The most comprehensive genetic analysis of the American bullFrog in Brazil has been done by researchers at the University of So Paolo and the State University of Campinas. The world's main Invasive Amphibian is the Bull Frog.
There is an article in Scientific Reports.
There are at least two populations of bullFrogs. The first bullFrogs arrived in Brazil. Most of the South and Southeast has this population. The other is limited to Minas Gerais and occurs in a small number of other states. The study was part of his master's research at the Institute of Biosciences.
The native of North America was brought to Brazil in 1935 to make meat. It is now grown throughout the South and Southeast and has spread in the wild with adverse impacts on local flora.
The importance of preventing escape from Frog farms is reinforced by the results of the study.
It would be possible to know the provenance of each animal if the population were different. Monitoring and law enforcement would be possible if analysis of a captured bullFrog pointed to a region where the animal had escaped. The Brazilian groups have less diversity than other countries.
The policy of the state.
Specific genes were analyzed in over 300 tissue samples. BullFrogs are found in seven of the nine Brazilian states. The majority of the population belong to the same group of animals that descended from North America in 1935 and spread across the country in response to incentives offered as a matter of state policy.
The other population is descended from a group of animals brought to Minas Gerais in the 70s. The breeding pairs probably came from the US. The species is native to the eastern US.
There is anecdotal evidence of others in the 1980s and 2000s and isolated initiatives by some producers. The animals could have had the same origin or interbred with the existing population if there were other introductions. We simply didn't collect samples from these individuals.
Bull Frog farming peaked in Brazil in the 1980's. At that time, some 2,000 farms were being produced. There were a number of factors that contributed to the decline in activity. Animals were able to escape into the wild.
The species is easy to reproduce and grows quickly until individuals reach 15 cm. Lus Felipe Toledo, one of the co-author of the article, said that it's resistant to disease and can coexist with the fungi and Viruses that have led to a global decline in populations of other amphibian. The State University of Campinas has a Biology Institute.
An invasion of the United States.
When animals in question invade wilderness areas, it becomes a major environmental problem. Competition with native species for food and other resources can result in adverse effects. Most anurans rely on acoustic communication to locate, appraise and choose mates, so alterations can have a significant impact on reproduction.
The transmission of diseases is one of the most serious environmental problems. BullFrogs affect native wildlife in various ways due to their spread through the Atlantic rainforest. They are carriers of the chytrid fungus and ranaviruses. The two pathogens have led to the extinction of species.
chytridiomycosis is an infectious disease that can cause death from cardiac arrest if it is not treated. At least 500 species of salamanders have been wiped out by it.
Ranaviruses has been found in the Atlantic Rainforest, which is associated with the decline in populations of these animals. The Ministry of Agriculture, Livestock and Food Supply (MAPA) in Brazil is required by law to destroy all animals if they are found with chytrid fungus or ranaviruses.
Most of the frog farms we visited were found to have chytrid fungus. Bull Frogs are moving a lot around the country. Toledo works with the state departments of agriculture to try to improve the legislation and control bullFrog breeding and marketing.
Frog farms have consolidated the same populations with low genetic diversity by exchanging animals, according to a study. The practice is not bad. Brazil sells 400 metric tons of frog meat on the domestic market.
There is a lot of interest in preventing diseases caused by chytrid fungus and ranaviruses. Producers cannot sell all the meat they produce. There needs to be better oversight and inspection. If large meatpackers were interested in the product, there could be an alternative strategy. It would have to be enforced by both producers and consumers.
More information: Gabriel Jorgewich-Cohen et al, Genetic structure of American bullfrog populations in Brazil, Scientific Reports (2022). DOI: 10.1038/s41598-022-13870-2 Journal information: Scientific Reports
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