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Earthwatch 2003 SCAP Team The fate of interspecific hybrids in an ant hybrid zone July 13-19, 2003 |
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THE SITE
Southwestern Research Station near Portal AZ |
THE TEAM L-R Dan Cremons, Emily Smith, Genna Hall, Lee Murray, Maya Perez-Baker, Omar Narvaez |
This research project is an ongoing study of caste differences in hybridizing seed-harvester ants. One species, Pogonomyrmex rugosus, occurs throughout the southwest; its range overlaps with a second species, P. barbatus, that occurs from eastern Arizona to Texas and much of Mexico. In a population within the overlap region, we have found that there are actually two interspersed, genetically distinct colony types, distinguishable only by male body color. Males from approximately half of the colonies are completely red in color ("red"); and the other half of colonies exclusively contained males with a black head and thorax and red abdomen ("black"). Red and black males are highly genetically differentiated. Workers from both species are exclusively hybrids, with no non-hybrid workers observed in any field colonies. In contrast, their virgin queen sisters are overwhelmingly non-hybrids, although occasional hybrid queens are seen.
A winged queen and red male of the hybrid population |
A winged queen of P. fuscatus (aka hybrid |
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This system of genetic caste determination (workers always hybrids, sister queens non-hybrids) is apparently costly, as the colony would waste many queen-destined eggs when the colony is not producing queens. However,one intriguing fact about this hybrid zone is that it is fairly geographically widespread and stable. Therefore, the question arises whether there is a selective advantage to having hybrid workers. Our team investigated whether the hybrids (what we referred to as P. fuscatus) had ecological advantages over the normal population of P. rugosus. We examined aggression in foraging, scouting and recruitment, and intra- and interspecific aggression levels. Experiments were designed, carried out and data analyzed by the students. |
The project also known as: the search for
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 Maya, Genna, Emily |
 Lee, Dan, Omar |
 Glennis |
Thanks to:
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