Graminoid Invasion in an Insular Endemism Hotspot and Its Protected Areas

Abstract

Invasive plant species are increasingly altering species composition and the functioning of ecosystems from a local to a global scale. The grass species Pennisetum setaceum has recently raised concerns as an invader on different archipelagos worldwide. Among these affected archipelagos are the Canary Islands, which are a hotspot of endemism. Consequently, conservation managers and stakeholders are interested in the potential spreading of this species in the archipelago. We identify the current extent of the suitable habitat for P. setaceum on the island of La Palma to assess how it affects island ecosystems, protected areas (PAs), and endemic plant species richness. We recorded in situ occurrences of P. setaceum from 2010 to 2018 and compiled additional ones from databases at a 500 m × 500 m resolution. To assess the current suitable habitat and possible distribution patterns of P. setaceum on the island, we built an ensemble model. We projected habitat suitability for island ecosystems and PAs and identified risks for total as well as endemic plant species richness. The suitable habitat for P. setaceum is calculated to cover 34.7% of the surface of La Palma. In open ecosystems at low to mid elevations, where native ecosystems are already under pressure by land use and human activities, the spread of the invader will likely lead to additional threats to endemic plant species. Forest ecosystems (e.g., broadleaved evergreen and coniferous forests) are not likely to be affected by the spread of P. setaceum because of its heliophilous nature. Our projection of suitable habitat of P. setaceum within ecosystems and PAs on La Palma supports conservationists and policymakers in prioritizing management and control measures and acts as an example for the potential threat of this graminoid invader on other islands.

Human impact, climate and dispersal strategies determine plant invasion on islands

“…To standardize for local disturbances, we sampled elevational transects in roadside plots (Bacaro et al, 2015; Jakobs et al, 2010; Maděra et al, 2013) because they provide not only repeatable settings ideal for comparing non‐native species establishment even across biogeographic regions (Alexander et al, 2011; Seipel et al, 2012) but also provide habitat for endemic plant species such as roadside cliffs that shelter endemics from anthropogenic disturbances and introduced herbivores (Irl et al, 2014). Roads are often regarded as important vectors for the spread of non‐native species (Walentowitz et al, 2019). In this context, human impact, which is measured as road density per km 2 , represents the probability of introduction of non‐native species to a certain location of an island.…”

Assessing the Potential Replacement of Laurel Forest by a Novel Ecosystem in the Steep Terrain of an Oceanic Island

“…Extremely steep and unstable slopes restrict access to the sites. Further, only estimating the current distribution of the alien species would be problematic because the current situation is just a snapshot of the potential occupied space and ecological niche on the island [64]. Therefore, it is important to combine in-situ and RS data with modelling approaches.…”

RAPID METHODS TO SELECT FACULTATIVE PATHOGENS ON INVADER Cenchrus setaceus

“…It is a strong fire-promoting invader of arid and semi-arid areas, and it has been introduced into South Africa, Australia, South Europe, USA, Hawaii, and Canary Islands (Adkins et al, 2011;González-Rodríguez et al, 2010;Poulin et al, 2005;Rahlao et al, 2014;Rodríguez-Caballero et al, 2017;Sinden et al, 2004). Alien invasive plants represent one of the major threats to native biodiversity especially on islands ecosystems due to their remoteness, small populations and high extinction rates (Walentowitz et al, 2019). In these environments, the influx of these species combined with other factors such as anthropogenic pressure and climate change lead to "the perfect storm", invasive species being the main driver of biodiversity loss (Caujapé-Castells et al, 2010).…”