January 17, 2008, 9:19 PM CT

Predators do more than kill prey

The direct effect predators have on their prey is to kill them. The evolutionary changes that can result from this direct effect include prey that are younger at maturity and that produce more offspring.

But killing prey also has indirect effects rarely characterized or measured such as a decline in the number of surviving prey, resulting, in turn, in more food available to survivors.

In a new study characterizing the complex ecological interactions that shape how organisms evolve, UC Riverside biologists Matthew Walsh and David Reznick present a novel way of quantifying these indirect effects by showing that prey adapt to food availability as well as the presence of predators.

Our study can serve as a model for how humans alter ecosystems when they remove key predators like wolves and bears from land or tuna and billfish from seas, said Reznick, a professor of biology.

He and Walsh compared life history traits between Trinidadian fish communities impacted by the presence of predators. They settled on Trinidadian waterfalls as study sites because the waterfalls serve as barriers to the upstream distribution of predator and prey fish, thereby creating distinct ecological communities in similar habitats only a few hundred meters from each other like test-tubes in nature......... Posted by: Kelly      Read more         Source

January 17, 2008, 9:03 PM CT

Clams Convert Air Into Food

Only plants can take nitrogen gas from the air and use it to make the protein they need to grow. Or so biologists thought.

Now researchers at Ocean Genome Legacy in Ipswich, Mass., and their colleagues at Harvard Medical School have shown that animals, too, can convert air into food. The National Science Foundation (NSF) funded their research.

The animals are marine clams called shipworms. They burrow into and eat wood, causing more than a billion dollars in damage to ships and piers each year.

"Wood has very little nutritional value," said biologist Dan Distel, executive director of Ocean Genome Legacy. "It contains almost no protein. But these clams use bacterial symbionts living inside a special organ in their gills to convert dissolved air [which is about 80 percent nitrogen] into the protein they need".

The discovery reveals a new way for animals to feed and suggests that other animals in the sea and elsewhere may be able to survive with only air as a source of protein.

Understanding how these clams make use of this process is also helping scientists gain insights into how plants fix nitrogen, responsible for a large percentage of the protein made by plants and ultimately eaten by livestock and humans, said Distel and his colleagues Claude Lechene and Gregory McMahon of Harvard Medical School and Yvette Luyten of Ocean Genome Legacy......... Posted by: Kelly      Read more         Source

January 14, 2008, 5:11 PM CT

Starfish outbreak threatens corals

Outbreaks of the notorious crown of thorns starfish now threaten the coral triangle, the richest center of coral reef biodiversity on Earth, as per recent surveys by the Bronx Zoo-based Wildlife Conservation Society and ARC Centre of Excellence for Coral Reef Studies.

The starfish a predator that feeds on corals by spreading its stomach over them and using digestive enzymes to liquefy tissue were discovered in large numbers by the scientists in reefs in Halmahera, Indonesia, at the heart of the Coral Triangle, which lies between Indonesia, Malaysia, the Philippines, Papua New Guinea and the Solomon Islands. It is considered the genetic fountainhead for coral diversity found on Australias Great Barrier Reef, Ningaloo and other reefs in the region.

Researchers fear the outbreak is caused by poor water quality and could be an early warning of widespread reef decline.

Recent surveys of Halmahera by the Wildlife Conservation Society and ARC Centre of Excellence for Coral Reef Studies confirmed that while Halmaheras reefs are still 30-50 percent richer than nearby reefs, some areas were almost completely destroyed.

The main cause of damage to the corals was the Crown of Thorns Starfish, Dr. Andrew Baird of the ARC Centre of Excellence for Coral Reef Studies and James Cook University. We witnessed many active outbreaks of this coral predator. There was little to suggest that the reefs have been much affected by climate change as yet: the threats appear far more localized......... Posted by: Kelly      Read more         Source

January 14, 2008, 5:09 PM CT

Sea otter study reveals striking variability

Ecologists have long found that when food becomes scarce, animal populations exploit a wider range of food sources. So researchers studying southern sea otters at different sites in California's coastal waters were not surprised to find that the dietary diversity of the population is higher where food is limited. But this diversity was not reflected in the diets of individual sea otters, which instead showed dietary specialization in response to limited food.

The new findings by scientists at the University of California, Santa Cruz, will be published online in the Proceedings of the National Academy of Sciences the week of January 14. The study observed that all sea otters in an area with abundant food resources share the same dietary preferences. Where food is limited, however, a diverse array of feeding strategies emerges, with individual sea otters specializing on particular types of prey.

Tim Tinker, a UCSC research biologist and first author of the paper, said the study has both theoretical implications for the science of ecology and practical implications for wildlife management.

"The traditional way of viewing the relationships between predators and prey and how food webs are structured may be oversimplified," Tinker said. "When you look at the population as a whole, you may see a diversification of the diet in response to limited food resources. But when you look at individuals, you see dietary specialization"......... Posted by: Kelly      Read more         Source

January 3, 2008, 10:05 PM CT

Insect attack may have finished off dinosaurs

Asteroid impacts or massive volcanic flows might have occurred around the time dinosaurs became extinct, but a new book argues that the mightiest creatures the world has ever known may have been brought down by a tiny, much less dramatic force biting, disease-carrying insects.

An important contributor to the demise of the dinosaurs, experts say, could have been the rise and evolution of insects, especially the slow-but-overwhelming threat posed by new disease carriers. And the evidence for this emerging threat has been captured in almost lifelike-detail many types of insects preserved in amber that date to the time when dinosaurs disappeared.

There are serious problems with the sudden impact theories of dinosaur extinction, not the least of which is that dinosaurs declined and disappeared over a period of hundreds of thousands, or even millions of years, said George Poinar Jr., a courtesy professor of zoology at Oregon State University. That time frame is just not consistent with the effects of an asteroid impact. But competition with insects, emerging new diseases and the spread of flowering plants over very long periods of time is perfectly compatible with everything we know about dinosaur extinction.

This concept is outlined in detail in What Bugged the Dinosaurs? Insects, Disease and Death in the Cretaceous, a book by George and Roberta Poinar, just published by Princeton University Press......... Posted by: Kelly      Read more         Source

January 3, 2008, 9:27 PM CT

Smell-wars between butterflies and ants

Among humans, making yourself smell more alluring than you really are is a fairly harmless, socially accepted habit that maintains a complete perfume industry. However, it is a matter of life and death for caterpillars of large blue butterflies that dupe ant workers into believing them to be one of the ants own larvae. In a publication in the journal Science this week , scientists from the Centre for Social Evolution (CSE) at the University of Copenhagen show that caterpillar deception is also a matter of smell, and that there is an ongoing co-evolutionary arms race in smell similarity between cheaters and their victims.

Most people are familiar with animal confidence tricksters such as cuckoos, which grow up at the expense of 4-5 chicks of hapless songbirds. Less well known, but at least as spectacular, are the large blue butterflies of the genus Maculinea, whose larvae are adopted by ant colonies and deceive the ants into feeding them while letting their own brood starve. Jutland, and the island Ls in particular, are among the last European strongholds of one of these species, the Alcon blue, which has enabled scientists from the CSE to study these spectacular butterflies in great detail.

David Nash, Jacobus Boomsma and his colleagues show that superb chemical mimicry manipulates the ants into neglecting their own brood to care almost exclusively for their caterpillar parasites, but also that the ant hosts can evolve resistance against this exploitation by changing how they smell. However, this only works when the host ants that live close to the initial foodplant of the caterpillars, the rare marsh gentian Gentiana pneumonanthe, do not interbreed with ants from neighbouring sites where the gentian does not occur. In the sites without the foodplant, ant colonies are never parasitized, so ants do not evolve resistance. Any resistance that has evolved in areas with butterflies is not effectively passed on to future generations because it is diluted by the flow of non-resistant genes from the uninfected areas......... Posted by: Kelly      Read more         Source

December 27, 2007, 9:18 AM CT

Photo-monitoring whale sharks

Up to 20 meters long and weighing as much as 20 tons, its enormous size gives the whale shark (Rhincodon typus) its name. Known as the gentle giant for its non-predatory behavior, this fish, with its broad, flattened head and minute teeth, eats tiny zooplankton, sieving them through a fine mesh of gill-rakers. Listed as a rare species, relatively little is known about whale sharks, which live in tropical and warm seas, including the western Atlantic and southern Pacific. However, a new study combines computer-assisted photographic identification with ecotourism to study the rare species and suggests whale shark populations in Ningaloo, Western Australia are healthy. The study appears in the Ecological Society of Americas recent issue of Ecological Applications.

West Australian marine scientist Brad Norman (ECOCEAN/Murdoch University) began the study in 1995. Photographs were taken while swimming alongside each whale shark and photographing or video-taping the white lines and spots along the flanks of the animal. Norman teamed up with U.S. computer programmer Jason Holmberg (ECOCEAN, Portland, Oregon) and astronomer Zaven Arzoumanian (USRA/NASA, Greenbelt, Maryland) who adapted software originally used with the Hubble space telescope. The pattern-recognition software developed by Holmberg and Arzoumanian allowed the group to positively identify individual whale sharks. Like a human fingerprint, the speckles and stripes pattern on the skins of whale sharks are thought to beunique to each individual......... Posted by: Kelly      Read more         Source

December 20, 2007, 9:53 PM CT

Study says 2000 tigers possible in Thailand

Thailands Western Forest Complex a 6,900 square mile (18,000 square kilometers) network of parks and wildlife reserves can potentially support some 2,000 tigers, making it one of the worlds strongholds for these emblematic big cats, as per a new study by Thailands Department of National Park, Wildlife, and Plant Conservation and the New York-based Wildlife Conservation Society. The study, which appears in latest issue of the journal Oryx, says that to make these numbers a reality, better enforcement to safeguard both tigers and their prey from poachers is critical.

As per the study, the entire Western Forest Complex currently supports an estimated 720 tigers. These tiger densities were lower than those reported by Wildlife Conservation Society researchers from some protected areas in India with similar habitat, but better enforcement. For example, tiger densities of as a number of as 12 tigers per 100 square kilometers were measured in Indias Nagarahole, Bandipur and Kanha forests, as opposed to four tigers per 100 square kilometers in Thailands Huai Kha Khaeng Wildlife Sanctuary.

The authors of the study conducted intensive surveys of tigers in Huai Kha Khaeng, using camera traps to estimate a population size of 113 individual animals living in the 1,084 square-mile (2,810 square kilometer) protected area......... Posted by: Kelly      Read more         Source

December 20, 2007, 5:30 AM CT

Parents show bias in sibling rivalry

Most parents would hotly deny favouring one child over another but new research suggests they may have little choice in the matter.

Biologists studying a unique species of beetle that raises and cares for its young have observed that parents instinctively favour the oldest offspring.

The University of Manchester research published in Ecology this month supports the findings of studies carried out on human families but is significant in that it suggests a wholly natural tendency towards older siblings.

The burying beetle Nicrophorus vespilloides has a similar family structure to that of a human family unit in that there are two parents, many offspring and interactions between parents and their young, said Dr Per Smiseth, who led the research in the Universitys Faculty of Life Sciences.

Of course human families are more complex and parent-child relationships are much more sophisticated. However, studying this beetle can help us understand the basic biological principles of how family relationships work.

Our study looked at how the parent beetles mediate competition between different aged offspring in comparison to what happens when the young were left to fend for themselves and indicates that parental decisions are important in determining the outcome of competition between offspring......... Posted by: Kelly      Read more         Source

December 18, 2007, 9:49 PM CT

Ant invaders eat the natives

The Argentine ant, Linepithema humile, is one of the most successful invasive species in the world, having colonized parts of five continents in addition to its native range in South America. A new study sheds light on the secrets of its success.

The findings, from scientists at the University of Illinois and the University of California at San Diego, appear this week in the Proceedings of the National Academy of Sciences.

The Argentine ant is tiny, aggressive and adaptable, traits that have helped it in its transit around the world. Once seen only in South America, the ant is now found in parts of Asia, Australia, Europe, North America and South Africa. It most likely made its way to these destinations on ships carrying soil or agricultural products.

Under the right conditions, the Argentine ant marches through a new territory, wiping out - by eating and out-competing - most of the native ants and a number of other insects. In the process it radically alters the ecology of its new home.

The Argentine ant thrives in a warm climate with abundant water, and is often found on agricultural lands or near cities. But it also invades natural areas, said U. of I. entomology professor Andrew Suarez, principal investigator on the new study. The ant is highly social, and sometimes forms immense "super-colonies" made up of millions workers spread over vast territories. In prior research, Suarez identified a super-colony in California that stretched from San Diego to San Francisco......... Posted by: Kelly      Read more         Source