Adrian Quijada-Mascareñas

The goal of my research is to understand the biogeographical and phylogenetic basis of biological diversification. My approach is a combination of molecular phylogenetic analysis and geographical information systems. My hope is to contribute to a better understanding of the ecological and biogeographic mechanisms of the origin and maintenance of biodiversity and the evolutionary consequences of ongoing habitat transformation produced by human activities.

My present research program is mostly located in the U.S. Southwest-Northern Mexico region. The main themes are listed below:

Genetic Consequences of Climate Change in the Sky Islands: Integrating Genetic, Ecological, and Climate Change Databases.

Melanie Culver, Hans-Werner Herrmann and I will investigate the genetic consequences of climate change in the Sky Islands region. Climate change will fragment and/or alter range of wildlife populations. Our model system is the Sky Islands region of the southwest US and northwest Mexico, an area known for its forested mountaintops surrounded by seas of arid grasslands and deserts. Under a warming climate, forested island mountaintops and their animal inhabitants will become further isolated. We hypothesize that climate change will alter the population genetics of small vertebrates in the Sky Islands. We will build an integrated database where genetic information on small vertebrates will be linked to habitat and climate information from the sampling localities. Molecular marker data will include microsatellites and mitochondrial DNA. In addition, DNA samples will be permanently stored in a DNA-based database bank. This permanent database will provide a baseline of genetic diversity in the Sky Islands, and framework for assessing the future effects of climate change on population genetics. Our database will enable us to identify losses in genetic diversity and changes in population dynamics, and correlate these changes with climate and related habitat change.

Molecular Systematics and Biogeography of the Black-tail Rattlesnake

In collaboration with Wolfgang Wüster (University of Wales), Kelly Zamudio (Cornell University), Rob Bryson (University of Nevada) Hans-Werner Herrman (University of Arizona) and Oscar Flores Villela (UNAM) we are performing a phylogenetic and biogeographical analysis of the black-tail rattlesnake. The black-tail rattlesnake Crotalus molossus is considered an allied taxon of the Neotropical group and is one of the most widespread rattlesnakes (second after the Neotropical rattlesnake). C. molossus presents considerable morphological and habitat variation. In previous studies, my colleagues and I determined the existence of several ancient lineages. Our data demonstrate that C. molossus is highly heterogeneous and paraphyletic, falling into well differentiated clades dating back to the Miocene, suggesting that it may represent a species complex. My colleagues and I have been gathering DNA samples from the entire distribution range of C. molossus in order to resolve the phylogeny of this group. In addition, we will incorporate lineage-specific niche modelling to test the hypothesis that different lineages may respond differentially to habitat preferences during their evolution. In collaboration with Steve Mackessy, we will explore venom composition and proteome evolution in the context of phylogenetic and natural selection as factors promoting venom evolution.

Evolutionary Patterns of Venom Composition in Rattlesnakes of the Gulf of California Islands and Baja California Peninsula

At least fifteen species of rattlesnakes are known in the Gulf of California region. With Steve Mackessy and Gustavo Arnauld (Centro de Investigaciones del Noroeste, Baja California, Mexico), we are running a project on venom variation of rattlesnakes in a phylogeographic framework. Venom phenotypes undergo more natural selection pressure than morphological characters and may reflect the effects of different ecological constraints. By comparing different genetic lineages we can analyze the patterns of venom variation and composition comparing island versus mainland. We are gathering venom, DNA samples and ecological data from island and mainland in Baja California and Sonora. Gustavo Arnauld is in charge of ecological data. Steve Mackessy will supervise the venom analysis and I will provide phylogeographic information from DNA samples.

Herpetofauna of Sonora: Evolutionary and Biogeographical Patterns.

In collaboration with Philip C. Rosen (University of Arizona), Erik F. Enderson (Drylands Institute), Robert L. Bezy (Natural History Museum of Los Angeles County), Matt Goode (University of Arizona), Cecil Schwalbe (University of Arizona) & Dale S. Turner (The Nature Conservancy) I am performing a comprehensive analysis of the richness and biogeography of the herpetofauna of the Mexican state of Sonora. This effort includes field work and collecting of unexplored areas and to resolve many of the remaining taxonomic issues using morphology and DNA. Also we are exploring the evolutionary patterns associated to the Neartic-Neotropical transitional nature of Sonora. We expect as the most important outcome of this project ansystematized collection of voucher specimens and DNA of the herpetofauna of Sonora, an urgent need that has been pointed out in our recent publications.

Photo footnote: In 1989 I was bitten by a Gila monster while doing field work in the coastal foothills of southern Sonora. Unusual conditions and stupidity joined to produce an event of mild consequences. After six-eight hours of pain and swollen finger, tachycardia and breath difficulties, symptoms disappeared. Since then my encounters with Heloderma lizards produce an emotional connection. These extraordinary creatures count on their arsenal just as a way to survive from predators including humans. Score: Gila monsters 2, Herpetologists 0.