Talk:Littorina

Self-contradict
"DNA analysis shows there is a significant genetic differentiation - not enough to consider these to be different species"

There is no absolute "cut-off" level of "enough" genetic distinctness that could be considered a "species threshold". It was once believed, but that theory is bullshit for a lot of reasons (in a nutshell, evolution does not work to suit researchers' desires of "clean" thresholds).

But the main point: "significant genetic differentiation", on its own, would imply that species status must seriously considered. So what's going on here? Genetic paraphyly? That's not a valid argument against species status (it is actually common between sister species). The question would have to be approached by a population-wide thorough sample, and if this shows at least some degree of genetic lineage sorting and consistent morphological distinctness, species status is more likely than not. Essentially, "distinct species" means "under natural conditions, reproductive isolation is dominant over gene flow". Thus, two recently-deverged species may be very similar genetically, but what counts is that they'll become ever more distinct as time progresses. And before species are reciprocally monophyletic, they are usually morphologically very distinct already (because morphological traits usually become established an order of magnitude faster than the sequences one studies in popgen/molphyl).

The source is unfortunately not accessible to me. I presume it lays out the case in more detail. Dysmorodrepanis (talk) 18:55, 14 September 2009 (UTC)

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