The More the Merrier

The relationship between the number of species in an ecological community and the functional aspects of the ecosystem is usually studied experimentally by observing the effects of random changes in diversity. However, a study of rocky intertidal pools reveals that the nonrandom variation in species diversity that is characteristic of natural habitats yields better predictions of functional effects than experiments in which the species composition is altered randomly. Bracken et al. quantified the effects of both kinds of variation in seaweed diversity on nutrient dynamics (nitrogen uptake) in a set of tide pools in which the number of species increased as disturbance (caused by heavy surf) decreased. The effects of natural realistic variation were compared with the effects of artificial diversity gradients established by random groupings of species. Increased diversity in the “real-world” pools was associated with higher rates of nutrient acquisition by the plants, whereas the artificial communities showed no relationship. These results present new challenges for experimental ecologists studying the consequences of biodiversity loss in ecosystems.

*.* Source of Information : 15th February 2008 Science

Third Party Parasitism

For more than 50 million years, Agaonidae wasps have laid their eggs in the ovules of the enclosed flowers, or syconia, of fig trees. The grubs stimulate the formation of a small gall and feed on the plant, tissue. The payback for the loss of reproductive power to the fig tree occurs when the young wasps emerge and carry their host's pollen to other trees. Fortunately for the trees, wasps don, Lay eggs in every ovule in a syconium, even though in evolutionary terms this might seem a good strategy for the wasp; rather than being deterred by the tree itself, the fig wasps are in fact preyed on by another wasp. The parasitoid's ovipositor is just long enough to penetrate the wall of the fig and reaches only the outer most ovules. Dunn et al. show that thanks to the packing architecture of the ovules within the syconium, the fig wasps predominantly use inner ovules that are out of range of the parasitoid, allowing the other ovules to mature into fig seeds and thereby stabilizing this mutualism.

*.* Source of Information : 4th April 2008 Science