Morphology of the invasive 'Carpobrotus' (Aizoaceae) in Europe: Malta as a case study

Abstract

Since the late 19th century, different taxonomic views have been reported for Carpobrotus species occurring in the Maltese Islands, where the latest treatments imply two varieties of C. edulis and the doubtful occurrence of C. acinaciformis. Taxonomic inconsistencies are possibly derived from the poor understanding or misinterpretation of morphological characters. Moreover, the hybridogenous morphotypes resulting from horticultural advances make the determination of Carpobrotus even harder, especially with the application of outdated identification keys which do not take hybrids into account. The difficulty in determining Carpobrotus spp. has been expressed in several recent accounts within the Mediterranean region. A taxonomic investigation was carried out by applying eleven morphological characters adopted from recent monographs on 25 populations present in Malta. Three taxonomic units have been retrieved from the analyzed sample, where C. acinaciformis s.l. has been confirmed to represent all the purple-flowering populations and C. edulis s.s. for the yellow-flowering ones. Emphasis was given on the interpretation and understanding of distinctive morphological characters by employing a standardized method of assessment aided by images. This comparative morphological study resulted in a new characteristic in the leaves of C. edulis, by which it could be easily distinguished from C. acinaciformis in the vegetative state. A detailed discussion about the two different morphotypes of C. acinaciformis s.l. and dichotomous keys to distinguish Carpobrotus taxa are also provided.

<i>Carpobrotus</i> Management in a Mediterranean Sand Dune Ecosystem: Minimum Effective Glyphosate Dose and an Evaluation of Tarping

“…Br. (Aizoaceae) genus is one of the foremost invaders of Mediterranean coastal ecosystems (Campoy et al 2018;Giulio et al 2020;Mifsud, 2021). In Spain, Carpobrotus is present in every coastal peninsular and insular province (Sanz-Elorza et al 2004).…”

“…The Carpobrotus genus, which is native to South Africa, was widely used as an ornamental and for soil stabilization (Sanz-Elorza et al 2004;Campoy et al 2018;Mifsud, 2021). However, it has now dispersed from the planting areas, becoming an extensively distributed invasive species present in five different continents, and has become widely naturalized in many coastal habitats, such as active and stabilized dunes, coastal scrub, and rocky coast (Campoy et al 2018;Mifsud, 2021). Carpobrotus grows horizontally and radially in all directions and forms monospecific carpets which attain near-dominance (Campoy et al 2018).…”