Diversity and distribution of earthworms in the pineapple (Ananus comosus) plantations of West Tripura

Earthworms account for their highest biomass among tropical soil macro-fauna and also called “Ecosystem engineers” because of their role in soil physical structure and organic matter dynamics, ecosystem function, biodiversity conservation and restoration of degraded soil. Pineapple, native to Southern Brazil and Paraguay, is widely cultivated in Tripura. Most of the pineapple plantations in Tripura derived either from waste or fallows over hill slopes, hillocks and plains. An individual tree species can effect earthworm biomass and density significantly by altering physico-chemical properties of soil

1. Diversity and distribution of earthworms in the pineapple ( Ananus comosus ) plantations of West Tripura Animesh Dey & P.S. Chaudhuri * Earthworm Research Laboratory, Department of Zoology, Tripura University, Suryamaninagar – 799022

2. Introduction Earthworms account for their highest biomass among tropical soil macro-fauna and also called “Ecosystem engineers” because of their role in soil physical structure and organic matter dynamics, ecosystem function, biodiversity conservation and restoration of degraded soil. Pineapple , native to Southern Brazil and Paraguay, is widely cultivated in Tripura. Most of the pineapple plantations in Tripura derived either from waste or fallows over hill slopes, hillocks and plains. An individual tree species can effect earthworm biomass and density significantly by altering physico-chemical properties of soil.

3. Objectives To determine the following regarding earthworm community of pineapple plantations: Species composition and community organization earthworms in pineapple plantations. Sampling optimization and non-parametric estimation of species richness of earthworm community in pineapple plantation. Spatio -temporal patterns of earthworm community in pineapple plantation. Impact of soil properties on earthworm community structure.

4. Materials & methods Study sites: Pineapple plantations of West Tripura. Collection: Digging (25 cm × 25 cm × 40 cm) and hand sorting method during 2008-2011. Application of sample based rarefaction curves to optimize sample size. Application of incidence and abundance based non-parametric richness estimators . Application of Probability density function (PDF ) & dispersion indices for determining horizontal distribution. Multivariate analysis (PCA) to find out the relationship between soil physico-chemical parameters and earthworm density.

5. Sampling sites

6. Results Earthworms of the pineapple plantations of West Tripura Drawida assamensis Gates Eudominant earthworm species of pineapple plantation

7. Metaphire houlleti Metaphire posthuma Kanchuria sp.1 Kanchuria Sumerianus Eutyphoeus gigas Eutyphoeus scutarius

8. E. comillahnus Eutyphoeus sp.1 Eutyphoeus gammiei Drawida p. papillifer Drawida nepalensis Pontoscolex corethrurus

9. Earthworms and family Categories Biomass (gm 2 ) Density (Ind.m 2 ) RA (%) Frequency (%) Megascolecidae M. houlleti * M. Posthuma * Kanchuria sp 1 K. Sumerianus Moniligastridae D. assamensis D. p. papillifer D. Nepalensis Epianecic Endogeic Endogeic Endogeic Endogeic Epianecic Endogeic 1.09 0.06 0.32 0.05 27.29 1.33 0.25 3.68 0.16 0.64 0.05 115.52 4.32 0.64 2.52 0.12 0.49 0.03 81.23 2.99 0.46 14.72 0.56 2.78 0.28 96.94 17.78 1.67 Table 1: Ecological categories, biomass, density, relative abundance and frequency of earthworms in the pineapple plantations * Exotic species, RA – Relative abundance Cont..

10. Earthworms and family Categories Biomass (gm 2 ) Density (Ind. m 2 ) RA (%) Frequency (%) Octochaetidae E. gigas E. scutarius E. comillahnus Eutyphoeus sp1 E. gammiei   Glossoscolecidae P. corethrurus * Endoanecic Endogeic Endogeic Endogeic Endoanecic Endogeic 0.72 0.10 0.27 0.09 0.01 5.61 0.48 0.09 0.40 0.16 0.05 16.16 0.37 0.06 0.28 0.12 0.03 11.39 2.78 0.56 1.94 1.11 0.28 72.22 Table 1 cont… * Exotic species, RA – Relative abundance

11. Fig 1 Showing sample based rarefaction curve generated from the complete sampling revealed the observed species richness

12. A B Fig 2 Showing (A) abundance based and (B) incidence based richness estimators extrapolating the undiscovered species richness

13. Estimators Observed richness (S obs ) Estimated richness (Est.) Estimation percent (%) Chao 1 13 13.25 98 ACE 13 14.49 90 Jackknife 1 13 14.98 87 Chao 2 13 13.17 99 ICE 13 14.06 92 Jackknife 2 13 12.07 - Michaelis-Menten 13 12.02 - Bootstrap 13 14.46 90 Table 2 Showing the observed earthworm species richness and estimated richness of earthworm species and percentage of estimation in the pineapple plantations

14. Fig 3 Probability density function (PDF) and different clumping parameters (Dispersion index, Morisita’s index and NB parameter) showing the patchy horizon tal distribution and the degree of patchiness of earthworm communities in the studied sites.

15. Depth (cm) Earthworm species 0-10 cm 10-20 cm 20-30 cm 30-40 cm M. houlleti M. posthuma Kanchuria sp K. sumerianus E. gigas E. scutarius E. comillahnus Eutyphoeus sp E. gammiei D. assamensis D. papillifer papillifer D. nepalensis P. corethrurus + + + - + + + - - + + + + - - + + + + + + + + + + + - - - - + + + + + + - + + - - - - + - - - + - - - - Table 3 Showing the vertical distribution of different earthworm species in the pineapple plantation

16. Fig 4 Showing the variation in overall earthworm density with soil depth (left) and impact of seasonality on vertical distribution of earthworms (right) in the pineapple plantations

17. Fig 5 Showing (A) multivariate analysis (PCA) and (B) its scores to show the impact of soil parameters on earthworm density A B

18. Major findings Thirteen species belonging to four families were identified from the pineapple plantation of west Tripura . Among the thirteen species of earthworms, three species were exotic, where as the rest endemic to the subcontinent . Endogeic ( geophagus ) earthworms were the dominant functional group in pineapple plantations. Drawida assamensis was the dominant species of pineapple plantation in respect to its density, biomass and relative abundance . Incidence based Chao2 estimator was found to be best suited for the non-parametric estimation of earthworm species richness.

19. Major findings Highly clumped horizontal distribution pattern was observed in the earthworm communities of pineapple plantations. As far as the vertical distribution is concerned, upper 10 cm soil layer was mostly exploited by earthworms. Vertical distribution was greatly influenced by seasonality. Monsoon and post monsoon were the major period of worm activity. Soil temperature and moisture were identified as most potent regulatory factors among the four soil parameters .

20. THANK YOU