Our understanding of many biological aspects of early placental mammals is still very limited. Due to the paucity of the fossil record, attention is often turned to those extant organisms that share plesiomorphic characters in order to gain insights into the evolutionary history of mammals. Afrotheria is one of the four major clades of placental mammals, accounting for around a third of all mammalian orders, and encompasses a wide array of differently adapted species. Within Afrotheria, tenrecs are a more species-rich group of small mammals native to the island of Madagascar that display several special traits resembling those hypothesized on early placentals regarding reproductive strategies, thermoregulation and growth metabolism. Despite this, tenrecs remain heavily understudied in many aspects. Genomic information for this group of mammals is scarce and not up to modern quality standards. We present here the complete, chromosome-scale reference genome and annotation of the common tenrec, Tenrec ecaudatus. To put this new resource to use, we conducted a phylogenetic reconstruction and divergence time estimation for Afrotheria using all the available genomic resources for afrotherian mammals. This analysis recovered the phylogenetic order containing hyraxes as a sister group to elephants and a younger molecular divergence of tenrecs than previously estimated. Added to this, our comparative chromosome-synteny analyses showed significant rearrangements within afrotherians, especially on the clade shared by tenrecs, elephant-shews and the aardvark (Afroinsectiphilia). This newly produced high-quality genome assembly proves to be a valuable resource to complement our genomic understanding of Afrotheria, allowing for insights into chromosome evolution, time of molecular divergence and phylogenetic reconstruction. This establishes a basis for further studies to utilize this resource to further pursue evolutionary questions regarding tenrecs adaptations and comparative analyses within Afrotheria.
Hernández-Roco et al. (Tue,) studied this question.