Accounting for sampling patterns reverses the relative importance of trade and climate for the global sharing of exotic plants
Product Type:Journal Article
Author(s):Sofaer, H.R. and Catherine S. Jarnevich
Suggested Citation:Sofaer, H.R. and Catherine S. Jarnevich. 2017. Accounting for sampling patterns reverses the relative importance of trade and climate for the global sharing of exotic plants. Global Ecology and Biogeography 2017:1–10. https://doi.org/10.1111/geb.1257710
Exotic species’ distributions reflect patterns of human-mediated dispersal, species’ climatic tolerances, and a suite of other biotic and abiotic factors. The relative importance of each of these factors will shape how the spread of exotic species is affected by ongoing economic globalization and climate change. However, patterns of trade may be correlated with variation in scientific sampling effort globally, potentially confounding studies that do not account for sampling patterns.
Time period: Museum records, generally from 1800s through 2015.
Major taxa studied: Plant species exotic to the U.S.
Methods: We used data from the Global Biodiversity Information Facility (GBIF) to summarize the number of plant species with exotic occurrences in the U.S. that also occur in each other country worldwide. We assessed the relative importance of trade and climatic similarity for explaining variation in the number of shared species while evaluating several methods to account for variation in sampling effort among countries.
Results: Accounting for variation in sampling effort reversed the relative importance of trade and climate for explaining numbers of shared species. Trade was strongly correlated with numbers of shared U.S. exotic plants between the U.S. and other countries before, but not after, accounting for sampling variation among countries. Conversely, accounting for sampling effort strengthened the relationship between climatic similarity and species sharing. Using the number of records as a measure of sampling effort provided a straightforward approach for analyzing occurrence data, whereas species richness estimators and rarefaction were less effective at removing sampling bias.
Main conclusions: Our work provides support for broad-scale climatic limitation on exotic species distributions, illustrates the need to account for variation in sampling effort in large biodiversity databases, and highlights the difficulty in inferring causal links between the economic drivers of invasion and global exotic species occurrence patterns.