After staying up until 1am last night, finishing my last research paper, I’m done with finals. So, now, as I officially start my summer break, I can get back to blogging. I’d like to thank those of you have suffered through my infrequent postings lately, and especially those of you who wished me luck with my exams. I managed to complete 14.5 credit hours this semester, and keep my 4.0 (my sanity, on the other hand, may be long gone.) Thanks for your support!
Looking at speciation as both a scientific and philosophic question has been quite interesting. I’ve always been fascinated by the diversity of nature, amazed that so many unique and individual parts could work together as a whole, functioning and adapting system. Now, to have delved into the details of the system, my fascination has been enhanced, rather than dulled. For me, biology is like being drawn into a black hole of knowledge: The more I learn, the more I want to know. Someday, I may not be able to escape, and only be capable of speaking in Latin, algorithms, Punnett squares, and organic chemistry terms… but it will be well worth it.
With that, I’d like to present my “final” definition for speciation, which I turned in last week. (I’m still waiting to hear feedback from my biology professor on my Deinoccocus radiodurans paper–he saved it for last, still intending to “rip it to shreds”–so it may be awhile, or never, before I hear about this speciation exam.) I gave a tentative definition for a species awhile back, but didn’t quite look at the whole picture when doing so. This time around, I tried to change that. I’ll eventually discuss speciation in the paper I’m working on, showing how the process is influenced by basic dimensions, but for now, here are the basics:
What is a species?
What is a species? Since humans began defining concepts with the onset of language, we have probably been trying to define “species” for 10,000 years. After all of this time, are we even close? It is tempting to suggest the concept is a subjective human construction, having nothing to do with actual nature—but even the organisms we study have a sense species. Indeed, they must, in order to know who to eat, who to attack, or who to reproduce with. They understand their place in the ecosystem—so why can’t we?
The traditional definition for species, proposed by Ernst Mayr, based on reproduction, isn’t perfect. Most obviously, it lacks a way to distinguish between species that rely solely on asexual reproduction. (Is each bacterium, unable to produce fertile offspring with another through sexual means, its own species? Or are bacteria simply not species?) Also, because of Mayr’s definition, groups of animals separated by distance (perhaps on their way to speciation) are lumped together as the same species. In the case of the cactus ferruginous pygmy owl (Glaucidium brasilianum cactorum) pictured above, such lumping means certain extinction. The tiny owl, native to the Sonoran Desert, is about to be removed from the endangered species list, because it is no longer considered a distinct subspecies.
Take the case of Preble’s meadow jumping mouse (Zapus hudsonius preblei.) Last year, the US Fish and Wildlife service considered removing the mouse from endangered species lists, because it could not be considered distinct. A study by the U.S. Geological Survey found flaws in the previous conclusions, and decided, once and for all, that Preble’s meadow jumping mouse was sufficiently distinct and deserved protection. When we later decide that the ferruginous cactus pygmy owl is, after all, distinct and worthy of protection, like the mouse, the laws may change again. But, if the owl’s habitat has been developed, it will be too late to change our minds.
Every organism, regardless of type, fills a small niche in the ecosystem. The organism knows who is who; each cell (if healthy) has markers to distinguish it from a neighbor or a stranger. Likewise, a species determines its own kind, interacting with other species, whether antagonistically or symbiotically. No individual organism or species acts in isolation. Since there are many ways for organisms within a species to interact with their environment besides sexual reproduction, it seems naïve to base a definition solely on reproduction.
A species should be defined according to the unique differences defining its role within the ecosystem, whether distinguished by differences in DNA, reproductive mechanisms or abilities, or a distinct impact on the species’ habitat. Any group of distinct organisms that fill a distinct niche in its environment is a species. Distinctness should be determined by noting differences in physiology, reproduction, DNA, pathogenicity, symbiotic or antagonistic roles, or ecological impacts—whichever is appropriate to the organism.
Before we decide if the cactus ferruginous pygmy owl is sufficiently distinct, and deserves to be protected, we should look at the role the species plays in the environment. The Sonoran Desert is a delicate balance of autotrophs and heterotrophs. What will happen when we replace one of the top heterotrophs with pink plastic lawn flamingos?
Sources: Thanks to GrrlScientist for updates on the cactus ferruginous pygmy owl, in her lovely Birds in the News feature. Thanks to Alan, for updates on Preble’s meadow jumping mouse, in his daily news clips. Image of the owl in a cactus from the Arizona Game and Fish Department, via Blue Planet Biomes. Mouse image from the Center for Native Ecosystems.