Large orb-webs adapted to maximise total biomass not rare, large prey

Screen Shot 2015-11-06 at 2.31.14 PMSpider orb-webs are the ultimate anti-ballistic devices, capable of dissipating the relatively massive kinetic energy of flying prey. Increased web size and prey stopping capacity have co-evolved in a number orb-web taxa, but the selective forces driving web size and performance increases are under debate. The rare, large prey hypothesis maintains that the energetic benefits of rare, very large prey are so much greater than the gains from smaller, more common prey that smaller prey are irrelevant for reproduction. Published in Nature Scientific Reports, Aaron Harmer leads work that integrates biophysical and ecological data and models to test a major prediction of the rare, large prey hypothesis, that selection should favour webs with increased stopping capacity and that large prey should comprise a significant proportion of prey stopped by a web. We find that larger webs indeed have a greater capacity to stop large prey. However, based on prey ecology, we also find that these large prey make up a tiny fraction of the total biomass (=energy) potentially captured. We conclude that large webs are adapted to stop more total biomass, and that the capacity to stop rare, but very large, prey is an incidental consequence of the longer radial silks that scale with web size.

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The life of fishes at the world’s smallest and isolated tropical island

foto_post_penedosReef fish communities have been intensely studied on large reef systems in the Caribbean Sea and Western Pacific regions, whereas communities on small and remote oceanic islands are still poorly understood. Logistical constraints imposed by remoteness limit fieldwork time and increase research costs. However, since environmental impacts on these previously pristine localities are increasing, there is an urgent need to learn how these isolated communities are structured. Isolated islands have been long known as natural laboratories for ecology and evolution because they are ecologically simpler than larger continental habitats. In a study published this week, Osmar Luiz, Diego Barneche and their colleagues take the ecological simplicity of islands to the extreme by investigating the factors affecting the reef fish community of the smallest remote tropical island in the world: the St. Peter and St. Paul’s Archipelago in the equatorial Atlantic Ocean, on the mid-Atlantic ridge.

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Food quality and reef fish diversification

The big disparities in species richness among evolutionary lineages have been fascinating and challenging scientists since Darwin’s time. Although geographical factors have been traditionally thought to promote speciation, the importance of ecological interactions as one of the drivers of diversification has been underscored. For example, is it possible to wonder that food quality might influence patterns of diversification in coral reefs?

new study conducted in Brazil and Australia shows that this is an important aspect to account for when looking at the evolution of coral reef fishes.

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Global change pushing reef fishes towards their energetic limits

_MG_7563 24x16A new study suggests that reef fish species may be hitting a ‘glass ceiling’ as water temperatures raise while reef predators receive substantial energy subsides from sources outside the reefs.

An international team of researchers led by scientists at Macquarie University offers a fresh perspective on threats to the health and biodiversity of reef ecosystems by synthesising energy expenditure data for individual fish with abundance and biomass data collected from reef fish communities all over the world.

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Daily grind shapes coral death

outer_reef_2bThe corals that build spectacular structures, like the Great Barrier Reef, can be killed in many different ways. Over the past few decades, the focus has been on extreme and rare events, such as tropical cyclones, thermal bleaching and outbreaks of the coral-eating crown-of-thorns starfish. However, a new study published in Ecology Letters raises important implications for policymakers to not ignore day-to-day reef death in environmental planning.

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