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Biology professors at Colorado State University have obtained a three-year, $400,000 National Science Foundation grant to study the effects of genes moving from one population to another.
Increasingly, wildlife managers are discovering the benefits of informing conservation action and policy with research on the genetics of populations. For example, relocation is a common management tool used to reintroduce species to environments where they used to occur or to augment declining populations, but moving animals or plants from one part of their range to another can have potentially disastrous effects. Disease can be brought in with the relocated individuals, or, mating between individuals from divergent populations – even if they are the same species –may cause populations to decline under some circumstances.
Chris Funk and Lisa Angeloni, assistant professors of biology at CSU, and their student teams tackle the dilemma of when to artificially induce migration between populations to rescue them from decline by getting up close and personal with Trinidadian guppies. These small fish, although not at risk of extinction themselves, make for an excellent model system to study the effects of introductions on local adaptation and population growth.
“This is a big question in evolutionary and conservation biology, but there haven’t been too many experimental studies to test these hypotheses,” said Funk.
Graduate students on the project – Sarah Fitzpatrick and Dale Broder, NSF Graduate Research Fellows – have spent the last several years in Trinidad and Tobago in the Caribbean to monitor native guppy populations in a long-term study following an introduction experiment. Fitzpatrick is also a 2012-2013 Global Sustainability Leadership Fellow through CSU’s School of Global Environmental Sustainability, also known as SoGES.
“We’re studying them in their native range,” Angeloni said. “Trinidad has pairs of contrasting environments with predictable differences. Guppies live in environments that are pretty different – some populations live with larger fish predators that eat them and others live in low predation environments.”
As the foreign guppies invade and mate with the native population, they may have negative effects by displacing the natives or introducing traits that were only useful in their previous environment. Or, the new neighbors might infuse new genetic material and aid in increasing population size. To untangle these possible effects, the guppy team is working in two streams in Trinidad.
Fitzpatrick spent much of the past two years in Trinidad taking monthly samples of every guppy within a given stream section, giving each fish its own unique tattoo and removing a few scales from each fish to bring back to CSU for genetic work. The tattoos allow the researchers to measure individual survival and track changes in population size, while the genetic sample allows them to identify each individual as a native, immigrant, or hybrid. This also will lead to a complete pedigree of the population to compare mating success among individuals.
“We’re going to be looking at how gene flow affects traits, individual fitness, and population dynamics in both those populations,” Funk said. “Does gene flow increase a population’s size or does it break down local adaptation?
“In conservation, if a population is declining, then one strategy is to grab individuals from a population doing well and move these individuals to the declining population in hopes of rescuing population growth. However, nobody really knows whether this strategy will work.”
The results of this study will aid in understanding when it is beneficial to translocate individuals into declining populations and when different measures should be taken to assure population persistence.
“We’re looking in depth at the cascading effects of gene flow on different levels – the trait, the individual organism, and the population,” said Angeloni, who studies behavioral ecology, including the evolution of reproductive behavior of fishes, the effects of human disturbance on wildlife behavior, and the reproductive ecology of species of conservation concern.
Broder is studying specific mating habits of guppies that are isolated in the lab in hopes of discovering how gene flow affects the mating system. First, the scientists had to measure traits in the wild, such as the number of dances males perform to engage females. They waited two years and took the measurements again to see how the immigrants and hybrids affected behavior.
Funk’s research focuses on basic and applied questions in evolutionary ecology. In 2012, he published a paper that revealed that the diversity of frogs in the Amazon Basin is much greater than previously recorded. The research, in collaboration with Ecuadorian researchers, could lead to greater understanding of how to save the frogs from extinction.