Un reciente artículo en Nature presenta los resultados de una meta-análisis que sintetiza la información de numerosos experimentos que en los últimos años han tratado de determinar la existencia y naturaleza de la relación entre biodiversidad y funcionamiento de los ecosistemas. Los resultados refuerzan la “teoría de muestreo” (sampling theory) que explica las amyores abundancias o biomasas de ecosistemas más diversos por la mayor probabilidad de aparición de especies muy productivas en estos sistemas. Este meta-análisis tiene la ventaja de demostrar la consistencia de estos efectos en diferentes grupos tróficos y tipos de ecosistemas sintetizando la información que se discute en el Tema 2 (y que aparece en la bibliografía recomendada, donde se ha incluído este estudio).
Cardinale BJ et al. (2006). Effects of biodiversity on the functioning of trophic groups and ecosystems. Nature 443:989-992. [pdf]. Resumen:
Over the past decade, accelerating rates of species extinction have prompted an increasing number of studies to reduce species diversity experimentally and examine how this alters the efficiency by which communities capture resources and convert those into biomass. So far, the generality of patterns and processes observed in individual studies have been the subjects of considerable debate. Here we present a formal meta-analysis of studies that have experimentally manipulated species diversity to examine how it affects the functioning of numerous trophic groups in multiple types of ecosystem. We show that the average effect of decreasing species richness is to decrease the abundance or biomass of the focal trophic group, leading to less complete depletion of resources used by that group. At the same time, analyses reveal that the standing stock of, and resource depletion by, the most species-rich polyculture tends to be no different from that of the single most productive species used in an experiment. Of the known mechanisms that might explain these trends, results are most consistent with what is called the 'sampling effect', which occurs when diverse communities are more likely to contain and become dominated by the most productive species. Whether this mechanism is widespread in natural communities is currently controversial. Patterns we report are remarkably consistent for four different trophic groups (producers, herbivores, detritivores and predators) and two major ecosystem types (aquatic and terrestrial). Collectively, our analyses suggest that the average species loss does indeed affect the functioning of a wide variety of organisms and ecosystems, but the magnitude of these effects is ultimately determined by the identity of species that are going extinct.
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