Expansion Speed as a Generic Measure of Spread for Alien Species

Naturalization and invasion potential of Sesuvium portulacastrum L. recorded as alien species in Egypt

Sesuvium portulacastrum is a perennial halophyte of family Aizoaceae, non-native to Egypt, which was introduced from France ten years ago as an ornamental species. This study reports the detection of S. portulacastrum in the wild in Egypt. Voucher specimens were deposited in the Herbarium of Alexandria University (ALEX). A population of the species was recorded in the wild near Maruit Lake in the north-western coast of Egypt in 2018 during plant resources surveys of the region. The study aimed to assess the potential for S. portulacastrum to spread as an alien species through field observations and geospatial measurements under current conditions in its new habitat. The measured morphological parameters were higher than those recorded in its native habitats. The field observation for three years revealed that the species is proliferating and expanding in the investigated site forming large mats of mean size of up to 9 m2. The spatial extent of S. portulacastrum based on the EOO and AOO was quantified, and the expansion rate was estimated at 0.16 ha/year in the investigated site. The geospatial parameter used in the study will not only help in determining the spread rate of the alien species spatially and temporally, but also in its effective management through guiding managers in developing monitoring plans for the species under the changing climate uncertainty. Continuous monitoring and early detection of any potential threats of the introduced species are highly recommended, to avert any potential adverse impacts on native biodiversity and assess its behaviour in the wild habitat.