There are currently around 60 species of the South American burrowing rodent tuco-tuco. The high number of species is due to the fact that these rodents have undergone enormous levels of chromosomal evolution, which makes defining the many different species a challenging task.
Good species definition is essential for planning conservation approaches in tuco-tucos. Certain groups of tuco-tucos are listed in the IUCN Red List of Threatened Species which is why redefining a species could change the threat level of certain groups of the animals.
Named for its bell-like call, which can be heard from its underground burrows, the gopher-like tuco-tuco is endemic to the southern cone of South America and is distributed along Brazil, Perú, Bolivia, Uruguay, Chile and Argentina. The burrowing animals dwell in very contrasting environments such as grasslands, the Puna desert, sandy coastal plains and forests.
Fascinating to biologists, the tuco-tuco has managed to survive for thousands of years in harsh climates. Various members display differing levels of sociability and only a minority of tuco-tucos are social. Nevertheless tuco-tucos are colonial, since they build their galleries very close to each other. Some adults share burrows and the females stay near their birthplaces and frequently nurse each other’s young. With around 60 identified species, tuco-tucos vary physically, in terms of colour, skeletal characteristics, and other features. They are varied chromosomally too. Scientists believe the key for the colonization of the animal’s diverse habitats is probably due to their subterranean lifestyle, which generates homogeneous underground conditions (similar temperature, humidity, etc).
The issue of species delimitation has long been debated between biologists. Different specialists advocate for distinct and partially incompatible species, leading to different conclusions about species boundaries and numbers of species. These incompatibilities emerge from considering different biological properties upon which several alternative concepts are based. Some biological species definitions require intrinsic reproductive isolation while others require shared specific mate recognition or fertilization systems. Because hybrids are less fertile, this causes the population to disperse.
Scientists have looked into 26 populations of the tuco-tucos from the Corrientes province in north east Argentina and integrated the results of other genetic characteristics studies. In their study published in the journal Mammalia on the solitary Corrientes tuco-tuco, the scientists integrated chromosomal studies, mitochondrial phylogenies and genetic variability analyses. By applying their approach, the Argentinian researchers identified seven independently evolving groups of the studied tuco-tucos. This identification might influence their status on the IUCN threatened and endangered species list.
One of the former species definitions retained its original status in light of this research, whereas two other definitions were redefined. Moreover, four other groups of the rodents were proposed based on their habitats localisation, including a population from the region of Paraje Sarandicito and three populations distributed at both sides of the Iberá wetland. This work contributes to the discussion of tuco-tuco species definition and is a revision of the different historical proposals for delimiting species in the tuco-tucos form the Corrientes province in Argentina.
As a result of this study, some small populations are now being regarded as new species and this might be enough to put these groups of tuco-tucos in the spotlight of conservation efforts.
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See also: Video of a tuco-tuco