The exotic invasive candle bush Senna alata (L.) Roxb. in Baja California Peninsula, México, a new threat for relictual oasis

Abstract

We recorded the invasive candle bush (Senna alata) for the first time in oases of southern Baja California peninsula in October 2013 and February 2015. Candle bush is likely an escape from residential plantings in this region. Data on density, plant cover, number of pods per plant, and seeds per pod are presented. In the oasis of Santiago, candle bush plant density was low and contained mainly mature plants, which made up 90% of the total population. In the oasis of San Jose del Cabo, population density was higher, but individuals were mostly shorter than 10 centimeters in height, and 60% of the population consisted of seedlings and young plants. Mature plants were seen mainly in full bloom and early fruiting stages. Candle Bush is invading very dry climates in oasis systems, this is the first documented record of the species invading this kind of wetlands and even starting to invade tropical deciduous forest around arroyos. The introduction pathways and time since the introduction of candle bush into the peninsula are unknown, but no records existed before 2013 when we found the population. We strongly recommend eradicating this invasive species from Baja California oases now, while it is in the early stages of invasion.