Richard Karban

• University of California, Davis

Plants form the foundation of most terrestrial ecosystems; therefore, plant chemistry can have important and far-reaching consequences for many ecological interactions and processes. Despite this, few studies have explicitly explored the spatial variation in plant chemistry. We mapped the distribution of volatile emissions of the mountain subspecie...

A survey conducted in the 1920s, prior to the chestnut blight, indicated that chestnuts and oaks were codominant canopy species in White Oak Canyon, Shenandoah National Park, Virginia. A second survey in 1977 suggested that chestnuts were being replaced by tree species present before the blight, particularly oaks. In 2021, we resurveyed the 10 site...

Many studies have found that volatile cues from damaged plants can induce resistance to herbivores in undamaged neighbors. However, fewer studies have examined the effects of soilborne cues. Furthermore, there are few studies that have considered the effects of plant-plant communication on plant reproduction. We conducted experiments with tomato se...

Herbivory is a major threat to virtually all plants, so adaptations to avoid herbivory will generally be selected. One potential adaptation is the ability to ‘listen in’ on the volatile cues emitted by plants that are experiencing herbivory and to then respond by ramping up defences. The nature of these volatile cues is poorly understood. Sagebrush...

Heat stress will be an increasing problem for plants and pollinators. Some Romneya coulteri flowers self-shade reproductive parts with vertically oriented petals; this keeps pistils 3–8 °C cooler. A previous study conducted outside of the plant’s native range found that self-shading flowers experienced higher seed set than flowers with petals that...

Many studies have found that volatile cues from damaged plants can induce resistance to herbivores in undamaged neighbors. However, fewer studies have examined the effects of soilborne cues. Furthermore, there are few studies that have considered the effects of plant-plant communication on plant reproduction. We conducted experiments with tomato se...

Plants exchange a variety of information intra‐ and interspecifically by using various mediating cues. For example, plant individuals that are injured by herbivores release volatile chemicals, which induce receiver plants to express anti‐herbivore resistance. Remarkably, some plant species were known to represent kin specificity in the response, wh...

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sp...

Host–pathogen dynamics are influenced by many factors that vary locally, but models of disease rarely consider dynamics across spatially heterogeneous environments. In addition, theory predicts that dispersal will influence host–pathogen dynamics of populations that are linked, although this has not been examined empirically in natural systems. We...

Many herbivorous insects die of pathogen infections, though the role of plant traits in promoting the persistence of these pathogens as an indirect interaction is poorly understood. We tested whether winter leaf retention of bush lupines (Lupinus arboreus) promotes the persistence of a nucleopolyhedroviruses, thereby increasing the infection risk o...

Vehicle pollution is a pervasive aspect of anthropogenic change across rural and urban habitats. The most common emissions are carbon‐ or nitrogen‐based pollutants that may impact diverse interactions between plants and insect herbivores. However, the effects of vehicle pollution on plant‐insect interactions are poorly understood. Here, we combine...

Premise: Plants are facing increased risk of heat stress with global climate change. Reproductive tissues are particularly heat-sensitive, which can result in lower plant fitness. Floral shading and closure are possible mechanisms to limit heat stress although most previous work on petal orientation has considered adaptations to raise temperatures...

Infectious disease is an important potential driver of population cycles but must occur through delayed density‐dependent infection and resulting fitness effects. Delayed density‐dependent infection by baculoviruses can be caused by environmental persistence of viral occlusion bodies (OBs), which can be influenced by environmental factors. Specific...

Many grasses (Poaceae) defend their basal meristems with silicified trichomes, prickles, and spines. These leaf features are often unidirectional, pointing from the leaf base to the tip. They have been hypothesized to direct small herbivores away from vulnerable meristems, making grasses tolerant of the loss of leaf tissue. The aim of this study wa...

Vehicle pollution is a pervasive aspect of anthropogenic change across rural and urban habitats. The most common emissions are carbon- or nitrogen-based pollutants that may impact diverse interactions between plants and insect herbivores. However, the effects of vehicle pollution on plant-insect interactions are poorly understood. Here, we combine...

Dispersal is a key driver of spatial population dynamics. Dispersal behaviour may be shaped by many factors, such as mate-finding, the spatial distribution of resources, or wind and currents, yet most models of spatial dynamics assume random dispersal. We examined the spatial dynamics of a day-flying moth species ( Arctia virginalis ) that forms ma...

Plant induced defenses may benefit plants by increasing cannibalism among insect herbivores. However, the general efficacy of plant defenses that promote cannibalism remains unclear. Using a generalist Lepidopteran herbivore (Helicoverpa zea), we examined whether plant induced defenses in Solanum lycopersicum increased cannibalism among H. zea and...

Animal biologists have recently focused on individual variation in behavioral traits and have found that individuals of many species have personalities. These are defined as consistent intraspecific differences in behaviors that are repeatable across different situations and stable over time. When animals sense danger, some individuals will alert n...

Dispersal is a key driver of spatial population dynamics. Dispersal behavior may be shaped by many factors, such as mate-finding, the spatial distribution of resources, or wind and currents, yet most models of spatial dynamics assume random dispersal. We examined the spatial dynamics of a day-flying moth species (Arctia virginalis) that forms matin...

Cicadas have amongst the longest development times and are also amongst the largest insects. Cicadas feed exclusively on xylem fluid, which is nutritionally dilute and difficult to obtain. One possible explanation for their slow development is that poor nutrition limits their growth rate. An analysis of 30 cicada species with known development time...

Insect declines have been reported worldwide, although the particular causes of the declines may be complex and are poorly understood. Meadow spittlebugs were one of the most abundant insects in the coastal prairie along the California coast 40 yr ago but have largely disappeared. Evidence links this decline to changing climatic conditions, which h...

Communication occurs when a sender emits a cue perceived by a receiver that changes the receiver's behavior. Plants perceive information regarding light, water, other nutrients, touch, herbivores, pathogens, mycorrhizae, and nitrogen-fixing bacteria. Plants also emit cues perceived by other plants, beneficial microbes, herbivores, enemies of herbiv...

Plant-to-plant volatile-mediated communication and subsequent induced resistance to insect herbivores is common. Less clear is the adaptive significance of these interactions; what selective mechanisms favour plant communication and what conditions allow individuals to benefit by both emitting and responding to cues? We explored the predictions of...

Apart from model organisms, 13- and 17-year periodical cicadas (Hemiptera: Cicadidae: Magicicada) are among the most studied insects in evolution and ecology. They are attractive subjects because they predictably emerge in large numbers; have a complex biogeography shaped by both spatial and temporal isolation; and include three largely sympatric,...

Premise of the study: Ecologists have an incomplete understanding of the factors that select for deciduous, evergreen, and marcescent leaf habits. Evergreens have more opportunities for photosynthesis but may experience costs when abiotic conditions are unfavorable such as during ice and windstorms. Methods: We documented branch loss for species...

The seeds of many plant species produce mucilage on their surfaces that when wetted and dried, firmly adheres seeds to surfaces and substrates. Previous studies have demonstrated that seed anchorage to the ground can reduce seed predation, although only a few species have thus far been tested. Here we investigated whether binding to the ground redu...

Plants can retain either physiologically active green leaves or inactive brown leaves over winter. Research has suggested that leaf retention incurs a cost due to higher herbivore load in the following year; however, no distinction has, thus, far been made between retention of green and brown leaves. We surveyed the over-winter retention of physiol...

The interaction between endogenous dynamics and exogenous environmental variation is central to population dynamics. Although investigations into the effects of changing mean climate are widespread, changing patterns of variation in environmental forcing also affect dynamics in complex ways. Using wavelet and time series analyses, we identify a reg...

Infectious disease is an important potential driver of population cycles, but this must occur through delayed density-dependent infection and resulting fitness effects. Delayed density-dependent infection by baculoviruses can be caused by environmental persistence of viral occlusion bodies, which can be influenced by environmental factors. In parti...

Climate change can affect biotic interactions, and the impacts of climate on biotic interactions may vary across climate gradients. Climate affects biotic interactions through multiple drivers, although few studies have investigated multiple climate drivers in experiments. We examined the effects of experimental watering, warming, and predator acce...

Induced plant responses to herbivory are common, and we have learned a lot about the mechanisms of induced resistance and their effects on herbivore performance. We know less about their effects on herbivore behaviour and especially on spatial patterns of damage. Theoretical models predict that induced responses can cause patterns of damage to beco...

Plants respond to damage by herbivores or to reliable cues of damage by changing in ways that provide greater resistance and increase their fitness. Sagebrush has been a model system for understanding induced resistance, although resistance in this system is commonly assessed by quantifying damage at the end of the season; this measure is slow and...

The risk of consumption is a pervasive aspect of ecology and recent work has focused on synthesis of consumer–resource interactions (e.g., enemy–victim ecology). Despite this, theories pertaining to the timing and magnitude of defenses in animals and plants have largely developed independently. However, both animals and plants share the common dile...

Background and aims: Pendulous flowers (due to a flexible pedicel) are a common, convergent trait of hummingbird-pollinated flowers. However, the role of flexible pedicels remains uncertain despite several functional hypotheses. Here we present and test the "lever-action hypothesis": flexible pedicels allow pendulous flowers to move upwards from a...

Seed mucilage, a coating on seeds or fruit that becomes slimy and sticky when wet, has evolved convergently many times across plants. One common consequence of having seed mucilage is that sand and dirt particles stick to wet seeds and remain tightly bound to the seed surface after the mucilage dries. Here, we test the hypothesis that a mucilage‐bo...

SADIE (Spatial Analysis by Distance Indices) is designed specifically to quantify patterns in spatially-referenced count-based data. It was developed for dealing with data that can be considered ‘patchy’. Such distributions are commonly found, for example, in insect populations where discrete patches of individuals are often evident. The distributi...

1. Plants perceive herbivore damage or increased risk and respond. These changes may increase plant fitness, although effects on fitness have often been assumed without supporting evidence. 2. Three models have been proposed to explain induced rather than constitutive defence. The optimal defence model posits that induction allow plants to reduce a...

Grasses frequently have unidirectional hairs, prickles, and spines; these leaf features have been hypothesized to move herbivores and their chewing damage away from grass meristems, which are located basally. Observations of chewing damage to two grasses, Andropogon virginicus and Phragmites australis, were consistent with this hypothesis as leaf t...

Many plants engage in protective mutualisms, offering resources such as extrafloral nectar and shelters to predatory arthropods in exchange for protection against herbivores. Recent work indicates that sticky plants catch small insects and provide this carrion to predators who defend the plants against herbivores. In this study, we investigated whe...

Context Patch-based population models predominately focus on factors that affect regional processes namely, patch size and connectivity, as the primary drivers explaining patch occupancy. This trend persists despite the recognition that patch quality can strongly influence population demography at the local scale. The quality of patches is often te...

Although many studies have investigated plant growth in the context of episodic herbivory and pressed resource availability, relatively few have examined how plant growth is affected by pulsed resources and chronic herbivory. Periodical cicada (Magicicada spp.) adults represent a pulsed detrital subsidy that fertilizes plants, and live cicada nymph...

Grasses are major agricultural products worldwide and they are critical to ecosystem function in many terrestrial habitats. Despite their global importance, we know relatively little about their defenses against herbivory. Grasses tend to be tolerant of leaf loss because their valuable meristems are located underground, out of reach for above groun...

Recently plant biologists have documented that plants, like animals, engage in many activities that can be considered as behaviors, although plant biologists currently lack a conceptual framework to understand these processes. Borrowing the well‐established framework developed by psychologists, we propose that plant behaviors can be constructively...

Climate change can have strong effects on species interactions and community structure. Temperature‐dependent effects on predator‐prey interactions are a major mechanism through which these effects occur. To understand the net effects of predator attack rates and dynamic windows of prey vulnerability, we examined the impacts of temperature on the i...

1. Abrasive material in the diet of herbivorous organisms comes from a variety of sources, including crystalline silica or calcium in plant tissues, accidentally ingested soil while digging or grazing, and entrapped substrate on the surfaces of plants. A wide variety of plants entrap substrate, usually with glandular trichomes. 2. A previous study...

Erebidae lek mate selection spatially structured populations 'Hilltopping' is a common mate-locating behaviour exhibited by numerous insect taxa; individuals aggregate on summits, ridges and other topographic features, and thereby increase their likelihood of mating. Recently, hilltopping has gained interest as a model system to study nonrandom dis...

Climate is widely recognized as an important factor that affects temporal and spatial patterns of occurrence and abundance of herbivorous insects, although the ecological mechanisms responsible are poorly understood. We found that precipitation and standing water were positively correlated with locations and years of high abundance of caterpillars...

Models of climate change predict more variable precipitation for much of western North America, including more severe multi-year droughts. Droughts are known to increase mortality to trees although less is known about effects on shrubs from arid environments and about effects on reproduction. In this study, we followed a cohort of young sagebrush p...

Plants commonly respond to reliable cues about herbivores by inducing greater defenses. Defenses are assumed to incur costs for plants when they are not needed. Sagebrush responds to volatile cues from experimentally clipped neighbors to induce resistance against chewing herbivores. Rather than experiencing costs, sagebrush seedlings that responded...

Anti-herbivore defense shows high levels of both inter- and intraspecific variability. Defending against herbivores may be costly to the plant when it requires a trade-off in allocation between defense and other missed opportunities, such as reproduction. Indeed, the plastic expression of defensive traits allows the plant to invest resources in def...

Habitat-forming species provide refuges for a variety of associating species; these refuges may mediate interactions between species differently depending on the functional traits of the habitat-forming species. We investigated refuge provisioning by plants with different functional traits for dragonfly and damselfly (Odonata: Anisoptera and Zygopt...

The performance and population dynamics of insect herbivores depend on the nutritive and defensive traits of their host plants(1). The literature on plant-herbivore interactions focuses on plant trait means(2,3,4), but recent studies showing the importance of plant genetic diversity for herbivores suggest that plant trait variance may be equally im...

Plants respond to volatile cues emitted by damaged neighbors to increase their defenses against herbivores. We examined whether plants communicated more effectively with local neighbors than distant neighbors in a reciprocal experiment at two sites. Three branches on focal plants were incubated with air from: 1) a control, 2) an experimentally clip...

Plants that are damaged by herbivores emit complex blends of volatile compounds that often cause neighboring branches to induce resistance. Experimentally clipped sagebrush foliage emits volatiles that neighboring individuals recognize and respond to. These volatiles vary among individuals within a population. Two distinct types are most common wit...

Most ecologists and evolutionary biologists practice natural history, whether in the lab, field or greenhouse. This information generally does not get disseminated, especially in the short form journals that are increasing in popularity. We propose that papers include a natural history supplement to present data and observations which would otherwi...

Plants can respond to insect herbivory in various ways to avoid reductions in fitness. However, the effect of herbivory on plant performance can vary depending on the seasonal timing of herbivory. We investigated the effects of the seasonal timing of herbivory on the performance of sagebrush (Artemisia tridentata). Sagebrush is known to induce syst...

Sand entrapment on plant surfaces, termed psammophory or sand armor, is a phylogenetically and geographically widespread trait. The functional significance of this phenomenon has been poorly investigated. Sand and soil are nonnutritive and difficult for herbivores to process, as well as visually identical to the background. We experimentally invest...

Sand entrapment on plant surfaces, termed psammophory or sand armor, is a phylogenetically and geographically widespread trait. The functional significance of this phenomenon has been poorly investigated. Sand and soil are nonnutritive and difficult for herbivores to process, as well as visually identical to the background. We experimentally invest...

When plants receive volatiles from a damaged plant, the receivers become more resistant to herbivory. This phenomenon has been reported in many plant species and called plant-plant communication. Lab experiments have suggested that several compounds may be functioning as airborne signals. The objective of this study is to identify potential airborn...

Despite the ubiquity of ontogenetic niche shifts, their drivers and consequences are poorly understood. Different nutritional requirements and stage-specific physiological limitations have often been offered as explanations for these life history features, but emerging work has demonstrated that top-down factors may also be important. We studied th...

Background/Question/Methods Much of the theoretical and empirical research on plant-herbivore interactions has focused on the influence of mean plant defensive and nutritional phenotypes on herbivore performance. However, plant traits often vary in space and time, at scales ranging from individuals to populations, and the consequences of this varia...

1. Climate and, therefore, abiotic conditions, are changing rapidly, and many ecological interactions depend on them. In this study, how abiotic conditions mediate a predator–prey interaction were examined. 2. Caterpillars of Platyprepia virginalis (Boisduval) ( A rctiidae) were found previously to be more abundant in wet habitats and thick litter...

Herbivores can greatly reduce plant fitness. Error management theory (EMT) predicts the evolution of adaptive plant defensive strategies that err towards making less-costly errors so as to avoid making rare, costly errors. EMT provides a common framework for understanding observed levels of variation in plant defense among and within species. Copyr...

1. Plant–plant communication has been found to affect interactions between herbivores and plants in several model systems. In these systems, herbivore‐induced volatile chemical cues are emitted and perceived by other plants (receivers), which subsequently change their defensive phenotypes. Most studies have focused on how the effects of volatile cu...

Volatile communication between sagebrush ( A rtemisia tridentata ) individuals has been found previously to reduce herbivory and to be more effective between individuals that are genetically identical or related relative to between strangers. The chemical nature of the cues involved in volatile communication remains unknown for this and other syste...

Periodical cicadas (Magicicada spp.) mature in 13 or 17 years, the longest development times for any non-diapausing insects. Selection may favor prolonged development since nymphs experience little mortality and individuals taking 17 years have been shown to have greater fecundity than those taking 13 years. Why don't periodical cicadas take even l...

Trichomes are an important physical resistance mechanism of plants, as they reduce insect herbivore movement, feeding, and digestion. However, we know little about how trichomes influence herbivore distributions and populations. We conducted laboratory and field experiments to evaluate the preferences of Platyprepia virginalis (Boisduval) (Lepidopt...

Summary There is substantial evidence that the rate of litter decomposition is affected by the match between the litter substrate and the soil matrix (decomposer community). We introduce and test the phenology–substrate-match hypothesis, which predicts that both litter composition and soil matrix will change over the course of the year and that a...

As human-aided range expansions and climate change alter the distributions of plants and their herbivores, predicting and addressing novel species interactions will become increasingly pressing for community ecologists. In this context, a key, surprisingly understudied question is: when an exotic plant is introduced, which herbivores will adopt thi...

Volatile communication between plants causing enhanced defence has been controversial. Early studies were not replicated, and influential reviews questioned the validity of the phenomenon. We collected 48 well-replicated studies and found overall support for the hypothesis that resistance increased for individuals with damaged neighbours. Laborator...

The tritrophic model featuring plants consumed by herbivores consumed by parasitoids or predators has become the primary paradigm used to describe herbivore dynamics. However, interactions involving herbivores can be habitat‐ specific and plants often provide habitat, as well as food. Structural complexity of the habitat may favor predators or may...

It is becoming increasingly accepted that plant–plant signals can affect plant defense against herbivores. In a few taxa, both the mechanisms of plant–plant signaling and the ecological consequences are well described. However, the current adaptive explanations for plant–plant signaling rely heavily on many ecological contingencies, such as the beh...

Leaf phenology is important to herbivores, but the timing and extent of leaf drop has not played an important role in our understanding of herbivore interactions with deciduous plants. Using phylogenetic general least squares regression, we compared the phenology of leaves of 55 oak species in a common garden with the abundance of leaf miners on th...

The importance of interplant volatile signaling in plant-herbivore interactions has been a contentious issue for the past 30 years. We revisit willows as the system in which evidence for interplant signaling was originally found, but then questioned. We established three well-replicated experiments with two willow species (Salix exigua and Salix le...

The ability of many animals to recognize kin has allowed them to evolve diverse cooperative behaviours; such ability is less well studied for plants. Many plants, including Artemisia tridentata, have been found to respond to volatile cues emitted by experimentally wounded neighbours to increase levels of resistance to herbivory. We report that this...

Thirteen microsatellite loci for the threatened orange coral, Astroides calycularis have been designed. The polymorphism of these thirteen loci was tested in 24 polyps from different colonies. The results show that the allele numbers for each loci ranged from 2 to 14 (mean Na=5.1), with an average observed heterozygosity of 0.47 (He=0.45). These ne...

Insect herbivores have developed a myriad of strategies to manipulate the defense responses of their host plants. Here we provide evidence that chewing insects differentially alter the oxylipin profiles produced by the two main and competing branches of the plant defensive response pathway, the allene oxide synthase (AOS) and hydroperoxide lyase (H...

Spatial dynamic theories such as source-sink models frequently describe habitat-specific demographies, yet there are surprisingly few field studies that have examined how and why interacting species vary in their dynamics across multiple habitat types. We studied the spatial pattern of interaction between a chewing herbivore and its primary larval...

1. There are now approximately 10 examples of plants that use volatile cues emitted by damaged neighbours to adjust their defences against herbivores. For two of these examples, preliminary evidence suggested that plants may experience net benefits from such eavesdropping, although eavesdropping was uncommon in one case and estimates of plant fitne...

Volatile communication allows plants to coordinate systemic induced resistance against herbivores. The mechanisms responsible and nature of the cues remain poorly understood. It is unknown how plants distinguish between reliable cues and misinformation. Previous experiments in which clipped sagebrush branches were bagged suggested that cues are emi...