Rapid Parallel Morphological and Mechanical Diversification of South American Pike Cichlids (Crenicichla).

Explosive bouts of diversification are one of the most conspicuous features of the tree of life. When such bursts are repeated in similar environments, it suggests some degree of predictability in the evolutionary process. We assess parallel adaptive radiation of South American pike cichlids (Crenicichla) using phylogenomics and phylogenetic comparative methods. We find that species flocks in the Uruguay and Iguazú River basins rapidly diversified into the same set of ecomorphs that reflect feeding ecology. Both adaptive radiations involve expansion of functional morphology, resulting in unique jaw phenotypes. Yet, form and function were decoupled such that most ecomorphs share similar mechanical properties of the jaws (i.e., jaw motion during a feeding strike). Prey mobility explained 6- to 9-fold differences in the rate of morphological evolution but had no effect on the rate of mechanical evolution. We find no evidence of gene flow between species flocks or with surrounding coastal lineages that may explain their rapid diversification. When compared with cichlids of the East African Great Lakes and other prominent adaptive radiations, pike cichlids share many themes, including the rapid expansion of phenotypic diversity, specialization along the benthic-to-pelagic habitat and soft-to-hard prey axes, and the evolution of conspicuous functional innovations. Yet, decoupled evolution of form and function and the absence of hybridization as a catalyzing force are departures from patterns observed in other adaptive radiations. Many-to-one mapping of morphology to mechanical properties is a mechanism by which pike cichlids attain a diversity of feeding ecologies while avoiding exacerbating underlying mechanical trade-offs. [Adaptive radiation; ecological opportunity; feeding kinematics; functional trade-off; hybridization; introgression.].

MtDNA species-level phylogeny and delimitation support significantly underestimated diversity and endemism in the largest Neotropical cichlid genus (Cichlidae: Crenicichla).

Crenicichla is the largest and most widely distributed genus of Neotropical cichlids. Here, we analyze a mtDNA dataset comprising 681 specimens (including Teleocichla, a putative ingroup of Crenicichla) and 77 out of 105 presently recognized valid species (plus 10 out of 36 nominal synonyms plus over 50 putatively new species) from 129 locations in 31 major river drainages throughout the whole distribution of the genus in South America. Based on these data we make an inventory of diversity and highlight taxa and biogeographic areas worthy of further sampling effort and conservation protection. Using three methods of molecular species delimitation, we find between 126 and 168 species-like clusters, i.e., an average increase of species diversity of 65-121% with a range of increase between species groups. The increase ranges from 0% in the Missioneira and Macrophthama groups, through 25-40% (Lacustris group), 50-87% (Reticulata group, Teleocichla), 68-168% (Saxatilis group), 125-200% (Wallacii group), and 158-241% in the Lugubris group. We found a high degree of congruence between clusters derived from the three used methods of species delimitation. Overall, our results recognize substantially underestimated diversity in Crenicichla including Teleocichla. Most of the newly delimited putative species are from the Amazon-Orinoco-Guiana (AOG) core area (Greater Amazonia) of the Neotropical region, especially from the Brazilian and Guiana shield areas of which the former is under the largest threat and largest degree of environmental degradation of all the Amazon.

Description of a new species of the Neotropical cichlid genus Gymnogeophagus Miranda Ribeiro, 1918 (Teleostei: Cichliformes) from the Middle Paraná basin, Misiones, Argentina.

Gymnogeophagus jaryi, new species, is described from Southern tributaries of the Middle Paraná basin in Misiones. It can be distinguished from all other members of the genus, except from G. australis and G. caaguazuensis, by the presence of a hyaline to grey anterior portion of the dorsal fin. Gymnogeophagus jaryi differs from G. caaguazuensis by a longer caudal peduncle, caudal fin not lyrate, central portion of scales on dorsal portion of trunk light iridescent blue and by white spots in soft portion of dorsal fin in adult males, and from G. australis by the light iridescent blue coloration of central portion of scales on the dorsal portion of trunk and tail, and by the lack of scales on the soft portion of the dorsal fin. Additionally, it can be diagnosed by the following unique combination of characters: 10-11 dorsal-fin branched rays, 27-30 E1 scales, absence of lips thickening, and, in males, by the possession of a hump in adults, caudal fin not lyrate, presence of large white spots forming transversal stripes distally and in anterior area of the dorsal fin's soft portion, central area of scales on the dorsal portion of the trunk light iridescent blue, lack of scales on the base of the dorsal fin's soft portion, absence of a conspicuous and oblique dark band from the eye to the anterior border of the head, anterior portion of dorsal fin hyaline to grey, scales of the midlateral spot each bearing a semicircular light blue blotch, head hump starting at the horizontal through the eyes, concave anterior profile in lateral view, base of unpaired fins yellow, and whitish hyaline spots on caudal fin. The new species, based on mtDNA phylogeny, is the sister species of G. caaguazuensis from the Paraguay basin and is closely related to G. australis.

Island- and lake-like parallel adaptive radiations replicated in rivers.

Parallel adaptive radiations have arisen following the colonization of islands by lizards and lakes by fishes. In these classic examples, parallel adaptive radiation is a response to the ecological opportunities afforded by the colonization of novel ecosystems and similar adaptive landscapes that favour the evolution of similar suites of ecomorphs, despite independent evolutionary histories. Here, we demonstrate that parallel adaptive radiations of cichlid fishes arose in South American rivers. Speciation-assembled communities of pike cichlids (Crenicichla) have independently diversified into similar suites of novel ecomorphs in the Uruguay and Paraná Rivers, including crevice feeders, periphyton grazers and molluscivores. There were bursts in phenotypic evolution associated with the colonization of each river and the subsequent expansion of morphospace following the evolution of the ecomorphs. These riverine clades demonstrate that characteristics emblematic of textbook parallel adaptive radiations of island- and lake-dwelling assemblages are feasible evolutionary outcomes even in labile ecosystems such as rivers.

Oligosarcus amome (Ostariophysi: Characidae), a new species from the río Uruguay basin, Misiones, Argentina.

Oligosarcus amome is described from tributaries of the arroyo Yabotí-Guazú, río Uruguay basin, Misiones Province, Argentina. This new species can be distinguished from all its congeners by the following combination of characters: presence of two conspicuous series of teeth on premaxilla bearing pentacuspidate teeth in the outer series. Oligosarcus amome is the sister taxon of all remaining analyzed species of the genus excepting O. itau. 

Phylogeographic pattern of Jenynsia multidentata (cyprinodontiformes: anablepidae) in the southern boundary of the Brazilian subregion, Argentina

The Atlantic drainage basins are located in the southern Pampean area, in the southernmost part of the Brazilian subregion. Tectonic and paleoclimatic phenomena, occurring during the Quaternary, have currently isolated these basins from the present hydrographic system. Their ichthyofaunal composition is similar to that of hydric systems located further northward. Jenynsia multidentata is a species with wide distribution in the Atlantic drainage basins, as well as in those Northern basins. Here we investigated the phylogeographic pattern of Jenynsia multidentata and analyzed its relationships with the paleoclimatic and geologic history of the region. The analysis of the population's assemblage showed moderate genetic diversity, demographic equilibrium and marked genetic structure in the populations that occupy the extremes of the distributional range. The populations in the center of the range did not present genetic diversity, sharing a single haplotype. These results allow inferring that the presence of Jenynsia multidentata in the area results from historical demographic processes that are independent but complementary. In turn, these processes could arise from paleoclimatic changes occurred during the Quaternary.

Las cuencas de pendiente atlántica del área pampeana Austral son el límite meridional de la subregión Brasílica. Fenómenos tectónicos y paleoclimáticos ocurridos durante el Cuaternario han dejado aisladas a estas cuencas del diseño hidrográfico actual. La composición íctica de estás cuencas es similar a la de los sistemas hídricos ubicados más al norte. Jenynsia multidentata es una especie con un amplia distribución en las cuencas de pendiente atlántica, como así también, en las cuencas ubicadas al norte. En el presente trabajo se investigó el patrón filogeográfico de Jenynsia multidentata, y se examinó la relación entre este patrón y la historia paleoclimática y geológica de la región. En el análisis del conjunto de poblaciones se encontró evidencia de una moderada diversidad genética, equilibrio demográfico, y una marcada estructura poblacional, en las poblaciones que ocupan los extremos de la distribución. Mientras que en las poblaciones que ocupan el centro de la distribución no se encontró diversidad genética presentando un único haplotipo. De los resultados obtenidos se infiere que la presencia de Jenynsia multidentata en el área es el resultado de procesos demográficos históricos independientes pero complementarios. A su vez, estos procesos podrían surgir de los cambios paleoclimáticos ocurridos durante el Cuaternario.

Crenicichla taikyra (Teleostei: Cichlidae), a new species of pike cichlid from the middle rio Paraná, Argentina.

Crenicichla taikyra, new species, is described from the middle río Paraná, Argentina. Crenicichla taikyra is distinguished from the other species of the genus by the following combination of characters: lower pharyngeal tooth plate stout, bearing molariform teeth, ascending arm of premaxilla longer than the dentigerous arm, posterior edge of preoperculum serrated, a well developed suborbital stripe, and absence of scattered dark dots on flanks. Molariform teeth on pharyngeal jaws is a derived character among Crenicichla species, however this character state has appeared several times in unrelated species.

Multilocus phylogeny of Crenicichla (Teleostei: Cichlidae), with biogeography of the C. lacustris group: species flocks as a model for sympatric speciation in rivers.

First multilocus analysis of the largest Neotropical cichlid genus Crenicichla combining mitochondrial (cytb, ND2, 16S) and nuclear (S7 intron 1) genes and comprising 602 sequences of 169 specimens yields a robust phylogenetic hypothesis. The best marker in the combined analysis is the ND2 gene which contributes throughout the whole range of hierarchical levels in the tree and shows weak effects of saturation at the 3rd codon position. The 16S locus exerts almost no influence on the inferred phylogeny. The nuclear S7 intron 1 resolves mainly deeper nodes. Crenicichla is split into two main clades: (1) Teleocichla, the Crenicichla wallacii group, and the Crenicichla lugubris-Crenicichla saxatilis groups ("the TWLuS clade"); (2) the Crenicichla reticulata group and the Crenicichla lacustris group-Crenicichla macrophthalma ("the RMLa clade"). Our study confirms the monophyly of the C. lacustris species group with very high support. The biogeographic reconstruction of the C. lacustris group using dispersal-vicariance analysis underlines the importance of ancient barriers between the middle and upper Paraná River (the Guaíra Falls) and between the middle and upper Uruguay River (the Moconá Falls). Our phylogeny recovers two endemic species flocks within the C. lacustris group, the Crenicichla missioneira species flock and the herein discovered Crenicichla mandelburgeri species flock from the Uruguay and Paraná/Iguazú Rivers, respectively. We discuss putative sympatric diversification of trophic traits (morphology of jaws and lips, dentition) and propose these species flocks as models for studying sympatric speciation in complex riverine systems. The possible role of hybridization as a mechanism of speciation is mentioned with a recorded example (Crenicichla scottii).

Redescription of Astyanax erythropterus (Holmberg, 1891) (Teleostei: Characiformes: Characidae) from La Plata basin in Argentina

Astyanax erythropterus (Holmberg, 1891) originally described on the basis of one juvenile, is redescribed herein based on juveniles and adults from the type-localiy. The species differs from its congeners by the combination of 11-13 transverse rows scales above lateral line and 8-10 rows below lateral line; 49-54 perforated scales in the lateral series; iii-v,38-42 anal-fin rays, and dorsal, anal and caudal fins vermilion red in juveniles. The vermilion red coloration of unpaired fins in juveniles of Astyanax is only known in A. correntinus.

Astyanax erythropterus (Holmberg, 1891) originalmente descripta sobre la base de un ejemplar juvenil, es redescripta en base a ejemplares juveniles y adultos de la localidad tipo. La especie se diferencia de sus congéneres por la combinación de 11-13 hileras de escamas transversas por encima de la línea lateral y 8-10 hileras debajo de la línea lateral; 49-54 escamas perforadas en las serie lateral; iii-v,38-42 radios en la aleta anal y juveniles con las aletas dorsal, anal y caudal rojo bermellón. Aletas impares rojo bermellón en ejemplares juveniles de Astyanax son solo conocidas en A. correntinus.

Crenicichla ypo (Teleostei: Cichlidae), a new species from the middle Paraná basin in Misiones, Argentina

A new species of Crenicichla, C. ypo, is described from the Arroyo Urugua-í, a left-hand tributary of the middle Paraná River, Misiones province, Argentina. The new species is recognized by 6 to 8 irregular blotches along the upper lateral line, absence of scattered dark spots on flanks, low number (47-55) of E1 scales, and a slightly prognathous lower jaw. Females have a distinctive coloration of the dorsal fin, with a wide black longitudinal stripe on the distal portion with an equally wide red stripe below it.

Una nueva especie de Crenicichla, C. ypo, es descripta de la cuenca del arroyo Urugua-í, tributaria de la margen izquierda del río Paraná medio, provincia de Misiones, Argentina. La nueva especie es reconocida por tener 6 a 8 manchas irregulares sobre la línea lateral superior, ausencia de pequeñas manchas oscuras dispersas sobre el flanco, bajo número (47-55) de escamas en la serie E1 y la quijada inferior levemente prognata. Las hembras tienen una coloración distintiva en la aleta dorsal con una banda ancha negra en la porción distal y otra roja del mismo ancho por debajo de esta.