Uncommon Ground

The origin of a bipolar moss (i.e., one that occurs in the far North and the far South)

One of the great pleasures of serving as an associate advisor on PhD committee is that sometimes you contribute enough to the analysis and interpretation of the data that you end up being a co-author on a paper. That’s why I have papers on New Zealand cicadas, deer mice, and tapeworms, among other things. Now I’ve added another group to my list – moss. Lily Lewis finished her PhD at UConn in the spring of 2015 working with Bernard Goffinet. I was a member of her committee, and now a chapter of her dissertation on which I was able to help has appeared in the American Journal of Botany.1 Here’s the title and abstract. You’ll find the DOI and a link to the paper below.

Resolving the northern hemisphere source region for the long-distance dispersal event that gave rise to the South American endemic dung moss Tetraplodon fuegianus.

PREMISE OF THE STUDY: American bipolar plant distributions characterize taxa at various taxonomic ranks but are most common in the bryophytes at infraspecific and infrageneric levels. A previous study on the bipolar disjunction in the dung moss genus Tetraplodon found that direct long-distance dispersal from North to South in the Miocene–Pleistocene accounted for the origin of the Southern American endemic Tetraplodon fuegianus, congruent with other molecular studies on bipolar bryophytes. The previous study, however, remained inconclusive regarding a specific northern hemisphere source region for the transequatorial dispersal event that gave rise to T. fuegianus.
METHODS: To estimate spatial genetic structure and phylogeographic relationships within the bipolar lineage of Tetraplodon, which includes T. fuegianus, we analyzed thousands of restriction-site-associated DNA (RADseq) loci and single nucleotide polymorphisms using Bayesian individual assignment and maximum likelihood and coalescent model based phylogenetic approaches.
KEY RESULTS: Northwestern North America is the most likely source of the recent ancestor to T. fuegianus.
CONCLUSIONS: Tetraplodon fuegianus, which marks the southernmost populations in the bipolar lineage of Tetraplodon, arose following a single long-distance dispersal event involving a T. mnioides lineage that is now rare in the northern hemisphere and potentially restricted to the Pacific Northwest of North America. Furthermore, gene flow between sympatric lineages of Tetraplodon mnioides in the northern hemisphere is limited, possibly due to high rates of selfing or reproductive isolation.

DOI: 10.3732/ajb.1700144
1If you’re keeping track, this is my third paper in AJB this year.

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