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Nematode Diversity in a Tropical Rainforest

Hypothesis: That most of the nematode diversity in the tropical rainforest is found in arboreal habitats and the associated invertebrates, as compared with the concentration of biodiversity found in temperate grassland soils. (NSF Biodiversty Surveys and Inventories #0450537)

Testing: We conducted a survey of nematode diversity in the humid lowland tropical rainforest of Costa Rica. Samples of soil, forest floor litter and understory habitats (insects and epiphytes) were collected from the La Selva Biological Station, Costa Rica. All nematode taxa were identified morphologically, with some unusual or unique phenotypes characterized by molecular metrics. Molecular Operational Taxonomic Units (MOTU's) determined by amplification of barcode region and sequence assessment.

Research methods- Sampling protocols

Specimen photographs

Publications resulting from this study

The research team

Results of the Nematode Survey:

Molecular analysis (measured by SSU ribosomal diagnostic region using single-nematode PCR and sequencing) of 360 nematodes (120 per each habitat) revealed 167 distinct MOTUs, only 6 of which identically matched the GenBank entries. Estimated total “species” richness ranged from 464 to 502 and sampling efficiency curves indicated that only 22-30% of the nematode species have been recovered from the soil, litter, and understory habitats. As much as 62% of the genetic diversity existed in litter and understory habitats and was not recovered from soil samples, indicating that previous estimates of tropical nematode diversity were low because habitats above the mineral soil were not included in sampling designs.

360 nematodes were processed, 120 from each habitat: soil, litter and understory
Of the 360 sequences, 167 unique sequences were recovered
Each habitat has a large proportion of unique sequences: 55 taxa were only recovered from the soil, 52 taxa were only recovered from the litter, and 38 taxa were only observed from the understory

For more specific results, see
Nematode Survey