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Evolution in island birds and the ‘insularity’ syndrome

In spite of the importance of islands as centres of endemism and important ‘laboratories’ for the study of ecology and evolution, some aspects of island ecology and evolution remain poorly understood. This programme studies patterns of adaptation on islands worldwide as well as conducting detailed studies using Tristan da Cunha and the Gulf of Guinea islands as study systems. Previous research has explored global patterns in life-history and behaviour of island species and, over the last year, we have shown how the low diversity of island communities influences the evolution of bird song.

Although the level of endemism on islands is generally high, individual island communities hold fewer species than their mainland counterparts. This has many ecological, behavioural and evolutionary consequences. PhD student Alois Robert (U. Montpellier, France) has been investigating how these processes affect communication, focusing on acoustic traits. The lower species diversity on islands also extends to parasites. Previous work conducted by our group revealed decreased diversity and prevalence of Haemosporidia parasites in the Gulf of Guinea islands. This decrease in parasite pressure may favour the evolution of a weaker immune systems, a contention that is currently debated. A new collaboration has now enabled us to test this hypothesis.

Activities in 2018

  • PhD student Alois Robert, working with Claire Doutrelant, Martim Melo and Thierry Lengagne (CNRS, France) revealed new patterns of acoustic communication in island bird communities. Comparing the soundscapes on islands in the Gulf of Guinea and Madeira with adjacent mainland communities (Cameroon and southern France, respectively), he found that mainland communities were louder and occupied a larger frequency range, especially in Cameroon, revealing a decreased availability of acoustic space for tropical mainland birds. In diverse communities, singing species exhibit a higher acoustic turnover and overlap less in time and frequency with each other than in more depauperate communities. This leads to greater acoustic niche partitioning on mainlands than islands, which suggests that competition for acoustic space plays a role in song evolution. This conclusion is further supported by the broader frequency bandwidths of island species compared to their mainland counterparts.
  • We established a collaboration with Benoit Nabholz (U. Montpellier, France) and Claire Loiseau (CIBIO) to obtain funding to investigate the effects of insularity on the immune system using toll-like receptors. Lab work has started on samples collected in previous years.
  • After considerable effort, Martim Melo and his team finally caught an individual of the recently discovered scops owl on Princípe Island by recording its call and using play- back to attract this elusive species. Genetic analyses confirmed it is a new species, distinct from the São Tomé Scops Owl Otus hartlaubi. Additional fieldwork by Martim and MSc student Barbara Freitas has determined the distribution of the newly-discovered scops-owl on Princípe Island, estimated its population size, and obtained information on its ecology.
  • A project by MSc student Louis Bliard, working with Claire Doutrelant, Matthieu Paquet and Rita Covas, suggests that predator pressure influences the evolution of bird colouration on islands. These results have now been submitted for publication.
  • In the project on Nesospiza finches on the Tristan da Cunha islands, effort continued to be made to understand the speciation scenario and the genomics underpinnings of the adaptive phenotypic variation in bill and body size. In addition to the previously produced reference genome assembly, whole genomes of several individuals each of the four taxa, N. a. acunhae, N. a. dunnei (Inaccessible Island), N. questi, and N. wilkinsi (Nightingale Island), were resequenced by Martin Stervander and Bengt Hansson using the Illumina HiSeq X10 platform.

Highlights

  • Genetic work confirmed that the specimen of scops owl captured on Princípe Island is a new species, highly differentiated from species on São Tomé and the mainland.
  • A paper on the origin of the Inaccessible Island Flightless Rail Atlantisia rogersi published in Molecular Phylogenetics and Evolution led by Martin Stervander attracted massive media attention, and obtained the highest Altmetric score for a paper in this journal.
  • Alois Robert presented his work on the influence of community structure on acoustic signals at the IBAC conference in India and the Bioacoustics conference in Cape Town. The differences he has found in acoustic communication between island and mainland birds are the subject of two papers that were submitted for publication.
  • Martin Stervander gave an invited presentation at the 2018 American Genetics Association meeting , the theme of which was the Origins of Adaptive Radiations. His presentation included data from Nesospiza buntings.
  • A new grant was obtained to study immunity among island birds.

Impact of the project

This project is uncovering novel patterns of adaptation in island birds and investigating the mechanisms underlying these adaptations. The results make a significant contribution to our understanding of the ecology and evolution of island environments. Given the high number of species endemic to islands worldwide and the threats to these faunas, our work will help to understand and conserve island species

Key supporters

Forever Principe; National Geographic; CNRS (PEPS); University of Montpellier (PhD grant to Alois Robert); LIA Biodiversity.

Research team

Dr Rita Covas (FIAO and CIBIO, U. Porto)
Dr Martim Melo (FIAO and CIBIO, U.Porto)
Dr Claire Doutrelant (CNRS and FIAO)
Dr Claire Loiseau (CIBIO, U. Porto)
Dr Martin Stervander (U. Oregon)
Prof. Bengt Hansson (U. Lund, Sweden)
Dr Peter Ryan (FIAO, UCT)

Student: Aloïs Robert (PhD, CNRS and U. Montpellier); Sandra Reis (PhD, CIBIO, U.Porto); Barbara Freitas (MSc, CIBIO, U. Porto); Louis Bliard (MSc, CNRS and U. Montpellier).