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Rupert Barneby and his legume legacy

McMahon, Michelle [2], Hufford, Larry [1].

Floral simplification in the Amorpheae (Papilionoideae).

Simplification of the complex papilionoid flower has occurred several times in the history of the Amorpheae (Fabaceae: Papilionoideae). First considered a natural group by Rupert Barneby in his elegant monograph Daleae Imagines, the Amorpheae are further supported to be monophyletic by phylogenetic analysis of nuclear and chloroplast sequence data. Based on extensive outgroup analysis, the ancestor of Amorpheae is inferred to have had a standard papilionoid flower (defined as having five petals in three types, strong distinctions between the blade and claw within petals, and often having fusion between two petals, forming the keel). Within Amorpheae, corolla simplification is manifest as a decrease in the number of petals (Amorpha, Errazurizia rotundata, Parryella and a few daleas), decrease in petal differentiation (Eysenhardtia, Errazurizia, Apoplanesia, Dalea subg. dalea), decrease in petal blade/claw distinction (Amorpha, Eysenhardtia, Errazurizia, and Apoplanesia), and decrease in petal fusion (Eysenhardtia, Errazurizia, Apoplanesia, Dalea subg. dalea, a few marinas). Most of these characters demonstrate homoplasy when compared to the phylogeny. Ontogenetic data from selected species show further a lack of homology between flowers with similar character states. For example, petals are completely suppressed in Parryella filifolia whereas petals are initiated and then aborted in Amorpha spp. The various changes toward simplified flowers in Amorpheae may indicate an evolutionary release of constraint, especially when compared to the relatively conserved floral form seen in the rest of Papilionoideae. Other exceptions to the standard form are few and phylogenetically scattered. Although the cause of these changes remains unclear, comparing Amorpheae to other exceptional papilionoids may elucidate correlates of evolutionary simplification.

1 - Washington State University, School of Biological Sciences, P.O. Box 644236, Pullman, Washington, 99164-4236
2 - Univeristy of California, Evolution and Ecology, One Shields Ave, Davis, California, 95616, USA

floral evolution
flower development

Presentation Type: Symposium
Session: 19-7
Location: Magpie (Cliff Lodge)
Date: Monday, August 2nd, 2004
Time: 3:45 PM
Abstract ID:818

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