Filogeografia de Omophoita octoguttata Fabricius (1775) (Coleopter: Alticinae) na região do Brasil e diferenciação de espécies crípticas pertencentes ao gênero Alagoasa Bechyné (1955) (Coleoptera: Alticinae)

Abstract

Coleoptera is the most diverse order among living beings, corresponding to about 40% of insects and 30% of known animals. The subfamily Alticinae comprises 10,000 species, and its individuals are popularly known as flea-beetles. In addition, they occur in greater amounts in degraded areas, primary succession and edges. The species Omophoita octoguttata, show a Neotropical distribution, and is found in the Atlantic forest in the South and Southeast regions of Brazil; however, it is known that this vegetation undergoes deforestation processes, and few preserved areas have remained, thus interfering with the dispersion of species. From the cytogenetic view, the subtribe Oedionychina presents interesting characteristics to be studied, such as, giant sex chromosomes assynaptics, diploid number 2n = 22 and sexual determination system type X + y, in most of its species, as well as many species with identification problems and mimetics. Thus, the objective of this study was to determine the existence of population structure of O. octoguttata in the southern region of Brazil, in order to infer on natural barriers to the dispersion and the presence of a phylogeographic discontinuity for Alticinae in this region. Furthermore, were analyzed three species belonging to the genus Alagoasa, possibly mimetic, to differentiate them cytogenetically and by molecular techniques. For the population analysis of O. octoguttata, amplified sequences from the mitochondrial cytochrome oxidase I (COI) and elongation factor (EF1-alpha) were used in 90 individuals collected in 6 different locations in the states Paraná, Santa Catarina and Rio Grande do Sul. The haplotypic and nucleotide diversity was high in all the analyzed locations. For the EF1-alpha gene, many different haplotypes were observed, indicating that the gene is not a good population marker for the analysis performed in this work for this species. The presence of a phylogeographic discontinuity for Alticinae was not observed in the Atlantic Forest of the South region of Brazil, since individuals belonging to the locality of Nonoai, located to the South, still maintains gene flow with the northern localities, possibly using the edge of the Atlantic Forest fragments to maintain a dispersal path. With respect to cytogenetic analysis, the three species (Alagoasa pantina, Alagoasa sp.1 and Alagoasa sp.2) presented diploid number 2n = 22, meiotic formula 2n = 10II + X + y, sex determination system type X + y, with giant sex chromosomes assynaptics, consistent with that observed in the subtribe Oedionychina. FISH using 18S and 5S rDNA probes showed the occurrence of syntenia and colocalization of these markers associated with a pair of autosomes in the three species analyzed, a condition considered ancestral in Coleoptera. The telomeric FISH demonstrated the presence of the TTAGGn repeat in the three species analyzed, in addition to showing the occurrence of interstitial markings on some sex chromosomes.