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Absolutely delighted to share that my first paper, with @Alex_Pigot, @TimBlackburn66 and @Ellie_E_Dyer, is out today in @NatureEcoEvo!
Environmental resistance predicts the spread of alien species https://www.nature.com/articles/s41559-020-01376-x (1/13)
Environmental resistance predicts the spread of alien species https://www.nature.com/articles/s41559-020-01376-x (1/13)
This work stemmed from my MSci research project @UCLCBER @UCLBiosciences and I am so pleased to finally share it. Here’s what we did… (2/13)
Predicting the spread of alien species is challenging, with species distribution models (SDMs) producing mixed results. (3/13)
In 1982, Eduardo Rapoport (well known for Rapoport’s rule) proposed an alternative approach: that the spread of alien species could be predicted based on patterns of distance decay in native species assemblages (4/13)
I.e. an alien species is less likely to spread to areas with a lower biotic similarity to the site where it established. These sites would have a high ‘environmental resistance’. After all, if conditions stop native species spreading between areas, they may also stop aliens(5/13)
To our knowledge Rapoport’s environmental resistance (ER) model has never been applied and so we set out to test if patterns of ER could predict alien range spread, using the distribution of 283 alien bird species as a case study (6/13)
We used a spreading dye model to simulate alien range expansion from known sites of population establishment. We assumed that alien species tended to spread into areas with low ER, calculated based on maps of distance decay using the distributions of all native birds (7/13)
Our results show that across species, ER predicts current alien ranges with an accuracy of 78%. Using ER was better than a null model assuming random dispersal and also models where patterns of spread are determined directly by climate (8/13)
In regions where ER is low (slow distance decay) aliens have spread further than in regions where ER is high (rapid distance decay). While no single ER threshold can explain alien range size well, very few alien species have spread beyond ER = 0.5 (9/13)
ER=0.5 is a 50% decline in biotic similarity from the site of establishment, a kind of ‘community half-life’. We suggest that this can define a ‘safe-limit’ beyond which spread is unlikely. We use this to identify areas at risk of future invasion from current alien birds (10/13)
While our paper raises more questions than it answers, the ability of ER to predict where species are likely to spread is exciting because it may allow prediction of invasion risk when information on the niche, or even identity, of a potential invader is lacking (11/13)
If we know where alien species are establishing, ER can help us predict which areas may then be most at risk from spread. We hope that the environmental resistance model could therefore complement existing approaches (e.g. SDMs) for predicting invasion risk (12/13)
