ECOLOGY & EVOLUTION

Diversity Ad Infinitum

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Science  11 Aug 2000:
Vol. 289, Issue 5481, pp. 833
DOI: 10.1126/science.289.5481.833c

Microorganisms remain one of the thornier sectors in the quest to quantify the number of living species. Morphological species delimitation, which is not always straightforward at the macroscopic level, becomes quixotic where bacteria, fungi, and protozoa are concerned. Among the fungi, estimates of global species diversity have reached as high as 1.5 million, or six times as many species as the higher plants.

Endophytes are fungi that are ubiquitous in plants, inhabiting root, stem, and leaf tissues in harmless commensal association. Several recent studies have suggested that endophytes might comprise a substantial component of fungal diversity. Arnold et al. find 418 morphospecies (estimated to account for about 350 genetically distinct species) of endophyte growing at low abundance within just two tree species in two Central American rain forest sites. After a larger fraction of the tropical forest flora has been sampled, and taking into account data on host preference and spatial variability within hosts and between sites, the fungi may grow to rival the arthropods as one of the most speciose groups on Earth. — AMS

Ecol. Lett. 3, 267 (2000).

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