Recovery of indigenous butterfly community following control of invasive alien plants in a tropical island’s wet forests

Abstract

Invasive alien species pose one of the highest threats to biodiversity, especially in isolated oceanic islands where high rates of both endemism and extinction risk also usually prevail. Few studies have investigated the impact of invasive alien plants on butterflies in insular ecosystems, despite butterflies representing a key indicator group for terrestrial arthropod diversity. Using the Pollard Technique, we quantified butterfly species richness and abundance in eight wet lowland forest areas invaded by alien plants, principally the strawberry guava (Psidium cattleianum Sabine) on the tropical volcanic island of Mauritius, and compared the results with paired adjacent forest plots that had been weeded of alien plants between 2 and 12 years previously. Butterfly assemblages in weedinfested and weeded forests were distinctly different with higher species richness and much higher butterfly abundance in the latter. At least some of these differences seemed attributable to weed removal effects on forest structure, but understanding the precise mechanisms involved will require further study. The results suggest that alien plant invasion may have contributed to the extinction of certain endemic taxa and can increase the likelihood of butterfly species extinction by reducing population sizes through reduced habitat quality. Such a shift in a forest's butterfly assemblage is likely to have negative effects on both their indigenous predators and the plants they pollinate. It is argued that in order to maintain butterfly and other arthropod diversity and function in these forests, alien plant control must be maintained and extended beyond the current 1% of surviving forest remnants.

The effectiveness of classical biological control of invasive plants

“…Nonetheless, classical biocontrol resulted in a reduction in the target plant and increases in diversity in invaded areas, which is likely to impact other trophic levels due to the provision of additional niches (Florens et al . ). These impacts occurred in the absence of additional control and restoration efforts, such as seeding.…”

Toward an Era of Restoration in Ecology: Successes, Failures, and Opportunities Ahead

“…Local extinctions of desirable native species accompanied by dominance of exotic species with strong impacts on ecosystem processes commonly have slowed or stopped recovery in both terrestrial and aquatic restorations (Florens et al 2010, Hilt et al 2010, Tanentzap et al 2009). For instance, a 70-year restoration of a shallow lake via reduction of nutrient loading reestablished some aspects of community structure, but owing to the regional loss of rare species, diversity remained lower than in the reference period (Louette et al 2009).…”

Removing an exotic shrub from riparian forests increases butterfly abundance and diversity

“…Removal of tamarisk trees (Tamarix ramosissima Deneb) from riparian areas along a river in Colorado improved butterfly habitat but not all species responded to removal (Nelson and Wydoski, 2008). Florens et al (2010) studied the effect of removing invasive plants from an island forest and found that forests with invasives removed had much greater butterfly abundance and richness than unweeded forests. Here we report the effects of removing privet on butterfly communities and compare them to untreated, heavily invaded control plots and to ''desired future condition'' plots that never had extensive privet cover.…”