Salamanders that breed in the fall are less likely to disperse
July 27, 2017
Pond-breeding salamanders face increasingly perilous treks as the space between suitable breeding ponds widens or is degraded by loss of tree cover and moist microhabitats. However, a new study from the University of Missouri suggests that a salamander’s dispersal success may depend more on when it breeds than on landscape obstacles. The finding has implications for management strategies of salamander populations and other pond-breeding species within forest ecosystems throughout the world.
“Salamanders serve as vital links in forest food chains, and their population size and recovery from major disturbances can help predict the health of forest ecosystems,” said Jacob Burkhart, a graduate student in the Division of Biological Sciences and lead author of the study. “It’s crucial that we have a better understanding of how salamanders move, or disperse, across their landscape as well as what factors encourage or discourage their movement in order to make sound decisions about managing their populations.”
Burkhart and his colleagues use DNA extracted from tissue samples to track salamanders. “With DNA, we can assess genetic relatedness and gene flow between populations and individuals. When we associate gene flow with geography, we can say how these salamanders are moving across the landscape,” he said.
The researchers collected tissue samples from four species of pond-breeding salamanders at Fort Leonard Wood, Missouri. Two of the species (Ambystoma maculatum and Notophthalmus viridescens) breed in the spring and two (A. annulatum and A. opacum) in the fall. They also measured features of the landscape, including distance between ponds, the amount of tree cover, distance from ravines, and soil wetness.
When the researchers analyzed the DNA, they found less gene flow among breeding populations of the two fall-breeding species as compared to the two spring-breeding species. In other words, the DNA shows that salamanders that breed in the fall are moving to new ponds less often than salamanders that breed in the spring. Distance between ponds and various landscape features could not fully explain the observed genetic differences.
“Even though some habitat features did seem to affect dispersal, we found that, for all four species, breeding season was a better predictor than habitat of the observed genetic differences,” said Burkhart. “Practically, what this says is that landscape variables are not quite as important for fall breeders for describing the observed differences in dispersal ability.”
For those concerned with managing salamander populations, Burkhart said the study serves as a reminder that not all salamanders are alike. “Our finding is a good reminder of the need to manage for a specific species. When writing a conservation plan or when choosing a surrogate species, you need to consider a lot more about your target species, including its life history traits, in addition to its interactions with the landscape,” he said.
The article, titled “The influence of breeding phenology on the genetic structure of four pond-breeding salamanders,” appears in the July issue of the journal Ecology and Evolution.
Teaming up with Burkhart on the study were Lori Eggert, Associate Professor of Biological Sciences, and a number of current and former MU students mentored by the late herpetologist and MU Curators’ Professor Ray Semlitsch. The alumni include Bill Peterman, Ph.D. ‘08, Emily Brocato, B.S. ‘14; Kim Romine, B.S. ‘13, Britt Ousterhout, Ph.D. ‘16; and Tom Anderson, Ph.D. ’16. Current students include Freya Rowland, a doctoral candidate in the Division of Biological Sciences, and Madeline Willis, an undergraduate in the Department of Biochemistry. An additional coauthor, Dana Drake, also worked in the Semlitsch lab.
The research was funded by a grant from the Department of Defense (RC2155).
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