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Our understanding of how conifers respond biochemically to multiple simultaneous herbivore attacks is lacking. Eastern hemlock (Tsuga canadensis; ‘hemlock’) is fed on by hemlock woolly adelgid (Adelges tsugae; ‘adelgid’) and by later-instar gypsy moth (Lymantria dispar; ‘gypsy moth’) caterpillars. The adelgid is a stylet-feeding insect that causes a salicylic acid (SA)-linked response in hemlock, and gypsy moth larvae are folivores that presumably cause a jasmonic acid (JA)-linked response. This system presents an opportunity to study how invasive herbivore–herbivore interactions mediated through host biochemical responses. We used a factorial field experiment to challenge chronically adelgid-infested hemlocks with gypsy moth caterpillars. We quantified 17 phytohormones, 26 phenolic and terpene metabolites, and proanthocyanidin, cell wall-bound (CW-bound) phenolic, and lignin contents. Foliage infested with adelgid only accumulated gibberellins and SA; foliage challenged by gypsy moth only accumulated JA phytohormones. Gypsy moth folivory on adelgid-infested foliage reduced the accumulation of JA phytohormones and increased the SA levels. Both herbivores increased CW-bound phenolics and gypsy moth increased lignin content when feeding alone but not when feeding on adelgid-infested foliage. Our study illustrates the importance of understanding the biochemical mechanisms and signaling antagonism underlying tree responses to multiple stresses and of disentangling local and systemic stress signaling in trees.

Mineral micronutrients are critical for basic physiological function, and variable availability of minerals over the landscape can influence foraging decisions. Sodium is essential for nerve function and osmotic balance; however, it can be limiting in some environments, such as those at high elevations. Koalas (Phascolarctos cinereus) living in subalpine regions have been observed eating Eucalyptus mannifera bark, an unusual food choice for a folivore. We hypothesized that sodium may be deficient in leaves at high-elevation sites, and that the bark from trees could be a potential sodium source. We compared the mineral content of eucalypt bark and leaves in 3 areas where koalas chew bark and in leaves of a preferred food tree of koalas, E. viminalis, across a range of elevations. Individual chewed trees were rare compared to non-chewed conspecifics and patchily distributed. Bark from chewed E. mannifera trees had significantly higher concentrations of sodium than plant parts from non-chewed neighboring conspecifics and other Eucalyptus species trees. We also found that E. viminalis foliage had significantly less sodium at higher elevations than lowland populations. We propose that koalas have developed the unusual bark-eating behavior to meet sodium requirements in an otherwise sodium-poor landscape. Given the physiological importance of sodium, behavioral adaptations such as these may be critical to the ability of mammalian herbivores to survive in nutrient-deficient landscapes.

Nasalis larvatus (von Wurmb, 1781), proboscis monkey, is the only member of its genus and is the largest colobine monkey. It has a uniquely large nose in males. It occurs in lowland riverine forests, peat swamps, and mangrove swamps of Borneo. It is a strong swimmer and can swim underwater. A folivore, it lives in single male-multifemale troops or all-male groups, in a multilevel social system. Male dispersal is routine and females commonly transfer among groups. It is listed as “Endangered” by the International Union for Conservation of Nature and Natural Resources and is included in Appendix 1 of the Convention on International Trade in Endangered Species of Wild Fauna and Flora.

Numerous studies have been made of rodent population and community dynamics, especially in arid ecosystems. Most have centered on understanding how total and species-specific densities of rodents change over time. The standing biomass each species contributes also is important to the energy available to the mesocarnivore community. Although density and standing biomass are related, how they might differ and if those differences are of importance to community structure and function have not received much attention. We analyzed 12 years of rodent density and body mass data from the Chihuahuan Desert in northern Mexico. Data were collected yearly in spring and fall from radial livetrapping webs. Total density and biomass changed significantly in a parallel manner from year to year, and both were related to precipitation and percent cover of grass and forbs. Based on density and biomass, the rodent community was dominated by 2 or 3 principal species. However, on a species-specific level, the numerically dominant species was a small-bodied granivore (Chaetodipus nelsoni), and a large-bodied folivore (Neotoma albigula) dominated in biomass. As total density increased, the proportion contributed by dominant species decreased. As total biomass increased, the proportion in the 2 dominant species increased and accounted for approximately 80% of total biomass. Over the 12 years of the study, species distributions based on density showed no directional change. In contrast, biomass of the rodent community gradually concentrated in a single, large-bodied folivore, N. albigula. Although total density and biomass responded similarly to precipitation and plant productivity, considerable differences between these 2 characteristics existed in their species-specific contributions to and changes within the community. The significance of these differences relative to foraging strategies and variable feeding opportunities within the community is discussed.

The process of selecting certain desirable traits for plant breeding may compromise other potentially important traits, such as defences against pests; however, specific phenotypic changes occurring over the course of domestication are unknown for most domesticated plants. Cranberry (Vaccinium macrocarpon) offers a unique opportunity to study such changes: its domestication occurred recently, and we have access to the wild ancestors and intermediate varieties used in past crosses. In order to investigate whether breeding for increased yield and fruit quality traits may indirectly affect anti-herbivore defences, the chemical defences have been examined of five related cranberry varieties that span the history of domestication against a common folivore, the gypsy moth (Lymantria dispar). Direct defences were assessed by measuring the performance of gypsy moth caterpillars and levels of phenolic compounds in leaves, and indirect defences by assaying induced leaf volatile emissions. Our results suggest that breeding in cranberry has compromised plant defences: caterpillars performed best on the derived NJS98-23 (the highest-yielding variety) and its parent Ben Lear. Moreover, NJS98-23 showed reduced induction of volatile sesquiterpenes, and had lower concentrations of the defence-related hormone cis-jasmonic acid (JA) than ancestral varieties. However, induced direct defences were not obviously affected by breeding, as exogenous JA applications reduced caterpillar growth and increased the amounts of phenolics independent of variety. Our results suggest that compromised chemical defences in high-yielding cranberry varieties may lead to greater herbivore damage which, in turn, may require more intensive pesticide control measures. This finding should inform the direction of future breeding programmes.

We studied the feeding ecology of the thin-spined porcupine (Chaetomys subspinosus), a small arboreal rodent endemic to the Atlantic rain forest of Brazil and threatened with extinction. We captured and radiotracked 4 free-ranging individuals and collected 1,177 feeding records in 944 h of observation between April 2005 and September 2006. We found that the animal feeds exclusively on the leaves of woody trees, preferring young leaves. Diet composition and foraging pattern did not vary seasonally, although we observed a seasonal variation in the availability of young leaves. Annual diet comprised primarily (90%) 4 plant species, Albizia pedicellaris, Inga thibaudiana, Pera glabrata, and Tapirira guianensis. This small subset of plant species contains high levels of both leaf protein and fiber, and most preferred species have the capacity to establish symbiotic associations with nitrogen-fixing bacteria. A diet concentrated in a few taxonomically related, nitrogen-fixing species suggests that in a...

Petauroides volans (Kerr, 1792) is a pseudocherid marsupial with the common name greater glider. It is the largest and most conspicuous of the gliding possums and is 1 of the most numerous arboreal marsupials in the eucalypt forests of eastern Australia. Its gliding membranes are large and its thick, shaggy coat obscures the basic body form, making the animal appear much larger than it actually is. P. volans is nocturnal, arboreal, solitary, and folivorous and is dependent on large tree hollows for shelter. In Australia, P. volans has received particular attention because it is highly sensitive to the removal of old hollow-bearing trees during forestry practices such as clear-cutting.

Bradypus variegatus Schinz, 1825 (the brown-throated three-toed sloth), is 1 of 4 extant three-toed sloths. A high-canopy folivore, B. variegatus is distributed over southern Central America and northern and central South America and is listed as Least Concern by the International Union for Conservation of Nature and Natural Resources because of its wide distribution. Males have a middorsal speculum. B. variegatus has a commensal relationship with the algae and invertebrates that live in its thick pelage. It does not adapt well to zoo settings.

Bradypus torquatus Illiger, 1811 is a three-toed sloth commonly called the maned three-toed sloth. It is endemic to the Atlantic coastal forests of southeastern Brazil. Occasionally placed in its own genus (Scaeopus), the black mane of this three-toed sloth is distinctive. Like other sloths, B. torquatus is a high-canopy folivore with a commensal relationship with algae and invertebrates that live in its abundant pelage. B. torquatus is an endangered species that does not adapt to captive zoo settings.

We examined the feeding habits of the Indian giant flying squirrel (Petaurista philippensis) in a rain-forest fragment in southern Western Ghats, India, from December 1999 to March 2000. Flying squirrels consumed 4 major plant parts belonging to 9 plant species. Ficus racemosa was the most-eaten species (68.1%) during the period of the study, followed by Cullenia exarillata (9.57%) and Artocarpus heterophyllus (6.38%). The most commonly consumed food item was the fruit of F. racemosa (48.93%). Leaves formed an important component of the diet (32.97%) and the leaves of F. racemosa were consumed more than those of any other species. Flying squirrels proved to be tolerant of disturbance and exploited food resources at the fragment edge, including exotic planted species.

Food competition is an expected cost of group living. It is therefore puzzling that there is little evidence for competition among group-living folivorous monkeys, for example, daily travel distance does not seem to increase with group size. It is even more puzzling that folivores do not form larger groups despite this apparent lack of food competition. This has become known as the folivore paradox, and to date, there is no broadly accepted theoretical solution. However, there have been no multigroup studies that have controlled for the potentially confounding effects of variation in habitat quality. We studied 9 groups of red colobus monkeys (Procolobus rufomitratus) in Kibale National Park, Uganda, and controlled for spatial and temporal variation in food availability. We found that larger groups occupied larger home ranges than smaller groups and that group size was related to increased foraging effort (longer daily travel distance), increased group spread, and reduced female reproductive success. Our results also suggest that monkeys in larger groups spent more time feeding and less time engaged in social behavior. These results suggest that folivorous red colobus monkeys experience within-group scramble competition and possess a suite of behavioral responses that may mitigate the cost of competition and represent adaptations for group living. The results offer insight into the folivore paradox and the evolutionary ecology of group size. Copyright 2008, Oxford University Press.

A measure of the specific impact for herbivore–plant interactions was used to test whether 7 insect species differ in the severity of their effects on young cruciferous plants. Specific impact was estimated as a biomass conversion ratio (reduction in plant biomass per unit gain in insect biomass) based on dry weights. The armyworm Mamestra configurata (Walker) had a specific impact of 4–5 on both canola, Brassica napus L., and mustard, Sinapis alba L., in the laboratory, and a similar specific impact of 3.4 was estimated for a natural field population. Two herbivore densities showed little if any difference in the specific impact for M. configurata on canola, nor for the flea beetle Phyllotreta striolata (F.), which had impacts of 81 and 96 at the 2 densities tested. The flea beetle Phyllotreta cruciferae (Goeze) had a specific impact of 148 on canola, not significantly different from that of its relative, P. striolata, which feeds in a similar way. The specific impact of the beetle Entomoscelis americana Brown was 3.5, similar to that of M. configurata, and both species had lower specific impacts than another folivore, Plutella xylostella (L.), with an impact of 12. The specific impacts of 2 aphids, Lipaphis erysimi (Kaltenbach) and Myzus persicae (Sulzer), were similar with values of 12 and 16, respectively. Although different herbivores showed substantial differences in their impacts on canola, no consistent pattern of difference was found between herbivores belonging to the leaf-chewing and sap-feeding guilds, nor were there consistent differences between generalist and specialist herbivores.

Outbreaks of folivorous Lepidoptera caterpillars are common in temperate forests (Ives and Wong 1988, Butterworth 1990). The high fat content, low chitin content, and large size of these larvae make them an important component of the diet of many temperate birds (Betts 1955, Robinson and Holmes 1982, Holmes and Schultz 1988, Sample et. al. 1993). Outbreaks of most species should increase available food for breeding birds, improving their reproductive success. Some caterpillars, however, have morphological or chemical defenses that make them unpalatable to avian predators (Heinrich and Collins 1983). During outbreaks, these species have the potential to reduce the abundance of palatable caterpillars through severe defoliation. Previous studies have not considered the effects of outbreaks of unpalatable Lepidoptera species on the breeding biology of birds. This investigation determines the effects of forest tent caterpillar (Malacosoma disstria) outbreaks on the reproductive success of Black-capped Chickadees (Parus atricapillus) near Athabasca, Alberta, Canada. The tent caterpillar is a major defoliator of trembling aspen (Populus tremuloides) in Alberta, undergoing three to five year population outbreaks every five to ten years (Ives and Wong 1988, Butterworth 1990). Egg masses and very early instar larvae can be consumed by avian predators. Thus, for resident bird species, an outbreak of tent caterpillars could increase food supply in winter and early spring prior to and just after hatch of egg masses. Late instar tent caterpillars, however, are equipped with spiny hairs and bristles and are unpalatable to most avian predators (Smith 1991). Thus, outbreaks of tent caterpillars that lead to defoliation during the brood-rearing period may decrease reproductive success for chickadees. Tent caterpillar outbreaks and complete canopy tree defoliation occurred in our study area during 1986 and 1987, while few or no caterpillars and little or no defoliation were evident during 1989-1992. We tested two predictions. First, in years with tent caterpillar outbreaks, initiation of breeding would be earlier and clutch sizes larger in response to extra food when compared to years with no outbreaks. Second, tent caterpillar defoliation would reduce the reproductive success and subsequent survival of female Black-capped Chicka ees through food limitation during brood-rearing.

Lamponius portoricensis Rhen is a folivorous neotropical walkingstick that is a common light-gap inhabitant of the tabonuco forest in Puerto Rico. Little is known concerning the spatial distribution of this phasmatid or the manner in which it selects habitats. Based on multiple regression analysis of a suite of taxonomic and structural characteristics of understory flora, we determined that the density of walkingsticks was associated with patches that exhibit high apparency values for Piper treleaseanum Britton Wilson and Symplocos martinicensis Jacq., and low apparency values for Dryopteris deltoidea (Sw.) Kuntze. The total development of the understory regardless of taxonomic composition at 76 cm (2.5 ft) and 107 cm (3.5 ft) also contributes to high walkingstick density, based on correlative analyses. Moreover, nonparametric analysis suggests that L. portoricensis disproportionately occurs on P. treleaseanum (approximately twice as often as expected based on plant apparency). Despite these associations, only a third of the variation in walkingstick density is accounted for by this suite of floral characteristics. The low vagility of L. portoricensis may result in its having incomplete information about the abundance and distribution of forage plants, whereas patch-dynamic processes involving changes in quality of forage can confound the significance of apparency alone inmore » predicting density. The production of aromatic attractants by Piper may act as the proximate cue affecting patch selection.« less

Kerodon rupestris , a folivorous rodent endemic to the Caatinga of Brazil, exhibits complex modifications of diet in response to changes in the absolute abundance of 10 food species when their relative abundances remain equal. We evaluated the correlation between a suite of 12 nutrients (energy, ash, carbon, nitrogen, phosphorous, sulphur, zinc, manganese, calcium, magnesium, potassium, and sodium) and the consumption of leaves from 10 different plant species. Regardless of the taxonomic composition of the diet, the proportional representation of all nutrients but sodium was constant during phases of low and high abundance of foods. The uptake of sodium increased by a factor of 2.84, even though total consumption increased only by a factor of 2.04. From multiple stepwise-regression analysis, we suggest that nitrogen, calcium, and potassium contributed significantly to food selection. Carbon and sodium also were correlated with consumption, but excluded from the multiple-regression results because of their intercorrelation with other nutrients. The median-log Levene's test was significant, indicating differences in the relative variation in uptake of the 12 nutrients. At high abundance of resources, sodium exhibited the most consistent daily uptake of all the nutrients, suggesting that it may constrain the maximization of other essential dietary elements. Sodium may play a role in the water balance of this arid-land rodent.

Statistical associations were sought between relative brain size and arboreality, diet, habitat, sociality, and reproductive effort among 33 species of North American sciurids. When using all 33 species, arboreality (species classified as arboreal or terrestrial) was found to be a better predictor of brain size compared to diet (folivore or other) or habitat (grassland or other). Arboreal squirrels had significantly larger brains for their body size than did terrestrial squirrels. No relationship was found between relative brain size and reproductive effort. Within the terrestrial squirrels, no relationships were found between brain size and diet, habitat, or sociality (social or asocial). Although these analyses showed that arboreal squirrels had larger brains than did terrestrial squirrels, it is not clear whether this difference is due to (1) selection for large brains in arboreal species, or (2) small brains in terrestrial squirrels as a result of selection for rapid growth rates of young.