Cytogenetic and molecular studies on neotropical small rodents from Brazil
| Grant number: | 01/11175-9 |
| Support type: | Research Projects - Thematic Grants |
| Duration: | May 01, 2002 - December 31, 2006 |
| Field of knowledge: | Biological Sciences - Biology |
| Principal Investigator: | Claudio de Oliveira |
| Grantee: | Claudio de Oliveira |
| Home Institution: | Instituto de Biociências (IBB). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil |
| Co-Principal Investigators: | Fausto Foresti |
Abstract
The superfamily Loricarioidea is the largest monophyletic group of Siluriformes found in the Neotropical region, including six families: Nematogenyidae (1 sp.), Trichomycteridae (ca. 200 spp.), Callichthyidae (ca. 170 spp.), Scoloplacidae (4 spp.), Astroblepidae (ca. 40 spp.) and Loricariidae (ca. 600 spp.). This group includes the three largest Siluriformes genera: Hypostomus, Corydoras and Trichomycteros, and a large number of species with high economic value, mainly as ornamental fishes. Actually, the hypotheses about the relationships among and within the families are based exclusively on morphological characters, with evidence being scarce for important portions of the cladograms. The present project intends to study the phylogeny of the Loricarioidea on an integrated basis of characters, providing a robust phylogenetic hypothesis with wide biological significance. Comparative and wide taxonomic studies of four kind of characters of a distinct nature and biological basis will be conducted, including morphology, DNA sequences, karyotypes and spermatozoa ultrastructure. The data obtained will be analyzed according to the most suitable methodology for each kind of character and, after this analysis, all data will be combined in a single matrix, with the objective of identifying the most parsimonious general hypothesis. The comparison among single and combined analyses should permit identification of the existence of regions in the phylogenies in which a particular kind of character is more or less informative. DNA sequences will be employed to estimate the time of occurrence of cladogenetic events. These data will be used to identify the relationships among events of diversification in Loricarioidea and the main geological events known in the Neotropical region. A particular question to be answered is if differentiation of the group occurred simultaneously with the Gondwana fragmentation. Dated Loricarioidea fossils with phylogenetic position relatively well determined will be used as an independent test for the time estimated by molecular clock. The information obtained in the present study will be useful as a basis for wide evolutionary studies in Loricarioidea, permitting an evaluation of the factors possibly responsible for the incredible adaptative radiation found in some genera of the families Callichthyidae, Trichomycteridae and Loricariidae. (AU)