The team compared the thermal limits of over 300 species of lizards, frogs, insects, spiders, bivalves, crustaceans, and fish from across the world, spanning latitudes from the Antarctic to Alaska. This is the most comprehensive analysis of the geographic distribution of thermal limits ever compiled. The study was published in the latest issue of the Proceedings of the Royal Society of London, series B.

“We were surprised at how little heat tolerance changed in American land animals – ranging from the equator up to Canadian latitudes,” said Jennifer Sunday. “These patterns are so striking that it suggests a common mechanism underlies uniform heat tolerance in land animals.”

The team’s finding goes against the received wisdom that animals living in cooler climates should be less heat tolerant. The key question is why even animals living in cool climates have the ability to survive tropical temperatures.

The team suggest two possible explanations. Either heat tolerance is an evolutionary legacy and there is little cost to retaining this trait. Alternatively, there is adaptive value in retaining the ability to tolerate even the rarest heat shocks. Either explanation will have important consequences for how land animals will respond to global climate warming.

By contrast, the same analysis revealed that ocean-dwelling animals have heat tolerances that decline steadily towards the poles. In other words, ocean animals follow the expectation but land animals do not. This surprising contrast between land and ocean animals may be a key into understanding why land animals in Canada can tolerate the same high temperatures as those in Costa Rica.

“The clear difference between land and ocean animals is an important clue,” said Amanda Bates of Deakin University, Australia. “Heat tolerance in fish declines as you move away from the equator, but heat tolerance in lizards does not. This key difference between ocean and land-dwelling organisms has never been noticed before.”

“Before we can predict how species will be affected climate change, we need to first understand how species distributions are limited by our current climate. While the poles are warming faster, the narrow thermal tolerance of tropical species means they have a narrow thermal safety margin (and are already close to their thermal limit). This finding opens the door to the possibility that high-latitude species may have heat tolerance over-and-above what they need to currently survive,” said Nicholas Dulvy of Simon Fraser University.

Sunday, J. M., Bates, A. E. and Dulvy, N. K. (2011) Global analysis of thermal tolerance and latitude in ectotherms, Proceedings of the Royal Society B: Biological Sciences, 278, 1823-1830.

Evaluation by Robert Colwell for Faculty of 1000:

Interview on Radio Ecoshock with Jenn Sunday andd Nick Dulvy

Contact:
Jennifer Sunday, email: sunday@sfu.ca

In a paper published recently in the journal PLoS ONE, Sean Anderson (a recent addition to the Dulvy lab) along with co-authors Joanna Mills Flemming, Reg Watson, and Heike Lotze explored global trends in invertebrate fisheries over the past 50 years using a database of fisheries catches maintained by the University of British Columbia’s Sea Around Us Project.

Marine invertebrates are ocean dwelling animals that lack a backbone. They include shrimps, oysters, squids, and sea urchins, for example. While global catches from fish fisheries peaked in the 1980s and have declined or remained stable since, invertebrate fisheries have continued to expand.

The authors found that fishing for invertebrates has rapidly expanded globally in three ways: (1) more countries are fishing invertebrates, (2) countries are fishing invertebrates in greater volume, and (3) countries are fishing for more types of invertebrates.

However, the underlying trends in many individual invertebrate fisheries are less optimistic. About 1/3 are now over-exploited, collapsed, or closed and 71% of the taxa and over half the catches are harvested with habitat destructive gear such as benthic trawls and dredges. Further, many invertebrate fisheries are developing more rapidly and further away from their main markets.

In addition to the predator-prey roles that both fish and invertebrate species play in the ocean, invertebrates tend to have diverse ecosystem functions such as maintaining water quality, regenerating nutrients, and preventing algal overgrowth. The authors estimate that bivalve harvesting alone removes about 11 million Olympic-sized swimming pools of filtering capacity every day.

There are many examples of successfully managed invertebrate fisheries that provide an opportunity to inform the management of other fisheries. Strategies such as co-management and assigning property rights combined with reductions in fishing effort have successfully restored abundance and profitability for many invertebrate fisheries.

The authors hope that by increasing awareness of the ecological and economic importance of invertebrate fisheries their work will encourage proper scientific assessment and management to ensure healthy ocean populations, ecosystems, and ultimately, human well-being.

Original article: Anderson, S.C., J. Mills Flemming, R. Watson, H.K. Lotze. 2011. doi:10.1371/journal.pone.0014735″ target=”_blank”>Rapid global expansion of invertebrate fisheries: trends, drivers, and ecosystem effects. PLoS ONE. doi:10.1371/journal.pone.0014735

An insight comes from fieldwork by Kirsten Abernethy, one of the first Dulvy lab graduates with a newly-minted PhD from University of East Anglia, UK. She was working in southwest England figuring out how fishermen decide where to fish when the price of fuel rocketed in early 2008. UK Fuel prices doubled between early 2007 and mid 2008, whereas fish prices remained relatively stable throughout as a result of the price-setting power of seafood buyers. Thus, fishers were unable to pass on increasing fuel costs resulting in a significant loss of income, reduced job security and difficulties in recruiting crew. The rapid change in the economic conditions in 2008 intensified pressure on fishing businesses and highlighted the susceptibility of vulnerable fishing-dependent communities to financial shocks. The primary concern was that job losses of crew and shore workers in the community would reduce the industry to a level where key parts of the fishing infrastructure such as the fish market, fish merchants and processors may disperse. Such losses may generate irreversible effects for the viability for the fishing industry, causing erosion of the community as previously observed in other parts of the UK. The fuel price shock provided an insight into which sectors were better able to adapt to uncertainty and how skippers altered their behaviour in response. Fishing vessels which used static fishing gear, were well-managed, and had recent investment resulting in greater fuel efficiency, were more able to cope and adapt with increasing fuel costs.

Fishing behaviour altered with most skippers fishing closer to port, and reducing fishing to times where fishing was likely to be efficient and profitable at the cost of reduced catches. Exploratory fishing reduced and skippers ceased experimentation with fishing gear with lower environmental impacts. The impacts of this fuel price volatility foreshadow a likely future impact of rising fuel prices attributable to climate change adaptation and mitigation and forecasts of rising global oil prices.

Kirsten summarised her findings in a recently published paper:
Abernethy, K. E., Trebilcock, P., Kebede, B., Allison, E. H. and Dulvy, N. K. (2010) Fuelling the decline of UK fishing communities?, ICES Journal of Marine Science, 67, 1076–1085.

Abernethy_2010

How do they all get along without one species taking over?

Why are there so many species and how do they all coexist? Understanding how species coexist is fundamental to understanding the generation and maintenance of the richness of life on Earth. These intertwined questions have challenged ecologists and natural historians for at least half a century. These questions are not just intertwined they are paradoxical. Multiple species dependent on a single resource cannot co-occur; in theory if there is any differenfce at all in species traits and their niches then the competitively-superior species should eventually dominate and drive the other inferior competitor to extinction. This is the “paradox of the plankton: first proposed by one of the fathers of moden ecology – G. Evelyn Hutchinson in 1961.

When is comes to understanding the origin and maintenance of the  diversity of life on Earth there are two distinct schools of thought. Species coexist because they are different (niche theory) or species coexist because they are identical (neutral theory). The very existence of differences among species in traits and performance has been taken as irrefutable evidence that niche partitioning enables species to get along (coexistence). However, recent work has identified a class of models on the other extreme, called neutral models, because all species are indentical. Neu models generate and explain important biological patterns, such as the species richness-abundance distribution, using as few as three parameters: the size of the wider metacommunity, dispersal and speciation rates.  Like everything else in science, the truth probably lies between these extremes and the most recent theoretical models allow for combined neutral and niche dynamics. The second truth of science is that this model is not new, but infact is one of the oldest and most fundamental models used in ecology – the Lotka-Volterra competition model. This model was rediscovered and in this context has been dubbed the emergent neutrality model because while it is fundamentally niche-based in formulation, relying on interspecific compatition coefficients, neutral patterns emanate from model simulations involving large numbers of competitors.

Remi Vergnon (University of Sheffield, UK) identified 4 theories along the niche-neutral spectrum of possible mechanisms and identified the key predictions from these. Remi showed that the distribution of marine phytoplankton species is non-random across a body size niche axis. Indeed, there are distinct aggregations of species of similar body mass among the permanent community members of the community. The only species that do not occur in these aggregations are the transient species that are unlikely to interact strongly with permanent members. These empirical observations are consistent only with a model that combines both niche and neutral dynamics, and to the best of our knowledge constitutes the first empirical evidence for the role of emergent neutrality in explaining species coexistence in nature. The team have recently published their findings in Ecology Letters.

Remi is funded by Euroceans and supervised by Rob Freckleton (U. Sheffield) Yunne Shin (IRD, Sete, France) and Nicholas Dulvy (Simon Fraser University, Canada). The work could not have been conducted without the generous support of Roger Harris and the Plymouth Marine Lab, Western Channel Observatory who collect and maintain the L4 zooplankton time-series.

Vergnon, R., Dulvy, N.K. & Freckleton, R.P. (2009) Niches versus neutrality: uncovering the drivers of diversity in a species-rich community. Ecology Letters, 12, 1079-1090.

It was already known that coral cover in the Caribbean was in decline, but this is the first large scale study showing exactly what this means for the architecture of the region’s reefs.

Published online on Wednesday June 10 by the peer-reviewed journal ‘Proceedings of the Royal Society B’, the researchers found that the vast majority of reefs have lost their complex structure and become significantly flatter and more uniform. The most complex reefs have been virtually wiped out.

The researchers, working with colleagues at Simon Fraser University in Canada, analysed changes in the structure of reefs using 500 surveys across 200 reefs conducted between 1969 and 2008.  They found that 75 per cent of the reefs are now largely flat, compared with 20 per cent in the 1970s. Contact me <nick_dulvy@sfu.ca> for a copy of the paper.

There have been two major periods of reef flattening. The first occurred when a widespread disease killed about 90 per cent of the Elkhorn and Staghorn corals in the late 1970s. The second period has been underway more recently and is thought to have been caused by an increase in the intensity and frequency of coral bleaching events, as a consequence of human-induced climate change increasing sea surface temperatures.