Butterflyfish community composition
The overall abundance of butterflyfishes did not change significantly
over the five surveyed years (mixed effects model, fixed effect: year,
random effect: site, χ2(3) = 2.35, P =
0.5, Figure 2a). There was a significant but weak effect of year on
community structure (PERMANOVA F(3,73) = 1.7,
R2 = 0.06, P = 0.03) accounting for 6% of the
variation in composition. This result was driven by a significant
difference between the 2016 and 2022 communities only (Figure 2c,
pairwise adonis, F = 2.64, R2 = 0.07, P = 0.02). While
these results show an overall shift in the butterflyfish community, this
was driven by rare species. Therefore, we also tested whether the
community shifted significantly when we included only the five most
abundant species (C. citrinellus, C. lunulatus, C. vagabundus, C.
unimaculatus, C. rafflesia ). These species represent at least 70% of
the total butterflyfish abundance in each year (2016: 82%, 2017: 75%,
2018: 81%, 2022: 72%), include each feeding guild (facultative
corallivore, obligate corallivore, and invertivore respectively), and
are responsible for a majority of aggressive interactions. There was no
significant difference in the abundance of these dominant species
following the bleaching event, suggesting that while the overall
community shifted slightly, the majority of species involved in
aggressive encounters remained at the same level of abundance (PERMANOVA
F(3,70) = 1.8, R2 =
0.06, P = 0.06).
The relative abundance of feeding guilds (facultative, obligate coral
feeders, and invertivores) did not differ significantly between the four
surveyed years (mixed effects model, fixed effects: year and feeding
guild interaction; random effect: location,
χ2(9) = 8.9, P = 0.4, Figure 2b).