Effects of plant pathogens on population dynamics and community composition in grassland ecosystems: two case studies

Abstract

Grassland ecosystems comprise a major portion of the earth's terrestrial surface, ranging from high-input cultivated monocultures or simple species-mixtures to relatively unmanaged but dynamic systems. Plant pathogens are a component of these systems with their impact dependent on many interacting factors, including grassland species population dynamics and community composition, the topics covered in this paper. Plant pathogens are affected by these interactions and also act reciprocally by modifying their nature. We briefly review these features of disease in grasslands and then introduce the 150-year long-term Park Grass Experiment (PGE) at Rothamsted Research in the UK. We then consider in detail two plant-pathogen systems present in the PGE, Tragopogon pratensis-Puccinia hysterium and Holcus lanata-Puccinia coronata. These two systems have very different life history characteristics: the first, a biennial member of the Asteraceae infected by its host-specific, systemic rust; the second, a perennial grass infected by a host-nonspecific rust. We illustrate how observational, experimental and modelling studies can contribute to a better understanding of population dynamics, competitive interactions and evolutionary outcomes. With Tragopogon pratensis-Puccinia hysterium, characterised as an "outbreak" species in the PGE, we show that pathogen-induced mortality is unlikely to be involved in host population regulation; and that the presence of even a short-lived seed-bank can affect the qualitative outcomes of the host-pathogen dynamics. With Holcus lanata-Puccinia coronata, we show how nutrient conditions can affect adaptation in terms of host defence mechanisms, and that coexistence of competing species affected by a common generalist pathogen is unlikely.

A Multiscale Approach to Plant Disease Using the Metacommunity Concept

“…Soil calcium levels were also shown to mediate interactions between yellow star thistle, Centaurea solstitialis, its foliar pathogen, and three insect seed predators (130). Nutrient conditions were also shown to affect adaptation of host defense mechanisms in the interaction between the perennial grass Holcus lanatus and its rust pathogen, Puccinia coronata, in the 150-year-long Park Grass Experiment in the United Kingdom (63). Thus, nutrients can modify host defenses, nutrient supply to pathogens, and spatial structuring of hosts in the landscape, highlighting the links between variation in environmental nutrient supply and the local and long-distance transmission of pathogens.…”

A long‐term study of burning effects on a plant pathogen in tallgrass prairie

“…When considering disease dynamics across larger spatial extents, many other factors may come into play Plant Pathology (2017) 66, 1308-1317 ( Fig. 1; Mitchell Jeger et al, 2014). For example, the abundance of both primary (Carex spp.)…”

Climate change and disease in plant communities

“…This impact may seem to be more limited to forest trees and other longer-lived species that remain present, and recordable, long after death than for herbaceous species that disappear quickly, leaving no evidence of their previous existence. Yet, careful studies provide a clear picture of pathogens affecting the size [22,23] and genetic structure of individual host populations [24] and that greater host diversity leads to reduced disease impact and pathogen evolution [25,26]. This is the situation today-what of the future?…”