Herbivore Abundance Research Articles

A novel trophobiotic interaction between a Neotropical stink bug and an ant species: Insights into potential benefits to the host plant

Trophobiotic interactions occur when phytophagous insects provide a sugary liquid, the honeydew, for ants and obtain defence against predators or parasitoids. The plants may indirectly benefit from an increased ant foraging activity by reducing the herbivorous abundance. These three trophic interactions have been previously studied for several species, but mainly involving plants with extrafloral nectaries, which is a plant structure that also produce attractive substances for ants. Previous studies have reported an ant preference for honeydew over extrafloral nectary content. Therefore, trophobiosis can be an important mediator of ant-plant interactions. In this study, we describe a trophobiotic interaction between Edessa contermina stink bugs and Camponotus blandus ants on the Byrsonima verbascifolia plants occurring in a conservation area of Brazilian savanna. Stink bugs excreted a sugary liquid which was consumed by the ants, and C. blandus ants were observed consuming potential parasitoids. Stink bugs were more abundant in plants containing high food supply and shelter availability. The occurrence of ants depended of the number of inflorescences and trunk circumference of B. verbascifolia. Ant abundance, however, was positively correlated with stink bug abundance and the number of inflorescences. Herbivory was not explained by neither plant architecture nor ant abundance. This high ant activity may benefit plants from a protection against herbivory, but we did not detect this effect during the study period. Hence, the interaction among ants and plants was apparently commensal. We concluded that plant traits were important in ant attraction, but stink bugs foraging also increased ant activity on the plant, but mainly on inflorescences. Therefore, the plant may benefit from an increased defence of inflorescences rather than leaves.

Coupled effects of climatic forcing and the human footprint on wildlife movement and space use in a dynamic floodplain landscape

With climate change, terrestrial fauna in riparian floodplain ecosystems must adapt to a predicted increase in frequency and magnitude of fluvial perturbations. Seasonal migration to seek refuge from floodwaters represents a central adaptation strategy, but may entail risky navigation of anthropogenic spaces in heterogeneous landscapes. Here, we demonstrate the opportunities and constraints large-bodied mammalian herbivores face during an adaptive response of obligatory flood-driven refuge migration, across a human-dominated environment. Our study system, centred around a productive protected area––Kaziranga National Park in Assam, Northeast India––on the floodplains of the Brahmaputra River, is home to an abundance of large herbivores that undertake seasonal migrations in response to floods. We contrast species distribution data during a major flood event with those from the dry season to illustrate season-specific movement and space use decisions of large herbivores ranging in body mass from the 3000-kg Asian elephant Elephas maximus to the 20-kg muntjac Muntiacus muntjak. In the dry season, most large herbivores––a majority of which are endangered and threatened by anthropogenic pressures––avoided areas with a strong human footprint, while preferring spaces with high land-use diversity. During the floods, such species were pushed out of inundated habitats within the protected area, and they chose to move through woodlands and areas under bamboo cover on private lands, as they migrated to forested refugia on higher ground. Our results show how seasonal environmental constraints shaped by floods determine the internal motivation of animals to risk traversing a human-dominated space to seek refuge, which contextually defines how animals view and navigate the landscape. Such insights underscore the importance of dynamic and adaptive planning, and participatory conservation efforts, to facilitate connectivity in the changing environment and climate of the present Anthropocene.

Multifunctionality of an Urbanized Coastal Marine Ecosystem

Coastal marine ecosystems provide numerous invaluable services and benefits to humankind. However, urbanization of coastal areas has homogenized and reduced the biodiversity of the surrounding marine environment and the sustainability of the multiple ecosystem services it provides. Studies have focused on single ecosystem functions despite human populations relying on several functions being delivered at once (known as multifunctionality). This study investigates five ecosystem functions (primary productivity, herbivory, predation, organic matter decomposition and carbon sequestration) and overall multifunctionality in four sites along a gradient of 16 environmental parameters. Ecosystem function varied significantly between sites that were farthest apart. In determining factors that drove ecosystem functioning, we found a positive relationship between coral cover and primary productivity but negative relationships between coral cover and levels of herbivory and predation intensity. Higher temperatures and greater concentrations of chlorophyll-a had a positive impact on predation and herbivory, respectively. Notably, we found a significant negative impact of total inorganic nitrogen and significant positive impact of total Kjeldahl nitrogen on carbon sequestration. Further, individual functions were compared with fish abundance (obtained from seawater eDNA), and benthic community composition (obtained from plate % coverage of autonomous reef monitoring structures). Increasing herbivorous fish abundance had a positive impact on Ulva mass loss. Overall, relative abundance of predatory, omnivorous and planktivorous fish exerted overriding influences on primary productivity and predation intensity, implying that fishing pressure and marine protected area status are important factors. Importantly, we found significant effects from environmental parameters indicating that reliably predicting the effects of future anthropogenic impacts will not be straightforward as multiple drivers are likely to have complex effects. Taken together, urbanized coastal ecosystems exhibit varying levels of multifunctionality depending on the extent of human impact, and the functional diversity of the benthic community present.

Grazing by over-abundant native herbivores jeopardizes conservation goals in semi-arid reserves

Relaxation of predation pressure following the removal of mammalian predators has led to the irruption of large herbivores and excessive levels of herbivory in many regions of the Earth. Conservation reserves in dryland regions aim to restore ecological processes and facilitate biodiversity conservation by functioning as refuges from grazing by livestock. However, grazing pressure in conservation reserves may be high and hamper conservation objectives because wild herbivore populations have irrupted in the surrounding landscape due to predator control as well as the absence of hunting and competition with livestock within reserves. Here, we assess the relative abundance of native herbivores (kangaroos) and introduced herbivores (rabbits) using driving transects and dung surveys, and use selective exclosures to assess wild herbivores’ impacts on vegetation and soils in four conservation reserves in semi-arid Australia. Kangaroos were the dominant herbivore in each reserve. Grazing by kangaroos and/or rabbits was linked to reduced complexity of understorey vegetation, grass cover, species richness of grasses, forbs and shrubs, the depletion of soil carbon and phosphorous, and increased soil bulk density. The marked impacts of grazing by wild herbivores, particularly kangaroos, on vegetation and soils that we report are symptomatic of overgrazing. Our study provides evidence that grazing by kangaroos may jeopardize conservation efforts across a large region of semi-arid Australia. We contend that managing the total grazing pressure exerted by wild herbivores is crucial to prevent overgrazing in dryland conservation reserves where herbivore populations are not regulated by predators.

Mammalian herbivory in post-fire chaparral impacts herbaceous composition but not N and C cycling

Abstract Aims Classical theory predicts that herbivores impact herb assemblages and soil nitrogen (N) cycling through selective plant consumption and the deposition of N-rich waste, with effects dependent upon ecosystem N availability. Herbivores are predicted to accelerate N cycling when N availability is high and decelerate cycling when availability is low. However, experimental tests of these theories in natural systems are limited and have yielded contradictory results. California’s widespread chaparral shrublands provide a tractable system in which to test these theories. They are prone to periodic crown fire, which temporarily removes living shrub cover, deposits mineral N on soils and allows diverse herbaceous assemblages to dominate the landscape for 3–5 years. Chaparral is also increasingly vulnerable to herbaceous invasion; mammalian herbivory may limit the establishment of non-native herbs in the shrub understory. Methods We implemented a 2-year herbivore-exclosure experiment (Hopland, CA) to assess the impact of mammalian herbivory during early post-fire chaparral succession, both on herbaceous plant assemblages and soil N and C cycling. We predicted that, in high-N post-fire conditions, mammalian herbivory would not demonstrate a strong preference for N-fixing herbs, would accelerate N cycling and would reduce the abundance of non-native herbs. Important Findings Excluding mammalian herbivores increased herb standing biomass by 54%, but changed neither the relative abundance of N-fixing vs. non-N-fixing herbs nor any measure of N or C cycling. Herbivore impacts on nutrient cycling may not be significant over the 2-year time scale of the experiment and physical effects of herbivore activity could have counteracted the influence of plant litter and animal dung/urine inputs. Mammalian herbivores concentrated their feeding on typical non-native herbs, slightly decreasing their relative abundance; however, mammalian herbivory was not sufficient to stem the invasion of chaparral by invasive herbs or alter C and N cycling over the first 2 years after fire.

Does leaf flushing in the dry season affect leaf traits and herbivory in a tropical dry forest?

In tropical dry forests (TDFs), stem-succulent deciduous species produce leaves during the dry season which coincides with the period of lower herbivore abundance. In this study, we evaluated the effects of abiotic factors (precipitation and day length) on the vegetative phenology of three stem-succulent deciduous species (Cochlospermum vitifolium, Commiphora leptophloeos, and Manihot anomala) during 2years. In addition, we compared leaf damage by herbivores and leaf defensive traits (specific leaf area, thickness, and content of phenolic compounds) on leaf cohorts produced before and during the rainy season by these stem-succulent deciduous species. We also evaluated herbivory and defensive traits on leaves produced during the rainy season by 14 non-succulent deciduous species. There was a positive effect of precipitation and day length on the amount of green leaves exhibited by the three stem-succulent species. The leaf cohort produced during the dry season by stem-succulent species showed lower leaf damage and content of phenolic compounds than the cohort produced during the rainy season by the same species and by non-succulent deciduous species. Leaf damage was only affected (positively) by the content of phenolic compounds, suggesting the production of induced defenses during leaf expansion. In general, herbivory levels were low in this study (0.57-6.37%) when compared with other TDFs, suggesting that a scape from herbivores due to anticipated leaf production is a weak selective force affecting plant fitness. These variations in leaf traits are mostly related to contrasting water conservation strategies among phenological groups. Further studies should evaluate other defensive and nutritional traits, as well as their variations along the leaf lifespan, to unravel herbivory patterns in TDFs.

Approaching a Tipping Point? Herbivore Carrying Capacity Estimates in a Rapidly Changing, Seagrass-Dominated Florida Bay

Herbivory is a key structuring force that can have negative, positive, or mixed impacts on seagrasses. The identity and abundance of herbivores, as well environmental conditions such as solar insulation, can influence the impacts of herbivory. To understand the impact of herbivores on turtlegrass in warm, temperate St. Joseph Bay (SJB) in the northeastern Gulf of Mexico, we estimated densities of the most common herbivores: variegated sea urchins and green turtles. We also estimated SJB’s herbivore carrying capacities by estimating annual average turtlegrass production and variegated urchin consumption rates and by using previously calculated juvenile green turtle consumption rates and seagrass area. During summer, turtlegrass exhibited compensatory growth due to urchin herbivory, but during winter, turtlegrass growth was negatively affected by urchin grazing. Given our calculated annual turtlegrass production, urchin ingestion rates, and the average urchin density of 5.89 ± 0.09 (SE) urchins ha−1, the turtlegrass production not consumed by urchins can sustain 278.0 juveniles ha−1, or about 556,010 turtles, putting current average green turtle abundance of 26 ± 3.7 individuals ha−1 at 4.0–14.6% of carrying capacity. Previous work in this system has shown that simulated turtle herbivory can reduce turtlegrass productivity—with this potential reduction in production, SJB could not sustain a green turtle population at current urchin densities. Given the rapid global green turtle increase, evaluating densities and future carrying capacities of herbivores in higher latitude seagrass pastures is critical for updating and achieving recovery goals for both green turtles and globally declining seagrass meadows.

Early snowmelt reduces aphid abundance (Aphis asclepiadis) by creating water-stressed host plants (Ligusticum porteri) and altering interactions with ants

Declining snow cover is reshaping ecological communities. Early loss of snow cover initiates changes in key interactions that mediate herbivore abundance, i.e., top-down and bottom-up effects. In this study, we used a field experiment to test the effects of host plant water stress and phenology on the multitrophic interactions that determine aphid abundance. The aphid, Aphis asclepiadis, in our study system colonizes the flowering stalks of the host plant Ligusticum porteri and relies on a protection mutualism with ants. We added snow and water to replicate host plants and tested for a variety of phenological and physiological responses to these treatments. Relative to host plants in ambient conditions, both water and snow addition reduced key signals of water stress (senescence and abscisic acid levels) and increased seed set. While aphid colonies were generally larger with reduced host plant water stress, the ant–aphid mutualism interacted with plant quality in complex ways. Without ant tending, we did not detect differences in aphid colony growth with host plant treatment. When tended by ants, aphid colony growth was greatest on host plants with snow addition. Host plant quality also altered the benefits exchanged in this mutualism. Ant-tended colonies hosted by plants with snow addition produced honeydew enriched in trehalose, which may have decreased both ant and natural enemy abundance. Our results suggest that early loss of snow reduces aphid abundance by creating low-quality, water-stressed host plants, and this effect may be exacerbated by natural enemies and the costs of ant attendance.

Fish Assemblage Structure in the Northwestern Hawaiian Islands Is Associated with the Architectural Complexity of Coral-Reef Habitats

The architectural complexity of coral-reef habitat plays an important role in determining the assemblage structure of reef fish. We investigated associations between the reef habitats and fish assemblages in the Northwestern Hawaiian Islands (NWHI) using in situ fish counts and data on habitat metrics and benthic community composition that were obtained from three-dimensional (3D) photogrammetric reconstructions of the surveyed sites. The structure of fish assemblage as a whole on the basis of Bray–Curtis dissimilarity, species richness and the abundances of herbivores and piscivores were associated with habitat metrics, with higher levels of architectural complexity generally supporting greater numbers of fish species and individuals. Benthic cover did not explain additional variation in these variables after the effects of habitat metrics were taken into account. Corallivorous fish was the only group that showed positive associations with both habitat metrics and benthic cover (Acropora and Pocillopora corals). The total fish abundance and the abundances of planktivores and invertivores did not show associations with either habitat metrics or benthic cover. This study suggests that an appropriate combination of habitat metrics can be used to account sufficiently for the effects of habitat architecture on fish assemblages in reef monitoring efforts in the NWHI.

Macroalgal defense phenotype correlates with herbivore abundance

A primary goal in the study of producer–herbivore interactions is to characterize the tradeoffs between primary producer growth and defense. Across the Aleutian Island Archipelago, the widespread decline in sea otters has resulted in reduced predation on sea urchins, which has led to increases in urchin populations, the formation of urchin barrens, and ultimately to overgrazing of much of the region’s kelp forests. The occurrence of both kelp forests and urchin barrens on islands, along with among island variation in the time period that urchin barrens have formed, presents a unique opportunity to characterize the extent to which exposure to intense herbivory and increased light may alter marine macroalgal growth and defense tradeoffs. To address this, we used a field caging experiment with Codium ritteri, a common perennial green macroalga in the Aleutian Archipelago, to test whether urchin barren macroalgae exhibit increased defenses and reduced growth relative to kelp forest individuals. Our results suggest that urchin barren C. ritteri had greater defense than growth relative to kelp forest individuals. In the laboratory, we found little evidence for urchin barren C. ritteri growth under low light or altered defenses at high light. Grazing rates on C. ritteri were correlated with urchin biomass in the field suggesting higher herbivory intensity may shift primary producer energy allocation from growth to defense. Together, our data suggest that macroalgae occurring within kelp forests grow faster but are more palatable than macroalgae occurring in urchin barrens, which may increase urchin deforestation potential.

Negative effects of an allelopathic invader on AM fungal plant species drive community-level responses.

The mechanisms causing invasive species impact are rarely empirically tested, limiting our ability to understand and predict subsequent changes in invaded plant communities. Invader disruption of native mutualistic interactions is a mechanism expected to have negative effects on native plant species. Specifically, disruption of native plant‐fungal mutualisms may provide non‐mycorrhizal plant invaders an advantage over mycorrhizal native plants. Invasive Alliaria petiolata (garlic mustard) produces secondary chemicals toxic to soil microorganisms including mycorrhizal fungi, and is known to induce physiological stress and reduce population growth rates of native forest understory plant species. Here, we report on a 11‐yr manipulative field experiment in replicated forest plots testing if the effects of removal of garlic mustard on the plant community support the mutualism disruption hypothesis within the entire understory herbaceous community. We compare community responses for two functional groups: the mycorrhizal vs. the non‐mycorrhizal plant communities. Our results show that garlic mustard weeding alters the community composition, decreases community evenness, and increases the abundance of understory herbs that associate with mycorrhizal fungi. Conversely, garlic mustard has no significant effects on the non‐mycorrhizal plant community. Consistent with the mutualism disruption hypothesis, our results demonstrate that allelochemical producing invaders modify the plant community by disproportionately impacting mycorrhizal plant species. We also demonstrate the importance of incorporating causal mechanisms of biological invasion to elucidate patterns and predict community‐level responses.

The prehistory and early history of the Šumava Mountains (Czech Republic) as seen through anthropogenic pollen indicators and charcoal data

In the lower forested mountain ranges of Europe, human impact on nature is usually confined to the written history of the Middle Ages. Our research in the Šumava mountains aims to specify the nature and intensity of human impact on vegetation, especially during agricultural prehistory. We use results from a multidisciplinary study of the unique La Tène archaeological site in the Sklářské Valley (elevation 802 m a.s.l.) and from a pollen and charcoal record 60 m away. With knowledge of this reference site we focus on the meaning of anthropogenic pollen indicators in 13 other pollen sites from central Šumava. From ca 3300 cal yr BP we detect an increase in NAP, Betula, Pinus and secondary anthropogenic indicators in pollen records – vegetation changes of anthropogenic origin. Charcoal records show a significant peak around 3200 cal yr BP. We found weak anthropogenic influence on the La Tène archaeological site in the Sklářské Valley, and much stronger anthropogenic pollen signals at other pollen sites dated to the Late Bronze and Iron Ages. Some of these sites are situated on trade routes which have been known since Medieval times but which most likely have much older origins. During prehistory, pollen data reveal no specific human activity such as pasturing or arable farming but reflect small-scale disturbances that supported growth of Betula and Pinus and an abundance of herbs. Such human impact could be connected primarily to activities along trade routes and to hunting, but other factors cannot be excluded.

Light environments affect herbivory patterns but not reproductive performance of a multivoltine specialist moth, Pareuchaetes pseudoinsulata

Unravelling the responses of insect herbivores to light-environment-mediated variation in the traits of their host plants is central to our understanding of the nutritional ecology of, and factors driving the population dynamics in, these species. This study examined the effect of light environment (shaded vs full-sun habitat) on leaf toughness and leaf nutritional quality in Chromolaena odorata (an invasive species in West Africa) and related these attributes to the abundance, herbivory patterns and reproductive performance of a multivoltine specialist moth, Pareuchaetes pseudoinsulata (a biological control agent). In this system, plants growing in shaded areas in the field experienced more herbivory and had higher herbivore abundance than those growing in full-sun. In the laboratory, P. pseudoinsulata larvae consumed significantly greater amounts of shaded foliage relative to full-sun foliage. However, reproductive performance metrics such as mating success, pre-oviposition period, number of eggs laid, duration of egg laying, egg hatchability, and adult longevity in P. pseudoinsulata did not differ according to foliage types. Reduced leaf toughness, increased water and nitrogen contents in shaded leaves coincided with increased leaf consumption by the larvae of P. pseudoinsulata. In summary, this study showed for the first time that light environments affect herbivory patterns but not reproductive performance of P. pseudoinsulata and hypothesized that high foliar nitrogen and water contents in shaded leaves resulted in feedback and necessity consumption patterns.

Role of plant diversity on arthropod communities in a restored tallgrass prairie of the U.S. Midwest

We investigated the effects of enhanced plant species diversity on prairie restoration on arthropod community assembly in a restored tallgrass prairie of the U.S. Midwest. Despite weak correlation with the arthropod taxon, enhanced plant species diversity in the restored prairie (RP) promoted the evenness and diversity of arthropod functional groups and led to a divergence of arthropod assemblage in comparison to the ones in old field (OF) and monospecific stand (reed canary grass [RCG]) of exotic reed canary grass (Phalaris arundinacia). Pollinators were most and least abundant in RP and RCG, respectively, and exhibited a positive correlation to plant species diversity. Herbivore abundance, highest in RP, also increased with plant species diversity. The diversity of arthropod functional groups was likely facilitated by structural complexity of the RP vegetation that resulted from the enhanced plant species diversity, particularly flowering and nectar‐producing forbs. Predator abundance, highest in RCG, decreased with plant species diversity and increased with C3 grass cover. The presence of small‐body sized herbivores seemed to attract predators in the RCG site, which has a monospecific vegetation structure of C3 reed canary grass. Our results demonstrate a positive effect of prairie restoration on the diversity of arthropod functional groups. We recommend increasing the diversity of native plant species and reduction (or eradication if possible) of exotic plants in the OF and RCG sites.

Soil macroarthropod community and soil biological quality index in a green manure farming system of the Brazilian semi-arid

Soil macroarthropods are organisms considered as key factors to sustain soil quality and sustainability due to their services to soil ecosystem. The community structure and seasonal variation of soil macroarthropods in 5-year cultivation of green manure plant species in the Brazilian semi-arid, Areia, Paraiba, Brazil were investigated between June and December 2018. Soil samples and macroarthropod specimens were collected using soil cores and Provid-type traps, respectively, during rainy and dry seasons. We characterized both soil chemical properties and macroarthropod community under ten green manure plant species: Brachiaria decumbens Stapf. cv. Basilisk, Canavalia ensiformis (L.) DC, Crotalaria juncea L., Crotalaria ochroleuca G. Don, Crotalaria spectabilis Roth, Lablab purpureus (L.) Sweet, Mucuna pruriens (L.) DC., Neonotonia wightii (Wight & Arn.) J.A. Lackey, Pennisetum glaucum L., and Stilozobium aterrimum Piper & Tracy. The highest values of richness, diversity and dominance in the macroarthropod community during the rainy season were found on the plots where C. spectabilis and M. pruriens were cultivated, whereas during the dry season the highest values were found in the plots where C. ochroleuca, C. spectabilis, and S. aterrimum were cultivated. In the plots where B. decumbens and P. glaucum where cultivated, we found lower values of richness, diversity, and dominance in the macroarthropod community compared to the leguminous plant species during rainy and dry seasons. Our findings suggest that: 1) green manure practice and seasonality changed soil macroarthropod community, trophic structure, and ecological processes in semi-arid conditions; and 2) abundance of predators, ecosystem engineers, decomposers and herbivores was promoted by plant species from Fabaceae family. The results highlight the importance to consider plant species from Fabaceae family as habitat and food resources for soil fauna community.

Small-scale variation in herbivore abundance and grazing on Juncus roemerianus dominated salt marshes

Herbivore-plant interactions have been shown to play central roles in determining the structure of salt marsh communities. However, relatively little is known about how marsh herbivory varies over small spatial scales (e.g., < 2 km) within a single geographic region as well as the potential driving forces for such variability. Here we quantify the small-scale spatial variablity in insect grazing on three Juncus roemerianus marshes in Grand Bay National Estuarine Research Reserve, MS, USA. Sampling covered both monthly and seasonal temporal scales (February to November) to capture the well described seasonality in insect grazing in these marshes Our results show large differences in abundance of insect herbivores and intensity of herbivory across, but not within, the three marshes. In addition, the observed spatial differences in herbivory do not appear to be related to herbivore abundance or insect species, but potentially to differences in landscape context, such as proximity to upland habitats (i.e., forestland) or habitat fragmentation. These results demonstrate that insect herbivory in marshes can also vary substantially at small spatial scales and we suggest some mechanisms responsible for such differences.

Why do certain species dominate? What we can learn from a rare case of Microdictyon dominance on a Caribbean reef

AbstractMany Caribbean reefs have shifted from coral dominance to macroalgal dominance, often by brown algae such as Dictyota and Lobophora. However, the north side of Cayman Brac in the Cayman Islands is dominated seasonally by the green macroalga Microdictyon (percent cover of Microdictyon is 4% in the winter and ~40% of the reef in the summer), although it is absent from the south side of the island and the remainder of the country. Indeed, Microdictyon is rare in much of the Caribbean, so this situation on Cayman Brac provides an opportunity to investigate the conditions that facilitate its distribution and dominance. The impact of herbivory, competition, nutrient input and other abiotic conditions were examined as factors that could influence the distribution and dominance of Microdictyon. While herbivory or nutrient input are frequently found to be key drivers of benthic community composition on coral reefs, here consumption of Microdictyon by herbivores was low, and thus, the alga was not subject to strong top‐down control by herbivory. So, in this case, neither herbivore abundance nor feeding preference appeared to influence the distribution of Microdictyon. Nutrient input was also similar to both sides of the island suggesting nutrients played little role in differential distribution. But, in a controlled transplant experiment where Microdictyon was protected from herbivory and competition, it experienced almost complete mortality (93.3%) when transplanted to the south side, compared to only 11.8% mortality on the north. The south side was exposed to the strongest wave action 92% of the days in our study and was on average a slight, but significant 0.2°C warmer. Thus, these data suggest physical forcing (i.e. wave exposure) is the most likely factor dictating Microdictyon distribution. Conversely, a combination of reduced herbivory and increased competitive strength may explain the seasonal dominance of Microdictyon on the north side of Cayman Brac. Microdictyon was a competitive inferior to the other common algae in winter but increased in competitive strength to equal other species in summer. These results add to the literature on Microdictyon and on the forces impacting benthic community structure of coral reefs.

Rewilding of large herbivore communities in high elevation Puna: geographic segregation and no evidence of positive effects on peatland productivity

During the past decades, the Argentine Puna (a subtropical high elevation desert of c. 14 million hectares) has been going through a process of “rewilding” of large herbivore communities. In response to rural population outmigration and resulting livestock reduction accompanied by protection measures, large wild herbivores such as vicunas increased. To explore the ecological consequences of this transition, we analysed the spatial patterns of wild herbivores and livestock in relation to human settlements, and we estimated the changes in vegetation productivity of peatlands, using NDVI derived from MODIS satellite images between 2001 and 2012. Peatlands are key ecosystems in high elevation deserts; they regulate water and carbon fluxes and provide most forage for livestock and wildlife. A field survey of 50 peatlands revealed that travel time from human settlements was positively correlated with the wild herbivore abundance, and negatively correlated with livestock abundance (especially sheep and goats). Thus, it is a good indicator of livestock use. At the regional scale, after controlling for the physical and climatic variables of the 8134 peatlands, accessibility from human settlements explained less than 0.1% of mean and interannual NDVI variability. These results provide no evidence of livestock-induced degradation. Furthermore, likely due to rainfall increase, peatlands showed an overall positive NDVI trend between 2001 and 2012, but isolated peatlands showed comparatively more negative NDVI trends during the same period, possibly associated with increased wildlife herbivory. Similar rewilding processes could occur in many mountain regions undergoing decreasing human population and marginal land uses. Our study suggests that traditional management could contribute to the productivity, stability, and resilience of peatlands.

Climate seasonality drives ant–plant–herbivore interactions via plant phenology in an extrafloral nectary‐bearing plant community

Abstract Interactions between ants and plants bearing extrafloral nectaries (EFNs) are among the most common mutualisms in Neotropical regions. Plants secrete extrafloral nectar, a carbohydrate‐rich food that attracts ants, which in return protect plants against herbivores. This ant–plant mutualism is subjected to temporal variation, in which abiotic factors can drive the establishment and frequency of such mutualistic interaction. However, studies investigating how abiotic factors (e.g. climate) directly and indirectly influence ant–plant–herbivore interactions are incipient. In this study, we investigated direct and indirect (via plant phenology) effects of temperature and rainfall on ant–plant–herbivore interactions. To address these goals, each month we estimated six plant phenophases (newly flushed leaves, fully expanded leaves, deciduousness, floral buds, flowers and fruits), the activity of EFNs and abundance of ants and herbivores in 18 EFN‐bearing plant species growing in a markedly seasonal region (the Brazilian Cerrado) during a complete growing season. Our results showed that (a) there were marked seasonal patterns in all plant phenophases, EFN activity and the abundance of ants and herbivores; (b) the peak of EFN activity and ant and herbivore abundance simultaneously occurred at the beginning of the rainy season, when new leaves flushed and (c) rainfall directly and indirectly (via changes in the production of new leaves) influenced EFN activity and this in turn provoked changes in ant abundance (but not on herbivores). Synthesis. Overall, our results build towards a better understanding of how climate drives seasonal patterns in ant–plant–herbivore interactions, explicitly considering plant phenology over time.

A comparison of weed, pathogen and insect pests between low tunnel and open-field grown strawberries in New York

While growing strawberries under plastic low tunnels is an increasing trend in the northeastern U.S., the effect of low tunnels on the incidence and severity of arthropod pests, pathogens, and weeds is largely unknown and presents a possible barrier to commercial adoption. During 2018 and 2019, we identified and quantified pest abundance on low tunnel versus open field grown strawberries at a research site in Geneva, New York, and compared these trends under three plastic types in 2019. Overall, we found that while yield and fruit marketability increased under tunnels of all plastic types compared to the open-field, ground-dwelling and foliar herbivores (mostly Tetranychus urticae) abundance was higher under low tunnels compared to open plots. In contrast, herbivores caught on clear sticky cards were more prevalent in open plots than under tunnels. A neutral effect of tunnels was present for Lygus lineolaris density and weed biomass during both years, although damage by L. lineolaris decreased under UV-limiting plastics. Tunnels also reduced infestation by Drosophila suzukii and several pathogens on foliage and fruit. This study provides needed information on pest communities of low tunnel strawberry in the Northeast, and could be used as an essential foundation for future IPM research.