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Catfishes (Teleostei: Siluriformes) are a highly diverse order within Ostariophysi that is distributed worldwide. At the base of this clade emerge three lineages with well-defined monophylies: Diplomystidae, Loricarioidei, and Siluroidei. Morphological phylogeny studies place the Diplomystidae as the earliest branching of these three lineages, but studies based on molecular phylogenetics consistently find the fast-evolving Loricarioidei instead. The high lineage evolutionary rate heterogeneity in this order and the fact that the lineage placed closest to the root in the molecular phylogenies is fast evolving, including many long branches, raises the possibility that the discrepancy between morphological and molecular phylogenies may be the result of a long branch attraction inference artifact. We test this hypothesis by using a 10-gene dataset to evaluate the arrangement of the three main siluriform lineages, and apply the LS 3 and LS 4 taxon sequence subsampling methods to reduce evolutionary rate heterogeneity among lineages. The initial and complete dataset supports the basal branching of Loricarioidei as in all previous molecular phylogenies, but once lineage rate heterogeneity is reduced with LS 3 or LS 4 through the removal of sequences disrupting homogeneity, the phylogeny shows Diplomystidae as the earliest branching group, with high supports, as proposed by morphological phylogeny. The result obtained with LS 3 , however, introduces the misplacement of one of the species with the highest amount of missing data, Scoloplax sp. Because the sequence sub-selection criterion of LS 4 has been optimized to reduce data removal, the phylogeny resulting from the LS 4 -processed data is in agreement with the known intra-lineage relationships in addition to supporting the morphologically-based rooting hypothesis. Our results are the first instance in which a consensus between molecular and morphological phylogeny is reached concerning the root of this order. [ABSTRACT FROM AUTHOR]

Following study of the external morphology and its unmatched variability throughout ontogeny and a re-examination of selected morphological characters based on many specimens of diplomystids from Central and South Chile, we revised and emended previous specific diagnoses and consider Diplomystes chilensis, D. nahuelbutaensis, D. camposensis, and Olivaichthys viedmensis (Baker River) to be valid species. Another group, previously identified as Diplomystes sp., D. spec., D. aff. chilensis, and D. cf. chilensis inhabiting rivers between Rapel and Itata Basins is given a new specific name (Diplomystes incognitus) and is diagnosed. An identification key to the Chilean species, including the new species, is presented. All specific diagnoses are based on external morphological characters, such as aspects of the skin, neuromast lines, and main lateral line, and position of the anus and urogenital pore, as well as certain osteological characters to facilitate the identification of these species that previously was based on many internal characters. Diplomystids below 150 mm standard length (SL) share a similar external morphology and body proportions that make identification difficult; however, specimens over 150 mm SL can be diagnosed by the position of the urogenital pore and anus, and a combination of external and internal morphological characters. According to current knowledge, diplomystid species have an allopatric distribution with each species apparently endemic to particular basins in continental Chile and one species (O. viedmensis) known only from one river in the Chilean Patagonia, but distributed extensively in southern Argentina.

Biotic homogenization in freshwater ecosystems is a growing concern among conservation biologists. Recent phylogeographic data has shown low genetic structure between some basins from Central Chile, suggesting that either current dispersal through irrigation canals or incomplete lineage sorting due to recent divergence might explain the observed patterns. However, these hypotheses remain untested despite their potential implications for freshwater biodiversity and conservation. We used a statistical, model-based framework (approximate Bayesian computation) to investigate the relative support for each of these hypotheses in the freshwater catfish Diplomystes cf. camposensis , an endangered species from Central Chile. Our results show strong support for the model involving current migration between basins, and rejected the model of recent divergence without migration. These results strongly suggest that irrigation canals are facilitating the dispersal between basins, posing a serious threat to biodiversity in Central Chile, an area considered a biodiversity hotspot. Finally, these results highlight the utility of model-based approaches for determining demographic processes with potential conservation implications, even with the lack of extensive molecular data. [ABSTRACT FROM AUTHOR]

Highlights: [•] First molecular phylogenetic reconstruction within the ancient catfish family Diplomystidae. [•] Results show inconsistencies with traditional systematic view. [•] Phylogeographic patterns suggest that different processes have occurred to populations from Pacific and Atlantic basins. [•] High inter-basin genetic structure suggests conservation efforts at the basin level. [Copyright &y& Elsevier]

The Rufous Tree Rat, Diplomys labilis, is known to range geographically from Central Panamá to Colombia and probably Ecuador. It occurs in a variety of habitat types where it moves by the branches in the high canopy at night. We report the Rufous Tree Rat for Costa Rica, ranging outside its geographical distribution about 490 km west from its type locality. [ABSTRACT FROM AUTHOR]

The article features the Diplomystes camposensis Arratia, 1987. The common name in Spanish is Tollo. It is endemic to the Valdivia River basin in southern Chile, inhabiting high gradient parts of Cruces, Enco, San Pedro and Calle Calle rivers. It can be identified with its elongate diplomystid, nostrils surrounded by large skin folds, and a round epidermal papillae on barbel. It prefers rithral areas with velocity <0.6 ms-1 and boulder substrates, and absent in potamal areas. It has a sexual maturity of 12 centimeter total length, and by January the larvae move from shallow riparian riffles to shallow pools with low current velocity. The threats include habitat loss and fragmentation due to anticipated dams construction and introduced salmonids.

Following study of the external morphology and its unmatched variability throughout ontogeny and a re-examination of selected morphological characters based on many specimens of diplomystids from Central and South Chile, we revised and emended previous specific diagnoses and consider Diplomystes chilensis , D. nahuelbutaensis , D. camposensis , and Olivaichthys viedmensis (Baker River) to be valid species. Another group, previously identified as Diplomystes sp., D . spec., D . aff. chilensis , and D . cf. chilensis inhabiting rivers between Rapel and Itata Basins is given a new specific name ( Diplomystes incognitus ) and is diagnosed. An identification key to the Chilean species, including the new species, is presented. All specific diagnoses are based on external morphological characters, such as aspects of the skin, neuromast lines, and main lateral line, and position of the anus and urogenital pore, as well as certain osteological characters to facilitate the identification of these species that previously was based on many internal characters. Diplomystids below 150 mm standard length (SL) share a similar external morphology and body proportions that make identification difficult; however, specimens over 150 mm SL can be diagnosed by the position of the urogenital pore and anus, and a combination of external and internal morphological characters. According to current knowledge, diplomystid species have an allopatric distribution with each species apparently endemic to particular basins in continental Chile and one species ( O. viedmensis ) known only from one river in the Chilean Patagonia, but distributed extensively in southern Argentina., Competing Interests: The authors declare there are no competing interests.

Carlos P. Muñoz-Ramírez, Evelyn Habit, Peter J. Unmack, Jerald B. Johnson, and Pedro F. Victoriano (2016) Despite the fundamental importance of the family Diplomystidae for understanding catfish evolution, its species are poorly known and most of them endangered. Diplomystes camposensis , restricted to a single river basin in southern Chile, is perhaps the most vulnerable species due to its small geographic range and imminent habitat alterations by dam constructions. Using mitochondrial DNA sequences, we describe the genetic diversity across its entire distribution in the Valdivia basin and test hypotheses related to the impact of glacial cycles on the genetic diversity and structure. We found that Diplomystes camposensis has low genetic diversity and structure across the entire Valdivia basin along with a pattern of decreasing nucleotide and haplotype diversity from West to East. Demographic analyses showed evidence of population expansion in agreement with the glaciated history of the basin. Analyses of population structure showed no evidence of population subdivision. However, coalescent analyses indicated that very recent subdivision (in the last 50 years) cannot be ruled out. Low genetic diversity and genetic structure across the entire basin suggest that the species might be highly vulnerable to habitat fragmentation. Thus, the imminent construction of hydropower dams represents a serious threat to its conservation. Our results suggest that the low genetic diversity can be the product of the glaciated history of the basin, although the influence of species-specific biological traits may also add to this condition. Despite the overall low genetic diversity, higher diversity was found in the central portion of the basin suggesting high priority of conservation for this area as it might be used as a source population in case translocations are required among potential management plans.