Amoebae or finches? Walking in the footsteps of Darwin, but looking under our feet!

Background/Question/Methods

Species functional trait (FT) research provides new insights into the links between community structure and ecosystem function providing a key tool for ecologist. A strength of trait-based measurements of functional diversity (FD) lies in the ability to study groups of taxa, such as minute soil taxa including testate amoebae (TA), for which species-level identification is difficult or impossible. In this study we analyzed species composition and functional traits of differing TA communities throughout the humid highlands of Santa Cruz, Galápagos. We examined possible links between TA species traits and environmental variables including substrate types, site habitat, and relative topographic position. We calculated classical diversity indices including, species richness, diversity, evenness, and density along with functional indices including functional richness (FRic), divergence (FDiv), evenness (FEve), and dispersion (FDis), to detect any changes in community structure and functioning. Multivariate statistics were used to identify and summarize major patterns in the TA communities while ‘Fourth Corner’ statistics were utilized to assess relationships between species traits and environmental variables.

Results/Conclusions

The analysis shows that total of 54 TA species were identified and TA functional dispersion and functional divergence differed between site topography and substrate types. Positive relationships between elevation and testate amoeba shell material and biovolume of the amoebae were detected while negative relations between two additional variables, pseudopod type and aperture placement, and elevation are also detected. Analysis of species traits indicated relatively high niche differentiation, moderate to low competition and more widely dispersed traits detected in the TA communities located in Sphagnum substrates and closed basin habitats. Additionally, TA communities within the open and intermediate sites and highly disturbed trail sites were indicted to have experienced higher levels of competition for more limited resources.