eastern barriers. Sampling included counts of individuals in random walks searching for habitat and microhabitat occupation, registration of environmental variables (i.e. substrate and air temperatures; dominant, height and cover of vegetation, and substrate composition), temporal daily activity and foraging habits of lizards. At regional scale, we evaluate the relationships between lizards`presence/absence and the percentage of associated coverage of the main groups of plants and bare sand. Results show that the wide spatial (habitat and microhabitat) segregation at local sites, associated to species traits, is meaningful relative to species coexistence, whereas the outcomes in the food and time niche dimensions are less explicative. At regional scale, the opposite distribution between the Sand Lizard (Liolaemus multimaculatus) in active dunes with higher coverage of clump herbs and bare sand, and the Wiegmann´s Lizard (Liolaemus wiegmannii) mainly in semi-fixed dunes whith higher coverage of shrubs and sub-shrubs, is also a common pattern that leads to coexistence at regional scale. In coastal sand dunes, the influence of salt spray, temperature and sand movement creates an environmental gradient from coast to inland, which seems to primarily control community organization, as in other places of the world. In Argentina, lizards of the eastern coastal sand dunes of Buenos Aires segregate in different structural habitats and microhabitats of this environmental gradient, sustaining the structure of these lizard assemblages and arising as a trade-off for species´ coexistence at two spatial scales.