Disease in Natural Plant Populations, Communities, and Ecosystems: Insights into Ecological and Evolutionary Processes

Abstract

Pathogens are associated with virtually all plant species, from a diverse array of habitats. Although we know the most about diseases of economically important plants, the goal of this article is to describe current work on host-pathogen interactions in natural or unmanaged systems outside of the crop field or forestry plantation. Agricultural scientists, of course, have contributed to this research. For example, disease resistance genes are often discovered as a result of surveys of wild relatives of crop plants, and it is well known that crop disease levels can be influenced by diseases in nearby weeds. Starting in the late 1970s, however, research on natural plant-pathogen interactions began to both increase and diversify, with an explicit goal of understanding the ecology and evolution of these interactions. This article will trace the history of this young discipline and provide highlights of ongoing research areas. I will focus on work by ecologists and evolutionary biologists that often is not published in plant pathology or forestry journals.A first step is to define a natural system as opposed to an agricultural or human-managed system. In contrast to most row crops, most natural populations occur in complex spatial arrangements with tens to hundreds of other species, are genetically diverse, and consist of plants of different ages and developmental stages. Seeds produced by a population in one year are the source of future generations at the site. Natural populations need not be pristine; as defined above, roadside weeds are as natural as prairie wildflowers. This natural versus agricultural dichotomy is also, of course, simplistic. Forest plantations and pasture landscapes have many natural attributes, and the degree of distinction between agricultural and natural ecosystems varies around the world.Although there have always been researchers intrigued by the role of pathogens in nature (58), publications in the 1970s and 1980s were influential in introducing the study of plant disease to ecologists and evolutionary biologists. For example, John Harper, a British biologist, published a landmark book in 1977 called Population Biology of Plants (61). This large tome (892 pages) encouraged ecologists to view plants not as vegetation, but as populations of individuals. One of his 17 chapters was titled "Pathogens" and emphasized the effect that disease could have on the structure and dynamics of plant populations and communities. Harper's book was followed a decade later by Jeremy Burdon's 1987 book Diseases and Plant Population Biology (30). Burdon expanded on the ecological consequences of disease and also emphasized genetic interactions between host and pathogen. Both Harper and Burdon emphasized the relevance of crop research and theories developed in an agricultural context, such as van der Plank's (101) work in epidemiology and Flor's gene-for-gene hypothesis (50). Interestingly, at the same time period, several plant pathologists were discussing disease in natural systems (130). Browning (29), in pa...

Higher plant diversity promotes higher diversity of fungal pathogens, while it decreases pathogen infection per plant

“…However, these single-host-single-pathogen studies cannot cover the species diversity and spatial complexity of natural plant assemblages (Mundt et al 2011). Thus, the characterization of multi-host-multipathogen associations is needed to comprehensively understand biotic and abiotic interactions to reliably predict pathogen infections of natural communities under changing species diversity , Alexander 2010.…”

“…Thus, plant communities may differentially affect the presence, infection, and diversity of plant pathogens (Keesing et al 2010, Scherber et al 2010a) via abundance and spatial distribution of susceptible and resistant genotypes, and of structural three-dimensional space-filling components (Garrett and Mundt 1999, Altizer et al 2003, Alexander 2010, King and Lively 2012. Plant community diversity can affect both pathogen communities and host-pathogen dynamics (Mitchell et al 2002, Ferrer and Gilbert 2003, Mitchell 2003, Keesing et al 2006, 2010.…”

Phylogenetic structure and host abundance drive disease pressure in communities

“…Plant pathogens can be important drivers of community diversity, structure and dynamics 1,2,10,11 . A basic premise of epidemiology is that pathogen transmission often increases with host density 12,13 .…”

Identification of <i>Alternaria</i> spp. as Pathogenic on the Native Species <i>Terminalia australis</i> and <i>Salvia guaranitica</i>

“…Pathogens are associated with virtually all plant species, from a diverse array of habitats. Although we know the most about diseases of economically important plants, insufficient research has been focused on the host-pathogen interactions in natural or unmanaged systems outside of the crop field or forestry plantation [26]. So as to learn more about diseases of native plants in the area, a cooperative project was signed between ARN and the Department of Plant Pathology, School of Agronomy, University of Buenos Aires, in 2010.…”