Ecology of Two Sympatric Species of Neusticurus (Sauria: Gymnophthalmidae) in the Western Amazon of Brazil

Neusticurus ecpleopus is linearly distributed along forest streams, uses stream banks and associated leaf litter, and numerically feeds primarily on fly larvae and ants. The most important prey items volumetrically are crickets and fly larvae. Neusticurus juruazensis occurs in leaf litter of damp low forest but is not directly associated with streams. Fly larvae and collembolans are the most abundant items in the diet but orthopterans, centipedes, and fly larvae are the most important items based on volume. Activity patterns and body temperatures are similar between species, and temperatures of lizards and their microenvironments are higher than average environmental temperatures based on comparisons with null temperature distributions. Morphologically, N. ecpleopus is a more robust species with a relatively longer tail when compared with N. juruazensis. Sexual dimorphism in size and head proportions exists in N. juruazensis but not in N. ecpleopus, at least at our study site. Associations between morphology and habitat use suggest that differences in habitat use explain relatively minor dietary differences and allow coexistence. A comparison of several species and populations of Neusticurus indicates that ecologically there is very little variation among most species. Neusticurus ecpleopus distribui-se linearmente ao longo de riachos na mata, utiliza as margens dos riachos e o folhiCo associado, e alimenta primariamente, em termos numericos, de larvas de moscas e formigas. Em termos volumetricos, os itens predados mais importantes sio gafanhotos e larvas de moscas. Neusticurus juruazensis ocurre no folhipo da mata baixa e encharcada, mas nio esti diretamente associado a riachos. Larvas de moscas e colembolas sio os itens mais abundantes na dieta, mas ort6pteros, centropeias e larvas de moscas sio os itens mais importantes em termos de volume. Os padrtes de atividade e as temperaturas corporais sio semelhantes entre as duas especies. As temperaturas dos lagartos e de seus microambientes sio mais altas do que a media das temperaturas ambientais baseadas em comparap6es com distribup6es nulas de temperaturas. Morfologicamente, N. ecpleopus e uma especies mais robusta e com cauda relativamente mais longa do que N. juruazensis. Diformismo sexual quanto ao tamanho e quanto as proporytes da cabeca ocurrem em N. juruazensis, mas nio em N. ecpleopus, pelo menos em nossa Area de estudo. Associap6es entre morfologia e uso de habitat sugerem que diferencas no uso do habitat explicam pequenas diferenCas na dieta e permitem a coexistencia das duas especies. Uma comparaCio entre diversas especies e populap6es de Neusticurus indica que existe pouca variap o, ecologicamente entre as especies.