Africanization in the United States

Abstract

The expansion of Africanized honeybees from South America to the southwestern United States in Ͻ50 years is considered one of the most spectacular biological invasions yet documented. In the American tropics, it has been shown that during their expansion Africanized honeybees have low levels of introgressed alleles from resident European populations. In the United States, it has been speculated, but not shown, that Africanized honeybees would hybridize extensively with European honeybees. Here we report a continuous 11-year study investigating temporal changes in the genetic structure of a feral population from the southern United States undergoing Africanization. Our microsatellite data showed that (1) the process of Africanization involved both maternal and paternal bidirectional gene flow between European and Africanized honeybees and (2) the panmitic European population was replaced by panmitic mixtures of A. m. scutellata and European genes within 5 years after Africanization. The post-Africanization gene pool (1998)(1999)(2000)(2001) was composed of a diverse array of recombinant classes with a substantial European genetic contribution (mean 25-37%). Therefore, the resulting feral honeybee population of south Texas was best viewed as a hybrid swarm.T HE evolutionary significance of natural hybridizaOur study of hybridization, which deals with one of tion has been debated for decades (Mayr 1942

Stock composition of northern neotropical honey bees: mitotype and morphotype diversity in Mexico (Hymenoptera: Apidae)

“…This finding is in agreement with results in tropical and subtropical regions elsewhere (Clarke et al 2002;Pinto et al 2005;Whitfield et al 2006). A numerical asymmetry between Africanized and European honey bees can explain these results (Rinderer et al 1991).…”

“…The numerical superiority of African drones in congregation areas where queens mate mainly arises from proportionately greater male production by Africanized colonies ) and Africanized drones' parasitism of European colonies, which also suppress the production of European drones (Rinderer et al 1985). In combination, these factors favor the introgression of African paternal alleles into European colonies while resulting in the eventual displacement of European nuclear markers (Rinderer et al 1991;Pinto et al 2005;Whitfield et al 2006). However, in temperate zones, feral populations with African ancestry may not reach the high densities observed in tropical areas, giving their European counterparts better opportunities to compete reproductively (Sheppard et al 1991;QuezadaEuán 2007) as our findings suggest.…”

“…For instance, the expansion of Africanized honey bees in the temperate region of the southern United States seems to have been greatly enhanced by the decimation of resident feral European honey bee colonies following the arrival of the Varroa mite (Pinto et al 2005). Similarly, in Puerto Rico, a genetically stable honey bee population has formed, with European-and Africanlike traits associated with Varroa resistance (Galindo-Cardona et al 2013).…”

Prevalence of Nosema species in a feral honey bee population: a 20-year survey

“…This was done to investigate the patterns of hybridization between bees of European and African descent occurring in this population of feral honey bees since the late 1990s (Baum 2003;2005;Pinto 2004;Pinto 2005). In 2013, 5.60 km 2 of the original WWR study area was resurveyed, and 89 of the original 109 trees that had been identified earlier were re-visited and sampled for honey bees if a colony was present.…”

Frequency of European and African-derived morphotypes and haplotypes in colonies of honey bees (Apis mellifera) from NW Mexico

“…The relative importance of the population size of resident European honey bees plus the environmental and beekeeping characteristics in different localities on the process of Africanization is controversial (Smith et al, 1989;Rinderer et al, 1991;Sheppard et al, 1991). One of the main problems in elucidating the relative importance of different factors and the mechanisms involved in the process is the lack of long term detailed studies before, during and after the arrival of colonizing swarms (QuezadaEuán, 2000; Pinto et al, 2005). The study of the expansion and establishment of AHBs in NW Mexico can provide additional information to test hypothesis regarding the relative effect of the size of the resident EHB population and that of climatic and geographic barriers (Quezada-Euán et al, 2003) different from the ones that AHBs have encountered during their expansion history across tropical and subtropical Mexico.…”