INVESTIGADORES
REINHEIMER Renata
congresos y reuniones científicas
Título:
Inflorescence diversification of the PCK Clade (Poaceae: Panicoideae: Paniceae) and new insight about its phylogeny
Autor/es:
REINHEIMER RENATA; ZULOAGA FERNANDO; VEGETTI ABELARDO C.; POZNER RAÚL
Lugar:
Chicago
Reunión:
Congreso; Botany and Plant Biology 2007; 2007
Resumen:
The PCK Clade,
represented by at least six genera (Brachiaria, Urochloa, Eriochloa,
Megathyrsus, Melinis and Chaetium), is a strong monophyletic group within the
Paniceae tribe (Poaceae). Despite the effort made by many authors, the internal
resolution of this group remains poorly solved. To better understand of the
phylogeny of PCK clade, we analyzed the structure and development of the
inflorescence, spikelet and floret of that group, to determine morphological
homologies and find new characters to combine with molecular data previously
published into an integrated phylogenetic analysis. The most important results
are: (1) twenty-one adult inflorescence types were identified, (2) an extensive
variation of branch system and spikelet development pattern was found (some of
them new for Paniceae and even for the grass family), (3) nine different floral
developmental patterns were described and, (4) some results support the
possibility of more than one sexual expression pattern. The phylogenetic
analysis combining previously published molecular data and our results on
inflorescence morphology and development, showed that Brachiaria s.s and
Melinis are the Basal Clade, while Urochloa is paraphyletic and associated with
Megathyrsus and Eriochloa. Nevertheless, the phylogeny of the PCK Clade remains
unsolved. The lack of a phylogenetic signal and the weak resolution of
evolutionary relationship among species may be interpreted as a signal of
explosive speciation or rapid radiation. Evidences for this hypothesis are: (1)
coincidence in the lack of internal resolution and politomies in the consensus
trees presented until today, (2) weakness of characters used, alone or combined,
to understand the entire history of the group, (3) the wide morphological
diversity among species in terms of inflorescence structure and development.