Analyzing Community Phylogenetic Structure with R
Explore the central question in community ecology of what processes are responsible for the identity and relative abundances of co-occurring species in local assemblages. Learn about community assembly processes, including niche and trait evolution, and patterns of phylogenetic community structure using phylogenetic data. Discover how to search for patterns in community structure that may reflect underlying processes through the use of R.
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PowerPoint presentation about 'Analyzing Community Phylogenetic Structure with R'. This presentation describes the topic on Explore the central question in community ecology of what processes are responsible for the identity and relative abundances of co-occurring species in local assemblages. Learn about community assembly processes, including niche and trait evolution, and patterns of phylogenetic community structure using phylogenetic data. Discover how to search for patterns in community structure that may reflect underlying processes through the use of R.. The key topics included in this slideshow are community ecology, phylogenetic structure, R, community assembly processes, niche and trait evolution,. Download this presentation absolutely free.
1. Community Phylogenetic structure with R
2. Central question in community ecology What processes are responsible for the identity and relative abundances of co-occurring species in local assemblages? What is the relative importance of different ecological processes in structuring communities Search for patterns in community structure that may reflect underlying processes
3. Community assembly processes Niche and trait evolution Patterns of phylogenetic community structure Phylogenetic data
4. Patterns of phylogenetic community structure Phylogenetic clustering Co-occurring species are more closely related than expected by chance Phylogenetic over- dispersion/evenness Co-occurring species are more distantly related than expected by chance Random patterns
5. Community assembly processes Many processes could influence phylogenetic community structure Facilitation Negative density dependent processes (e.g. herbivory, predation) Indirect interactions mediated by herbivores, parasites, pathogens Disturbance e.g. fire Speciation Two main processes are usually considered
6. Habitat filtering Adaptation of species to abiotic conditions Communities composed of ecologically similar species Environment imposes a filter via abiotic conditions favoring species with similar adaptations Emerson & Gillepsie, 2008
7. Competitive exclusion The principle of competitive exclusion: similar species cannot coexist indefinitely. Related species are ecologically similar Prediction: closely related species should co-occur less than would be expected Early efforts tested this hypothesis using species : genus ratios Taxonomic community structure Emerson & Gillepsie, 2008
8. Phylogenetic signal Kembel, 2009
9. Community phylogenetic structure (Competitive exclusion) (or clustering) Kembel, 2009
10. Clustering due to environmental filtering Trait conservatism Over-dispersion due to competitive exclusion Trait conservatism Clustering due to competitive exclusion Trait convergence Over-dispersion due to environmental filtering Trait convergence h Clustering: Co-occurring species are more closely related than expected by chance Over-dispersion: Co-occurring species are more distantly related than expected
11. Emerging patterns Communities structured by several processes acting in concert Mediated by different sets of traits Scale is important Taxonomic scale (Cavender-Barres et al., 2004; 2006) Oaks: phylogenetic over dispersion Angiosperms: phylogenetic clustering Spatial scales Similar shift from smaller (overdispersion) to larger spatial scales (clustering)
12. Steps Quantify the degree of relatedness among co- occurring species using a phylogeny Define a broader pool of species from which communities have been assembled Construct a null model which generates random communities from the broader species pool Determine phylogenetic signal for functional traits that influence community assembly
13. Data Phylogenetic tree for regional/broader species pool Entire species in all the communities Species list and presence/absence or abundance data for the different communities, plots or specific habitats within a community.
14. Getting a phylogenetic tree Can use either sequence data or species list Different formats: Newick, Nexus Online tools available e.g. Genbank ( http://www.ncbi.nlm.nih.gov/ ): can obtain raw sequence data ARB/Silva ( http://www.arb-silva.de/ ): provides aligned sequence data free for academic use RDP ( http://rdp.cme.msu.edu/ ): provides sequence data and builds phylogenetic tree Beast ( http://beast.bio.ed.ac.uk/Main_Page ): contains programs to create phylogenies with sequence data Phylomatic ( http://www.phylodiversity.net/phylomatic/ ): assembles phylogenies using species lists.
15. Quantifying degree of relatedness Vamosi et al. , 2009
16. Within community measures Faiths phylogenetic diversity (PD) Total branch length spanned by the tree including all species in a local community. A lower value indicates that Taxa are clumped on the phylogeny Capture only a small part of the total phylogenetic diversity present in the entire phylogeny Co-ocurring species are more closely related
17. MPD: Mean pair-wise distance between all species in a community Measures whether species in a community are more closely related than expected by chance (using a null model and the regional species pool) MPD is more sensitive to tree-wide phylogenetic patterns MNTD: Mean distance to nearest taxon for each species in the community Measures whether closely related species tend to co-occur or not (using a null model and the regional species pool). MNTD is more sensitive to patterns of evenness and clustering closer to the tips of the phylogeny
18. Distance matrix Kembel, 2009
19. Null models Randomize the phylogeny Phylogeny shuffle: randomizes phylogenetic relationships among species by shuffling the taxa on the tips. Randomize tree structure Randomize community structure Randomize draws from species pool Species in each sample are random draws from the Sample pool: maintains species richness of each sample but species are drawn without replacement from the list of all species actually occurring in the sample. Regional species pool: maintains species richness, but species are drawn without replacement from a broader phylogeny pool. Randomize community matrix Independent swap: creates swapped versions of the sample/species matrix; only applicable with presence/absence data.
20. Randomization Using null model Generate a random community Recalculate metrics i.e. MPD/MNTD Repeat many times Result: distribution of metric values for random communities
21. Standardized effect sizes (SES) SES=(Observed value Mean (random values))/SD(random values) Net relatedness index (NRI): standardized metric obtained by comparing MPD obs and MPD exp + NRI = phylogenetic clustering - NRI = phylogenetic evenness Calculated as standardized effect size (SES) in picante SES = -1 x NRI
22. SES continued Nearest taxon index (NTI): obtained by comparing MNTD obs and MNTD exp + NTI = phylogenetic clustering - NTI = phylogenetic evenness Computed as standardized effect size (SES) in picante SES = -1 x NTI
23. Phylogenetic Beta Diversity Measures patterns of phylogenetic relatedness among communities Among communities equivalent of MPD and MNTD using pairs of species drawn from different communities can be used with any method based on among-community distances e.g. cluster analysis, phyloordination, Mantel tests with spatial/environmental distances separating communities.
24. Todays Data Bird communities along 3 highways: 64, 44, and 55 Gradient from urban (1) to rural (5) along those highways, with each community separated by 16 km Ex. Communities: RD441, RD442, RD443, RD641, RD642, etc RD64 1 2 3 4 5 ???
25. Genetic data from Genbank using 2 mitochondrial genes Cytochrome b (Cytb) and Cytochrome c oxidase subunit I (COI) Made a phylogeny using Beast and Beauti (free online, easy to use, and comes with a short tutorial and good manual) Question : What is the phylogenetic structure of communities as you go from rural to urban environments? RD64 1 2 3 4 5 ???