This is the finding of a new model developed by researchers from the University of Leeds and Imperial College London. The model could apply both to actual islands and isolated areas of habitat on the mainland that are home to unique species, such as the table top mountains of South America.
The natural history of islands is littered with examples of unusual species found only in one place, such as the Hawaiian Goose, Galapagos Tortoises and Dodo that may once have been common on their islands, but since human contact have become rare or even extinct. Now this new modelling approach shows that in general, most unique island species should be common on their island. If they are not, then the researchers believe human activity is most likely to be the cause.
"Models of island ecology have tended to focus on the total number of different species that you might expect to find on an island, rather than on how common or rare those species are and whether or not they are unique to the island," says Dr James Rosindell, of Leeds' Faculty of Biological Sciences. "Our model is able to predict the way that new species develop in isolation from the mainland as well as how many individuals of each species we could expect to see in their natural habitat. However, there is little data on population sizes and this highlights a real gap in knowledge that we need to fill."
To develop the model, the researchers collated data on bird species found across 35 islands and archipelagos. Modern genetics makes it possible to identify which species have diverged to create new species - so the team were able to test their model against actual data.
The model and data both show that whilst islands close to the mainland have no unique species, more distant islands tend to have unique species that are closely related to mainland species. Only the islands and archipelagos furthest from the mainland are expected to contain large numbers of unique species closely related to each other, such as Darwin's finches on the Galapagos and the Hawaiian honeycreepers.
"This model is still in its early stages of development, but we hope it will help to prompt more study of population sizes on islands," says Dr Albert Phillimore, from Imperial's Department of Life Sciences. "Comparing the predictions of different models to actual data can help us to identify where other factors are coming into play - such as additional ecological processes and human intervention. In the future, we plan to look at how the model could also help make predictions relevant to conservation strategy."
The work has been funded through an EPSRC research fellowship and an Imperial Junior Research Fellowship.
Helen Miller, Innovate UK (Apr 2018), £999,960
Elisabetta Groppelli, David Rowlands & Stanley Lemon (University of North Carolina), Medical Research Foundation Fellowship (Apr 2018), £293,494
Nikesh Patel, Medical Research Foundation fellowship (Apr 2018), £290,976
Jessica Kwok & Ralf Richter, Leverhulme Trust (Apr 2018), £298,273
Julie Aspden, Royal Society (Apr 2018), £20,000
Liz Duncan, Royal Society (Mar 2018), £14,602
Alex O'Neill & Ryan Seipke, BBSRC (Feb 2018), £45,489
Jim Deuchars, Royal Society (Feb 2018), £16,300
Stefan Kepinski & Netta Cohen, Leverhulme Trust (Feb 2018), £320,387
Lisa Collins, BBSRC (Feb 2018), £49,950
Lars Jeuken, BBSRC (Feb 2018), £30,000
Nikita Gamper, BBSRC (Feb 2018), £30,000
Alison Baker, BBSRC (Feb 2018), £30,000
Scott Bowen, Leducq Foundation Grant (Feb 2018), £28,470
Jessica Kwok and Ronaldo Ichiyama, International Spinal Research Trust (Feb 2018), £94,450
Alex O'Neill, Oxford Drug Design (Jan 2018), £86,098
Dave Lewis and Colleagues in South Africa, HEFCE Global Challenge Research (Jan 2018), £48,000
Sarah Calaghan, Ed White, John Colyer, Isuru Jayasinghe, BHF (Jan 2018), £128,308
Christine Foyer and Alison Baker, HEFCE GCRF Grant (Jan 2018), £71,158
Alison Baker, Yun Yung Gong and Lindsay Stringer and ICRISAT India, HEFCE GCRF Grant (Jan 2018), £27,000
Graham Askew, Simon Walker, BBSRC (Jan 2018), £699,781
Jennifer Tomlinson, Royal Society (Jan 2018), £512,801
Alison Dunn, NERC (Dec 2017), £18,000
Jennifer Tomlinson, Royal Society-Research Fellows Enhancement Award (Dec 2017), £94,681
Helen Miller, AB AGri Grant (Dec 2017), £73,600
Simon Walker, Royal Society Enhancement Award (Dec 2017), £10,000
Carrie Ferguson, Bryan Taylor, Harry Rossiter, The Physiological Society (Dec 2017), £7,392
Ralf Richter, Royal Society (Dec 2017), £6,000
Christine Foyer, British Council Newton Fund (Dec 2017), £49,840
Adrian Whitehouse and colleagues in School of Chemistry and University of Liverpool, MRC (Nov 2017), £622,319
Michelle Peckham, Neil Ransom, MRC (Nov 2017), £495,159
Dave Lewis, British Council India (Nov 2017), £22,540
Elton Zeqiraj, Royal Society (Nov 2017), £15,000
Hannah Dugdale, Royal Society (Nov 2017), £15,000
Shaunna Burke, Cancer Research UK Innovation Grant (Nov 2017), £20,000
Alex O'Neill and colleagues in Chemistry, BBSRC (Nov 2017), £431,865
Jessica Kwok, Wings for Life (Nov 2017), £87,365
Tom Bennett, BBSRC (Oct 2017), £523,679
Neil Ranson, Darren Tomlinson, BBSRC (Oct 2017), £494,318
Nikita Gamper, BBSRC (Oct 2017), £490,426
Amanda Bretman and colleagues from UEA, NERC (Oct 2017), £430,886
Juan Fontana, Rosetrees Trust consumables grant (Oct 2017), £22,500
Helen Miller, DSM Nutritional Products AG (Sep 2017), £69,988
Neil Ranson, Juan Fontana, Mark Harris, Michelle Peckham, Ralf Richter, Peter Stockley, Patricija Van Oosten-Hawle and colleagues in Engineering, FMH and MAPS, Wellcome Trust Equipment Call (Sep 2017), £418,000
Jamie Johnston, Physiological Society (Sep 2017), £10,000
Frank Sobott, Adrian Goldman, Mark Harris, Andrew Macdonald, Stephen Muench, Sheena Radford and colleagues in FMH and MAPS, Wellcome Trust Equipment Call (Aug 2017), £415,000
Ralf Richter, David Brockwell, Eric Hewitt, Jessica Kwok, Emanuele Paci and MAPS/FMH, BBSRC (Jun 2017), £600,000
Eric Blair, Adrian Whitehouse, Nicola Stonehouse, Alison Baker, Richard Bayliss, Joan Boyes, Ryan Seipke, Sally Boxall and MAPS/FMH, BBSRC (Jun 2017), £376,000
Stefan Kepinski, Yoselin Benitez-Alfonso, Tom Bennett, Michelle Peckham, BBSRC (Jun 2017), £331,000
Roman Tuma, Lars Jeuken, Paul Millner, Sheena Radford, Peter Stockley and MAPS/FMH, BBSRC (Jun 2017), £222,000
Vas Ponnambalam, Darren Tomlinson, Stephen Wheatcroft, BHF (May 2017), £107,878