Chris, at Organic Matter, offers this thoughtful post about taxonomy, one of my favorite messes. The current debate over species organization is concerned with two possible modes of classification. The Biological Species Concept (BSC) is based on breeding potential (that is, if duck A can make a duckling with Duck B, the two birds are the same species). The BSC results in fewer distinct species, but some biologists insist that it is overly simplified. The Phenetic and Phylogenetic Species Concept (PSC) are based on distinct characteristics, both genetic or physiological; it makes for many more distinct species, but requires an extensive overhaul of the current arrangement. Still other biologists call for a unitary, web-based alternative, a kind of Wiki-taxa open to all users, but designed and funded by an international committee of serious taxonomists. Whatever system biology opts for, confusion is likely to remain constant for a long while. What will such biological debates mean for conservation biology at large? Politicians love simple answers to complex questions; taxonomy, like most sciences, has few simple answers...unless, of course, we fudge the science. (See also Dave Roberts' post at Gristmill.)
Observable instances of natural selection don't get much better than this. In the November 29, 2004 issue of PNAS (Proceeding of the National Academy of Sciences), Ben Phillips and Richard Shine published this study (unfortunately, you can only read the abstract) on the effect of cane toads (Bufo marinus), an introduced species, on native Australian snake populations. Because the toads are large and toxic when full grown, snakes capable of swallowing the adult cane toad are more likely to be poisoned. Since the introduction of the cane toad in 1935, snake head sizes have been gradually shrinking relative to body size. You gotta love this stuff! Those folks dunderheaded enough to still decry evolutionary theory are also missing out on the fun!
Are you into exotic pets? If so, you're not alone. With nearly 7,000 tigers kept as pets and only 2,500 remaining in the wild, it's clear that more and more people are bringing wild animals into their homes. As a keeper of multiple pythons and, at various times throughout my life, Northern flying squirrels, European starlings, Eastern box turtles, snapping turtles, and several species of snake, frog, and toad, I understand the desire to keep wild animals in captivity. One can learn a lot about animal behavior and develop a life long love of other species. But I think it cruel in all but the most exceptional cases and, although I'd like to keep a starling or crow again, I view these animals less as pets than as creatures in my care. (Reptiles and amphibians, if reasonably sized, do fairly well in captivity, but I get very upset when I see a reptile owner being careless with temperature/humidity control or mishandling the animal.) Their needs are often specific and unusual and I fear most people purchasing a caracal or kinkajou don't think about long-term commitment; these animals are impulse buys.
I'm reminded of the "Mr. Show" "Sulu the Iguana" skit in which David Cross gets angry at his "pet" iguana for knocking over his bong, beats it to death with an encyclopedia, and then sobs over the reptile's body. Undaunted in his quest to be the most "original" pet owner, however, David buys a "real, live albino boy" to replace the iguana. Funny though it may be, it accurately depicts the selfish impetus of many exotic pet owners.