Thursday, September 17, 2015

Africanized honey bees

The honey bee subspecies Apis mellifera scutellata, was introduced from southern Africa to Brazil in 1956 in an effort to breed honey bees better suited to the Neotropics. Swarms soon escaped containment and began to hybridize with European honey bees. The resulting hybrid offspring are known as "Africanized" honey bees. Africanized bees have since spread throughout much of the Western hemisphere, and arrived in the Southern United States in the mid-1980s.

Africanized bees are characterized by far greater defensiveness than European honey bees. They are more likely to attack a perceived threat and, when they do so, attack relentlessly and in larger numbers. Their hyper-defensive behavior has earned them the nickname "killer bees", an unfortunate misnomer which has caused the public to falsely believe that "killer bees" actually seek out and attack people for no reason other than sheer ferocity. That is of course total nonsense. 

Researchers from the University of California, San Diego used mitochondrial markers and morphometric analyses to determine the prevalence of Africanized honey bees in San Diego County and their current northward progress in California west of the Sierra Nevada crest. The current standard molecular method for identification is Restriction fragment length polymorphism (RFLP) analysis of the cytochrome b gene.

Some of the results were discussed in this TV interview with one of the authors, Josh Kohn:

In contrast to the statewide sample, honey bees throughout San Diego County were highly Africanized. Restriction analysis revealed that 64.8% of the 298 bees from San Diego County carried the African mitochondrion. 

The colleagues also found a single nucleotide polymorphism (SNP) at the DNA Barcode locus COI that distinguishes European and African mitotypes. In order to confirm its utility they took 401 DNA Barcode sequences from BOLD and mapped their occurrence data. Sequences with the putative African SNP are found only where they are known to occur (Africa, South and Central America and the lower U.S.) while European mitotypes are spread across continents. This won't change the fact that RFLP will remain method of choice as it is currently easier, cheaper and very reliable.

DNA Barcoding is becoming an increasingly popular method of assessing biodiversity used both in research and classroom contexts. Because honey bees are frequently collected during invertebrate biodiversity assessments that utilize DNA barcoding, the Barcode of Life Database will provide ongoing data on further spread of Africanized honey bees.

What a great way to use BOLD.

h/t Josh Kohn

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