Tropical spiders have been poorly studied, and studies regarding the distribution of genetic diversity in natural populations of these species are even more scarce. Among the spider genera, the South American genus Aglaoctenus includes species that build tube-shaped webs and display subsocial behavior that includes parental care. Herein we studied the population genetics of Aglaoctenus lagotis in five primary fragments of the Brazilian Atlantic Forest (with varying distances between 2 and 47 km) considered a conservation hotspot. In this study, we used two molecular markers: microsatellites and the COI mitochondrial gene. The data obtained indicated the presence of two genetic lineages (A and B), as evidenced by both markers, suggesting the presence of cryptic diversity. Lineages subpopulations are not completely isolated and have moderate structure (FST A=0.118; FST B= 0.142). Dispersal by air (or ballooning) must occur and possibly allows the maintenance of gene flow between sample sites. The hypotheses that lineages found here represent distinct species cannot be confirmed until further studies have been carried out. However, regardless of its taxonomic classification, the genetic lineages, found here, should be considered as individual units in future evolutionary studies of this species.
Key words: conservation, population genetics, fragmentation, spider