Link-Perez, Melanie A. , Watson, Linda E. , Hickey, R. James .
Toward a Redefinition of Adiantopsis Fée (Pteridaceae).
Of the five major clades in Pteridaceae, the cheilanthoid ferns (about 20 genera and 400 species) are most obviously characterized by adaptations to xeric habitats. The high degree of convergent adaptive morphology to such habitats has made the taxonomic circumscription of cheilanthoids problematic, and has led to an abundance of polyphyletic genera, notably the large genera Cheilanthes, Doryopteris, and Pellaea. Our morphological and molecular phylogenetic study of Adiantopsis Fée has revealed that this small neotropical cheilanthoid genus (~20-25 species) also is not monophyletic as traditionally circumscribed. Classically, Adiantopsis has been characterized by the combination of echinate spores, golden or golden-red paired ridges (called carinae) on the upper side of axes, and distinct pseudoindusia—a combination of characters that sets Adiantopsis apart from other cheilanthoids. Species with cristate spores (A. dichotoma and A. regularis) are generally placed in Cheilanthes. Preliminary analysis of rbcL data using parsimony indicates that the morphological characteristics often used to distinguish Adiantopsis lead to a circumscription that is overly conservative and excludes several basal members in the clade that are non-carinate and have cristate spores. Additionally, several Cheilanthes species are embedded within the Adiantopsis clade, a placement also supported by morphological similarities. The molecular data indicate that Adiantopsis is monophyletic but only with the inclusion of several Cheilanthes species. The inclusion of non-carinate and cristate-spored species in Adiantopsis provides for a clearly defensible and monophyletic circumscription, although one whose morphological boundaries need clarification. Our results also suggest that secondary radiation into mesic habitats accounts for species diversification, especially within the palmate clade within Adiantopsis.
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1 - Miami University, Department of Botany, Oxford, Ohio, 45056, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2008
Time: 10:45 AM