Media & Education
News Room

June 2010, Volume 8, Issue 6

Bats in the News

Too Many Ancestors

Bats have a well-deserved reputation as unusual animals. But even by bat standards, a fruit bat on the Caribbean islands of the Lesser Antilles is a rare find, reports Discover Magazine online. A genetic analysis reveals that the bat species Artibeus schwartzi is “a hybrid mish-mash of DNA inherited from no less than three separate ancestors.”

The complicated ancestry of the species has puzzled scientists for almost three decades, Discover said. Now Ph.D. candidate Peter Larsen of Texas Tech University has documented that the bat represents the rare fusion of two species that still inhabit the islands and a third that is probably extinct. Larsen’s coauthors are graduate student María R. Marchán-Rivadeneira and Professor Robert J. Baker, both of Texas Tech.

Larsen sequenced DNA from 237 individuals from the seven fruit bat species of the Lesser Antilles. Most of A. schwartzi’s genome is a cross between the genes of the Jamaican fruit bat (A. jamaicensis) and the flat-faced fruit bat (A. planirostris), Discover said, while “a tiny minority of sequences don’t match either genome.”

Animal cells also include another, smaller collection of DNA inside structures called mitochondria. Discover reports that Larsen found that the mitochondrial genome of A. schwartzi, however, does not resemble mitochondrial DNA from either of those two species. Larsen suspects those sequences represent a third fruit-bat species that is now extinct.

The result of all this inter-breeding is a fruit bat species that is larger and more robust than either of its ancestors, and is quite capable of reproduction. Larsen said in a Texas Tech news release that “most mammal hybrids are thought to be evolutionary dead-ends because they’re sterile [the mule, for example, offspring of a horse and donkey] or poorly adapted to their environment.”

Larsen said the new species probably emerged in the last 30,000 years or so, after the Jamaican fruit bat colonized the Lesser Antilles from Mexico, while the flat-faced fruit bat arrived from South America. Before that, the species apparently had never shared overlapping ranges.

Larsen believes Artibeus schwartzi’s “success stems from events that took place after the last Ice Age,” Discover said. “Rising sea levels severely isolated the islands that it now lives on, particularly St. Vincent. This separated the new hybrid from its parental species, cutting off the flow of genes that would otherwise dilute this unique lineage.”

In any event, the magazine concludes, “A. schwartzi’s three-way chimeric genome is a rare find indeed.”

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