Fletcher Halliday

@fletcher-h.bsky.social

1507 Followers 679 Following

Disease Ecology. Biodiversity. Global Change. PI of the Disease Ecology and Diversity Lab at Oregon State University https://agsci-labs.oregonstate.edu/diseaseecology/

Full grown Saguaros stand as solitary sentinels watching over the desert, but young Saguaros require help and protection to achieve this state. 'Nurse trees' are trees like palo verdes, mesquites, and ironwoods that help 'nurse' the young cacti. This means that they give the baby saguaros a chance at a good start by providing a better microclimate with shade, better soil, and a degree of protection during their young susceptible years. Eventually the grown Saguaros outlive their nurse plants to become the mature solitary cacti you see.
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 '+/−').
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).
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."
Here's a photo of my favorite grass host, Dactylis glomerata, infected with ergot and stem rust in the beautiful Swiss Alps
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)
Title and abstract of Straud et al 2024 TREE. Priority effects transcend scales and disciplines in biology.