Banishing bandits: other countries bear the cost
A new study reveals the strategies that stop bandits from illegally fishing in Australian waters—but warns there is a cost to the region’s poorer countries. Co-author Dr Brock Bergseth, from th
Understanding of the links between coral reef ecosystems, the goods and services they provide to people, and the wellbeing of human societies.
Examining the multi-scale dynamics of reefs, from population dynamics to macroevolution
Advancing the fundamental understanding of the key processes underpinning reef resilience.
ARC Centre of Excellence for Coral Reef Studies
James Cook University Townsville
Queensland 4811 Australia
Phone: 61 7 4781 4000
Tropical oceans teem with the dazzle and flash of colourful reef fishes, and contain far more species than the cold ocean waters found at high latitudes. This “latitudinal diversity gradient” is one of the most famous patterns in biology, and scientists have puzzled over its causes for more than 200 years.
A common explanation for the gradient is that warm reef environments serve as evolutionary hot spots for species formation. But a new study led by researchers at University of Michigan and the Australian Research Council Centre of Excellence for Coral Reef Studies (Coral CoE), has analyzed the evolutionary relationships between more than 30,000 fish species and found that the fastest rates of species formation have occurred at the highest latitudes and in the coldest ocean waters.
Over the past several million years, cool-water and polar ocean fishes formed new species twice as fast as the average species of tropical fish, according to the new study, published today in the prestigious journal Nature.
“These findings are both surprising and paradoxical,” said University of Michigan evolutionary biologist Daniel Rabosky, lead author of the study.
“We find that speciation is actually fastest in the geographic regions with the lowest species richness,” he said.
The authors admit they cannot fully explain their results, which are incompatible with the idea that the tropics serve as an evolutionary cradle for marine fish diversity.
Common sense suggests that a high rate of new species formation will eventually lead to impressive levels of biodiversity. But that depends on how many of the newly formed species survive and how many go extinct.
“Extinction is the missing piece of this puzzle, but it’s the most difficult thing to understand,” Rabosky explained. “We’re now using both fossils and new statistical tools to try to get a handle on what extinction might have been doing in both the polar regions and the tropics.”
The researchers tested the widely held assumption that species-formation rates are fastest in the tropics by examining the relationship between latitude, species richness and the rate of new species formation among marine fishes. They assembled a time-calibrated ‘evolutionary tree*’ of all 31,526 ray-finned fish species, then focused their analysis on marine species worldwide.
Surprisingly, some of the fastest rates of new species formation occurred in Antarctic icefish and their relatives. Other temperate and polar groups with exceptionally high speciation rates include snailfish, eelpouts and rockfish.
Three of the largest coral reef-associated fish groups – wrasses, damselfish and gobies – showed low to moderate rates of species formation. “The fact that coral reefs support many more fish species than polar regions despite these lower rates may have a lot to do with their long history of connectivity and ability to act as refugia,” Cowman said.
“Who would have thought that you’d have these really explosive rates of species formation happening in the coldest Antarctic waters, where water is literally at the freezing point and fish, like the icefish, have to have all kinds of really crazy adaptations to live there, like special antifreeze proteins in their blood to keep it from freezing,” Rabosky said.
The paper “An inverse latitudinal gradient in speciation rate for marine fishes” is now available here.
Citation: Rabosky DL, Chang J, Title PO, Cowman PF, Sallan L, Friedman M, Kaschner K, Garilao C, Near TJ, Coll M, Alfaro ME (2018) An inverse latitudinal gradient in speciation rate for marine fishes. Nature 559:392-395
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* Genetic data were available for more than one-third of the fish species analyzed in the study, and the evolutionary tree was time-calibrated using a database of 139 fossil taxa.
* An evolutionary tree, also known as a phylogenetic tree, is a branching diagram showing the inferred evolutionary relationships among various species. The tree assembled for this project is one of the largest time-calibrated phylogenetic trees ever assembled for any group of animals.
* The authors of the Nature paper, in addition to Rabosky and Cowman, are U-M’s Jonathan Chang, Pascal O. Title and Matt Friedman; Michael Alfaro of the University of California, Los Angeles; Lauren Sallan of the University of Pennsylvania; Kristin Kaschner of the University of Freiburg; Cristina Garilao of GEOMAR Helmholtz Centre for Ocean Research; Thomas J. Near of Yale University; and Marta Coll of the Institute of Marine Science in Barcelona, Spain.
* The work was supported in part by grants from the National Science Foundation and by the David and Lucile Packard Foundation.
New research suggests an urgent need to find out why sea snakes are disappearing from known habitats, after it was discovered some seemingly identical sea snake populations are actually genetically distinct from each other and can’t simply repopulate if one group dies out.
Lead author, Dr Vimoksalehi Lukoschek from the ARC Centre of Excellence for Coral Reef Studies at James Cook University collected genetic samples from more than 550 sea snakes around Australia.
She said scientists were previously unaware of how genetically different sea snake populations on the Western Australian coast were from populations on reefs in the Timor Sea, Gulf of Carpentaria and the Great Barrier Reef.
“The previously unappreciated genetic distinctiveness in coastal Western Australia is critically important. It means that this region is home to genetic diversity not found elsewhere in Australia. If those populations die out, then that biodiversity and potential for adaptation is lost forever,” said Dr Lukoschek.
“Also, genetic differences of sea snakes between reefs around Australia mean that if a species disappears from a particular reef, they are unlikely to be replenished by dispersal of juveniles or adults from adjacent reefs.”
Dr Lukoschek said the sudden disappearance of sea snakes on the highly-protected Ashmore Reef in the Timor Sea remained unexplained, as were sea snake declines on protected reefs in New Caledonia and the southern Great Barrier Reef.
“We observed none of the obvious threats, such as changes in the habitat or fishing, so we are left with a list of other possible causes including disease, invasive species, pollution, seismic surveys or recruitment failure.”
Dr Lukoschek said targeted research on habitat and diet requirements, reproductive biology, disease susceptibility and the impacts of man-made processes, is crucial.
“It’s important we investigate sea snakes in particular, as traditional conservation actions that focus on tackling common causes of species decline, such as habitat loss, may not optimise the conservation of genetic divergence and diversity in these vulnerable populations,” she said.
Dr Lukoschek said conservation planners should incorporate genetic information, including identifying and prioritising evolutionary significant lineages, into their work.
“In the meantime, the findings suggest it is imperative to reduce stressors to coastal WA habitats including minimising the impacts of trawling and reducing the numerous anthropogenic impacts on the environment,” Dr Lukoschek concluded.
The paper “Congruent phylogeographic patterns in a young radiation of live-bearing marine snakes: Pleistocene vicariance and the conservation implications of cryptic genetic diversity” is published today in the journal Diversity and Distributions.
Images are available here. Please caption and credit as marked.
Dr Vimoksalehi Lukoschek
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New research into the impact of climate change has found that warming oceans will cause profound changes in the global distribution of marine biodiversity.
In a study published in the journal Nature Climate Change an international research team modelled the impacts of a changing climate on the distribution of almost 13 thousand marine species, more than twelve times as many species as previously studied.
The study found that a rapidly warming climate would cause many species to expand into new regions, which would impact on native species, while others with restricted ranges, particularly those around the tropics, are more likely to face extinction.
Professor John Pandolfi from the ARC Centre of Excellence for Coral Reef Studies at the University of Queensland says global patterns of species richness will change significantly, with considerable regional variability.
“This study was particularly useful because it not only gave us hope that species have the potential to track and follow changing climates but it also gave us cause for concern, particularly in the tropics, where strong biodiversity losses were predicted,” says Professor Pandolfi.
“This is especially worrying, and highly germane to Australia’s coral reefs, because complementary studies have shown high levels of extinction risk in tropical biotas, where localized human impacts as well as climate change have resulted in substantial degradation.”
To model the projected impact of climate change on marine biodiversity, the researchers used climate-velocity trajectories, a measurement which combines the rate and direction of movement of ocean temperature bands over time, together with information about thermal tolerance and habitat preference.
They say the analysis provides the simplest expectation for the future distribution of marine biodiversity, showing recurring spatial patterns of high rates of species invasions coupled with local extinctions.
Professor Elvira Poloczanska from CSIRO says, “This study shows how climate change will mix up biodiversity patterns in the ocean. Ecological communities which are currently distinct, will become more similar to each other in many regions by the end of the century”
Dr David Schoeman from the University of the Sunshine Coast says the model suggests that there is still time to act to prevent major climate-related extinctions outside of the topics.
“Results under a scenario in which we start actively mitigating climate change over the next few decades indicates substantially fewer extinctions than results from a business-as-usual scenario,” Dr Schoeman says.
“Possibly more worrying, though, is the imminent development of novel biotic assemblages. We have little idea of how these new combinations of species in ocean systems around the world will affect ecosystem services, like fisheries. We should be prioritising ecological research aimed specifically at addressing this question.”
Professor Pandolfi warns the resultant novel combinations of resident and migrant species will present unprecedented challenges for conservation planning.
“Above all, this study shows the broad geographic connections of the effects of climate change – conservation efforts need to be facilitated by cooperation among countries to have any real chance of combating the potentially severe biodiversity losses that a changing climate might impose.”
The paper, Climate velocity and the future of global redistribution of marine biodiversity by Jorge Garcia Molinos, Benjamin S. Halpern, David S. Schoeman, Christopher J. Brown, Wolfgang Kiessling, Pippa J. Moore, John M. Pandolfi, Elvira S. Poloczanska, Anthony J. Richardson and Michael T. Burrows is published in the journal Nature Climate Change http://dx.doi.org/10.1038/nclimate2769
Professor John Pandolfi, firstname.lastname@example.org, +61 (0) 400 982 301
Professor Elvira Poloczanska, Elvira.email@example.com, +61 (0) 428 741 328
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One of Australia’s leading coral reef ecologists fears that reef biodiversity may not provide the level of insurance for ecosystem survival that we once thought.
In an international study published today, Professor David Bellwood from the ARC Centre of Excellence for Coral Reef Studies (Coral CoE) says we need to identify and protect the most important species within reef ecosystems.
In coral reefs, just as in any modern-day society, there are vital jobs that keep the ecosystem safe and functioning.
Professor Bellwood says, in many cases, a single species of fish carries out a unique and essential role, making the ecosystem vulnerable to loss of that species.
Professor Bellwood and a team of international colleagues, led by Professor David Mouillot from the University of Montpellier, examined the ‘jobs’ of over six thousand coral reef fish species across 169 locations worldwide.
“What we often assume is that if we lose one species on a reef, there are many others that can step in and take over their job,” Professor Bellwood explains.
But he and his colleagues fear that’s not the case. They believe if a reef ecosystem were to lose a species that carried out a ‘specialist’ role, the impact could be profound.
“We could easily lose a type of fish that has no substitute, no replacement,” Professor Bellwood says.
“Unfortunately we have become complacent, we have assumed that biodiversity will buy us some time and give us some insurance, but that’s not necessarily the case.”
“It’s not about numbers of species,” adds Professor David Mouillot. “Biodiversity is important and desirable in an ecosystem, but it is not necessarily the key to being safe and secure”.
Professor Bellwood singles out the parrotfish, explaining that out of thousands of reef fish species, on the Great Barrier Reef only one parrotfish species regularly performs the task of scraping and cleaning inshore coral reefs.
“This parrotfish is a particularly valuable species,” he says, likening this finding to a large city with many inhabitants, but only one doctor.
“To protect ecosystems, we need to ensure that specific jobs are maintained,” Professor Bellwood says. “And that means we must protect the fish that do them.”
‘Functional over-redundancy and high functional vulnerability in global fish faunas on tropical reefs’ by David Mouillot, Sébastien Villéger, Valeriano Parravicini, Michel Kulbicki, Jesus Ernesto Arias-González, Mariana Bender, Pascale Chabanet, Sergio R. Floeter, Alan Friedlander, Laurent Vigliola, and David R. Bellwood appears in Proceedings of the National Academy of Sciences.
The paper is available on request.
Professor David Bellwood, Coral CoE: +44 (0) 7901 236 784, or
+61 (0) 407 175 007, firstname.lastname@example.org
(David Bellwood is travelling in the UK and is contactable on the above number between 1630 – 0600 AEST daily)
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Professor David Mouillot, University of Montpellier: +33 (0) 46 714 3719
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James Cook University Townsville
Queensland 4811 Australia
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