Paolo Momigliano

Limited ecological population connectivity suggests low demands on self-recruitment in a tropical inshore marine fish (Eleutheronema tetradactylum: Polynemidae)

The diversity of geographic scales at which marine organisms display genetic variation mirrors the biophysical and ecological complexity of dispersal by pelagic larvae. Yet little is known about the effect of larval ecology on genetic population patterns, partly because detailed data of larval ecology do not yet exist for most taxa. One species for which this data is available is Eleutheronema tetradactylum, a tropical Indo‐West Pacific shorefish. Here, we use a partial sequence mitochondrial cytochrome oxidase subunit 1 (COI) marker and five microsatellite loci to survey the genetic structure of E. tetradactylum across northern Australia. Structure was found throughout the range and isolation by distance was strong, explaining approximately 87 and 64% of the genetic variation in microsatellites and mtDNA, respectively. Populations separated by as little as 15 km also showed significant genetic structure, implying that local populations are mainly insular and self‐seeding on an ecological time frame. Because the larvae of E. tetradactylum have lower swimming performance and poor orientation compared with other tropical fishes, even modest larval abilities may permit self‐recruitment rather than passive dispersal.

The diversity of Coolia spp. (Dinophyceae Ostreopsidaceae) in the central great barrier reef region.

Background Dinoflagellates are important primary producers, crucial in marine food webs. Toxic strains, however, are the main causative agents of non-bacterial seafood poisoning, a major concern for public health worldwide. Despite their importance, taxonomic uncertainty within many genera of dinoflagellates is still high. The genus Coolia includes potentially harmful species and the diversity within the genus is just starting to become apparent. Methodology/Principal Findings In the current study, cultures were established from strains of Coolia spp. isolated from the central Great Barrier Reef (GBR). Cultures were identified based on thecal plate morphology and analyses of sequences (18S, ITS and 28S) from the nuclear rRNA operon. We report that the central GBR harbors a high diversity of Coolia species, including two species known to be capable of toxin production (C. tropicalis and C. malayensis), as well as the non-toxic C. canariensis. The strain of C. canariensis isolated from the GBR may in fact be a cryptic species, closely related but nevertheless phylogenetically distinct from the strain on which the holotype of C. canariensis was based. We also found evidence of the occurrence of a cryptic species morphologically very similar to both C. malayensis and C. monotis. The consequences of taxonomic confusion within the genus are discussed. Conclusion/Significance The central GBR region harbors a previously unreported high diversity of Coolia spp., including two species known to potentially produce toxins. The presence of a cryptic species of unknown toxicity highlights the importance of cryptic diversity within dinoflagellates.

Extraordinarily rapid speciation in a marine fish

Significance Divergent selection can lead to the evolution of distinct species, a process known as ecological speciation. Evidence for ecological speciation in the marine environment is scarce, and the few known examples have happened within a time frame of hundreds of thousands to millions of years. We present evidence that European flounders in the Baltic Sea exhibiting different breeding behaviors are a species pair arising from a recent event of ecological speciation. The two lineages diverged within less than 3,000 generations. This is the fastest event of speciation ever reported for any marine vertebrate. Extraordinarily rapid speciation driven by natural selection can therefore happen even in the marine environment. Divergent selection may initiate ecological speciation extremely rapidly. How often and at what pace ecological speciation proceeds to yield strong reproductive isolation is more uncertain. Here, we document a case of extraordinarily rapid speciation associated with ecological selection in the postglacial Baltic Sea. European flounders (Platichthys flesus) in the Baltic exhibit two contrasting reproductive behaviors: pelagic and demersal spawning. Demersal spawning enables flounders to thrive in the low salinity of the Northern Baltic, where eggs cannot achieve neutral buoyancy. We show that demersal and pelagic flounders are a species pair arising from a recent event of speciation. Despite having a parapatric distribution with extensive overlap, the two species are reciprocally monophyletic and show strongly bimodal genotypic clustering and no evidence of contemporary migration, suggesting strong reproductive isolation. Divergence across the genome is weak but shows strong signatures of selection, a pattern suggestive of a recent ecological speciation event. We propose that spawning behavior in Baltic flounders is the trait under ecologically based selection causing reproductive isolation, directly implicating a process of ecological speciation. We evaluated different possible evolutionary scenarios under the approximate Bayesian computation framework and estimate that the speciation process started in allopatry ∼2,400 generations ago, following the colonization of the Baltic by the demersal lineage. This is faster than most known cases of ecological speciation and represents the most rapid event of speciation ever reported for any marine vertebrate.

Connectivity in grey reef sharks (Carcharhinus amblyrhynchos) determined using empirical and simulated genetic data

Grey reef sharks (Carcharhinus amblyrhynchos) can be one of the numerically dominant high order predators on pristine coral reefs, yet their numbers have declined even in the highly regulated Australian Great Barrier Reef (GBR) Marine Park. Knowledge of both large scale and fine scale genetic connectivity of grey reef sharks is essential for their effective management, but no genetic data are yet available. We investigated grey reef shark genetic structure in the GBR across a 1200 km latitudinal gradient, comparing empirical data with models simulating different levels of migration. The empirical data did not reveal any genetic structuring along the entire latitudinal gradient sampled, suggesting regular widespread dispersal and gene flow of the species throughout most of the GBR. Our simulated datasets indicate that even with substantial migrations (up to 25% of individuals migrating between neighboring reefs) both large scale genetic structure and genotypic spatial autocorrelation at the reef scale were maintained. We suggest that present migration rates therefore exceed this level. These findings have important implications regarding the effectiveness of networks of spatially discontinuous Marine Protected Areas to protect reef sharks.

Conserving coral reef organisms that lack larval dispersal: are networks of Marine Protected Areas good enough?

INTRODUCTION Coral reef ecosystems are under increasing threat due to the synergistic effects of habitat destruction, overfishing, eutrophication and climate change (Hughes et al., 2003, 2007; Hoegh-Guldberg et al., 2007). In response to these threats, management strategies that implement networks of Marine Protected Areas (MPAs) have gained momentum in the past few decades. Networks of MPAs can protect coral reef biodiversity from anthropogenic impacts either by eliminating the impacts of overfishing and habitat destruction, or by increasing ecosystem resilience to other anthropogenic disturbances (Russ and Zeller, 2003; McCook et al., 2010). For networks of MPAs to be effective they must meet three key elements. Individual MPAs must be (1) partially self-seeding (Almany et al., 2007, 2009), (2) adequately connected to other MPAs via dispersal (Jones et al., 2007; Almany et al., 2009), and (3) they must protect target organisms during life stages when they are most vulnerable to anthropogenic impact (Zeller and Russ, 1998). Accordingly, MPAs should be large enough to encompass individual home ranges of the target species and to ensure a portion of the larvae produced within a MPA settles within its boundaries (Almany et al., 2009). Furthermore, networks of MPAs must ensure genetic and demographic connectivity between protected areas. Connectivity is defined as the exchange of individuals between populations. Connectivity bolsters local resilience to stochastic demographic fluctuations and in so doing, minimizes genetic erosion, the risk of inbreeding depression and ultimately maximizes adaptive potential (Almany et al., 2009). Here we discuss how different life history strategies may affect the feasibility of achieving the three requirements for effective long-term conservation (selfseeding, connectivity, and protection). While sedentary organisms with a pelagic larval phase (most reef fishes and invertebrates), readily achieve this trinity (Planes et al., 2009), animals where dispersal only occurs as adults inevitably fail to meet all three requirements simultaneously (Figure 1). Here we propose a potential solution focusing on incorporating information on how habitat shapes adult dispersal to increase connectivity within networks of MPAs.

Effects of temperature, salinity and composition of the dinoflagellate assemblage on the growth of Gambierdiscus carpenteri isolated from the Great Barrier Reef

Increases in reported incidence of ciguatera fish poisoning (hereafter ciguatera) have been linked to warmer sea temperatures that are known to trigger coral bleaching events. The drivers that trigger blooms of ciguatera-causing dinoflagellates on the Great Barrier Reef (GBR) are poorly understood. This study investigated the effects of increased temperatures and lowered salinities, often associated with environmental disturbance events, on the population growth of two strains of the potentially ciguatera-causing dinoflagellate, Gambierdiscus carpenteri (NQAIF116 and NQAIF380). Both strains were isolated from the central GBR with NQAIF116 being an inshore strain and NQAIF380 an isolate from a stable environment of a large coral reef aquarium exhibit in ReefHQ, Townsville, Australia. Species of Gambierdiscus are often found as part of a mixed assemblage of benthic toxic dinoflagellates on macroalgal substrates. The effect of assemblage structure of dinoflagellates on the growth of Gambierdiscus populations has, however, not been explored. The study, therefore investigated the growth of G. carpenteri within mixed assemblages of benthic dinoflagellates. Population growth was monitored over a period of 28days under three salinities (16, 26 and 36) and three temperature (24, 28 and 34°C) conditions in a fully crossed experimental design. Temperature and salinity had a significant effect on population growth. Strain NQAIF380 exhibited significantly higher growth at 28°C compared to strain NQAIF116, which had highest growth at 24°C. When strain NQAIF116 was co-cultured with the benthic dinoflagellates, Prorocentrum lima and Ostreopsis sp., inhibitory effects on population growth were observed at a salinity of 36. In contrast, growth stimulation of G. carpenteri (strain NQAIF116) was observed at a salinity of 26 and particularly at 16 when co-cultured with Ostreopsis-dominated assemblages. Range expansion of ciguatera-causing dinoflagellates could lead to higher frequency of reported ciguatera illness in populated temperate Australian regions, outside the tropical range of the GBR. Therefore, the findings on salinity and temperature tolerance of two strains of G. carpenteri indicates potential adaptability to different local environmental conditions. These are baseline data for future investigations into the potential southward range expansion of ciguatera-causing dinoflagellates originating from the GBR.

Predators in danger: shark conservation and management in Australia, New Zealand and their neighbours

In this chapter we examine the biodiversity and the status of conservation and management of shark species in Australasia and Indonesia. Almost 17% of shark species in the region are listed by the International Union for the Conservation of Nature (IUCN) as threatened, and approximately 40% are of conservation concern, their future being dependent on the implementation of appropriate management strategies. Overfishing is a major threat to sharks, as their life-history strategies make them susceptible to even modest levels of fishing mortality. In Australia and New Zealand many shark stocks experienced dramatic declines as a consequence of overfishing; however, in the past few decades substantial improvements in the management of shark fisheries have taken place. On the other hand, shark fishing in Indonesia is largely unreported and unregulated and fishing by Indonesian vessels is likely to have consequences that go beyond the depletion of local populations, affecting shark populations in neighbouring countries such as Australia. We illustrate examples of over fishing in the region, discuss the potential effects of habitat degradation and climate change in the future and examine current management frameworks for the conservation of shark species in the region with an emphasis on the implementation of Nation Plans of Action for the Conservation and Management of Sharks (NPoAs).

Genetic structure and signatures of selection in grey reef sharks (Carcharhinus amblyrhynchos)

With overfishing reducing the abundance of marine predators in multiple marine ecosystems, knowledge of genetic structure and local adaptation may provide valuable information to assist sustainable management. Despite recent technological advances, most studies on sharks have used small sets of neutral markers to describe their genetic structure. We used 5517 nuclear single-nucleotide polymorphisms (SNPs) and a mitochondrial DNA (mtDNA) gene to characterize patterns of genetic structure and detect signatures of selection in grey reef sharks (Carcharhinus amblyrhynchos). Using samples from Australia, Indonesia and oceanic reefs in the Indian Ocean, we established that large oceanic distances represent barriers to gene flow, whereas genetic differentiation on continental shelves follows an isolation by distance model. In Australia and Indonesia differentiation at nuclear SNPs was weak, with coral reefs acting as stepping stones maintaining connectivity across large distances. Differentiation of mtDNA was stronger, and more pronounced in females, suggesting sex-biased dispersal. Four independent tests identified a set of loci putatively under selection, indicating that grey reef sharks in eastern Australia are likely under different selective pressures to those in western Australia and Indonesia. Genetic distances averaged across all loci were uncorrelated with genetic distances calculated from outlier loci, supporting the conclusion that different processes underpin genetic divergence in these two data sets. This pattern of heterogeneous genomic differentiation, suggestive of local adaptation, has implications for the conservation of grey reef sharks; furthermore, it highlights that marine species showing little genetic differentiation at neutral loci may exhibit patterns of cryptic genetic structure driven by local selection.

First records of the grey nurse shark Carcharias taurus (Lamniformes: Odontaspididae) from oceanic coral reefs in the Timor Sea

The threatened grey nurse shark (Carcharias taurus) is reported for the first time from oceanic coral reefs in the Timor Sea. Generally known from temperate and subtropical coastal reef habitats, this species was encountered by Indonesian traditional fishers on oceanic coral reefs in an area of the Australian Exclusive Economic Zone known as the 1974 MoU Box, some 200 km from the Australian mainland. The presence of C. taurus on these remote tropical reefs bears important management implications, including the species’ protected status in Australian waters and the challenges of regulating catches in areas permitted for traditional Indonesian fishing.

New distribution records of the Vulnerable fossil shark Hemipristis elongata from eastern Indonesia call for improved fisheries management

Genetically verified catch data from fishers in eastern Indonesia provide new distribution records for the fossil shark Hemipristis elongata in the Halmahera, Seram and Arafura seas. Previously only recorded from the island of Java, this study reports a range extension for this species of >2000Â km across the Indonesian archipelago, suggesting that fossil sharks are subjected to fishing pressure over a much larger geographic area than implied by previous species records. We recommend a review of the current species assessment to reflect the reported range extension and inform management of this fishery-Targeted shark.