INTRODUCTION

The genus Hypostomus Lacepède, 1803 (Loricariidae) is one of the most diverse and complex groups of South American freshwater catfishes, having 163 nominal species. As is the case with other Neotropical groups studied in the two past centuries, the species of Hypostomus have been only briefly and incompletely described, with original descriptions often useless for species identification. This, allied with a very limited knowledge on general distribution patterns in South American basins, has resulted in a great number of misidentifications throughout the taxonomic and fisheries literature.

At the present, no synapomorphy has been identified to diagnose the genus Hypostomus. Furthermore, there are few studies describing in detail the skeleton of any member of family Loricariidae. The one such study involving an Hypostomus species was not placed within a phylogenetic context.

The upper Rio Paraná region of Brazil is an area of demonstrated ichthyological endemism. This fact together with the demonstrated limited home ranges of many species of stream fishes, and their series of adaptations to this specific type of environment make it likely that the majority of the species of the genus Hypostomus occurring in streams of the upper Rio Paraná are restricted to that environment and likely demonstrate small scale endemism. To date 20 nominal species of Hypostomus were described from the upper Rio Paraná, and another 12 have been mentioned as occurring in that region by various authors. Our problem was to try to determine the number of recognizable species of the genus in this region and which of the various available names was appropriate for each form.

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Study Area

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OBJECTIVES

To characterize and identify the forms of the genus Hypostomus from the streams in the upper Paraná basin, in the State of São Paulo. This was done using external morphology and meristic and morphometric characters, analyzed utilizing multivariate analysis.

To test the Canonical Discriminant Analysis (CDA) to see if it is a useful methodology to use in the sorting and identification process. Once the species of Hypostomus were discriminated using this method, which of the names available in the literature is appropriately associated with each form, and which forms might represented new species.

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MATERIAL & METHODS

The morphological measurements were made point-to-point following Boeseman (1968) with modifications suggested by Armbruster & Page (1996) and Bockmann & Ribeiro (in press).

Due to the great ratio of overlap in various features, it was necessary to use multivariate analysis to discriminate the species Canonical Discriminant Analysis (CDA) was used because it is one of the strongest multivariate analyses. The analysis was ran using SAS, and results plotted as a graph that show the grouping of species. This allowed us to find the most significant characters separating the species, and, allowed us to associate the types with different morphospecies and, thus, apply the most appropriate name to each of these.

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RESULTS

After collecting meristic and morphometric data it was entered into a matrix and run utilizing the CDA analysis in the program SAS. The results were plotted as a graph (graph 1) showing the grouping of each species. Each letter represents a species and each circle represents the variation of the sample. The red letters are the types of the nominal species.

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CONCLUSIONS

The use of CDA to discriminate the collected samples proved very successful in grouping individuals of the same species. With the addition of data from types of most of the nominal species described from that basin, we were able to unequivocally associate previously described species with specific forms for the first time, thereby providing a basis for the identification of these different forms. The results furthermore allowed us to identify two possible new species represented by the letter E and H on the attached graph.

As clear on the graph, species E is very similar to species B and C in terms of characters utilized in the CDA, but species E has red vertical bars on the body, a feature absent in the two other species and indicative that it is a different species. A phylogenetic analysis may also reveal additional features that may confirm that this species is undescribed. That will be pursued in the future.

The situation with species H is more problematic. Although there are distinct differences in the characters used in the CDA, we have available only a few specimens and further collecting efforts are necessary. It is, nonetheless, noteworthy that this possible new species was collected in an area that demonstrates a high degree of endemism in other groups of fishes.

In summary, the statistical analysis proved to be very useful as a first step to an understanding the diversity of a complex problem of the Hypostomus species in the upper Rio Paraná basin.

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ACKNOWLEDGMENTS

The authors gratefully acknowledge the support provided by Alice Eve Kennington Endowment. We would like to thank all the staff of the Division of Fishes for their support. Particular thanks are extended to: Angela Zanata, Jeffrey Williams, Kouichi Hoshino, Mary Sangrey (Research Training Program), Sandra Raredon, Stanley Weitzman, and my fellow RTP interns.

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LITERATURE CITED

ARMBRUSTER, J. W. & L. M. PAGE. 1996. Redescription of Aphanotorulus (Teleostei, Loricariidae) with description of one new species, A. ammophilus, from the Río Orinoco Basin. Copeia, 1996 (2): 379–388.

BOCKMANN, F. A. & A. C. RIBEIRO. In press. Description of a new suckermouth armored catfish of the genus Pareiorhina (Siluriformes: Loricariidae), from southeastern Brazil. Ichthyological Exploration of Freshwaters.

BOESEMAN, M. 1968. The genus Hypostomus Lacépède, 1803, and its Surinam representatives (Siluriformes, Loricariidae). Zoologische Verhandelingen, 99: 1–89.

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ENTOMOLOGY

Sarah Garrett
"An Inventory of Leafroller Species of Moths of the Great Smoky Mountains National Park"

Abstract / Summary

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