Inflorescence diversity and evolution in the PCK Clade (Poaceae: Panicoideae: Paniceae)

The PCK Clade, represented by six to nine genera, is a monophyletic group situated within the Paniceae tribe. The highly diverse inflorescences within the PCK Clade provide an interesting system for the study of morphological evolution and also may aid in better understanding its unclear systematics. The inflorescence structure of 110 members of the PCK Clade has been investigated. Inflorescences are polytelic showing different levels of truncation. At least 21 different inflorescence subtypes were identified. Fourteen variable inflorescence characters were found, among which some have suprageneric or infrageneric value and others are polymorphic. A key for the identification of inflorescence types is presented. Nine processes have been identified as responsible for inflorescence diversification. Highly branched inflorescences with different internode lengths are present in the basal genus whereas truncated inflorescence morphologies appear late in the history of the clade. The precise timing of morphological changes is impossible to assess until we have a well supported phylogeny for the PCK Clade.