Epiphytic Orchid Recovery After Invasive Woody Plant Removal in Mauritius

Abstract

Anthropogenically introduced alien species pose the second largest threat to global biodiversity, yet their impact on orchids, one of the most species-rich and threatened plant families, has received little attention. This gap is especially pronounced on tropical oceanic islands, where forest ecosystems are highly susceptible to the spread of invasive alien plants (IAPs). This study aimed to quantify the impact of woody IAP removal on native epiphytic orchids in Mauritius, an island with protected forests heavily invaded by strawberry guava (Psidium cattleyanum). Epiphytic orchids were surveyed in an invaded control hectare and a treatment hectare that underwent woody IAP removal in 1996 in Black River Gorges National Park. Results showed that woody IAP removal significantly increased epiphytic orchid population densities, especially in the forest understory. This may be due to an increase in suitable bark habitat for epiphytic orchid colonization as woody IAP removal likely alleviates competition for light and fosters more native tree recruitment. This research suggests that woody IAP removal can effectively catalyze native epiphytic orchid recovery in the tropical forest of an oceanic island. Since orchids were found to occur more frequently on larger host trees, conservation management efforts should prioritize woody IAP removal in the better-preserved, mature protected forests of Mauritius to most effectively restore native epiphytic orchid communities.