Vegetative multiplication and resilience of Crassula multicava Lem.: challenges for mechanical eradication in the Canary Islands

Abstract

Biological invasions in oceanic archipelagos threaten island ecosystems due to the rich endemic biodiversity they support. Crassula multicava is a succulent species found in shaded environments along the subtropical coastline of South Africa. In the Canary Islands, this species invades zones within the Canarian laurel forest domain. Mechanical eradication tasks raise serious doubts about their effectiveness because this species is capable of regrowing from vegetative propagules. This work evaluates the regrowing capacity of leaves, leaf fragments, stems, and stem fragments of C. multicava under different treatments. For this purpose, 18 individuals of C. multicava were collected in a population inhabiting the Bosque del Adelantado (El Rosario, Tenerife), with 9 subjected to irrigation every two days and 9 subjected to natural environmental conditions, serving as controls. For each individual, 8 leaves and 8 stem sections were selected and subjected to darkness, burial and cutting treatments. After seven weeks, some propagules exhibited the ability to regrow, developing roots and/or shoots. However, the irrigated propagules showed a faster regrowth rate than the controls, with longer roots and larger shoots. This work demonstrates the high invasiveness of Crassula multicava due to its high vegetative multiplication and resilience under different temperature, light, and humidity scenarios. These results explain why mechanical eradication is not always effective and highlight the need for continuous monitoring at the action sites.