Keynote speakers
Rosemary gillespie
Island time and the interplay between ecology and evolution in species diversification
Abstract
Research on the dynamics of biodiversity has progressed tremendously over recent years, though in two separate directions – ecological, to determine change over space at a given time, and evolutionary, to understand change over time. Integration of these approaches has remained elusive. Archipelagoes with a known geological chronology provide an opportunity to study ecological interactions over evolutionary time. In this presentation I will focus on the Hawaiian archipelago and summarize the development of ecological and evolutionary research, emphasizing spiders because they have attributes allowing analysis of ecological affinities in concert with diversification. I highlight recent insights from the island chronosequence, in particular the importance of (1) fusion and fission in fostering diversification; (2) variability upon which selection can act; and (3) selection and genetic drift in generating diversity. Insights into biodiversity dynamics at the nexus of ecology and evolution are now achievable by integrating new tools, in particular ecological metrics (interaction networks, maximum entropy inference) across the chronosequence to uncover community dynamics; and genomic tools to understand contemporaneous microevolutionary change. This work promises insights into biodiversity dynamics by showing not only how diversity has been shaped in the past, but also how it might accommodate change in the future.
Tadashi fukami
Embracing historical contingency in community assembly
Abstract
The order of species arrival during community assembly can be a major determinant of the structure and function of ecological communities. Such historical contingency, called priority effects, is often viewed as a nuisance that hinders progress in our understanding of community assembly. In this talk, I will argue that historical contingency should be embraced, rather than ignored, in order to advance community ecology. To make this point, I will discuss four recent and ongoing projects at the interface of ecology and evolution as illustrative examples: (1) combined analysis of field, laboratory, and theoretical results, demonstrating how phylogenetic relatedness predicts the strength of priority effects in nectar microbes and how the microbes may alter the effect of flowering phenology on pollination, (2) phylogenetic and abundance analysis of New Zealand alpine plants, suggesting how environmental stress influences the strength of priority effects in evolutionary diversification, (3) laboratory bacterial experiments, demonstrating how pre-adaptation history of immigrants determines the strength of priority effects in evolutionary diversification, and (4) theoretical simulation modeling, indicating how rapid evolution of traits helps to maintain local priority effects and promote regional species coexistence.
Presenters
Rachel germain
Species coexistence: macroevolutionary relationships and the contingency of historical interactions
Abstract
Evolutionary biologists since Darwin have hypothesized that closely related species compete more intensely and are therefore less likely to coexist. However, recent theory posits that species diverge in two ways: either through the evolution of ‘stabilizing differences’ that promote coexistence by causing individuals to compete more strongly with conspecifics than individuals of other species, or through the evolution of ‘fitness differences’ that cause species to differ in competitive ability and lead to exclusion of the weaker competitor. We tested macroevolutionary patterns of divergence by competing pairs of annual plant species that differ in their phylogenetic 2 relationships, and in whether they have historically occurred in the same region or different regions (sympatric vs. allopatric occurrence). For sympatrically-occurring species pairs, stabilizing differences rapidly increased with phylogenetic distance. However, fitness differences also increased with phylogenetic distance, resulting in coexistence outcomes that were unpredictable based on phylogenetic relationships. For allopatric species, stabilizing differences showed no trend with phylogenetic distance, whereas fitness differences increased, causing coexistence to become less likely among distant relatives. Our results illustrate the role of species’ historical interactions in shaping how phylogenetic relationships structure competitive dynamics, and offer an explanation for the evolution of invasion potential of non-native species.
robin hopkins
The causes and consequences of natural selection for speciation
Abstract
Understanding the role of natural selection in the process of species formation is one of the fundamental goals of evolutionary biology. My work incorporates molecular biology, population genetic analyses, and field-based selection experiments to better understand how selection drives the evolution of reproductive isolation. I study reinforcement, the process in which reduced hybrid fitness generates selection for the evolution of reproductive isolation between emerging species. Specifically, I focus on the native Texas wildflower, Phlox drummondii, which has evolved flower color variation in response to reinforcing selection. Identifying the genetic basis of reinforcement has allowed me to better measure the strength of selection. I investigate both the benefits and costs of reinforcement and strive to understand the mechanism underlying the selection. Through this work, I seek to better understand how two diverging lineages can co-occur in a population through the evolution of reproductive isolation.
melissa kemp
Community assembly (and disassembly) dynamics as revealed by the fossil record
Abstract
Determining the factors that shape diversity and the persistence of species is a major aim of ecology and evolutionary biology. Empirical data from present-day ecosystems have proven critical in characterizing how species interact with one another and their environment, but many of these studies lack a crucial element that would make them more broadly applicable: temporal resolution. I use Quaternary Caribbean lizards to investigate ecological theory about the repercussions of colonization and extinction on community structure. I describe a Caribbean-wide trend of size-biased and lineage-specific extinction. These extinctions alter community structure permanently, serving as a predator release on some islands. Throughout the Lesser Antilles, these extinctions erode the replicate nature of communities that existed on the islands in prehistoric times, and recent introductions cause further divergence. Further, the introduced species are ecologically distinct from extinct species and possess traits that may facilitate their ability to persist in human-modified habitats, whereas extinct species possessed traits that may be selected against in landscapes with a significant human presence. My results highlight the importance of fossil data in assessing community change, and provide a glimpse into the potential outcomes of continued colonization and extinction in the Anthropocene.
jp lessard
Improving phylogenetic and trait-based inference of biotic interactions with process-based species pool definitions
Abstract
A persistent challenge in ecology is to tease apart the influence of multiple processes acting simultaneously and interacting in complex ways to shape community structure. I developed a heuristic null model approach that relies on explicitly defining species pools and which permits assessing the relative influence of the main processes thought to shape community structure: environmental filtering, dispersal limitations and biotic interactions. In this presentation, I implement this approach using data on the community composition, global distributions, phylogeny and morphological traits of hummingbirds. Results from these analyses call for a reexamination of a multitude of phylogenetic- and trait-based studies that did not explicitly consider potentially important processes in their definition of the species pool. I conclude that this heuristic approach provides a transparent way to explore patterns and refine interpretations of the underlying causes of assemblage structure.
D. luke mahler
The assembly of island lizard faunas through diversification on macroevolutionary adaptive landscapes
Abstract
Research on community assembly has traditionally focused either on the role of local ecological interactions or on the role of historical processes that shape the regional species pool. Disentangling the relative importance of these factors in the assembly of communities remains an outstanding challenge in ecology and evolution. Replicated adaptive radiations occurring within large islands provide unique opportunities for studying the interplay of local ecology, geography and macroevolution during faunal assembly. I’ll discuss how a model of the macroevolutionary adaptive landscape can help to explain the repeated evolution of specialized niche use in island lizards diversifying on the Greater Antilles. Convergent ecological shifts on similar islands suggest a deterministic component to faunal assembly, although large islands also show evidence for numerous non-convergent shifts. Inferences about the timing and geographic setting of niche shifts yield insights into the ecological stability of island faunas and suggest a role for geographic area in determining the ecological diversity of entire island faunas as well as their local communities.
andy rominger
The statistical mechanics of biodiversity in evolving island communities
Abstract
Applying static ecological theories in rapidly evolving ecosystems can highlight what about the evolutionary process drives communities away from statistical idealizations. Using the chronosequence afforded by the Hawaiian Islands to capture snapshots of arthropod communities at different evolutionary ages and stages of ecological assembly, I have tested static ecological theories of herbivory network structure and the distributions of abundances and metabolic rates across species. To do so I developed an open source R package implementing an approach to theory development in ecology based on the principle of maximum information entropy. This framework seeks to predict distributions of interest, such as abundance distributions, without invoking any specific mechanistic assumptions but instead by finding the solution that an ideal system would reach in equilibrium. Thus deviations from this theory can reveal the nature of unique mechanisms behind the observed structure of biodiversity. My studies of network linkage, abundance and metabolic distributions indicate that rapid assembly from immigration and speciation in young ecosystems and extinction in old ecosystems could drive observed patterns.
Megan Rúa
Variation in plant and fungal traits indicate mycorrhizal mediated selection in Pinus radiata
Abstract
Coevolution describes evolutionary change in which two or more interacting species reciprocally drive each other’s evolution, potentially driving trait diversification and ecological speciation. Yet, we still understand very little about how coevolution works in multi-species interactions or about the relative importance of biotic and abiotic sources of selection. Interactions between conifers and their microbes are ideal for such studies as conifers form obligate associations with mutualistic ectomycorrhizal fungi, and these interactions vary along abiotic gradients. Using genotypes of Monterey pine (Pinus radiata) from geographically separated sites along the coast of California and Baja California, as well as crosses to represent intermediate phenotypes/genotypes, I performed a common garden experiment examining the relationship between sources of selection on candidate coevolving traits. We found direct linear selection on all traits, but the strength of selection differed for fungal and plant traits. The strength of selection was greatest for fungal traits (foraging strategy) while plant traits (relative growth rate, diameter, root:shoot, specific root length) were all undergoing moderate to no selection. Variation in these traits of the symbiosis indicates an important step in establishing evolution in response to abiotic variation. This work represents the first field-based, community-level approach towards investigating selection in mycorrhizal relationships.
