The Galápagos Islands, Pickled Lizards and DNA: The Value of Museums
The Galápagos Islands are home to a wide array of endemic wildlife. Among the species found nowhere else on Earth is the Galápagos land iguana, Conolophus subcristatus. Originally, this species was found on 7 islands throughout the Archipelago, but they disappeared from Santiago Island in the 19th century and from Baltra Island in the 1940s. The reasons for the loss of iguanas on Baltra are unclear, but may have been due to the construction of a U.S. air station during World War II.
Fortuitously, in 1932, a number of land iguanas were translocated from Baltra to nearby North Seymour Island, by members of the Allan Hancock Expedition. Descendants of those animals, and possibly a few of the original transplanted individuals, survive today on North Seymour and, thus, represent a potential source population for the return of iguanas to Baltra. Both the Galápagos National Park Service and the Charles Darwin Research Station are interested in repatriating iguanas to Baltra, but North Seymour has a 2nd land iguana population in addition to descendents of the introduced Baltra animals. The two populations are indistinguishable, although they have distinct breeding seasons. It is the current policy of the Galápagos National Park, to only repatriate animals to islands of their precise origin. Since it is unclear which of the two North Seymour populations originated on Baltra, plans to reestablish iguanas on Baltra were put on hold...until UNM biologists came to the rescue, but by a rather circuitous route.
In 1905-06, a Galápagos expedition, under auspice of the California Academy of Sciences, made collections throughout the Archipelago, including land iguanas from Baltra. Since 1906, these specimens have been maintained at the California Academy in San Francisco. But in 2001, UNM biologist, Dr. Bruce Hofkin and graduate student April Wright obtained tissue samples from approximately 20 of these Baltra iguanas on loan from the California Academy. Their goal was to attempt to extract DNA from these museum-preserved samples and develop a DNA fingerprinting technique with which they could compare these century-old Baltra lizards with today’s North Seymour iguanas. If successful, they could identify animals of unambiguous Baltra origin, among living land iguanas, with the ultimate goal of providing this information to the Galápagos National Park Service, so that a restoration project could be initiated.
Extracting DNA from century-old museum specimens was problematic, especially in the case of these iguana samples, because no records were available regarding the manner in which the iguanas were originally preserved. After several false starts, Hofkin and Wright consulted Dr. Anne Stone (UNM Anthropology Department) because Stone is a recognized expert in the extraction and sequencing of ancient DNA. Her advice regarding the Baltra samples proved crucial and, ultimately, Hofkin and Wright successfully extracted and sequenced DNA from 12 of the 20 museum specimens.
Previous work by Dr. K. Rassmann, Bielefed University, Munich, Germany, had shown that C. subcristatus from different islands could be distinguished based on Cytochrome B polymorphisms. Hofkin and Wright found two Cytochrome B haplotypes present on North Seymour lizards, suggestive of a mixed population. One of these two haplotypes was unique to North Seymour; using PCR, they found that the haplotype previously thought to be unique to North Seymour, was also present among the original Baltra animals in the California Academy collection! This indicates that animals currently living on North Seymour bearing this haplotype, were descendants of the animals originally brought to North Seymour by the Hancock Expedition. A manuscript detailing this work is currently in press in Conservation Genetics.
In May 2002, Hofkin and Wright traveled to Galápagos and collected blood samples from approximately 160 land iguanas that were living on North Seymour or held at the Charles Darwin Research Station on Santa Cruz Island. They are currently extracting DNA from these samples, in preparation for sequencing. Their data will be provided to colleagues at the Charles Darwin Research Station, who will use the information to decide which animals should be repatriated to Baltra Island, allowing this threatened and endemic reptile to reclaim a part of its former habitat. Funds to support this study were provided by the University of New Mexico Resource Allocation Committee, the Max and Anna Levinson Foundation, and the Charles Darwin Research Station.
In addition to his research and teaching responsibilities in Biology, Dr. Hofkin also writes, produces and hosts, " Today’s Biocast." As we enter the Century of the Life Sciences, keeping up with the many advances in biology and related fields can be difficult, even for the specialist. But discoveries and breakthroughs affect us all in many ways, so it behooves us to know what’ s going on. Here to help is Today’s Biocast. Since 1992, Bruce has provided New Mexican listeners with information about "biology that affects your life."His show can be heard Tuesday through Thursday, between 8:20-8:30 a.m. on KANW (89.1 FM) radio in Albuquerque. Each 2-minute segment combines up-to-the-minute education and light, sometimes humorous, entertainment that exposes listeners to current biological topics in an understandable manner. Topics are selected for their appeal to a broad listener audience, but are of particular interest to young listeners, encouraging their further exploration of the life sciences. The program is sponsored by alumni and friends of Biology through donations to the UNM Foundation.