Fish feeding on mobile benthic invertebrates: influence of spatial variability in habitat associations

Patterns of habitat association and foraging were examined for a group of tropical goatfishes (family Mullidae) that feed on mobile benthic invertebrates at Lizard Island (Great Barrier Reef). All goatfish possess barbels that disturb the substratum during feeding. Foraging methods were examined for the six most common species and used in conjunction with data on habitat associations to estimate the distribution and potential impact on the benthic invertebrate assemblage of foraging-related disturbance. Particular species exhibited broad habitat associations which differed little over two surveys (January 1989, January 1990). All species showed different preferences for the substrata they foraged. Preferences for substrata exhibited by the most common reef-associated species, Parupeneus multifasciatus, differed among locations separated by 1 km, between sites 150 m apart, and between depths (shallow and deep). Habitat preferences changed with ontogeny. Based on their habitat associations and foraging preferences, species were divided into habitat generalists and specialists. Specialists associated primarily with soft sediments. Habitat generalists, such as P. multifasciatus and P. cyclostomus, are likely to have an impact on their mobile invertebrate prey that is localised, diffuse and transitory, making any experimental analysis difficult and expensive. Habitat specialists form a guild of fishes with complementary feeding modes that efficiently exploit soft sediments and are more amenable to experimental manipulation. Experiments designed to detect the impact of foraging by these fishes must be repeated at different locations and times and must account for depth differences in foraging pressure.     

Coexistence of nine anemonefish species: differential host and habitat utilization, size and recruitment

The region of Madang, Papua New Guinea, has the highest reported species diversity of both anemonefishes (nine species) and their host anemones (ten species). To determine which factors may allow so many anemonefish species to coexist at this location, we studied their patterns of distribution, abundance, and recruitment. Population surveys at three replicate reef sites within four zones situated at varying distances from the mainland (nearshore, mid-lagoon, outer barrier, and offshore) indicated that each species of host anemone and anemonefish lived within a particular range of zones. Each species of anemonefish lived primarily with one species of host. Anemonefish species that lived with the same host species usually had different distribution patterns among zones (e.g., Amphiprion percula occupied Heteractis magnifica in nearshore zones, while A. perideraion occupied H. magnifica in offshore zones). Monitoring of natural populations showed that there were few changes (losses or recruitment) in the number or species of fishes associated with each individual anemone over periods ranging from 3 to 9 months. Recruitment was monitored on anemones with and without residents (resident fishes were removed) within each of three zones (nearshore, mid-lagoon, outer barrier). Significantly more anemonefishes recruited to anemones without resident fishes than to anemones with resident fishes. Each anemonefish species recruited to particular host species and zones. The distribution and abundance of the recruits of each fish species among zones were positively correlated with the distribution and abundance of resident fishes in the benthic habitat. This suggests that the spatial patterns of recruitment among zones strongly determined the distribution and abundance patterns of the benthic populations, and they were not the result of post-recruitment mortality or movement. Coexistence of the nine anemonefish species on the limited anemone resource was considered possible because of niche differentiation (i.e., differences in host and habitat utilization among zones), and the ability of two small species (i.e., Amphiprion sandaracinos and A. leucokranos) to cohabit individual anemones with other anemonefish species. Received: 29 July 1999 / Accepted: 1 September 2000     

Spatial structure of communities on dead pen shells (<Emphasis Type="Italic">Atrina rigida</Emphasis>) in sea grass beds

Delimiting communities in marine habitats is difficult because co-occurring species often have different life histories and the life stages experience the environment at different spatial scales. The habitat of a particular community is embedded within a larger habitat or ecosystem with many species shared between the focal community and the larger system. Pen shells (Atrina rigida) are large bivalves that, once the mollusk dies, provide shelter for motile species and hard substrate for settling larval invertebrates and egg-laying fishes. In St. Joseph’s Bay, Florida (29°45′N, 85°15′W), pen shells are the most abundant source of hard substrate, especially inside sea grass (Thalassia testudinum) beds, where they reach densities of 0.1–4.0 m⁻². This study, which was conducted from May to August 2005, measured the overlap in species densities between dead pen shells and the surrounding sea grass communities at eight sites to determine the discreteness of the pen shell communities. Of the 70-epibenthic taxa recorded, 66% were found on the pen shells but not in the surrounding sea grass habitat. Community structure, which varied among shells within sites and among the eight sites, could be related to sea grass characteristics such as blade density and length either directly (e.g., inhabitants of pen shells directly benefit from the surrounding sea grass) or indirectly (e.g., pen shells and sea grass both benefit from similar factors such as current and nutrients). Pen shells were randomly distributed at several spatial scales within the 15 × 15 m sites as were many motile species. Two exceptions were the shrimp, Palaemon floridanus and the amphipod, Dulichella appendiculata, whose distributions were clumped. Most of the sessile species had clumped distributions, tending to be very abundant when they were present. These pen shell communities provide an opportunity for experimental studies of factors affecting species diversity on small, discrete, naturally occurring habitats. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Temporal and spatial settlement patterns of sympatric hermit crabs and the influence of shell resource availability

Larvae of marine organisms often need specific resources or environments at settlement, and their success at settlement might be strongly influenced by the abundance and distribution of such specific resources. The larvae of hermit crabs need small shells to settle, so it is thought that the distribution and abundance of small shells influence the settlement pattern of hermit crabs. To investigate the influence of small shell distribution on the settlement of pagurid hermit crab larvae, we conducted a field experiment at an intertidal rocky shore in Hakodate Bay, Japan. From the line-transect sampling in the field, we found that Pagurus middendorffii settled extensively in the offshore side of the intertidal zone while P. nigrofascia settled in the uppermost area of the intertidal zone. Small shells were most abundant in a narrow shallow trough, slightly offshore from the uppermost area of the intertidal zone. For both species, settler abundance was high where adults were abundant, but settler abundance did not appear to be related to shells abundance. An experiment to clarify settlement patterns showed that larval recruits tended to be similar to those in the line-transect sampling of settlers. Thus shells may not be a primary factor affecting settlement patterns at relatively large scale within the intertidal flat. However, when we analyzed the relationship of settlers and shells separately within each transect, the distribution of settlers was well explained by shell resource availability. Therefore on a smaller scale, shell availability may influence the number of settlers. Settlement periods of P. middendorffii and P. nigrofascia fully overlapped, so their larvae probably were affected by similar transport factors, such as current and tidal movement. Nevertheless they showed different spatial patterns of settlement.Communicated by T. Ikeda, Hakodate     

Biodiversity in the ecosystem of the Portuguese continental shelf: distributional ecology and the role of benthic amphipods

The biodiversity and distributional ecology of amphipod crustaceans were analysed from benthic surveys in 1985 and 1986 along the coast of Portugal, from the Tagus canyon to the coast of Minho, in order to determine their role in the ecosystem of the Portuguese continental self. In samples obtained from different types of substrate between 18 and 545 m, we identified 113 species belonging to 51 genera of 24 families. Seventeen of these species were new records for the Portuguese coast. The relative frequencies and number of individuals of all species were analysed. The genus Ampelisca clearly dominated the group of the most frequent and abundant species, which also exhibited a large range of vertical distribution. Most of the 113 species were found only down to 150 m depth, corresponding roughly to the lower limit of the continental shelf. Fifteen species exhibited clear bathyal traits, being consistently found deeper than 100 m, especially in the Tagus canyon and the upper zone of the continental slope. The most frequent and abundant species were found predominatly or in large numbers in medium to fine sand bottoms. This type of substrate also contained the highest number of species. The granulometric structure of the habitat could constitute the most important factor controlling both biodiversity and development of large amphipod populations, since oxygen level, water exchange, number of available shelters, and probably the quantity and quality of nutritional resources all vary as a function of substrate texture. Because of their dominance in both frequency and abundance, several Ampelisca species may constitute an important food source for many secondary consumers of the shelf sediments, especially for demersal fishes.     

Do artificial structures alter marine invertebrate genetic makeup?

Human-made structures are increasingly built in marine coastal habitats for a variety of purposes. Offshore oil and gas production platforms are among the largest examples. Yet, biological effects of these increasing density artificial substrata are under evaluated. The objective of our study is to investigate the possible role of offshore platforms in modifying the genetic composition of populations of natural rocky shores species. The serpulid Pomatoceros triqueter was used as a model, and genetic variation was assessed using a 419?bp fragment of the mtDNA COI gene in samples collected on eleven offshore gas platforms, on one coastal buoy on the sandy shore and in four sites located on natural rocky shores in the Adriatic Sea. Deep phylogenetic lineages were uncovered over all samples. Nucleotide diversity and mean number of pairwise differences among haplotypes were significantly smaller in offshore platform samples compared to rocky shores samples. No significant genetic structure was observed over all samples. We found direct evidence of lower genetic diversity on platforms confirming that, although artificial structures attract and support species typical of hard bottoms, they are not analogues of natural rocky habitats.     

Macrobenthic species assemblages in Ellis Fjord,Vestfold Hills,Antarctica

A study was made of the sub-littoral benthic environment of Ellis Fjord, a 10 km-long fjord located near Davis Station, in the Vestfold Hills, Antarctica, over a 15 mo period (November 1984 to February 1986). Data were collected by SCUBA diving and underwater photography and were inhitially analysed by ordination techniques (non-metric multidimensional scaling). Ordinations showed substratum type to be the factor most strongly associated with changes in the distribution and abundance of macrobenthic species within the fjord. Other factors shown to be associated with changes in macrobenthic species assemblages were depth, distance from the fjord mouth, bottom slope, shoreline characteristics, current speed, and the presence of low-salinity water at shallow depths during the summer melt. The four major substratum types in Ellis Fjord were sand, rock, Serpula narconensis colonies and Phyllophora antarctica thalli. S. narconensis colonies supported the most species and sand substrate supported the least. P. antarctica is the only macrophyte species which occurred in the fjord. S. narconensis colonies in Ellis Fjord from one of the largest known tubeworm reefs in the world. The assemblages of benthic species in Ellis Fjord were different from those seen at other sub-littoral benthic sites off the Vestfold Hills, and at other Antarctic sites. There was a far greater proportion of filter-feeding species in the fjord than at other sub-littoral benthic sites off the Vestfold Hills. Factors which are thought to have caused these differences are the high level of organic but low level of inorganic input into the benthic system of the fjord, and the absence of anchor ice from the fjord.     

A Mechanistic Approach to Evaluation of Umbrella Species as Conservation Surrogates

Abstract:  Although species with large area requirements are sometimes used as umbrella species, their general utility as conservation tools is uncertain. We surveyed the species diversity of birds, butterflies, carabids, and forest-floor plants in forest sites across an area (1600 km²) in which we delineated large breeding home ranges of Northern Goshawk ( Accipiter gentilis ). We tested whether protection of the home ranges could serve as an effective umbrella to protect sympatric species of the four taxa. We also used an empirical habitat model of occupancy of home range to examine mechanisms by which the Northern Goshawk acts as an umbrella species. Among species richness, abundance, and species composition of the four taxa, only abundance and species composition of birds differed between sites located inside and outside home ranges, which was due to greater abundance of bird species that were prey of Northern Goshawks inside the home ranges. Thus, although home range indicated areas with high abundance of certain bird prey species, it was not effective as an indicator of the species diversity of all four taxa. We also did not find any difference in species richness, abundance, and species composition between sites predicted as occupied and unoccupied using the habitat model. In contrast, when we selected sites on the basis of each habitat variable in the model, habitat variables that selected sites either in agricultural or forested landscapes encompassed sites with high species richness or particular species composition. This result suggests that the low performance of the Northern Goshawk as an umbrella species is due to this species' preference for habitat in both agricultural and forested landscapes. Species that can adjust to changes in habitat conditions may not act as effective umbrella species despite having large home ranges.     

Loss of genetic diversity in Harpacticoida near offshore platforms

Offshore oil and gas production platforms can be a source of chronic stress that could lead to sublethal impacts on resident benthic organisms. In June 1993 and January 1994, genetic diversity of Harpacticoida (Copepoda) living proximal to operating, offshore platforms in the Gulf of Mexico was estimated to test if platforms are associated with strong selective pressures. Because harpacticoids have short generation times and direct benthic development, they are suitable organisms for examining population responses. Genetic diversity was estimated by comparing restriction fragment length polymorphisms generated from mitochondrial DNA amplified by the polymerase chain reaction on individuals of five species (Cletodes sp., Enhydrosoma pericoense, Normanella sp., Robertsonia sp., and Tachidiella sp.). Populations living at Near regions (stations<50 m from a platform) had significantly less haplotype diversity than populations of the same species living at Far regions (stations>3 km from a platform). The levels of haplotype diversity exhibited by the Far populations were similar at three different platforms located hundreds of kilometers apart. The differences in haplotype diversity between Near and Far regions were the result of a higher proportion of dominant haplotypes, and a loss of less common haplotypes. Haplotypic diversity was inversely correlated with a multivariate measurement of levels of sediment contaminants. The pattern of haplotype diversity on the Gulf of Mexico continental shelf seems to consist of a uniform level of haplotype diversity, punctuated by islands of lower diversity around oil and gas platforms. The selective pressures that lead to a loss of genetic diversity may be the result of contaminants, other differences in the physico-chemical environment, or disturbance in general.     

Spatial distribution patterns of the soft corals Alcyonium acaule and Alcyonium palmatum in coastal bottoms (Cap de Creus, northwestern Mediterranean Sea)

Current knowledge on the abundance and distribution patterns of different soft coral species is relatively limited when compared to other benthic suspension feeders such as gorgonians and hard coral species. To overcome this scarcity of information, the distribution patterns of the soft corals Alcyonium acaule and Alcyonium palmatum were investigated in northwestern Mediterranean benthic communities over a wide geographical (60 km of coastline) and bathymetrical (0–70 m depth) extent using a remotely operated vehicle. A. acaule was the most abundant species in the study area with highest recorded density of 18 col m^?2 found at depths of 35–45 m in areas that are directly exposed to strong near-bottom currents. Conversely, A. palmatum was only found as scattered solitary colonies at greater depths in soft bottoms, with maximum density of 2.4 col m^?2. Medium and large colonies of A. acaule were preferentially found on sloping and vertical rocky bottoms where they form dense patches. High-density patches of A. acaule were preferentially found on vertical rocky bottom, while isolated colonies were preferentially observed on coralligenous substrata as well as on flat soft and maërl substrates. A. acaule biomass distribution showed highest values between 40 and 45 m depth, and between 60 and 65 m depth. This suggests that deeper populations are formed by colonies that are bigger than the equivalent shallower ones. Although both species are almost genetically identical, ecologically they are very different. For this reason, conservation plans should consider the differential ecological traits shown by these two soft coral species.     

Effect of the Introduced Common Slipper Shell on the Suprabenthic Biodiversity of the Subtidal Communities in the Bay of Saint-Brieuc

Abstract: Our study compared the suprabenthic fauna collected in the Bay of Saint-Brieuc (western English Channel) in September 1995 and May 1996 at two sites colonized by Crepidula fornicata with that of one site where it was absent (site 23–0). Where Crepidula was present, no species dominated and abundance remained low. At the site without Crepidula , abundance was higher and the mysid Haplostylus lobatus dominated the suprabenthic community. Swimming activity of most suprabenthic species was increased by the presence of C. fornicata . The differential abundance and swimming activity of certain species are linked to the conversion of the formerly soft substrate to now hard, shelled substrate.     

Effects of Oil‐Palm Plantations on Diversity of Tropical Anurans

Agriculturally altered vegetation, especially oil‐palm plantations, is rapidly increasing in Southeast Asia. Low species diversity is associated with this commodity, but data on anuran diversity in oil‐palm plantations are lacking. We investigated how anuran biological diversity differs between forest and oil‐palm plantation, and whether observed differences in biological diversity of these areas is linked to specific environmental factors. We hypothesized that biological diversity is lower in plantations and that plantations support a larger proportion of disturbance‐tolerant species than forest. We compared species richness, abundance, and community composition between plantation and forest areas and between site types within plantation and forest (forest stream vs. plantation stream, forest riparian vs. plantation riparian, forest terrestrial vs. plantation terrestrial). Not all measures of biological diversity differed between oil‐palm plantations and secondary forest sites. Anuran community composition, however, differed greatly between forest and plantation, and communities of anurans in plantations contained species that prosper in disturbed areas. Although plantations supported large numbers of breeding anurans, we concluded the community consisted of common species that were of little conservation concern (commonly found species include Fejervarya limnocharis, Microhyla heymonsi, and Hylarana erythrea). We believe that with a number of management interventions, oil‐palm plantations can provide habitat for species that dwell in secondary forests. Efectos de las Plantaciones de Palma de Aceite sobre la Diversidad de Anuros Tropicales Faruk et al.     

Dynamics of parrotfish grazing scars

Parrotfishes exhibit a range of feeding modes. These species vary in both feeding morphology and behaviour, but the vast majority of species leave distinctive scars on the substratum when feeding. Although the role of parrotfishes in reef resilience is well documented, the basis of this role and the effect of their grazing scars on the benthic community structure remain unclear. This study evaluated the dynamics of grazing scars of large adult Scarus rivulatus and Chlorurus microrhinos on an inshore reef in the Great Barrier Reef (GBR). These species represent the most abundant scraping and excavating parrotfish species on inshore reefs. Grazing scars of each species were marked, measured and observed for seven consecutive days. S. rivulatus grazing scars were smaller in area and volume and more rapidly reoccupied by algae than those of C. microrhinos. However, because of the higher abundance and feeding frequency of S. rivulatus at the study site, this species had higher algal removal rates than C. microrhinos. These species appear to play distinctly different functional roles in shaping the benthic community of inshore GBRs. S. rivulatus is primarily responsible for algal dynamics dominated by vegetative regrowth. In contrast, C. microrhinos opens relatively large areas which remain clear for several days. These scars may represent settlement sites which are relatively free from algae and sediment. This study provides new information on the differences between scraping and excavating parrotfishes and, in a system with just one abundant large excavating species, emphasizes the potential for low functional redundancy in high diversity coral reef systems.     

Impact of Arenicola marina (Polychaeta) on the microbial assemblages and meiobenthos in a marine intertidal flat

The benthic microbial food web can be responsible for a large proportion of benthic carbon cycling yet there are few data on the trophic interactions between this food web and macrobenthos. A large-scale field experiment was conducted to investigate effects of eliminating the polychaete Arenicola marina on benthic microbes (prokaryotes, heterotrophic and autotrophic protists) and metazoan meiofauna in a marine intertidal flat of the North Sea, Germany. Over a period of 2 years, quantity and composition of micro- and meiobenthos from unmanipulated sites were compared to those from sites deplete of lugworms. These grazer treatments were cross-classified with different sediment characteristics (low- and mid-intertidal areas). Lugworm removal resulted in an initial increase in abundance of prokaryotes and nanoflagellates, which became less pronounced in the second year. Ciliates were not affected quantitatively, but in the absence of lugworms, diversity and the proportion of carnivorous forms increased. Meiobenthos (nematodes, ostracods and copepods) were affected only moderately. The observed changes are probably due to a combination of release from grazing/predation pressure, changes in the species composition of higher trophic levels (namely large polychaetes) and altered environmental conditions (such as depth of the oxygenated layer and sediment grain size). Spatial differences between sites of different tidal exposure/grain size appeared to be as large as temporal differences during the 2 years following the manipulation of the system. We conclude that in intertidal sediments, indirect effects due to habitat transformation are as important as direct biological interactions (grazing pressure and competition) for the dynamics of the benthic microbial food web.     

Stalked tunicates Boltenia ovifera form biogenic habitat in the rocky subtidal zone of Nova Scotia

The stalked tunicate Boltenia ovifera is widely distributed in the Arctic and North Atlantic oceans on rocky substrata at 10–300 m depth, although its ecological role in benthic communities is poorly understood. The distribution and abundance of B. ovifera were recorded at 10–100 m depth in towed-video transects in November 2011 and in June, July, and November 2012 off a wave-exposed headland near Halifax, Nova Scotia. Specimens also were collected at 30 m depth using SCUBA (44°26.88′N, 63°31.59′W) in September 2012. Areas dominated by B. ovifera had densities of 10–100 individuals m^?2 on rocky substrata at 30–60 m depth. These tunicate beds often were associated with sparse kelp (Agarum clathratum) and turf-forming red algae. A generalized additive model indicated that depth, substrate type, and benthic algal type were strong predictors of tunicate abundance. Twenty-two epibiotic species were found on specimens of B. ovifera, including juvenile conspecifics. Filter-feeding macroinvertebrates, including anemones and soft corals, were more abundant in areas with B. ovifera than in areas without these tunicates. Our findings suggest that beds of B. ovifera can act as biogenic habitat to enhance local species richness in the rocky subtidal zone of Nova Scotia.     

Mangroves as nursery sites: comparisons of the abundance and species composition of fish and crustaceans in mangroves and other nearshore habitats in tropical Australia

Daytime sampling of mangrove and seagrass (Halophila/Halodule community) habitats every 7 wk at Alligator Creek, Queensland, Australia, over a period of 13 mo (February 1985–February 1986) using two types of seine net, revealed distinct mangrove and seagrass fish and crustacean faunas. Total abundance of fish and relative abundance of small and large fish also varied between habitats and seasonally. Post-larval, juvenile and small adult fish captured with a small seine-net (3 mm mesh) were significantly more abundant (4 to 10 times) in the mangrove habitat throughout the 13 mo of sampling. Mangrove fish abundance showed significant seasonality, greatest catches being recorded in the warm, wet-season months of the year. Relative abundances of larger fish (captured in a seine net with 18 mm mesh) in the two habitats varied throughout the year, but did not show a seasonal pattern. At the same site, small crustaceans were significantly more abundant in the mangroves in all but one dryseason sample. Similar comparisons for three riverine sites, sampled less frequently, in the dry and wet seasons of 1985 and 1986, respectively, showed that in general mangrove habitats had significantly more fish per sample, although the relative abundance of fish in mangroves and other habitats changed with season. Crustacean catches showed a similar pattern, except that densities among sites changed with season. Fish and crustacean abundance in mangroves varied among sites, indicating that estuaries differ in their nursery-ground value. The juveniles of two commercially important penaeid prawn species (Penaeus merguiensis and Metapenaeus ensis) were amongst the top three species of crustaceans captured in the study, and both were significantly more abundant in the mangrove habitat. By contrast, mangroves could not be considered an important nursery for juveniles of commercially important fish species in northern Australia. However, based on comparisons of fish catches in other regions, the results of the present study indicate the importance of mangroves as nursery sites for commercially exploited fish stocks elsewhere in South-East Asia. Contribution No. 378 from the Australian Institute of Marine Science     

Offshore distributional patterns of Hawaiian fish larvae

An analysis of ichthyoplankton samples based on relative abundance reveals pronounced inshore/offshore distributional gradients for most Hawaiian fish larvae. Larvae of pelagic bay species are found almost exclusively in semi-enclosed bays and estuaries. Larvae of pelagic neritic species are more or less uniformly distributed with distance from shore. The larvae of reef species with non-pelagic eggs are most abundant close to shore, while those of reef species with pelagic eggs are most abundant offshore. Finally, the larvae of offshore (primarily mesopelagic) species show no clear pattern but frequently occur in high numbers nearshore. Within any group, variation in pattern was often evident; for example, although Hawaiian fishes of both the families Labridae and Mullidae spawn pelagic eggs, larvae of the former had not peaked in abundance 12 km from shore while larvae of the latter had peaked between 0.5 and 2 km. Some larvae which occur offshore are highly specialized morphologically for a pelagic existence (e.g. Chaetodontidae, which is illustrated) while others are little modified (e.g. Labridae). These findings indicate ichthyoplankton surveys in tropical areas must sample offshore areas in addition to the inshore adult habitat to obtain a complete picture.Hawaii Institute of Marine Biology Contribution No. 484.     

Biodiversity of coastal polyclad flatworm assemblages in the wider Caribbean

Polyclads are mobile predators and possibly an important functional component of hard substrate marine environments globally. To understand the natural patterns of spatial differences, polyclad assemblages were sampled in seven coastal regions across the wider Caribbean spanning 15° latitude and 24° longitude between May and June 2005 and May and September 2006. In total, 67 species in 28 genera and 17 families were recorded from 62 sites. Only two species were found in all surveyed regions, Melloplana ferruginea and Pseudoceros bicolor. Conversely, 41 species were restricted to one or two sites, and 34 species were represented by one or two individuals. The distribution and abundance of species varied between the two suborders. Cotyleans were most species rich and had a higher number of species of restricted range, while Acotylea showed a higher proportion of rare species; however, two species were highly abundant comprising over half of the individuals counted. In most habitats, polyclads were rare, but in some intertidal habitats two species, Styloplanocera fasciata and Boninia divae were densely aggregated and dominant members of the benthic epifauna. Alpha diversity was variable but showed no evidence of a relationship with latitude, longitude or depth. Beta diversity increased with the number of habitats sampled and was highest for cotyleans. Highest gamma diversity was recorded in Jamaica and the US Virgin Islands and was not significantly correlated to alpha diversity. Overall assemblages from the seven regions were similar, revealing faunal homogeneity across the wider region. Reef assemblages were distinct from other habitats dominated by species of the Cotylea. Reefs from Panama and the US Virgin Islands were the most species rich. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.