August 03, 2012
Cloudy with a chance of horned lizards
Horned lizards are especially diverse, including sixteen species that vary dramatically from each other (picture Thanksgiving dinner, when you're wondering how that crazy cousin could POSSIBLY be related to you).
Some give live birth like humans, while others lay eggs. Some can squirt blood out of their eye as a defense mechanism against predators, while others can’t. Not to mention, horn and tail lengths vary dramatically between the species. How, where, and why did these lizards adapt so differently from one another?
That’s what Dr. Adam Leaché, curator of herpetology at the Burke Museum, is trying to find out. Adam, along with University of Washington graduate student Jared Grummer, set out to compare DNA from all sixteen species of horned lizards to learn their evolutionary history.
The Burke Museum’s Genetic Resources collection already had tissue samples for almost all of the horned lizards in the family except for three found in southern Mexico: the short-tail horned lizard, bull horned lizard, and the giant horned lizard.
After months of planning and preparation, Adam and Jared set out for Mexico, where they joined professors and students from the Universidad Nacional Autónoma de México to form a top-notch lizard-catching field team. The Mexican landscape is hostile at best, and the three species of horned lizards they were looking for are notoriously difficult to catch (part of the reason they aren't already in many collections!). According to Jared, the lizards are easily camouflaged in a wide variety of landscapes and can stay still - very still. “They don’t move, not even if you step near them.”
The team traversed many acres of land, fending off scrapes and cuts from thorny branches and cacti for three days, with no luck finding horned lizards. Their task became even more difficult when hurricane Carlotta blew in.
After a frustrating first few days, the team headed to Chilpancingo, Guerrero, after locals notified them of horned lizards in the area. “The sun had come out for a little while and the lizards were out,” said Jared. They quietly watched as two male giant horned lizards bobbed their heads and wagged their tails at each other while competing for a female. “You feel like you are looking back in time when you see their horns, scales, and eyes,” said Jared.
Though the lizards may seem like a portal to a bygone era, their habitat and survival faces serious threats today. In some places like Chilpancingo, Mexico, their natural habitats are already being overrun by new farms. That’s where the importance of research comes in.
By collecting and studying specimens - and investigating the diversity of species - researchers like Adam and Jared, are able to provide invaluable information to the scientific and conservation communities.
After five grueling days in the field, the team managed to catch all three species of horned lizard they hoped to find. They are now part of the collection at the Burke Museum and Adam is comparing each species' DNA in his research to understand how horned lizards adapted and evolved.
Learn more about Dr. Leaché's research on his lab website, or visit our website to learn more about Herpetology at the Burke Museum.
By Cathy Britt, Digital Communications
Photos courtesy of Jared Grummer. Video courtesy of Dr. Adam Leaché.
The three horned lizards caught in Mexico are of genus Phrynosoma:
P. braconnieri: short-tail horned lizard
P. taurus: bull-horned lizard
P. asio: giant horned lizard