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Abundance and mass of R. giarettai and environmental variables measured in plots in Dam Reservoirs (DR) (n=39) and Free Flowing Waters (FFW) (n=60 plots) along Veredas (Palm Grove Marshes) in Uberlândia (MG), Brazil

Abundance and mass of R. giarettai and environmental variables measured in plots in Dam Reservoirs (DR) (n=39) and Free Flowing Waters (FFW) (n=60 plots) along Veredas (Palm Grove Marshes) in Uberlândia (MG), Brazil

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We present data on the habitat, density, and spatial distribution of Rivulus giarettai, and discuss some biotic and abiotic variables related to its abundance in Free Flowing Waters (FFW) and Dam Reservoirs (DR) in palm grove (Mauritia flexuosa) marshes (Veredas) in Uberlândia, Minas Gerais, southeastern Brazil. The mean density (individuals/plot)...

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... However, species which inhabit degraded and fragmented systems would seem to be most vulnerable to fire and firerelated disturbances (Dunham et al. 2003). In this study, a fire was observed in June, but it seemed to have no effect on the variables studied here, as no significant changes were observed immediately after the fire on the population structure of Melanorivulus giarettai (Costa 2008) from Bvereda^habitats (Oliveira et al. 2012). As pointed out by Minshall et al. (2001), fire may affect aquatic organisms over the long term, suggesting that this population should be monitored over a long time course to determine the real effects of fire and other significant environmental disturbances. ...
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Species of Melanorivulus present behaviour and physiological traits that allow them to live in marginal aquatic habitats. In particular, Melanorivulus rossoi is a small nonannual fish only known from its type locality in the Brazilian Cerrado. In this study, we aimed to characterize the distribution and temporal variation in body size, sex ratio, density, length-weight relationship (LWR) and condition factor (CF) of M. rossoi in its natural habitat. To accomplish this, fish samples were taken monthly for a year using sieve nets every 30 min. Body size of males and females increased throughout the year until early summer. LWR was significant, and general coefficient of determination (r²) was 92%. Juveniles showed negative allometric growth, but adults showed positive allometric growth. Both sexes presented the same tendency of temporal variation in CF, with lower values in October and January and peaks in September and February. Fire occurred in June, but no difference in population parameters was observed after this event. A decrease in the abundance of Melanorivulus was related with an increase in the abundance of Erythrinidae juveniles. This might be explained by an increased predation of this species over the M. rossoi individuals, when the population was reduced to about 30% of that in the previous months. We report four new locations where this species was recorded; thus, similar to most Rivulidae members, M. rossoi has a restricted distribution area and is threatened with extinction. Therefore, our results may be useful in developing management strategies aimed at conservation of this species and its habitat in Brazil.
... The region comprising the Cerrado savannas of central Brazil has been considered among the most important biodiversity hotspots in the world (Myers et al. 2000), although many organisms endemic to this region were insufficiently sampled and poorly known until recent years . A typical component of the Cerrado fauna is the killifish genus Melanorivulus Costa, 2006, with species inhabiting the Veredas, a Cerrado ecosystem consisting of small streams running in shallow valleys, often exhibiting the buriti-palm Mauritia flexuosa along their banks (e.g., Costa 2007a; Oliveira et al. 2012). Probably as a consequence of small size, usually not surpassing 45 mm of total length, species of Melanorivulus occurring in this ecosystem were not represented in collections until recent years, with the great majority of the approximately 40 species occurring in the central Brazilian Cerrado being described only after 2005 (e.g., Costa 2012;Costa et al. 2016). ...
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... With great occurrence of endemic taxa, biogeographical relationships of organisms inhabiting these savannas are still poorly known (e.g., silva & Bates, 2002), as well as biological inventories in past decades have neglected some habitats, making biodiversity underestimated until recent years. This is the case of the killifish genus Melanorivulus Costa, 2006, with most species only living in shallow marginal parts of small streams draining South America savannas (Costa, 1995(Costa, , 2006oliveira et al., 2012), habitats that were poorly sampled in fish collections until recently. As a consequence, only two of the about 35 valid species of Melanorivulus were first described before 1989, in spite of the huge area occupied by this genus, between the Oiapoque river basin in northern Brazil, about 4º N, and the Uruguay river basin in northern Argentina, about 27º S, and between the Paraguay river basin in eastern Bolivia, about 60º W, and the coastal plains of north-eastern Brazil, about 37º W (e.g., Costa, 1995;Bragança et al., 2012;Costa et al., 2015). ...
... Like species of the closely related genera Anablepsoides and Atlantirivulus, species of Melanorivulus typically inhabits shallow marginal areas close to streams, about 5 to 30 cm deep (Costa, 1995(Costa, , 2006. However, differently from species of those two genera that are found in dense rain forests, species of Melanorivulus inhabit savanna-like environments (Costa, 2007b(Costa, , 2011oliveira et al., 2012). Most species are endemic to the Cerrado savanna of central Brazil and the adjacent Cerrado-Amazon ecotone (Costa, 1995(Costa, , 2005(Costa, , 2012a. ...
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This study comprises the first molecular phylogeny of Melanorivulus, a genus of small killifishes inhabiting shallow streams draining South American savannas, using segments of the mitochondrial genes 16S and ND2 and the intron 1 of the nuclear S7 gene, total of 2,138 bp, for 26 taxa. Monophyly of the genus is highly supported and some clades previously diagnosed on the basis of colour patterns are corroborated. A biogeographical analysis using event-based methods indicated that the most recent common ancestor of Melanorivulus occupied a region comprising the savannas of the eastern Amazon and the ecotone Amazon-Cerrado, and the present day distribution has been shaped by a series of dispersal and vicariance events through areas today including the upland Cerrado and the lowland Pantanal. The presence of a broad stripe of dense rain forest today separating the savannas of the eastern Amazon, inhabited by M. schuncki, from the savannas located south of the Amazon, from where a clade comprising all other species of the genus is endemic, is regarded as evidence of possible geographical expansion of Melanorivulus lineages through savanna areas during past cooler and drier periods, when South American grasslands and savannas expanded and rain forests were restricted to small areas.