Leonardo David Fernández

We investigate for the first time the species composition and community structure of lobose thecamoebians (Arcellinida) inhabiting an unpopulated and pristine island from the southeastern Pacific. Results revealed low alpha diversity and a high proportion of cosmopolitan species. One genus, four species and two subspecies were identified for the first time for southwestern South America. Further, four morphotypes were not identifi ed to species level, and one could not be identifi ed to species or genera level. They are probably endemics of this poorly studied and remote zone. These results were consistent with the moderate endemicity hypothesis of microbial biogeography. We hypothesized that the low diversity of species recorded on the island is due to selective colonization-extinction dynamics, processes that determines the low species richness of insular macro-organisms. However, this hypothesis needs to be evaluated in the future. Statistical analysis showed that testate amoebae were distributed in two discrete communities in the island. The first consisted of organisms inhabiting habitats located within a forest and the second by organisms inhabiting habitats located outside the forest. The suggested primary factor differentiating these both communities was the availability of appropriate habitat for the different species of testate amoebae.
 

In arid environments, protist diversity is higher in soil covered by vegetation than in bare soil and is also likely to vary in line with the marked seasonal patterns; however, these patterns have not been explored in detail in arid zones. Herein, we used culture – and morphological-based approaches to describe patterns of amoeboid protist diversity in  vegetated and bare soil areas from the intertropical desert of Tehuacán, Mexico, during dry and wet seasons. Overall, 27 protist species belonging to Amoebozoa, Discoba and Rhizaria were retrieved using culture-dependent methods. Among the soil protist groups found, Discoba (principally represented by Heterolobosea) was always the most prevalent taxa. Protist diversity was different between soil with vegetation and bare soil, principally during the dry season. Moreover, the electrical conductivity and pH of the soil were correlated with the protist species during the wet season. Our results support the hypothesis that soil protist diversity patterns exhibit a seasonal variation between dry  and wet seasons. This seasonal variation likely relies on water availability, although the role of other environmental factors cannot be completely ruled out. In addition, the soils with vegetation could be a refuge for the amoeboid protists during the harsh soil conditions of dry seasons.