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Researchers holding pythons. Credit: UTA
Florida has become a paradise for invasive species in the United States, but Burmese python is perhaps the best known of foreign residents of this state. These giant snakes, from Southeast Asia, have established themselves in recent decades and thrive even in their new environment.
"In Burmese pythons, we have observed the rapid establishment and expansion of an invasive population in Florida, quite distinct from the ecological point of view of Southeast Asia and which probably imposes an ecological selection. important to the invasive population of Burmese pythons, "said Todd Castoe, professor of biology at the University. from Texas to Arlington and director of Castoe Lab. "This situation had all the features of a system that allowed for rapid adaptation, so we were excited to test this possibility using advanced genomic approaches."
The researchers initially sought to determine if the pythons could have adapted to an extreme freeze in Florida in 2010. They generated data for dozens of samples before and after freezing. By scanning areas of the Burmese python genome, they identified parts of the genome that had changed significantly between the two periods, providing clear evidence of the evolution occurring over a very short period of time in this population.
"The 2010 freeze in Florida resulted in a documented 40 to 90% field mortality in invasive Burmese pythons, so if evolution and adaptation occurred, we knew we would have to see it during this period, which would have imposed a very strong bottleneck in selection. "Castoe said.
"We used a technique commonly known as genome analysis, which identifies areas of the genome that appear to be subject to strong natural selection, which may contain important genes for adaptation that could have allowed a subset of this genome to population to survive these freezing events, "he added.
The researchers expected to find genes in these areas that were important for potential cold adaptation, but after looking at the data more closely, a different signal began to appear that tells a more general story of adaptation in this area. invasive population.
"We continued to see evidence of adaptation in genes related to cell division, organ growth, and tissue development, which, it is true, surprised us at first. finally appeared that there was a link with a parallel project in the laboratory that uses Burmese Pythons as a model system for understanding the growth of regenerative organs, where tissues are negatively regulated during of fasting, then regenerated according to cyclic patterns corresponding to the feeding cycles of most pythons.apt to the way they regenerated organ systems according to their food ecology, "said Daren Card, a recently graduated doctorate. student in the Castoe lab who worked on this project for his thesis.
Based on the working hypothesis that invasive Burmese pythons may adapt to more regular feeding opportunities in Florida, researchers have collected additional ecological, functional and morphological genomic data to understand the frequency with which pythons feed and if there are physiological changes consistent with more factors. regular diet.
"These additional analyzes showed that Florida's Burmese pythons were constantly feeding and that the morphological and gene expression patterns of the tissues favored a better regulated physiological state in fasting pythons." This is alarming because it has has already been shown that these snakes have major negative impacts on endemic populations of mammals and birds of southern Florida, including the Everglades National Park, and our data suggested that, through rapid adaptation, they were only improving, being an effective invasive predator, "Card added.
UTA biology president, Clay Clark, congratulated the team for this work, which provides tangible evidence that evolution can occur extremely rapidly in natural populations and that this rapid evolution can result in changes major in very complex traits affecting the physiology and ecology of vertebrates.
"These results offer an unprecedented perspective on how quickly a vertebrate population can evolve, while building new links between genomic adaptation and complex physiological changes related to the ecological impacts of invasive species," Clark said. . "This is a particularly important work given UTA's strategic focus on the global impact on the environment."
Explore further:
Could a super snake emerge from the Everglades pythons? New DNA study raises possibility
More information:
Daren C. Card et al, New ecological and climatic conditions result in a rapid adaptation of invasive Florida Burmese pythons, Molecular ecology (2018). DOI: 10.1111 / mec.14885
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