Editorial Type:
Article Category: Research Article
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Online Publication Date: Nov 22, 2023

Phylogenomics and Morphology of the African Fish Genus Brycinus with Revalidation of Brachyalestes and Description of a New Species from the Congo Basin (Teleostei: Alestidae)

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Page Range: 597 – 611
DOI: 10.1643/i2023033
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A time-calibrated phylogeny, based on nuclear ultraconserved elements and including representatives of all major alestid lineages, strongly supports two distantly related clades within the currently accepted concept of Brycinus. The first, which includes the type species of the genus, B. macrolepidotus (herein Brycinus), and a second, composed of taxa previously referred to as the B. nurse group (herein Brachyalestes), are both resolved as monophyletic. These results provide strong evidence for the restriction of the genus Brycinus to nine species, and for the revalidation of the genus Brachyalestes to accommodate 20 valid species. Within Brachyalestes, a new species from the Lulua River basin, initially misidentified as Brycinus kingsleyae, is described and resolved as sister to the widespread, central Congolese lowland species, Brachyalestes bimaculatus. Within Brachyalestes, a subclade mostly restricted to the Central Congo basin is estimated to have undergone diversification within the last 10 million years, suggesting that Late Neogene riverine reorganization likely influenced their allopatric speciation. The split of the new species, endemic to high elevation tributaries of the Lulua River, from its lowland sister species, Brachyalestes bimaculatus, suggests a Late Miocene/Early Pliocene colonization into the upland river ecosystems of the Katanga plateau in the southwestern Democratic Republic of Congo.

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Copyright: © 2023 by the American Society of Ichthyologists and Herpetologists
Fig. 1.
Fig. 1.

Maximum likelihood tree of Brachyalestes and related alestid genera based on a 70% complete dataset of 481 ultraconserved element loci (119,993 bp). Brachyalestes jackiae highlighted in red. Photographs: J. Cutler, J. Mbimbi, M. Stiassny, R. Palmer, and South African Institute for Aquatic Biodiversity (used with permission).

Fig. 2.
Fig. 2.

Brycinus macrolepidotus, AMNH 270775. (A) Posterior neurocranium, Weberian apparatus, predorsal vertebrae, and associated structures (lateral view). (B) Neurocranium, premaxillae, and circumorbitals (dorsal view). (C) Isolated maxilla in lateral (left) and dorsal (right) views.

Fig. 3.
Fig. 3.

(A) Alestes liebrechtsii, AMNH 254612, posterior neurocranium, Weberian apparatus, predorsal vertebrae, and associated structures (lateral view); (B) Alestes liebrechtsii, AMNH 254612, neurocranium, premaxillae, and circumorbitals (dorsal view); (C) Bryconaethiops microstoma, AMNH 253823; (D) Bryconalestes longipinnis, AMNH 59626; (E) Brachyalestes nurse, AMNH 215629.

Fig. 4.
Fig. 4.

Brachyalestes jackiae. (A) AMNH 253243, holotype, male, 105.8 mm SL, Mutefu, Tshimayi River, Lulua-Kasai system, Kasai Central, Democratic Republic of Congo. (B) AMNH 252787, paratype, female, 114.1 mm SL, Kalumba, Lubi River, Lulua, Kasai Central, Democratic Republic of Congo. Scale bars = 1 cm.

Fig. 5.
Fig. 5.

Brachyalestes jackiae, AMNH 277628. (A) Premaxillae and dentition (ventral view); (B) isolated maxilla in lateral (left) and dorsal (right) views; (C) lower jaw (dorsal view); (D) circumorbital series.

Fig. 6.
Fig. 6.

Brachyalestes jackiae, AMNH 277628. (A) Posterior neurocranium, Weberian apparatus, predorsal vertebrae, and associated structures (lateral view); (B) neurocranium (posterior view); (C) neurocranium (dorsal view), 70.9 mm SL; (D) posterior neurocranium (dorsal view), 79.8 mm SL.

Fig. 7.
Fig. 7.

Brachyalestes jackiae, live coloration: (A) male, (B) female, (C) digestive tract (slightly unraveled for clearer depiction of morphology), after removal of liver, pancreas, gallbladder, spleen, and adherent tissues.

Fig. 8.
Fig. 8.

(A) Brachyalestes epuluensis, AMNH 5995, male, 79.7 mm SL, Avakubi, Ituri River, Democratic Republic of Congo (DRC); (B) Brachyalestes kingsleyae, AMNH 262921, male, 104.6 mm SL, Ivindo River, near Makokou, Ogooué-Ivindo, Gabon; (C) Brachyalestes kingsleyae, AMNH 262921, female, 104.0 mm SL, Ivindo River, Gabon; (D) Brachyalestes bimaculatus, AMNH 240760, male, 115.1 mm SL, confluence of Lofongo and Luilaka Rivers, Salonga National Park, DRC; (E) Brachyalestes bimaculatus, AMNH 242470, female, 102.7 mm SL, Lac Nkolentulu, Bandundu, DRC. Scale bars = 1 cm.

Fig. 9.
Fig. 9.

(A) Map of the central Congo basin and Lower Guinea showing analyzed museum records of Brachyalestes bimaculatus (green diamonds), B. jackiae (red triangles), and B. kingsleyae (yellow circles); collection habitats at (B) Kamuandu, Lubi River, (C) Lunyenga River, (D) Tshimayi River, (E) Luna River. Photographs by José J. M. M. Mbimbi.

Fig. 10.
Fig. 10.

Time-calibrated phylogeny based on BEAST analyses of ultraconserved elements (70% complete matrix; 481 loci; 119,993 bp). Ma = million years ago; Pal = Paleocene; Olig = Oligocene; Pli = Pliocene; Q = Quaternary. See Data Accessibility for tree file.

Contributor Notes

1 Department of Ichthyology, American Museum of Natural History, 200 Central Park West, New York, New York 10024; ORCID: (MLJS) 0000-0001-8220-4768; and (BFM) 0000-0002-0499-567X; Email: (MLJS) mljs@amnh.org; (CK) coop.keane@gmail.com; and (BFM) bmelo@amnh.org. Send correspondence to BFM.
2 Département de Biologie, Faculté des Sciences, Université de Kinshasa, B.P. 190 Kin XI, Kinshasa, République Démocratique de Congo; ORCID: 0009-0001-7666-1820; Email: jjmbimbishambuyi@gmail.com.

Associate Editor: R. E. Reis.

Received: May 17, 2023
Accepted: Sep 08, 2023