Herbivore Consumption Research Articles

Shrouded in history: Unveiling the ways of life of an early Muslim population in Santarém, Portugal (8th- 10th century AD).

In around 716 AD, the city of Santarém, Portugal, was conquered by the Berber and Arab armies that swept the Iberian Peninsula and went on to rule the region until the 12th century. Archaeological excavations in 2007/08 discovered an Islamic necropolis (Avenida 5 de Outubro #2-8) that appears to contain the remains of an early Muslim population in Santarém (8th- 10th century). In this study, skeletal material from 58 adult individuals was analysed for stable carbon (δ13Ccol; δ13Cap), nitrogen (δ15N) and sulphur (δ34S) isotope ratios in bones, and stable oxygen (δ18O), carbon (δ13Cen) and radiogenic strontium (87Sr/86Sr) isotopes in tooth enamel. The results of this study revealed a dietary pattern of predominantly C3-plant and domestic C3-fed herbivore consumption during adulthood (δ13Ccol and δ15N, respectively) but a higher proportion of C4-plant input during childhood (δ13Cen) for some individuals-interpreted as possible childhood consumption of millet porridge, a common practice in North Africa-in those with unorthodox burial types (Groups 1 and 2) that was not practiced in the individuals with canonical burials (Group 3). In this first mobility study of a medieval Muslim population in Portugal, δ18ODW values revealed greater heterogeneity in Groups 1 and 2, consistent with diverse origins, some in more humid regions than Santarém when compared to regional precipitation δ18O data, contrasting the more homogenous Group 3, consistent with the local precipitation δ18O range. Ancient DNA analysis conducted on three individuals revealed maternal (mtDNA) and paternal (Y-chromosome) lineages compatible with a North African origin for (at least) some of the individuals. Additionally, mobility of females in this population was higher than males, potentially resulting from a patrilocal social system, practiced in Berber and Arab communities. These results serve to offer a more detailed insight into the ancestry and cultural practices of early Muslim populations in Iberia.

Warming alters the top–down effect of a common mesopredator in an aquatic food web

Global warming is altering the composition and functioning of both terrestrial and aquatic ecosystems. Most research has focussed on direct effects of warming on species and their population dynamics, while less is known about indirect effects through species interactions. Trophic cascades are especially likely to influence the effects of warming given that trophic levels differ in their response to warming because of differences in metabolism and vital rates such as growth and reproduction. We investigated if the top–down effect of a common mesopredator, the threespine stickleback, alters the impact of warming on a Baltic Sea food web. We manipulated both temperature and the presence of stickleback in mesocosms, and found the stickleback to alter the impact of warming on lower trophic levels. This was through increased consumption of herbivores that exceeded the rate at which the herbivore population could grow under higher temperature, which in turn increased algae biomass compared to a scenario without stickleback, but not compared to conditions under normal temperature. Thus, the mesopredator increased the transfer of biomass to higher trophic levels of the food web when temperature was increased. This stresses the importance of considering the impact of warming on multiple trophic levels and their interactions. Failing to consider differences in responses among trophic levels and the impact this has on their interactions can result in faulty conclusions about the impact of warming on ecosystems.

Late‐Quaternary megafauna extinctions have strongly reduced mammalian vegetation consumption

AbstractAimHow much stronger would the effects of herbivorous mammals be in natural ecosystems if human‐linked extinctions and extirpations had not occurred? Many mammal species have experienced range contractions, and numerous species have gone extinct in the late Quaternary, completely or in large part linked to human pressures. Therefore, herbivore consumption rates in seemingly natural ecosystems will deviate from their pre‐anthropogenic state. Here, we estimate the size of this deviation.LocationTerrestrial systems, globally.Time periodCurrent.Major taxa studiedAll late‐Quaternary terrestrial mammals.MethodsWe estimated and mapped vegetation consumption rate by all late‐Quaternary terrestrial mammals. We did this through the estimation of natural densities and dietary needs. We mapped their consumption rate in both current ranges and present‐natural ranges, that is estimated ranges in the absence of human‐linked range contractions and extinctions. We compared these estimated consumption rates to current net primary productivity (NPP). We summarized the results across ecosystem types everywhere as well as for only the last remaining wilderness areas.ResultsWe estimate that wild mammals consume a median of 11% of NPP (at the scale of 96.5 km × 96.5 km grid cells) in current natural areas and that this would have been much higher in the absence of extinctions and extirpations, namely 21%. Looking at the change per grid cell, the mammal losses result in a median 42% reduction in consumption rate. Importantly, we estimate very similar declines in herbivory in what are considered the last remaining wilderness areas.Main conclusionsOur results suggest that the natural interaction of mammalian herbivores with vegetation in ecosystems across the world is strongly reduced by prehistoric and historic to recent species losses, even in the last remaining wilderness areas, likely with major effects on ecosystem structure and functioning.

Large herbivore impact on plant biomass along multiple resource gradients in the Serengeti

Abstract Herbivores form an important link in the transfer of energy within a food web and are strongly influenced by bottom‐up trophic cascades. Current hypotheses suggest that herbivore consumption and impact on plants should scale positively with plant resource availability. However, depending on the effect of resources on plant quantity and quality, herbivore impact may vary with different types of resources. We test four alternative hypotheses for the relationship between plant biomass, herbivore impact on plant biomass and plant resource gradients, each based on how resources might affect plant abundance and quality to herbivores. We measured plant biomass for four non‐consecutive years in a long‐term grazing exclosure experiment in the Serengeti National Park that includes seven sites that vary substantially in rainfall and soil and plant nitrogen (N) and phosphorus (P). Our data supported the hypothesis that herbivore impact is controlled by plant quality, in this case driven by plant P, as herbivore effects on biomass decreased with higher rainfall but increased with greater plant P, but not N content. To our knowledge, this is the first experimental study to indicate that wild mammalian herbivory is associated with P availability rather than N. Synthesis. Our results suggest that P, in addition to water and N, may play a more important role in driving trophic interactions in terrestrial systems than previously realized. Given the uncertainties in rainfall due to climate change and increasing anthropogenic manipulations of global N and P cycles, our findings emphasize the need to consider multiple resources for understanding how trophic interactions might be influenced by environmental variables.

Altered structure of bat–prey interaction networks in logged tropical forests revealed by metabarcoding

Habitat degradation is pervasive across the tropics and is particularly acute in Southeast Asia, with major implications for biodiversity. Much research has addressed the impact of degradation on species diversity; however, little is known about how ecological interactions are altered, including those that constitute important ecosystem functions such as consumption of herbivores. To examine how rainforest degradation alters trophic interaction networks, we applied DNA metabarcoding to construct interaction networks linking forest-dwelling insectivorous bat species and their prey, comparing old-growth forest and forest degraded by logging in Sabah, Borneo. Individual bats in logged rainforest consumed a lower richness of prey than those in old-growth forest. As a result, interaction networks in logged forests had a less nested structure. These network structures were associated with reduced network redundancy and thus increased vulnerability to perturbations in logged forests. Our results show how ecological interactions change between old-growth and logged forests, with potentially negative implications for ecosystem function and network stability.

Open space, not reduced herbivory, facilitates invasion of a marine macroalga, implying it is a disturbance-mediated “passenger” of change

Sargassum horneri, a brown macroalga, recently invaded the California coast, including into critical foundational communities such as kelp (Macrocystis pyrifera) forests. Despite its rapid spread, empirical tests that evaluate mechanisms underlying S. horneri's invasion success are lacking. To fill this knowledge gap, we conducted three field experiments on temperate rocky reefs in southern California using growth as a proxy for invasion success. We first tested whether S. horneri success differed with herbivory strength and native diversity by conducting a 2-factor experiment varying site (with different baseline levels of urchin densities and native algal diversity) and urchin access. We found S. horneri growth only differed among urchin treatments and not sites. We then evaluated whether S. horneri could successfully invade established algal canopies as a driver or whether it required open space as a passenger via a 2-factor experiment varying S. horneri size (small, medium, large) and canopy type (S. horneri, kelp, -canopy). We found that all S. horneri sizes grew fastest when canopy was lacking and light was high and slower in both canopy habitats with lower light; overall, small S. horneri grew slowest. Finally, we evaluated whether herbivore consumption for native species could facilitate S. horneri's invasion by conducting a 2-factor experiment varying species (M. pyrifera, S. horneri) and herbivore access. We found uncaged algae were consumed and caged algae grew, but there was no difference between species. Taken together, our results suggest that S. horneri is a “passenger” invader that will take advantage of points in time and space where light is plentiful, such as when M. pyrifera is removed via disturbance. Further, our results suggest that herbivory and native algal diversity are likely not key determining factors of the invasion success of S. horneri.

Predation services: quantifying societal effects of predators and their prey

Conservation of predators – especially large carnivores and those that potentially pose threats to humans – can be controversial among stakeholders who must coexist with them. What is often overlooked, however, are the direct and indirect ecosystem services and disservices predators provide as a result of consumption of herbivores (“predation services”). We used a theoretical predator–prey–economic model to examine when predators are likely to provide a net service to society, by comparing services/disservices to a predator‐free counterfactual scenario. We found that net predator services were strongly dependent on how per‐capita services and disservices of predators and prey changed with abundance (ie assumed marginal value [MV] functions of service/disservice). We suggest that further empirical research is needed into MVs of services/disservices of wildlife, because transferring net services among locations – a common practice – is problematic unless MV functions are known. Rigorously quantifying services/disservices of predators could improve conservation and management outcomes by increasing effective communication to diverse stakeholders.

Forest Thinning in Ponderosa Pines Increases Carbon Use Efficiency and Energy Flow From Primary Producers to Primary Consumers

AbstractA better understanding of carbon use efficiency (CUE) and carbon allocation during disturbance is critical to improve simulations of the global carbon cycle and understanding future climate impacts. Forest thinning of high‐stem density, high elevation dry western US forests is becoming more common to reduce severe fire danger but there are uncertainties about how forest thinning may impact forest CUE, carbon allocation and energy flow through the food chain. In three, quarter ha stands with similar soils, elevation and climate along a forest thinning gradient near Flagstaff (AZ), we measured total net primary production (NPP of wood, fine root, and leaves), total autotrophic respiration (Ra of wood, rhizosphere, and canopy respiration), gross primary production (GPP = NPP + Ra) and large mammal herbivory (with camera traps and dung counts) over a ∼2‐year period. We found strong seasonality in all carbon cycling variables and herbivory, peaking during the warm, wet monsoon period. Carbon was produced more efficiently in the thinned stands, with carbon use efficiency (CUE = NPP/GPP) of ∼0.63, versus the unthinned stand with CUE of 0.38. GPP was similar in the two thinned stands (∼3.5 Mg C ha−1 yr−1) but was about 30% greater in the unthinned stands (5.0 Mg C ha−1 yr−1). Finally, the thinned stand had higher understory NPP, large herbivore consumption and had triple the total energy going into primary consumers. Overall, the thinning, and the return to a more natural prefire suppression forest structure, increased the CUE and energy flow from primary producers to primary consumers.

Remote sensing of trophic cascades: multi‐temporal landsat imagery reveals vegetation change driven by the removal of an apex predator

Trophic cascade theory predicts that predators indirectly benefit plants by limiting herbivore consumption. As humans have removed large predators from most terrestrial ecosystems the effect of their absence is unrecognized. A manipulation of dingo populations across Australia’s dingo-proof fence, within the Strzelecki Desert, was used to assess how predator absence has altered vegetation cover dynamics at landscape and site scales. Landscape-scale analysis used Landsat fractional vegetation cover time series statistics to classify landforms and examine vegetation dynamics either side of the dingo fence. Generalised additive models were used to analyse the influence of predator absence on site-scale observations of fauna abundance and vegetation cover. The location of the dingo fence was visible as a change in both the standard deviation and maximum of non-photosynthetic vegetation (NPV) cover (e.g. wood and dry leaves) over 32 years (1988–2020). On average, NPV cover of swales decreased in the standard deviation by 1.4% and in the maximum by 5.0% where dingo abundance was reduced. The differences were consistent with suppressed vegetation growth following rainfall, due to high grazing pressure, where predators were rare. The landscape-scale analysis was supported by site-scale observations. The influence of the trophic cascade was observable at both the landscape and site scales, suggesting that apex predator removal has significantly affected the arid ecosystem’s responses to resource pulses. Analogous effects may exist across the large areas of the planet over which apex predators have been extirpated.

Nutrient enrichment stimulates herbivory and alters epibiont assemblages at the edge but not inside subtidal macroalgal forests

Nutrient enrichment is a major threat to subtidal macroalgal forests. Several studies have shown that nutrient inputs can enhance the ability of opportunistic algal species to acquire space freed by disturbance, at the expense of architecturally complex species that form forests. However, competition between canopy- and turf-forming macroalgae is not limited to the aftermath of disturbance. Canopy-forming macroalgae can provide suitable substratum for diverse epibiont assemblages, including both algae (epiphytes) and sessile invertebrates (epizoans). Despite evidence of enhanced epiphyte loading under eutrophic conditions, few experimental studies have assessed how nutrient enrichment influences the structure of epibiont assemblages on canopy-forming macroalgae at the edge versus inside forests. In oligotrophic waters of the NW Mediterranean, we experimentally tested the hypothesis that nutrient-driven proliferation of opportunistic epiphytic algae would affect the performance of the fucoid, Carpodesmia brachycarpa, and reduce the richness and abundance of the epizoan species they support. We predicted negative effects of nutrient enrichment to be greater at the edge than inside forests and on thalli that had recovered in cleared areas than on those within undisturbed canopy stands. Nutrient enrichment did not affect the photosynthetic efficiency and reproductive output of C. brachycarpa. By contrast, it enhanced herbivore consumption and decreased the cover and diversity of epizoans at forest edges, likely by stimulating the foraging activity of Arbacia lixula, the most abundant sea urchin in adjacent encrusting coralline barrens. Fertilization of areas inside forests had no effect on either C. brachycarpa or epibiont assemblages. Finally, nutrient enrichment effects did not vary between cleared and undisturbed areas. Our results show that moderate nutrient enrichment of oligotrophic waters does not necessarily cause the proliferation of epiphytes and, hence, a strengthening of their competitive effects on canopy-forming macroalgae. Nevertheless, enhanced herbivory damage to fertilized thalli at forest edges suggests that fragmentation could reduce the resilience of macroalgal forests and associated epibiont assemblages to nutrient enrichment.

Herbivory in Seagrass Meadows: an Evolving Paradigm

In the past few decades, we have learned much about the factors that regulate the productivity of seagrass-dominated ecosystems, especially those at low latitudes. Here, we update our previous assessments of the importance of seagrass-herbivore interactions, focusing on recent studies that have examined (1) the diversity of herbivores feeding on live seagrass leaves; (2) the factors that determine the ability of seagrasses to respond to herbivore damage; (3) how potential chemical deterrents, and structural defenses, in seagrass leaves influence herbivore consumption; (4) how climate-driven changes in herbivore identity might change grazing intensity in temperate seagrasses; (5) the effects of herbivory on pollen, flowers, fruits, and seeds of seagrasses; and (6) the effects of human removal of seagrass megaherbivores and the top-down effects of overfishing top predators on seagrass consumption. We also identify important gaps in our understanding of the broadly defined topic of herbivory in seagrass-dominated ecosystems. Specifically, we suggest that future studies should consider focusing on increasing our understanding of herbivore foraging strategies, quantifying the impact of herbivory on seagrass reproductive biology, including effects on the fates of flowers, fruits, and seeds and documenting the commonness of compensatory responses and chemical defenses to grazing. Studies of the roles of the nutritional content (as measured by C/N/P ratios), in determining herbivore feeding preferences, remain fertile grounds for future studies, as do additional experiments to quantify the relative roles of top-down and bottom-up factors in determining seagrass abundance and energy fluxes in seagrass meadows.

Temperature dependency of predation: Increased killing rates and prey mass consumption by predators with warming.

Temperature dependency of consumer–resource interactions is fundamentally important for understanding and predicting the responses of food webs to climate change. Previous studies have shown temperature‐driven shifts in herbivore consumption rates and resource preference, but these effects remain poorly understood for predatory arthropods. Here, we investigate how predator killing rates, prey mass consumption, and macronutrient intake respond to increased temperatures using a laboratory and a field reciprocal transplant experiment. Ectothermic predators, wolf spiders (Pardosa sp.), in the lab experiment, were exposed to increased temperatures and different prey macronutrient content (high lipid/low protein and low lipid/high protein) to assess changes in their killing rates and nutritional demands. Additionally, we investigate prey mass and lipid consumption by spiders under contrasting temperatures, along an elevation gradient. We used a field reciprocal transplant experiment between low (420 masl; 26°C) and high (2,100 masl; 15°C) elevations in the Ecuadorian Andes, using wild populations of two common orb‐weaver spider species (Leucauge sp. and Cyclosa sp.) present along the elevation gradient. We found that killing rates of wolf spiders increased with warmer temperatures but were not significantly affected by prey macronutrient content, although spiders consumed significantly more lipids from lipid‐rich prey. The field reciprocal transplant experiment showed no consistent predator responses to changes in temperature along the elevational gradient. Transplanting Cyclosa sp. spiders to low‐ or high‐elevation sites did not affect their prey mass or lipid consumption rate, whereas Leucauge sp. individuals increased prey mass consumption when transplanted from the high to the low warm elevation. Our findings show that increases in temperature intensify predator killing rates, prey consumption, and lipid intake, but the responses to temperature vary between species, which may be a result of species‐specific differences in their hunting behavior and sensitivity to temperature.

Age-related variation in the trophic characteristics of a marsupial carnivore, the Tasmanian devil Sarcophilus harrisii.

Age‐related changes in diet have implications for competitive interactions and for predator–prey dynamics, affecting individuals and groups at different life stages. To quantify patterns of variation and ontogenetic change in the diets of Tasmanian devils Sarcophilus harrisii, a threatened marsupial carnivore, we analyzed variation in the stable isotope composition of whisker tissue samples taken from 91 individual devils from Wilmot, Tasmania from December 2014 to February 2017. Both δ13C and δ15N decreased with increasing age in weaned Tasmanian devils, indicating that as they age devils rely less on small mammals and birds, and more on large herbivores. Devils <12 months old had broader group isotopic niches, as estimated by Bayesian standard ellipses (SEAB mode = 1.042) than devils from 12 to 23 months old (mode = 0.541) and devils ≥24 months old (mode = 0.532). Devils <24 months old had broader individual isotopic niches (SEAB mode range 0.492–1.083) than devils ≥24 months old (mode range 0.092–0.240). A decrease in δ15N from the older whisker sections to the more recently grown sections in devils <24 months old likely reflects the period of weaning in this species, as this pattern was not observed in devils ≥24 months old. Our data reveal changes in the isotopic composition of devil whiskers with increasing age, accompanied by a reduction in isotopic variation both among population age classes and within individuals, reflecting the effect of weaning in early life, and a likely shift from an initially diverse diet of small mammals, birds, and invertebrates towards increasing consumption of larger herbivores in adulthood.

Diet of autochthonous populations in Yakutia using isotopic, ethnographic, historical and archaeological data

This article investigates, for the first time, the diet of the Yakut population between the 15th and 19th centuries AD. Analyses of the stable isotopes of carbon and nitrogen in human and animal bone collagen were used for the study. The stable isotope values were then compared through four historical periods, three geographical areas, sexes, and socio-economic groups determined by the presence or absence of artefacts in the excavated tombs. The results highlight the variety of dietary practices among the Yakuts. There are significant differences between the North, characterised mostly by the consumption of herbivores, the Viluy region, where fish had an important role, and Central Yakutia with a diversified diet. No differences were seen between the diets of men and women. The group of elites had a stable diet based on meat and milk consumption. Samples before 1700AD had δ15N values that were higher than samples from other periods, probably due to greater consumption of fish and foal meat. These data were compared with ethnographic, historical and archaeological information so as to better depict the diet of these past populations.

Evaluación del efecto del pastoreo con bovinos como herramienta de control de ligustro (Ligustrum lucidum) en bosque parque

de Santiago, F., Bresciano, D., Del Pino, L., Castagna, A., Blumetto, O. 2019. Evaluation of the effect of grazing with bovines as a control tool for privet (Ligustrum lucidum) in park forest. Ecosistemas 28(2): 109-115. Doi.: 10.7818/ECOS.1673 Invasive alien species constitute one of the most important threats to the conservation of biodiversity and ecosystem processes. A specie that stound out In Uruguay and other temperate zones, is the privet (Ligustrum lucidum W.T. Aiton); an Asian species with great adaptability and characteristics that make it a successful colonizer. Seeds production is its main reproductive strategy, so the herbivore consumption could contribute to reduce the recruitment of seedlings. The objective of this work was to evaluate the use of bovine grazing as a tool to reduce the progress of this species in park forest ecosystems. An experiment was carried out at Las Brujas Experimental Station, of the National Institute of Agricultural Research (INIA), Uruguay. The experimental area consisted of 4 paddocks assigned to two treatments of different intensities of cows grazing (initial allowance of 5 kg and 3 kg of grass dry matter / kg of animal body weight). During winter and spring 2016 and summer 2017, six plots of 1 m2 were sampled in each paddock. In each sampling station, the total number of plants, height, number of leaves, presence of apical bud and presence of other buds were recorded. Although there was no negative effect on the final number of plants, there was defoliation and cut of buds due to the effect of grazing, which could have a retarding effect on growth. The treatment with higher grazing intensity had more apical buds cutting, but, in both cases, the sprouts were grazed. Grazing, under these conditions, did not result in an effective tool for privet control. However, it is worthwhile to go deeper into studies where grazing pressure is maintained during longer periods of time.

Exceptionally high δ15N values in collagen single amino acids confirm Neandertals as high-trophic level carnivores

Isotope and archeological analyses of Paleolithic food webs have suggested that Neandertal subsistence relied mainly on the consumption of large herbivores. This conclusion was primarily based on elevated nitrogen isotope ratios in Neandertal bone collagen and has been significantly debated. This discussion relies on the observation that similar high nitrogen isotopes values could also be the result of the consumption of mammoths, young animals, putrid meat, cooked food, freshwater fish, carnivores, or mushrooms. Recently, compound-specific C and N isotope analyses of bone collagen amino acids have been demonstrated to add significantly more information about trophic levels and aquatic food consumption. We undertook single amino acid C and N isotope analysis on two Neandertals, which were characterized by exceptionally high N isotope ratios in their bulk bone or tooth collagen. We report here both C and N isotope ratios on single amino acids of collagen samples for these two Neandertals and associated fauna. The samples come from two sites dating to the Middle to Upper Paleolithic transition period (Les Cottés and Grotte du Renne, France). Our results reinforce the interpretation of Neandertal dietary adaptations as successful top-level carnivores, even after the arrival of modern humans in Europe. They also demonstrate that high δ15N values of bone collagen can solely be explained by mammal meat consumption, as supported by archeological and zooarcheological evidence, without necessarily invoking explanations including the processing of food (cooking, fermenting), the consumption of mammoths or young mammals, or additional (freshwater fish, mushrooms) dietary protein sources.

Dogs in funerary contexts during the Middle Neolithic in the northeastern Iberian Peninsula (5th–early 4th millennium BCE)

In this article, a zooarchaeological and isotopic analysis is presented for 26 dog exemplars (Canis familiaris). These dogs were deposited in burial and ceremonial structures in the northeastern Iberian Peninsula during the Middle Neolithic, within the Pit Grave cultural horizon (ca. 4200–3600 cal BC). Four archaeological sites of the Catalonian coastal strip are studied: Camí de Can Grau, La Serreta, Ca l'Arnella, and Bòbila Madurell (one of the most important necropolises of the Iberian Peninsula). The presence of these dogs is interpreted as evidence of accompanying offerings and represents the most ancient use of this animal in the context of burials within the studied territory. Although it is a not a globally recorded gesture during this period, in light of the present results, it can be considered as a stereotyped ritual activity and evidence of the close relationship between these animals and the human communities. The diet of most of the dogs must be considered mixed and very similar to that of the humans, including consumption of herbivores and terrestrial plants.

Geographic patterns of plant–herbivore interactions are driven by soil fertility

Abstract Aims Geographic patterns of the intensity of plant herbivory in relation to climate factors have garnered little general support and appear to be species specific. However, plant–herbivore interactions are also driven by resource availability, such as soil nutrient content, and it remains unclear whether broad-scale variation in soil factors is reflected in herbivore consumption rates across species’ ranges. Additionally, we know little of how intraspecific variation in tissue quality associates with edaphic and climatic factors, and how this variation controls herbivore consumption. The resource availability hypothesis (RAH) predicts that plant individuals growing in low-resource environments will have lower leaf nutritional quality and more constitutive defenses, which will result in lower rates of leaf consumption. Methods We collected leaves from the old-field dominant species, Solidago altissima L., from 20 sites across 10 degrees of latitude in the Eastern USA to determine the percentage leaf area consumed by insect folivores. We obtained soil and climate data for each site, as well as plant functional and defensive traits, including specific leaf area (SLA), leaf carbon:nitrogen (C:N), and trichome density. Important Findings Although we found no significant latitudinal trend of leaf consumption rate, there was strong evidence that leaf herbivory decreased with leaf C:N and trichome density, which themselves decreased with soil N, supporting our hypothesis that the RAH applies for intraspecific variation across spatial gradients. Additionally, high precipitation seasonality and soil nitrogen predicted decreased herbivory. The results suggest that spatial variation in herbivory can be driven by factors other than herbivore communities and climatic gradients, and that bottom-up processes, where plant traits and soil fertility control leaf consumption, must be incorporated into spatial predictions of herbivory.

Herbivory on freshwater macrophytes from the perspective of biological invasions: a systematic review

The previously neglected herbivore–aquatic macrophyte interaction has received more attention among scientists in the recent decades, especially in the context of biological invasions. However, there is still a great deal of work needed to improve scientific knowledge about this relationship and to improve biological management and control techniques. This systematic review provides an overview of temporal and spatial trends and the methodological approaches, habitats, and species most studied concerning this interaction. We evaluated scientific articles published in journals indexed to Web of Science that measured the consumption or other direct effects of herbivores on freshwater macrophytes, including non-native species. From 1992 to 2017, there was a growth rate of approximately three times in the publication of such articles, although they are concentrated in the temperate and subtropical zones, neglecting tropical and subpolar environments. We have also noticed a simple general pattern in most of the topics evaluated here, such as the low preference for using tests of multiple hypotheses and for applying both experimental and fieldwork methods together. Deep lakes and rivers were the most studied ecosystems, while shallow lakes, ponds, streams and wetlands had less attention. Non-native macrophytes were more studied than non-native herbivores. The macrophyte life forms most studies were rooted submerged, free-floating and emergent species, while the herbivore taxa most often examined in these studies were fish, molluscs and crustacea. We suggest performing studies that are more complex, using multi-species biological communities, with a focus on the unexplored pointed areas to advance scientific knowledge regarding herbivory on macrophytes, especially in tropical areas.

Living on a trophic subsidy: Algal quality drives an upper-shore herbivore's consumption, preference and absorption but not growth rates.

The transfer of seaweeds from subtidal bottoms to nearby intertidal rocky shores is a common but often overlooked phenomenon. Freshly detached seaweeds often represent critical trophic subsidies for herbivores living in upper-shore rocky intertidal areas, such as the marine snail Diloma nigerrima. This species relies on three species of seaweeds for food and displays feeding strategies to deal with a resource that is scarce and at times unpredictable. This study focused on the nutritional quality of freshly detached algae (Durvillaea antarctica, Lessonia spicata and Lessonia trabeculata) and measured Diloma nigerrima’s algal consumption rates in trials with and without choice. Absorption efficiency and growth of individual snails fed on each alga were also measured. Durvillaea antarctica had the highest nutritional quality and was the most consumed algae in both single and multiple-choice trials. Absorption efficiency was also highest for D. antarctica but growth rates of snails fed with this species were similar to those fed with the other algae. Combined, these results suggest that D. nigerrima has the ability to discriminate among seaweeds based on their nutritional quality. A potential increase in oxygen uptake when D. nigerrima is consuming the preferred food item is also proposed as a plausible hypothesis to explain the mismatch between snails’ preference and growth rate. These results aim to guide further studies on trophic subsidies and their role in coastal systems.