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The foxes of the Americas

Deforestation promotes encounters between different species and leads to the emergence of hybrids

Hoary fox procreate in the state of São Paulo

Cintia Possas Pampas fox and hoary fox (photo) procreate in the state of São PauloCintia Possas

There are species of fox scattered across every continent except the Antarctic, but foxes enjoy little popularity in Brazil. It’s not that they have a bad reputation: their existence actually goes nearly unnoticed, despite the fact that they are often run over by vehicles in the streets. Even biologists do not usually pay them much heed. But the group led by geneticist Eduardo Eizirik of the Pontifical Catholic University of Rio Grande do Sul (PUC-RS) has started reconstructing the history of the diversification of these animals in South America, and showing how changes in the environment can genetically affect these species—although it is uncertain whether these changes are problematic for the animals.

According to a paper published in the July/September issue of the journal Genetics and Molecular Biology, the hoary fox (Lycalopex vetulus) was the first species of this group of canids to exhibit evolutionary divergence from the North American lineages, between 1 and 1.3 million years ago, after a common ancestor moved southward across the Isthmus of Panama. Of the eight species of South American foxes, it is the only one endemic to Brazil, inhabiting all areas of the Cerrado savannah, and thus accustomed to open landscapes. Analyses conducted by geneticist Ligia Tchaicka as part of her doctoral research under Thales de Freitas of the Federal University of Rio Grande do Sul (UFRGS), with Eizirik as co-advisor, show that the emergence and diversification of the genus Lycalopex occurred after the species had entered South America.

This conclusion fits in with the theory developed by other groups, which posits that a rise in sea level split South America into two parts during the Pleistocene. The split likely left one group in eastern Brazil, giving rise to the hoary fox, and the other in western Brazil, where it expanded into the Andes region and diversified there, giving rise to the other species.

When she compared the genetic material from five species of South American foxes, Tchaicka, now a professor at the State University of Maranhão (UEMA), saw another enigma: some individuals that had been classified as Pampas fox (L. gymnocercus)—which is typical of southern Brazil, as well as Uruguay, Argentina, Paraguay and Bolivia—had mitochondrial DNA (received only from the mother) more similar to the South American gray fox, L. griseus, which is widely distributed throughout Chile and Argentina—on the other side of the Andes. One possible explanation would be that these foxes are really hybrids—a surprising conclusion since, despite the overlapping distributions of the two species, there are no records of places where they both exist.

More recent but as-yet-unpublished studies have pointed to another locus of hybridization, in this case between the Pampas fox and the hoary fox, in the state of São Paulo. “With the gradual disappearance of the Atlantic Forest, the fox has been occupying open areas and expanding its distribution outside the domain of the Cerrado,” Eizirik explains. “We had already conceived of the possibility that it could end up encountering the Pampas fox.” The formation of hybrids is nothing new to Eizirik, who has found similar results in wild cats (see Pesquisa FAPESP Issue nº 159).

That is precisely what has been shown by the work of biologist Fabricio Garcez during his master’s studies, and now in his current doctoral research at Eizirik’s laboratory at PUC-RS. Some animals that resemble L. vetulus have the mitochondrial DNA of L. gymnocercus, a mixture corroborated by markers in the nuclear genetic material that each animal receives from both the father and the mother. Garcez is now conducting genomic analyses, and his preliminary findings indicate that all the foxes sampled so far from São Paulo State combine genetic material from the two species. The results also suggest that at least some of these animals were not from the first crossbred generation, offering an indication that the hybrids in this case are at least partially fertile.

“We’re seeing that the DNA of L. gymnocercus is invading the populations of L. vetulus more often than it is not,” says the PUC professor. This hybridization is quite probably caused by the changes brought about by human occupation, which causes him some concern. “We don’t yet know whether this process will cause profound genetic changes that could affect the existence of the species,” says Eizirik, who presented these discoveries at a symposium on 20 years of conservation genetics in Brazil at the Brazilian-International Congress of Genetics sponsored by the Brazilian Society of Genetics, held in Caxambu, Minas Gerais, in September 2016.

In the interest of expanding the research and deepening our understanding of the genetic development of these foxes, Eizirik maintains that the ideal step would be to form a network—of both researchers and citizens not connected with academia—that could gather and share information, photographs, and even samples of biological material taken from animals run over by vehicles (the most frequent donors of genetic material), as well as data obtained on field expeditions and animals held in captivity.

Scientific article
TCHAICKA, L. et al. Molecular assessment of the phylogeny and biogeography of a recently diversified endemic group of South American canids (Mammalia: Carnivora: Canidae). Genetics and Molecular Biology. V. 39, No. 3, p. 442-51. July/September 2016.