Fletcher Halliday
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fletcher-h.bsky.social
Fletcher Halliday
@fletcher-h.bsky.social
1.5K followers 660 following 26 posts
Disease Ecology. Biodiversity. Global Change.
PI of the Disease Ecology and Diversity Lab at Oregon State University https://agsci-labs.oregonstate.edu/diseaseecology/
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fletcher-h.bsky.social
But then we started to notice some key similarities among these hypotheses. Despite differences in life histories, terminology, direction, and magnitude, these hypotheses seem to share at least one of five non-exclusive fundamental factors mediating the impact of biodiversity on consumer damage.
A hypothetical causal model of biodiversity–consumer interactions derived from five, non-mutually exclusive fundamental factors that ultimately drive consumer damage: (1) density of a focal plant, (2) total plant biomass, (3) plant neighborhood quality, (4) resource diversity, and (5) structural complexity. The objective of this model is to highlight the important connections between these five factors and various hypotheses regarding biodiversity–consumer relationships, while more complex submodels are presented in the path column of Table 1. Paths a–e represent the causal effects of plant diversity on the five factors, while paths f–s represent the effects of these factors on consumer damage. The paths in the left side of the model allow biodiversity–consumer relationships to be linked to fundamental ecological ideas, including (a) substitutive or additive plant community assembly, (b) biodiversity–productivity relationships, (c) directional species loss or gain, (d) plant heterogeneity, and (e) niche complementarity. Similarly, the paths on the right side of the model can be linked to the proximate mechanisms through which those paths impact consumer abundance, as described in the table. Green letters correspond to the herbivory literature, whereas pink letters correspond to the disease literature. Blue arrows represent uniformly positive hypothesized relationships (also indicated by a '+' symbol), orange arrows represent uniformly negative relationships (indicated by a '−' symbol), and black arrows represent relationships that are either positive or negative (indicated by '+/−').
April 22, 2025 at 9:32 PM
fletcher-h.bsky.social
First, we organized published hypotheses linking changing diversity to consumer damage across consumer groups - this was a big task! Not surprisingly, there are a lot of hypotheses (>20) and they differ in terminology across consumer groups. I left this exercise feeling quite overwhelmed.
A table of hypotheses linking changing diversity to consumer damage grouped by consumer type (herbivore vs pathogen) and the expected direction of the relationship (monotonic increase in damage with increasing diversity vs monotonic decrease).
April 22, 2025 at 9:32 PM
fletcher-h.bsky.social
Pathogens and herbivores differ in key life history characteristics, and we expected that these might drive differences in terminology, patterns, and hypotheses in the published literature.
Figure 1 from our paper showing biological differences in life-history traits (bold text) across above- and belowground compartments for pathogenic and herbivorous consumer groups. some consumers (i.e., leaf miners and parasitic nematodes) exhibit traits that span both categories. The bold text for pathogens reads: "span a wider taxonomic breadth (viruses, bacteria, and multi-cellular eukaryotes), limited host choice, may require vectors, fast reproduction". The text for herbivores reads: "span a narrower taxonomic breadth (restricted to animals), consumed by predators, movement, range in body size, host choice."
April 22, 2025 at 9:32 PM
fletcher-h.bsky.social
Please spread the word - I am looking for a postdoc to join my lab at @osubpp.bsky.social to study diversity and interactions of plants and pathogens in wild and working landscapes!

More information here: agsci-labs.oregonstate.edu/diseaseecolo...
Here's a photo of my favorite grass host, Dactylis glomerata, infected with ergot and stem rust in the beautiful Swiss Alps
February 4, 2025 at 12:55 AM
fletcher-h.bsky.social
Interested in field ecology, genomics, and infectious diseases? Want to live in the beautiful Pacific Northwest? Then this job might be for you! We will start reviewing applications on 22 November and hope to have the position filled by the new year.
The grass, Dactylis glomerata, infected with a few different pathogens in the foreground with mountains and a rainbow in the background. Some of the work in our lab involves studying diseases in this plant across environmental gradients. Can you name both pathogens in the picture (hint - one is restricted to flowers and seeds and the other mostly infects the stems)
November 17, 2024 at 5:04 PM
fletcher-h.bsky.social
What an honor to be part of this new synthesis paper on priority effects. Priority effects are everywhere, but research on them remains incredibly siloed. Here’s our first attempt to reduce barriers between disciplines.

Read the article for free here: authors.elsevier.com/a/1inWTcZ3X0...
Title and abstract of Straud et al 2024 TREE. Priority effects transcend scales and disciplines in biology.
March 19, 2024 at 6:18 PM
fletcher-h.bsky.social
Join me!! Our department is looking to hire two(!) new assistant professors: (1) plant-microbe interactions and (2) population and disease dynamics of cereal pathogens.

Our department is dynamic and fun, our building is newly renovated, and Oregon is wonderful! bpp.oregonstate.edu/bpp/about/op...
December 11, 2023 at 11:03 PM
fletcher-h.bsky.social
My lab (blogs.oregonstate.edu/diseaseecolo...) is looking for a postdoc to study host and pathogen diversity and interactions at the interface of wild and working landscapes in Oregon! Come and join us! gradschool.oregonstate.edu/sites/gradsc...
November 20, 2023 at 6:28 PM