Phylogeny of the Subfamily Corydoradinae Hoedeman, 1952 (Siluriformes: Callichthyidae), with a Definition of Its Genera
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PROCEEDINGS OF THE ACADEMY OF NATURAL SCIENCES OF PHILADELPHIA 153: 119±154. DECEMBER 2003 Phylogeny of the subfamily Corydoradinae Hoedeman, 1952 (Siluriformes: Callichthyidae), with a de®nition of its genera MARCELO R. BRITTO Museu de Zoologia da Universidade de SaÄo Paulo, SaÄo Paulo, SP, Brazil Present address: Museu NacionalÐUFRJÐSector de Ictiologia, Departamento de Vertebrados, Quinta da Boa Vista s/n, 20940±040 Rio de Janeiro, RJ, BrazilÐ[email protected] ABSTRACTÐA phylogenetic hypothesis of relationships within the callichthyid subfamily Corydoradinae is proposed based on 83 characters. The monophyly of the subfamily is well supported, as are those of two included genera, Aspidoras and Brochis. However, the monophyly of Corydoras, as traditionally de®ned, is not corroborated, with some of currently included species being more closely related to Aspidoras or Brochis than to nominal congeners. These conclusions contrast with a previous hypothesis, which considered Brochis and Corydoras as forming a monophyletic assemblage, with Aspidoras as its sister-group. A clade composed of Aspidoras and the species currently assigned to Corydoras, C. barbatus, C. ma- cropterus, C. prionotus and Corydoras sp. A, is herein recognized based on the following characters: possession of anterior portion of frontal bone long, hypobranchial 2 well ossi®ed, free margin of opercle angulated, epiphyseal branch of the supraorbital canal long, and ossi®ed portion of pectoral spine reduced. The remaining corydoradines are grouped in a monophyletic assemblage with complex vertebra compact, posterior expansion of ceratobranchial 3 notched, presence of triangular dorsal lamina on anguloarticular, and medial expansion of coracoid exposed. A new classi®cation is proposed to accommodate the monophyletic groups de®ned in the present study. Discussions about subgroups within each major clade are provided. RESUMOÐUma hipoÂtese sobre as relacËoÄes ®logeneÂticas da subfamõÂlia de Callichthyidae, Corydoradinae, e proposta com base em 83 caracteres. O mono®letismo da subfamõÂlia e corroborado, assim como o de dois geÃneros nela incluõÂdos, Aspidoras e Brochis. Entretanto, o mono®letismo de Corydoras, como tradicionalmente de®nido, naÄo e corroborado, com algumas de suas espeÂcies atuais sendo mais proximamente relacionadas a Aspidoras ou Brochis do que aos seus congeÃneres nominais. Estas conclusoÄes contrastam com uma hipoÂtese preÂvia que considera Brochis e Corydoras formando um agru- pamento mono®leÂtico, com Aspidoras como seu grupo-irmaÄo. Um clado composto por Aspidoras e as espeÂcies assinaladas a Corydoras, C. barbatus, C. macropterus, C. prionotus e Corydoras sp.A,e diagnosticado pelos seguintes caracteres: porcËaÄo anterior do osso frontal alongado, hipobranquial 2 bem ossi®cado, margem livre do opeÂrculo angulada, ramo epi®seal do canal supra-orbital alongado, e porcËaÄo ossi®cada do espinho peitoral reduzida. Os demais coridoradõÂneos saÄo reunidos em um grupo mono®leÂtico de®nido pela veÂrtebra complexa compacta, expansaÄo posterior do ceratobranquial 3 com um entalhe, presencËa de laÃmina dorsal triangular no aÃngulo-articular e expansaÄo medial do coracoÂide exposta. Uma nova classi®cacËaÄo e proposta para acomodar os grupos mono®leÂticos de®nidos no presente estudo. DiscussoÄes sobre subgrupos de cada um dos principais clados saÄo fornecidas. INTRODUCTION from the Rio Magdalena basin (however, this could be a mislocation; see Nijssen and IsbruÈcker, 1983). The subfamily Corydoradinae includes about Representatives of the Corydoradinae are found in 90% of the species in the Neotropical cat®sh family several freshwater environments, ranging from fast- Callichthyidae and is one of the most diverse silu- ¯owing piedmont streams with sandy or rocky bot- riform assemblages in the Neotropics, with approx- tom to lowland pools with muddy bottom. They imately 170 valid species (Nelson, 1994; Reis, are well known among ®shkeepers worldwide, with 1998a). Species of the Corydoradinae are of small Corydoras species being particularly popular. size (maximum about 90 mm in standard length) Most of the studies dealing with Corydoradinae and are easily distinguished from other callichthyids focused on species descriptions and taxonomic re- by their deep bodies and short maxillary barbels. visions (e.g. Ihering, 1907; Knaack, 1961; Nijssen, The Corydoradinae is currently composed of the 1970; Nijssen and IsbruÈcker, 1976, 1983, 1986a; genera Corydoras LaceÂpeÁde, Brochis Cope, and As- Burgess, 1993), and very little is known about the pidoras Ihering (Reis, 1998a). The subfamily has a phylogenetic relationships of its genera, largely due predominantly cis-Andean distribution north of the to the scarcity of data on internal anatomy. Nijssen Rio de La Plata system, in Argentina, with only one (1970) and Nijssen and IsbruÈcker (1980) arranged trans-Andean species, Corydoras melanotaenia Regan, the species of Corydoras in several groups on the 119 120 MARCELO R. BRITTO basis of color pattern, morphometric and meristic see ICZN, 1925: opinion 89, 1954: opinion 259, data, however those groupings were not intended to 1985; Eschmeyer, 1990). re¯ect phylogenetic relationships (Nijssen and Is- Valenciennes (in Cuvier and Valenciennes, 1840) bruÈcker, 1986a). Only two attempts have been suggested the identity of Corydoras geoffroy with Ca- made to elucidate the interrelationships among Cal- taphractus punctatus and added more morphological lichthyidae genera: Gosline (1940) and Reis data on the former. Later, the two species were syn- (1998a), with only the latter study carried out under onymized by Bleeker (1858), who proposed the new the cladistic paradigm. Although the recognition of combination Corydoras punctatus. As a consequence, the monophyly of Aspidoras and Brochis, Reis Hoplosoma became a junior synonym of Corydoras (1998a) recognized the genus Corydoras tentatively (see Nijssen, 1970). Recently, IsbruÈcker (1999a,b) on the basis of absence of synapomorphies de®ning pointed out that Corydoras geoffroy and Cataphractus the other two Corydoradinae genera. punctatus are distinct species, with the former being In the present study a phylogenetic analysis of the a valid species. IsbruÈcker (1999b) considered Cory- subfamily Corydoradinae is conducted, using as a doras octocirrus Nijssen, 1970 as a junior synonym framework recent phylogenetic hypotheses involving of Corydoras geoffroy. the Callichthyidae (Reis, 1997, 1998a), which dem- GuÈnther (1864) united callichthyid and loricariid onstrated overwhelmingly the monophyly of Cory- cat®shes in a subgroup, the ``Loricarina'', of the doradinae. The present analysis focused on species- more inclusive group ``Hypostomatina'', of his sub- level relationships in all three currently recognized family ``Siluridae Proteropodes''. Furthermore, that genera of the Corydoradinae with the objective of author proposed the inclusion of all callichthyid spe- testing the monophyly of each genus and determin- cies in a single genus, Callichthys Scopoli, divided ing the interrelationships within Corydoras, the most into three subgenera: Scleromystax (described in that species-rich cat®sh genus. A new classi®cation is work and including only Callichthys barbatus Quoy proposed for the subfamily in order to re¯ect the and Gaimard), Corydoras (including species belong- monophyletic groups de®ned herein. ing to Corydoras) and Callichthys (containing all the remaining callichthyid species). Historically, GuÈn- ther's (1864) study was the ®rst to suggest distinct HISTORICAL BACKGROUND OF THE groups within Corydoras, with the placement of CORYDORADINAE Callichthys barbatus (5Corydoras barbatus) in a sub- genus apart from other Corydoras species. This dis- Various changes occurred in the classi®cation of tinction was proposed on the basis of ``bristles'' the Callichthyidae between the time of the original (odontodes) present on the sides of the head in description of Silurus callichthys (5Callichthys cal- Callichthys barbatus (GuÈnther, 1864: 225). lichthys) by Linnaeus (1758), and Hoedeman's In 1871, Cope provided brief comments on some (1952) original proposal of the subfamilies cat®sh genera from the Amazon and proposed the Callichthtyinae and Corydoradinae. The history of genera Brochis and Dianema. A year later, in his what is now termed the Corydoradinae begins with study on ®shes from the Ambyiacu river, Peru, Cope the description of Cataphractus punctatus Bloch (1872) presented new formal descriptions of these (now Corydoras punctatus). two genera, apparently ignoring his previous study. LaceÂpeÁde (1803) later described the genus Cory- In this latter study, Cope raised Corydoras to generic doras, including a new species C. geoffroy (the type- status and arranged its included species in four species of the genus, by monotypy). The name Cor- groups according to modi®cations of the lower lip. dorinus proposed by Ra®nesque (1815) is an unjus- Gill (1872) removed callichthyids from GuÈnther's ti®ed emendation of Corydoras (Follett, 1952; Nijs- ``Hypostomatina'' and placed them in a distinct fam- sen and IsbruÈcker, 1980). ily, the Callichthyidae, with only one genus, Callichthyid cat®shes were ®rst recognized as a Callichthys, and considered the remaining nominal group (named the ``Callichthini'') within the family callichthyid genera as junior synonyms. Cope Siluridae by Bonaparte (1838). In that same year, (1878) described two new callichthyid genera, Chae- Swainson described Hoplisoma (subsequently nothorax and Gastrodermus,