Pathogen Impact on Sexual vs. Asexual Reproductive Success in Arisaema Triphyllum

Abstract

Populations of Arisaema triphyllum commonly harbor a systemic fungal pathogen, Uromyces ari‐triphylli, which reduces leaf area and leaf longevity. Infected plants produced 42% fewer asexual progeny (cormlets). Furthermore, all asexual progeny from infected parents were themselves infected with Uromyces. Mean seed production of infected plants was only 21% of that among healthy plants. A hand pollination experiment demonstrated that 1) infected male plants can produce viable pollen, 2) the low seed production of naturally pollinated infected females was not due to inadequate pollination, and 3) seed production among healthy female plants was strongly pollinator limited. Seeds from infected and healthy parents had similar viability, and all seeds germinating from both types of parents were uninfected. The contrast in disease transmission to sexual vs. asexual progeny suggests that pathogen attack may be one selective factor favoring sexual reproduction in A. triphyllum populations.

Pollen Limitation of Plant Reproduction: Pattern and Process

“…Changes in the abundance of plant enemies (e.g., herbivores, pathogens, nectar robbers), plant mutualists (e.g., mycorrhizal fungi), and pollinator enemies (predators) may all affect interactions between plants and pollinators and thus the magnitude of pollen limitation (Table 1). Whereas many studies have factorially manipulated plant enemies and pollen receipt (Bertness & Shumway 1992, Garcia & Ehrlen 2002, Holland 2002, Juenger & Bergelson 1997, Krupnick & Weis 1999, Lehtila & Syrjanen 1995, Mizui & Kikuzawa 1991, Mothershead & Marquis 2000, only Parker (1987) found a significant interaction; enemies decreased the magnitude of pollen limitation. Other interacting species in the community have received much less attention and should be the target of future empirical work.…”

The Role of Natural Enemies in the Expression and Evolution of Mixed Mating in Hermaphroditic Plants and Animals

“…Alternatively, enemies may reduce plant resources, such that reproduction is resource limited rather than pollen limited. For example, Parker (1987) demonstrated that healthy Arisaema triphyllum plants were strongly pollen limited whereas those infected with Uromyces were not, most likely because the infected plants did not have the resources to allocate to maturing more seeds. Future empirical studies should expand this work to understand the evolutionary consequences for mating system of these enemy‐induced changes in pollen limitation and mate availability.…”

“…Sexually transmitted diseases are ubiquitous among animals (Morand 1993;Morand and Faliex 1994;Lockhart et al 1996;Knell and Webberley 2004). In plants, enemies transmitted among flowers by pollinating agents (e.g., bees, wind) are considered sexually transmitted (Parker 1992;Kaltz and Schmid 1995;Antonovics 2005). Wolf et al (unpubl.…”

Impact of a Pollinator-Transmitted Disease on Reproduction in Healthy Silene Acaulis

“…Fungal pathogens that severely affect plant reproduction have been suggested to be a potentially important factor in the evolution of a host's reproductive system (Levin 1978, Clay 1991, Antonovics 1992. A few studies have shown differences between diseased and healthy plants in the amount of selfed vs. outcrossed seed or asexual vs. sexual progeny produced (Clay 1984, Parker 1987. Pathogens would also influence the breeding system of healthy plants (1) if differences in infection rates existed between sexual morphs or male and female phases, (2) if differences DEBORAH L. MARR in fitness costs existed between female and male function (e.g., pollen dispersal is affected more than seed production), or (3) if pollen limitation is greater in populations with diseased individuals.…”