Astyanax xavante, a new species of characid from middle rio Araguaia in the Cerrado region, Central Brazil (Characiformes: Characidae)

Abstract

Astyanax xavante is described from a creek of the middle rio Araguaia drainage located in the Cerrado region of the Brazilian Central Plateau. The new species is distinguished from congeners by the combination of pigmentation, morphometric, meristic, morphologic, and tooth features. Ecological notes for A. xavante are included.Astyanax xavante é descrita de um córrego da drenagem do médio rio Araguaia, localizado em área de Cerrado do planalto do Brasil Central. A nova espécie se distingue das demais do gênero pela combinação de caracteres pigmentares, morfométricos, merísticos, morfológicos e dentários. Notas ecológicas para A. xavante são incluídas.

Comparative cytogenetics in Astyanax (Characiformes: Characidae) with focus on the cytotaxonomy of the group

“…According to Garutti & Venere (2009), the last complete Astyanax revision founded on morphological characteristics was conducted by Eigenmann (1921,1927), and the author who most recently treated this genus as a whole was Géry in 1977, who essentially followed Eigenmann. Astyanax is one of the most common genera in the freshwaters of Neotropical basins (Bertaco & Garutti, 2007), and is non-monophyletic (Weitzman & Fink, 1983;Garutti & Venere, 2009;Mirande, 2010;Oliveira et al, 2011).…”

Downstairs gene flow: the effects of a linear sequence of waterfalls on the only population of the endangered minnow Astyanax xavante

“…Astyanax xavante Garutti & Venere (Characidae) is a minnow species endemic to Avoadeira (Fig. ), a steep brook of 11·7 km in length that is located in the Araguaia Basin within a nature park (Parque Estadual da Serra Azul) in the state of Mato Grosso, Brazil.…”

“…None of these species can climb the Pé‐da‐Serra Waterfall and are therefore not found upstream of this barrier. Astyanax xavante density dramatically decreases downstream of the Pé‐da‐Serra waterfall with decreasing distance to the Araguaia River, and this species is not found in the lower 1·5 km of the brook (Garutti & Venere, ). The geographic restriction of A. xavante has most likely persisted due to barrier 3, which blocks the upstream migration of competitors and predators and functions as a biological barrier to the downstream distribution of A. xavante to the Araguaia River and its other tributaries.…”

“…Previous studies by Garutti & Venere () have revealed some of the biological and ecological characteristics of A. xavante : regardless of the season (wet or dry), (1) the species is omnivorous, (2) females and males can be found with mature gonads at a very young age (at standard lengths, L S , c . 26 mm for both females and males) throughout the year, (3) fish predators and competitors act as biological barriers, (4) natural groups remain isolated from predators and competitors by a waterfall c .…”

“…The endemism of this species to such a small geographical area, the inability of this species to spread to other tributaries and the proximity of this brook to urban environments make A. xavante a candidate endangered species. Previous studies by Garutti & Venere (2009) have revealed some of the biological and ecological characteristics of A. xavante: regardless of the season (wet or dry), (1) the species is omnivorous, (2) females and males can be found with mature gonads at a very young age (at standard lengths, L S , c. 26 mm for both females and males) throughout the year, (3) fish predators and competitors act as biological barriers, (4) natural groups remain isolated from predators and competitors by a waterfall c. 30 m high (Pé-da-Serra) and (5) A. xavante is distributed throughout the most rugged portion of the brook, suggesting that there may be micro-isolations between different groups of fish. This set of biological and ecological characteristics provides a good context in which to investigate the effect of micro-barriers on genetic variation and gene flow between different sampling sites in a species with a highly restricted distribution to a short and discrete gradient of environmental factors.…”