Yellow or black, large or small? Ant color and body size respond strongly to environment

Date: September 8, 2016

Source: University of Liverpool

A University of Liverpool study of ants across three continents has revealed that their colour and size is strongly influenced by their environment, and that the dominant colour and average body size can change from year to year as temperatures vary. This finding has implications for how ant communities will cope with rising global temperatures.

Ants are ectotherms and so rely on the temperature of their surrounding environment to control their metabolic activity. Previous studies from individual locations or single species have found that larger bodied ectotherms with dark colouration do well in cold places. Large bodies retain heat whilst dark colours help individuals to gain heat quicker than their paler counterparts do. Combined, these two traits are highly beneficial as they allow ectothermic individuals to forage and remain active for longer even under cool conditions.

Researchers at the University's School of Environmental Sciences wanted to test whether these ideas of ectotherm thermoregulation held across species and at large geographic scales. They collected and analysed information on the abundance, body size and colour of ants on 14 different mountains from locations in South Africa, South America and Australia. Some of the sites were sampled repeatedly for up to seven years. This diversity of elevations and latitudes provided a huge range of external ambient temperatures (from 0.5 to 35°C).

They found that the colder the external temperature is, the larger and darker ants were, and vice versa. Consequently, communities of ants in sites closer to the South Pole or near the tops of mountains, where it was colder, would tend to be dominated by dark and large bodied ants. In warmer places the ant species were smaller and lighter in colour.

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On land and at sea, large animals are in 'double jeopardy'

Date: June 9, 2016

Source: Cell Press

Large animals hunted for their parts -- such as elephant ivory and shark fins--are in double jeopardy of extinction due to their large body size and high value, according to a new analysis reported in the Cell Press journal Current Biologyon June 9. The study reveals underappreciated risk to marine species similar to that of iconic terrestrial species, but elevated by key differences in the sea.

"We typically assume that if a species is reduced to low numbers, individuals will be hard to find, hunters will stop hunting, and populations will be given a chance to recover," says Loren McClenachan of Colby College in Waterville, Maine. "But the extreme values of these species mean that without significant conservation intervention, they will be hunted to extinction."

In the new study, McClenachan, along with Andrew Cooper and Nicholas Dulvy of Simon Fraser University in Canada, identified a taxonomically diverse group of more than 100 large marine and terrestrial species that are targeted for international luxury markets. They estimated the value of these species across three points of sale and explored the relationships among extinction risk, value, and body size. They also quantified the effects of two mitigating factors: poaching fines and geographic range size.

The analysis showed a threshold above which economic value is the key driver of extinction risk. Although lower-value species are influenced primarily by their biology, the most valuable species are at high risk of extinction no matter their size. Once mean product values are greater than US$12,557 per kilogram, body size no longer drives risk, the report shows.

The researchers also uncovered important differences between marine and terrestrial species that point to elevated risk in the sea: although marine products are generally less valuable on a per kilogram basis, individual animals are still just as valuable as the most valuable terrestrial species. An individual whale shark, for example, is about as valuable as the most valuable terrestrial species: rhinoceroses and tigers.

"Hunters don't kill kilograms, they kill individuals, so we need to pay attention to these high values of individual animals," McClenachan says.

The risk to marine species isn't reduced for species with larger ranges as it is on land, either.

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Warming Temperatures Cause Aquatic Animals to Shrink the Most

ScienceDaily (Nov. 5, 2012) — Warmer temperatures cause greater reduction in the adult sizes of aquatic animals than in land-dwellers in a new study by scientists from Queen Mary, University of London and the University of Liverpool.

The research published Nov 5 in Proceedings of the National Academy of Sciences (PNAS) shows that the body size of marine and freshwater species are affected disproportionately by warmer temperatures. This could have implications for aquatic food webs and the production of food by aquaculture.

The researchers compared the extent to which the adult size of 169 terrestrial, freshwater, and marine species responded to different non-harmful temperatures, in the largest study of its kind.

Summarising the results, co-author Dr Andrew Hirst from Queen Mary's School of Biological and Chemical Sciences, said:

"Aquatic animals shrink 10 times more than land-dwellers in species the size of large insects or small fish. While animals in water decrease in size by 5 percent for every degree Celsius of warming, similarly sized species on land shrink, on average, by just half a percent."

Continued:  http://www.sciencedaily.com/releases/2012/11/121105151334.htm

Extinction Risk Factors for New Zealand Birds Today Differ from Those of the Past

ScienceDaily (Aug. 2, 2012) — What makes some species more prone to extinction? A new study of nearly 300 species of New Zealand birds -- from pre-human times to the present -- reveals that the keys to survival today differ from those of the past.

The results are important in light of the growing number of studies that try to predict which species could be lost in the future based on what kinds of species are considered most threatened today, said lead author Lindell Bromham of Australian National University.

In the roughly 700 years since humans arrived in the remote islands that make up New Zealand, more than one out of four of New Zealand's native bird species have been wiped out.

Gone are birds such as the massive Haast's eagle, which weighed up to 33 pounds (15kg), and the giant moa, a flightless bird that stood up to ten feet (3m) tall.

Many species were hunted to extinction. Others were eaten by the animals humans brought with them -- such as cats, rats and weasels -- or pushed off their land as humans cleared and burned forests to make way for farms and pastures.

In a new study, a team of researchers examined whether biological traits such as body size might help scientists predict which species were likely to perish, and whether those risk factors held up over time.

Continued:  http://www.sciencedaily.com/releases/2012/08/120802183952.htm