In biology, we call “endemism” a living being that, naturally, lives exclusively in a defined geographical area. A species can become endemic to a place in different ways. It is a restricted condition in space and time. In other words, a species endemic to a region today need not have always been so, nor why continue to be so in the future. In addition, the region referred to when speaking of endemism can be of highly variable size.
from big to small
When it is said that an organism is endemic to a place, a hierarchical biogeographic classification is used in kingdoms, ecozones, regions, provinces and sectors.
For example, the alder is a tree that is widespread in Europe, but does not appear anywhere else; it is therefore an endemism of the so-called Palearctic ecozone —the area that encompasses all of Europe, North Africa and the entire Asian region north of the Himalayas—, and more specifically, of the Euro-Siberian and Mediterranean regions.
From a much more restricted area is, for example, the Iberian lynx , endemic to the southernmost provinces of the Mediterranean region of the Iberian Peninsula.
The Oro- Cantabrian oak ( Quercus orocantabrica) , one of the last tree species discovered in Spain, is even more restrictive, appearing exclusively in the Oro-Cantabrian province, represented by the Cantabrian mountain range, from Alto Carrión, through Picos de Europa, to Los Ancares.
Another tree endemic to a very small region is the Spanish fir , endemic to the so-called Betic province, specifically the so-called Ronda sector , which ranges from Sierra de las Nieves to Grazalema, and to the south as far as Sierra Bermeja and Estepona.
There may even be even more limited endemisms in its range; it is not uncommon to find them in insular ecosystems, or in others that resemble them. To an animal that lives in water, a lake is nothing more than an island surrounded by land. For a plant that does not survive high mountains and cannot disperse over long distances, a valley is, after all, a low-lying island surrounded by mountains. And for an animal adapted to subterranean life and that does not tolerate the outside, a cave is still an island.
At this extreme we find, for example, animals such as Apoduvalius saledoi , a carabid beetle that lives exclusively in the Refidieyu cave, in the municipality of Muñera, Asturias, and nowhere else in the world.
Types of endemism
There are several ways in which a species can reach the level of exclusivity of being present only in such a restricted area as a concrete and specific cave. And these forms are defined by different factors that are part of the natural history of the species.
On the one hand, we distinguish two types of endemism, according to their evolutionary history.
We call neoendemism to that species that has evolved recently, and that the restriction in its distribution is due to the fact that it has not yet had time to disperse further.
In opposition, there are paleoendemisms , species with a long evolutionary history and whose geographical restriction is due to other reasons. One of them may be the existence of biogeographic barriers that have prevented the species from dispersing, as is the case with most of the endemic species found on the islands. On the other hand, there are what we call relict endemisms , species that in the past were widely distributed, but that suffered an extinction in most of the area in which they were distributed, and were relegated to a few or only protected areas. That was the case of the pinsapo, for example.
The repeated influence of the last glaciations was the cause of the presence of a good part of the relict endemisms that exist in the Iberian Peninsula. In the example of the cave beetles, when the ice advanced, the insects that did not find refuge or migrated south, froze to death irremediably. Among these shelters were the caverns, areas where temperatures are very constant and are hardly influenced by the harsh weather conditions outside.
In each cave, the insects were subjected to a series of selective pressures, and evolution did its job, causing each population to end up transforming into a new species. A different one in each cave. Adapted to the new cave environment, when the ice retreats, the animals remain in their new habitat, which remains undisturbed.
The importance of its conservation
Biodiversity is at risk. That’s a fact. One of the main objectives of conservation is to maintain as much biodiversity as possible. To do this, it is first necessary to know the biodiversity of a region. And endemisms can help determine priorities when establishing conservation systems. Frequently, the areas with the most endemism are also the most vulnerable to disturbance, indicating that they are deserving of special conservation status.
I dedicate this article to Professor José María Salgado Costas.
REFERENCES:
Carbajal Márquez, E., García Carrillo, J., et al. 2001. Description of a new Apoduvalius (Coleoptera: Caraboidea: Trechidae) from Asturias. Heteropterus Journal of Entomology , 1, 1-6.
Morrone, JJ 2008. Endemism. In Encyclopedia of Ecology (pp. 81-86). Elsevier.
DOI: 10.1016/B978-0-444-63768-0.00786-1Rivas-Martínez, S. 1987. Memory of the vegetation series map of Spain.
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