Senna alata in Mexico
Senna alata (Fabaceae) is a shrub native to South America. The species has been used as an ornamental plant and is currently introduced and naturalised in tropical areas of Africa, Asia, Oceania and North America, where it is widespread. The species can impede access to waterways and is poisonous to livestock. It can form dense stands which outcompete native plant species and can outcompete biodiversity. In Mexico, the species has been introduced to a number of areas (Veracruz, Sinaloa, Morelos, Michoacán, Tamaulipas, Nayarit, Jalisco, Colima, Puebla, Guerrero, Oaxaca, Tabasco, Chiapas, Campeche, Yucatán and Quintana Roo) with the earliest records from the 1890s. S. alata was discovered in the Baja California peninsula, in the Cape region (Mexico) for the first time in 2013. The plant was first noticed in gardens, along valleys, and in tropical deciduous forest vegetation along waterways. In total, 294 plants were recorded in both the Santiago and San José del Cabo oases (small, fragile relict mesic habitats in the arid desert ecosystem). In the oasis of Santiago, populations of S. alata were scattered, and consisted mainly of mature plants. In the oasis of San José del Cabo, density was higher, but individuals were less than 10 cm in height. 60% of the population consisted of seedlings and young plants. Mature plants were mostly in full bloom and early fruiting stages. In Los Barriles and Santa Anita, a few plants were recorded, some of which were found in gardens. The authors highlight that the current invasion appears to have started from propagules escaped from gardens and moved through the valleys by flood events. Management of the species should occur in the in the natural habitats where it is invading.
Sources
Navarro JJP, Rodriguez-Estrella R (2020) The exotic invasive candle bush Senna alata (L.) Roxb. In Baja California Peninsula, Mexico, a new threat for relictual oasis. BioInvasions Records 9, 29-36.