Neotropical Ichthyology, 13(2): 325-340, 2015 Copyright © 2015 Sociedade Brasileira de Ictiologia DOI: 10.1590/1982-0224-20140129 Phylogenetic relationships of the species of Acestridium Haseman, 1911 (Siluriformes: Loricariidae) Mónica S. Rodriguez1, Maria Laura S. Delapieve2 and Roberto E. Reis2 A phylogeny of the species of the loricariid genus Acestridium and relevant outgroups is presented based on a parsimony analysis of 52 unweighted and unordered morphological characters. Acestridium is diagnosed as monophyletic based on the possession of the 17 exclusive synapomorphies. Two primary trees were found, and the strict consensus among those alternative trees resulted in the following relationships: ((A. dichromum + A. triplax)(A. gymnogaster + A. scutatum + (A. discus (A. colombiensis + A. martini)))). Acestridium was found to be sister to Niobichthys with this clade subsequently the sister-group to Oxyropsis + Hypoptopoma. Uma filogenia das espécies do gênero de Loricariidae Acestridium e grupos externos relevantes é apresentada com base na análise de parcimônia de 52 caracteres morfológicos não pesados e desordenados. Acestridium é diagnosticado como monofilético com base na posse de 17 sinapomorfias exclusivas. Duas árvores primárias foram encontradas e o consenso estrito entre essas árvores alternativas resultou nas seguintes relações: ((A. dichromum + A. triplax)(A. gymnogaster + A. scutatum + (A. discus (A. colombiensis + A. martini)))). Acestridium foi encontrado como grupo-irmão de Niobichthys e este clado como grupo-irmão sucessivo de Oxyropsis + Hypoptopoma. Keywords: Amazon, Biodiversity, Evolution, Neotropical, Phylogeny. Introduction pectoral girdle that bears laminar extensions on the ventral surface of both the cleithrum and the coracoid that largely Loricariidae is the largest catfish family with almost 900 or entirely cover the fossae for the arrector muscles. species recognized as valid and more described each year. The species level taxonomic history of Acestridium is Loricariids are distributed throughout most of the Neotropics, largely recent. Except for A. discus Haseman, 1911, all other extending from Costa Rica to northern Argentina. The vast species have been described in the last 15 years. Currently, majority of the species occur on the Andes, but with several seven species are recognized: Acestridium discus, A. species restricted to the western slopes of that mountain dichromum Retzer, Nico & Provenzano, 1999, A. martini range (Reis et al., 2003). Six subfamilies are currently Retzer, Nico & Provenzano, 1999, A. colombiensis Retzer, recognized: Delturinae, Hypoptopomatinae, Hypostominae, 2005, A. triplax Rodriguez & Reis, 2007, A. gymnogaster Lithogeninae, Loricariinae, and Neoplecostominae (Reis et Reis & Lehmann, 2009 and A. scutatus Reis & Lehmann, al., 2006). 2009. The position of the genus has been inconsistent in Hypoptopomatinae is a monophyletic subfamily comprised different revisions of the Loricariidae. Gosline (1945) placed of 20 genera (Reis et al., 2012). Most species are relatively Acestridium in the subfamily Loricariinae. Subsequently, small as adults, ranging from 20 to 45 mm in SL. Like Isbrücker & Nijssen (1974) relocated Acestridium to the other members of the Loricariidae, hypoptopomatines are subfamily Acestridiinae stating that it did not belong in encased in dermal plates which bear numerous odontodes, Loricariinae, but providing no evidence to justify their or dermal teeth, and the mouth is surrounded by expanded action. Most recently, Isbrücker (1980) placed the genus fleshy lips forming a suctorial device. Hypoptopomatines in the subfamily Loricariinae, tribe Acestridiini. Finally, are distinguished from all other loricariids, among other Nijssen & Isbrücker (1987) diagnosed and placed the genus features, by the totally or partially ventrally exposed in the Hypoptopomatinae. 1Universidade Federal de Viçosa, Campus de Rio Paranaíba, Rodovia MG-230 km 7, Caixa Postal 22, 38810-000 Rio Paranaíba, MG, Brazil. [email protected] 2Laboratório de Sistemática de Vertebrados, Pontifícia Universidade Católica do Rio Grande do Sul, Faculdade de Biociências, Av. Ipiranga 6681, Caixa Postal 1429, 90619-900 Porto Alegre, RS, Brazil. (MLSD) [email protected], (RER) [email protected] (corresponding author) 325 326 Phylogenetic relationships of Acestridium In the first phylogenetic analysis of the hypoptopomatines, Schaefer, 1996); a truncated mid-dorsal lateral plate series Schaefer (1991) united Hypoptopoma Gunther, 1868, and the plates of the canal-bearing median series dorsally Oxyropsis Eigenmann & Eigenmann, 1889, Acestridium, expanded; the presence of a conspicuous enlarged median Niobichthys Schaefer & Provenzano, 1998 (then as new pre-anal shield plate. genus), Otocinclus Cope, 1871, and Microlepidogaster Although Acestridium has been demonstrated to be a Eigenmann & Eigenmann, 1889 as the tribe member of the Hypoptomatinae, its position in the family Hypoptopomatini. The tribe was diagnosed by the absence is uncertain and the phylogenetic relationships of its of a levator arcus palatini crest on the hyomandibula and species have never been investigated. In the present study, reduced levator muscle, the presence of few, relatively a phylogenetic analysis of the species of Acestridium is large plates at the anterior margin of the snout, and a provided based on osteology and comparison with other ventrolateral reflection of the cheek plates. A number of members of the Hypoptopomatinae, and an expanded synapomorphic traits were used to diagnose Acestridium: phylogenetic diagnosis is advanced for the genus and ten principal caudal-fin rays; the dermal plates anterior species groups. to first dorsal-fin proximal radial expanded, bearing a ventromedial keel contacting the dorsal margin of the Material and Methods neural arches of vertebrae six through twelve; and the presence of a medially reflected ridge of bone on the Unless otherwise indicated, the descriptions of ventral surface of the lateral ethmoid contacting the characters and character states pertain only to the metapterygoid channel. Schaefer (1991) also added as specimens listed in Material Examined. Skeletal diagnosing features the plates at the anterior margin of the terminology follows Schaefer (1987), except that snout forming a conspicuous spatulate projection; the very parieto-supraoccipital replaces supraoccipital (Arratia & slender, depressed head and body; the dorsal surface of Gayet, 1995), and compound pterotic replaces pterotic- the head and trunk with longitudinal ridges; a posteriorly supracleithrum (Aquino & Schaefer, 2002). Fishes were placed dorsal fin, well beyond pelvics just anterior to anal- cleared and double-stained for cartilage and for bone fin origin; and the absence of an adipose fin. according to procedures derived from Taylor & van Dyke Schaefer (1997), in a revision of Otocinclus and (1985). reanalysis of the position of the genus in the subfamily The data matrix for the phylogenetic analysis provided using additional discovered character evidence, in Table 1 was constructed using Mesquite, version reaffirmed the earlier phylogeny of Schaefer (1991), with 2.74 (Maddison & Maddison, 2006) and exported and the exception that Microlepidogaster was transferred to submitted to heuristic parsimony analyses in NONA the tribe Otothyrini. Finally, Schaefer (1998) diagnosed (Goloboff, 1999) under Winclada 1.00.08 (Nixon, 2002) Hypoptopomatinae by the following six synapomorphies: Windows shell. The heuristic search was performed with the presence of a ventrally opened nasal capsule (reversed 1000 replications of Random Addition Sequence (RAS) in Acestridium); the pterotic bone pierced by numerous and Tree Bisection Reconnection (TBR) branch swapping, fenestrae and enlarged in all hypoptopomatines; the followed by a final round of global TBR. All character presence of a metapterygoid channel; the closed arrector transformations were unweighted and unordered. Branch fossae of the ventral pectoral skeleton; the presence of support was calculated as Bremer decay index (Bremer, a median rostral snout plate (reversed in Niobichthys 1994) in NONA. Character state transformations are given Schaefer & Provenzano, 1998); and the possession of in Appendix 1. enlarged odontodes on both the dorsal and ventral margins Taxa were selected based on previous phylogenetic of the snout (reversed in Niobichthys). hypothesis of the Hypoptopomatini (Schaefer, 1997, 1998). In the same year, Schaefer & Provenzano (1998) Outgroups in the Hypoptopomatini were Hypoptopoma described Niobichthys and rediagnosed the tribe spectabile (Eigenmann, 1914), H. inexspectatum Hypoptopomatini based on the following synapomorphies: (Holmberg, 1893), Niobichthys ferrarisi Schaefer & the elongate lateral ethmoid-antorbital lateral process, Provenzano, 1998, Oxyropsis wrightiana Eigenmann with the contact between the lateral ethmoid and the third & Eigenmann, 1889, Otocinclus batmani Lehmann, infraorbital located well lateral to the lateral margin of 2006 and O. arnoldi Regan, 1909 and in the Otothyrini the nasal capsule (reversed in Acestridium); a reduced Hisonotus maculipinnis Regan, 1912, which was also used pterotic lateral fenestrae (reversed from derived state for to root the trees. the Hypoptopomatinae); the number of bifid haemal spines In Comparative Material Examined lots are grouped by reduced to 2; the reduced intervertebral interdigitations country and within each country, by state or department, between successive