Biology subjects

Penczykowski, R. M.

Publications and source records attributed to Penczykowski, R. M..

4 recordsLinked to original sources

bioRxiv2024

Local adaptation of a fungal pathogen to temperature along a latitudinal gradient

Whether climate warming will increase or decrease prevalence of an infectious disease partly depends on the potential for pathogens to adapt to higher temperatures. This potential can be assessed by investigating regional variation in pathogen thermal performance and testing for local adaptation to current temperature regimes and host populations. We collected seeds of a host plant (Plantago rugelii, a perennial herb) and isolated strains of its specialist fungal pathogen (Golovinomyces sordidus, a powdery mildew) from five locations along a latitudinal transect from southern Mississippi to northern Wisconsin, USA. In a laboratory experiment, we placed sympatric and allopatric host-pathogen pairings into seven temperature treatments from 7 to 33 {degrees}C. We fitted thermal performance curves to pathogen growth data for each strain. Pathogen strains were locally adapted to temperature, with estimated thermal optima ranging from 20.6 {degrees}C (southernmost strain) to 16.7 {degrees}C (second-northernmost strain) and generally decreasing 0.26 {degrees}C for each degree increase in latitude of origin. However, there was no evidence of pathogen local adaptation to sympatric hosts. Given that powdery mildew spores can disperse long distances via wind, our results suggest that northward spread of warm-adapted strains could facilitate pathogen adaptation to warming climates in this and similar systems.

ecology↗

bioRxiv2022

Urbanization alters phenology of plant reproduction, foliar infection, and herbivory

O_LIUrbanization involves numerous environmental changes that may affect the timing of plant reproduction and foliar damage by pathogens, herbivores, and human activities. Yet such relationships have not been examined simultaneously in plant populations across levels of urbanization. C_LIO_LIWe conducted monthly surveys of 22 populations of Plantago lanceolata and P. rugelii in parks spanning an urbanization gradient. We quantified plant reproductive development and prevalence of powdery mildew infection, insect herbivory, and mowing damage. Additionally, we placed potted "sentinel" plants into field populations to directly measure infection and herbivory rates. C_LIO_LIUrbanization was associated with earlier flowering and more seed production for P. rugelii, but less seed maturation for P. lanceolata. Mildew epidemics on P. rugelii started earlier and achieved greater prevalence in more urban sites. Correspondingly, sentinels only became infected in suburban and urban sites. There was less infection on P. lanceolata, including sentinels, suggesting low availability of pathogen genotypes able to infect this species. Early-summer herbivory on both plant species was accelerated in urban sites. C_LIO_LIUrbanization has species-specific associations with reproductive phenology and is associated with increased early-summer herbivory, larger epidemics of a foliar pathogen, and more mowing damage on two weedy herbs C_LI

ecology↗

bioRxiv2020

Virulent disease epidemics can increase host density by depressing foraging of hosts

All else equal, parasites that harm host fitness should depress densities of their hosts. However, parasites that alter host traits may increase host density via indirect ecological interactions. Here, we show how depression of infected host foraging rate can produce such a hydra effect. Using a foraging assay, we quantified reduced foraging rates of a zooplankton host infected with a virulent fungal parasite. We then parameterized a dynamical model of hosts, parasites, and resources with this foraging function, showing how foraging depression can create a hydra effect. Mathematically, the hydra arose when increased resource productivity exceeded any increase in resource consumption per host. Therefore, the foraging-mediated hydra effect more likely emerged (1) for hosts which strongly control logistic-like resources and (2) during larger epidemics of moderately virulent parasites. We then analyzed epidemics from 13 fungal epidemics in nature. We found evidence for a foraging-mediated hydra effect: large outbreaks depressed foraging rate and correlated with increased densities of both algae and hosts. Therefore, depression of foraging rate of infected hosts can produce higher host densities even during epidemics of parasites that increase host mortality. Such hydras might prevent collapse of host populations but also could produce higher densities of infected hosts.Competing Interest StatementThe authors have declared no competing interest.View Full Text

ecology↗

bioRxiv2020

Facilitative priority effects drive parasite assembly under coinfection

Host individuals are often coinfected with diverse parasite assemblages, resulting in complex interactions among parasites within hosts. Within hosts, priority effects occur when the infection sequence alters the outcome of interactions among parasites. Yet, the role of host immunity in this process remains poorly understood. We hypothesized that the host response to first infection could generate priority effects among parasites, altering the assembly of later arriving strains during epidemics. We tested this by infecting sentinel host genotypes of Plantago lanceolata with strains of the fungal parasite, Podosphaera plantaginis, and measuring susceptibility to subsequent infection during experimental and natural epidemics. In these experiments, prior infection by one strain often increased susceptibility to other strains, and these facilitative priority effects altered the structure of parasite assemblages, but this effect depended on host genotype, host population, and parasite genotype. Thus, host genotype, spatial structure, and priority effects among strains all independently altered parasite assembly. Then, using a fine-scale survey and sampling of infections on wild hosts in several populations, we identified a signal of facilitative priority effects, which altered parasite assembly during natural epidemics. Together, these results provide evidence that within host priority effects by early arriving strains can drive parasite assembly, with implications for how strain diversity is spatially and temporally distributed during epidemics.

ecology↗