Diversity and Structure of Parrotfish Assemblages across the Northern Great Barrier Reef

Johnson, G.; Taylor, Brett M.; Robbins, William D.; Franklin, Erik C.; Toonen, Robert J.; Bowen, Brian W.; Choat, J. Howard

doi:10.3390/d11010014

Cited by 24 publications

(20 citation statements)

References 65 publications

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“…That cross-shelf structure of roving herbivorous fish assemblages was distinct at each shelf position prior to disturbances is consistent with previous studies on the GBR [5,14,18,20,22,[35][36][37]. The differences in assemblage structure of herbivorous fish among shelf positions are likely driven by the natural variation in environmental conditions across the shelf forming distinct habitats that favour particular species [5,7,22].…”

Section: Discussionsupporting

confidence: 85%

Cross-Shelf Differences in the Response of Herbivorous Fish Assemblages to Severe Environmental Disturbances

et al. 2019

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Cross-shelf differences in coral reef benthic and fish assemblages are common, yet it is unknown whether these assemblages respond uniformly to environmental disturbances or whether local conditions result in differential responses of assemblages at different shelf positions. Here, we compare changes in the taxonomic and functional composition, and associated traits, of herbivorous reef fish assemblages across a continental shelf, five years before and six months after two severe cyclones and a thermal bleaching event that resulted in substantial and widespread loss of live hard coral cover. Each shelf position maintained a distinct taxonomic assemblage of fishes after disturbances, but the assemblages shared fewer species among shelf positions. There was a substantial loss of species richness following disturbances within each shelf position. Total biomass of the herbivorous fish assemblage increased after disturbances on mid- and outer-shelf reefs, but not on inner-shelf reefs. Using trait-based analyses, we found there was a loss of trait richness at each shelf position, but trait specialisation and originality increased on inner-shelf reefs. This study highlights the pervasiveness of extreme environmental disturbances on ecological assemblages. Whilst distinct cross-shelf assemblages can remain following environmental disturbances, assemblages have reduced richness and are potentially more vulnerable to chronic localised stresses.

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Section: Discussionsupporting

confidence: 85%

Cross-Shelf Differences in the Response of Herbivorous Fish Assemblages to Severe Environmental Disturbances

et al. 2019

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“…Ecological niche space for parrotfishes in the TEP is constrained by a general lack of active coral reef construction. Rather, the vast majority of primary grazing surfaces are associated with rocky benches and boulders, and the TEP largely lacks the structural and erosional niche dimensions associated with coral reefs that is positively related to species- and functional diversity [ 54 , 55 ]. Powerful excavating species like S. perrico and S. rubroviolaceus may thrive in the rocky-reef habitats of the TEP because of jaw morphologies and musculature that can effectively remove low-lying encrusting epibionts from smooth rock surfaces.…”

Section: Discussionmentioning

confidence: 99%

The origin of the parrotfish species Scarus compressus in the Tropical Eastern Pacific: region-wide hybridization between ancient species pairs

et al. 2021

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Background In the Tropical Eastern Pacific (TEP), four species of parrotfishes with complex phylogeographic histories co-occur in sympatry on rocky reefs from Baja California to Ecuador: Scarus compressus, S. ghobban, S. perrico, and S. rubroviolaceus. The most divergent, S. perrico, separated from a Central Indo-Pacific ancestor in the late Miocene (6.6 Ma). We tested the hypothesis that S. compressus was the result of ongoing hybridization among the other three species by sequencing four nuclear markers and a mitochondrial locus in samples spanning 2/3 of the latitudinal extent of the TEP. Results A Structure model indicated that K = 3 fit the nuclear data and that S. compressus individuals had admixed genomes. Our data could correctly detect and assign pure adults and F1 hybrids with > 0.90 probability, and correct assignment of F2s was also high in some cases. NewHybrids models revealed that 89.8% (n = 59) of the S. compressus samples were F1 hybrids between either S. perrico × S. ghobban or S. perrico × S. rubroviolaceus. Similarly, the most recently diverged S. ghobban and S. rubroviolaceus were hybridizing in small numbers, with half of the admixed individuals assigned to F1 hybrids and the remainder likely > F1 hybrids. We observed strong mito-nuclear discordance in all hybrid pairs. Migrate models favored gene flow between S. perrico and S. ghobban, but not other species pairs. Conclusions Mating between divergent species is giving rise to a region-wide, multispecies hybrid complex, characterized by a high frequency of parental and F1 genotypes but a low frequency of > F1 hybrids. Trimodal structure, and evidence for fertility of both male and female F1 hybrids, suggest that fitness declines sharply in later generation hybrids. In contrast, the hybrid population of the two more recently diverged species had similar frequencies of F1 and > F1 hybrids, suggesting accelerating post-mating incompatibility with time. Mitochondrial genotypes in hybrids suggest that indiscriminate mating by male S. perrico is driving pre-zygotic breakdown, which may reflect isolation of this endemic species for millions of years resulting in weak selection for conspecific mate recognition. Despite overlapping habitat use and high rates of hybridization, species boundaries are maintained by a combination of pre- and post-mating processes in this complex.

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“…However, S. rivulatus has been well studied but mainly focused on coral reefs. On the GBR, S. rivulatus is a species characteristic of mid-shelf reefs, often being present in lagoons and back reef habitats [54,55,73], and has been shown to have limited home range movements as adults [74].…”

Section: Discussionmentioning

confidence: 99%

Unravelling Seascape Patterns of Cryptic Life Stages: Non-Reef Habitat Use in Juvenile Parrotfishes

et al. 2020

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Juvenile fish often use alternative habitats distinct from their adult phases. Parrotfishes are an integral group of coral reef fish assemblages, are targeted in fisheries, are sensitive to reef disturbances, and have been documented as multiple-habitat users. Considering the abundance of research conducted on parrotfishes, very little is known about their juvenile ecology at the species level due to their cryptic and variable coloration patterns. We collected juvenile parrotfishes in non-reef habitats (macroalgal beds, seagrass beds, and lagoons) in the Philippines and used DNA analysis to determine species composition. The results were then compared with data on adult parrotfish abundance from underwater visual census (UVC) surveys in coral reef and non-reef habitats. Collections identified 15 species of juvenile parrotfishes in non-reef habitats, and of these, 10 were also recorded in UVCs as adults. Informed by adult surveys, 42% of the 19 parrotfish species observed as adults were classified as multi-habitat users based on their presence in coral reef and non-reef habitats. When accounting for the occurrence of species as juveniles in non-reef habitats, 93% of the species collected as juveniles would be considered multi-habitat users. Species identified as juveniles in non-reef habitats comprised 50% of the average adult parrotfish density on coral reefs and 58–94% in non-reef habitats. The species richness of juveniles in non-reef habitats was greater than that of adults occupying the same habitats, and the most common adult species observed in UVCs was not collected as juveniles in non-reef habitats. Finally, UVC suggested that 97% of juvenile parrotfish <10-cm total length was present in non-reef habitats compared to coral reefs. These results provide further evidence for ontogenetic movement across habitat boundaries for parrotfish species in a diverse and highly connected tropical seascape. This is one of the few studies to quantify links between nursery and adult habitat in parrotfishes, highlighting the importance of including non-reef habitats in ecological studies of an iconic group of coral reef fish.

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Diversity and Structure of Parrotfish Assemblages across the Northern Great Barrier Reef

Cited by 24 publications

References 65 publications

Cross-Shelf Differences in the Response of Herbivorous Fish Assemblages to Severe Environmental Disturbances

Cross-Shelf Differences in the Response of Herbivorous Fish Assemblages to Severe Environmental Disturbances

The origin of the parrotfish species Scarus compressus in the Tropical Eastern Pacific: region-wide hybridization between ancient species pairs

Unravelling Seascape Patterns of Cryptic Life Stages: Non-Reef Habitat Use in Juvenile Parrotfishes

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