Abstract
Pareiorhaphis hystrix is a widely distributed species, occurring in the upper and middle Uruguay River and in the Taquari River basin, Patos Lagoon system, southern Brazil. Morphological variation has been detected throughout the distribution of P. hystrix, and this work seeks to test the conspecific nature of populations in several occurrence areas. Specimens from six areas in the Uruguay River basin and three in the Taquari River basin were compared. Variance analysis (ANOVA) was performed for the meristic data, and Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) were conducted for morphometric data. Molecular analyses used coI, cytb, 12S and 16S mitochondrial genes, examining nucleotide diversity, haplotype diversity, genetic distance, and delimitation of possible multiple species through the Generalized Mixed Yule Coalescent (GMYC) method. Phylogenetic relationships of studied populations were also investigated through Bayesian inference. While PCA indicated a tendency of overlap between areas, ANOVA and LDA detected a subtle differentiation between populations from the two hydrographic basins. Yet, both latter analyses recovered the population from Pelotas River, a tributary to Uruguay River, as more similar to populations from Taquari River, which is congruent to morphological observations of anterior abdominal plates. The molecular data indicated a nucleotide diversity lower than the haplotypic diversity, suggestive of recent expansion. The concatenated haplotype network points to slight differentiation between areas, with each locality presenting unique and non-shared haplotypes, although with few mutational steps in general. The species delimitation by coalescence analysis suggested the presence of a variable number of OTUs depending on the inclusion or exclusion of an outgroup. In general, the morphological data suggest a subtle variation by river basin, while the genetic data indicates a weak population structuration by hydrographic areas, especially the Chapecó and Passo Fundo rivers. However, there is still not enough differentiation between the specimens to suggest multiple species. The iterative analyses indicate that Pareiorhaphis hystrix is composed of a single, although variable, species.
Highlights
Among catfish families, Loricariidae is the most diverse with above 1,000 species currently valid [1], a number that continues to raise steadily
The concept of iterative taxonomy is used in the sense of Yeates et al [11], where species boundaries are treated as hypotheses to be tested by the comparison of multiple lines of evidence analyzed iteratively, in opposition to integrative taxonomy, where different sources of evidence should be integrated and analyzed together
These odontodes vary in size, thickness, density, direction, and position on the sides of the head, while the fleshy lobe varies in thickness and shape (Fig 4)
Summary
Loricariidae is the most diverse with above 1,000 species currently valid [1], a number that continues to raise steadily. Fishes in this family, popularly known as Cascudos in Brazil, are widely distributed in neotropical freshwaters from the Pacific drainages of southern Costa Rica to northeastern Argentina, with six subfamilies currently recognized [1, 2]. Pareiorhaphis currently has 26 valid species [5] and is endemic to Brazil, occurring in main coastal river drainages of south, southeast and northeast Brazil, in addition to eastern versants tributaries to the Paranaand São Francisco rivers [5, 6]. Even the hypertrophied cheek odontodes of adult males, which represent a synapomorphy for the genus [8] are highly variable in size, thickness, density, direction, and position on the sides of the head
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