A glaring omission in Australia’s marine conservation planning

The primary goal of Australia’s National Representative System of Marine Protected Areas(NRSMPA) is to establish a comprehensive, adequate and representative system of MPAs. This study identifies a glaring contradiction to this policy. The provinces of Christmas and Cocos Islands are among the most unique and threatened marine bioregions in Australia, yet receive no protection from the NRSMPA. The lack of protection appears to be due to difficulties with multiple governance arrangements and other political priorities. These issues have already caused biodiversity loss in the terrestrial environment of these bioregions. The Australian Government must include the Christmas and Cocos provinces in the NRSMPA other wise it risks irreversible loss of marine biodiversity in these unique bioregions

Hybridisation among coral reef fishes at Christmas Island and the Cocos (Keeling) Islands

Hybridisation is common among terrestrial and freshwater species, but is considered rare and insignificant in marine systems. Christmas and Cocos (Keeling) Islands represent a recently discovered marine suture zone that contains a high number of hybridising coral reef fishes. In this study we document a further eight species that are hybridising, bringing the total number of reported hybrid crosses to 15, involving 27 species across eight families. So far, eight of the 15 hybrid crosses have been genetically confirmed. There is a taxonomic bias to this hybridisation,with chaetodontids and acanthurids containing the greatest number of hybridising species. Hybridisation commonly involves Indian and Pacific Ocean sister species that are coming into secondary contact. In most cases, at least one parent species is rare and the lack of conspecific partners is leading to the formation of heterospecific social groups and the breakdown of assortative mating. The discovery of this hybrid hotspot provides a unique and importantopportunity to examine speciation in the marine environment

The status of hard coral diversity at Christmas Island and Cocos (Keeling) Islands

Very little is known about the coral biodiversity in Australia’s remote Indian Ocean Territories; hence it is not possible to detect extinctions, depletions or to quantify changes in the coral fauna. Here we document the results of rapid visual assessment surveys of hard coral biodiversity at Christmas Island. This study provides a much-needed updated species list as well as a baseline dataset on coral community composition that will enable detection of future changes in the community. From this survey, a total of 145 species of scleractinian coral and five species of non-scleractinian coral (three hydrozoans and two octocorals) from 51 genera were recorded, including 28 range extensions. When combined with existing specimen-based records, the current estimate of hard coral species richness at Christmas Island is 169, and comparable to communities at other isolated Indian Ocean localities. In conjunction with the results of a previous study at neighbouring Cocos (Keeling) Islands, the total number of hard corals recorded from Australia’s Indian Ocean Territories is 197 species. The composition of the coral community is biogeographically unique and its long-term conservation is dependent on greater protection from local pollution impacts to safeguard resilience

Optimal monitoring of coral biodiversity at Christmas Island

Abstract. Coral reefs are one of the most biodiverse ecosystems in the world and are increasingly at risk due to a range of threats. Detailed species-level data is essential in developing effective management strategies for the conservation of coral reef biodiversity. For hard corals, this critical information is rarely available due to the high degree of expertise, time and costs involved in collecting species-level data, hence, the development of proxy metrics which accurately and reliably reflect coral species richness are imperative. At Christmas Island, in the north-easternIndian Ocean, little species-level baseline data is available to inform managers regarding spatial (or temporal) variations of coral diversity. Here we examine the ability of four proxy metrics to reflect patterns in hard coral species richness, compared across depth gradients at eight sites around Christmas Island using regression analysis. Generic richness measured on a belt transect was the strongest explanatory variable for species richness (68–88% variation explained) regardless of the scale of analysis. Percent live hard coral cover has traditionally been used to assess and monitor coral reef health; however, our results suggest that it is not related to coral species richness asa significant linear function. Overall, at Christmas Island, monitoring generic richness on replicated belt transects offers the simplest and most robust proxy metric for estimating species richness

Does genetic distance between parental species influence outcomes of hybridization among coral reef butterflyfishes?

Christmas Island is located at the overlap of the Indian and Pacific Ocean marine provinces and is a hot spot for marine hybridization. Here, we evaluate the ecological framework and genetic consequences of hybridization between butterflyfishes Chaetodon guttatissimus and Chaetodon punctatofasciatus. Further, we compare our current findings to those from a previous study of hybridization between Chaetodon trifasciatus and Chaetodon lunulatus. For both species groups, habitat and dietary overlap between parental species facilitate frequent heterospecific encounters. Low abundance of potential mates promotes heterospecific pair formation and the breakdown of assortative mating. Despite similarities in ecological frameworks, the population genetic signatures of hybridization differ between the species groups. Mitochondrial and nuclear data from C. guttatissimus × C. punctatofasciatus (1% divergence at cyt b) show bidirectional maternal contributions and relatively high levels of introgression, both inside and outside the Christmas Island hybrid zone. In contrast, C. trifasciatus × C. lunulatus (5% cyt b divergence) exhibit unidirectional mitochondrial inheritance and almost no introgression. Back-crossing of hybrid C. guttatissimus × C. punctatofasciatus and parental genotypes may eventually confound species-specific signals within the hybrid zone. In contrast, hybrids of C. trifasciatus and C. lunulatus may coexist with and remain genetically distinct from the parents. Our results, and comparisons with hybridization studies in other reef fish families, indicate that genetic distance between hybridizing species may be a factor influencing outcomes of hybridization in reef fish, which is consistent with predictions from terrestrially derived hybridization theory

Recent advances in understanding the effects of climate change on coral reefs

Climate change is one of the greatest threats to the persistence of coral reefs. Sustained and ongoing increases in ocean temperatures and acidification are altering the structure and function of reefs globally. Here, we summarise recent advances in our understanding of the effects of climate change on scleractinian corals and reef fish. Although there is considerable among-species variability in responses to increasing temperature and seawater chemistry, changing temperature regimes are likely to have the greatest influence on the structure of coral and fish assemblages, at least over short–medium timeframes. Recent evidence of increases in coral bleaching thresholds, local genetic adaptation and inheritance of heat tolerance suggest that coral populations may have some capacity to respond to warming, although the extent to which these changes can keep pace with changing environmental conditions is unknown. For coral reef fishes, current evidence indicates increasing seawater temperature will be a major determinant of future assemblages, through both habitat degradation and direct effects on physiology and behaviour. The effects of climate change are, however, being compounded by a range of anthropogenic disturbances, which may undermine the capacity of coral reef organisms to acclimate and/or adapt to specific changes in environmental conditions

Fishes of the Cocos (Keeling) Islands: new records, community composition and biogeographic significance

The Cocos (Keeling) Islands comprise the most isolated oceanic atoll in the tropical Indian Ocean and are situated 1000 km south-west of Indonesia. The remoteness of the islands has shaped the composition of marine communities but also limited scientific research. This study summarises field research on the marine fishes of the Cocos (Keeling) Islands over the last 14 years (2001–2014). Sixty-seven new records (from 28 families) are described and raise the total number of known fishes to 602 species from 84 families. New records span a variety of body sizes (3 cm TL Gobiodon unicolor to 500 cm TL Rhincodon typus), were observed in all major habitats,and found at both the Southern Atoll and at North Keeling Island. Notable new records include first records for the families Alopiidae, Coryphaenidae, Eleotridae, Gempylidae, Istiophoridae, Molidae, Polymixiidae, Rhincodontidae, Sillaginidae and Xiphiidae. Sampling from pelagic and deepwater (60–300 m) reef environments significantly increased the number of species described from these habitats. New records include species that have dispersed more than 2500 km (Centropyge acanthops) and dispersal ability appears to explain the lack of syngnathids and the high representation of acanthurids and holocentrids in the community. Some of the Indian Ocean species that have colonised the Cocos (Keeling) Islands now co-occur with their Pacific Ocean sister species, increasing the potential for hybridisation. Although the fish community of the Cocos (Keeling) Island resembles that of the Indo-West Pacific, the isolation and co-occurrence of Indian and Pacific Ocean species distinguishes it from all other locations