Untangling the phylogenetic and spatial components of trait variation in ecological assemblages
Lead Research Organisation:
University of Sheffield
Department Name: School of Biosciences
Abstract
Traits are the set of evolved characteristics that permit a species to exploit its niche and live in a given environment. Explaining how and why traits vary among species is a basic problem in ecology and evolutionary biology. Fundamental to achieving this is the task of disentangling how evolutionary, environmental and ecological factors drive trait variation.
Trait evolution is driven by the interplay of biotic and abiotic factors, whilst constrained by previous history, and plays out at all scales. In ecological terms, the composition and structure of communities is determined by the ecological and functional diversity of species present in a community, which is dependent on the traits of those species. Thus, evolutionary and ecological scales of organisation within a community are linked through species traits.
To understand the variation in traits of species within a community, accounting for species' distributions and the degree to which species' ranges overlap is important. Within the communities in a geographic region, the similarities and differences between species' traits will be shaped by factors such as the extent to which species' ranges overlap, as well as the similarity of niches and habitat use within areas of range overlap compared with outside. Given this observation, the first main objective of this project is to develop comparative models that account for species' co-distributions in driving trait variation.
When exploring the ecological drivers of trait variation, an obvious consideration is the extent to which species co-occur ecologically. For example, two species may have similar habitat requirements, with the consequence that they tend to occur together in the same communities. In this case, it might be expected that when species' ranges overlap they occur in the same communities. Consequently, species that occur in the same communities may be expected to share common suites of adaptations, and traits would co-vary positively. Alternatively, as a consequence of ecological interactions (e.g. competition), negative effects on trait covariance would also be possible: if species that co-occur only possess divergent traits, then covariance will be reduced. The second main objective of this project is to develop comparative models that link phylogeny with both large-scale distributions and local-scale patterns of occurrence within their ranges.
We will use the methods we develop to test two hypotheses:
Hypothesis 1: species with overlapping geographic distributions show greater similarity than those with non-overlapping ones.
Hypothesis 2: species that co-occur within the same ecological communities show greater divergence, for given levels of range overlap, than those that do not.
The strategy for developing methods will be as follows. First, we will create a model that simulates data according to well-defined processes. Second, a statistical framework will be developed that allows the model to be fitted to data and tested against the simulation outputs. Finally, we will apply our models to real datasets, testing our two main hypotheses using each dataset.
To apply the methods, we require datasets that contain the following: (i) traits of species co-occurring in a series of ecological communities; (ii) a phylogeny, resolved as well as possible; (iii) maps of species' geo-graphic ranges; and, in addition, to apply the methods developed in Objective 2: (iv) ecological measures of species' occurrences. We will apply the models to two existing datasets that include these elements--one on Brazilian Atlantic forest trees, the other on Colombian birds--to generate new insights into the factors that drive community composition, in each case testing the two major hypotheses of the project.
Trait evolution is driven by the interplay of biotic and abiotic factors, whilst constrained by previous history, and plays out at all scales. In ecological terms, the composition and structure of communities is determined by the ecological and functional diversity of species present in a community, which is dependent on the traits of those species. Thus, evolutionary and ecological scales of organisation within a community are linked through species traits.
To understand the variation in traits of species within a community, accounting for species' distributions and the degree to which species' ranges overlap is important. Within the communities in a geographic region, the similarities and differences between species' traits will be shaped by factors such as the extent to which species' ranges overlap, as well as the similarity of niches and habitat use within areas of range overlap compared with outside. Given this observation, the first main objective of this project is to develop comparative models that account for species' co-distributions in driving trait variation.
When exploring the ecological drivers of trait variation, an obvious consideration is the extent to which species co-occur ecologically. For example, two species may have similar habitat requirements, with the consequence that they tend to occur together in the same communities. In this case, it might be expected that when species' ranges overlap they occur in the same communities. Consequently, species that occur in the same communities may be expected to share common suites of adaptations, and traits would co-vary positively. Alternatively, as a consequence of ecological interactions (e.g. competition), negative effects on trait covariance would also be possible: if species that co-occur only possess divergent traits, then covariance will be reduced. The second main objective of this project is to develop comparative models that link phylogeny with both large-scale distributions and local-scale patterns of occurrence within their ranges.
We will use the methods we develop to test two hypotheses:
Hypothesis 1: species with overlapping geographic distributions show greater similarity than those with non-overlapping ones.
Hypothesis 2: species that co-occur within the same ecological communities show greater divergence, for given levels of range overlap, than those that do not.
The strategy for developing methods will be as follows. First, we will create a model that simulates data according to well-defined processes. Second, a statistical framework will be developed that allows the model to be fitted to data and tested against the simulation outputs. Finally, we will apply our models to real datasets, testing our two main hypotheses using each dataset.
To apply the methods, we require datasets that contain the following: (i) traits of species co-occurring in a series of ecological communities; (ii) a phylogeny, resolved as well as possible; (iii) maps of species' geo-graphic ranges; and, in addition, to apply the methods developed in Objective 2: (iv) ecological measures of species' occurrences. We will apply the models to two existing datasets that include these elements--one on Brazilian Atlantic forest trees, the other on Colombian birds--to generate new insights into the factors that drive community composition, in each case testing the two major hypotheses of the project.