Ancient ecosystems organized much like our own

April 29th, 2008 - 2:50 pm ICT by admin  

Washington, April 29 (ANI): A new study has determined that networks of feeding relationships among marine species that lived hundreds of millions of years ago are remarkably similar to those of today.

Conducted by researchers from the Santa Fe Institute in New Mexico, Microsoft Research Cambridge, and other institutions, the study is the first to reconstruct detailed food webs for ancient ecosystems.

Food webs depict the feeding interactions among species within habitats - like food chains, only more complex and realistic.

The discovery of strong and enduring regularities in how such webs are organized will help in the understanding of the history and evolution of life, and could provide insights for modern ecology - such as how ecosystems will respond to biological extinctions and invasions.

A multidisciplinary group of scientists led by ecologist Jennifer Dunne of the Santa Fe Institute and the Pacific Ecoinformatics and Computational Ecology Lab in Berkeley, California, studied the food webs of sea creatures preserved in rocks from the Cambrian.

During the Cambrian period, there was an explosion of diversity of multicellular organisms - including early precursors to todays species as well as many strange animals that were evolutionary dead ends.

The researchers compiled data from the 505 million-year-old Burgess Shale in British Columbia, Canada and the even earlier Chengjiang Shale of eastern Yunnan Province, China, dating from 520 million years ago.

Both fossil-rich assemblages are unusual because they have exquisitely preserved soft-body parts for a wide range of species.

The researchers determined who was eating whom by piecing together a variety of clues. In most cases, feeding interactions were inferred from where species lived and what body parts they had.

For example, grasping claws, swimming lobes, big eyes, and toothy mouthparts suggest that Anomalocaris canadensis, a large, unusual organism with no modern descendents, was a formidable predator of trilobites and other arthropods, consistent with bite marks found on some fossils.

To compare the organization of Cambrian and recent ecosystems, the team used methods for studying network structure, including new approaches for analyzing uncertainty in the fossil data.

The Cambrian food webs share many similarities with modern webs, such as how many species are expected to be omnivores or cannibals, and the distribution of how many types of prey each species has.

Such regularities, and any differences, become apparent only when variation in the number of species and links among webs is accounted for.

There are a few intriguing differences with modern webs, particularly in the earlier Chengjiang Shale web. However, in general, it doesnt seem to matter what species, or environment, or evolutionary history youve got, you see many of the same sorts of food-web patterns, explained Dunne. (ANI)

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