BIOLOGY OF A SCALE-INDEPENDENT PREDATOR-PREY INTERACTION

Dense populations of epifaunal, suspension-feeding ophiuroids, or brittlestar beds, are widely distributed geographically, but they are rare and are restricted in their habitat distribution. On a microecological scale (meters to kilometers, hours to days), experimental studies and censuses of sublethal injury show the distribution of brittlestar beds in the British Isles and the Bahamas to be limited by predatory fishes and crabs. On an ecological scale (tens to hundreds of km, decades to centuries), there is evidence that predation by seastars limits the distribution of brittlestar beds in the English Channel, beyond the stringent restrictions imposed by fish and crab predators in modern ecosystems. On an evolutionary scale (globally, millions to tens of millions of years), the Mesozoic decline of brittle-star beds visible in the fossil record is associated with the diversification of predators adapted to eat skeletonized prey, including teleostean fishes, neoselachian sharks, and decapod crustaceans. In this biological interaction, microecological- and ecological-scale processes are reflected in evolutionary-scale patterns. The scale-independent effects of predation on brittlestar beds, and other scale-independent biological interactions, may be related to self-organized criticality, d consequence of the non-linear dynamics of the biosphere.