Mites and poor diet contribute to honeybee decline in Europe

Two timely reports have surfaced this week regarding the decline of honeybee populations in Europe, and France has taken action in an attempt to curb the falling numbers.  A recent study linked honeybee health and plant biodiversity In a study published in the Journal of Apicultural Research, scientists have found that managed honeybee populations across Europe have dropped an average of 20 percent over the last 20 years, with England being hit the hardest at a 54 percent decline. Simon Potts and colleagues from the University of Reading analyzed several patterns across 18 countries in Europe and found the mite Varroa destructor–a parasite responsible for transmitting infections in honeybee colonies—infested virtually every honeybee colony they examined. In another study, scientists from the French National Institute for Agricultural Research (INRA) in Avignon reported a possible dietary connection between the strength of the honeybee immune system and plant biodiversity.  Cedric Alaux, who co-authored the study published in Biology Letters, told BBC News:    We found that bees fed with a mix of five different pollens had higher levels of glucose oxidase compared to bees fed with pollen from one single type of flower, even if that single flower had a higher protein content.  Bees use glucose oxidase to sterilize colony and brood food in an effort to make the hive resistant to infection. As Alaux told BBC, a more diverse diet, therefore, might help a honeybee colony protect against pathogen invasion.   These studies emerge amidst France’s recent decision to sow nectar-bearing flowers alongside 250 kilometers (155 miles) of roadway in an effort to boost honeybee populations. If the results from the three-year test are positive, France is prepared to extend the flowers along the country’s 12,000-kilometer (7,500-mile) network of non-toll roads.  Read more at BBC and the Telegraph.    Photo Credit: http://www.flickr.com/photos/aussiegall/ / CC BY 2.0 Potts, S., Settele, J., Neumann,, P., Jones, R., Mike A Brown, M., Marris, G., Dean, R., & Roberts, S. (2010). Declines of managed honey bees and beekeepers in Europe Journal of Apicultural Research, 49 (1) DOI:...

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Reduced predator populations lead to algal blooms

Algal blooms are a phenomenon in which algal populations in a marine area proliferate rapidly, creating a water-column shield that blocks sunlight and oxygen. These blooms are usually attributed to rises in nitrogen levels from human agriculture and industrial runoff, which fertilize the algae. But a study in the current issue of Ecological Applications shows that overfishing of top fish predators can also lead to algal blooms. Satellite image of a large algal bloom in the Bering Sea in 1998. After reviewing a year’s worth of data on the Baltic Sea, the authors found that areas with high algal concentrations also had large populations of small fish and small populations of large fish. Specifically, predatory perch and pike shortages resulted in a 50 percent chance of that area experiencing an algal bloom, compared to only a 10 percent chance in normal areas. Experimental studies in which the authors excluded top predators from marine areas corroborated the findings. Lead author Britas Klemens Eriksson of the University of Groningen in the Netherlands says this pattern suggests that the problem is a trophic one: when top predators are scarce, their smaller fish prey become more abundant and eat more invertebrates. These invertebrates feed primarily on algae, so when their numbers are reduced, algae can grow freely. Eriksson says that the key to controlling algal blooms may not be through simply controlling nitrogen, but also by controlling fishing. Said Eriksson in the Nature article: If we want to manage algal blooms effectively, we need to start by taking an ecosystem perspective … we have to restore depleted fish communities. Read the paper in Ecological Applications here (abstract; full-text by subscription), and rest of the Nature article here. Eriksson, B., Ljunggren, L., Sandström, A., Johansson, G., Mattila, J., Rubach, A., Råberg, S., & Snickars, M. (2009). Declines in predatory fish promote bloom-forming macroalgae Ecological Applications, 19 (8), 1975-1988 DOI:...

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A better diversity index?

A paper out online in the August issue of Ecology Letters presents a new index for estimating biodiversity. John Harte of UC Berkeley and his colleagues have developed a method that they say yields more precise measures of biodiversity than classic indices, such as Simpson’s and Shannon’s diversity indices. In an argument similar (but reversed) to that for quantum physics, Harte explains that fractal geometry helps to explain distributions at small scales, but not at large scales. Like most other indices, their new model uses an entropy index. Harte and his colleagues Adam Smith of UC Berkeley and David Storch of Charles University in Prague, Czech Republic, used insights from information theory, often used in thermodynamics and statistical mechanics. They say that maximizing the information entropy, or minimizing assumptions of the unknown based on small plot samples, led to a better prediction of species-area relationships. Harte and his colleagues used their theory to estimate biodiversity the Western Ghats mountain range of India overlooking the Arabian Sea. Nearly 60,000 square kilometers, the Western Ghats are partially protected and have been studied extensively by Indian scientists in 48 quarter-hectare plots and through large-scale surveys. Earlier species-area theories predict between 400 and 500 species of trees throughout the range, but to date, Indian scientists have documented more than 900 tree species in the preserve. Harte’s theory estimates around 1,070. Said Harte in a press release: “People have been finding different curves when looking at different organisms or in different habitats, but in fact, all these curves are the same. There really is a universal curve people are sampling, they are just sampling along different parts of the curve depending on the habitat or class of organisms.” Harte , J., Smith, A., & Storch, D. (2009). Biodiversity scales from plots to biomes with a universal species-area curve Ecology Letters, 12 (8), 789-797 DOI:...

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