Magazine article Oceanus

Describing Diversity: Too Many New Species, Too Few Taxonomists

Magazine article Oceanus

Describing Diversity: Too Many New Species, Too Few Taxonomists

Article excerpt

Marine biodiversity can be defined as the number of species occurring within a circumscribed region or habitat. Consequently, for biodiversity to be understood, taxonomists - scientists who describe and name species - must have a chance to examine the flora and fauna of the region or habitat under consideration.

Since the oceans occupy approximately 71 percent of the earth's surface it is reasonable to suppose that a large proportion of the world's species will be found there, and indeed existing evidence already shows that the oceans harbor a great variety of life. Two-thirds of the world ocean floor is deeper than 2,000 meters (1.2 miles). First evidence for the very great biological diversity of these abyssal depths has come within the past 30 years with the introduction of finer mesh screens (less than 0.5 millimeters, 1/50 inch) for separating organisms from the bottom sediments that most species inhabit (see The Deep Sea: Desert AND Rainforest, Oceanus Fall/Winter 1995). Since most organisms from samples taken before 1965 were lost through the coarse mesh screens previously used, analysis of these samples gave a grossly distorted estimate of diversity in the deep sea. It now has become apparent that the deep sea bottom fauna includes untold numbers of heretofore undescribed species, many never previously encountered. Recent estimates of the numbers of deep-sea species vary a hundredfold, from hundreds of thousands upwards to ten million.

Yet the study of this newly discovered diverse fauna has only just begun. There are on the shelves of laboratories and museums of North America and Europe thousands of unnamed species collected within the past three decades on expeditions of American, French, Russian, and British research ships.

For example, among the superorder pericarida, a major taxon that includes most of the minute bottom-dwelling crustacea of the deep sea, 69 percent among those found in the western Atlantic during the past 30 years are newly discovered species. Though some of these have received attention, most remain to be named and described. Among the 236 species of polychaete worms from the deep western North Atlantic, 64 percent are undescribed, and among bivalve mollusca, one of the better known groups of the deep-sea benthos, 105 new species (about 43 percent of all species collected) have been described over the last 20 years. Only one-third of the collected species of Aplacophoran molluscs have been named and described even though they are an important component of the deep-sea fauna and often appear among the ten most abundant species.

Meanwhile, the number of undescribed new species grows unrelentingly with each additional deep-sea dredge sample - and biologists estimate that a total area of only 500 square meters (635 square feet) of the world ocean floor has been sampled!

Shallower regions off continents are also undercollected in many parts of the world. Recent reports indicate that one-third (124 species) of all polychaete worms collected from Georges Bank are undescribed and unnamed, while a small sample of coral sand from a fringing reef off one of the Hawaiian Island (about as much as fits in six one-quart pickle jars) produced 112 new species (78 percent of all species present in the sample). Ninety-two percent of the flatworms (123 species) collected from two locations on Australia's Great Barrier Reef were new. Shore collections made in tropical lagoons, from coral reefs, and even from rocky shores continue to yield large numbers of new unnamed species.

The question now arises: "Is it really necessary to name and describe every species in order to understand the biological diversity of a particular fauna?" The structures of different bottom communities exhibit striking differences. For example, on the bottom of Buzzards Bay near Woods Hole, Massachusetts, samples from 19 meters depth yielded 79 species of macro-invertebrates exceeding 0.5 millimeter in size. …

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