ASTRONOMY: The Distance to the Large Magellanic Cloud

The Large Magellanic Cloud (LMC), a satellite of the Milky Way, is an important yardstick by which most intergalactic distances are measured. But as Cole explains in this Perspective, how far away the LMC is remains a matter of dispute, with far reaching implications in cosmology. But observations of Cepheids and of eclipsing binaries, two types of stars that allow absolute luminosity and thus absolute distances to be determined, are promising to resolve this important issue in the not too distant future.     

Marine protected areas export larvae of infauna, but not of bioengineering mussels to adjacent areas

Populations of organisms that create habitat can often be fragmented throughout landscapes by anthropogenic disturbances such as harvesting and loss or change to the identity of such bioengineers may lead to large changes in biodiversity. Using the fauna associated with a bioengineer, the intertidal mussel Perna perna, we tested hypotheses about the relative importance of larval export from protected populations in marine reserves. Harvesting led to the replacement of P. perna and the domination of shores outside reserves by turf-forming coralline algae, mostly Corallina spp. We determined whether the diverse fauna recruiting onto artificial units of habitat placed within mussel beds differed between reserves and non-reserve areas or whether shores outside reserves, and open to harvesting, received recruits through larval export from reserves. Furthermore, we determined whether this was affected by the distance away from reserves and whether colonisation was achieved by movement of adults from surrounding biogenic habitats or via the plankton. Overall, we found no effect of increasing distance away from a reserve on the cover of adult mussels or associated fauna. We found strong effects of the presence of marine reserves on abundances of molluscs and polychaetes but not crustaceans. There were greater densities of molluscs in sites with a reserve (i.e. inside reserves, and up to 5 km outside reserve boundaries), but more polychaetes in exploited sites. For molluscs, this pattern was driven by gastropods rather than bivalves. Furthermore, although reserves had greater cover of adult mussels than non-reserve areas, recruitment of mussels was not greater inside or near to reserves. Our study illustrates the effectiveness of these reserves in protecting stocks of adult mussels, and although there was no evidence that reserves provided export of the larvae of mussels (the target species), they did provide larval export of non-targeted associated species. By protecting a harvested bioengineer and through export of the larvae of its associated fauna, these reserves fulfil some, but not all the conservation aims of a marine protected area.     

Factors related to the distribution and prevalence of the fungal pathogen Batrachochytrium dendrobatidis in Rana cascadae and other amphibians in the Klamath Mountains

The fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes the disease chytridiomycosis, has been associated with declines and extinctions of montane amphibians worldwide. To gain insight into factors affecting its distribution and prevalence we focus on the amphibian community of the Klamath Mountains in northwest California. The Cascades frog (Rana cascadae), one of the most common amphibians in these mountains, experienced increased mortality as a result of Bd exposure in laboratory trials and has experienced recent, dramatic declines in other parts of California. We surveyed 112 sites in the Klamaths, all of which supported R. cascadae between 1999 and 2002, for amphibians and Bd to (1) determine the distribution of Bd, (2) evaluate changes in the distribution of R. cascadae, and (3) assess associations between potential biotic and abiotic drivers and Bd infection. Bd was widely distributed in the Klamath Mountains – we detected the pathogen at 64% of sites. R. cascadae was found at 79% of sites, and was often infected with Bd. These results suggest that Bd has not caused dramatic declines in R. cascadae in the Klamaths in recent years. Subadult R. cascadae had a higher Bd prevalence than other R. cascadae life stages (subadults: 36%, adults: 25%, metamorphs: 4%, larvae: 1%), and while the probability of infection decreased over the season for adults, it did not for subadults, suggesting that subadults may be more vulnerable to chytridiomycosis than other R. cascadae life stages. Bd prevalence in R. cascadae was highest early in the season at high-elevation sites, which may indicate that populations inhabiting high elevation sites may have a greater risk of being affected by chytridiomycosis. Three other common amphibian species also tested positive for Bd: Pacific chorus frog (Pseudacris regilla), western toad (Anaxyrus boreas), and rough-skinned newt (Taricha granulosa).     

Vegetational changes associated with recreational use and fire suppression in the Eagle Cap Wilderness, Oregon: Some management implications

Construction and use of trails and campsites, grazing by recreational packstock, and suppression of fires have altered the vegetation of the Eagle Cap Wilderness Area in northeastern Oregon, USA. The amount and type of alteration has varied among vegetation types and with the kind of activity. Changes attributed to intensive recreational use are localised but severe, particularly in more densely forested areas. Suppression of fires has produced subtle but widespread changes. Current attempts to minimise these changes are often inadequate due to the lack of ecological information and the difficulties of implementing regulations. Management suggestions are offered.