Systematics Section / ASPT
Allphin, Loreen , Windham, Michael D. .
Will the real Boechera perennans please stand up?: New evidence of morphological convergence through reticulation in the genus Boechera (Brassicaceae).
Molecular studies of the primarily North American genus Boechera suggest that it has undergone a rapid evolutionary radiation. Within the last two million years, divergent speciation has produced at least 71 morphologically distinct, sexual diploids. However, reproductive isolation has not kept pace with morphological divergence, and most diploids hybridize when they come into contact. These hybridization events have given rise to a diverse array of facultatively apomictic diploids and obligately apomictic triploids, which can obscure the morphological distinctions among even the most divergent sexual diploids. Now, to add to the confusion, we find that these interspecific hybrids occasionally resemble a third, unrelated sexual diploid more than they do their actual parents. Here we report the results of recent work on the long-lived perennial Boechera perennans. This species has been reported from much of the western United States, ranging as far north as Wyoming. Our analyses reveal that true B. perennans (a sexual diploid) has a much narrower distribution, occurring primarily in the southern portions of New Mexico, Arizona, Nevada, and California. We have found that the more northern populations of “B. perennans” are apomictic triploids of hybrid origin. However, despite their morphological similarity to B. perennans, these triploid populations are unrelated to that species. Isozyme studies reveal that they are, instead, hybrids between B. pallidifolia and B. fendleri. These taxa are morphologically quite distinct from B. perennans and show no genetic affinity to it. Thus, we have documented a clear case of morphological convergence through reticulate evolution.
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1 - Brigham Young University, Department of Plant and Animal Sciences, 275 Widtsoe Building, Provo, UT, 84602, USA
2 - Duke University, Department of Biology, Durham, NC, 27708, USA
Presentation Type: Oral Paper:Papers for Sections
Location: Boulevard C/Hilton
Date: Wednesday, July 11th, 2007
Time: 12:00 PM