Selection is frequency dependent when an individual's fitness depends on the frequency of its phenotype. Frequency-dependent selection should be common in gynodioecious plants, where individuals are female or hermaphroditic; if the fitness of females is limited by the availability of pollen to fertilize their ovules, then they should have higher fitness when rare than when common. To test whether the fitness of females is frequency dependent, we manipulated the sex ratio in arrays of gynodioecious...

Fluid-feeding insects, such as butterflies, moths and flies (20% of all animal species), are faced with the common selection pressure of having to remove and feed on trace amounts of fluids from porous surfaces. Insects able to acquire fluids that are confined to pores during drought conditions would have an adaptive advantage and increased fitness over other individuals. Here, we performed feeding trials using solutions with magnetic nanoparticles to show that butterflies and flies have...

Streams are being subjected to physical, chemical, and biological stresses stemming from both natural and anthropogenic changes to the planet. In the face of limited time and resources, scientists, resource managers, and policy makers need ways to rank stressors and their impacts so that we can prioritize them from the most to least important (i.e., perform 'ecological triage'). We report results from an experiment in which we established a periphyton community from the Huron River...

The ecological and physiological significance of body size is well recognized. However, key macroevolutionary questions regarding the dependency of body size trends on the taxonomic scale of analysis and the role of environment in controlling long-term evolution of body size are largely unknown. Here, we evaluate these issues for decapod crustaceans, a group that diversified in the Mesozoic. A compilation of body size data for 792 brachyuran crab and lobster species reveals that their maximum,...

Physicochemical and ecological attributes of ecosystems (i.e., environmental context) can modify the exposure and effects of metals, which presents a challenge for ecosystem management. Furthermore, the functional and structural attributes of an ecosystem may not respond equally to metals or be uniformly responsive to environmental context. We explored how physicochemical and ecological context modified sediment metal dose-response for a suite of functional and structural measures. Two sediments with high (HB) and low (LB) acid volatile...

Many genera of terrestrial vertebrates diversified exclusively on one or the other side of Wallace’s Line, which lies between Borneo and Sulawesi islands in Southeast Asia, and demarcates one of the sharpest biogeographic transition zones in the world. Macaque monkeys are unusual among vertebrate genera in that they are distributed on both sides of Wallace‘s Line, raising the question of whether dispersal across this barrier was an evolutionary one-off or a more protracted exchange—and if...

The expansion of woody plants into grasslands and old fields is often ascribed to fire suppression and heavy grazing, especially by domestic livestock. However, it is also recognized that nutrient availability and interspecific competition with grasses and other woody plants play a role in certain habitats. I examined potential factors causing range- and niche expansion by the eastern redcedar Juniperus virginiana, the most widespread conifer in the eastern United States, in multifactorial experiments in a...

Plant ecosystem structure is understood to be a result of complex multitrophic interactions. Most multitrophic studies focus on plant aboveground adaptations to aboveground herbivore pressures, neglecting belowground adaptations in response to aboveground damage. Differential investment in root structures may allow plants to compensate for tissue loss or damage due to herbivores. Furthermore, phylogeny may constrain a plant’s ability to adapt belowground. We examined the belowground responses of 12 species of oak (Quercus) to varying locations...

1. Plant functional traits have revealed trade-offs related to life-history adaptations, geographical distributions, and ecosystem processes. Fine roots are essential in plant resource acquisition and play an important role in soil carbon cycling. Nonetheless, root trait variation is still poorly quantified and rarely related to the rest of the plant. 2. We examined chemical and morphological traits of 34 temperate arbuscular mycorrhizal tree species, representing three main angiosperm clades (super-orders asterid, magnoliid and rosid). We...

Assembly of fungal communities remains poorly understood in part because of the daunting range of spatial scales that may be involved in this process. Here, we use individual leaves as a natural sampling unit, comprising spatially distinct habitat and/or resource patches with unique histories and suites of resources. Spatial patterns in fungal beta diversity were tested for consistency with the metacommunity paradigms of species sorting and neutral dynamics. Thirty senesced leaves were collected from the...

The diversity of genome sizes across the tree of life is of key interest in evolutionary biology. Various correlates of variation in genome size, such as accumulation of transposable elements or rate of DNA gain and loss, are well known, but the underlying molecular mechanisms that drive or constrain genome size are poorly understood. Here we study one of the smallest genomes among frogs characterized thus far, that of the ornate burrowing frog (Platyplectrum ornatum)...

As agricultural practices intensify, species once common in agricultural landscapes are declining in abundance. One such species is the monarch butterfly (Danaus plexippus L.), whose eastern North American population has decreased approximately 80% during the past 20 years. One hypothesis explaining the monarch’s decline is reduced breeding habitat via loss of common milkweed (Asclepias syriaca L.) from agricultural landscapes in the north central United States due to adoption of herbicide tolerant row crops. Current efforts...

The evolution of plant defenses is often constrained by phylogeny. Many of the differences between competing plant-defense theories hinge upon the differences in the location of meristem damage (apical vs. auxiliary) and the amount of tissue removed. We analyzed the growth and defense responses of 12 Quercus (oak) species from a well-resolved molecular phylogeny using phylogenetically independent contrasts. Access to light is paramount for forest-dwelling tree species, such as many members of the genus Quercus....

Long term evolution experiments have tested the importance of genetic and environmental factors in influencing evolutionary outcomes. Differences in phylogenetic history, recent adaptation to distinct environments, and chance events all influence the fitness of a population. However, the interplay of these factors on a population's evolutionary potential remains relatively unexplored. We tracked the outcome of 2,000 generations of evolution of four natural isolates of Escherichia coli bacteria that were engineered to also create differences in...

PREMISE OF THE STUDY: Gynodioecy is a sexual polymorphism whereby female and hermaphroditic plants co-occur within populations. In many gynodioecious species, stressful abiotic environments are associated with higher frequencies of females. This association suggests that abiotic stress affects the relative fitness of females and hermaphrodites and, thus, the maintenance of gynodioecy. METHODS:To test whether abiotic stress affects the fitness of females and hermaphrodites, we grew open-pollinated Lobelia siphilitica families in temperature regimes characteristic of the...

Background: Transitions in habitats and feeding behaviors were fundamental to the diversification of life on Earth. There is ongoing debate regarding the typical directionality of transitions between aquatic and terrestrial habitats and the mechanisms responsible for the preponderance of terrestrial to aquatic transitions. Snail-killing flies (Diptera: Sciomyzidae) represent an excellent model system to study such transitions because their larvae display a range of feeding behaviors, being predators, parasitoids or saprophages of a variety of mollusks...

Ecotones are important landscape features where there is a transition between adjoining ecosystems. However, there are few generalized hypotheses about the response of communities to ecotones, except for a proposed increase in species richness that receives varying empirical support. Based on the assumption that transport of abiotic material and dispersal of organism propagules across ecotones are independent processes, we propose the new hypothesis that ecotones decouple community-environment relationships, increasing the importance of spatial structure that...

Floral phenotypic traits are expected to reflect evolutionary changes and are used as a reliable basis for species delimitation. However, when traits overlap among populations of newly emerging species, this confounds identification of evolutionarily distinct lineages and reduces taxonomic stability. In this study, we quantified variation in ten floral traits and plastid DNA sequences across 26 populations of Platanthera dilatata (Orchidaceae) in North America to determine geographic structure among populations and to evaluate support for...

Rationale: Changes in fine-root morphology are typically associated with transitions from the ancestral arbuscular mycorrhizal (AM) to the alternative ectomycorrhizal (ECM) or non-mycorrhizal (NM) associations. However, the modifications in root morphology may also coincide with new modifications in leaf hydraulics and growth habit during angiosperm diversification. These hypotheses have not been evaluated concurrently, which limits our understanding of the causes of fine-root evolution. Methods: To explore the evolution of fine-root systems, we assembled a 600+...

Research into the epigenome is of growing importance as a loss of epigenetic control has been implicated in the development of neurodegenerative diseases. Previous studies have implicated aberrant DNA and histone methylation in multiple sclerosis (MS) disease pathogenesis. We have previously reported that the methyl donor betaine is depleted in MS and is linked to changes in histone H3 trimethylation (H3K4me3) in neurons. We have also shown that betaine increases histone methyltransferase activity by activating...

Lobsters are a ubiquitous and economically important group of decapod crustaceans that includes the infraorders Polychelida, Glypheidea, Astacidea and Achelata. They include familiar forms such as the spiny, slipper, clawed lobsters and crayfish and unfamiliar forms such as the deep-sea and “living fossil” species. The high degree of morphological diversity among these infraorders has led to a dynamic classification and conflicting hypotheses of evolutionary relationships. In this study, we estimated phylogenetic relationships amongst the major...

In many gynodioecious species, cytoplasmic male sterility genes (CMS) and nuclear male fertility restorers (Rf) jointly determine whether a plant is female or hermaphrodite. Equilibrium models of cytonuclear gynodioecy, which describe the effect of natural selection within populations on the sex ratio, predict that the frequency of females in a population will primarily depend on the cost of male fertility restoration, a negative pleiotropic effect of Rf alleles on hermaphrodite fitness. Specifically, when the cost...

Intraspecific coevolution between selfish elements and suppressors may promote interspecific hybrid incompatibility, but evidence of this process is rare. Here, we use genomic data to test alternative models for the evolution of cytonuclear hybrid male sterility in Mimulus. In hybrids between Iron Mountain (IM) Mimulus guttatus × Mimulus nasutus, two tightly linked M. guttatus alleles (Rf1/Rf2) each restore male fertility by suppressing a local mitochondrial male-sterility gene (IM-CMS). Unlike neutral models for the evolution of...

Local community structure is shaped by processes acting at local and landscape scales. The relative importance of drivers operating across different spatial scales are difficult to test without observations across regional or latitudinal gradients. Cities exhibit strong but predictable environmental gradients overlaying a mosaic of highly variable but repeated habitat types within a constrained area. Thus, cities present a unique opportunity to explore how both local and landscape factors influence local biotic communities. We used...

1. Plant responses to major environmental drivers like precipitation can influence important aspects of carbon (C) cycling like soil CO2 efflux (JCO2). These responses may be predicted by two independent classes of drivers: plant size—larger plants respire more and produce a larger quantity of labile C, and plant economics—plants possessing more acquisitive plant economics strategies (i.e., high metabolic rate and tissue nutrient content) produce higher-quality tissue that respires rapidly and decomposes quickly. 2. At two...