Dear Diana, I am a professional taxonomist, however I work with crustaceans not plants. In zoology, the genus concept has become formally defined as a group of species where hybridization is possible: i.e., a zygote can be formed regardless of whether the parents are actually capable of mating. In my crustaceans, genera are defined by the basic form of the male and female genitalia; characters that are highly conserved in evolution because they are governed mostly by sexual selection. If the animals cannot reproduce, there are no genes to be passed on. At the species level, the crustaceans that I study are separated based on the form of the male second antennae, which are used to amplex the female prior to copulation. Again, these characters are primarily formed through sexual selection. What it often comes down to is that species are typically defined by what the animal recognizes as a potential mate. When I (or any taxonomist) finds what I think is a new species, I write up a paper describing it, deposit type specimens at one or more international museums, and submit the paper to a scientific journal. At the journal, the paper is sent to three or more independent reviewers, (hopefully) people who also are familiar with the taxonomic group that the new species is in. These reviewers may have many questions or comments, or may wish to examine the material that I deposited in the museums before reviewing my paper. After review and edits, if the paper is good, it is published, and the new taxon is valid. I am often amazed at botanical taxonomy. There do not appear to be any quantitative definitions for most taxa. So many species defined by such small and often qualitative characters. If hybridizability were a criterion for plant genera, then nearly all of the thousands of orchids would be in one mega-genus! Conversely, polyploidy (extra sets of genes) often causes plants to be unable to hybridize, so then how could two morphologically identical plants, one a polyploid, be separate genera? I hope this in some way is helpful, Christopher D. Christopher Rogers Invertebrate Ecologist/Taxonomist ((,///////////=====< EcoAnalysts, Inc. (530) 406-1178 166 Buckeye Street Woodland CA 95695 USA ? Invertebrate Taxonomy ? Invertebrate Ecological Studies ? Bioassessment and Study Design ? Endangered Invertebrate Species ? Zooplankton ? Periphyton/ Phytoplankton Moscow, ID ? Bozeman, MT ? Woodland, CA ? Neosho, MO ? Selinsgrove, PA http://www.ecoanalysts.com/ -----Original Message----- From: pbs-bounces@lists.ibiblio.org [mailto:pbs-bounces@lists.ibiblio.org]On Behalf Of Diane Whitehead Sent: Sunday, October 22, 2006 10:32 AM To: Pacific Bulb Society Subject: [pbs] how many differences for a species? I have heard it said that a different colour should not mean a new species. OK, that makes sense. However, upon reading descriptions of several species of Hesperantha, I wonder how many differences are required for a different species. Here are a couple of examples of species with several differences. Hesperantha falcata is either white, scented, evening-flowering or yellow, unscented, midday flowering. Hesperantha pilosa is either white, scented, evening-flowering or blue to purple, unscented, day-flowering. Has anyone grown both kinds of either of these, and would you have thought they were the same species if the labels didn't say so? Diane Whitehead _______________________________________________ pbs mailing list pbs@lists.ibiblio.org http://www.pacificbulbsociety.org/list.php