Invasive alien palm Pinanga coronata threatens native tree ferns in an oceanic island rainforest

Abstract

Invasive ornamental plants are a global problem that can have severe impacts on native biodiversity, especially on islands. To determine whether the invasive, ornamental ivory-cane palm Pinanga coronata could be displacing native biodiversity, we investigated its co-distribution with native tree ferns in a Fijian rainforest. We recorded the abundances of P. coronata and tree ferns and related these to environmental variables using linear models and generalised linear mixed-effect models (GLMMs). Distance to an introduction site was the most significant factor predicting the palm’s distribution and abundance, suggesting that its current distribution is limited by insufficient time for wider dispersal. P. coronata cover was strongly and negatively related with the abundance of native tree ferns and the palm may therefore be displacing native tree ferns. This relationship was strongest with tree fern seedlings and weakest with mature tree ferns, implying that the palm is preventing the establishment of native tree ferns. This study thus provides strong circumstantial evidence that P. coronata is progressively displacing native tree ferns by preventing seedling establishment and poses a severe threat to Fiji’s native biodiversity and ecological processes. Therefore, urgent management is required to control and prevent the further spread of P. coronata and its negative impacts on native plant biodiversity. Management should involve an initial feasibility study to determine the effectiveness of various management strategies, followed by targeted control and/or eradication campaigns and long-term monitoring. Ultimately, well implemented legislation to prevent the spread and introduction of P. coronata and other ornamental plants will be crucial to protect native biodiversity in Fiji and elsewhere.

A functional trait‐based approach to assess the impact of an alien palm invasion on plant and soil communities on a South Pacific island

“…Invasion by P. coronata led to a strong and significant decrease of native understory plant diversity (evenness; Shannon index) in the study area. Recently, Dyer et al (2018) within the same area (CIS Forest Reserve) found that an increase in P. coronata cover in the understory was negatively correlated with the abundance of native tree ferns. In their plots, P. coronata comprised up to 70% of the understory and seemed to outcompete native understory plants.…”

“…During the 1970s, P. coronata was introduced as an ornamental plant to the Colo-i-Suva area in Fiji and has since become invasive in mahogany plantations and native lowland rainforest, where mono-dominant stands are easily found (Keppel & Watling 2012;Dyer et al 2019). P. coronata is extensively cultivated throughout the tropics, making it a potential threat to tropical biodiversity (Dyer et al 2018). For this study, we selected Collembola as a model group of soil fauna.…”

“…P. coronata is extensively cultivated throughout the tropics, making it a potential threat to tropical biodiversity (Dyer et al . 2018). For this study, we selected Collembola as a model group of soil fauna.…”

Alien palm invasion leads to selective biotic filtering of resident plant communities towards competitive functional traits

“…There, IAP-induced changes to ecosystems tend to readily manifest, given that the native biota is disharmonic, the functional redundancy is low, and food webs are simple. Recorded impacts on the biodiversity of Pacific island rainforests (e.g., by Dyer et al 2018;Minden et al 2010a) include the replacement of native understory species and the interruption of life cycles of foundation species (Boehmer et al 2013;Keppel et al 2014;Minden et al 2010b;Mueller-Dombois and Boehmer 2013). Another notable impact of IAP is the alteration of habitat (e.g., a change in biogeochemical soil properties and microclimate) and ecosystem functioning (e.g., nutrient cycling and productivity) brought about as a consequence of species replacement and diversity loss (Pyšek et al 2012(Pyšek et al , 2020Vilà et al 2011).…”

Coral islands in West Papua: A model system for functional and taxonomic diversity and the resilience of isolated habitats

“…Global biodiversity is declining at unprecedented rates (Barnosky et al 2011, Ceballos et al 2015. Island species are especially vulnerable to suffer extinction as they are often less competitive than invasive species (Caujapé-Castells et al 2010, Moser et al 2018, Dyer et al 2019, often adapted to unique habitats only present on particular islands (Keppel et al 2014, Heinen et al 2018), and exhibit small population sizes (Hanski 1986, Cody andOverton 1996). Detailed knowledge of ecological adaptations of island communities is essential to develop conservation strategies in order to address species loss (Caujapé-Castells et al 2010).…”