An odd title for a post to be sure, but hopefully it will be an illustrative one. I have been writing of late of species recognition and how different species recongise each other and by extension how we ourselves recognise them. While I don’t want to drift off into an essay on species definitions fun* thought that may be, there is an issue here both for palaeoartists and biologists as a whole that I intend to illustrate with a pair of pheasants that rank among my most favourite, and certainly most beautiful, birds.
*For a given value of ‘fun’, your enjoyment may vary.
Behold Lady Amherst’s Pheasant, Chrysolophus amherstiae, probably my favourite bird. What is important to note here is the pattern of the various coloured sections on the animal as opposed to the actual colours themselves. The striped tail, tail base section, upper chest, body, crown, and nape of the neck are clearly defined sections and easily distinguished from each other. It’s not the best photo of the animal to show off either the wonderful colours or the exact pattern and distribution of those various swatches of colour, but should give you a good idea and serve as sufficient for comparison to our second bird.
This is the Golden Pheasent Chrysolophus pictus, rather obviously a close relative both from the name but also from the actual pattern of the feathers. Again the picture is far from perfect for comparison (great photo that it is – courtesy of Roger Close again – both photos from the Beijing Zoo by the way). At least the crown, striped tail, nape, front and base of the tail should all be fairly clear and recongisable as being identical to the pattern of the Amherst, even if the colours themselves are remarkably and dramatically different.
This is interesting for a number of reasons and especially when you take into account that they are the only two species in their genus and in the wild their range does overlap (very slightly admittedly) and in captivity at least they certainly can interbreed (though I don’t know if this can go to a second generation or if they produce sterile offspring).
Now I really don’t know much about them as living animals or their evolutionary history (and indeed while I have not looked into it, given our average knowledge of most living taxa, my guess is that no one knows that much) but these are pretty much by definition very closely animals that split from some common ancestor not too long ago. Nevertheless despite their similar habits and habitats and similar gross anatomy, somewhere along the line one (or possibly both) underwent a massive shift in colour, while still retaining the underlying pattern on which those colours are laid out.
Two quick things then (in brief, after all that build up):
1. Palaeoartists: I’d love to see something like this done more often. Living species at least on some occasions can be well separated by ‘superficial’ differences like colour and pattern (and indeed, taxonomists take note too!).
2. Some species don’t *care* what criterion use use to distinguish them (which characteristics or species concepts) some can and do interbreed even when you think they are quite different and others keep their reproductives lives well separated even when they look the same to us. Furthermore, although obviously there may well be a history of geographic separation, the fact that these animals can and do interbreed and overlap in the wild suggest that these species have separated and produced two different species despite these issues. I wouldn’t want to use it as a concrete example without knowing more about them, but I would argue that it is highly suggestive that ‘mere’ colour differences and perhaps mating preferences can produce dramatically different looks in animals that are otherwise morphologically near identical.
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