Coppard, S.E. & Lessios, H.A. (2017). Phylogeography of the sand dollar genus Encope: implications regarding the Central American Isthmus and rates of molecular evolution. Scientific Reports. 7(1): 11520.
Phylogeography of the sand dollar genus Encope: implications regarding the Central American Isthmus and rates of molecular evolution
Scientific Reports
7(1): 11520
Publication
Vicariant events have been widely used to calibrate rates of molecular evolution, the completion of the
Central American Isthmus more extensively than any other. Recent studies have claimed that rather
than the generally accepted date of ~3 million years ago (Ma), the Isthmus was effectively complete
by the middle Miocene, 13 Ma. We present a fossil calibrated phylogeny of the new world sand dollar
genus Encope, based on one nuclear and four mitochondrial genes, calibrated with fossils at multiple
nodes. Present day distributions of Encope are likely the result of multiple range contractions and
extinction events. Most species are now endemic to a single region, but one widely distributed species
in each ocean is composed of morphotypes previously described as separate species. The most recent
separation between eastern Pacific and Caribbean extant clades occurred at 4.90 Ma, indicating that the
Isthmus of Panama allowed genetic exchange until the Pliocene. The rate of evolution of mitochondrial
genes in Encope has been ten times slower than in the closely related genera Mellita and Lanthonia. This
large difference in rates suggests that splits between eastern Pacific and Caribbean biota, dated on the
assumption of a “universal” mitochondrial DNA clock are not valid.