How many lineages are there of the stingrays' genus Hypanus (Myliobatiformes, Dasyatidae) and why does it matter?

PETEAN, FLÁVIA F.; YANG, LEI; CORRIGAN, SHANNON; NAYLOR, GAVIN J.P.; LIMA, SERGIO M. Q.

Congreso; II Congreso Latinoamericano de Genética para la Conservación; 2021

Sociedade Brasileira de Genética, Red Latinoamericana de Genética para la Conservación

Hypanus stingrays currently encompass nine valid species from the Atlantic and Pacific oceans, though the phylogenetic relationships amongst some of them were based on a single mitochondrial gene and did not involve all putative Hypanus species. To address the monophyly of the genus and its relationship to other Dasyatinae genera, we sequenced the whole mitochondrial genomes of all valid species, adding up to 135 specimens. Hypanus is the sister-genus to all other Dasyatinae, and this subfamily is closely-related to Neotrygoninae within the family Dasyatidae. The species Fontitrygon geijskesi is closely related to H. guttatus rather than to other Fontitrygon species, therefore should be allocated to Hypanus as H. geijskesi for the genus to be monophyletic. There are two species-complex composed by H. guttatus and H. say, with two distinct evolutionary lineages within each, besides the already known H. americanus species complex with also two lineages. Hypanus marianae was proven to be indeed a Hypanus species. The discovery of new lineages leaves the genus with 14 evolutionary units, of which only H. sabinus is clearly under low threatened risk by IUCN criteria while currently six valid species are under threat. With the identification of new lineages within known species, an immediate consequence is the reduction of their extension of occurrence, which is a criterion for evaluating a taxon as threatened. Besides, the description of new taxa allows studies on their populational growth and movement during the following generations, which also meet another IUCN criterion, such as population size reduction, as it was seen in H. berthalutzae. Its description followed the recognition of H. americanus, a data deficient species, as a paraphyletic taxon with an independent evolutionary unit at its southern distribution. With taxonomic issues solved, both could be evaluated: H. americanus is now near threatened and H. berthalutzae vulnerable. Therefore, this case of a recently discovered species being already under threat suggests an urgency in evolutionary and taxonomic evaluations of these stingrays since there might be unknown units already facing some threat.