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From hybrid swarms to swarms of hybrids

Thomas J. Stohlgren, Allen L. Szalanski, John F Gaskin, Nicholas Young, Amanda West, Catherine S. Jarnevich, Amber Tripodi
Environment and Ecology Research 2014 v.2 no.8 pp. 311-318
Africanized honey bees, Apis mellifera scutellata, Tamarix chinensis, Tamarix ramosissima, biogeography, ecosystems, genotype, habitats, humans, hybrids, indigenous species, introgression, invasive species, linear models, mitochondrial DNA, risk, Southwestern United States
The introgression of modern humans (Homo sapiens) with Neanderthals 40,000 YBP after a half-million years of separation, may have led to the best example of a hybrid swarm on earth. Modern trade and transportation in support of the human hybrids has continued to introduce additional species, genotypes, and hybrids to every country on the globe. We assessed the utility of species distribution modeling of genotypes to assess the risk of current and future invaders. We evaluated 93 locations of the genus Tamarix for which genetic data were available. Maxent models of habitat suitability area showed that the hybrid T. ramosissima x T. chinensis was slightly greater than the parent taxa (AUCs > 0.83). Generalized linear models of Africanized honey bees, a hybrid cross of Tanzanian Apis mellifera scutellata and a variety of European honey bees including A. m. ligustica, showed that the Africanized bees (AUC = 0.81) may be displacing European honey bees (AUC > 0.76) over large areas of the southwestern U.S. More important, Maxent modeling of sub-populations (A1 and A26 mitotypes based on mDNA) could be accurately modeled (AUC > 0.9), and they responded differently to environmental drivers. This suggests that rapid evolutionary change may be underway in the Africanized bees, allowing the bees to spread into new areas and extending their total range. Protecting native species and ecosystems may benefit from preliminary risk maps of harmful invasive species, hybrids, and genotypes.