Joined: Jan. 2006
|Quote (jeannot @ June 28 2007,14:27)|
|Quote (BWE @ June 28 2007,12:54)|
|Speculation is difficult since there is virtually no way to determine a good phylogenic tree for fungi.|
Why is that? Molecular markers are not reliable?
Well, maybe. This is a sample of what I mean:
|Integrating molecular and morphological data in the systematics of fungi|
Department of Mycology, Estonian Agricultural University, Tartu, Estonia
The use of molecular characters in addition to morphological ones, and the use of cladistic methods has remarkably changed our knowledge on the phylogeny of fungi. A single classification, common for all users, which is based on all available data ought to be coined. Classifications using molecular characters (sequencing data a.o.) are in several cases congruent with the present system (of mainly genera). In other cases, due to the widespread parallelism in changes of morphological character states, the new phylogeny hypotheses are different from the classification in current use. In these cases, the main conclusion drawn from the contradiction of molecular and morphological data is that we have to re-evaluate the usefulness of the characters we used. But there are also cases when cladistic analyses based on molecular and morphological characters are giving extremely different topologies of phylogenetic trees. One of the examples is the system of Hymenochaetales (Basidiomycota, Hymenomycetes): if the tree based on rDNA LSU sequence data is accepted, there are almost no synapomorphic morphological characters supporting the branching pattern.
Molecular data taken from the GenBank used for a phylogenetic analysis are in many cases erroneous, mainly due to misidentifications. When only one or some representative species are used to characterize presumably monophyletic genera, the topology of the resulting tree depends on the selection of the species. The number of species included in a study is usually relatively small, causing sampling errors; when additional taxa and species of closely related genera are included, the resulting tree topology is changing. Many studies have been published where no attempts have been made to use combined datasets or to compare molecular data based trees with the morphology-based ones. Studies where changes of morphological characters are mapped on trees obtained using sequence data are surprisingly rare.
Shortly: phylogenetic studies of fungi based on molecular characters are extremely fruitful, but we are only halfway in compiling more or less stable classifications. Until that, the modern trend of using rankless taxonomy and denoting clades arbitrarily is causing some chaos. The so-called Linnean hierarchy is nothing more – and nothing less – than a way of showing the phylogenetic relations between species or species groups in an easily understandable way. A system of organisms is a way of communication between all biologists, not only among taxonomists themselves.
Now I'm just a user, I don't do any research but when you genetic folks get it all sorted out, I suspect there will still be unhappy people. If morphology doesn't end up being represented in the final product then the product isn't very darn useful for people who are trying to use field guides.
Who said that ev'ry wish would be heard and answered
When wished on the morning star
Somebody thought of that, and someone believed it
Look what it's done so far
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