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Although parasites are ubiquitous in marine ecosystems, predicting the abundance of parasites present within marine ecosystems has proven challenging due to the unknown effects of multiple interacting environmental gradients and stressors. Furthermore, parasites often are considered as a uniform group within ecosystems despite their significant diversity.We aim to determine the potential importance of multiple predictors of parasite abundance in coral reef ecosystems, including reef area, island area, human population density, chlorophyll‐a, host diversity, coral cover, host abundance and island isolation.Using a model selection approach within a database of more than 1,200 individual fish hosts and their parasites from 11 islands within the Pacific Line Islands archipelago, we reveal that geographic gradients, including island area and island isolation, emerged as the best predictors of parasite abundance.Life history moderated the relationship; parasites with complex life cycles increased in abundance with increasing island isolation, while parasites with direct life cycles decreased with increasing isolation. Direct life cycle parasites increased in abundance with increasing island area, although complex life cycle parasite abundance was not associated with island area.This novel analysis of a unique dataset indicates that parasite abundance in marine systems cannot be predicted precisely without accounting for the independent and interactive effects of each parasite's life history and environmental conditions. [ABSTRACT FROM AUTHOR]

Aim: Identification of the processes that generate and maintain species diversity within the same region can provide insight into biogeographic patterns at broader spatiotemporal scales. Hawkfishes in the genus Paracirrhites are a unique taxon to explore with respect to niche differentiation, exhibiting diagnostic differences in coloration, and an apparent center of distribution outside of the Indo–Malay–Philippine (IMP) biodiversity hotspot for coral reef fishes. Our aim is to use next‐generation sequencing methods to leverage samples of a taxon at their center of maximum diversity to explore phylogenetic relationships and a possible mechanism of coexistence. Location: Flint Island, Southern Line Islands, Republic of Kiribati. Methods: A comprehensive review of museum records, the primary literature, and unpublished field survey records was undertaken to determine ranges for four "arc‐eye" hawkfish species in the Paracirrhites species complex and a potential hybrid. Fish from four Paracirrhites species were collected from Flint Island in the Southern Line Islands, Republic of Kiribati. Hindgut contents were sequenced, and subsequent metagenomic analyses were used to assess the phylogenetic relatedness of the host fish, the microbiome community structure, and prey remains for each species. Results: Phylogenetic analyses conducted with recovered mitochondrial genomes revealed clustering of P. bicolor with P. arcatus and P. xanthus with P. nisus, which were unexpected on the basis of previous morphological work in this species complex. Differences in taxonomic composition of gut microbial communities and presumed prey remains indicate likely separation of foraging niches. Main Conclusions: Our findings point toward previously unidentified relationships in this cryptic species complex at its proposed center of distribution. The three species endemic to the Polynesian province (P. nisus, P. xanthus, and P. bicolor) cluster separately from the more broadly distributed P. arcatus on the basis of relative abundance of metazoan sequences in the gut (presumed prey remains). Discordance between gut microbial communities and phylogeny of the host fish further reinforce the hypothesis of niche separation. [ABSTRACT FROM AUTHOR]

Abstract: Human impacts on ecosystems can decouple the fundamental ecological relationships that create patterns of diversity in free‐living species. Despite the abundance, ubiquity, and ecological importance of parasites, it is unknown whether the same decoupling effects occur for parasitic species. We investigated the influence of fishing on the relationship between host diversity and parasite diversity for parasites of coral reef fishes on three fished and three unfished islands in the central equatorial Pacific. Fishing was associated with a shallowing of the positive host‐diversity–parasite‐diversity relationship. This occurred primarily through negative impacts of fishing on the presence of complex life‐cycle parasites, which created a biologically impoverished parasite fauna of directly transmitted parasites resilient to changes in host biodiversity. Parasite diversity appears to be decoupled from host diversity by fishing impacts in this coral reef ecosystem, which suggests that such decoupling might also occur for parasites in other ecosystems affected by environmental change. [ABSTRACT FROM AUTHOR]

Aim There is global consensus that marine protected areas offer a plethora of benefits to the biodiversity within and around them. Nevertheless, many organisms threatened by human impacts also find shelter in unexpected or informally protected places. For coral reef organisms, refuges can be tourist resorts implementing local environment-friendly bottom-up management strategies. We used the coral reef ecosystem as a model to test whether such practices have positive effects on the biodiversity associated with de facto protected areas. Location North Ari Atoll, Maldives. Methods We modelled the effects of the environment and three human management regimes (tourist resorts, uninhabited and local community islands) on the abundance and diversity of echinoderms and commercially important fish species, the per cent cover of reef benthic organisms (corals, calcareous coralline algae, turf and macroalgae) and the proportion of coral disease. We used multivariate techniques to assess the differences between reef components among the management regimes. Results Reefs varied between the management regimes. A positive 'resort effect' was found on sessile benthic organisms, with good coral cover and significantly less algae at resort islands. Corals were larger and had fewer diseases in uninhabited islands. Minor 'resort effect' was detected on motile species represented by commercial fish and echinoderms. Main conclusions In countries where natural biodiversity strongly sustains the tourist sector and where local populations rely on natural resources, a balance between tourism development, local extraction practices and biodiversity conservation is necessary. The presence of eco-friendly managed resorts, which practices would need to be certified on the long term, is beneficial to protect certain organisms. House reefs around resorts could therefore provide areas adding to existing marine protected areas, while marine protection efforts in local community islands should focus on improving fishing management. [ABSTRACT FROM AUTHOR]

Human impacts can homogenize and simplify ecosystems, favoring communities that are no longer naturally coupled with (or reflective of) the background environmental regimes in which they are found. Such a process of biophysical decoupling has been explored little in the marine environment due to a lack of replication across the intact-to-degraded ecosystem spectrum. Coral reefs lacking local human impacts provide critical baseline scenarios in which to explore natural biophysical relationships, and provide a template against which to test for their human-induced decoupling. Using 39 Pacific islands, 24 unpopulated (relatively free from local human impacts) and 15 populated (with local human impacts present), spanning 45° of latitude and 65° of longitude, we ask, what are 'natural' biophysical relationships on coral reefs and do we see evidence for their human-induced decoupling? Estimates of the percent cover of benthic groups were related to multiple physical environmental drivers (sea surface temperature, irradiance, chlorophyll- a, and wave energy) using mixed-effects models and island mean condition as the unit of replication. Models across unpopulated islands had high explanatory power, identifying key physical environmental drivers of variations in benthic cover in the absence of local human impacts. These same models performed poorly and lost explanatory power when fitted anew to populated (human impacted) islands; biophysical decoupling was clearly evident. Furthermore, key biophysical relationships at populated islands (i.e. those relationships driving benthic variation across space in conjunction with chronic human impact) bore little resemblance to the baseline scenarios identified from unpopulated islands. Our results highlight the ability of local human impacts to decouple biophysical relationships in the marine environment and fundamentally restructure the natural rules of nature. [ABSTRACT FROM AUTHOR]

Variability in primary productivity and fishing pressure can shape the abundance, species composition, and diversity of marine life. Though parasites comprise nearly half of marine species, their responses to these important forces remain little explored. We quantified parasite assemblages at two spatial scales, across a gradient in productivity and fishing pressure that spans six coral islands of the Line Islands archipelago and within the largest Line Island, Kiritimati, which experiences a west-to-east gradient in fishing pressure and upwelling-driven productivity. In the across-islands data set, we found that increasing productivity was correlated with increased parasite abundance overall, but that the effects of productivity differed among parasite groups. Trophically transmitted parasites increased in abundance with increasing productivity, but directly transmitted parasites did not exhibit significant changes. This probably arises because productivity has stronger effects on the abundance of the planktonic crustaceans and herbivorous snails that serve as the intermediate hosts of trophically transmitted parasites than on the higher-trophic level fishes that are the sole hosts of directly transmitted parasites. We also found that specialist parasites increased in response to increasing productivity, while generalists did not, possibly because specialist parasites tend to be more strongly limited by host availability than are generalist parasites. After the effect of productivity was controlled for, fishing was correlated with decreases in the abundance of trophically transmitted parasites, while directly transmitted parasites appeared to track host density; we observed increases in the abundance of parasites using hosts that experienced fishing-driven compensatory increases in abundance. The within-island data set confirmed these patterns for the combined effects of productivity and fishing on parasite abundance, suggesting that our conclusions are robust across a span of spatial scales. Overall, these results indicate that there are strong and variable effects of anthropogenic and natural drivers on parasite abundance and taxonomic richness. These effects are likely to be mediated by parasite traits, particularly by parasite transmission strategies. [ABSTRACT FROM AUTHOR]

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