IBODA   05360
INSTITUTO DE BOTANICA DARWINION
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Inflorescence diversification of the PCK Clade (Poaceae: Panicoideae: Paniceae) and new insight about its phylogeny
Autor/es:
REINHEIMER, R; ZULOAGA, F.; VEGETTI, A.; POZNER, R.
Lugar:
Chicago, Illinois
Reunión:
Congreso; Plant Biology & Botany 2007 Conference; 2007
Institución organizadora:
Botanical Society of America
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.