Sunday, April 12, 2020

[Ichthyology • 2020] Phylogeny and Biogeography of the Brazilian–Guiana Shield Endemic Corymbophanes Clade of Armoured Catfishes (Loricariidae)

Yaluwak primus Lujan, Armbruster & Werneke

in Lujan, Armbruster, Werneke, Teixeira & Lovejoy, 2020. 
Numerous rivers, interrupted by large waterfalls and extensive rapids, drain the geologically ancient Guiana Shield Highlands. We describe a new armoured catfish genus and two new species endemic to the upper Ireng and Kuribrong rivers, respective tributaries of the Amazon and Essequibo basins in western Guiana. Corymbophanes ameliae sp. nov. is distinguished by having vermiculations on the abdomen, bands on the caudal fin, the anal fin i,5 and narrow caudal peduncle. Yaluwak primus gen. & sp. nov. is distinguished by having evertible cheek odontodes, a plated snout, a tall caudal peduncle and absence of adipose fin and iris operculum. We present a new molecular phylogenetic analysis inclusive of these and several related genera that suggests that the Corymbophanes clade (Araichthys, Corymbophanes, Cryptancistrus, Guianancistrus, Hopliancistrus and Yaluwak) originated in the Guiana Shield with secondary dispersal to the Brazilian Shield. Within the Guiana Shield, relationships among Corymbophanes and Yaluwak are consistent with geodispersal between drainages via headwater capture, although an uplift-mediated relictual distribution cannot be ruled out. ND2 haplotype structure among C. ameliae populations suggests that ichthyofaunal diversity on the Guiana Shield escarpment is shaped not only by inter-, but also intrafluvial barriers to gene flow.

Keywords: Amaila Falls, Amazonian Craton, Guianas, Ireng River, Kuribrong River, Rio Maú, Potaro River, sexual dimorphism

Figure 5. Corymbophanes ameliae paratype, ROM 89897, 80.8 mm SL, Guiana, Region 8 (Potaro–Siparuni), Kuribrong River at rapids ~15 min upstream of upstream Kuribrong Camp, ..., 454 m a.s.l., 19–20 March 2011.
Photos by Nathan K. Lujan.

Corymbophanes ameliae Lujan et al., sp. nov.

Etymology: Named for Amelia, a Patamona Amerindian girl who disappeared near Amaila Falls in the late 19th century. The falls are named for her, but her name was misspelled.

Figure 2. Phylogenetic relationships of taxa within the tribe Ancistrini (Loricariidae: Hypostominae), including the new genus and species Yaluwak primus and new species Corymbophanes ameliae. Relationships based on Bayesian analysis of a 4123 bp alignment consisting of three mitochondrial (16S, Cytb, ND2) and two nuclear loci (RAG1, RAG2; Table 2). Node numbers correspond to Bayesian posterior probability (BI) and maximum likelihood (ML) support values in Table 3; numbers in red indicate BI < 0.90, whereas numbers in italics indicate ML < 60. Green, red and blue colours for Corymbophanes ameliae correspond to those in Figure 3. MC = main channel, Trib = tributary

Figure 1. Distributions of Corymbophanes and Yaluwak specimens examined in this study. OC = Oung Creek.

Figure 8. Holotype of Yaluwak primus, CSBD F1722, 122.9 mm SL, Guiana, Region 8 (Potaro–Siparuni), 5. Sukwabi Creek, East Fork, downstream of Wotowanda Falls, ..., 634 m a.s.l., 13 January 2016.

Yaluwak Lujan & Armbruster, gen. nov. 

Etymology: Yaluwak is the Patamona Amerindian word for this species (and used generally for larger loricariids). The pronunciation of the ‘l’ in Yaluwak is a guttural ‘lr’ sound. Name is treated as masculine. 
Included species: Yaluwak contains only the type species 

Yaluwak primus Lujan, Armbruster & Werneke, sp. nov. 

Etymology: The species epithet primus comes from the same Latin word meaning first, foremost, chief or principal and is in reference to the large body size of the species and the fact that it retains the evertible cheek odontodes, likely inherited from the common ancestor of the Yaluwak/Corymbophanes clade. This species name was also inspired by our indefatigable Patamona guide, Mr Primus Peters, who led the collection effort for this species and assisted in innumerable other ways during our 2016 expedition to the upper Ireng River.

Nathan K. Lujan, Jonathan W. Armbruster, David C. Werneke, Túlio Franco Teixeira and Nathan R. Lovejoy. 2020. Phylogeny and Biogeography of the Brazilian–Guiana Shield Endemic Corymbophanes Clade of Armoured Catfishes (Loricariidae). Zoological Journal of the Linnean Society. 188(4); 1213–1235. DOI: 10.1093/zoolinnean/zlz090