Island foxes and island spotted skunks exhibited the core
mammalian microbiome, with the relative abundance of bacteria differing
between host species and (for skunks) island populations
Gut microbial communities of island foxes and island spotted skunks
contained high proportions of Firmicutes (SCZ: Fox=33.9%, Skunk=43.4%;
SRI: Fox=20.8%, Skunk=56.8%) and Bacteroidetes (SCZ: Fox=26%,
Skunk=24.5%; SRI: Fox=46.7%, Skunk=25.6%). Dominant classes within
these phyla included Bacilli, Clostridia, and (for foxes)
Erysipelotrichi (Phylum: Firmicutes); and Bacteroidia (Phylum:
Bacteroidetes; Figure 4). Additional phyla with relative abundances
above 1% included Actinobacteria (SCZ: Fox=3.6%, Skunk=21%; SRI:
Fox=7.7%, Skunk=5.8%), Proteobacteria (SCZ: Fox=20.6%, Skunk=4.1%;
SRI: Fox=13.3%, Skunk=7.1%), and Fusobacteria (SCZ: Fox=15.1%,
Skunk=5.6%; SRI: Fox=9.7%, Skunk=4.3%). Dominant classes within these
phyla included Actinobacteria and Coriobacteriia (Phylum:
Actinobacteria); Gammaproteobacteria, Epsilonproteobacteria, and
Deltaproteobacteria (Phylum: Proteobacteria); and Fusobacteriia (Phylum:
Fusobacteria; Figure 4). All additional phyla summed to less than 2%
within each island population (SCZ: Fox=0.8%, Skunk=1.4%; SRI:
Fox=1.8%, Skunk=0.4%).
While the presence of taxa was largely consistent across species and
islands, their relative abundances often differed. We therefore used
ANCOM to identify significantly differentially abundant taxa within each
island and species at the class level (Table 2). Within-island
comparisons between island foxes and island spotted skunks returned four
unique classes. On Santa Cruz Island, island foxes harbored more
Gammaproteobacteria (W=54; 13.8% vs. 0.8%) and Deltaproteobacteria
(W=50; 0.4% v. 0.009%) than island spotted skunks, while island
spotted skunks harbored more Actinobacteria (W=52; 9.2% vs. 1.9%) than
island foxes. On Santa Rosa Island, island foxes again harbored more
Gammaproteobacteria (W=55; 9.9% vs. 0.4%) and Deltaproteobacteria
(W=57; 1% v. 0.01%) than island spotted skunks, whereas island spotted
skunks exhibited more Epsilonproteobacteria (W=54; 6.5% vs. 2%).
Similar analyses conducted within each species revealed island-specific
differences within island spotted skunks but not within island foxes
(Table 2). Island spotted skunks exhibited a higher percentage of
Coriobacteriia (W=54; 11.8% vs. 0.08%) on Santa Cruz Island, with no
classes significantly more abundant in Santa Rosa Island skunks.