ijuin wrote:WriteBrainedJR wrote:Misanthropic Scott wrote: Actually, I'm going to need to ask for a link to something backing up that claim about insects. They may be the most diverse group of animals. They are certainly not more numerous than bacteria.
A major problem with determining the number of bacteria species is that the classic definition of "species" (i.e. the ability/inability to interbreed) does not properly apply to creatures that almost exclusively reproduce asexually. Thus, we have to fall back on genetic analysis and make something of an arbitrary distinction regarding how different two bacterial strains must be in order to qualify as distinct species.
That old definition of species doesn't work even for sexually reproducing species. We've learned a lot since then. For example, many black duck females prefer the showier mallard males. They breed fertile offspring and are still recognized as different species, even with the existence of hybrids. Similarly, homo sapiens interbred with homo neanderthalensis. No one suggests that these are the same species.
So, the whole concept of species has gotten somewhat muddled and is somewhat subjective for closely related species. That's why groups formerly called subspecies may now be granted full species status and vice versa. The lines are being redrawn in light of new information and subjective analyses. Gorillas used to all be considered the same species with separate subspecies. Now we recognize mountain gorillas, western lowland gorillas, and eastern lowland gorillas as three separate species.
So, even within hominoidia, the lines are not clear.
I expect such debates will go on for quite some time, sometimes in light of our changing understanding of the relationships between species, sometimes without changing our understanding of such relationships at all, merely reflecting growing understanding of what it means to be a species.
The problem actually stems from the entire Linnean system of classification. There is no way in this system to express intermediate species. Every species gets a full binomial name. A third name may indicate subspecies. But still, each and every individual ends up classed into one definitive bucket. Perhaps an increased understanding will replace the Linnean system with an updated and more expressive system. For now, expect continued confusion about naming even when all relationships are well known.