Mitochondrial DNA polymorphism among populations of Meliponaquadrifasciata quadrifasciata Lepeletier (Apidae: Meliponini) from southern Brazil

Polimorfismo do DNA mitocondrial entre populações de Melipona quadrifasciata quadrifasciata Lepeletier (Apidae: Meliponini) do sul do Brasil

SYSTEMATICS, MORPHOLOGY AND PHYSIOLOGY

Mitochondrial DNA polymorphism among populations of Meliponaquadrifasciata quadrifasciata Lepeletier (Apidae: Meliponini) from southern Brazil

Polimorfismo do DNA mitocondrial entre populações de Melipona quadrifasciata quadrifasciata Lepeletier (Apidae: Meliponini) do sul do Brasil

Rogelio R Torres^I; Maria C Arias^II; Geraldo Moretto^III

^IDepto. de Producion Animal, Univ. Nacional de Colombia, Bogotá D.C.; [e-mail]

^IIDepto. de Genética e Biologia Evolutiva, Instituto de Biociências, Univ. de São Paulo 05.508-090, São Paulo, SP; [e-mail]

^IIIDepto. de Ciências Naturais, Univ. Regional de Blumenau, 89.010-971 Blumenau, SC; [e-mail]

ABSTRACT

The geographical distribution of the Brazilian endemic stingless bee Melipona quadrifasciata quadrifasciata Lepeletier ranges from Rio Grande do Sul to Minas Gerais states. The objective of the present study was to verify mtDNA polymorphisms among samples of M. q. quadrifasciata collected in southern Brazil. Twenty nine colonies from three localities (Blumenau and Mafra/SC and Prudentópolis/ PR) were sampled. Seven mtDNA regions were amplified and further digested with 15 restriction enzymes (PCR-RFLP). Five composite haplotypes were identified, with two unique to samples from Prudentópolis and the remaining three to samples from Mafra and/or Blumenau.

Key words: mtDNA, PCR-RLFP, stingless bee, haplotype

RESUMO

A distribuição geográfica da abelha sem ferrão Melipona quadrifasciata quadrifasciata Lepeletier compreende desde o Rio Grande do Sul até Minas Gerais. O objetivo do presente estudo foi verificar a variabilidade genética em amostras de M. q. quadrifasciata coletadas na Região Sul do Brasil. Para tanto, 29 colônias de três localidades (Blumenau e Mafra/SC e Prudentópolis/PR) foram amostradas e a técnica de PCR-RFLP para o DNA mitocondrial foi utilizada. Sete regiões do genoma mitocondrial foram amplificadas e digeridas com 15 enzimas de restrição. Cinco haplótipos foram identificados: dois exclusivos das amostras de Prudentópolis e os outros três registrados nas amostras de Mafra e/ou de Blumenau.

Palavras-chave: mtDNA, PCR-RLFP, abelha sem ferrão, haplótipo

The tribe Meliponini exhibits Pantropical distribution. The vast majority of species occurs in the Neotropical region (Michener 2000). In Brazil, this tribe is widely distributed throughout the country and is well represented, with more than 300 described species (Camargo & Pedro 2007). Their ecological and economic importance is unquestionable, since they are responsible for 40% to 90% of the native floora pollination (Kerr et al 1999). Also, the importance of several species for honey production and crop pollination has increased the beekeeping practice and queen exchange among breeders.

Melipona quadrifasciata Lep. ("mandaçaia") comprises two subspecies, M. quadrifasciata quadrifasciata and M.quadrifasciata anthidioides (Schwarz 1932). The geographic distribution of each subspecies seems to be very distinct. Melipona q. quadrifasciata is found in regions with colder climates, being more abundant in the states of Paraná and Santa Catarina (Monteiro 2000), and altitudes higher than 1500 m, in São Paulo, Rio de Janeiro and Minas Gerais states (Moure 1975). Conversely, M. q. anthidioides is naturally distributed in warmer regions, being frequent in Rio de Janeiro and Minas Gerais states (Aidar 1996). The two subspecies are morphologically discriminated by the yellow stripe pattern presented from the third to the sixth tergite (M. q. quadrifasciata presents continuous bands and M. q.anthidioides presents interrupted bands in the dorsal midline) (Aidar 1996). Molecular differences between both subspecies have been recently reported, as a putative RAPD marker of M. q. quadrifasciata was absent from M. q. anthidiodes (Waldsmchmidt et al 2000). Mitochondrial DNA (mtDNA) variation was also described between subspecies through RFLP analyses (Weinlich et al 2004, Moretto & Arias 2005). Souza et al (2008) reported a reliable and simple method to discriminate between both subspecies based on mtDNA RFLP, reinforcing the importance of describing new molecular markers for subspecies identification and maternal origin, since hybrids can be originated through natural contact or mediated by beekeepers as a consequence of queen or brood combs exchange among different geographic regions.

In this paper, we detailed the methodology and discuss the results which were briefloy reported as unpublished data in a review article (Arias et al 2006), focusing in detecting mtDNA polymorphisms among samples of M. q. quadrifasciata from three localities (here called as populations) of southern Brazil in an attempt to identify haplotypes closely associated to geographic sites. Moreover, as an effort to improve the data described by Souza et al (2008), seven mtDNA regions were analyzed and a large number of restriction enzymes were utilized.

Material and Methods

A total of twenty nine feral M. quadrifasciata quadrifasciata colonies were sampled. Workers were obtained from twelve, eight and nine colonies located in Blumenau, Mafra (Santa Catarina state) and Prudentópolis (Paraná state), respectively. Blumenau (26º 55'26'' S) is located at the Itajaí Valley, at 21 m altitude and exhibits an average temperature of 21.6ºC; Mafra (26º 06'55''S) is located at the north of Santa Catarina state at 809 m altitude, with an average temperature of 18ºC; and Prudentópolis (25º 12'40''S) is at 730 m altitude, with an average temperature of 19ºC. According to Koppen (1948), these three regions have a humid mesothermic climate, with no distinct dry period.

Total DNA was extracted as described by Sheppard & McPheron (1991) using one thorax per extraction. The mtDNA was analyzed by PCR-RFLP, a technique that consists in amplifying mitochondrial genome regions by PCR and subsequent digestion of the fragments by restriction enzymes. PCR was carried out using 1 µl of the total DNA extraction, 5 µl of PCR buffer (Boehringer Mannheim), 1.5 µl of each primer (20 µM), 5 µl of dNTPs (2 mM each) and 2.5 U of Taq DNA polymerase (Boehringer Mannheim) in a total volume of 50 µl. Each PCR reaction was submitted to an initial denaturation at 94ºC/5 min, followed by 35 cycles of denaturation at 94ºC/1 min, annealing for 1 min and 20 s at the specifi c temperature for each pair of primers (Table 1) and elongation at 64ºC/2 min. Afinal elongation step at 64ºC for 10 min was performed. Seven primer pairs (Table 1) were used to amplify the specific mtDNA regions of M. q. quadrifasciata. The PCR-amplified fragments were separated by electrophoresis in 0.8% agarose gels, stained with ethidium bromide, visualized under a UV light and photographed.

To determine the presence of restriction sites, the PCR-amplified fragments were digested for a minimum period of 6h with the following restriction enzymes: Ase I, Bam HI, Bcl I, Bgl II, Cfo I, Cla I, Dra I, Eco RI, Eco RV, Hae III, Hind III, Hinf I, Nde I, Pst I and Ssp I. The digested products were analyzed in 1.0% agarose (Agarose 1000 Gibco) or 12 % acrylamide gels (non-denaturing conditions). The latter were silver stained, dried and scanned.

Results

The fragment size of the seven amplified mtDNA regions ranged from 950 bp to 2200 bp (Table 1) according to the expected (Francisco et al 2001, Moretto & Arias 2005). The restriction enzymes Bgl II, Bam HI, Cfo I and Eco RV did not cleave any fragment. The enzymes Bcl I, Cla I, Dra I, Eco RI, Hae III, Hind III, Nde I and Pst I presented one or more restriction sites in each mtDNA region, but they did not yield polymorphic restriction patterns. In contrast, the enzymes Ase I, Hinf I and Ssp I detected polymorphic sites at intra and inter population levels (Figs 1, 2, Table 2).

The variation considered to compose the haplotypes was the presence/absence of restriction fragments and shift in fragment gel mobility, which led to the identifi cation of five composite haplotypes identified, which were distributed according to the collecting sites (Table 3). Two haplotypes were found per population. Haplotype 5 (H5) was the only one shared between populations (Blumenau and Mafra). Differences among H5, H4 and H3 found only in Santa Catarina reside in gel mobility polymorphism, not in restriction pattern. Haplotypes H1 and H2 were exclusive of Prudentópolis and differed in four out of six RFLP markers when compared to H3, H4 and H5. Haplotype differences within population were restricted to a single or two RFLP markers (Table 3).

Discussion

Few molecular studies on stingless bees have been conducted (Arias et al 2006), so the data available are still limited and are poorly representative, considering the hundreds of Meliponini species and their wide distribution (Michener 2000, Camargo & Pedro 2007). Weinlich et al (2004) determined the mtDNA restriction map for seven species of Melipona including M. quadrifasciata. Eighteen restriction sites were mapped for this species, however comparing the published map with the present study some differences should be pointed out. We did not fi nd the Bgl II site mapped at the cytochrome B gene, and moreover this enzyme did not cut any mtDNA region here studied. Nonetheless, a previous undetected Hae III site in the fragment containing the ATPase 6, 8 and COIII genes was detected in our study. These results were consistent among all samples, thus not representing inter population variation.

Recently, Moretto & Arias (2005) published a comparative study between the two subspecies of M. quadrifasciata by analyzing mtDNA restriction patterns. Polymorphisms between M. quadrifasciata quadrifasciata and M.quadrifasciata anthidioides were detected for COI region digested with Hinf I and Nde I, and CytB region digested with Dra I. Souza et al (2008) analyzed a large sample of M. quadrifasciata and reported RFLP patterns generated by CytB region after Vsp I digestion closely associated to each subspecies. Although the latter study presented a strong correlation between molecular markers and subspecies, authors could not identify molecular markers associated to the nest geographic origin.

The present study aimed at the molecular characterization of M. quadrifasciata quadrifasciata from three distinct geographic areas from Southern Brazil by mtDNA PCRRFLP analysis. Most of the restriction enzymes were not informative; however, polymorphism was detected by the enzymes Ssp I, Hinf I and Ase I. Polymorphisms verified at the 16S/12S region were not related to any population exclusively, representing intra-specific variability. The restriction patterns generated by Ase I digestion are worthwhile as they differ only by differences in gel mobility of two fragments (210 and 105 bp). This mobility shift was reported as a consequence of double-strand conformation polymorphism (DSCP) due to base substitutions (Hagerman 1990). The same phenomenon has been verified in other studies on bees for the 16S and CytB regions (Collet et al 2007, Souza et al 2008). Nonetheless, the COI/COII region digested with Ase I and Hinf I, and the ND2 region digested with Ase I presented distinct restriction patterns between samples from Prudentópolis (Paraná state) and Santa Catarina state, and exclusive haplotypes were identified. It is interesting that the COI/COII region of Apis mellifera L. contains an intergenic non-coding region (Crozier et al 1989), which is highly informative to differentiate among A. mellifera geographic races and evolutionary lineages (Garnery et al 1992, 1995, Franck et al 1998). Although this intergenic region was reported as absent in Meliponini (Arias et al 2006), the surrounding genes (COI and COII) revealed polymorphic and exclusive restriction sites between M. quadrifasciata quadrifasciata samples from Paraná and Santa Catarina.

The colonies sampled in Santa Catarina had three haplotypes: H3 was present only in Mafra, H4 only in Blumenau and H5 in both localities, while samples from Prudentópolis had two haplotypes (H1 and H2). Geographic characteristics, as altitude, indicate similarities between Mafra and Prudentópolis, both at around 700 m high, whereas Blumenau is located at 23 m above sea level. The high similarity among Mafra and Blumenau haplotypes and the high incidence of haplotype H5 in both regions could suggest a current gene floow mediated by females between these two geographic regions. In fact these two localities are connected by Atlantic Rain Forest remnants (Moretto, personal information), which may function as a natural corridor to the dispersion of reproductive individuals. The two haplotypes identified in Prudentópolis were exclusive, indicating a possible isolation of this population in relation to the other in here studied. Although Prudentópolis and Mafra are located in areas of Araucaria Forest, the former seems to be isolated as no ecological corridor exists due to Araucaria and Atlantic forest fragmentation. Arias et al (2006) studied populations of the stingless bee Plebeia remota Holmberg and through mtDNA RFLP verified that samples collected from Prudentópolis did not share haplotypes with populations from São Paulo, Santa Catarina and eastern Paraná. Moreover, a multidisciplinary study provided extra evidences based on wing morphology, cuticular hydrocarbons and mtDNA RFLP that P. remota from Prudentópolis should be considered as a distinct species (Francisco et al 2008). Whether this is indicative of an ancient event where populations of several species were kept isolated in southern Paraná refuge or is related to natural selection due to climatic or biotic factors, it should be a subject for further studies, including a broad sampling of M.quadrifasciata and other species for comparative studies from this area and nearby .

Received 28/IX/07. Accepted 29/I/09.

Edited by Fernando Noll - UNESP

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Publication Dates

• Publication in this collection
  25 May 2009
• Date of issue
  Apr 2009

History

• Accepted
  29 Jan 2009
• Received
  28 Sept 2007