Part

Chapter Fourteen

Species of Concern

Rules of Thumb for Selecting — or Avoiding

Certain Fishes and Invertebrates

Living near the Great Smoky Mountains National Park gives me a different perspective on ecosystems than might be available to someone in an urban environment. Lacking a mature ecosystem conveniently available for observation, however, is no handicap to understanding basic ecology If you live in the suburbs, simply walk out to your backyard. Apartment dwellers, stroll down to the nearest park or vacant lot. Never mind the season. Although it will be easier during warm weather to observe the various kinds of plants growing, there is evidence of biodiversity even in winter. Try to pick a location that hasn't been mowed in a while. Now look closely at the plant life. There may be only a few species of plants present, but what you will observe is this: for a small proportion of the total number of species, many individuals will be present; for the majority, only a clump here and there; and for a third, also small, proportion of species, individuals will be rare, perhaps only one or two on the entire lot.

This arrangement will hold true for almost any location you choose, a vacant lot or a national park, a pond or a coral reef. In fact, the less disturbance the ecosystem lias

Although stunningly beautiful, crinoids, or 'feather stars," typically starve to death in captivity and should be avoided.

experienced, the more likely this kind of equilibrium of species will exist. What is the reason for this distribution?

The dynamic interaction of species with each other and with the conditions of their environment creates limits on the size of the population of one species versus another. Part of the reason has to do with the basic "life strategy" of each species. These strategies divide species into two groups, called by ecologists k-selected and r-selected species. (The "k" and V' refer to variables used in the mathematical formulas describing these two patterns of life.)

R-selected species are the spendthrifts of the ecosystem. They exhaust their energies on the here and now. These are typically the numerous species — individuals have many offspring but invest little in their care. Often, they care little for their surroundings, adapting themselves to make use of whatever the habitat has to offer. Alas, such profligate ways take a toll on the individual, and most r-selected species are short-lived. For some, a lifetime is less than an hour. Weeds are good examples of such species, as are the microalgae that sometimes undergo blooms in aquariums.

K-selected species, on the contrary, follow a less risky path. They live, literally, for the future. Among them, one may find the rarest species. Offspring are few, come late in life, and may receive lavish parental investment. For some of

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