Morphometric isozymic and mitochondrial variability of Africanized honeybees in Costa Rica

Abstract

Wing morphometry, isozymic variation and mitochondrial RFLPs were studied in samples of feral Africanized bees collected at three different locations in Costa Rica, two of them in the lowlands (Guanacaste and Golfito regions) and the other in the Central Valley. These data revealed a predominantly African origin at all locations. However, significant heterogeneity was found between the two lowland sites and the Central Valley for some isozyme markers as well as for the RFLPs considered in this study. Both isozymic and mitochondrial DNA European markers were more frequent in the Central Valley. This could be the result of different opportunities for European gene introgression at the beginning of the migration of Africanized honeybees. It is shown that different gene frequencies of mitochondrial and nuclear European genetic markers may exist in Africanized bee populations, and that this may result from different selection pressures among colonies with African and European queens.

Asymmetric introgression of African genes in honeybee populations (Apis mellifera L.) in Central Mexico

“…A number of studies have investigated the process of Africanization of the honeybee using various genetic markers (for example, Hall and Muralidharan, 1989;Smith et al, 1989;Del Lama et al, 1990;Rinderer et al, 1991;Sheppard et al, 1991;Lobo 1995;McMichael and Hall, 1996;Suazo et al, 1998;Quezada-Euán, 2000;Clarke et al, 2001Clarke et al, , 2002Pinto et al, 2005;The Honeybee Genome Sequencing Consortium, 2006;Whitfield et al, 2006). Initially, it was believed that the Africanized honeybees were a hybrid swarm of European and African honeybee subspecies, but the use of mitochondrial DNA markers soon undermined that view (Smith et al, 1989).…”

Genetic structure of honeybee populations from southern Brazil and Uruguay

“…Malate dehydrogenase (Mdh-1) and hexokinase (Hk-1) allozymes have usually been used to characterize A. mellifera populations or determine their racial composition (Badino et al, 1983;Sheppard and McPheron, 1986;Spivak et al, 1988;Lobo et al, 1989;Del Lama et al, 1988Lobo, 1995). Nuclear and mitochondrial DNA polymorphisms (Hall, 1986(Hall, , 1990Smith and Brown, 1988;Hall and Muralidharan, 1989;Oldroyd et al, 1992;Sheppard et al, 1991a,b;Clarke et al, 2001), and, more recently, microsatellites (Estoup et al, 1993, Franck et al, 1998 have proven to be very useful molecular markers for honeybee population genetics.…”

Hybridization between European and Africanized honeybees in tropical Yucatan, Mexico. II. Morphometric, allozymic and mitochondrial DNA variability in feral colonies

“…Although there was a high frequency of African mtDNA in Yucatecan feral colonies, this finding could be explained by differences in the reproductive behaviour of Africanized bees with respect to their European counterparts [21]. For instance, the high reproductive rate of colonies headed by Africanized queens might eventually lead to a reduction of European genes in the feral pool simply by a numerical (selective) effect, rather than as a result of genetic incompatibilities [14,21]. However, it was also evident that European mtDNA was present in a significant proportion of feral colonies, 449 commercial populations found in SE Mexico.…”

“…However, high population densities of managed European colonies can probably create a scenario in which European genes may have a better chance of introgression and survival in the feral Africanized pool [14,18,21]. In Yucatan at the start of the Africanization process, European colonies were at a numerical advantage and this situation probably created the conditions for a high degree of introgression of European genes within the feral population.…”

“…Allele frequencies were calculated for each system and were then compared with the allele frequencies reported for feral colonies in Brazil [33] and Costa Rica [14] by means of a χ 2 test.…”