Thursday, February 25, 2021

[Ichthyology • 2021] Phylogenetic Relationships, Genetic Diversity and Biogeography of Menhadens, Genus Brevoortia (Clupeiformes, Clupeidae)

in Pozzobon, Gonçalves, Anderson, .. et Dario, 2021.
upper photo by Brian Gratwicke

• First phylogenetic study including all six currently valid species of Brevoortia.
• The genus is monophyletic and species are grouped as pairs in three major clades.
 • Divergence times were estimated and a biogeographic scenario is proposed.
• Gene flow occurs between different species within each major clade.
• Species-specific clades were not observed, and taxonomy of the genus needs revision.

Brevoortia Gill 1861 is a genus of the Clupeidae (Teleostei) that includes six species of fishes commonly known as menhadens in eastern North America and “savelhas” or “saracas” in southeastern South America. Species of Brevoortia are important components of the marine food web of coastal ecosystems in the Atlantic and contribute significantly to fisheries. In this study, the first phylogenetic and biogeographic hypotheses including all species of Brevoortia are presented. A total of 113 specimens were analyzed using three molecular markers (two mitochondrial: COI and 16s; and one nuclear: RAG2). Maximum Parsimony, Maximum Likelihood and Bayesian Inference were employed to estimate phylogenetic relationships. A Bayesian multispecies coalescent approach was used to estimate a dated phylogeny, which supported biogeographic analyses of ancestral geographic ranges. Results corroborate previous hypotheses that the four North Atlantic species are grouped in two clades, one composed of B. tyrannus (Latrobe, 1802) and B. patronus Goode, 1878, and the second including B. smithi Hildebrand, 1941 and B. gunteri Hildebrand, 1948. The South Atlantic B. aurea (Spix and Agassiz, 1829) and B. pectinata (Jenyns, 1842) form a third clade, which is sister to the clade composed of B. smithi and B. gunteri. The monophyly and validity of the six nominal species of Brevoortia were not supported. Results also indicate that Brevoortia originated in the North Atlantic during the middle Miocene (about 15 Mya). A cooling event of the tropical Atlantic at around 10 Mya likely facilitated the range expansion of the genus to the South Atlantic, whereas a significant warming of the tropical Atlantic waters during the late Miocene at 6-7 Mya possibly promoted the isolation between the northern and southern counterparts of that ancestral lineage. The relevance of the Florida Peninsula in association with sea level fluctuations for the diversification within Brevoortia is also discussed.

Keywords: Alosa, Biodiversity, Molecular systematics, Panama Isthmus, Teleostei, Tethyan Seaway

Brevoortia tyrannus Atlantic menhaden.
photo: Brian Gratwicke

Allan Pierre Bonetti Pozzobon, Pablo Rodrigues Gonçalves, Joel D. Anderson, Luiz A. Rocha, Juan M. Diaz de Astarloa and Fabio Di Dario. 2021. Phylogenetic Relationships, Genetic Diversity and Biogeography of Menhadens, Genus Brevoortia (Clupeiformes, Clupeidae). Molecular Phylogenetics and Evolution. In Press, 107108. DOI: 10.1016/j.ympev.2021.107108