Spatially complex neighboring relationships among grassland plant species as an effective mechanism of defense against herbivory

Abstract

Close spatial relationships between plant species are often important for defense against herbivory. The associational plant defense may have important implications for plant community structure, species diversity, and species coexistence. An increasing number of studies have focused on associational plant defense against herbivory at the scale of the individual plant and its nearest neighbors. However, the average neighborhood effects between plant species at the scale of whole plant communities have received almost no attention. The aims of this study were to determine patterns of spatial relationship between different plant species that can provide effective defense against herbivory. We conducted a manipulative experiment using sheep and three native plant species with different palatability. Consumption of palatable plants by herbivores was largest when the three plant species were isolated in three patches and independent of each other. A homogenous and spatially equal neighbor relationship between the three species did not reduce the risk of herbivory of palatable species compared to isolation of these species, but it reduced the total intake of all plant species. The palatable species was subject to less herbivory in a complex spatial neighborhood of several plant species. High complexity of spatial neighborhood resulted in herbivores passively reducing selectivity, thereby reducing the probability of damage to palatable species in the community, or making inaccurate judgments in foraging selectivity between and within patches, thereby reducing the vulnerability of palatable plants and even the whole plant community. We conclude that compelling herbivores to passively reduce the magnitude of foraging selectivity by establishing spatially complex neighborhoods between plant species is a compromise and optimal spatial strategy by plants to defend themselves again herbivory. This may contribute not only to maintenance of plant species diversity but also to a stable coexistence between herbivores and plants in grassland ecosystems.

Interactive effects of large herbivores and plant diversity on insect abundance in a meadow steppe in China

“…The difference in plant species diversity is a typically important characteristic of heterogeneity, and diverse plant communities can markedly affect foraging strategies of large herbivores and their concomitant impacts on the dynamics of vegetation itself (Bergvall et al, 2006;Miller et al, 2007;Wang et al, 2011). Our previous work found that complex spatial neighborhood of several plant species makes the palatable species for herbivores to less selected, contributing to the maintenance of plant diversity (Wang et al, 2010). This 'plant species diversity disaffinity' may be an important factor influencing subsequent herbivores' impacts on plant community, which, in turn, consequently impacts insect community.…”

Vegetation richness, height, coverage and spatial distribution mediate grasshopper abundance in the upper reaches of Heihe River, China

“…It was a big challenge to predict that the heterogeneity of grasshopper patches are critical factors that influenced by foraging selectivity and habitat heterogeneity.This study finds that grasshopper population was good at selecting a micro-environment to a dwelling. The semivariable function of grasshopper abundance and vegetation community were a nonlinear model in geostatistics; while in ecology, the curves meant that the spatial distribution pattern was aggregated (Wang, et al 2010;Zhong, et al 201r). The grasshopper abundance typically produces spacial heterogeneity with larger range and nuggets than vegetation community (except the range of vegetation coverage in model).…”

Plants Can Benefit from Herbivory: Stimulatory Effects of Sheep Saliva on Growth of Leymus chinensis

“…L. chinensis is a perennial rhizomatous grass with good palatability and high forage value [8], [40], [41], [42], [43], [44]. It is widely distributed in the eastern region of the Eurasian steppe zone as a dominant species from arid to semi-arid steppes in northern China and eastern Mongolia, and it has extensive plasticity in morphological and physiological characteristics.…”