Exotic terrestrial flatworms on islands: a threat to biodiversity
The recent article "DNA barcoding reveals new records of invasive terrestrial flatworms (Platyhelminthes, Tricladida, Geoplanidae) in the Macaronesian region", co-authored by several IPNA researchers, reports the presence of three species of exotic terrestrial flatworms in Madeira and the Canary Islands.
The term Macaronesia, used to refer to the region that includes the archipelagos of the Azores, Madeira, Salvajes, Canary Islands and Cape Verde, comes from the Greek words 'makarios' and 'nesos', translated into English as 'Fortunate Islands'. Although the nickname 'fortunate' may derive from their mild climate, one of the archipelago's major gifts is its outstanding biodiversity. As a consequence of their isolation from the mainland, the islands' flora and fauna have evolved to give rise to a large number of species that are unique to these archipelagos. However, this extraordinary occurrence is under threat due to the presence of exotic species in these ecosystems. An example of this is the terrestrial flatworms.
There are very few terrestrial flatworm species on islands since, owing to a very permeable epidermis, they do not survive long periods of immersion in seawater. Therefore, most of the flatworms that inhabit these areas have arrived as a result of human activity, mainly through the shipping of plants, in whose pots they are hidden in the humid soil. The main impact they may have on the areas where introduced comes from their trophic ecology, as they are generalist predators. In other words, they feed on a wide variety of invertebrate species. Whereas the effect of flatworms on local fauna is less worrying in anthropogenic environments, such as greenhouses or gardens, once settled in a natural environment, their effect could be devastating.
In a recent article published on Zootaxa, "DNA barcoding reveals new records of invasive terrestrial flatworms (Platyhelminthes, Tricladida, Geoplanidae) in the Macaronesian region", researchers reported the presence of three species of exotic flatworms in Madeira and the Canary Islands for the first time. Their morphological identification, often difficult, was complemented with molecular identification techniques. For this purpose, the 'barcoding' technique was used, i.e. the sequencing of a fragment of the cytochrome oxidase I gene, which is found in the mitochondrial genome and has a distinctive sequence for each species. In this way, the species Obama nungara and Endeavouria septemlineata were detected in Madeira and the Canary Islands. Likewise, the species Caenoplana coerulea, a flatworm already reported in the Canary Islands in 2017, was also registered for the first time in Madeira. More than just recording data on the species, this finding is significant because these flatworms have been found in natural ecosystems such as the laurel forests of the Anaga Rural Park (Tenerife) or in Funduras and Ribeiro Bonito (Madeira). While in continental areas of Europe the climate is too cold for these tropical species to colonise natural areas, the islands of Macaronesia seem to offer these undesirable visitors such conditions that would allow not only their settlement but also their expansion. Their presence in the laurel forests of the Canary Islands and Madeira, home to a rich fauna of native invertebrates, undoubtedly poses a major threat and a challenge to the conservation of these unique ecosystems.
Suárez, D., Pedrianes, J. R. and Andújar, C. (2022): DNA barcoding reveals new records of invasive terrestrial flatworms (Platyhelminthes, Tricladida, Geoplanidae) in the Macaronesian region. Zootaxa.
Caenoplana coerulea image by Daniel Suárez.