Ring Species

I thought I'd return to an old favourite of mine- evolution. What I find particularly annoying is the attitude of the religious fundamental brigade and their insistence that there is no concrete evidence for evolution, whatsoever. Frankly, it makes me wanna burn stuff. Why are they so insistent that there can be no evolutionary change from one species to another? They will not acknowledge that populations change, over time, in the thrall of evolutionary pressures, eventually giving rise to genetically separate species. The answer is quite simple and quite sad: adherents dismiss evolution as a mechanism of speciation because it appears contrary to scripture, or God's majesty, or not in keeping with the contradictory accounts in Genesis. Never mind that the evidence is multifarious, deep and gathered from diverse subjects, various. Never mind that the basic tenets of evolution, through natural selection, have stood the test of time since first proposed by Charles Darwin in 1859. 

 I would like to introduce a further skein of evidence. The 'fundies' are wont to insist that micro-evolution exists, but macro-evolution does not. And they understand macro-evolution as the formation of a new species from an existing one. In this regard, I will define a distinct species at its most basic: a discrete reproducing population able to produce reproductively viable offspring. There are other ways of defining a species, but this basic definition will suffice for the purpose of this post.

Today's post will take an askew glance (steady Flaxen, you are starting to wax lyrical) at 'Ring Species' as evidence for macro-evolution. This is useful for illustrating an oft-neglected part of evolution. Whilst the accepted definitions deal with discrete entities, it should be acknowledged that the path of evolution involves a continuum, of individuals, with varying degrees of 'change' from the population they are evolving from. Ultimately, at its most fundamental, evolution concerns the individual. The human mind desires discrete concepts that can be neatly placed within conceptual boxes. We abhor gradation and messy transitions expressed as a spectrum of traits. Tis tough because real biology is particularly squelchy.

For my prime example, I would like to proffer the majestic Larus gull, and its ilk, emerging, stage left...

These gulls are cited as the textbook example of a ring species. The arctic is circumscribed by land, continental and island chains. The adaptable gull has colonised these lands to the full. Individuals are able to freely reproduce with the adjacent gull populations, as to be expected. What might surprise some are that discrete populations on opposite sides of the arctic are unable to reproduce with each other and therefore fulfil our definition of distinct and separate species. However, if we track reproductive viability between adjacent populations of gulls anywhere upon the 'ring', we observe full reproductive viability. This is an oversimplification of the real situation, of course. Biology is never as succinct and 'sanitised' as depicted in the textbooks and in reality, is generally a lot messier, and dare I say- squelchy. Those of a sensitive nature may have realised that I have not been taking my prescribed medication, of late. Arse. 

There are other examples of ring species in the biological world but the aforementioned gull is a prime, but not uncontroversial, example of the concept under consideration. How many separate and reproductively discrete gull species are present in our sample/example? Tis difficult to say, precisely, and is dependent on a particular geographic perspective. The gulls on 'opposite sides', because of their inability to interact and exchange genetic information will continue to diverge genetically as natural selection fixates advantageous genetic traits, within the given environment. There is also the mechanism of 'genetic drift' to contend with. This refers to the fluctuation and fixation of genetic traits based upon chance genetic change. This is particularly pertinent to small breeding populations. Mayhap sparse gull populations on the smaller arctic islands could be prone to this genetic phenomenon. However, this is pure speculation on my behalf. We should never rule out the possibility that my musings are just the reverie, or fevered phantasm, of a disordered mind devoid of pharmacological induced stability.   

In this brief and simple post, I hope I have cited a concrete and ongoing example of evolution in action ultimately depicting speciation. Fundamental Christians should take note. Their sensible 'progressive' and liberal brethren have taken on board evolution as a legitimate mechanism for biological change, even though they wrongly ascribe said mechanism to their mythical, non-evidential deity. However, their scientifically unenlightened, fellow Christians, are unlikely to change as they are irrevocably wedded to a pre-enlightenment system of religious doctrine and dogma. But what more can we expect from a group who collectively consider the Earth to be no more than 6,000 years old and consider fossils, of obvious ancient origins, to have been spuriously planted at the behest of a mischievous and very naughty god.