Biology

Invasive species (V): Cat’s claw or Carpobrotus: an ornamental problem

Cat ‘s claw is the common name for two invasive species of the Carpobrotus family present in Spain, C. acinaciformis and C. edulis . The scientific name of the genus refers to the fact that its fruits are edible (from the giego ” karpos “, fruit, and ” brotus “, edible).

As for its common name, cat’s claw, it comes from the shape of its leaves . These plants grow at ground level, forming a network of clonal individuals connected by their stems (which in clonal plants are called “stolons”). If this network of stolons is broken, the individuals are able to survive and if they are transported they give rise to a new population.

Both species are very similar, the color of their flowers being the feature that distinguishes them: in Carpobrotus edulis the petals are yellow ...
Both species are very similar, the color of their flowers being the feature that distinguishes them: in Carpobrotus edulis the petals are yellow …

Cat’s claws generally grow in the littoral area, both in dunes and on cliffs , covering the ground with a dense bush that prevents the development of other species. Both species are very similar, the color of their flowers being the distinguishing feature: in Carpobrotus edulis the petals are yellow while in C. acinaciformis they are pink or purple . The flowers reach a large size, over 10cm, and their striking appearance makes them appreciated as an ornamental plant.

While clonal reproduction is useful for plants to spread rapidly once established in a place, the production of seeds allows their movement over long distances. However, for various reasons, the main displacement vector of this species is humans.

Biological invasion of Carpobrotus

These two species, like many others in the genus Carpobrotus , are native to South Africa . Carpobrotus edulis was introduced in several countries (such as Australia or the USA) to immobilize the dunes of the coastal areas, due to its ability to form extensive clumps.

In California the plant was introduced extensively during the first half of the 20th century . Unfortunately, this plant has enormous potential to become invasive due to its biological characteristics, such as its high resistance and rapid growth. The species spread rapidly in the Mediterranean causing serious environmental problems.

Cat's claw or Carpobrotus
Cat’s claw or Carpobrotus

In Europe there is a peculiar case of mutualism between invasive species involving Carpobrotus edulis and the black rat ( Rattus rattus ) . The black rat, native to Asia and invasive in Europe, feeds on the fruits of Carpobrotus and carries the seeds of the plant with its feces.

The seeds are also carried by other small mammals native to Europe, as well as gulls. As for the enormous flowers of Carpobrotus , it is worrying that they are indirectly affecting the rest of the plants that inhabit the littoral zone, by attracting the attention of pollinating insects and preventing them from fertilizing native species .

Situation in Spain of cat’s claw

It is not clear if C. edulis was introduced in Spain to immobilize dunes or for purely ornamental purposes, but today it has spread throughout the entire coast of the Iberian Peninsula, the Canary Islands and the Balearic Islands.

The situation is especially serious on the coast of Catalonia and the Cantabrian Sea area. C. acinaciformis , for its part, is less widespread but has the same range of distribution in our country as C. edulis .

Its use as an ornamental plant is greater , because its violet flowers have great beauty. Due to this characteristic, and how simple it is to cultivate the species (for the asexual reproduction of this plant, it is enough to cut a fragment of the stem with leaves and put it in a pot), it is common to see the plant in the gardens of the houses in coastal areas . There has also been the case of a city council that has used it to decorate the surroundings of public buildings or a park.

Fortunately, in recent years common sense has prevailed over the trend of altering the beaches and sandy areas of our country and measures are being taken to control Carpobrotus . Its eradication is as simple as uprooting the bushes and preventing human hands from continuing to spread the species, but the lack of initiative (and budget) on the part of the administrations means that the elimination tasks of this plant remain incomplete, or extend in time so that the plant is able to recover.

For now it seems that we will have to live with Caprobrotus on our beaches, with no prospect of getting rid of this invasive species.

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