Stand Alone Conference of the American Society of Naturalists
Asilomar Conference Grounds, Pacific Grove, California, 5-9 January 2018
The full program including the entire talk and poster schedule and abstracts can be downloaded here.
A shorter version of the program including the entire talk and poster schedule but no abstracts can be downloaded here.
Saturday Evening, 6 January 2018
Posters & Mixer
8:30 PM in the Chapel
|P1||Sarah Sanderson||Phenotypic variation of native and exotic fish species along an ion gradient in the Upper St. Lawrence River|
|P2||Laura Vander Meiden||Using network analysis to determine species' roles in mixed-species flocks|
|P3||Arthur Weis||Adding the temporal dimension to isolation by distance|
|P4||Justin Bain||The effects of floral resource removal on plant-pollinator interactions: evidence for a diversity of responses|
|P5||Ellen Simms||Do rare or introduced rhizobia escape their enemies?|
|P6||Carrie Barker||The effects of forest type and microclimate on growth traits of dominant tree species at La Selva Biological Station, Costa Rica|
|P7||Luana Maroja||Reproductive and genomic isolation between inter-fertile behavioral semi-species of Drosophila athabasca complex|
|P8||Joseph Braasch||Effective populations sizes across the range expansion of an invasive plant|
|P9||Christopher Klausmeier||Trait-based eco-evolutionary modeling with Mathematica|
|P10||Marion Donald||Effects of forest fragmentation and keystone species loss on nectar microbial community composition|
|P11||Hannah Justen||Characterization of Clock gene polymorphism across Saxicola populations and migratory phenotypes|
|P12||Aubrie James||Specialist bee pollinators phenologically matched with Clarkiai> blooming at the community level|
|P13||Gaku Takimoto||Flower constancy by pollinators drives ecological speciation of flowering plants|
|P14||Marta Shocket||Food resources as ecological and evolutionary drivers of seasonal disease in a Daphnia-fungus system|
|P15||David Smith||Plasticity, population structure and tadpoles on a habitat gradient|
|P16||Joan Edwards||Near-complete records of flower visitors support a neighborhood model of pollination|
|P17||Manuel Morales||Plant-herbivore dynamics in an herbivore protection mutualism|
|P18||Jennifer Ison||Taking genetic structure to a new dimension: Quantifying temporal and spatial pollen movement in field populations of Brassica rapa|
|P19||Daniel Smith||Towards a mechanistic basis of the thermal plasticity of ectotherm fecundity|
A guide for presenters to format their presentations can be found here.
Phenotypic variation of native and exotic fish species along an ion gradient in the Upper St. Lawrence River
All organisms have range limits that often arise when species are unable to adapt to extreme conditions. Range limits are particularly important for invasive species because they help limit their spread and hence their impacts. The invasive round goby (Neogobius melanostomus) has spread through the Laurentian Great Lakes having important effects on native species. In the upper St. Lawrence River, particularly in Lake St-Louis, one factor that might limit the spread of round gobies are the low-ion waters associated with runoff from the boreal shield. In this habitat, ion gradients determine refuge vs. invaded habitats because native species are found in both low-ion and high-ion habitats. Here, we study phenotypic variation of native and invasive fish species to investigate adaptions to low-ion water.
Using network analysis to determine species’ roles in mixed-species flocks
Laura Vander Meiden and Daizaburo Shizuka
In animal communities, species role differentiation can lead to dependencies between species. Knowing these dependencies is integral for understanding these systems. In mixed-species flocks of birds, some species play the role of nuclear species, facilitating flock formation and cohesion, while others play the role of satellite species. Satellite species are dependent on the nuclear species for flock formation and thus the benefits of flock membership. In this study, we looked at mixed-species flocks from 24 different study sites around the world to determine whether network analysis can be used to assess species' roles within flocks. Using presence-absence matrices, we calculated strengths of association between species. We constructed social networks using these strengths of association to determine which species have the highest indices of centrality and whether these correspond with the expected nuclear species. Similar social network approaches could be key in determining species roles and dependencies in other animal communities.
Adding the Temporal Dimension to Isolation by Distance
Arthur Weis and Madeline A. W. Peters
Wright suggested that with limited dispersal distances, populations can build spatial genetic structure even on a continuous, uniform landscape. Subsequent models have confirmed that when genetic neighborhoods (mating pools) are small, local inbreeding leads to genotype clustering. However, mating pools will also be temporally structured when there is genetic variation in mating phenology. We are exploring the interaction of spatial and temporal mating pool structure on heterozygosity and linkage disequilibrium within and between loci that control mating phenology and unlinked neutral loci. Our simulation models mimic hermaphroditic, annual plants, where dispersal is through pollen. Assortative mating by flowering time adds a temporal dimension to the mating pool decreasing the genetic neighborhood size. Local inbreeding thus occurs even when the scale of dispersal is too large to cause spatial isolation on its own, with consequences for genetic drift.
The Effects of Floral Resource Removal on Plant-Pollinator Interactions: Evidence for a Diversity of Responses
Justin Bain, Rachel G. Dickson, and Paul J. CaraDonna
An important component of understanding the dynamics and stability of communities is to elucidate how species interactions respond to disturbance. We address this issue by experimentally removing a dominant floral resource from an intact subalpine plant community, and exploring its effects on plant-pollinator interactions. Specifically, we investigated how this removal affects pollinator visitation rates and the topological properties of plant-pollinator interaction networks. Overall, we observed a reduction in visitation rates in response to the removal; however, at the species level, removal both reduced and increased visitation to the two other common co-flowering species. The topological properties of the networks exhibited variation in response to the removal, but only during peak flowering of the dominant plant species. Our findings illustrate the complexity of responses that can occur with the removal of a dominant resource, with implications for our understanding of the stability and dynamics of ecological interactions in response to disturbance.
Do rare or introduced rhizobia escape their enemies?
Ellen L. Simms, Jannick Van Cauwenberghe, Stephanie S. Porter, and Kimberly J. La Pierre
Biological invasion is a well-studied phenomenon, but some invasions are cryptic and poorly understood. Rhizobia are soil-dwelling bacteria that infect legumes to engage in an endosymbiotic nitrogen-fixation mutualism. Rhizobia are not transmitted in legume seeds, yet invading legumes often associate with rhizobia closely related to rhizobia from their home range. Were these rhizobia introduced or have they proliferated in response to encountering an appropriate host? Either scenario represents a founder event during which natural enemies might have been lost. Bacteriophages, specialized natural enemies of bacteria, cause significant mortality that can structure bacterial populations. Do rhizobia associated with invading legumes encounter fewer or less diverse bacteriophage enemies? To answer this question, we are using Bradyrhizobium bacteria associated with native and introduced legumes to trap bacteriophages from California soils.
The effects of forest type and microclimate on growth traits of dominant tree species at La Selva Biological Station, Costa Rica
Secondary forests have reduced plant species richness compared to primary forests, although certain species are found in both forest types. Plants may occur in both habitats by taking advantage of beneficial microclimates. I tested whether forest type or microclimate affects growth traits of two dominant species, Pentaclethra macroloba and Welfia regia, that are commonly found in primary and secondary forests. I sampled juveniles from both forest types and measured height, number of leaves, and length of longest leaf. To measure microclimate I recorded canopy openness and soil compaction. I found that soil compaction had a negative effect on height for P. macroloba and canopy openness had a negative effect while soil compaction had a positive effect on the number of leaves for W. regia, but forest type did not have an effect. This suggests that microclimate is more influential than forest type for traits indicative of growth in these species.
Reproductive and genomic isolation between inter-fertile behavioral semi-species of Drosophila athabasca complex
The Drosophila athabasca species complex is thought to exemplify rapid speciation. The three semi-species WN, EA and EB, may have evolved sexual isolation in as little as several thousand years, driven mostly by divergent female mating preferences for male courtship songs. We studied reproductive and genetic isolation within and between semi-species and compared sympatric and allopatric populations. Sexual isolation is essentially complete in both sympatry and allopatry with signs of reinforcement. We used ngs of 52 genes (nearly 23K bp per individual) to analyze 319 iso-female lines across 21 populations. At the within-taxon level, we found: 1) low levels of genetic variation, 2) genetic evidence of population expansions, and 3) no evidence of isolation-by-distance, except for WN populations separated by nearly 4,000 km. Analyses across taxa showed low interspecific sequence divergence, but detectable genetic structure, with individuals and populations clustering based on their taxon identity. We also uncovered extremely low levels of historical heterospecific gene flow. Finally, we question previous claims that divergence within this species complex is as recent as several thousand years, demostrating that it is at least 100K years. Given the near-complete sexual and genetic isolation in sympatry, we argue that these are good species.
Effective populations sizes across the range expansion of an invasive plant
Joseph Braasch and Katrina Dlugosch
The capacity for adaptation can be summarized by effective population size (Ne), which represents the randomness in allele fluctuations over time. Populations with greater Ne may therefore be better able to exhibit allelic changes in line with those predicted by selection alone, and are more likely to exhibit phenotypes indicative of local adaptation. Variation in Ne at the scale of populations is rarely documented though, as is the reason for the existence of variation. We estimated contemporary Ne for 12 invasive populations of the weed Centaurea solstitialis in California using the linkage disequilibrium method with double digest RAD-seq genomic data. We found that across this range there exists substantial variation in Ne which appears to be the result of date of colonization and climatic variables which effect census population sizes. This results match theoretical and in vitro studies demonstrating weak responses to selection and reduced fitness at the leading edge of range expansions.
Trait-based eco-evolutionary modeling with Mathematica
Trait-based eco-evolutionary modeling provides an integrative framework that incorporates life-history and physiological traits and trade-offs to predict the emergence of community structure. These modeling approaches include adaptive dynamics, quantitative genetics, and other moment-based methods. I will present a package for the Mathematica computational environment to easily analyze such trait-based models. Complications such as population structure, multiple traits and guilds, and non-equilibrium dynamics can be easily incorporated. These tools should open up trait-based modeling to a wider range of users.
Effects of forest fragmentation and keystone species loss on nectar microbial community composition
Marion Donald , Manpreet Dhami, Adam Hadley, Kara Leimberger, Tadashi Fukami, and Tom Miller
Deforestation is well documented as negatively affecting important ecosystem services, such as pollination and biodiversity richness. Yet, not much is known as to how the resulting forest fragmentation and loss of plant species affect nectar microbial communities, which can influence plant-pollinator mutualism. We tested the effects of forest configuration and loss of a keystone tropical forest herb (Heliconia tortuosa) on microbial communities found in floral nectar and on the bills of hummingbirds. Forest patches of similar configuration were paired, and all H. tortuosa plants were effectively removed from one of each of the paired sites. Since hummingbirds are the primary pollinators of H. tortuosa and vectors of nectar microbes, we hypothesize that sites in which H. tortuosa was removed will experience lower hummingbird visitation and this will be reflected by changes in the microbial species richness found in the flowers. Results are forthcoming and may have implications for forest conservation.
Characterization of Clock gene polymorphism across Saxicola populations and migratory phenotypes
Timing is essential for the survival and successful reproduction of migratory birds. The Clock gene has been identified as candidate gene for circannual timing processes, it is extremely homologous except for one variable exonic region that shows poly-Q lengths variation. Longer repeats have been associated with higher breeding latitude for various bird species. Some studies have also suggested a link of Clock gene variability with migratory timing. Here we characterize Clock gene variability across different stonechat populations at varying breeding latitude that also exhibit clear differences in migratory behaviour. The Saxicola complex allows us to examine genotype differences in closely related populations with different phenotypes, including one (resident) African population breeding at the equator experiencing the same 12:12 light/dark cycle throughout the year. Interestingly, the African stonechats showed little variability in clock genotype, while more variation was detected in the other populations, suggesting that the lack of light-entrainment might have selected for an optimized Clock genotype. The most variable Clock genotype also including longest alleles was found in Siberian stonechats, supporting previous findings with longer repeats found at higher breeding latitudes. Evaluating Clock gene variability in the context of migratory phenotype shows a stronger signal in autumn compared to spring, with shorter alleles associated with earlier timing of autumn migration.
Specialist bee pollinators phenologically matched with Clarkia blooming at the community level
Aubrie James and Elizabeth Magno
An important feature of specialized plant-pollinator relationships is phenological matching of floral display and pollinator availability. Though research has demonstrated that specialist bee pollinators can be phenologically adapted to bloom times, the scale of this relationship is less understood. Here, we ask if specialist and generalist bee pollinators of four species in the Clarkia plant genus (Onagraceae) displayed different patterns of emergence throughout the 2016 Clarkia growing season in Kern County, CA. We passively collected bees and estimated floral display of Clarkia daily in nine communities in the sympatric range of the Clarkia—three ‘early’, ‘mixed’, and ‘late’ blooming communities—on rotation. Specialist pollinators captured per day in each community type peaked at the same time as floral display in that community type, whereas generalists showed no trend. We conclude that specialist pollinator phenology is tightly linked to flowering phenology and that this relationship occurs at the plant community level.
Flower constancy by pollinators drives ecological speciation of flowering plants
In the presentation, I theoretically examine whether and what degree of flower constancy can drive ecological speciation of flowering plants subject to divergent natural selection from growth environments. I develop a population genetic model of two plant populations in different habitats with divergent growth conditions, and ask whether a mutant allele conferring a novel floral trait can spread through one of the populations, cause floral trait divergence, and result in reproductive isolation. I find two conditions important for speciation. First, speciation is facilitated when pollinator’s flower constancy to plants well adapted to local growth conditions is stronger than constancy to plants poorly adapted. Second, realistic levels of flower constancy can cause speciation if the rates of seed dispersal and pollinator movement between habitats are sufficiently low. These results suggest that pollinator-mediated selection coupled with divergent natural selection may be important to drive ecological speciation of flowering plants.
Food resources as ecological and evolutionary drivers of seasonal disease in a Daphnia-fungus system
Marta Shocket, Maja Sljivar, and Spencer Hall
Seasonal epidemics are ubiquitous, but their mechanistic drivers are often poorly understood. Many environmental factors change simultaneously and can impact host-parasite interactions via both ecological (plastic) and evolutionary (genetic) pathways. We investigated the ecological and evolutionary roles of food resources in a Daphnia-fungus disease system with seasonal epidemics. We collected lake water from five lakes during the epidemic season and performed host-growth assays with six genotypes to measure food impacts on host condition (linked to parasite performance) over time in each lake.Host condition (from resources) varied over time and space. Most (but not all) lakes showed similar reaction norms over time. Contrary to expectations, there was no trade-off for resource use between host genotypes (fast-growing clones were always bigger, regardless of variation in resources between lakes or over time). We discuss these results in the context of a field survey of concurrent natural epidemics in the same lakes.
Plasticity, population structure and tadpoles on a habitat gradient
David Smith , Luana Maroja, and Osama Brosh
The tadpoles of the boreal chorus frog on Isle Royale, Michigan occupy a persistence and predator gradient on the shores of Lake Superior. Tadpoles in the upper margin of the gradient occupy predator rich pools and express a strong plastic response in body shape and behavior. However, the opportunity for selection on these tadpoles is low because the majority of the tadpoles occupy the middle levels where predator levels are low. The population structure and phenotypic variability in the middle level tadpoles suggest that the plasticity in the upper pools is maintained indirectly by selection on tadpoles at mid-levels.
Near-complete records of flower visitors support a neighborhood model of pollination
Joan Edwards , Molly McEntee, and Jonathan MacDougall
Long-term time-lapse video provides near-complete records of flower visitors. Our studies of flowers including Cornus canadensis (bunchberry dogwood) and Primula misstasinica (bird's-eye primrose) show that insect taxa vary among sites indicating flowers rely on neighborhood insects for pollination services.
Plant-herbivore dynamics in an herbivore protection mutualism
Taking genetic structure to a new dimension: Quantifying temporal and spatial pollen movement in field populations of Brassica rapa
Jennifer Ison, Laura Leventhal, and Arthur E. Weis
Just as mating between neighboring plants can lead to spatial genetic structure, assortative mating by ﬂowering time can cause temporal genetic structure in species with heritable ﬂowering times. However, estimating the temporal genetic structure is problematic because of the phenotypic correlation of the trait of interest, flowering time, between dam and sire. We developed a novel method that isolates flowering time by holding the maternal contribution constant. In eight open-pollinated field plots of Brassica rapa, we sampled the pollen pool throughout the flowering season. In half of the plots, plants were aggerated into dense clusters to examine how small-scale spatial distribution impacted pollen movement. We used a Bayesian framework to assign paternity to 1,885 offspring from the field plots. We found temporal genetic structure for flowering time in seven of the eight field plots. We also found that temporal pollen movement varied based on the spatial distribution of the plants.
Towards a mechanistic basis of the thermal plasticity of ectotherm fecundity
Temperature affects most biological processes in ectotherms and numerous studies exemplify the importance of understanding its effect on life history traits. Surprisingly, few studies broadly consider the effect of temperature on lifetime fecundity, a key component of fitness. We investigate the temperature response of fecundity through two approaches: (1) a data analysis of previous studies that experimentally measure ectotherm fecundity at multiple constant temperatures and (2) a biophysical model based on the Sharpe-Schoolfield equation incorporating the two essential temperature dependent biological responses comprising fecundity – birth rate and reproductive period. We report two key results: (1) the thermal reaction norm of lifetime fecundity is a unimodal response that can be right skewed, left skewed, or symmetrical and (2) differential sensitivities to temperature of birth rate and reproductive period accurately describe the thermally plastic response of fecundity.