Dynamic Ecological Shifts

 

Dynamic ecological shifts are when a clade switches between different ecologies, for example habitats or diets. Investigation of the impact of these type of shifts on phenotypic and lineage diversity require maps of the evolutionary history of the ecological trait upon the phylogeny of the clade of interest. We can then compare the rates of evolution (phenotypic or net diversification) in lineages with different ecologies.

A morphospace of parrotfishes & wrasses with the phylogeny superimposed to illustrate the dynamic evolution of morphology in these fishes.

Coral reefs are one of the most diverse ecosystems on earth and yet we know little about the evolutionary and ecological mechanisms that generate or maintain such spectacular diversity. Using stochastic character-mapping to sample the history of habitat shifts in labrids we have shown that evolutionary-informed rates of functional morphological evolution are approximately twice as fast in complex coral reef environments. In addition we found that coral reef species occupy more trophic morphospace than non-reef species.


Price, S.A., Holzman, R. A., Near, T.J. & Wainwright, P.W. (2011) Coral reefs promote the evolution of morphological diversity and ecological novelty in labrid fishes. 2011 Ecology Letters 14(5), 462-469 (DOI 10.1111/j.1461-0248.2011.01697.x)


Recently, working with Jose Tavera, a graduate student at the Centro de Investigaciones Biológicas del Noroeste in La Paz México, we have been able to provide independent support for this conclusion by showing that a primarily nocturnal clade of fishes (haemulids) that are very distantly related to labrids also exhibit higher rates of morphological diversification on reefs.


Price, S.A., Tavera, J., Near, T.J. & Wainwright, P.W. (2013) Elevated rates of morphological and functional diversification in reef-dwelling haemulid fishes. Evolution 67 (2), 417-428.


These results suggest that the preservation of coral reefs is necessary, not only to safeguard current biological diversity but also to conserve the underlying mechanisms that can produce functional diversity in the future.

Coral reefs promote the evolution of morphological diversity & ecological novelty

One possible reconstruction of major dietary transitions across mammals using stochastic character mapping implemented in SIMMAP. Herbivores are depicted in green, carnivores in blue and omnivores in purple.

Major transitions in mammalian dietary strategies

I am currently working on a large-scale collaborative project to elucidate the major shifts in dietary strategy and its impact on phylogenetic and phenotypic diversification. Mammals are arguably the best-studied group of organisms on Earth and yet relatively little is known about how mammalian dietary strategies have evolved across the phylogeny.  Studies of dietary evolution have focused on specific dietary categories or individual clades of mammals.  This specificity deprives us of the ability to generalise about common processes of evolution of mammalian diets.  We have collated species-level dietary data from the scientific literature for over 1,500 species of mammal. By synthesising it with an already published time-calibrated phylogeny for all mammals we will be able to describe these important macroevolutionary patterns.


Our first analyses are providing some exciting results: we show within living mammals (~5020 species) that net diversification rate (the cumulative effect of speciation and extinction) differs significantly depending on trophic strategy. Herbivores diversify fastest; carnivores are intermediate and omnivores are slowest. Countering the slow diversification of omnivorous lineages we find that the tempo of transitions between the trophic strategies is highly biased: the highest rates occur into omnivory from herbivory and carnivory.


Price, S.A., Hopkins, S. B., Smith, K. K. & Roth, V. L. (2012) The tempo of trophic evolution and its impact on mammalian diversification. Proceedings of the National Academy of Science 109 (18), 7008-7012.


Our current NSF grant extends this research to combine fossil and extant data to try and look at the mechanisms generating these patterns by estimating speciation and extinction rates and how they have changed over time as well as looking at phenotypic diversification of tooth morphology and body size. The first two years of this grant have been focused on collecting data on: morphology independent fossil diet proxy data, fossil occurrence data, extant dietary data and existing morphological phylogenetic matrices of fossil and extant taxa, for Primates, Carnivora & Cetartiodactyla.


Price, S.A., Hopkins, S. S. B. (2015) The macroevolutionary relationship between diet and body mass across mammals. Biological Journal of the Linnean Society 15(1), 173-184.


Also, working with one of my undergraduate researchers we have uncovered some interesting patterns and relationships between diet and carnassial tooth morphology - so watch this space!


My primary collaborator on these projects is Samantha Hopkins we met while at NESCent - the National Evolutionary Synthesis Center, which has partially funded this project.