“More than meets the eye”: phylogeographic inferences and remarkable cryptic diversity and in endemic catfish Parotocinclus (Loricariidae: Hypoptopomatinae) from neglected and impacted basins in South America

Genetic Diversity in Natural Populations of the Near-Threatened Species Lignobrycon myersi (Characiformes, Triportheidae): Implications for Species Conservation

The river basins of Brazil contain a highly diverse ichthyofauna of remarkable endemism, including several threatened species. Accordingly, Lignobrycon myersi is a fish species distributed only in a few rivers from the state of Bahia, northeastern Brazil. Since this species is classified as Near Threatened and is poorly studied, efforts to understand the genetic structure of populations and putative cryptic forms should help define efficient strategies of management and conservation. Herein, the molecular identification and the population genetic diversity of specimens of L. myersi across their range (Almada, Contas, and Cachoeira river basins) were assessed using mitochondrial markers (16S rDNA and D-Loop, respectively). The inferences based on phylogenetics, genetic distance, and species delimitation methods invariably identified all samples as L. myersi. In addition, sequencing of D-loop fragments revealed significant haplotype diversity and a considerable level of population genetic structure. Despite their geographic isolation, these data suggested that populations from Almada and Contas rivers represent a single evolutionary lineage that could be managed as a whole. In contrast, the population from Cachoeira River was highly differentiated from the others and should be managed separately as a unique and endemic unit, particularly focused on the conservation of native habitats.

Speciation in Coastal Basins Driven by Staggered Headwater Captures: Dispersal of a Species Complex, Leporinus bahiensis, as Revealed by Genome-wide SNP Data

Past sea level changes and geological instability along watershed boundaries have largely influenced fish distribution across coastal basins, either by dispersal via palaeodrainages now submerged or by headwater captures, respectively. Accordingly, the South American Atlantic coast encompasses several small and isolated drainages that share a similar species composition, representing a suitable model to infer historical processes. Leporinus bahiensis is a freshwater fish species widespread along adjacent coastal basins over narrow continental shelf with no evidence of palaeodrainage connections at low sea level periods. Therefore, this study aimed to reconstruct its evolutionary history to infer the role of headwater captures in the dispersal process. To accomplish this, we employed molecular-level phylogenetic and population structure analyses based on Sanger sequences (5 genes) and genome-wide SNP data. Phylogenetic trees based on Sanger data were inconclusive, but SNPs data did support the monophyletic status of L. bahiensis. Both COI and SNP data revealed structured populations according to each hydrographic basin. Species delimitation analyses revealed from 3 (COI) to 5 (multilocus approach) MOTUs, corresponding to the sampled basins. An intricate biogeographic scenario was inferred and supported by Approximate Bayesian Computation (ABC) analysis. Specifically, a staggered pattern was revealed and characterized by sequential headwater captures from basins adjacent to upland drainages into small coastal basins at different periods. These headwater captures resulted in dispersal throughout contiguous coastal basins, followed by deep genetic divergence among lineages. To decipher such recent divergences, as herein represented by L. bahiensis populations, we used genome-wide SNPs data. Indeed, the combined use of genome-wide SNPs data and ABC method allowed us to reconstruct the evolutionary history and speciation of L. bahiensis. This framework might be useful in disentangling the diversification process in other neotropical fishes subject to a reticulate geological history.

A new species of Parotocinclus (Loricariidae: Hypoptopomatinae) from the rio Pardo basin, Bahia State, Brazil, with comments on the sexually dimorphic traits of the nares and olfactory lamellae

A new species of Parotocinclus is described from lower rio Pardo basin, Bahia, Brazil. The new species differs from the majority of its congeners by the presence of a rudimentary or vestigial adipose fin, restricted to one to three small unpaired plates on the typical location of the fin. The new species differs from congeners that lack a well-developed adipose fin, and also from various other congeners, by a series of features including the absence of unicuspid accessory teeth and abdomen completely covered by plates similar in size. Additionally, mature males of the new species possess hypertrophied and a higher number of olfactory lamellae, when compared to similar-sized or even larger females. Hypertrophied and higher number of olfactory lamellae in males is shared with the congeners from the north-eastern Mata Atlântica freshwater ecoregion examined to the feature.