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The "Cargola del Cap de Creus" may be becoming extinct from its only Iberian locality

End of the study project of this endemic species from the south of France and Cap de Creus.

Fig1: Área de distribución de Eordium foetidum (L.) L’Hér. La mayoría de localidades se encuentran en el sur de Francia y la única localidad ibérica se mantiene en el Cap Norfeu, una pequeña península rocosa del sur de Cap de Creus

The work and the analysis of the data collected in various campaigns throughout this year on the "Cargola del Cap de Creus" (Erodium foetidum (L.) L'Her.) have already been completed, within the framework of a project that BioSciCat has developed within the "Unique" program, with the support of the Fundación Biodiversidad, the Ministry for Ecological Transition and the Demographic Challenge, and the Department of Territory and Sustainability of the Generalitat of Catalonia and the collaboration of the Cap de Creus Natural Park.

The project has shed light on various important aspects of the biology and ecology of this small plant whose future prospects are not at all promising. The “Cargola del Cap de Creus” grows on hillside and cliffs with stony or rocky soil, of calcareous nature. In the south of France, for example, it does so in the Cévennes, Corbières, La Clape, Garrigues and the foothills of the eastern Pyrenees. In the Iberian Peninsula, its only known population resides in Cap Norfeu, a small peninsula located in the southeast of Cap de Creus, taking up an area of less than one hectare.

One of the results has been to verify that the one from Cap Norfeu is, with great probability, the only Iberian population of the species, after the efforts to identify it in 10 localities of the Cap de Creus were unsuccessful, which, a predictive mathematical model elaborated ad hoc, pointed out as potentially suitable for hosting the “Cargola del Cap de Creus”.

Fig2: Los pulvínulos de la “cargola del Cap de Creus” se secan completamente en verano y al final de esta estación brotan nuevas hojas y elementos florales que se desarrollarán a lo largo del otoño (izquierda). A la derecha se compara el aspecto del mismo pulvínulo en plena primavera (arriba) y al final del verano (abajo).

The peculiar life cycle of the “Cargola del Cap de Creus” exemplifies its adaptation to the Mediterranean bioclimate. The plant, which grows in rock gaps and between the stones, remains green throughout the winter and begins to develop flowers at the end of this season. It acquires its maximum radiance in spring, a time when it shows off numerous flowers and fruits. With the arrival of summer and drought, the green parts of the plant (leaves, flowers and fruits) completely dry up and die. In this way, it overcomes this unfavorable time, with the minimum expense of energy and resources. At the end of summer, new leaf shoots and flower buds begin to emerge from the woody stump, which will develop throughout the autumn.

Fig5: Comparación de los recuentos efectuados en 2010 y 2020.
Fig4: Resultados de los trabajos de recuento de individuos. Para ello, el área de distribución se dividió en distintos sectores. El color de cada sector refleja la densidad de individuos. Para cada sector las cifras indican el número mínimo y máximo de individuos (por las incertidumbres derivadas de la identificación de pulvínulos en las imágenes de los acantilados tomadas con un dron).

But the result that has raised the most concern has been the count. The individuals of the "Cargola del Cap de Creus" were counted directly on the ground and with the help of high-resolution images taken by a drone on the contiguous cliffs. This work yielded the minimum number of 4808 individuals. If we do not take into account new localities population found in Cap Norfeu throughout this project (371), it turns out that, in ten years, the population has seen its numbers decreased by a third.

The regressive tendency must be confirmed with subsequent counts, since we do not know the interannual variability in the growth of new individuals. Regardless, the most obvious potential threats to the species, such as forest fires, grazing, the progress of woody vegetation or the anthropic pressure, do not seem to have been, during the last decade, sufficiently relevant to explain the observed deterioration. Climate change could explain, at least in part, this population decline. A regressive tendency has also been reported in some of the French populations, according to the INPN (Inventaire National du Patrimoine Naturel).



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