Figure Legends
Figure 1. Experimental design and timelines for the diet
manipulation and diet selection studies. In the first experiment, zebra
finches were given one of three diet treatments that varied in protein
and lipid content and blood and fecal samples were collected to assess
how diet influenced complement activity, baseline and stress-induced
corticosterone concentrations, and the gut microbiome. In the second
experiment, we simulated an infection in established zebra finch pairs
using the bacterial endotoxin lipopolysaccharide (LPS), and quantified
feeding behavior in immune challenged and control individuals, as well
as birds housed near either a control pair (no immune threat), or birds
housed near a pair given an immune challenge with LPS (social cue of
heightened infection risk). To investigate how a direct and perceived
immune threat shape macronutrient feeding preferences, we created two
isocaloric diets with varied lipid and protein ratios and quantified how
much of each diet birds consumed. Fecal samples were collected from all
individuals to assess changes in gut microbiota and blood samples were
collected from focal individuals (LPS-focal, Saline-focal) to quantify
changes in complement activity, corticosterone, and testosterone (males
only).
Figure 2. Effect of diet treatment (high fat, equal ratio, high
protein), time (day 0, day 8), and hemolytic complement activity (CH50)
on (a) observed richness and (b) Shannon diversity index of zebra finch
microbiotas in zebra finches fed diets differing in macronutrient
content (experiment 1).
Figure 3. Effect of diet treatment (high fat, equal ratio, high
protein), time (day 0, day 8), and stress-induced corticosterone
concentrations (ng/ml) on (a) observed richness and (b) Shannon
diversity index of zebra finch microbiotas in zebra finches fed diets
differing in macronutrient content (experiment 1).
Figure 4. (a) Proportional abundance of bacterial phyla across
diet treatment groups (high fat, equal ratio, high protein) and time
(day 0, day 8) in zebra finches fed diets differing in macronutrient
content (experiment 1). Each bar represents a sample from an individual
bird. Phyla with less than 1% relative abundance are collapsed into the
category < 1%. (b) Relative abundance of the four most common
phyla where individual points represent the relative abundance of each
phylum from an individual bird. Black circles denote the mean (±SE)
relative abundances across treatments.
Figure 5. Grams of high lipid and high protein diet consumed
per day in zebra finches challenged with lipopolysaccharide (LPS) or
saline (a, b) and in focal birds that were either housed next to
sick-conspecifics (LPS-focal) or healthy conspecifics (saline-focal) (c,
d). Data are reported as means ± standard error.
Figure 6. Physiological responses of focal birds housed in view
of conspecifics injected with saline or LPS (experiment 2). (a)
Hemolytic complement activity (CH50), (b) plasma corticosterone
concentrations, and (c) plasma testosterone concentrations in zebra
finches that were housed next to healthy (no cue of infection,
saline-focal) or sick-conspecifics (cue of infection, LPS-focal) in
experiment 2. All data are reported as means ± standard error.
Figure 7. Alpha diversity metrics are negatively associated
with consumption of the high fat diet in focal birds (LPS-focal,
saline-focal). Panels depict (a) the number of observed ASVs (observed
richness) and (b) Shannon diversity. Points represent individual birds.
Pre-treatment (day 0) samples are indicated by circles and
post-treatment samples (day 5) are represented by triangles.