[Taxacom] barcode of life

Steve Manning sdmanning at asub.edu
Thu Jul 1 09:43:04 CDT 2010


It is interesting that I have not detected anywhere near as much 
controversy or discussion about delimitation of Genera, Families, and 
other taxa more general in the hierarchy than species - yet surely 
there has to be even less precision possible in defining their 
boundaries than those of species(?).

Steve

At 02:52 AM 7/1/2010, Stephen Thorpe wrote:
> >better to leave religion out of it and keep it simple
>
>but it ain't simple either way!
>
> >but this leads to all the different beliefs on what constitutes 
> "reproductive isolation" ...
>
>this is the point that nobody gets! You have to consider two cases, 
>viz. the "in practice" case, and the "theoretical basis" case which 
>underpins it
>
>In practice, there is less disagreement about what constitutes 
>reproductive isolation than there would be if every faction could 
>just have their own species to suit themselves. In other words, 
>reproductive isolation "works". It isn't perfectly precise and 
>objective, but I bet (at least) 9 times out of 10 when two 
>taxonomists just consider reproductive isolation as a criterion, 
>they will agree on species boundaries. Most disagreement seems to 
>arise from differing "species concepts" (i.e., biological, 
>morphological, phylogenetic, etc.)
>
>The theoretical basis which underpins this goes something like this: 
>take topography as an example. It describes a real objective feature 
>of the world, yet there are different altitudes, and the contour map 
>will be different for each choice of altitude. But this "dimensional 
>aspect" doesn't imply subjectivity. Similarly, choose whatever level 
>of reproductive isolation you like and draw the species boundaries 
>for that choice. This will also describe a real objective feature of 
>the world. In practice we cannot measure reproductive isolation very 
>precisely at all, but luckily in most cases the result will be the 
>same for a wide range of choices that would cover most peoples idea 
>of the appropriate level for drawing the map. Of course there will 
>be some problem cases, but by and large I suggest there would be 
>more agreement than doing it any other way ...
>
>Stephen
>
>PS: If we accept "Pylean subjectivity", then we cannot criticise 
>molecular taxonomists for describing cryptic species to suit 
>themselves, as it is none of our concern. We just have to ignore 
>them, and do it our way. I don't know quite where this would leave 
>global biodiversity databases like EoL, etc.? Maybe we need one for 
>the molecular species, one for the biological species, one for the 
>morphological species, one for the phylogenetic species, etc....
>
>
>
>________________________________
>From: "dipteryx at freeler.nl" <dipteryx at freeler.nl>
>To: taxacom at mailman.nhm.ku.edu
>Sent: Thu, 1 July, 2010 7:21:57 PM
>Subject: Re: [Taxacom] barcode of life
>
>Van: taxacom-bounces at mailman.nhm.ku.edu namens Stephen Thorpe
>Verzonden: do 1-7-2010 7:03
>
> > but this leads to different factions of "the community"
> > (=different communities) with their own species
>
> > better to try to hold on to reproductive isolation
> > as the one true canonical criterion of species boundaries ...
>
>***
>but this leads to all the different beliefs on what constitutes
>"reproductive isolation" ...
>
>better to leave religion out of it and keep it simple.
>
>Paul
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