Abstract
Analysis of cpDNA matK sequences for a total of 43 members of the succulent plant family Crassulaceae, including 24 taxa of Crassula, recovered a well-supported clade comprising Crassula species that is sister to the remainder of the family. The resulting topologies do not support the monophyly of the currently recognized subgenera of Crassula, as one member of subgenus Disporocarpa (C. crenulata) is placed as sister to an otherwise monophyletic subgenus Crassula. The major synapomorphy that has been used to recognize the latter subgenus is a base chromosome number of x = 7 versus a base of x = 8 in the other subgenus. We cannot assess the utility of this feature for defining subgenus Crassula because a chromosome count of C. crenulata has yet to be published. The five accessions of the recently resurrected segregate genus Tillaea (of 24 total Crassula species) included here were placed in four separate, well-supported lineages, one of which is greatly removed from the other four accessions. This suggests that this genus is not valid and should not be recognized. An initial examination of the evolution of habit indicates that a perennial habit is ancestral and that the annual habit is a feature that has been derived at least twice in the genus.
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Acknowledgments
This research was supported by NSF DEB 0344883 to MEM. The authors wish to thank J.A. Archibald, D.J. Crawford, T. O’Leary, and P. Protti for helpful comments on previous versions of this manuscript. We dedicate this paper to Charles Uhl for his decades of contributions to the study of Crassulaceae.
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Mort, M.E., Randle, C.P., Burgoyne, P. et al. Analyses of cpDNA matK sequence data place Tillaea (Crassulaceae) within Crassula . Plant Syst Evol 283, 211–217 (2009). https://doi.org/10.1007/s00606-009-0227-z
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DOI: https://doi.org/10.1007/s00606-009-0227-z