Carpenter, Kevin J.

Calonymphids are a group of multinucleate, multiflagellate protists belonging to the order Cristamonadida (Parabasalia) that are found exclusively in the hindgut of termites from the family Kalotermitidae. Despite their impressive morphological complexity and diversity, few species have been formally described and fewer still have been characterized at the molecular level. In this study, four novel species of calonymphids were isolated and characterized: Calonympha chia and Snyderella yamini spp. nov., from Neotermes castaneus and Calcaritermes nearcticus from Florida, USA, and Snyderella kirbyi and Snyderella swezyae, spp. nov., from Calcaritermes nigriceps and Cryptotermes cylindroceps from Colombia. Each of these species was distinguished from its congeners by residing in a distinct host and by differences at the molecular level. Phylogenetic analyses of small subunit (SSU) rDNA indicated that the genera Calonympha and Stephanonympha were probably not monophyletic, though the genus Snyderella, previously only represented by one sequence in molecular analyses, appeared with these new data to be monophyletic. This was in keeping with the traditional evolutionary view of the group in which the morphology of the genus Snyderella is considered to be derived, while that of the genus Stephanonympha is ancestral and therefore probably plesiomorphic.

The inadequacy of morphology for species and genus delineation in microbial eukaryotes

Digital Document

Background For the majority of microbial eukaryotes (protists, algae), there is no clearly superior species concept that is consistently applied. In the absence of a practical biological species concept, most species and genus level delineations have historically been based on morphology, which may lead to an underestimate of the diversity of microbial eukaryotes. Indeed, a growing body of molecular evidence, such as barcoding surveys, is beginning to support the conclusion that significant cryptic species diversity exists. This underestimate of diversity appears to be due to a combination of using morphology as the sole basis for assessing diversity and our inability to culture the vast majority of microbial life. Here we have used molecular markers to assess the species delineations in two related but morphologically distinct genera of uncultivated symbionts found in the hindgut of termites. Methodology/Principal Findings Using single-cell isolation and environmental PCR, we have used a barcoding approach to characterize the diversity of Coronympha and Metacoronympha symbionts in four species of Incisitermes termites, which were also examined using scanning electron microscopy and light microcopy. Despite the fact that these genera are significantly different in morphological complexity and structural organisation, we find they are two life history stages of the same species. At the same time, we show that the symbionts from different termite hosts show an equal or greater level of sequence diversity than do the hosts, despite the fact that the symbionts are all classified as one species. Conclusion/Significance The morphological information used to describe the diversity of these microbial symbionts is misleading at both the genus and species levels, and led to an underestimate of species level diversity as well as an overestimate of genus level diversity. The genus ‘Metacoronympha’ is invalid and appears to be a life history stage of <i>Coronympha</i>, while the single recognized species of <i>Coronympha octonaria,</i> inhabiting these four termites is better described as four distinct species.

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