POPULATION DIFFERENTIATION AND RACIAL ADMIXTURE IN THE AFRICANIZED HONEYBEE (APIS MELLIFERA L.)

Abstract

To study the degree of interpopulational differentiation and racial admixture in Africanized honeybees, we collected worker bees from three regions of Brazil (the northeast, the state of Sao Paulo, and Porto Alegre) and from Uruguay and determined their genotypes for 10 enzyme loci. We also performed a morphometric analysis on forewing measurements of worker bees from the northeast and Porto Alegre regions of Brazil and from Paysandu, Uruguay. Comparative analysis of interpopulational heterogeneity snowed that there are significant differences, especially at the Mdh locus, among the populations from different regions. An increase in the frequency of the Mdh allele was observed from north to south, with predominance in the Uruguayan populations. A small component of interpopulational variability was detected in the populations studied. Racial admixture was calculated from information obtained for Mdh in Africa and Europe. The percentages of racial admixture differed slightly but significantly among Brazilian regions. The morphometric study based on canonical variables exhibited a similar pattern. The greater proportions of Apis mellifera adansonii alleles in the admixture may be explained by selection during the initial stage of migration of Africanized bees and by preferential mating between individuals of the same race. Differences in the proportions of A. m. adansonii alleles between regions indicate incipient populational differentiation of Africanized bees. We suggest that greater gene flow from the European races in the south of Brazil could be one of the causes of this phenomenon.

Morphometric isozymic and mitochondrial variability of Africanized honeybees in Costa Rica

“…The diversity of allele frequencies at the MDH locus between the three Costa Rican regions is higher than the genetic variation that has been detected between Brazilian populations separated by distances of thousands of kilometers (Lobo et a!., 1989). However, Lama et al, 1990).…”

“…Comparative studies of behaviour, population dynamics and morphometrics have revealed that these new bee populations are very similar to their African ancestors (summarized by Michener, 1975;Winston, 1992). Genetic polymorphism data have supported this conclusion, except in some regions where higher frequencies of European alleles can be detected (Lobo et al, 1989;Rinderer et al, 1991;Sheppard et al, 1991b). The latter phenomenon may be a result of prior high population densities or continued introduction of other honeybee races and/or ecological constraints for Africanized bees.…”

“…Opportunities for the introgression of European alleles are very different at different loci: polymorphism at loci that influence selectively important traits should disappear in a few generations, but alleles at other polymorphic loci can, through recombination, subsist in an 'African' genetic background. For example, some isozymic data show low but significant percentages of alleles of European origin (Lobo et aL, 1989;Sheppard et a!., 1991a). However, mitochondrial DNA RFLPs (mitotypes) are of African origin in most of the samples (Sheppard et al, 1991a).…”

Heterozigosidade e assimetria do número de hâmulos em operárias adultas de Apis mellifera (Hymenoptera, Apidae)

“…Análise aloenzimática -Para estimar as heterozigosidades intra-loco ( Hi ) e média ( H ), extratos de tórax de operárias adultas foram analisados através de eletroforese horizontal em gel de amido (DEL LAMA et al 1985, 1988, 1990LOBO et al 1989) para os seguintes sistemas aloenzimáticos: malato desidrogenase (Mdh) nas amostras Européias e Africanizadas; esterases (Est-1 e Est-3), fosfoglucomutase (Pgm) e hexoquinase (Hk) nas amostras Africanizadas.…”

Maximum likelihood estimates of gene frequencies and racial admixture in Apis mellifera L. (Africanized honeybees)

“…An example is the analysis of the genetic composition of the Africanized honeybee, the population of bees resulting from the introduction of Apis mellifera scutellata to Brazil in 1956 (Kerr, 1967;Michener, 1975). Estimation of the frequencies of some racial markers in these populations may reveal the existence or otherwise of interracial hybridization during the initial settlement of A. m. scutellata in Brazil, and its subsequent migration across the American continent Hall & Muraihidharan, 1989;Lobo et a!., 1989;Smith et a!., 1989;Del Lama eta!., 1990, Hall, 1990Smith, 1991).…”