Saturday, June 13, 2020

Collagen sequence reveals evolutionary history of extinct 'island-shrews' - Nesophontes

With great satisfaction, I announce the publication of our paper on the extinct Greater Antillean endemic: Nesophontes. As you may have read from posts in this blog, the genus Nesophontes is a group of shrew-like mammals for which several species have been identified on the islands of Cuba, Cayman, Hispaniola, and Puerto Rico, but not The Bahamas or Jamaica. Each island had its own exclusive forms. These unique varieties to each island are called endemics. 

Original specimen from which Nesophontes was described: N. edithae (AMNH 14174). 

The genus Nesophontes is grouped within the mammal order Eulipotyphla. This is a group of basal placental mammals that are considered ancestrally associated to the Solenodon of Cuba and Hispaniola. Also, to other North American extinct shrew-like micromammals, but surprisingly not to the African tenrecs despite their physical similarity.  Nesophontes was small, likely venomous, nocturnal, and could tunnel underground. At least eight species are currently recognized: three in Cuba (N. major, N. micrus and N. longirostris); three in Hispaniola (N. paramicrus, N. hypomicrus, and N. zamicrus); one in Puerto Rico (N. edithae) and one in Cayman (N. hemicingulus). However, the identification, naming, and evolutionary history of this diverse group has been somewhat controversial. 

Solenodon paradoxus from Hispaniola. Plate from Allen's (1910) monograph on the species. 

We designed our study to help unravel especially the issue of evolution and species limits. Our paper, formally accepted in the journal Molecular Biology and Evolution this past march, provides the following abstract: 

“Ancient biomolecule analyses are proving increasingly useful in the study of evolutionary patterns, including extinct organisms. Proteomic sequencing techniques complement genomic approaches, having the potential to examine lineages further back in time than achievable using ancient DNA, given the less stringent preservation requirements. In this study, we demonstrate the ability to use collagen sequence analyses via proteomics to provide species delimitation as a foundation for informing evolutionary patterns. We uncover biogeographic information of an enigmatic and recently extinct lineage of Nesophontes across their range on the Caribbean islands. First, evolutionary relationships reconstructed from collagen sequences reaffirm the affinity of Nesophontes and Solenodon as sister taxa within Solenodonota. This relationship helps lay the foundation for testing geographical isolation hypotheses across islands within the Greater Antilles, including movement from Cuba towards Hispaniola. Second, our results are consistent with Cuba having just two species of Nesophontes (N. micrus and N. major) that exhibit intrapopulation morphological variation. Finally, analysis of the recently described species from the Cayman Islands (N. hemicingulus) indicates that it is a closer relative to the Cuban species, N. major rather than N. micrus as previously speculated. Our proteomic sequencing improves our understanding of the origin, evolution, and distribution of this extinct mammal lineage, particularly with respect to approximate timing of speciation. Such knowledge is vital for this biodiversity hotspot, where the magnitude of recent extinctions may obscure true estimates of species richness in the past.”

I take this opportunity to extend my gratitude and thanks to the whole team, for pushing through with persistence for nearly a decade. And to all the friends and colleagues that helped along the way. 

Stay tuned for more details on our findings and these peculiar mammals ahead. 

Recommended Citation

Buckley, Mike; Virginia L. Harvey; Joha Orihuela; Alexis M. Mychajliw; J. Keating; J. N. Almonte Milan; C. Lawless; A. T. Chamberlain; V. M. Egerton; and Phillip L. Manning (2020). Collagen sequence analysis reveals evolutionary history of extinct West Indies Nesophontes ('island-shrews'). Molecular Biology and Evolution:

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