Farewell to species - reticulation

B. J. Tindall bti at DSMZ.DE
Wed Feb 2 14:03:49 CST 2000

Pierre Deleporte wrote:

>There is obviously a field for experimental investigations on the line of
>"closing the gap between population biology and phylogenetic systematics":
>make hybrids and check for the resulting cladogram of the known lineage.
>The artificial selection of pidgeons by Darwin and the discovery of the
>genetic code was perhaps sufficient to support the idea of "descent with
>modification" as the general process in evolution, and this remains the
>general assumption supporting phylogeny reconstruction. But there is no
>reason to stop there, provided that it can be proved that more complexe
>processes (reticulation) leave clear traces behind.

I agree with the last part, but would also raise another point. What do we
mean by "descent with modification"? It certainly does not have to be point
mutation of the gene, one can have re-arrangement of the genome and tranfer
of genetic material and it can still be described as "descent with
modification". These are the kinds of things which bacteria like to do.
However, there also appear to be restrictions on such activities. This is
the kind of thing which is currently causing problems when looking at the
distribution of genes in total genomes, particularly of bacteria. The
system is rather more complex than we would like. After all if one accepts
the hypothesis outlined by Ken Kinman, that chloroplasts and mitochondria
are or prokaryotic origin it indicates that such complex events as even
mixing "lines of descent" plays a very important role in evolution.
Brian Tindall

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