Biological invasions pose a continuing threat to the conservation of the unique biodiversity and ecosystems of the Caribbean Overseas Territories (OTs), which are islands and archipelagos [1]. These islands are linked to each other, to other islands and to continents via air and sea transport networks. Transport links are the source of current and future introductions of invasive species [2], and need to be quantified and understood, so that we can better predict invasion risk and preventing introductions of high-risk species in the future [3]. This PhD project aims to quantify the risk of biological invasions to the Caribbean OTs from the pools of species represented across the trade and transport network of the islands. The project provides a unique opportunity to combine network and distribution modelling, overseas fieldwork and experimental approaches that will yield results directly applicable to Caribbean OT biosecurity measures.
Methodology
The project has four main objectives:
1) Build an invasion risk network for the Caribbean OTs, identify the most high-risk sources and pathways of invasive species. To achieve this objective, the PhD student will first create a dataset describing the transport links centred on the OTs and their magnitude, from open access sources and from the OT authorities themselves. This dataset will then be used to create a risk map, identifying the links and source regions posing the highest risk of species arrival, and then establishment (based on climate suitability) and invasion (based on known native and introduced ranges of high-impact invasive species globally) [4]. The predictions from this risk map will also be compared to known established and invasive non-native species on the OTs for validation (as in [2]), and to data collected on OT biosecurity capacity.
2) Collect interceptions data for at least two selected Caribbean OTs, to establish which types of INNS and which origins and pathways of introduction pose the highest biological invasion risk. This objective will involve visiting the OTs and working with local biosecurity authorities to identify and catalogue organisms that arrive at major ports of entry. These data will then form the basis of an interceptions database for the OTs which we will use to model risk based on trade, trait and interceptions data [5; 6]. We will also validate recently constructed lists of species considered to pose a high risk of imminent invasion to the OTs [3], and quantitative risk scores based on the CABI Horizon Scanning Tool.
3) Assess the ability of species distribution modelling methods to predict climatic suitability of invasive species in the Caribbean OTs. The islands and archipelagos are small in area, and this may limit reliable prediction of climate suitability for introduced species [7]. The student will assess the scale of this limitation by applying species distribution models to species already present and established on the OTs, providing an opportunity to validate and optimise methods to be applied to species not yet introduced. The student will also explore the role of other data layers in explaining the distribution of non-native species.
4) Experimentally assess the survivorship and performance of species intercepted and already present in the selected OTs. This objective will focus on plants that are i) intercepted as seed contaminants, in imported goods, transport and on people/luggage and ii) already introduced but not invasive in the exemplar OTs. Attempts to germinate and grow these seeds of these species will be carried out in climatic and light conditions simulating those found in the OTs, using climate growth chambers at Durham. For species that successful germinate and grow, their competitive ability versus candidate native plants will also be assessed under current and near-future climates, as a measure of potential impact on native vegetation.
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