Are there any examples of a group of micro-organisms where two different, established species are designated and these two groups meet all aspects of the definition of species (perhaps can not reproduce with each other?), but it turns out that there is a continuous distribution of occurences of this group such that they can reproduce "locally" with nearby members?

I lack the sophistication in biology to know the best possible words to use here so some guidance is welcome, and since the concept of species classification has been around much longer than genome sequencing and analysis, the topic itself draws on concepts from several different centuries.

So I've draw a simple diagram with a 1-D simplified "spectrum" of genetic difference, whereas of course it would likely be multi-dimensional.

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  • $\begingroup$ I think the biggest problem for this question is that most microorganisms only reproduce asexually (by copying themselves). At that point the definition of where one species ends and the next begins has to be done one either observable characteristics or on a sequence basis. At least for sequence based species classification a 'spectrum' is possible, but then the classical species definition doesn't make sense anymore. $\endgroup$
    – Nicolai
    Sep 17 '18 at 7:55
  • $\begingroup$ @Nicolai It seems that I've seen too many Gary Larson cartoons; yes of course most do reproduce asexually. I wonder how to proceed — do you think the question is answerable as-is in some way, or should I modify the question? If you can expand on your comment a bit as an answer, that might be enough, especially if you touch on species classification in microorganisms. Or, I could just ask "how was species classification done for microorganisms before DNA sequencing?" separately. $\endgroup$
    – uhoh
    Sep 17 '18 at 8:00
  • $\begingroup$ For those who learned about biology sans Larson: (e.g. 1, 2, 3, 4) $\endgroup$
    – uhoh
    Sep 17 '18 at 8:06
  • 1
    $\begingroup$ @uhoh classification of bacterial species before DNA sequencing relied on morphological, physiological, and ecological characteristics. $\endgroup$
    – user37894
    Sep 17 '18 at 12:45

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