Land flatworm community structure in a subtropical deciduous forest in Southern Brazil

Due to their biological characteristics and habitat requirements, land planarians have been proposed as indicator taxa in biodiversity and conservation studies. Herein, we investigated spatial patterns of land flatworm communities in the three main existent vegetation types of the most significant remnant of the subtropical deciduous forest in south Brazil. The main questions were: (1) How species-rich is the study area? (2) How are community-structure attributes allocated in areas with distinct floristic composition? (3) What are the effects of soil humidity and soil organic matter content on flatworm abundance? (4) Are there seasonal differences regarding species richness? (5) Are the communities in the three types of vegetation distinct? Twenty-two flatworm species, distributed in five genera and two subfamilies, were recorded. Results indicated that: (1) species richness, evenness, abundance, and dominance in the three vegetation types are not significantly different; (2) diversity indices were higher for areas with caducifolious forest than for areas with jaboticaba trees with marginally significant differences; (3) flatworm abundance is negatively related to soil organic matter; (4) there are no significant differences in flatworm species richness throughout the year; and (5) flatworm communities in the three types of vegetation are not distinct. Soil organic matter content was abundant at sites with distinct vegetation types, thereby negatively affecting flatworm abundance. The original vegetation of the study area has been well-preserved, which may be an explanation for the absence of a clear separation of the flatworm communities of the three main types of vegetation in the study area.