Biotic interactions and the generation and organisation of biodiversity
Lead Research Organisation:
University of Bristol
Department Name: Biological Sciences
Abstract
One of the biggest challenges facing biologists is to predict, and perhaps prevent, the loss of biodiversity. For some groups, such as birds and mammals, we know where species live and can identify biodiversity hotspots - areas of the world with unusually high numbers of species. But knowing where species live is not enough: to determine how biodiversity will be affected by global change we need to understand the evolutionary processes that generate it. Yet, species do not evolve in isolation: they evolve together in the context of communities or ecosystems. Consider two species that need the same limited resource. Can the two species co-exist? One might think not - they are in competition with one another and for one species to succeed then it must do so at the expense of the other. This may often be true, but an alternative is for one or both species to use the resource in different ways, or even to use a different resource altogether. The finches of the Galapagos Islands, made famous by Charles Darwin, reveal both of these outcomes of competition: where two species, the medium ground finch and the small ground finch, occur together on the same island they can be easily distinguished by differences in beak size, but on some islands one species is much reduced in number or even absent altogether and in such cases the two species typically have similar, intermediate, beak sizes. So the interactions between species in communities are important as drivers of evolutionary change and in determining which species live where. The aim of my research is to understand how interactions that act over generations within communities can influence the evolution of biodiversity over thousands to millions of years. Does competition cause evolution to speed up? Can changes in diversity through time in the fossil record be attributed to competition? My solution to understanding these problems is to build computer models that mimic competitive interactions and generate predictions of evolutionary change among competing species. This is an exciting approach because by mimicking a range of evolutionary scenarios we can generate predictions of how species change over long time-scales and how these changes alter biodiversity. More importantly, we can compare our predictions with real data from living and fossil species to test how different ecological processes determine how species and their traits diversify and which species live together. This is a major challenge as ecological communities contain multiple species and each species occurs in multiple communities. Not only that but the importance of species interactions is influenced by other factors. If there is ecological opportunity such as the chance to occupy a new habitat, then the pressures driving evolution will change. Ecological opportunity could arise due to environmental change, the evolution of a key innovation or a host of other factors. For example, a group of Caribbean lizards called anoles have diversified rapidly to occupy trees, partly due to the evolution of a unique toe-pad. This type of ecological opportunity may even lead to the formation of new species as different populations of the same parent species diverge from one another, as is the case for anoles. To prise apart the role of ecological opportunity and competition in generating biodiversity I explore variation and evolution in the morphology, ecology and behaviour in different groups of organisms. Hummingbirds are one such group. There are 330 hummingbird species that feed primarily on nectar, occupy diverse habitats across their geographic range, and display several feeding behaviours. In short, they provide an exceptional group to test the relative importance of competition and ecological opportunity in driving large-scale evolution change. By combining this real-world data with predictive models, I will provide new insight into how past and present-day biological diversity is generated and maintained.
Organisations
Publications
CASSEY P
(2012)
Why are birds' eggs colourful? Eggshell pigments co-vary with life-history and nesting ecology among British breeding non-passerine birds WHY ARE BIRDS' EGGS COLOURFUL?
in Biological Journal of the Linnean Society
Clarke M
(2017)
Trait Evolution in Adaptive Radiations: Modeling and Measuring Interspecific Competition on Phylogenies.
in The American naturalist
Cooper N
(2016)
A cautionary note on the use of Ornstein Uhlenbeck models in macroevolutionary studies.
in Biological journal of the Linnean Society. Linnean Society of London
Ezard T
(2013)
Inclusion of a near-complete fossil record reveals speciation-related molecular evolution
in Methods in Ecology and Evolution
Jenkins T
(2012)
Migratory behavior of birds affects their coevolutionary relationship with blood parasites.
in Evolution; international journal of organic evolution
Jetz W
(2014)
Global distribution and conservation of evolutionary distinctness in birds.
in Current biology : CB
Jetz W
(2012)
The global diversity of birds in space and time
in Nature
Kuhn T
(2011)
A simple polytomy resolver for dated phylogenies
in Methods in Ecology and Evolution
Description | A major aim of my research is to understand how competitive interactions among closely related species that act over generations within communities can influence the evolution of biodiversity over thousands to millions of years. We can potentially detect past evolutionary processes by examing patterns in the physical traits of species and the relationships among species. A major component of this research uses the evolutionary histories of species to infer how diversity has arisen. With an international team including researchers from universities in the US, Canada, and Australia, I have built the world's first family tree (called a phylogeny) linking all known species of living birds that has allowed me to show when and where birds evolved and diversified. The family tree was used to map out where the almost 10,000 species of birds live to show where the most diversification has taken place in the world. Diversification is the net outcome of new species arising, called speciation, and existing species going extinct. We combined this data with existing data on the geographic ranges of all living bird species so that we could map diversification across the world. Our results revealed that the formation of new species has sped-up over the last 50 million years. This result was unexpected. Often, in smaller groups of closely related species, including many groups of bird species, the rate at which new species arise slows down from the past towards the present. This is because unused ecological niches (habitat, diet) can become more scarce as new species arise until eventually there are no niches left to fill. This 'phylogeny' is important because it is the first that includes all living birds. It means we can ask questions about biodiversity and evolution on a global scale and gain new insight into how diversity has changed over millions of years as well as understand the possible causes of those changes. For example, we found that despite harbouring more species in total, species formation is slower in the tropics than at higher latitudes. Surprisingly we found higher rates of speciation in the Western Hemisphere compared to the Eastern Hemisphere. |
Exploitation Route | One way in which the bird phylogeny can be used is in helping to prioritise conservation efforts. We can identify where species at greatest risk of extinction are on the tree and ask how much distinct evolutionary history they represent. Some species have many close relatives and represent a small amount of distinct evolutionary history whereas others have few close relatives and their loss would represent the disappearance of vast amounts of evolutionary history that could never be recovered.This is one of major themes of ongoing research on the bird family tree with links to the EDGE of Existence conservation programme run by the Zoological Society of London (http://www.edgeofexistence.org/). The bird phylogeny has been made available as an open access database at http://birdtree.org/. |
Sectors | Other |
URL | http://birdtree.org/ |
Description | Outputs of one paper on the global conservation of birds has been used by the Zoological Society of London to support fundraising as part of their EDGE program (http://www.edgeofexistence.org) |
First Year Of Impact | 2014 |
Sector | Environment |
Impact Types | Societal |
Description | ERC Consolidator Grant |
Amount | € 1,700,000 (EUR) |
Organisation | European Research Council (ERC) |
Sector | Public |
Country | Belgium |
Start | 05/2014 |
End | 04/2019 |
Title | birdtree.org |
Description | Website supporting open access to phylogenies of the world's birds. |
Type Of Material | Database/Collection of data |
Year Produced | 2012 |
Provided To Others? | Yes |
Impact | Resource has been cited ~200 times (Google Scholar). |
URL | http://birdtree.org |
Title | MOTMOT |
Description | Free software in the R language for studying the evolution of traits among species using phylogenetic trees. |
Type Of Technology | Software |
Year Produced | 2012 |
Open Source License? | Yes |
Impact | Used in numerous published papers (cited 31 times to date according to Google Scholar). |
URL | https://github.com/ghthomas/motmot |