Saturday, June 9, 2012

[Ichthyology • 2008] Taxonomy of Ixinandria Isbrücker & Nijssen (Loricariidae: Loricariinae) based on morphological and molecular data

Ixinandria steinbachi (Regan, 1906)


The genus Ixinandria was described in 1979 to include I. steinbachi from the upper río Juramento in northern Argentina and I. montebelloi from the upper río Bermejo in southern Bolivia. We used a multivariate morphometric analysis (Principal Components Analysis) and a molecular comparison of the Cytochrome Oxidase I gene to investigate variation among distinct populations from the known distribution range of both species. We conclude that the populations are not significantly distinct and do not deserve separate species recognition, and we place I. montebelloi in the synonymy of I. steinbachi.

Key words: Neotropical, Synonymy, río Juramento; río Bermejo; río Pilcomayo.


Ixinandria Isbrücker & Nijssen, 1979 was described to accommodate two species, Loricaria steinbachi Regan, 1906, the type species, and Canthopomus montebelloi Fowler, 1940. Ixinandria was considered by the authors to be very close to Rineloricaria Bleeker, 1862, and diagnosed on the basis of the absence of abdominal plates, the degree of development of odontodes, and the shape of the head in sexually mature males (Isbrücker, 1979). Isbrücker (1979) placed Ixinandria in the subtribe Rineloricariina, which also included Spatuloricaria Schultz, 1944, Dasyloricaria Isbrücker & Nijssen, 1979, and Rineloricaria. The validity of Ixinandria or its relationships with other loricariines were never further investigated.

Loricaria steinbachi was placed in the subgenus Rhineloricaria by Eigenman (1911), a few years after its original description, and remained as Rineloricaria until it was moved to Ixinandria by Isbrücker (1979). On the other hand, Canthopomus montebelloi remained mostly unnoticed until Isbrücker's (1979) new combination by its inclusion in the genus Ixinandria.

Loricaria steinbachi was described from the río Juramento basin, a tributary to the río Salado drainage, near Cachi, Salta, Argentina, at an elevation of 2,500 meters above sea level, based on three specimens. Isbrücker (1979) later designated the largest of those three syntypes as the lectotype. Canthopomus montebelloi was described from tributaries of the upper río Bermejo at the Monte Bello Farm in Tarija, southern Bolivia, based on the holotype only, also from high elevation.

The validity of those species was later questioned by Isbrücker (1981a), who suggested that they might represent a single species. In this paper, we revised the two species and placed Ixinandria montebelloi in the synonymy of I. steinbachi, based on both morphological and molecular evidence.

Rodriguez, Mónica S.; Cramer, Christian A.; Bonatto, Sandro L.; Reis, Roberto E. 2008. Taxonomy of Ixinandria Isbrücker & Nijssen (Loricariidae: Loricariinae) based on morphological and molecular data. Neotropical Ichthyology. 6 (3): 367–378. DOI: 10.1590/S1679-62252008000300010