Paper: The nature of plant species

The nature of plant species
Loren H. Rieseberg, Troy E. Wood and Eric J. Baack

Many botanists doubt the existence of plant species viewing them as
arbitrary constructs of the human mind, as opposed to discrete, objective
entities that represent reproductively independent lineages or 'units of
evolution'. However, the discreteness of plant species and their
correspondence with reproductive communities have not been tested
quantitatively, allowing zoologists to argue that botanists have been overly
influenced by a few 'botanical horror stories', such as dandelions,
blackberries and oaks. Here we analyse phenetic and/or crossing
relationships in over 400 genera of plants and animals. We show that
although discrete phenotypic clusters exist in most genera (> 80%), the
correspondence of taxonomic species to these clusters is poor (< 60%) and no
different between plants and animals. Lack of congruence is caused by
polyploidy, asexual reproduction and over-differentiation by taxonomists,
but not by contemporary hybridization. Nonetheless, crossability data
indicate that 70% of taxonomic species and 75% of phenotypic clusters in
plants correspond to reproductively independent lineages (as measured by
postmating isolation), and thus represent biologically real entities.
Contrary to conventional wisdom, plant species are more likely than animal
species to represent reproductively independent lineages.

Abstract and Full text Links at Nature
http://www.nature.com/nature/journal/v440/n7083/abs/nature04402.html

Posted by
Robert Karl Stonjek


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