Endemic plant species are more palatable to introduced herbivores than non-endemics

Abstract

Islands harbour a spectacular diversity and unique species composition. This uniqueness is mainly a result of endemic species that have evolved in situ in the absence of mammal herbivores. However, island endemism is under severe threat by introduced herbivores. We test the assumption that endemic species are particularly vulnerable to generalist introduced herbivores (European rabbit) using an unprecedented dataset covering an entire island with enormous topographic, climatic and biological diversity (Tenerife, Canary Islands). With increasing endemism, plant species are more heavily browsed by rabbits than non-endemic species with up to 67% of endemics being negatively impacted by browsing, indicating a dramatic lack of adaptation to mammal herbivory in endemics. Ecosystems with high per cent endemism are most heavily browsed, suggesting ecosystem-specific vulnerability to introduced herbivores, even within islands. Protection of global biodiversity caused by disproportionally high endemism on oceanic islands via ecosystem-specific herbivore control and eradication measures is of utmost importance.

Spatiotemporal dynamics of plant diversity and endemism during primary succession on an oceanic‐volcanic island

“…Nevertheless, endemics on La Palma have been shown to profit from virgin cliff habitats where primary succession is initiated, for example, after the construction of roads (Irl et al, 2014a). However, such roadside cliff habitats protect endemics from introduced herbivores (Irl, et al, 2014a), which preferentially feed on endemics (Cubas et al., ). Selective browsing by introduced herbivores might alter patterns of endemics in primary succession (Cubas et al., ; Irl et al, ) but to what degree remains unknown.…”

The effect of small-scale topography on patterns of endemism within islands

“…As we sampled up to an elevation of 674m, the majority of our study area is located near the peak range for exotic species, indicating that exotics are largely excluded from the barrancos. As well as exotic plants, barrancos may also restrict the access of exotic herbivores to certain areas, particularly the steep barranco sides, which may act as refugia from exotic herbivores that preferentially feed on endemic plant species (Cubas et al 2019).…”

Graminoid Invasion in an Insular Endemism Hotspot and Its Protected Areas

“…A common disturbance on islands is the browsing of introduced herbivores. However, P. setaceum seems not to be negatively affected by browsing, although the graminoid mainly occurs at low elevations where introduced rabbit density is high [18]. Very likely, this results from the sharp blades of the plant using silica phytoliths as a mechanical defense against herbivory [74].…”

“…This vulnerability is exacerbated by the introduction of alien and invasive species, which become the main driver of these losses [13,14]. On the Canary Islands, many endemic plant species are currently considered highly endangered as a result of invasive species [15][16][17][18]. The survival of endangered endemics will largely depend on adequately controlling invasive species based on scientifically sound knowledge of their distribution, population dynamics, and ecology.…”