Researchers sequence genome of endangered tortoise to support conservation of the spur-thighed species in Spain

There are only two population centres on the Spanish mainland: one in the southeast, from the north of Almeria to the south of Murcia provinces, and the other located within the Doñana National Park

Europa Press

Malaga

Wednesday, 11 September 2024, 17:12

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Researchers from the ecology department of Miguel Hernández University of Elche (UMH) and the University of Alicante (UA) have managed to sequence the genome of the spur-thighed tortoise for the first time, using as a reference the genome of another tortoise native to America, but evolutionarily related to the spur-thighed species.

The results of this research, published in the scientific journal PLOS One, will allow the scientific community to support the conservation of these endangered animals. The spur-thighed tortoise (Testudo graeca or 'Greek tortoise') is one of the "most iconic" species of tortoises in the Mediterranean, the two institutions said in a statement.

There are two population centres on mainland Spain: one in the southeast, from the north of Almeria to the south of Murcia provinces, and one located within the Doñana National Park. The species is in danger of extinction in Andalucía and is included in the catalogue of threatened Species of Murcia's regional government and the Ministry of the Environment.

"Understanding the genetic diversity of animals can be very useful when it comes to conserving species such as the spur-thighed tortoise because the more we know, the better we can understand how these animals have adapted to their environment or what capacity they will have to face climate change," explained UMH researcher Andrea Mira Jover, principal author of the study.

Key scientific milestone

The genome is the complete set of DNA instructions found in a cell. Sequencing consists of reading all the genetic information that will be representative for a species, identifying this information (e.g. specific genes) and arranging them into chromosomes. The description of the genome of this species is a "key scientific milestone", as very few tortoises have been described at this level.

"These results will be a starting point to better understand the evolutionary history of the species and to solve questions related to its life history, such as the secret of its high longevity," said UA researcher Roberto Rodríguez-Caro.

He added that the publication of this reference genome will provide "key tools" for its conservation at a global level, as the species is classified as "vulnerable" according to the International Union for Conservation of Nature (IUCN) and requires "concrete measures" that are capable of preserving populations in the future.

The researcher has been working with this species for 15 years with the aim of obtaining information on its ecology, conservation and genetics, in collaboration with different national and international research centres.

Techniques

There are different techniques for obtaining complete genomes, depending on whether they read genetic information in long or short fragments. "In other words, if the entire DNA were a novel, some techniques read long sentences and others identify single words," explained Mira Jover.

"The chelonians are an ancient and very diverse taxonomic group - there are freshwater, marine and land turtles - but their genomic organisation is very similar," said the scientist, who added that tortoises "have evolved very slowly throughout their history and their genes are similar and are in the same position in the chromosomes".

Tortoises (Testudinidae) are the most endangered of all turtle families, but only five reference genomes are available, compared to 33 for sea and freshwater turtles. In this situation, the scientific community is faced with a "severe lack of resources" to help conserve tortoise populations.

The researchers used the known genome of Gopherus evgoodei, the so-called 'Sinaloense scrub tortoise', native to the desert of the United States and Mexico. "If you imagine the DNA double helix as a spiral staircase, each step of the staircase would be made up of so-called 'base pairs' containing smaller molecules," they explain. The size of a complete genome is measured by the number of base pairs. For example, the human genome has 3.2 billion base pairs containing about 25,000 genes.

This reference genome generated will be useful to answer questions about the evolutionary history of the spur-thighed tortoise and to investigate genes of interest in future studies. It will also be a useful tool for making better conservation decisions.

The study has also involved the work of researchers from the Zoological Museum of Dresden (Germany) and the Institut de Recherche pour le Développement (Montpellier, France).

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