[Taxacom] barcode of life

Stephen Thorpe stephen_thorpe at yahoo.co.nz
Thu Jul 1 02:52:00 CDT 2010


>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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