Timid jumping spider uses ant as bodyguard
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March 11, 2014 Source: Springer Science+Business Media Summary: Ants are the unlikely guardians of jumping spiders in their battle against aggressive spitting spiders. A timid jumping spider uses the scent of ants as a secret weapon to save itself from becoming the somewhat soggy prey of the predatory spitting spider. The downside to this plan is that jumping spiders are also a favorite snack of its very own saviors. To overcome this additional hazard, the spider has made yet another plan in the form of an ant-proof nest.Ants are the unlikely guardians of jumping spiders in their battle against aggressive spitting spiders. A timid jumping spider uses the scent of ants as a secret weapon to save itself from becoming the somewhat soggy prey of the predatory spitting spider. The downside to this plan is that jumping spiders are also a favorite snack of its very own saviors. To overcome this additional hazard, the spider has made yet another plan in the form of an ant-proof nest, writes Ximena Nelson of the University of Canterbury in New Zealand and Robert Jackson of the University of Canterbury and the International Centre of Insect Physiology and Ecology in Kenya, in Springer's journal Behavioral Ecology and Sociobiology. Associations in which a more vulnerable species gains protection by seeking out the company of a pugnacious protector species capable of deterring predators are more well-known among birds than among arachnids. Nelson and Jackson therefore carried out experimental work at the International Rice Research Institute in the Philippines to look at the dynamics between a type of jumping spider (Phintella piatensis), the territorial weaver ant (Oecophylla smaragdina) and a web-building predatory spitting spider (Scytodes sp). The spitting spider can immobilize its prey by spitting on it from a distance. In the Philippines, it lives on the same large waxy leaves as the jumping spider. It normally spins its web right over the nest of the jumping spider, to make hunting just a little bit easier. However, the researchers found that a spitting spider does not come near a jumping spider when the latter positions its own nest near that of weaver ants. This is because the spitting spider is repelled by the specific airborne olfactory compounds that these ants release. The researchers found that jumping spiders choose nesting sites based on whether they can see active living ants, if they detect ant odor or can see mounts made from dead weaver ants. However, it's not yet plain sailing for the jumping spider, as it is also a favorite snack of its savior, the weaver ant. Therefore jumping spiders build dense ant-proof nests of an unusually tough and dense weave that are difficult for the insects to tear open. The nest's hinged flaps of silk at each end function as swinging doors. The spider quickly raises these when it enters or leaves the nest, before any ants can follow, too. "Nesting associations with territorial ants whereby the ant does not receive any benefit may be more common among arthropods than is currently appreciated," concludes Nelson. "We expect that a closer look at ant-other arthropod relationships will yield numerous examples similar to ours and provide a better understanding of the complexities of microhabitat choice and its ecological ramifications." Story Source: The above story is based on materials provided by Springer Science+Business Media. Note: Materials may be edited for content and length. |
Light pollution impairs rainforest regeneration: Seed-dispersing bats avoid feeding in light polluted areas
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March 10, 2014 Source: Forschungsverbund Berlin e.V. (FVB) Summary: Increasing light pollution in tropical habitats could be hampering regeneration of rainforests because of its impact on nocturnal seed-dispersers. These new findings show that seed-dispersing bats avoid feeding in light-polluted areas.Increasing light pollution in tropical habitats could be hampering regeneration of rainforests because of its impact on nocturnal seed-dispersers.These new findings were reported by scientists from the German Leibniz Institute for Zoo and Wildlife Research Berlin (IZW). The study -- published in the British Ecological Society's Journal of Applied Ecology - is the first to show that seed-dispersing bats avoid feeding in light-polluted areas. Working with Sowell's short-tailed bats (Carollia sowelli), Daniel Lewanzik from the IZW gave the bats a simple choice. He divided a flight cage into two compartments. One was naturally dark and the other was illuminated by a sodium street lamp, the most common form of street lighting in the world. Inside both parts of the cage the bats were offered their favourite fruits to harvest: pepper plants, nightshade and figs. The results revealed that bats flew into the dark compartment twice as often as the compartment lit by a street lamp. The bats also harvested fruits almost twice as often in the dark compartment. In a second experiment Lewanzik illuminated pepper plants growing in the wild with a street light and measured the percentage of ripe fruit which bats harvested from plants in a dark location and from lit plants. While bats harvested 100 per cent of the marked, ripe fruit from the plants in the dark, only 78 per cent were taken from the lit plants. Although insect-eating bats have been shown to avoid foraging in light-polluted areas, this is the first study to show that fruit-eating bats also avoid lit areas. This has important implications for forest regeneration in the tropics. Bats play a key role in pollinating plants and spreading their seeds, especially the seeds of species that are first to recolonise cleared land. "In tropical habitats bat-mediated seed dispersal is necessary for the rapid succession of deforested land because few other animals than bats disperse seeds into open habitats," says Daniel Lewanzik, doctoral candidate at the IZW and first author of the study. Under naturally dark conditions, bats produce a copious 'seed rain' when defecating seeds while flying. By reducing foraging of fruit-eating bats in lit areas, light pollution is likely to reduce seed rain, he commented. In many tropical countries, light pollution is increasing rapidly as economies and human populations grow. Natural succession of forests could therefore suffer as tropical habitats become increasingly illuminated. "The impact of light pollution could be reduced by changes in lighting design and by setting up dark refuges connected by dark corridors for light-sensitive species like bats," Lewanzik says. Background information: * Sowell's short-tailed bat (Carollia sowelli) belongs to the large family of Phyllostomidae or leaf-nosed bats. The characteristic leaf like structure protruding upwards from their nose is believed to be involved in focusing the bats' ultrasonic biosonar beam more precisely. Their relatively broad wings allow them to fly slowly and to manoeuvre elegantly within the dense forest. This is necessary since they mainly feed on fruit of pepper plants from the genus Piper that grow in the understory. These fruit are usually long and thin spikes that bats harvest on the wing and then eat it as humans eat corn on the cob. Story Source: The above story is based on materials provided by Forschungsverbund Berlin e.V. (FVB). Note: Materials may be edited for content and length. |
Predation on invertebrates by woodland salamanders increases carbon capture
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March 10, 2014 Source: USDA Forest Service - Pacific Southwest Research Station Summary: Woodland salamanders perform a vital ecological service in American forests by helping to mitigate the impacts of global warming. Woodland salamander predation on invertebrates indirectly affects the amount of leaf litter retained for soil-building where nutrients and carbon are captured at the litter-soil interface.Woodland salamanders perform a vital ecological service in American forests by helping to mitigate the impacts of global warming. Global warming occurs when greenhouse gases like carbon dioxide are released into the atmosphere. Woodland salamanders facilitate the capture of this carbon before it is released by feeding on invertebrates (beetles, earthworms, snails, ants, etc.) that would otherwise release carbon through consumption of fallen leaves and other forest debris. Woodland salamanders are the most common vertebrate species in American forests; consequently, these small, seldom-seen animals may play a significant role in regulating the capture of carbon from leaf litter in forest soils. Dr. Hartwell Welsh, Jr., research wildlife biologist at the U.S. Forest Service's Pacific Southwest Research Station (PSW), helped conduct a study in Northwestern Calif. that examined how woodland salamander predation on invertebrates indirectly affects the amount of leaf litter retained for soil-building where nutrients and carbon are captured at the litter-soil interface. The objective of the study was to investigate the role of salamanders in regulating invertebrate abundances and how that influenced leaf litter retention. The study included soil moisture as a covariate, and field enclosures on the forest floor to quantify the effects of woodland salamanders. The study was conducted over two rainy seasons, and found that woodland salamander predation on invertebrates suppressed some populations of invertebrates and released others, with the overall result of increased litter retention and carbon capture in the soil. However, the strength of the effect was modulated by the timing and amount of precipitation. This research is unique and important, and will increase public understanding of how the impacts of global warming may be countered and raise awareness of the ecological role woodland salamanders play in the forest carbon cycle. "The renowned evolutionary biologist E.O. Wilson once said it is the little things that run the world," Dr. Welsh said. "While Wilson probably had in mind invertebrates, I think he would agree that our research on the influence of one of the primary predators on invertebrates, and their influence on the forest carbon cycle, is a good example of what he was talking about." Further information: http://www.treesearch.fs.fed.us/pubs/45487 Story Source: The above story is based on materials provided by USDA Forest Service - Pacific Southwest Research Station. Note: Materials may be edited for content and length. |
Impersonating poisonous prey: Evolution of interspecific communication
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March 10, 2014 Source: Michigan State University Summary: Imitation is the most sincere form of flattery -- especially in the predator/prey/poison cycle. In nature, bright colors are basically neon signs that scream, 'Don't eat me!' But how did prey evolve these characteristics? When did predators translate the meaning?Imitation is the most sincere form of flattery -- especially in the predator/prey/poison cycle. In nature, bright colors are basically neon signs that scream, "Don't eat me!" But how did prey evolve these characteristics? When did predators translate the meaning? In the current issue of the journal PLOS ONE, researchers at Michigan State University reveal that these color-coded communiqués evolve over time through gradual steps. Equally interesting, the scientists show how drab-colored, oft-eaten prey adopt garish colors to live long and prosper, even though they aren't poisonous, said Kenna Lehmann, MSU doctoral student of zoology. "In some cases, nonpoisonous prey gave up their protection of camouflage and acquired bright colors," said Lehmann, who conducted the research through MSU's BEACON Center for the Study of Evolution in Action. "How did these imitators get past that tricky middle ground, where they can be easily seen, but they don't quite resemble colorful toxic prey? And why take the risk?" They take the risk because the evolutionary benefit of mimicry works. A nontoxic imposter benefits from giving off a poisonous persona, even when the signals are not even close. Predators, engrained to avoid truly toxic prey, react to the impersonations and avoid eating the imposters. An example of truly toxic animals and their imitators are coral snakes and king snakes. While coral snakes are poisonous, king snakes are not. Even though king snakes are considered imperfect mimics, they are close enough that predators don't bother them. Why don't all prey have these characteristics, and why don't the imitators evolve to develop poison instead? Leaving the safety of the cryptic, camouflage peak to go through the exposed adaptive valley over many generations is a dangerous journey, Lehmann said. "To take the risk of traversing the dangerous middle ground -- where they don't look enough like toxic prey -- is too great in many cases," she said. "Toxins can be costly to produce. If prey gain protection by colors alone, then it doesn't make evolutionary sense to expend additional energy developing the poison." The results suggest that these communicative systems can evolve through gradual steps instead of an unlikely large single step. This gives insight into how complex signals, both sent and received, may have evolved through seemingly disadvantageous steps. Rather than conduct experiments of voracious predators chasing and eating, or completely avoiding, prey, the scientists used evolving populations of digital organisms in a virtual world called Avida. Avida is a software environment developed at MSU in which specialized computer programs compete and reproduce. Because mutations happen when Avidians copy themselves, which lead to differences in reproductive rates, these digital organisms evolve, just like living things. Additional MSU scientists who contributed to the study include: Brian Goldman, Ian Dworkin, David Bryson and Aaron Wagner. This research was funded by the National Science Foundation. Story Source: The above story is based on materials provided by Michigan State University. Note: Materials may be edited for content and length. |