Species delimitation reveals an underestimated diversity of Andean catfishes of the family Astroblepidae (Teleostei: Siluriformes)

Fish databases for improving their conservation in Colombia

Progress in the acquisition of massive sets of molecular data and in the bioinformatic capabilities for their processing have revolutionised species identification, filling gaps in crucial areas such as taxonomy, phylogenetic inference, biogeography, and even biodiversity conservation. Advanced DNA sequencing and metabarcoding have uncovered previously hidden diversity, although their effectiveness is highly dependent on the accuracy of reference DNA databases at local and regional scales. The compilation of information on freshwater fishes from the Magdalena River basin is an important milestone in improving our knowledge of the genetic and taxonomic diversity of a highly endemic region in the Neotropical context. Here, we share DNA data from 1,270 specimens representing 183 species, cross-referenced with complete collecting and catalogue information, along with high resolution photographs of voucher specimens when alive. This collection of multiple sources of information based on fish specimen records not only contributes to future research on Neotropical fish systematics and ecology, but also to conservation decisions in one of the South American rivers with a highest level of endemism.

Integrative morphological, cytogenetic and molecular characterization of the Andean climbing catfish Astroblepus mindoensis (Regan, 1916) (Siluriformes:Astroblepidae)

Astroblepus species, commonly known as Andean climbing catfish, exhibit a unique challenge in species delimitation, leading to ongoing taxonomic debates. Here we report data on Astroblepus mindoensis, a vulnerable species endemic to Ecuador, obtained by an integrative approach that includes cytogenetic analysis, molecular identification of the specimens, and recording of morphological and morphometric characters useful for species diagnosis. Thus, this study aimed to associate the karyotype data of the specimens analyzed with morphological and molecular characters, improving and expanding the existing taxonomic information, thus contributing to the systematics of the species. Our morphology results, unlike Regan's original description, which is brief and ambiguous, provide a more detailed morphometric and meristic description. Molecular phylogenetic reconstruction and genetic distance based on a fragment of the cytochrome c oxidase subunit I (COI) showed that our samples constitute a well-supported and monophyletic clade within the A. grixalvii species complex. The cytogenetic analysis identified distinct chromosomal markers, including a single cluster of major ribosomal genes (on chromosome pair 3) and of minor ribosomal genes (on chromosome pair 12) with their localization differing from those reported in other Astroblepus species analyzed. Additionally, the presence of a heteromorphic chromosome pair in males suggests the presence of an XX/XY sex-determination system that has not been identified in other congeneric species. Further investigation is necessary to determine if these chromosomes are associated with the accumulation of repeated sequences, as typically occurs with sex chromosomes, and to assess their presence in other species of the genus.

Phylogeographic patterns of Cyphocharax from trans-Andean rivers and northward expansion to lower Central America (Teleostei, Curimatidae)

Phylogenetic analyses of mitochondrial and nuclear data of 31 specimens of Cyphocharax from trans-Andean rivers support the presence of one lineage of Cyphocharax aspilos in Lago Maracaibo and three cryptic lineages of Cyphocharax magdalenae: (1) Cauca-Magdalena and Ranchería, (2) León and Atrato, and (3) Chucunaque-Tuira, Santa María, and Chiriquí basins of Central America. Results suggest that the Serranía del Perijá facilitated Late Miocene cladogenetic events, whereas post-Isthmian C. magdalenae expansion was enabled by gene flow across the lower Magdalena valley and Central American lowlands. Time-calibrated phylogenetics indicate that the C. magdalenae colonized lower Central America in the Pliocene (3.7 MYA; Ma), the divergence Atrato-Magdalena occurred in Late Pliocene (3.0 Ma) and the split Ranchería-Magdalena during the Middle Pleistocene (1.3 Ma). Updated geographic distribution data support the hypothesis that the Cordillera de Talamanca functions as a barrier to northward expansion of C. magdalenae in Central America.

New records of native and introduced fish species in a river basin of Western Ecuador, the Chocó-Darien Ecoregion, using DNA barcoding

DNA barcoding, based on mitochondrial markers, is widely applied in species identification and biodiversity studies. The aim of this study was to establish a barcoding reference database of fishes inhabiting the Cube River from Western Ecuador in the Chocó-Darien Global Ecoregion (CGE), a threatened ecoregion with high diversity and endemism, and evaluate the applicability of using barcoding for the identification of fish species. Barcode sequences were obtained from seven orders, 17 families, 23 genera and 26 species, which were validated through phylogenetic analysis, morphological measurements, and literature review. Our results showed that 43% of fish species in this region are endemic, confirmed the presence of known species in the area, and included the addition of three new records of native (Hoplias microlepis, Rhamdia guatemalensis and Sicydium salvini) and an introduced species (Xiphophorus maculatus) to Ecuador. In addition, eight species were barcoded for the first time. Species identification based on barcoding and morphology showed discrepancy with species lists from previous studies in the CGE, suggesting that the current baseline of western fishes of Ecuador is still incomplete. Because this study analyzed fishes from a relatively small basin (165 km2), more molecular-based studies focusing on fish are needed to achieve a robust sequence reference library of species inhabiting Western Ecuador. The new sequences of this study will be useful for future comparisons and biodiversity monitoring, supporting the application of barcoding tools for studying fish diversity in genetically unexplored regions and to develop well-informed conservation programs.

Conservation threats and future prospects for the freshwater fishes of Ecuador: A hotspot of Neotropical fish diversity

Freshwater fish communities in Ecuador exhibit some of the highest levels of diversity and endemism in the Neotropics. Unfortunately, aquatic ecosystems in the country are under serious threat and conditions are deteriorating. In 2018-19, the government of Ecuador sponsored a series of workshops to examine the conservation status of Ecuador's freshwater fishes. Concerns were identified for 35 species, most of which are native to the Amazon region, and overfishing of Amazonian pimelodid catfishes emerged as a major issue. However, much of the information needed to make decisions across fish groups and regions was not available, hindering the process and highlighting the need for a review of the conservation threats to Ecuador's freshwater fishes. Here, we review how the physical alteration of rivers, deforestation, wetland and floodplain degradation, agricultural and urban water pollution, mining, oil extraction, dams, overfishing, introduced species and climate change are affecting freshwater fishes in Ecuador. Although many of these factors affect fishes throughout the Neotropics, the lack of data on Ecuadorian fish communities is staggering and highlights the urgent need for more research. We also make recommendations, including the need for proper enforcement of existing environmental laws, restoration of degraded aquatic ecosystems, establishment of a national monitoring system for freshwater ecosystems, investment in research to fill gaps in knowledge, and encouragement of public engagement in citizen science and conservation efforts. Freshwater fishes are an important component of the cultural and biological legacy of the Ecuadorian people. Conserving them for future generations is critical.

Fish Ecology of the Alto Madre de Dios River Basin (Peru): Notes on Electrofishing Surveys, Elevation, Palm Swamp and Headwater Fishes

Our study analyzes the distribution of fish communities related to the environmental variables of the Alto Madre de Dios River, an Andean-Amazon watershed of southern Peru, between 300 and 2811 m a.s.l. within the Manu Biosphere Reserve. We provide new ecological and diversity data on fishes for these poorly studied rivers and new data for palm swamp habitats. With electric fishing techniques, we collected a total of 1934 fish specimens belonging to 78 species, 42 genera and 15 families. To assess main patterns of diversity we combined SIMPER and ANOSIM with canonical correspondence analysis to obtain an overview of the community structure of fish and their distribution related to aquatic habitats. Our results show an important shift on fish diversity at 700 m a.s.l. separating headwater and middle-lowland communities. Electrofishing was a hindrance due to the depth, flow and low conductivity of the rivers, but also allowed us to capture fish not observed with other techniques. We also compared the use of elevation with slope as an alternative variable for statistical analysis. Our results show that slope offers a solid and equivalent explanation for fish distribution variability, avoids redundance, and instead of giving geographical data offers ecologically solid information.

Cryptic speciation in populations of the genus Aphyocharax (Characiformes: Characidae) from eastern Amazon coastal river drainages and surroundings revealed by single locus species delimitation methods

Abstract Recent studies in eastern Amazon coastal drainages and their surroundings have revealed new fish species that sometimes exhibit little morphological differentiation (cryptic species). Thus, we used a DNA-based species delimitation approach to test if populations showing the morphotype and typical character states of the Aphyocharax avary holotype correspond either to A. avary or A. brevicaudatus, two known species from the region, or if they form independent lineages, indicating cryptic speciation. WP and GMYC analyses recovered five lineages (species) in the ingroup, while a bPTP analysis delimited three lineages. ABGD analyses produced two possible results: one corroborating the WP and GMYC methods and another corroborating the bPTP method. All methods indicate undescribed cryptic species in the region and show variation from at least 1 to 4 species in the ingroup, depending on the approach, corroborating previous studies, and revealing this region as a possible hotspot for discovering undescribed fish species.