Complex Transitions between C₃ and C₄ Photosynthesis during the Evolution of Paniceae: A Phylogenetic Case Study Emphasizing the Position of Steinchisma hians (Poaceae), a C₃‐C₄ Intermediate

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The University of Chicago Press is collaborating with JSTOR to digitize, preserve and extend access to International Journal of Plant Sciences.A two-tiered, nested molecular phylogenetic study of panicoid grasses to explore character state transitions between the C 3 and C 4 adaptive syndromes is presented. A broad survey of 92 panicoid species was sampled for the grass-specific insert sequence in the chloroplast RNA polymerase locus (rpoC2), combining published and unpublished sequences. This portion of the study also included an intensive phylogenetic investigation of one clade of seven species that included Steinchisma hians, which is notable for exhibiting intermediacy between the C 3 and C 4 photosynthetic types. Both rpoC2 data and previously published sequences of the F subunit of an NADH-dependent dehydrogenase were analyzed together for this small group. A rigorous phylogenetic investigation of S. hians and 13 other species of Panicoideae included in the broad survey was then performed with sequences of both rpoC2 and the externally transcribed spacer region of the nuclear ribosomal repeat. These 14 species were selected to maximize representation among photosynthetic subtypes. Combined analysis resolved single origins of two photosynthetic subtypes. A reversion of C 4 to C 3 photosynthesis during the evolution of the lineage that includes S. hians is identified. These and other recent results indicate that repeated reversions from C 4 to C 3 have occurred. The C 3 species Panicum laxum has a strongly supported sister group relationship to S. hians (C 3 -C 4 ). The most parsimonious interpretation is that S. hians represents an incipient reversal from C 3 to C 4 photosynthesis, beginning with the capacity to compartmentalize photorespiratory metabolism in the bundle sheath tissue.

Phylogeny of the Grasses (Poaceae) Revisited

“…Sequence determination followed standard methods (Clark et al 1995;Duvall and Morton 1996). GenBank accession numbers for the complete set of sequences analyzed, together with voucher specimen information for newly determined sequences, are provided in Table 2.…”

“…In a recent phylogenetic study of another plastid locus, the rpoC2 insert, Micrairoideae, represented by Eriachne ALISO Duvall, Davis, Clark, Noll, Goldman, and Sánchez-Ken mucronata R. Br., Isachne distichophylla G. C. Munro ex Hillebr., and Pheidochloa gracilis S. T. Blake, were similarly resolved as monophyletic (Duvall et al 2003). The position of Micrairoideae among the PACMAD subclades was unresolved in MP (Fig.…”

“…Molecular phylogenetic relationships within Poaceae have been shown to be influenced by outgroup selection in a smaller study of plastid DNA sequences (Duvall and Morton 1996). Here we explored the effect of outgroup membership on ingroup resolution and support in analyses of a larger molecular matrix.…”

Integrating Phylogeny into Studies of C4 Variation in the Grasses

“…Both the distribution of C 4 grasses in distinct taxonomic groups and the high variability of their C 4 syndrome led to the inference of multiple origins of the C 4 pathway in this family (Sinha and Kellogg, 1996;Kellogg, 2001). Phylogenetic analyses of the subfamily Panicoideae further suggested that C 4 photosynthesis appeared several times independently, although a single appearance followed by multiple reversions could not be excluded (Giussani et al, 2001;Duvall et al, 2003;Vicentini et al, 2008). The ancestral state reconstructions adopted in these studies are strongly dependent on species sampling and rely on statistical methods whose assumptions can produce different results.…”

Phylogenetic analysis and taxonomic position of section Verrucosa of Panicum and its relationship with taxa of the Sacciolepis–Trichanthecium clade (Poaceae: Panicoideae: Paniceae)

“…Phylogenetic studies, based on morphological and molecular characters, have firmly demonstrated that Panicum in its traditional sense is not monophyletic (Gómez-Martínez and Culham 2000;Zuloaga et al 2000;Duvall et al 2001Duvall et al , 2003Giussani et al 2001;Aliscioni et al 2003). These studies allowed new delimitations within the Paniceae, such as the recognition of four genera, previously treated by Zuloaga (1987) at subgeneric level: Dichanthelium (Hitchc.…”