The San Antonio frog, Hyla molleri, is a widely distributed species in the Iberian Peninsula. Despite its small size, it has a greater tolerance to cold than other amphibians; in fact, there are populations that live at sea level, on the Atlantic and Cantabrian coasts, and others at more than 2,000 meters of altitude in the Central System.
Researchers from the National Museum of Natural Sciences (MNCN-CSIC) and the University of Évora (Portugal) have discovered that, contrary to what happened with other amphibians, the San Antonio frogs managed to survive the Quaternary glaciations and today they continue to maintain high levels of genetic diversity.
The extinctions caused by the glaciations did not occur only in northern Europe, but also affected populations in northern Spain. There were particularly unfavorable periods during the last glacial period, about 20,000 years ago, which affected species such as the gallipato, Pleurodeles waltl, or the spur toad, Pelobates cultripes.
“Over time, both species have managed to recolonize these areas, but it has been at the cost of a strong loss of genetic diversity in the new populations. In fact, we have verified that populations in the south of Spain generally show much higher genetic diversity than those that inhabit the north ”, explains Martínez-Solano.
By cons, the San Antonio frog maintains high levels of genetic diversity in areas both north and south of its range and it does not appear that the climatic changes of the last 140,000 years in the Iberian Peninsula have affected the species.
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Apparently, its greater tolerance to cold conditions and its dispersal capacity, compared to other amphibian species with which it habitually coexists, helped it successfully survive the last ice ages in its Iberian glacial refuge. "This little frog has prevented major extinctions, as well as losses of genetic diversity, which worsen the current situation of other typical Mediterranean amphibians," concludes Martínez-Solano.
The migratory factor of the San Antonio frog in the face of climate change
One of the factors that conditions the The response of the species to climatic changes is their dispersal capacity. Thus, groups such as amphibians, which develop their complete life cycles in areas of a few square kilometers, are more sensitive to these changes, since as a general rule they are not able to migrate to other areas with more favorable climates at the necessary speed.
In fact, your response as a species highly dependent on the ability to disperse and colonize new areas during periods of favorable weather. The low mobility of some species, among other factors, is behind many of the widespread extinction episodes that occurred during the colder periods in most of central Europe.
Sánchez-Montes, G .; Recuero, E .; Barbosa, A.M .; Martínez-Solano, I. 2019. «Complementing the Pleistocene biogeography of European amphibians: Testimony from a southern Atlantic species«. Journal of Biogeography. DOI: 10.1111 / jbi.13515.
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