By Emma Steigerwald
“When I was a child and the rain did not come,” adults sometimes told us, “my mother had me carry a frog far from the water, so that its distressed song would call the rain”.
“Make sure you don’t annoy the frogs,” people would warn my team. “When they are upset, the lightning falls”.
“Make sure you return those frogs when you’ve finished. If you don’t, the springs will dry”.
The cultural importance of amphibians in the most remote reaches of the Cordillera Vilcanota in the Peruvian Andes became more obvious each day that I spent there. People’s relationship with these animals is not an affectionate one: for the most part, they find the concept of contact with frogs disgusting or frightening. Still, a culture that depends on the success of their potatoes, tarwi, and alpaca will pay close attention to the creatures to whom they attribute sway over precipitation patterns. Communities that genuinely lose alpaca, homes, and people to lightning strikes will have respect for the creatures to whom they attribute sway over electrical storms. Therefore, when frog populations began disappearing in the early 2000s, Quechua herders broadcast their concerns (Seimon et al 2017). These reports motivated scientists to begin long-term amphibian monitoring in the Cordillera Vilcanota (Seimon et al 2017). Conversations with this monitoring team drew me to begin the first landscape genetic project ever based in the region, which I hoped to pursue without “annoying the frogs”!
I had my first field season this spring 2018, supported by the Tinker Summer Research Grant from Berkeley’s Center for Latin American studies. I was accompanied by local guide and horsedriver Gumercindo Crispin, as well as two students from the Universidad Nacional San Antonio Abad de Cusco: Yonatan Jared Guevara Casafranca and Peter Frank Condori Ccarhuarupay.
In their dedicated work with the Marbled water frog, Marbled four-eyed frog, and Warty toad, the long-term monitoring team has found the pandemic fungal disease chytridiomycosis implicated in the reported die-offs (Seimon et al 2017). The team was also amazed to find all three species at elevations hundreds of meters higher than had ever been previously registered (Seimon et al 2007). Accelerated glacial melt, which had entirely transformed the Cordillera in the last century, had also unlocked new habitat for these frogs to colonize (Seimon et al 2007).
The situation of these Cordilleran frogs captivates me because I am interested in problems relating to conserving wild populations. Here, I saw the convergence of several pressures: glacial melt, climate-driven range shifts, a novel pathogen, and the potential for restored animal movement across a mountain chain that has served as a barrier for perhaps thousands of years. I wondered if my particular toolkit, landscape genetics, could lend insight into how these pressures are interacting. Rapid range expansion and new or restored animal movement across deglaciated mountain passes will impact the genetic characteristics of wild populations (e.g. Ibrahim et al 1996, Excoffier 2004, Kolbe et al 2008, Pfaff et al 2001). These characteristics are, in turn, integral to whether populations will adapt, cope with new threats like diseases, and finally persist in the long term (Bonin et al 2007). Since climate change is causing species across taxa and across the world to alter their ranges (Parmesan 2006), rapid deglaciation is proceeding in tropical and temperate zones alike (Berger et al 2017), and novel disease threats are emerging at an accelerated rate (Daszak et al 2000), it is critical that we examine the impacts of these pressures and how they interact.
Ecologists are driven by the understanding that no element of an ecosystem stands independently– not even humans. For this reason, I find wisdom in the ancient beliefs that were shared with us about the Cordilleran frogs. I suspect that, in the grand scheme of things, the presence of frogs is indeed important for streams to flow. I suspect that, ultimately, the health of frogs is indeed important for the rains to fall. As scientists, we currently understand only small parts of that larger puzzle. While we catch up, I am going to trust that deeper wisdom, letting it inspire my effort to understand the forces we unknowingly exert on the wildlife that surrounds us.
Berger, A., Yin, Q.Z., Nifenecker, H. and Poitou, J., 2017. Slowdown of global surface air temperature increase and acceleration of ice melting. Earth’s Future, 5(7), pp.811-822.
Bonin, A., Nicole, F., Pompanon, F., Miaud, C. and Taberlet, P., 2007. Population adaptive index: a new method to help measure intraspecific genetic diversity and prioritize populations for conservation. Conservation Biology, 21(3), pp.697-708.
Daszak, P., Cunningham, A.A. and Hyatt, A.D., 2000. Emerging infectious diseases of wildlife–threats to biodiversity and human health. Science, 287(5452), pp.443-449.
Excoffier, L., 2004. Patterns of DNA sequence diversity and genetic structure after a range expansion: lessons from the infinite‐island model. Molecular Ecology, 13(4), pp.853-864.
Ibrahim, K.M., Nichols, R.A. and Hewitt, G.M., 1996. Spatial patterns of genetic variation generated by different forms of dispersal during range expansion. Heredity, 77(3), p.282.
Kolbe, J.J., Larson, A., Losos, J.B. and de Queiroz, K., 2008. Admixture determines genetic diversity and population differentiation in the biological invasion of a lizard species. Biology Letters, 4(4), pp.434-437.
Parmesan, C., 2006. Ecological and evolutionary responses to recent climate change. Annu. Rev. Ecol. Evol. Syst., 37, pp.637-669.
Pfaff, C.L., Parra, E.J., Bonilla, C., Hiester, K., McKeigue, P.M., Kamboh, M.I., Hutchinson, R.G., Ferrell, R.E., Boerwinkle, E. and Shriver, M.D., 2001. Population structure in admixed populations: effect of admixture dynamics on the pattern of linkage disequilibrium. The American Journal of Human Genetics, 68(1), pp.198-207.
Seimon, T.A., Seimon, A., Daszak, P., Halloy, S.R., Schloegel, L.M., Aguilar, C.A., Sowell, P., Hyatt, A.D., Konecky, B. and Simmon, J.E., 2007. Upward range extension of Andean anurans and chytridiomycosis to extreme elevations in response to tropical deglaciation. Global Change Biology, 13(1), pp.288-299.
Seimon, T.A., Seimon, A., Yager, K., Reider, K., Delgado, A., Sowell, P., Tupayachi, A., Konecky, B., McAloose, D. and Halloy, S., 2017. Long‐term monitoring of tropical alpine habitat change, Andean anurans, and chytrid fungus in the Cordillera Vilcanota, Peru: Results from a decade of study. Ecology and Evolution, 7(5), pp.1527-1540.
EMMA STEIGERWALD is a National Science Foundation graduate research fellow and PhD student in the Department of Environmental Science, Policy and Management. Her research is motivated by the belief that, to manage wild populations with defined outcomes in mind, we should integrate our understanding of the complex ecological and evolutionary processes they are subjected to on diverse and ever-changing landscapes. She comes to Berkeley from a project working on an ecological corridor for endangered, range-restricted parakeets of the Ecuadorian Andes, and is glad to now be working on a project that also considers the implications of ecological corridors for infectious disease. Emma received a 2018 Tinker Summer Research Grant awarded by the Center for Latin American Studies.