Systematics Section / ASPT
Wood, Troy E. , Rieseberg, Loren H. .
The Nature of Plant Species.
Many botanists doubt the reality of plant species, suggesting that they are often arbitrary divisions in more or less continuous "morphospace." Zoologists, on the other hand, have chastised botanists for being hung up on a few, atypical "horror stories," e.g. agamic complexes and hybrid swarms that exhibit highly complex patterns of phenotypic variation. They maintain that, in general, plants, like animals, can be grouped into natural and discrete units. Unfortunately, neither side has addressed this problem with an empirically rigorous methodology. We compiled the results of over 200 numerical taxonomic studies that compared patterns of phenotypic variation within and among closely related plant and animal species. The proportion of species taxa that correspond to distinct phenotypic clusters was not significantly different between plants and animals (plants = 53.7 %; animals = 58.7 %, p=0.73). As expected, polyploidy and asexual reproduction have a significantly negative effect on percent correspondence in plants, and when these factors are removed, correspondence is increased to 68.2 %. In contrast, hybridization alone has no effect on percent correspondence. It also has been suggested that botanical species rarely reflect reproductive communities. We find that for 80.7 % of seed plants and 89.6% of ferns and allies in our data set, intraspecific crossability is markedly higher than interspecific crossability, a result significantly greater than that for animals (54.3%). Traditionally, plant species have been viewed as taxonomically more difficult than animal species. Both the phenetic and crossability data sets yield conclusions that are at variance with this prevailing notion.
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1 - Indiana University, Department of Biology, Jordan Hall, 1001 East Third Street, Bloomington, Indiana, 47405, USA
Presentation Type: Oral Paper
Date: Tuesday, August 16th, 2005
Time: 2:00 PM