Padrões de distribuição espacial de Opiliões (Arachnida: opiliones) em uma área de floresta de terra firme na Amazônia Central

Abstract

The harvestmen are the fourth class in diversity of Arachnida, composed by 6,490 species described in the world. Its more abundant in tropical regions, especially in the Neotropics. For the Amazon, a region worldwide recognized for its high biodiversity, this order is still taxonomically and systematically, as well as ecologically poorly, understood. This study aimed to inventory this group at the Experimental Farm of Federal University of Amazonas, north of Manaus city (AM), as well as to investigate the spatial distribution patterns of the harvestmen community in an area of dryland forest. A total of 1,115 individuals were collected, which 52 were juvenils and did not allowed their correct identification. A total of 28 species, 12 families and 13 genera were identified so far. Among the species, only eight are known, and the others represent up to 71% of new records. Only Cosmetidae and Sclerosomatidae represented more than 68% of the total collected individuals, being the most abundant and widely distributed. Regarding the environmental gradients, there was no high rate of substitution of the species in the scale investigated; however, it was found that each method used in the collection showed different assemblies of harvestmen, which evidences the importance of microhabitats in the distribution patterns of these species. The species accumulation curve and assemblage composition analysis showed that the technique of nocturnal active search is able to satisfactorily sample the community of harvestmen, suggesting that in situations where time or financial resources are limiting factors, this methodology is used in order to optimize them with satisfactory results. This mesoscale work allowed to observe that microhabitat conditions interfere more in the spatial distribution of harvestmen than environmental gradients. It is therefore proposed that new specific collection protocols should be tested for the group in order to optimize time in field and cost of research, still scarce in the region.