Data from: Biogeographical diet variation within and between the rabbitfishes Siganus corallinus, Siganus doliatus, Siganus trispilos and Siganus virgatus

Feeding habits of herbivorous fishes play an important role in shaping
form and function of coastal marine ecosystems. Rabbitfishes (Siganidae)
are important consumers of macroalgae on Indo-West Pacific coral reefs.
However, it is unclear how their diet varies among and within species at
biogeographical scales, casting doubt on their precise functional roles
across different regions. The present study assessed the inter- and
intraspecific diet variation of four rabbitfishes (Siganus trispilos,
Siganus coralinus, Siganus virgatus, and Siganus doliatus) factored by
morphological relatedness among populations from Ningaloo Reef (western
Australia), the Great Barrier Reef (GBR, eastern Australia) and the
Yaeyama Islands (Okinawa Prefecture, Japan). Results showed that region
had a strong effect on diet, effectively reducing the expected effect of
morphologic similitude. While intraspecific differences were only
significant when populations inhabited different regions; interspecific
differences were not as predicted, with different morphotypes having
similar diets when populations inhabited the same regions. Rabbitfishes
consumed more corticated and filamentous macroalgae on the GBR, more
foliose and membranous macroalgae at the Yaeyama Islands, and more
leathery macroalgae at Ningaloo Reef. The findings indicate that
rabbitfishes have high diet plasticity, and hence their functional role as
mediators of competition between macroalgae and corals can change across
biogeographic regions. Local context is therefore important when assessing
the diet and functional role of herbivorous fishes. As climate change
unfolds, shifts in the distribution, trophic behaviour and function of
species are expected, making the study of trophic plasticity more
important.