Department of Ecology, Evolution, and Behavior, University of Minnesota
The integration of community ecology and phylogenetic biology: finding answers to some of life’s persistent questions
Community ecology investigates the nature of organismal interactions, their origins, and their ecological and evolutionary consequences. In the face of habitat destruction world wide, understanding how communities assemble and the forces that influence their dynamics, diversity and ecosystem function will prove critical to managing and restoring the Earth’s biota. Consequently, the study of communities is of paramount importance in the 21st century. The increasing availability of phylogenetic data, computing power and informatics tools has facilitated a rapid expansion of studies that apply phylogenetic data and methods to community ecology. These studies have helped to reveal the multitude of processes driving community assembly, particularly evolutionary processes. As a result this emerging area contributes to the resolution of long-standing controversies in community ecology, challenges previous assumptions, and opens new areas of investigation. Of particular significance is the promise that studies of phylogenetic community structure and composition hold for predicting ecosystem processes and impacts of global change.
Rose L. Carlson
Postdoctoral Research Fellow
Department of Organismic and Evolutionary Biology and Museum of Comparative Zoology, Harvard University
The ecological diversification of darter fishes (Percidae: Etheostomatinae)
To identify the mechanisms responsible for the unequal ecological diversification of closely related clades, I combine ecological data with phylogenetic hypotheses. Here, I will discuss two projects that illustrate the breadth of my work on the diversification of the North American freshwater fishes known as darters. First, I investigated the relationship between the rate of change in ecologically relevant morphological characters and species co-occurrence in Percina darters. I combined a molecular phylogeny for 37 Percina species with morphological and species co-occurrence data for each species. I found that the frequency of co-occurrence among Percina species is positively correlated with the rate of diversification in morphology suggesting, as long postulated by ecologists, a strong role for morphological, and by extension ecological, divergence in promoting species co-existence. Second, I investigated the temporal dynamics of habitat diversification across darters. I combined a molecular phylogeny with physical habitat and geographic range data for 189 species. I found that habitat type is highly conserved among closely related species due to a two-fold decrease in the rate of ecological diversification following the origin of the major darter clades. This decrease in rate is itself likely the result of limited habitat availability due to the geographic restriction of many of the clades.
Liliana M. Dávalos-Álvarez
Department of Ecology and Evolution, Consortium for Inter-Disciplinary Environment Research, State University of New York at Stony Brook
Space and time travel using phylogenetics
Anthropogenic climate change and habitat fragmentation frame all ecological interactions on Earth today. The scale of such environmental change is unprecedented in human history, but not in geological time. My research uses phylogenies to both investigate the role of past environmental change in shaping today’s communities and model the future of populations under alternative climate change scenarios. These analyses combine phylogenetics, population genetics, and environmental niche modeling to obtain colonization and extinction parameters for Caribbean bats. The diversity and endemism of the West Indies can be explained by faunal exchange with the continent during brief periods of low sea level, and increased extinction rates during high sea level stands. These methods provide a framework for identifying the species most vulnerable to climate change, and those more likely to maintain gene flow across barriers and persist despite rapid environmental change.
Erika J. Edwards
Assistant Professor of Biology
Department of Ecology and Evolutionary Biology, Brown University
The global biogeography of C4 grasses: discerning the effects of physiological novelty from historical contingency
C4 photosynthesis refers to a suite of biochemical and anatomical traits that promote high photosynthetic rates in high light, high temperature environments. While the C4 pathwayhas evolved in numerous angiosperm lineages, it is most common in the grasses. Globally, C4 grasses are dominant members of tropical grassland/savanna communities and are conspicuously absent from cooler climates. The C4 pathway has been exclusively invoked to explain this striking biogeographical pattern; however, C4 photosynthesisevolved only in grass lineages of tropical origin, so an alternative hypothesis is that C4grasses were pre-adapted to warm climates and that photosynthetic pathway variation isnot the primary driver of perceived C3/C4 sorting along temperature gradients. A phylogenetic analysis of climate niche for 156 grass species co-occurring in the Hawaiian Islands revealed strong phylogenetic niche conservatism for temperature. Most coolclimate grasses belong to the exclusively C3 “BEP” grass clade, while most warm climate grasses belong to the “PACCMAD” clade, which contains a mix of both C3 andC4 species. Within the PACCMAD clade, shifts to C4 photosynthesis were more strongly correlated with lower precipitation than with higher temperatures. Our results highlight the fundamental difficulties in assigning proper ‘cause and effect’ to trait-environment relationships without a phylogenetic perspective. We are currently testing our results from the Hawaii study with a global dataset unprecedented in size (a grass phylogenywith >1,000 species, climate data from >900,000 specimens), and here I present initial new insights from this ‘mega-analysis’.
Matthew R. Helmus
Postdoctoral Research Fellow
Xishuangbanna Tropical Botanical Garden, Kunming, China
Evolutionary history explains species invasions and extinctions at the confluence of nearctic and neotropical freshwater fishes
Humans have homogenized the biota of many ecological communities by causing exotic species invasions and native species extinctions. Understanding the details of any particular broad-scale homogenization event is difficult because both species invasion success and extinction susceptibility depend on species-specific traits and geographic contingencies. However, these dependences should result in nonrandom invasion and extinction patterns across phylogenetic trees because closely related species typically share similar traits and are typically found in the same region where their lineage speciated. Here, I analyzed the biotic homogenization that is occurring among freshwater fish communities located at the biogeographic confluence of neartic and neotropical faunas. I resampled over 150 freshwater fish communities in central Mexico that were previously sampled in the last 100 years. Natives with high extinction probability were of neartic evolutionary origin, while highly invasive exotics were closely related to tolerant natives of neotropical origin. This phylogenetic signal was due to both conserved species tolerances and to different geographic centers of clade diversity having different amounts of human impact. I then developed a predictive model to estimate other fish species extinction and invasion probabilities. Evolutionary history can thus be used to understand patterns of biotic homogenization and predict future changes to biodiversity.
Steven W. Kembel
Center for Ecology and Evolutionary Biology, University of Oregon
Ecology without species: phylogenetic perspectives on microbial diversity
Microbial ecologists have long recognized the value of a phylogenetic perspective on diversity, due in part to the challenges of taxonomic classification and species delimitation in microbes. The increasing availability of metagenomic data from environmental shotgun sequencing offers the potential to revolutionize our understanding of ecological communities, and will likely drive the development of a new conceptual framework for understanding biological diversity that focuses on individual organisms rather than on classical taxonomic ranks such as species. I give an overview of the conceptual and practical challenges of working with metagenomic data, and present a metagenomic analysis of environmental and spatial diversity gradients in marine microbial communities. I show that taxonomic and phylogenetic diversity vary independently along these gradients, and discuss the implications of these findings for our understanding of the ecology and evolution of diversity in microbial communities.
John R. Paul
Department of Biology, Colorado State University
Explaining variation in the distribution and abundance of species using a phylogenetic approach
Understanding variation in the abundance and distribution of species is a central theme in ecology. Recently, the role that phylogenetic relationships may play in ecology has become increasingly apparent. Although several studies have examined the phylogenetic structure of communities, few have explicitly linked phylogeny to variation in abundance and distribution. My research aims to elucidate how phylogenetic information can help explain interspecific variation in geographic range sizes and local abundances, focusing on the diverse tropical plant group Psychotrieae (Rubiaceae). To address variation in range size, I combined Bayesian relaxed‐clock dating of DNA sequences and ecological niche modeling. I found that in one clade of Psychotria, younger species have colonized a smaller proportion of their potential range extent than older species. I argue that an evolutionary time for‐dispersal effect is responsible for this pattern. To address variation inabundance, I collected data from 240 transects, nested in seven Psychotrieae species communities in Costa Rica, and developed a novel approach to examine how phylogenetic structure relates to the variation in abundance among species. I found significant relationships between variation in abundance, species richness, and community phylogenetic structure, and examined these results in light of niche conservatism, ecological interactions, and the geography of speciation.
Enrico L. Rezende
Department of Genetics and Microbiology, Universitat Autonoma de Barcelona
Phylogenetic effects in ecological networks of species interactions
Network theory and the phylogenetic comparative method have been recently applied by ecologists to study two general phenomena underlying community structure: species evolve and species interact with one another. However, few studies have attempted to investigate these phenomena in a unified framework, and we currently lack analytical apporaches to study how evolutionary history affects current patterns of species interactions. In the present seminar I will discuss how phylogenetic statistical tools and other analytical approaches employed in evolutionary physiology can be applied to study networks of species interactions. These methods allow researchers to study (i) the relative contribution of evolutionary history to community structure, (ii) whether these effects are consistent across communities, (iii) which phenotypic or ecological attributes might underlie observed phylogenetic effects. The seminar will be focusing on my previous and ongoing research on phylogenetic effects on plant‐animal mutualistic networks and food webs. Nonetheless, the approaches highlighted in the talk are very general and can be employed to study a wide variety of ecological networks.
Nathan G. Swenson
Postdoctoral Fellow in Bioinformatics
Center for Tropical Forest Science — Asia Program, Harvard University Herbaria
Stochastic and deterministic temporal turnover of the tree composition in a tropical rain forest: the role of phylogeny and species function
Gaining deeper insight into the processes driving community structure and dynamics will require ecologists to move beyond taxonomically-based assessments of communities. Information pertaining to the function and evolutionary history of species is required to directly test mechanistic hypotheses regarding community structure. Recent extensions of theoretical population genetics to descriptions of community structure provide novel metrics to partition functional and phylogenetic diversity into alpha and beta components. To move beyond the classic taxonomically-based paradigm we use these new metrics to simultaneously quantify species, functional, and phylogenetic beta-diversity, or temporal turnover, within a tropical rain forest with a dynamic history. The results show: (i) that species beta-diversity is generally uncorrelated with functional and phylogenetic beta-diversity and that the species compositional similarity has tended to decay through time at a faster rate than the decay in phylogenetic and functional compositional similarity through time; and (ii) that while the functional and phylogenetic turnover in this forest was stochastic in the early stages following disturbance, in later stages the turnover became largely deterministic. Ultimately, the results show that mechanistic insights into tropical forest community structure and dynamics, particularly in successional forests, can be obtained by explicitly incorporating information regarding the phylogenetic relatedness and function of species and that stochastic and deterministic processes both play a role in tropical forest succession.