Using Morphology to Test DNA-Based Phylogenetic Relationships within the Guiana Shield Catfish Tribe Lithoxini (Siluriformes: Loricariidae)
As DNA-based phylogenetic analyses have exploded, historically phenotype-based evolutionary hypotheses throughout the tree of life have been rewritten. However, rarely are DNA-based phylogenetic hypotheses tested via the reanalysis of phenotypic data. Skeletons representing all four recognized genera of the Guiana Shield endemic suckermouth armored catfish clade Lithoxini were examined to test a recently published DNA-based phylogenetic hypothesis using morphological evidence. Phylogenetic analysis of 54 mostly osteological characters yielded a single most parsimonious tree of 90 steps that was congruent with the molecular hypothesis: (Avalithoxus, ((Exastilithoxus), (Lithoxus, Paralithoxus))). Lithoxini was a well-supported clade with 20 synapomorphies, as was each of the genera within this clade. Avalithoxus jantjae, which was originally described in Lithoxus, was found to be missing the unique synapomorphies of Lithoxus + Paralithoxus: a spoon-shaped, ventrally oriented process on the metapterygoid and a process on the preoperculo-hyomandibular ridge.
Right metapterygoids, lateral view of (A) Avalithoxus jantjae AUM 39478, (B) Neblinichthys yaravi AUM 36699, (C) Paralithoxus bovallii AUM 67127, (D) Paralithoxus sp. nov. aff. bovallii (Konawaruk) AUM 35549. APM, anterior process of metapterygoid; MPC, metapterygoid channel; MPS, metapterygoid suture to lateral ethmoid. Scale = 1 mm.
Right mandible, roughly dorsal view of (A) Avalithoxus jantjae AUM 39478, (B) Neblinichthys yaravi AUM 36699, (C) Paralithoxus bovallii AUM 67127. AA, anguloarticular; AAAF, anguloarticular fenestra; AAAP, anguloarticular anterior process; AMP, adductor mandibulae process; D, dentary; DTC, dentary tooth cup; QC, area quadrate condyle connects. Scale = 1 mm; gray shading indicates cartilage.
Right maxilla, dorsolateral view of (A) Avalithoxus jantjae AUM 39478, (B) Neblinichthys yaravi AUM 36699, (C) Paralithoxus bovallii AUM 67127. Scale = 1 mm.
Right opercle, medial view of (A) Avalithoxus jantjae AUM 39478, (B) Exastilithoxus fimbriatus MCNG 44872, (C) Lithoxus lithoides AUM 39040, (D) Neblinichthys yaravi AUM 36699, (E) Paralithoxus bovallii AUM 67127. HY, hyomandibula; OAP, opercle anterior process; OC, opercular condyle of hyomandibula; OPP, opercular posterior process; OS, opercular suture to hyomandibula. Scale = 1 mm; gray shading indicates cartilage.
Sphenotic and orbital region, dorsolateral view of (A) Avalithoxus jantjae AUM 39478, (B) Neblinichthys yaravi AUM 36699, (C) Paralithoxus bovallii AUM 67127. A and C, left side, B, right side but reflected. F, frontal; IO, infraorbital; O, orbit; SP, sphenotic. Scale = 1 mm.
Single most parsimonious tree of 90 steps, CI = 0.722, numbers above branches are bootstrap values/Bremer decay indices. Avalithoxus jantjae AUM 39478 (31.9 mm SL), Exastilithoxus fimbriatus AUM 36668 (23.6 mm SL), Lithoxus lithoides AUM 39040 (43.0 mm SL), Paralithoxus bovallii AUM 67127 (51.7 mm SL), P. sp. nov. aff. bovallii (Konawaruk) AUM 35549 (42.6 mm SL), P. planquettei AUM 50395 (47.0 mm SL), and P. surinamensis AUM 51737 (34.7 mm SL). Photos by JWA.
Contributor Notes
Associate Editor: R. E. Reis.