Invasive behaviour of Gleditsia triacanthos in Spain
Gleditsia triacanthos (Leguminosae) is a tree species native to Eastern USA which has been introduced to South America (Argentina, Uruguay), Australia, South Africa and the EPPO region. Its invasive range includes California, Australia and Argentina. Although widely planted in the EPPO region, G. triacanthos has, until now, not been reported as being invasive. In Spain, G. triacanthos was first introduced in the 19th century as an ornamental species in cities and along roadsides and for erosion control along riverbanks. In the Iberian Peninsula, G. triacanthos has been recorded as planted or as a transient species. However, in 2019, a population was discovered in the Southwest of Spain spreading over 1.9 km along the Guadiamar River. The population structure includes seedlings, young vegetative saplings and large adult flowering and fruiting individuals, the latter often forming dense spiny thickets that restrict access. Measures of trunk perimeter showed the dominance of juveniles with trunks ≤ 0.1 m (57.8%, 244 individuals), but trunk perimeters greater than 0.4 m represented ca. 20% of all individuals found (84 out of 422 individuals). Currently, the ecological impact ofG. triacanthos along the Guadiamar River has not been studied but it colonises areas that should be occupied by native vegetation. It is recommended that the species is eradicated from this area and the habitat is restored. The seeds of G. triacanthos can remain viable for long periods due to its thick, impermeable seed coat. Therefore, any management action must be monitored during a sufficient time to ensure eradication has been achieved.
Sources
Dana ED, García-de-Lomas J, Jiménez-Cantizano FA, Verloove F (2022) Gleditsia triacanthos L. (honeylocust, Leguminosae): first record as an invader of riparian woodland in Southern Spain. BioInvasions Records 11 (in press).