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opencc-zeroDec 2016View details →

Data from: Testing genotypic variation of an invasive plant species in response to soil disturbance and herbivory

Herbivores, competitors, and predators can inhibit biological invasions ("biotic resistance" sensu Elton 1959), while disturbance typically promotes biological invasions. Although biotic resistance and disturbance are often considered separately in the invasion literature, these two forces may be linked. One mechanism by which disturbance may facilitate biological invasions is by decreasing the effectiveness of biotic resistance. The effects of both disturbance and biotic resistance may vary across invading genotypes, and genetic variation in the invasive propagule pool may increase the likelihood that some genotypes can overcome biotic resistance or take greater advantage of disturbance. We conducted an experimental field trial in which we manipulated soil disturbance (thatch removal and loosening soil) and the presence of insect herbivores and examined their effects on the invasion success of 44 Medicago polymorpha genotypes. As expected, insecticide reduced leaf damage and increased Medicago fecundity, suggesting that insect herbivores in this system provide some biotic resistance. Soil disturbance increased Medicago fecundity, but did not alter the effectiveness of biotic resistance by insect herbivores. We found significant genetic variation in Medicago in response to disturbance, but not in response to insect herbivores. These results suggest that the ability of Medicago to invade particular habitats depends on the amount of insect herbivory, the history of disturbance in the habitat, and how the specific genotypes in the invader pool respond to these factors.

opencc-zeroFeb 2020View details →

Data from: Herbivory and climate as drivers of woody plant growth: Do deer decrease the impacts of warming?

Vegetation at ecotone transitions between open and forested areas is often heavily affected by two key processes: climate change and management of large herbivore densities. These both drive woody plant state-shifts, determining the location and the nature of the limit between open and tree or shrub-dominated landscapes. In order to adapt management to prevailing and future climate, we need to understand how browsing and climatic factors together affect the growth of plants at biome borders. To disentangle herbivory and climate effects, we combined long-term tree growth monitoring and dendroecology to investigate woody plant growth under different temperatures and red deer (Cervus elaphus) herbivory pressures at forest-moorland ecotones in the Scottish highlands. Reforestation and deer densities are core and conflicting management concerns in the area, and there is an urgent need for additional knowledge. We found that deer herbivory and climate had significant and interactive effects on tree growth: in the presence of red deer, pine (Pinus sylvestris) growth responded more strongly to annual temperature than in the absence of deer, possibly reflecting differing plant-plant competition and facilitation conditions. As expected, pine growth was negatively related to deer density and positively to temperature. However, at the tree population level, warming decreased growth when more than 60% of shoots were browsed. Heather (Calluna vulgaris) growth was negatively related to temperature and the direction of the response to deer switched from negative to positive when mean annual temperatures fell below 6.0°C. In addition, our models allow estimates to be made of how woody plant growth responds under specific combinations of temperature and herbivory, and show how deer management can be adapted to predicted climatic changes in order to more effectively achieve reforestation goals. Our results support the hypothesis that temperature and herbivory have interactive effects on woody plant growth, and thus accounting for just one of these two factors is insufficient for understanding plant growth mechanics at biome transitions. Furthermore, we show that climate-driven woody plant growth increases can be negated by herbivory.

opencc-zeroMay 2020View details →

Data from: Tree seedling responses to leaf-cutting ants herbivory in Atlantic Forest restoration sites

Leaf-cutting ants (LCA) are generalist herbivores capable of causing severe plant damage. Negative impacts of ant herbivory vary according to the density of nests and availability of palatable plants; however, it is not yet clear how these herbivores affect tropical forest restoration sites. To investigate how LCA preference affects plant species performance, we evaluated the herbivory of Atta sexdens rubropilosa on native tree species seedlings in Atlantic Forest restoration sites. We expected pioneer species to suffer higher herbivory by LCA when compared with non-pioneer species, and that species with higher damage will have poorer growth and higher mortality. The experiment was conducted in three restoration sites in northern Paraná state, southern Brazil, with 1500 seedlings of 5 pioneer and 5 non-pioneer species. Sites share similar age, stand size, tree species composition, and LCA nest density. The number of attacks, degree of leaf damage, number of leaves, plant height and survival were recorded. Specific leaf area, leaf polyphenols, flavonoids, tannins, and nitrogen content were analyzed for each species. Plant damage was similar between pioneer and non-pioneer plant species. This could be explained by trait variability among species in each group and by LCA generalist foraging. Preferred species suffered decreases in growth and survival. Less preferred species suffered fewer ant attacks and no change in performance. Results suggest that ant herbivory can influence plant species establishment and thus species composition in restoration sites by reducing performance and increasing mortality of some, but not all species, making LCA an important ecological filter.

opencc-zeroDec 2023View details →

Plant size, latitude, and phylogeny explain within-population variability in herbivory

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sparse data. We collected standardized surveys of herbivory for 503 plant species at 790 sites across 116° of latitude. With these data, we show that within-population variability in herbivory increases with latitude, decreases with plant size, and is phylogenetically structured. Differences in the magnitude of variability are thus central to how plant-herbivore biology varies across macroscale gradients. We argue that increased focus on interaction variability will advance understanding of patterns of life on Earth.

opencc-by-4.0Mar 2024View details →

Insect herbivory in a South African savanna-forest mosaic: neglected but substantial

These are primary data for the study of insect herbivory conducted in the savanna-forest mosaic of HluHluwe Imfolozi Park in South Africa. The submission contains the following files: specifically, notes for scripts and data particularly used in this study. 1. Script 00_Configuration for R 2. Script 01_types_of_herbivory represents Figure 3a and Figure S1 3. Script 02_subset7_speciesALLhabitats represents Figure 3b, Figure S4, S5 4. Script 03_leaf_size_explorations represents Figures S2 and S3 5. Script 04_Species_traits_analyses represents Table 1 6. Script 05_Savanna correlation 7. Script 06_herbivory_savanna_PCA represent figure 4b Data used: 1. Data = Distribution_herbivory_class represented Figure_2b & TableS4 2. Data = Mean proportion of leaf area eaten by chewers and miners per individual plant species represent figure 2a 3. Data = Data_Table S1_fire_mammal gradient 4. Data =  Leaf sizes investigations  for all plant species 5. Data = KTraits_20220625_PhylTrait.csv represents phylogenetic correlation signals in table 1 for correlation matrix (Pearson correlation). 6. Data = 07_dataset_herbivory_fortraits.csv represents correlation table 1 or correlation matrix (Pearson correlation). 7. Data = Environment_savanna_correlations_ExcelPlot.2024 represents Figure S6a & 6b

opencc-zeroMar 2024View details →

The combined effects of resource landscapes and herbivory on pollination services in agro-ecosystems

We apply a resource landscape approach to map the spatial distribution of floral resources across landscapes using neighbourhood modelling and empirical data on floral availability at specific land-use types. In each of 25 Mediterranean landscapes, spanning a gradient of natural-agricultural land use intensity, we established a pair of arrays of potted phytometer plants (White Wall-rocket, Diplotaxis erucoides) that were either aphid-infested or aphid-free. In each array, we recorded the activity of insect flower visitors and subsequent seed-set. At the same time, we also recorded the relative flower abundance in dominant land uses at 1 km radii around each array.

opencc-by-4.0Apr 2024View details →

Data and code for : 'Interactive effects of temperature, aridity, and plant stoichiometry on insect herbivory: past and present', The American Naturalist

The files are for the manuscript 'Interactive effects of temperature, aridity, and plant stoichiometry on insect herbivory: past and present' consist of the following major parts:   1.     FILE “all site summary.xlsx”: Summary data of all the fossil sites used in the study. This is an MS Excel file and has three sheets, namely: a.     All_sites: This sheet lists various metadata related to each of the 39 fossil sites used in this study. The name of the site is listed as ‘Flora’, and each site has the following data associated with it: Epoch, Latitude Bin, Region, Geographic location, Lat(itude), Long(itude), Depositional.Environment, Age, Age.error, MAT.C (Mean Annual Temperature in degrees C), MAT.Error, MAP.mm.yr (Mean Annual Precipitation in mm), MAP.error, and No.Leaves (number of leaf specimens). b.     PEB sites list (Bighorn): This sheet specifically lists the 8 Paleocene-Eocene boundary (PEB) sites from the Bighorn basin along with relevant metadata. These sites are also present in the All_sites tab. c.     PEB sites list (Hanna): This sheet lists the 2 Hanna Basin sites from the PEB with relevant metadata. 2.     FOLDER “fossil site herbivory data”: This folder contains the leaf-level herbivory data from all the fossil sites used in this study (including the PEB sites from Hanna Basin) in .csv format. Each file has the following data structure: the first column lists the morphotaxa name of the leaf and the subsequent columns represent whether a particular DT (Damage Type, represented by individual column names) is present (1) or absent (0/NA) in that leaf. 3.     FOLDER “modern site herbivory data”: This folder contains the leaf-level level herbivory data from all the modern sites used in this study in .txt format. “presab_data_HFmatrix” is the data from the three sites in Harvard Forest, “presab_data_LSmatrix” from three sites in La Selva and “presab_data_SERCmatrix” from the three sites in the Smithsonian Environmental Research Center. The quarry number is the name of the site in each file. The rest of the structure is same as fossil data: the second column lists the taxa name for the leaf and the subsequent columns represent whether a particular DT (Damage Type, represented by individual column names) is present (1) or absent (0/NA) in that leaf. 4.     FOLDER “masks for FFGs”: This folder has two files, namely: a.     “ffgdef_DT.csv”: This file lists which Functional Feeding Group does each DT belong to. Oviposition =0, Skeletonization=1, Surface feeding =2, Galling=3, Hole Feeding=4, Mining =5, Margin Feeding =6,  Piercing and Sucking=7. b.    “mask_DT.csv”: This file lists whether a given DT is a herbivory damage, a specialized damage, gall or mining damage (T/F). 5.     FOLDER “N2_fixing_site_level_taxa”: This folder contains 8 files in .csv format corresponding to each of the 8 PEB Bighorn Basin sites. Each file has the same structure: the first column corresponds to a specific morphotaxa and the next column indicates whether it is a N2 fixing plant (1) or not (0). 6. FILE "Analyais_base.Rmd" gives base code to replicate all the results.

opencc-zeroApr 2024View details →

Vertical stratification of leaf physical traits exerts bottom-up pressures on insect herbivory in a sugar maple temperate forest

Do vertical gradients in temperate forest structure insect herbivore communities? We tested the hypothesis that the increase in light intensity from understory to forest canopy level drives differences in leaf physical traits and budburst phenology that impact insect herbivores and thus play a role in structuring both herbivore communities and the leaf damages they cause. Twelve sugar maple (Acer saccharum) sites were monitored in southern Quebec, examining insect herbivore patterns from understory to the shaded and sun canopy over the summers of 2020, 2021, and 2022. Additionally, we recorded leaf physical traits, temperature, humidity, and sun exposure. Our findings revealed that leaf thickness increased along the vertical gradient in 2021, making leaves less favorable to herbivores in the canopy level. Accordingly, we recorded a consistent decrease in insect herbivory damage rates from the understory to the shaded canopy and sun canopy in 2020 and 2021, driven by leaf cutters, skeletonizers, stipplers, and leaf miners. These results support our hypothesis that variation in plant physical traits due to sun exposure contributes to the vertical stratification of insect damage. In 2022, the gradient of insect herbivore abundance corroborated the observed damage trends from the previous years. Moreover, we calculated an average annual herbivory rate of 9.1% of the leaf surface in our study site, suggesting limited evidence supporting a significant contribution of background herbivory to the decline of sugar maple forests. Overall, our study highlights the importance of vertical gradients in structuring insect herbivore communities and emphasizes the role of leaf traits in mediating these interactions.

opencc-by-4.0Dec 2024View details →

Data on Trait diversity and spider community composition are associated with lower herbivory in young forest plantations

Open the record for dataset details and reuse information.

opencc-by-4.0Dec 2021View details →

Data for "Meta-analysis of induced anti-herbivore defence traits in plants from 647 manipulative experiments with natural and simulated herbivory"

Data used in analysis in "Meta-analysis of induced anti-herbivore defence traits in plants from 647 manipulative experiments with natural and simulated herbivory" in Journal of Ecology.  Code used for analysis are included as Supplementary Material of the main article.

opencc-zeroDec 2021View details →

Soil nitrogen mediates the effect of distance from climatic center on herbivory rates in a tropical herb

The center-periphery hypothesis predicts that species are most abundant at the center of their range. Differential herbivory rates between center and periphery populations can explain this variation in species abundance. However, if the geographic center of a species distribution coincides with its ecological optimum, the resource availability hypothesis predicts higher herbivory rates and tolerances at the center compared to the periphery. Biogeographic studies on herbivory have treated these two mechanisms separately, limiting our mechanistic understanding of the role of herbivory in shaping species range limits. We analyzed the role of resource availability on herbivory variation from center to periphery using data collected across the distribution of Thunberbia atacorensis, a range limited species of West Africa. We used two types of distances: geographic distance (the distance from each plot to the geographic center of all populations) and climatic distance (the distance from each plot to the preferendum of the species). We found no increase in herbivory toward the periphery of the climatic and geographic ranges. However, herbivory rates increased with soil nitrogen. Nitrogen in soil decrease from center to periphery of climatic range. Phylogenetic diversity and surrounding plants' competition did not affect herbivory rates. Our study provides insights into how nutrient limitation can shape species center-periphery distribution by altering spatial variation in herbivory rates.

opencc-zeroJan 2022View details →

Data from: Foliar herbivory creates subtle soil legacy effects that alter future herbivores via changes in plant community biomass allocation

Plants leave legacy effects in the soil they grow in, which can drive important vegetation processes, including productivity, community dynamics and species turnover. Plants at the same time also face continuous pressure posed by insect herbivores. Given the intimate interactions between plants and herbivores in ecosystems, plant identity and herbivory are likely to interactively shape soil legacies. However, the mechanisms that drive such legacy effects on future generations of plants and associated herbivores are little known. In a greenhouse study, we exposed ten common grasses and non-leguminous forbs individually to insect herbivory by two closely related noctuid caterpillars, Mamestra brassicae and Trichoplusia ni (Lepidoptera: Noctuidae) or kept them free of herbivores. We then used the soil legacies created by these plant individuals to grow a plant community composed of all ten plant species in each soil, and exposed these plant communities to M. brassicae. We measured conditioning plant biomass, soil respiration and chemistry of the conditioned soils, as well as individual plant, plant community and herbivore biomass responses. At the end of the conditioning phase, soils with herbivore legacies had higher soil respiration, but only significantly so for M. brassicae. Herbivore legacies had minimal impacts on community productivity. However, path models reveal that herbivore-induced soil legacies affected responding herbivores through changes in plant community shoot: root ratios. Soil legacy effect patterns differed between functional groups. We found strong plant species and functional group-specific effects on soil respiration parameters, which in turn led to plant community shifts in grass: forb biomass ratios. Soil legacies were negative for the growth of plants of the same functional group. Synthesis: We show that insect herbivory, plant species and their functional groups, all incur soil microbial responses that lead to subtle (herbivory) or strong (plants and their functional group) effects in response plant communities and associated polyphagous herbivores. Hence, even though typically ignored, our study emphasizes that legacies of previous insect herbivory in the soil can influence current soil-plant-insect community interactions.

opencc-zeroFeb 2022View details →

Aboveground herbivory causes belowground changes in twelve oak Quercus species: a phylogenetic analysis of root biomass and non‐structural carbohydrate storage

Plant ecosystem structure is understood to be a result of complex multitrophic interactions. Most multitrophic studies focus on plant aboveground adaptations to aboveground herbivore pressures, neglecting belowground adaptations in response to aboveground damage. Differential investment in root structures may allow plants to compensate for tissue loss or damage due to herbivores. Furthermore, phylogeny may constrain a plant's ability to adapt belowground. We examined the belowground responses of 12 species of oak (Quercus) to varying locations and intensities of simulated herbivore damage. We first established that oak belowground traits responded to aboveground herbivory by measuring patterns of investment in coarse vs fine root structures and re-allocation of non-structural carbohydrates (NSC) to root storage. We then tested whether phylogeny could explain variations in investment patterns using phylogenetic independent contrasts. Plant adaptations to aboveground herbivory included allocating biomass and carbon reserves to root structures, depending on the location and intensity of herbivore damage. NSC re-allocation to root storage was observed when oak species experienced any type of damage, but damage to lateral tissues caused a greater re-allocation than apical damage or control treatments. We found that most belowground responses to aboveground herbivory are species-specific and may be adapted for environmental conditions or type of herbivory. Some responses to herbivore damage, such as changes in fine-root mass and root sugar concentrations, were phylogenetically constrained. Phylogenetic constraints generally occur when there is severe damage at the apical meristem. Plants may adapt to aboveground tissue loss due to varying herbivore pressures (i.e. varying location and intensity of damage) by differentially investing in root types and NSC re-allocation to root storage. Understanding linkages between and phylogenetic constraints of plant belowground responses to aboveground herbivory will improve our understanding of the ecological processes involved in multitrophic interactions.

opencc-zeroDec 2021View details →

Fire and forage quality: post-fire regrowth quality and pyric herbivory in subtropical grasslands of Nepal

Indiscriminate fire is rampant throughout subtropical South and Southeast Asian grasslands. However, very little is known about the role of fire and pyric herbivory on the functioning of highly productive subtropical monsoon grasslands lying within Cwa-climatic region. We collected grass samples from 60 m x 60 m plots and determined vegetation physical and chemical properties at regular 30-day intervals from April to July 2020, starting from 30 days after fire to assess post-fire regrowth forage quality. We counted pellet groups for the same four months from 2 m x 2 m quadrats that were permanently marked with pegs along the diagonal of each 60 m x 60 m plot to estimate grazing intensity to the progression of post-fire regrowth. We observed strong and significant reductions in crude protein (mean value 9.1 to 4.1 [55% decrease]) and phosphorus (mean value 0.2 to 0.11 [45% decrease]) in forage collected during different time intervals i.e., from 30 days to 120 days after fire. Mesofaunal deer utilised the burned areas extensively for a short period, i.e., up to two months after fire when the burned areas contained short grasses with a higher level of crude protein and phosphorus. Grazing intensity of chital (Axis axis) to post-fire regrowth differed significantly over time since fire, with higher intensity of use at 30 days after fire. Grazing intensity of swamp deer (Rucervus duvaucelii) did not differ significantly until 90 days after fire, however, decreased significantly after 90 days since fire. Large-scale indiscriminate single event fires thus may not fulfil nutritional requirements of all species in mesofaunal deer community in these subtropical monsoon grasslands. We recommend for a spatio-temporal manipulation of fire to reinforce grazing feedback and to yield for the longest possible period a reasonably good food supply for the conservation of mesofaunal deer.

Reduced predation by arthropods and higher herbivory in burned Amazonian forests

Biodiversity losses have increased in tropical forests due to fire-related disturbances. As landscape fragmentation and climate change increase, fires will become more frequent and widespread across tropical rain forests worldwide, with important implications for forest dynamics by altering plant-animal interactions. Here we tested the hypothesis that recurrent fires in tropical rain forests change bottom-up and top-down forces controlling the abundance of insect herbivores, which in turn increases herbivory. To quantify herbivory, we collected 50 leaves per tree of five species in burned and unburned experimental plots (N = 75) in southeastern Amazonian forests. We measured leaf nitrogen content and leaf thickness of tree leaves as bottom-up factors that could explain differences in herbivory; we measured predation pressure on model caterpillars and estimated the abundance of predatory ants as top-down factors. We found higher herbivory in burned than in unburned forests, as well as lower predator attacks in caterpillar models and lower abundance of predatory ants. Leaf nitrogen content did not vary across treatments. Birds attacked model caterpillars more frequently in burned than in unburned forests, and leaf thickness was higher in burned forests, but these factors together were not enough to offset the higher herbivory in burned plots. Fire degrades tropical forests not only by killing trees and altering their structure and community dynamics, but also by reducing predatory arthropods and disrupting predator-prey interactions, which triggers increased herbivory. These indirect impacts of recurrent fires probably contribute to further alter forest structure, functioning, and to decrease forest regeneration in Amazonian forests.

Data for: Interactive effects of light and snail herbivory rather than nutrient loading determine early establishment of submerged macrophytes

Submerged macrophytes play a key role in maintaining a clear-water phase and promoting biodiversity in shallow aquatic ecosystems. Since their abundance has declined globally due to anthropogenic activities, it is important to include them in aquatic ecosystem restoration programs. Macrophytes establishment in early spring is crucial for the subsequent growth of other warm-adapted macrophytes. However, factors affecting this early establishment of submerged macrophytes have not been fully explored yet. Here, we conducted an outdoor experiment from winter to early spring using the submerged macrophytes Potamogeton crispus and Vallisneria spinulosa to study the effects of shading, nutrient loading, snail herbivory (Radix swinhoei) and their interactions on the early growth and stoichiometric characteristics of macrophytes. The results show that the effects strongly depend on macrophyte species. Biomass and number of shoots of P. crispus decreased, and internode length increased during low light conditions, but were not affected by nutrient loading. P. crispus shoot biomass and number showed hump-shaped responses to increased snail biomass under full light. In contrast, the biomass of the plant linearly decreased with snail biomass under low light. This indicates an interaction of light with snail herbivory. Since snails prefer grazing on periphyton over macrophytes, a low density of snails promoted growth of P. crispus by removing periphyton competition, while herbivory on the macrophyte increased during a high density of snails. The growth of V. spinulosa was not affected by any of the factors, probably because of growth limitation by low temperature. Our study demonstrates that the interaction of light with snail herbivory may affect establishment and growth of submerged macrophytes in early spring. Macrophyte restoration projects may thus benefit from lowering water levels to increase light availability and making smart use of cold-adapted herbivores to reduce light competition with periphyton.

Herbivory and traits of Lupinus polyphyllus

Glyphosate is the most widely used non-selective herbicide in the world. Glyphosate residues in soil can affect plant quality by modifying plant physiology, hormonal pathways, and traits, with potential consequences for plants' interactions with herbivores. We explored these indirect effects in the context of plant-herbivore interactions in a perennial, nitrogen-fixing herb. We quantified leaf herbivory for glyphosate-exposed and control plants grown in phosphorus-fertilised and non-fertilised soils, and assessed the impacts of glyphosate treatment on traits related to plant resistance against herbivores (leaf trichome density, leaf mass per area) and performance (aboveground biomass, root:shoot ratio, nodule number, nodule activity). Moreover, we conducted a laboratory feeding experiment to compare the palatability of leaves from glyphosate-exposed and control plants to a generalist mollusc herbivore. Herbivore damage and intensity in situ increased during the growing season regardless of glyphosate or phosphorus treatment. Glyphosate treatment reduced leaf trichome density, but had no effect on the other plant traits considered. Herbivore damage was negatively associated with leaf trichome density. The feeding experiment revealed no difference in the feeding probability of mollusc herbivores between glyphosate-exposed and control plants. However, there was an interaction between glyphosate treatment and initial leaf area for leaf consumption by herbivores: leaf consumption increased with increasing leaf area in both groups, but at a lower rate for glyphosate-exposed plants than for control plants. Our results show that glyphosate residues in soil have the potential to indirectly affect aboveground herbivores through changes in leaf quality, which may have mixed consequences for folivore damage.

Insect herbivory for Catula gettyi, a late Cretaceous laurel from Utah, USA

The Upper Cretaceous (Campanian Stage) Kaiparowits Formation of southern Utah, USA, preserves abundant plant, invertebrate, and vertebrate fossil taxa. Taken together, these fossils indicate that the ecosystems preserved in the Kaiparowits Formation were characterized by high biodiversity. Hundreds of vertebrate and invertebrate species and over 80 plant morphotypes are recognized from the formation, but insects and their associations with plants are largely undocumented. Here, we describe a new fossil leaf taxon, Catula gettyi gen et. sp. nov. in the family Lauraceae from the Kaiparowits Formation. Catula gettyi occurs at numerous localities in this deposit that represent ponded and distal floodplain environments. The type locality for C. gettyi has yielded 1,564 fossil leaf specimens of this species, which provides the opportunity to circumscribe this new plant species. By erecting this new genus and species, we are able to describe ecological associations on C. gettyi and place these interactions within a taxonomic context. We describe an extensive archive of feeding damage on C. gettyi caused by herbivorous insects, including more than 800 occurrences of insect damage belonging to five functional feeding groups indicating that insect-mediated damage on this taxon is both rich and abundant. Catula gettyi is one of the best-sampled host plant taxa from the Mesozoic Era, a poorly sampled time interval, and its insect damage is comparable to other Lauraceae taxa from the younger Late Cretaceous Hell Creek Flora of North Dakota, USA.

opencc-zeroAug 2022View details →

Invasive plant species that experience lower herbivory pressure may evolve lower diversities of chemical defence compounds in the exotic range

ABSTRACT PREMISE Invasive plant species often escape from specialist herbivore species and are likely to experience herbivory mostly from generalist herbivore species in the exotic range. Consequently, the Shifting Defence Hypothesis (SDH) predicts that invasive plants will express higher concentrations of qualitative defence compounds to deter dominant generalist herbivores in the exotic range. Here, I additionally propose a Reduced Chemical Diversity Hypothesis (RCDH), which predicts that reduced herbivory pressure will select for invasive plant genotypes that produce lower diversities of defence compounds in the exotic range. METHODS I tested whether: (1) Invasive Brassica nigra populations express a lower diversity and an overall higher concentration of glucosinolate compounds than native-range B. nigra; (2) Brassica nigra individuals that express high diversities and concentrations of glucosinolates are more attractive to specialist and deterrent to generalist herbivores; (3) Tissues of invasive B. nigra are less palatable to two generalist herbivores Theba pisana and Helix aspersa than tissues of native-range B. nigra. RESULTS Invasive B. nigra populations expressed a significantly lower diversity of glucosinolate compounds and a marginally higher concentration of total glucosinolate compounds. Leaf tissues of the invasive B. nigra were significantly less palatable to T. pisana and marginally less so to H. aspersa. Brassica nigra individuals that expressed high concentrations of total glucosinolate compounds were visited by a low diversity of generalist herbivore species in the field. CONCLUSIONS The biogeographical differences in glucosinolate profiles of invasive and native-range populations of B. nigra may be the result of differential herbivore selection pressures in the respective ranges.