Quantifying earthworm species richness in the pineapple and mixed fruit plantations of West Tripura, India - A non-parametric approach

Species richness is a fundamental measurement of community and regional diversity. In spite of its importance, ecologists have not always appreciated the effects of sampling efforts and abundance on richness measures and comparisons. The species richness, abundance of earthworms were investigated in the pineapple (PP) and mixed fruit plantations (MFP) of West Tripura, India. A total of 11 and 14 earthworm species belonging to 8 genera of 4 families were collected by conventional digging and hand sorting method from PP and MFP respectively. A comparative analysis of inventory completeness and species richness among the two types of plantations was done by using species accumulation curves and other non-parametric richness estimators. Species accumulation curves revealed more completeness of the inventory in MFP than that of PP. We use six different estimators based on abundance data: Chao 1, Chao 2, ACE, ICE, Jack-knife 1 and Jack-knife 2. For MFP, all the estimators except Jack-knife 2, showed accurate prediction of species richness; whereas only Chao 1 and Chao 2 estimators perform particularly well in case of PP.