Mark H. Sabaj Pérez

Freshwater Ecoregions of the World: A New Map of Biogeographic Units for Freshwater Biodiversity Conservation

ABSTRACT We present a new map depicting the first global biogeographic regionalization of Earths freshwater systems. This map of freshwater ecoregions is based on the distributions and compositions of freshwater fish species and incorporates major ecological and evolutionary patterns. Covering virtually all freshwater habitats on Earth, this ecoregion map, together with associated species data, is a useful tool for underpinning global and regional conservation planning efforts (particularly to identify outstanding and imperiled freshwater systems); for serving as a logical framework for large-scale conservation strategies; and for providing a global-scale knowledge base for increasing freshwater biogeographic literacy. Preliminary data for fish species compiled by ecoregion reveal some previously unrecognized areas of high biodiversity, highlighting the benefit of looking at the worlds freshwaters through a new framework.

Morphology of the Gas Bladder in Thorny Catfishes (Siluriformes: Doradidae)

ABSTRACT. The gross morphology of the gas bladder is described, illustrated, compared and categorized among 86 of 88 nominal valid and six undescribed species representing all 31 genera of Doradidae with comments on ontogenetic and taxonomic variation when observed. The putatively basal-most doradids exhibit an unmodified cordiform gas bladder. Derived taxa exhibit an impressive suite of modifications including the addition of a secondary bladder, pronounced reduction of the posterolateral chambers, internal trabeculae, associations with bony capsule-like expansions of the anterior (Weberian) vertebrae, and accessory diverticula varying widely in size, shape, abundance, and distribution, Intra-specific differences are minor, most often reflective of ontogenetic changes especially in large-size species, whereas inter-specific and inter-generic differences are significant, in many cases diagnostic, and suggestive of phylogenetic signal excepting instances of evident convergence such as gas bladder reduction in Rhynchodoras and all but one species of Leptodoras.

Fossil catfishes of the families Doradidae and Pimelodidae (Teleostei: Siluriformes) from the Miocene Urumaco Formation of Venezuela

ABSTRACT Four taxa are added to the fossil history of catfishes based on new identifications and descriptions of material from the Miocene Urumaco Formation in northwestern Venezuela. Three of the fossil catfishes belong to the family Doradidae (thorny catfishes); one, Doras dioneae, represents a new species, the first fossil doradid to be formally named, and the other two, Doraops cf. zuloagai and Rhinodoras cf. thomersoni, are referred to modern taxa endemic to the Maracaibo basin. The fourth fossil catfish belongs to the family Pimelodidae (long-whiskered catfishes) and is assigned to Platysilurus, a modern genus that occurs in the Maracaibo, Orinoco, Amazon, and large rivers of the Guianas. These fossil taxa inhabited the paleo-Amazon-Orinoco, a large ancient river system that drained the South American continent northward prior to the uplift of the Eastern Andes and Coastal Cordilleras and concomitant isolation of the Maracaibo basin in the Late Miocene (ca. 8 Ma). Species novum: Doras dioneae Sabaj Pérez, Aguilera and Lundberg

Molecular phylogeny of thorny catfishes (Siluriformes: Doradidae).

Doradidae is a monophyletic catfish family endemic to continental South America, and composed of 93 valid species here placed in 31 genera. Existing phylogenetic hypotheses for Doradidae are derived from comprehensive analyses of morphological data, and a single molecular-based study on a limited subset of taxa. To provide a robust molecular phylogeny commensurate with those based on morphology, we gathered original and published sequence data for 86 species-level taxa (at least 70 valid species plus 16 new or questionably nominal species) and all genera of Doradidae, as well as 10 species (nine genera) of Auchenipteridae and three species and genera of Aspredinidae as outgroups. 3011 base pairs were aligned for two mitochondrial genes (cytochrome c oxidase subunit 1, and 16S ribosomal RNA) and one nuclear gene (recombination activating gene 1), and analyzed for a total of 143 specimens (130 doradids, 10 auchenipterids and three aspredinids). Tree topologies generated by Maximum Parsimony, Maximum Likelihood, and Bayesian analyses were largely congruent, and are compared to existing phylogenies based on morphology and molecules. Although many of the relationships supported by our molecular analyses corroborated those based on morphology, others are newly hypothesized or remain in conflict. The monotypic Wertheimeria, Franciscodoras and Kalyptodoras, for example, form a newly proposed clade, and the subfamily Astrodoradinae is placed at the base of the doradid tree. The monotypic Doraops and Centrochir, endemic to Caribbean drainages north and west of the Andes, are sister to Pterodoras and Platydoras, respectively, two genera that are widely distributed in Atlantic drainages. Additional biogeographic implications are discussed for hypothesized relationships among doradids. Molecular evidence strongly supports synonymization of monotypic Merodoras with Amblydoras, and transfer of Amblydoras bolivarensis to genus Scorpiodoras. Furthermore, we consider Opsodoras ternetzi to be more properly placed in the genus Nemadoras. The genus Opsodoras may warrant synonymization with Hemidoras, and the monophyly of genus Ossancora is not supported; however, we refrain from taxonomic decisions regarding those taxa until a broader spectrum of doradids can be submitted to further morphological and molecular phylogenetic analyses.

Taxonomic revision of extant Doras Lacepède, 1803 (Siluriformes: Doradidae) with descriptions of three new species

ABSTRACT Extant Doras are newly diagnosed among Doradidae by the unique combination of maxillary barbels long and fimbriate; mesethmoid with anterior lateral margins converging towards narrow tip; single anterior cranial fontanel contained largely within frontals and anteriorly by mesethmoid (posterior cranial fontanel occluded); anterior nuchal plate wide, pentaganol or roughly hexagonal, sharing distinct lateral suture with epioccipital and isolating supraoccipital from middle nuchal plate; nuchal foramina absent; coracoid process short, posterior tip falling well short of that of postcleithral process; dentary with acicular teeth; and skin immediately ventral to postcleithral process perforated with conspicuous pores. One fossil species, †D. dioneae, and two nominal extant species, D. carinatus and D. micropoeus, are recognized as valid and the latter two redescribed. Three additional extant species, D. phlyzakion, D. higuchii and D. zuanoni, are newly described from the middle Amazon and tributaries, lower Amazon tributaries and rio Araguaia (Tocantins drainage), respectively. Doras phlyzakion and D. zuanoni form a monophyletic group that is found in lowland, lentic habitats, and is characterized by multiple conspicuous pores in skin on breast and abdomen, a trait unique among doradids and rare if not unique among all catfishes. The remaining extant species, D. carinatus, D. higuchii and D. micropoeus, with uncertain relationships, are found in upland, lotic habitats. The occurrence of D. carinatus in the Orinoco basin suggests a historical link between right-bank tributaries of the lower Orinoco (e.g., Caroní) draining the western Guiana Shield and more eastern rivers (e.g., Cuyuní-Essequibo) that drain the Shield directly into the Atlantic Ocean. A key to extant species is provided, a neotype is designated for Silurus carinatus Linnaeus 1766, and Mormyropsis Miranda Ribeiro, 1911, is placed in the synonymy of Doras Lacepède, 1803. New taxa: Doras higuchii Sabaj Pérez and Birindelli, Doras phlyzakion Sabaj Pérez and Birindelli, Doras zuanoni Sabaj Pérez and Birindelli

Platydoras brachylecis, a new species of thorny catfish (Siluriformes: Doradidae) from northeastern Brazil

Platydoras brachylecis, new species, is described from coastal drainages of northeastern Brazil (Pindare to Parnaiba rivers), and diagnosed from congeners by the unique combination of: pale yellow to white stripe beginning above orbits, continuing midlaterally on body and onto middle rays of caudal fin; skin in axil of each midlateral thorn without concentration of pigment forming small dark spot, midlateral scutes shallow (depth of 10 th scute 8.8-11.9% of SL), and midlateral scutes on caudal peduncle distinctly separated by strip of skin from middorsal and midventral caudal-peduncle plates. Three additional species of Platydoras are recognized as valid: P. armatulus (lower Orinoco, Amazon and Paraguay-Parana drainages), P. costatus (coastal drainages of Suriname and French Guiana), and P. hancockii (upper Orinoco, Negro, Essequibo and Demerara drainages). The nominal species P. dentatus and P. helicophilus are tentatively treated as junior synonyms of P. costatus. A key to species of Platydoras is provided. Platydoras brachylecis, especie nova, e descrita para as drenagens costeiras do nordeste do Brasil (rios Pindare a Parnaiba) e diagnosticada de suas congeneres pela exclusiva combinacao dos seguintes caracteres: faixa amarelo-palida a branco iniciando acima das orbitas, continuando medio-lateralmente sobre o corpo e atingindo os raios medianos da nadadeira caudal; pele das axilas dos espinhos medio-laterais sem concentracao de pequenas pintas negras; escudos medio-laterais baixos (altura do decimo escudo 8.8-11.9% do comprimento padrao) e escudos medio-laterais do pedunculo caudal distintamente separados das placas medio-dorsais e medio-ventrais da mesma regiao por uma faixa de pele. Mais tres especies de Platydoras sao reconhecidas como validas: P. armatulus (distribuida pelas drenagens do baixo Orinoco, Amazonia e Paraguai-Parana), P. costatus (drenagens costeiras do Suriname e Guiana Francesa) e P. hancockii (drenagens do Negro, Essequibo, Demerara e alto Orinoco). As especies nominais P. dentatus e P. helicophilus sao provisoriamente consideradas sinonimos juniores de P. costatus. Uma chave de identificacao para as especies do genero Platydoras e apresentada.

Palaeontological Evidence for the Last Temporal Occurrence of the Ancient Western Amazonian River Outflow into the Caribbean

Fossil catfishes from fluvio-lacustrine facies of late Miocene Urumaco, early Pliocene Castilletes and late Pliocene San Gregorio formations provide evidence of a hydrographic connection in what is today desert regions of northern Colombia and Venezuela. New discoveries and reevaluation of existing materials leads to the recognition of two new records of the pimelodid Brachyplatystoma cf. vaillantii, and of three distinct doradid taxa: Doraops sp., Rhinodoras sp., and an unidentified third form. The presence of fossil goliath long-whiskered catfishes and thorny catfishes are indicative of the persistence of a fluvial drainage system inflow into the South Caribbean during the Pliocene/Pleistocene boundary, complementary to the previous western Amazonian hydrographic system described from the Middle Miocene Villavieja Formation in central Colombia and Late Miocene Urumaco Formation in northwestern Venezuela. The Pliocene Castilletes and San Gregorio formations potentially represent the last lithostratigraphic units related with an ancient western Amazonian fish fauna and that drainage system in the Caribbean. Alternatively, it may preserve faunas from a smaller, peripheral river basin that was cut off earlier from the Amazon-Orinoco, today found in the Maracaibo basin and the Magdalena Rivers.

Potamotrygon tigrina, a new species of freshwater stingray from the upper Amazon basin, closely related to Potamotrygon schroederi Fernandez-Yépez, 1958 (Chondrichthyes: Potamotrygonidae)

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Ossancora, New Genus of Thorny Catfish (Teleostei: Siluriformes: Doradidae) with Description of One New Species

ABSTRACT. Ossancora, new genus, is diagnosed within Doradidae by having the unique combination of posterior coracoid process approximately as long as posterior cleithral process in adults, posterior cranial fontanel occluded, long maxillary barbel with smooth elongate fimbriae, and teeth present on dentary and premaxilla. A similarly long posterior coracoid process is found in only one other doradid species, Trachydoras paraguayensis, which is distinguished, as are its congeners, from Ossancora by having a small posterior cranial fontanel retained in adults, a relatively short maxillary barbel with stout fimbriae, and edentulous jaws. Three nominal species are recognized as valid and redescribed in Ossancora: Doras punctatus Kner 1853, in both the Amazonas and Paraná-Paraguay basins, Oxydoras eigenmanni Boulenger 1895, in the Paraguay basin, and Doras fimbriatus Kner 1855 in the Amazonas basin. The younger name Doras fimbriatus Kner 1855 is considered valid as a nomen protectum according to Article 23.9 of the ICZN, and its older synonym, D. loricatus Kner 1853 qualifies as a nomen oblitum. A fourth new species, Ossancora asterophysa, is described and diagnosed in part by a gas bladder morphology that is distinctive among congeners. Three species, O. eigenmanni, O. fimbriata and O. asterophysa, form a monophyletic group based on three shared characteristics: smooth elongate fimbriae inserted in more than one row, one dorsally and one ventrally, along anterior margin of maxillary barbel (uniquely derived among Doradidae), elongate fimbriae on mental barbels, and anterior nuchal plate reduced, not sutured to epioccipital (latter two features uniquely derived among Ossancora). Ossancora is typical of lowland floodplain lakes and river channels, and its occurrence in the both the Amazonas and Paraná-Paraguay supports a historical link between these two basins. A key to species and detailed anatomical descriptions are provided. Type specimens are discussed and lectotypes are newly designated for Oxydoras eigenmanni Boulenger 1895, D. fimbriatus Kner 1855, and Doras (Corydoras) punctatus Kner 1853, respectively.

Seasonal changes in the assembly mechanisms structuring tropical fish communities

Despite growing interest in trait-based approaches to community assembly, little attention has been given to seasonal variation in trait distribution patterns. Mobile animals can rapidly mediate influences of environmental factors and species interactions through dispersal, suggesting that the relative importance of different assembly mechanisms can vary over short time scales. This study analyzes seasonal changes in functional trait distributions of tropical fishes in the Xingu River, a major tributary of the Amazon with large predictable temporal variation in hydrologic conditions and species density. Comparison of observed functional diversity revealed that species within wet-season assemblages were more functionally similar than those in dry-season assemblages. Further, species within wet-season assemblages were more similar than random expectations based on null model predictions. Higher functional richness within dry season communities is consistent with increased niche complementarity during the period when fish densities are highest and biotic interactions should be stronger; however, null model tests suggest that stochastic factors or a combination of assembly mechanisms influence dry-season assemblages. These results demonstrate that the relative influence of community assembly mechanisms can vary seasonally in response to changing abiotic conditions, and suggest that studies attempting to infer a single dominant mechanism from functional patterns may overlook important aspects of the assembly process. During the prolonged flood pulse of the wet season, expanded habitat and lower densities of aquatic organisms likely reduce the influence of competition and predation. This temporal shift in the influence of different assembly mechanisms, rather than any single mechanism, may play a large role in maintaining the structure and diversity of tropical rivers and perhaps other dynamic and biodiverse systems.