Color patterns of the body are commonly used to distinguish and identify species of Trichomycterus. Therefore, variation in color pattern in a population can cause doubt concerning species identification. With the purpose to test the hypothesis of high variation in color pattern of Trichomycterus davisi (Haseman, 1911), 118 specimens were collected in a stream of a private Ecological Park in southern Brazil, of which 88 were used in the morphological analysis and 30 for DNA barcoding analysis. Three phenotypic classes were determined analyzing the distribution, size and shape of dark brown spots and blotches. The results of morphometric analysis indicate a tendency of association of those pigmentation patterns with the standard length, evidencing ontogenetic variation of color pattern in the species. The results of K2P intraspecific genetic distance (<0.72%), haplotypes network and Bayesian phylogenetic tree corroborate the existence of only one species with a high variable color pattern.
Fishes were collected at 36 sites in first order streams of Tibagi River basin, Paraná state, Brazil. A total of 2,669 individuals belonging to 47 species of 13 families and six orders were collected. The number of collected species represented 95.9% of the expected number of species for the studied area as estimated by Chao 1, and 93.4% by ACE, indicating an effective sampling. The highest richness was recorded in the tributaries at the lower region (Zone III) of the Tibagi River basin, with 33 species, including 16 species not found in the other regions of the basin. In the streams of the middle and upper regions (Zones II and I) each presented less richness, with 10 (two exclusive) and 25 (11 exclusive) species, respectively. This study shows a high geographic variation in the composition of fish fauna among zones, maybe related to historical and/or ecological influences.
ABSTRACT. Most studies of diversity and genetic structure in neotropical fish have focused on commercial species from large rivers or their reservoirs. However, smaller tributaries have been identified as an important alternative migratory route, with independent pools of genetic diversity. In this context, the present study aimed to evaluate genetic diversity and structure in five neotropical fish species from a region of Laranjinha River in the upper Paraná River basin. PCR-RAPD (random amplified polymorphic DNA) markers were used to characterize around 40 individuals of each species distributed upstream and downstream of Corredeira Dam that interrupts the river. The descriptive index of genetic diversity (P = 30.5-82%; H E 0.122-0.312) showed that the populations have acceptable levels of genetic diversity. The values for Nei's genetic distance (D N min 0.0110 and max 0.0306) as well as the genetic structure index and the analysis of molecular variance (AMOVA, ϕ ST min 0.0132 and max 0.0385) demonstrated low, but significant levels of genetic structure. Bayesian analysis of assignment found two k clusters, including several individuals with mixed ancestry for all populations from the five species analyzed. These findings along with historical data on rainfall and the low dimensions of the dam studied here support the hypothesis that periodic floods enable the transit of individuals between different localities mitigating the differentiation process between populations.
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