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Abstract Detail

Systematics Section / ASPT

Simoes, Andre O. [1], Endress, Mary [1], Quast, Monica P. [1], Conti, Elena [1].

Molecular phylogenetics and character evolution of Tabernaemontaneae, a pantropical tribe of Apocynaceae.

TABERNAEMONTANEAE is one of the largest tribes of Apocynaceae s. str., and includes 16 genera and about 175 species distributed throughout the tropics. To test the monophyly of the tribe, a Bayesian analysis was conducted based on DNA sequences from five plastid DNA markers. In addition, the obtained phylogeny was used to test hypotheses of floral and fruit evolution in the tribe. For this, ancestral character states were reconstructed for three discrete, binary characters (guide rails on the anthers, morphological and functional differentiation of the style-head and seeds surrounded by an aril) using a likelihood approach, and a correlation test was performed for the first two. Our results strongly support the monophyly of Tabernaemontaneae, corroborating the most recent classification of the tribe. Within the tribe, two major clades can be distinguished: 1) the Ambelanieae clade, formed by a small group of six genera with indehiscent fruits restricted to northern South America; and 2) the Tabernaemontaneae s.str. clade, formed by a large pantropical group of nine genera with dehiscent fruits. Ancestral state reconstruction suggests that the most recent ancestor of the tribe had anthers with lignified guide rails and a differentiated style-head, with three to four subsequent reversals to anthers without guide rails and a non-differentiated style-head. Our tests supported the correlated evolution of these two characters, but the temporal order of evolutionary change could not be unambiguously determined. Seeds surrounded by an aril were reconstructed as the most likely state for the ancestor of the Tabernaemontaneae s.str. clade. The occurrence of arillate seeds in all sampled species from this clade suggests that this trait may represent a key innovation, leading to species diversification by opening a new niche for a broad array of seed dispersers.

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1 - Universität Zürich, Institut für Systematische Botanik, Zollikerstrasse 107, Zürich, CH-8008, Schweiz

ancestral state reconstruction
character correlation.

Presentation Type: Oral Paper:Papers for Sections
Session: 62-10
Location: 106/Ayres
Date: Wednesday, August 2nd, 2006
Time: 10:45 AM
Abstract ID:129

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