Jared Grummer: Studying hybrid zones between Argentinean lizard species with loads of DNA
|At the end of every rainbow is a doctoral dissertation. Photo by Jared Grummer.|
I am a fourth year Ph.D. candidate and I have been interested in hybrid zones for a little while. Hybrid zones offer a unique view into the evolutionary processes that either generate or extinguish species. You see, “species” is a word that the non evolutionary biologist is certainly familiar with, but few know the incendiary debates that regularly occur on campuses worldwide that cover ideas of what defines a species. Just like species, the definition of a species is mutable and evolves over time, largely based on how data are collected. Before Darwin, species have been diagnosed based on morphological (physical/external) characteristics that separate different types of organisms; this lizard is green, and that one is yellow, therefore they are different species. Nowadays, species are mostly being defined based on something all organisms share: DNA.
DNA sequencing technologies that have recently been developed allow us to sequence a large portion of an organism’s genome, therefore shedding light on not only its past, but the past of its ancestors. I still, however, recognize the importance of morphology in determining species limits, those boundaries that separate species. When morphological variation within a “species” is high, it is suspect that more than one species may be present. This point brings us to the lizards!
I am studying a group of lizards in Argentina, the Liolaemus fitzingerii group, that belongs to a lizard genus (Liolaemus) that is confined to South America. This is an exceptional genus of lizards because some species exist at over 5,000m, whereas others are found at sea level; some are herbivorous, and some even give live birth. Furthermore, they are relatively poorly understood and between 10-15 new species are described each year! Regarding the L. fitzingerii group, approximately 15 species are currently recognized, but the geographic and biological boundaries that separate many of these species are not clear.
|One of the first male Liolaemus melanops we found during this fieldwork! Photo by Jared Grummer.|
|The governmental building of my collaborators Luciano Avila and Mariana Morando. Photo by Jared Grummer.|
|Variation in male dorsal patterning from individuals collected at the same locality. Photo by Jared Grummer.|
Sometimes, hybrid zones are found in “ecotones”, where two distinct habitat types come together. However, in this area of Patagonia, the habitat appears to be homogeneous (at least to the human eye).
|Liolaemus melanops habitat in Chubut Province. Photo by Jared Grummer.|
My collaborator Luciano and I have sampled ~10 sites in northern Chubut and southern Rio Negro provinces spanning an area over 100km that potentially represents a hybrid zone between 2-3 species in the L. fitzingerii group. Now that I have the lizards, the next step will be to collect and analyze DNA from across the genomes of these individuals to see the extent of gene flow between these various populations along a morphological gradient. Half of the vouchers, or physical specimens, will be sent to the Burke Museum of Natural History and Culture; the other half will remain with my collaborators at the National Central Patagonia Institute in Puerto Madryn. These specimens will be a critical reference when analyzing the DNA, as we will be looking for congruence or conflict between morphological and molecular data in this area of putative hybridization between species.
I will leave you with some photos of the other cool things that we have been seeing. Stay tuned with results of this research in the spring!
|A gecko, Homonota darwinii, that is one of nine Homonota species in Argentina. Photo by Jared Grummer.|
|A male Liolaemus melanops. Photo by Jared Grummer.|
The herpetology lab in CENPAT where we processed all of our samples. Photo by Jared Grummer.
|Luciano overlooks a rocky outcrop and ranch in Chubut Province. Photo by Jared Grummer.|
|Flamingos leaving their laguna. Photo by Jared Grummer.|
A southern sea lion colony during breeding season at Punta Norte on the Valdez Peninsula. Photo by Jared Grummer.