A modern scleractinian coral with a two-component calcite-aragonite skeleton.

One of the most conserved traits in the evolution of biomineralizing organisms is the taxon-specific selection of skeletal minerals. All modern scleractinian corals are thought to produce skeletons exclusively of the calcium-carbonate polymorph aragonite. Despite strong fluctuations in ocean chemistry (notably the Mg/Ca ratio), this feature is believed to be conserved throughout the coral fossil record, spanning more than 240 million years. Only one example, the Cretaceous scleractinian coral Coelosmilia (ca. 70 to 65 Ma), is thought to have produced a calcitic skeleton. Here, we report that the modern asymbiotic scleractinian coral Paraconotrochus antarcticus living in the Southern Ocean forms a two-component carbonate skeleton, with an inner structure made of high-Mg calcite and an outer structure composed of aragonite. P. antarcticus and Cretaceous Coelosmilia skeletons share a unique microstructure indicating a close phylogenetic relationship, consistent with the early divergence of P. antarcticus within the Vacatina (i.e., Robusta) clade, estimated to have occurred in the Mesozoic (ca. 116 Mya). Scleractinian corals thus join the group of marine organisms capable of forming bimineralic structures, which requires a highly controlled biomineralization mechanism; this capability dates back at least 100 My. Due to its relatively prolonged isolation, the Southern Ocean stands out as a repository for extant marine organisms with ancient traits.

Bamboozled! Resolving deep evolutionary nodes within the phylogeny of bamboo corals (Octocorallia: Scleralcyonacea: Keratoisididae).

Keratoisididae is a globally distributed, and exclusively deep-sea, family of octocorals that contains species and genera that are polyphyletic. An alphanumeric system, based on a three-gene-region phylogeny, is widely used to describe the biodiversity within this family. That phylogeny identified 12 major groups although it did not have enough signal to explore the relationships among groups. Using increased phylogenomic resolution generated from Ultraconserved Elements and exons (i.e. conserved elements), we aim to resolve deeper nodes within the family and investigate the relationships among those predefined groups. In total, 109 libraries of conserved elements were generated from individuals representing both the genetic and morphological diversity of our keratoisidids. In addition, the conserved element data of 12 individuals from previous studies were included. Our taxon sampling included 11 of the 12 keratoisidid groups. We present two phylogenies, constructed from a 75% (231 loci) and 50% (1729 loci) taxon occupancy matrix respectively, using both Maximum Likelihood and Multiple Species Coalescence methods. These trees were congruent at deep nodes. As expected, S1 keratoisidids were recovered as a well-supported sister clade to the rest of the bamboo corals. S1 corals do not share the same mitochondrial gene arrangement found in other members of Keratoisididae. All other bamboo corals were recovered within two major clades. Clade I comprises individuals assigned to alphanumeric groups B1, C1, D1&D2, F1, H1, I4, and J3 while Clade II contains representatives from A1, I1, and M1. By combining genomics with already published morphological data, we provide evidence that group H1 is not monophyletic, and that the division between other groups - D1 and D2, and A1 and M1 - needs to be reconsidered. Overall, there is a lack of robust morphological markers within Keratoisididae, but subtle characters such as sclerite microstructure and ornamentation seem to be shared within groups and warrant further investigation as taxonomically diagnostic characters.

An assessment of people living by coral reefs over space and time.

Human populations near ecosystems are used as both a proxy for dependency on ecosystems, and conversely to estimate threats. Consequently, the number of people living near coral reefs is often used in regional coral reef management, evaluation of risk at regional and global scales, and even considerations of funding needs. Human populations and their statistics, are ever-changing and data relating to coral reefs have not been updated regularly. Here, we present an up-to-date analysis of the abundance, and density of people living within 5-100 km of coral reef ecosystems along with population proportion, using freely available data sets and replicable methods. We present trends of changes in human populations living near coral reefs over a 20-year time period (2000-2020), divided by region and country, along with socio-economic denominations such as country income category and Small Island Developing States (SIDS). We find that across 117 coral reef countries there are currently close to a billion people living within 100 km of a coral reef (~13% of the global population) compared with 762 million people in 2000. Population growth by coral reefs is higher than global averages. The Indian Ocean saw a 33% increase in populations within 100 km of a coral reef and 71% at 5 km. There are 60 countries with 100% of their population within 100 km of coral reefs. In SIDS, the proportion of the total population within 100 km of a coral reef is extremely high: 94% in 2020. Population density 5-10 km from coral reefs is 4× the global average. From 5 to 100 km, more people from lower-middle-income countries live by coral reefs than any other income category. Our findings provide the most up-to-date and extensive statistics on the regional and nation-level differences in population trends that play a large role in coral reef health and survival.

Opposite environmental and genetic influences on body size in North American Drosophila pseudoobscura.

BACKGROUND: Populations of a species often differ in key traits. However, it is rarely known whether these differences are associated with genetic variation and evolved differences between populations, or are instead simply a plastic response to environmental differences experienced by the populations. Here we examine the interplay of plasticity and direct genetic control by investigating temperature-size relationships in populations of Drosophila pseudoobscura from North America. We used 27 isolines from three populations and exposed them to four temperature regimes (16°C, 20°C, 23°C, 26°C) to examine environmental, genetic and genotype-by-environment sources of variance in wing size. RESULTS: By far the largest contribution to variation in wing size came from rearing temperature, with the largest flies emerging from the coolest temperatures. However, we also found a genetic signature that was counter to this pattern as flies originating from the northern, cooler population were consistently smaller than conspecifics from more southern, warmer populations when reared under the same laboratory conditions. CONCLUSIONS: We conclude that local selection on body size appears to be acting counter to the environmental effect of temperature. We find no evidence that local adaptation in phenotypic plasticity can explain this result, and suggest indirect selection on traits closely linked with body size, or patterns of chromosome inversion may instead be driving this relationship.

Evolutionary dynamics of a common sub-Antarctic octocoral family.

Sequence data were obtained for five different loci, both mitochondrial (cox1, mtMutS, 16S) and nuclear (18S, 28S rDNA), from 64 species representing 25 genera of the common deep-sea octocoral family Primnoidae. We tested the hypothesis that Primnoidae have an Antarctic origin, as this is where they currently have high species richness, using Maximum likelihood and Bayesian inference methods of phylogenetic analysis. Using a time-calibrated molecular phylogeny we also investigated the time of species radiation in sub-Antarctic Primnoidae. Our relatively wide taxon sampling and phylogenetic analysis supported Primnoidae as a monophyletic family. The base of the well-supported phylogeny was Pacific in origin, indicating Primnoidae sub-Antarctic diversity is a secondary species radiation. There is also evidence for a subsequent range extension of sub-Antarctic lineages into deep-water areas of the Indian and Pacific Oceans. Conservative and speculative fossil-calibration analyses resulted in two differing estimations of sub-Antarctic species divergence times. Conservative analysis suggested a sub-Antarctic species radiation occurred ∼52MYA (95% HPD: 36-73MYA), potentially before the opening of the Drake Passage and Antarctic Circumpolar Current (ACC) formation (41-37MYA). Speculative analysis pushed this radiation back into the late Jurassic, 157MYA (95% HPD: 118-204MYA). Genus-level groupings were broadly supported in this analysis with some notable polyphyletic exceptions: Callogorgia, Fanellia, Primnoella, Plumarella, Thouarella. Molecular and morphological evidence supports the placement of Tauroprimnoa austasensis within Dasystenella and Fannyella kuekenthali within Metafannyella.

Does polyandry control population sex ratio via regulation of a selfish gene?

The extent of female multiple mating (polyandry) can strongly impact on the intensity of sexual selection, sexual conflict, and the evolution of cooperation and sociality. More subtly, polyandry may protect populations against intragenomic conflicts that result from the invasion of deleterious selfish genetic elements (SGEs). SGEs commonly impair sperm production, and so are likely to be unsuccessful in sperm competition, potentially reducing their transmission in polyandrous populations. Here, we test this prediction in nature. We demonstrate a heritable latitudinal cline in the degree of polyandry in the fruitfly Drosophila pseudoobscura across the USA, with northern population females remating more frequently in both the field and the laboratory. High remating was associated with low frequency of a sex-ratio-distorting meiotic driver in natural populations. In the laboratory, polyandry directly controls the frequency of the driver by undermining its transmission. Hence we suggest that the cline in polyandry represents an important contributor to the cline in sex ratio in nature. Furthermore, as the meiotic driver causes sex ratio bias, variation in polyandry may ultimately determine population sex ratio across the USA, a dramatic impact of female mating decisions. As SGEs are ubiquitous it is likely that the reduction of intragenomic conflict by polyandry is widespread.

Antarctic Seabed Assemblages in an Ice-Shelf-Adjacent Polynya, Western Weddell Sea.

Ice shelves cover ~1.6 million km2 of the Antarctic continental shelf and are sensitive indicators of climate change. With ice-shelf retreat, aphotic marine environments transform into new open-water spaces of photo-induced primary production and associated organic matter export to the benthos. Predicting how Antarctic seafloor assemblages may develop following ice-shelf loss requires knowledge of assemblages bordering the ice-shelf margins, which are relatively undocumented. This study investigated seafloor assemblages, by taxa and functional groups, in a coastal polynya adjacent to the Larsen C Ice Shelf front, western Weddell Sea. The study area is rarely accessed, at the frontline of climate change, and located within a CCAMLR-proposed international marine protected area. Four sites, ~1 to 16 km from the ice-shelf front, were explored for megabenthic assemblages, and potential environmental drivers of assemblage structures were assessed. Faunal density increased with distance from the ice shelf, with epifaunal deposit-feeders a surrogate for overall density trends. Faunal richness did not exhibit a significant pattern with distance from the ice shelf and was most variable at sites closest to the ice-shelf front. Faunal assemblages significantly differed in composition among sites, and those nearest to the ice shelf were the most dissimilar; however, ice-shelf proximity did not emerge as a significant driver of assemblage structure. Overall, the study found a biologically-diverse and complex seafloor environment close to an ice-shelf front and provides ecological baselines for monitoring benthic ecosystem responses to environmental change, supporting marine management.

Coral reef carnivorous fish biomass relates to oceanographic features depending on habitat and prey preference.

Carnivorous fish are a key part of the Indonesian human population sustenance, and it is important to design marine protected areas that include environmental features that allow these species to thrive. Many studies report the role of coral cover and habitat complexity in determining fish distribution on coral reefs but broader environmental factors such as current velocity and productivity are less studied. Southern Indonesia is characterised by upwellings and strong currents, stemming from the tidal cycle and the Indonesian Throughflow. In this study we investigate how current velocity, chlorophyll-a (chl-a), sea surface height and temperature relate to the biomass of carnivorous fish, considering the influence of habitat complexity and coral cover. Data were collected by surveying seven sites around Nusa Penida MPA for a total of 97 h of observation. Serranids and Lutjanids showed higher dependency on coral cover than fish from family Lethrinidae, Carangidae and Scombridae for which current, sea surface height, chl-a, and temperature were more influential predictors. Considering the similar trophic ecology of these species, the different relationship with oceanographic factors is likely related to different body shapes, living, and feeding habits between fish families. Changes in sea surface temperature and current velocity induced by vertical mixing are affecting coral reef fisheries-targeted species distribution in Nusa Penida and investigating these relationships on a broader scale will better inform marine spatial planning decisions.

An illustrated key to the species of the genus Narella (Cnidaria, Octocorallia, Primnoidae).

A history of the description of the 50 valid species of Narella is given, beginning with the first species described in 1860. To help differentiate the various species, a tabular and a polychotomous key are provided. The species in the keys are arranged using nine characters or character sets that are believed to be of value at the species level. New characters or new significance given to previously described characters used in our keys include: 1) the nature of the dorsolateral edge of the basal scale, being ridged or not, 2) the thickness of the body wall scales, and 3) the arrangement of the coenenchymal scales (imbricate or mosaic), their thickness (thin or massive), and their outer surface ornamentation (ridged or not). All characters used in the keys are illustrated.

Author Correction: Species replacement dominates megabenthos beta diversity in a remote seamount setting.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Species replacement dominates megabenthos beta diversity in a remote seamount setting.

Seamounts are proposed to be hotspots of deep-sea biodiversity, a pattern potentially arising from increased productivity in a heterogeneous landscape leading to either high species co-existence or species turnover (beta diversity). However, studies on individual seamounts remain rare, hindering our understanding of the underlying causes of local changes in beta diversity. Here, we investigated processes behind beta diversity using ROV video, coupled with oceanographic and quantitative terrain parameters, over a depth gradient in Annan Seamount, Equatorial Atlantic. By applying recently developed beta diversity analyses, we identified ecologically unique sites and distinguished between two beta diversity processes: species replacement and changes in species richness. The total beta diversity was high with an index of 0.92 out of 1 and was dominated by species replacement (68%). Species replacement was affected by depth-related variables, including temperature and water mass in addition to the aspect and local elevation of the seabed. In contrast, changes in species richness component were affected only by the water mass. Water mass, along with substrate also affected differences in species abundance. This study identified, for the first time on seamount megabenthos, the different beta diversity components and drivers, which can contribute towards understanding and protecting regional deep-sea biodiversity.

Exceptional biodiversity of the cryptofaunal decapods in the Chagos Archipelago, central Indian Ocean.

The Chagos Archipelago is geographically remote and isolated from most direct anthropogenic pressures. Here, we quantify the abundance and diversity of decapod crustaceans inhabiting dead coral colonies, representing a standardised microhabitat, across the Archipelago. Using morphological and molecular techniques we recorded 1868 decapods from 164 nominal species within 54 dead coral colonies, but total species estimates (Chao1 estimator) calculate at least 217 species. Galatheids were the most dominant taxa, though alpheids and hippolytids were also very abundant. 32% of species were rare, and 46% of species were found at only one atoll. This prevalence of rarer species has been reported in other cryptofauna studies, suggesting these assemblages maybe comprised of low-abundance species. This study provides the first estimate of diversity for reef cryptofauna in Chagos, which will serve as a useful baseline for global comparisons of coral reef biodiversity.

Trait and phylogenetic diversity provide insights into community assembly of reef-associated shrimps (Palaemonidae) at different spatial scales across the Chagos Archipelago.

Coral reefs are the most biodiverse marine ecosystem and one of the most threatened by global climate change impacts. The vast majority of diversity on reefs is comprised of small invertebrates that live within the reef structure, termed the cryptofauna. This component of biodiversity is hugely understudied, and many species remain undescribed. This study represents a rare analysis of assembly processes structuring a distinct group of cryptofauna, the Palaemonidae, in the Chagos Archipelago, a reef ecosystem under minimal direct human impacts in the central Indian Ocean. The Palaemonidae are a diverse group of Caridae (infraorder of shrimps) that inhabit many different niches on coral reefs and are of particular interest because of their varied habitat associations. Phylogenetic and trait diversity and phylogenetic signal were used to infer likely drivers of community structure. The mechanisms driving palaemonid community assembly and maintenance in the Chagos Archipelago showed distinct spatial patterns. At local scales, among coral colonies and among reefs fringing individual atolls, significant trait, and phylogenetic clustering patterns suggest environmental filtering may be a dominant ecological process driving Palaemonidae community structure, although local competition through equalizing mechanisms may also play a role in shaping the local community structure. Importantly, we also tested the robustness of phylogenetic diversity to changes in evolutionary information as multi-gene phylogenies are resource intensive and for large families, such as the Palaemonidae, are often incomplete. These tests demonstrated a very modest impact on phylogenetic community structure, with only one of the four genes (PEPCK gene) in the phylogeny affecting phylogenetic diversity patterns, which provides useful information for future studies on large families with incomplete phylogenies. These findings contribute to our limited knowledge of this component of biodiversity in a marine locality as close to undisturbed by humans as can be found. It also provides a rare evaluation of phylogenetic diversity methods.

Graduate mental health worker case management of depression in UK primary care: a pilot study.

BACKGROUND: Based on data from large multicentre US trials, the National Institute for Health and Clinical Excellence (NICE) is advocating a stepped-care model for the management of depression, with 'case management' or 'collaborative care' for selected patients in primary care. AIM: To conduct a pilot study examining the use of graduate mental health workers case managing depressed primary care NHS patients. DESIGN OF STUDY: A randomised controlled trial comparing usual GP care with or without case management over 16 weeks of acute antidepressant drug treatment. SETTING: Three primary care practices in the North East of England. METHOD: Patients with depression, aged 18-65 years, who had failed to adequately respond to antidepressant treatment, were randomised to the two treatments. Assessments were made at baseline, 12, and 24 weeks using a combination of observer and self ratings. RESULTS: Randomisation of 62 patients required screening of 1073 potential patients. There was little difference in outcome between the two treatment arms but a gradual improvement in symptoms over time was seen. Client satisfaction was assessed as high across both treatments. CONCLUSION: While this pilot study confirmed the integrity of the study protocol and the suitability of the outcome measures and randomisation procedure, it raises questions regarding the practicality of recruitment and feasibility of the intervention. It would be crucial to address these issues prior to the implementation of a large multi-centre randomised controlled trial.

Temperature can shape a cline in polyandry, but only genetic variation can sustain it over time.

Multiple mating by females (polyandry) is a widespread behavior occurring in diverse taxa, species, and populations. Polyandry can also vary widely within species, and individual populations, so that both monandrous and polyandrous females occur together. Genetic differences can explain some of this intraspecific variation in polyandry, but environmental factors are also likely to play a role. One environmental factor that influences many fundamental biological processes is temperature. Higher temperatures have been shown to directly increase remating in laboratory studies of insects. In the longer term, high temperature could also help to drive the evolution of larger-scale patterns of behavior by changing the context-dependent balance of costs and benefits of polyandry across environments. We examined the relative influence of rearing and mating temperatures on female remating in populations of Drosophila pseudoobscura that show a latitudinal cline in polyandry in nature, using a range of ecologically relevant temperatures. We found that females of all genotypes remated more at cooler temperatures, which fits with the observation of higher average frequencies of polyandry at higher latitudes in this species. However, the impact of temperature was outweighed by the strong genetic control of remating in females in this species. It is likely that genetic factors provide the primary explanation for the latitudinal cline in polyandry in this species.

Polyandry in nature: a global analysis.

A popular notion in sexual selection is that females are polyandrous and their offspring are commonly sired by more than a single male. We now have large-scale evidence from natural populations to be able to verify this assumption. Although we concur that polyandry is a generally common and ubiquitous phenomenon, we emphasise that it remains variable. In particular, the persistence of single paternity, both within and between populations, requires more careful consideration. We also explore an intriguing relation of polyandry with latitude. Several recent large-scale analyses of the relations between key population fitness variables, such as heterozygosity, effective population size (Ne), and inbreeding coefficients, make it possible to examine the global effects of polyandry on population fitness for the first time.