[Taxacom] What is Homo sapiens

[John Grehan]

I would agree with the possibility that a multicotomy may represent a
multicotomous differentiation event. To my understanding a multicotomy is
poorly resolved by definition. Whether it is possible to further resolve
depends on what character information is found in the future. As for the
differentiation process, the branching sequence is not the only possible
information. There is also distribution. Many years ago there was a case of
several allopatric taxa all next to each other in a jigsaw pattern. The
cladogram identified the two most distant and separated (by other species)
taxa as sister groups. The authors therefore posited dispersal from one end
to the other somehow. An alternative is that in this case the character
similarities better tracked a sequence of character divergence than species
divergence - at least as one possibility.

John Grehan

On Fri, Jun 1, 2018 at 12:50 PM, Adam Cotton <adamcot at cscoms.com> wrote:

> ----- Original Message ----- From: "John Grehan" <calabar.john at gmail.com>
> To: "Richard Zander" <Richard.Zander at mobot.org>
> Cc: "taxacom" <taxacom at mailman.nhm.ku.edu>
> Sent: Friday, June 01, 2018 10:43 PM
> Subject: Re: [Taxacom] What is Homo sapiens
>
>
> All systematic arrangements may be viewed as artifacts of a particular
>> method - whether cladistic, phenetic, Zandean etc. Whether or not they
>> model anything in nature is a matter of individual interpretation. Just
>> because cladistic methods may generate dichotomies (as can phenetic
>> methods) it does not mean that speciation has to be dichotomous. The fact
>> that dichotomies are often found may suggest that dicotomous speciation is
>> common, or that character relationships are often resolvable to
>> dichotomous
>> arrangements - at least in my opinion.
>>
>> John Grehan
>>
>>
>>
>
> This is one point I have been thinking about for the past day or so as a
> result of posts on Taxacom.
>
> Generally it is assumed that when a tree has multiple branches arising
> from a single node it must be poorly resolved. However, it occurred to me
> that it is quite possible that several new species could arise
> simultaneously from a single ancestor species.
>
> I can easily envisage that when sea level was lower a single species could
> have inhabited what are now the islands of Indonesia, for example. Rising
> sea levels would then isolate the populations on each island, and over time
> they would speciate, creating a number of different species at the same
> time (not instantaneous of course) from a single ancestor species.
>
> Is there a way to test whether such a node is reliable? I should mention
> that I do not actually run analyses myself; I am more of a traditional
> taxonomist involved in DNA research, partly to ensure that the taxa are
> correctly identified. It is quite possible there is an obvious answer to my
> question, and if so I would be interested to hear it.
>
> Adam.
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