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Papers by Keith Clay

Periodical cicada emergences in the eastern United States are one of the largest biomass fluctuat... more Periodical cicada emergences in the eastern United States are one of the largest
biomass fluctuations in the world, providing a unique opportunity to study if a root parasite
can affect broad-scale patterns of forest growth and succession. We used dendrochronology to
examine the direct effect of Brood X (17 y cicada) and Brood XXIII (13 y cicada) periodical
cicadas on 89 individual trees from five species (Acer saccharum, Fraxinus americana, Quercus
palustris, Q. velutina and Sassafras albidum) in Indiana. Standard dendrochronological
techniques were used to date the tree-ring samples and our chronologies ranged from 63–
98 y in age, spanning from four to eight cicada emergences. We removed the main climate
variable from each species chronology by conducting a regression analysis and using the
residuals for the remainder of the analysis. Significant climate models were developed for all
five species. Acer saccharum growth correlated highest with Jun. temperature (r 5 20.392),
Fraxinus americana growth correlated with summer Palmer Drought Severity Index (PDSI) (r
5 0.338), Quercus palustris growth correlated with summer precipitation (r 5 0.366), Q.
velutina growth correlated with Jul. PDSI (r 5 0.527) and Sassafras albidum growth correlated
the highest with Jun. precipitation (r 5 0.406). A superposed epoch analysis was used to
examine the effect of periodical cicadas on each tree species before, during and after
multiple emergences on the stand level. No effect from root parasitism prior to emergence
was evident in any of the species, but three of the species chronologies showed a significant
reduction in growth the year of or the year after the emergence year. Three chronologies
showed an increase in growth 5 y following the cicada emergence event.

Frontiers in Microbiology, 2015

Background/Question/Methods Parasites and pathogens do not infect all hosts equally. Heterogeneit... more Background/Question/Methods Parasites and pathogens do not infect all hosts equally. Heterogeneity within a host community can be caused by host species, sex, and previous exposure to infectious agents. Differences in host immune response have been proposed as a mechanism for heterogeneity in parasite distribution on hosts. We studied small mammal hosts and tick vectors to investigate interactions between host immune function and ectoparasite load. Two hypotheses that could explain observed relationships are: 1) hosts with lower immune function will have higher ectoparasite burden due to reduced ability to mount a response, and 2) hosts with higher immune function will have higher ectoparasite burden due to high investment in immune function. We live-trapped white-footed mice (Peromyscus leucopus) and prairie voles (Microtus ochrogaster) at eight sites in southern Indiana. We collected ticks and blood samples from each individual to relate host immune function to ectoparasite load. ...

Mycologia, Jan 14, 2015

Periglandula ipomoeae and P. turbinae (Ascomycota, Clavicipitaceae) are recently described fungi ... more Periglandula ipomoeae and P. turbinae (Ascomycota, Clavicipitaceae) are recently described fungi that form symbiotic associations with the morning glories (Convolvulaceae) Ipomoea asarifolia and Turbina corymbosa, respectively. These Periglandula species are vertically transmitted and produce bioactive ergot alkaloids in seeds of infected plants and ephemeral mycelia on the adaxial surface of young leaves. Whether other morning glories that contain ergot alkaloids also are infected by Periglandula fungi is a central question. Here we report on a survey of eight species of Convolvulaceae (Argyreia nervosa, I. amnicola, I. argillicola, I. gracilis, I. hildebrandtii, I. leptophylla, I. muelleri, I. pes-caprae) for ergot alkaloids in seeds and associated clavicipitaceous fungi potentially responsible for their production. All host species contained ergot alkaloids in four distinct chemotypes with concentrations of 15.8-3223.0 μg/g. Each chemotype was a combination of four or five ergot ...

Journal of Applied Ecology, 2015

ABSTRACT While many ecosystems depend on fire to maintain biodiversity, non-native plant invasion... more ABSTRACT While many ecosystems depend on fire to maintain biodiversity, non-native plant invasions can enhance fire intensity, suppressing native species and generating a fire–invasion feedback. These dynamics have been observed in arid and semi-arid ecosystems, but fire–invasion interactions in temperate deciduous forests, where prescribed fires are often used as management tools to enhance native diversity, have rarely been investigated.Here we evaluated the effects of a widespread invasive grass on fire behaviour in eastern deciduous forests in the USA and the potential effects of fire and invasions on tree regeneration. We planted native trees into invaded and uninvaded forests, quantified fuel loads, then applied landscape-scale prescribed fires and no-burn controls, and measured fire behaviour and tree seedling and invasive plant performance.Our results show that fires in invaded habitats were significantly more intense, including higher fire temperatures, longer duration and higher flame heights, even though invasions did not alter total fuel loads. The invasion plus fire treatment suppressed native tree seedling survival by 54% compared to invasions without fire, and invasions reduced natural tree recruitment by 66%.We also show that invasive plant biomass did not change from one season to the next in plots where fire was applied, but invader biomass declined significantly in unburned reference plots, suggesting a positive invasive grass–fire feedback.Synthesis and applications. These findings demonstrate that fire–invasion interactions can have significant consequences for invaded temperate forest ecosystems by increasing fire intensity and reducing tree establishment while promoting invasive plant persistence. To encourage tree regeneration and slow invasive spread, we recommend that forest managers remove invasions prior to applying prescribed fires or avoid the use of fire in habitats invaded by non-native grasses.

Molecular ecology, Jan 2, 2015

High-throughput sequencing is revealing that most macro-organisms house diverse microbial communi... more High-throughput sequencing is revealing that most macro-organisms house diverse microbial communities. Of particular interest are disease vectors whose microbiome could potentially affect pathogen transmission and vector competence. We investigated bacterial community composition and diversity of the ticks Dermacentor variabilis (n = 68) and Ixodes scapularis (n = 15), and blood of their shared rodent host, Peromyscus leucopus (n = 45) to quantify bacterial diversity and concordance. The 16S rRNA gene was amplified from genomic DNA from field-collected tick and rodent blood samples and 454 pyrosequencing was used to elucidate their bacterial communities. After quality control, over 300,000 sequences were obtained and classified into 118 Operational Taxonomic Units (OTUs, clustered at 97% similarity). Analysis of rarefied communities revealed that the most abundant OTUs were tick species-specific endosymbionts, Francisella and Rickettsia, and the commonly flea-associated bacterium Ba...

The Quarterly Review of Biology, 1990

Journal of Medical Entomology, 2008

In total, 394 questing adult blacklegged ticks, Ixodes scapularis Say (Acari: Ixodidae), collecte... more In total, 394 questing adult blacklegged ticks, Ixodes scapularis Say (Acari: Ixodidae), collected at four sites were analyzed by polymerase chain reaction (PCR) for Þve microbial species: Anaplasma phagocytophilum, Babesia microti, Babesia odocoilei, Borrelia burgdorferi, and the rickettsial I. scapularis endosymbiont. Identities of genetic variants of A. phagocytophilum were determined by se- quencing a portion of the 16S DNA. In

Journal of Medical Entomology, 2006

Journal of Medical Entomology, 2013

Biogeosciences Discussions, 2014

Acta Oecologica-international Journal of Ecology, 2010