{"294841":{"#nid":"294841","#data":{"type":"news","title":"Evolution in Species May Reverse Predator-Prey Population Cycles","body":[{"value":"\u003Cp\u003EPopulations of predators and their prey usually follow predictable cycles. When the number of prey increases, perhaps as their food supply becomes more abundant, predator populations also grow.\u003C\/p\u003E\u003Cp\u003EWhen the predator population becomes too large, however, the prey population often plummets, leaving too little food for the predators, whose population also then crashes. This canonical view of predator-prey relationships was first identified by mathematical biologists Alfred Lotka and Vito Volterra in the 1920s and 1930s.\u003C\/p\u003E\u003Cp\u003EBut all bets are off if both the predator and prey species are evolving in even small ways, according to a new study published this week in the journal \u003Cem\u003EProceedings of the National Academy of Sciences\u003C\/em\u003E. When both species are evolving, the traditional cycle may reverse, allowing predator populations to peak before those of the prey. In fact, it may appear as if the prey are eating the predators.\u003C\/p\u003E\u003Cp\u003EResearchers at the Georgia Institute of Technology have proposed a theory to explain these co-evolutionary changes. And then, using data collected by other scientists on three predator-prey pairs \u2013 mink-muskrat, gyrfalcon-rock ptarmigan and phage-\u003Cem\u003EVibrio cholerae\u003C\/em\u003E \u2013 they show how their theory could explain unexpected population cycles.\u003C\/p\u003E\u003Cp\u003EThe new theory and analysis of these co-evolution cycles could help epidemiologists predict cycles of disease and the virulence of infectious agents, and lead to a better understanding of how population cycles may affect ecosystems.\u0026nbsp; The research was supported by the National Science Foundation and the Burroughs Wellcome Fund.\u003C\/p\u003E\u003Cp\u003E\u201cOur work shows that co-evolution can yield new and unique behavior at the population scale,\u201d explained \u003Ca href=\u0022http:\/\/www.biology.gatech.edu\/people\/joshua-weitz\u0022\u003EJoshua Weitz\u003C\/a\u003E, an associate professor in the \u003Ca href=\u0022http:\/\/www.biology.gatech.edu\/\u0022\u003ESchool of Biology\u003C\/a\u003E at Georgia Tech. \u201cWhen you include evolution, the classic prey-predator dynamics have a much greater range of possible outcomes. We are not replacing the original theory, but proposing a more general model that opens the door to these new phenomena.\u201d\u003C\/p\u003E\u003Cp\u003EEvolution is often perceived as an historical event, noted Weitz, who also has a courtesy appointment in the Georgia Tech \u003Ca href=\u0022http:\/\/www.physics.gatech.edu\/\u0022\u003ESchool of Physics\u003C\/a\u003E. But organisms are evolving continuously, with certain phenotypes becoming dominant as environmental and other conditions favor them. In organisms such as birds or small mammals, those changes can be manifested in as few as ten generations. In microbial species with brief lifespans, evolutionary changes can happen within days or weeks.\u003C\/p\u003E\u003Cp\u003EEvolutionary changes can dramatically affect relationships between species, potentially making them more vulnerable or less vulnerable. For instance, if a mutation that confers viral resistance in a species of bacteria becomes dominant, that may change the predator-prey relationship by rendering the bacteria population safe from harm. More generally, co-evolutionary cycles can arise when predator offense is costly and prey defense is effective against low offense predators.\u003C\/p\u003E\u003Cp\u003E\u201cWith predator and prey co-evolution, you can see oscillations in which there are lots of prey around even when there are many predators, or lots of predators around even when there are very few prey,\u201d noted Michael Cortez, a postdoctoral fellow in the Weitz lab and first author of the paper.\u003C\/p\u003E\u003Cp\u003E\u201cWhen prey is abundant and there are few predators, it may be because there are many defended prey \u2013 prey that the predators can\u2019t eat,\u201d he added. \u201cWhen there are lots of predators around and few prey, it\u2019s because the prey are very good food sources and the predators are doing quite well.\u201d\u003C\/p\u003E\u003Cp\u003EIn their paper, Weitz and Cortez simulated models in which the evolutionary process was sped up to show how their theory of co-evolution would affect predator-prey population cycles. Speeding up the process allowed them to break the cycle up into smaller segments that could be analyzed in more detail. They then used the earlier observations of the changing abundances of the three pairs of predators and prey\u0026nbsp; -- leveraging data sets collected by other scientists \u2013 to show how the models would apply.\u003C\/p\u003E\u003Cp\u003E\u201cAlthough the structure of the cycles in these three systems had been noted as unusual by the authors who observed them, there had been, as yet, no unified theoretical framework from which to make sense of such as radical departure from the classic signature of predator-prey interactions,\u201d Weitz said.\u003C\/p\u003E\u003Cp\u003EScientists have long studied how the interaction between species affects overall populations in ecosystems. Weitz and Cortez believe their new model will give scientists a broader and more complete picture of the complex process.\u003C\/p\u003E\u003Cp\u003E\u201cThis study identifies how adaptation between two species and interactions between their numbers can result in something different from what you would get if you just had the interaction between the numbers,\u201d said Cortez. \u201cThis is something that will show up across many ecological systems. We can now explain broad trends that occur in vastly different systems using a theoretical approach, and the fact that we can identify the mechanism responsible for it is unique to our study.\u201d\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThis research was supported by the National Science Foundation under Award DMS-1204401, and by the Burroughs Wellcome Fund. Any conclusions or opinions expressed are those of the authors and do not necessarily represent the official views of the sponsoring agencies.\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECITATION\u003C\/strong\u003E: Michael H. Cortez and Joshua S. Weitz, \u201cCoevolution Can Reverse Predator-Prey Cycles,\u201d (Proceedings of the National Academy of Sciences, 2014). \u003Ca href=\u0022http:\/\/www.pnas.org\/cgi\/doi\/10.1073\/pnas.1317693111\u0022 title=\u0022www.pnas.org\/cgi\/doi\/10.1073\/pnas.1317693111\u0022\u003Ewww.pnas.org\/cgi\/doi\/10.1073\/pnas.1317693111\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EGeorgia Institute of Technology\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003E177 North Avenue\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cstrong\u003EAtlanta, Georgia\u0026nbsp; 30332-0181\u0026nbsp; USA\u003C\/strong\u003E\u003Cbr \/\u003E\u003Cbr \/\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986) (\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or Brett Israel (404-385-1933) (\u003Ca href=\u0022mailto:brett.israel@comm.gatech.edu\u0022\u003Ebrett.israel@comm.gatech.edu\u003C\/a\u003E).\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EAccording to a study published in the journal Proceedings of the National Academy of Sciences, co-evolutionary changes in species may reverse traditional predator-prey population cycles, creating the appearance that prey are eating the predators.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Co-evolution in species may reverse traditional predator-prey population cycles, creating the appearance that prey are eating the predators."}],"uid":"27303","created_gmt":"2014-05-04 19:29:14","changed_gmt":"2016-10-08 03:16:22","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2014-05-05T00:00:00-04:00","iso_date":"2014-05-05T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"294831":{"id":"294831","type":"image","title":"Predator-Prey Relationship","body":null,"created":"1449244511","gmt_created":"2015-12-04 15:55:11","changed":"1475894993","gmt_changed":"2016-10-08 02:49:53","alt":"Predator-Prey Relationship","file":{"fid":"199359","name":"bobcat-rabbit.jpg","image_path":"\/sites\/default\/files\/images\/bobcat-rabbit_0.jpg","image_full_path":"http:\/\/hg.gatech.edu\/\/sites\/default\/files\/images\/bobcat-rabbit_0.jpg","mime":"image\/jpeg","size":1477731,"path_740":"http:\/\/hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/bobcat-rabbit_0.jpg?itok=X-uz7f80"}}},"media_ids":["294831"],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"154","name":"Environment"},{"id":"146","name":"Life Sciences and Biology"},{"id":"135","name":"Research"}],"keywords":[{"id":"92711","name":"co-evolution"},{"id":"3028","name":"evolution"},{"id":"11599","name":"Joshua Weitz"},{"id":"92731","name":"population cycle"},{"id":"13478","name":"predator"},{"id":"92721","name":"predator-prey"},{"id":"13479","name":"prey"}],"core_research_areas":[{"id":"39441","name":"Bioengineering and Bioscience"},{"id":"39541","name":"Systems"}],"news_room_topics":[{"id":"71911","name":"Earth and Environment"}],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003EJohn Toon\u003C\/p\u003E\u003Cp\u003EResearch News\u003C\/p\u003E\u003Cp\u003E\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E\u003C\/p\u003E\u003Cp\u003E(404) 894-6986\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}