Abstract Detail



Systematics

Burke, Sean [1], Duvall, M [2].

Ancestral State Reconstruction, Divergence Date Estimation, and Trait Evolution in Panicoideae (Poaceae).

Within the grass family (Poaceae) the second largest subfamily, Panicoideae, contains over 200 genera and 3300 species. While mainly warm open habitat grasses, panicoids display a wide array of traits in the extant species. These panicoid traits, such as leaf and floral morphologies, leaf anatomy, and photosynthetic/biochemical pathways, which evolved within the subfamily, arose independently in other grass subfamilies. Thus the diversity found within Panicoideae can explain the diversity throughout the rest of the PACMAD clade, if panicoids are assumed to be sister to the rest of the PACMAD grasses. The evolution of these traits within the subfamily were analyzed within the context of evolution of the whole grass family.
This study investigates the transitions of characteristics of the Panicoideae by analyzing the largest plastome phylogeny to date. The phylogeny was produced from an alignment with 74522 sites representing 352 Poaceae plastomes, with 199 panicoid species. Characteristics were found for the 352 species, representing photosynthetic pathways, kranz anatomy, biochemical subtypes, stigma and stamen numbers, presence or absence of pseudopetioles, as well as light regime. Ancestral state reconstruction using the phytools package in R was used to determine the probable character states for lineages within Panicoideae. This was then paired with divergence date estimations using BEAST2 to determine when these ancestral panicoids arose in the evolutionary timeline.
The Panicoideae demonstrate multiple transitions to other adaptable states when compared against other Poaceae subfamilies. Panicoideae contained at least 14 transitions from C3 to C4 photosynthesis. These transitions to the C4 state includes both types of Kranz anatomy, XyMS- and XyMS+, and all three corresponding biochemical types: PCK, NADP-ME and NAD-ME. There was little variation for the number of stigmas, but there was an estimated nine transitions from three anthers to other variations in stamen numbers. The eight transitions to pseudopetioles were unevenly distributed among Panicoideae with the largest group occurring in Boivinellinae. The diversity displayed in extant panicoid grasses demonstrates their ability to adapt and radiate within a time span with estimates placing the divergence of the subfamily approximately 33 - 53 Ma.


1 - Northern Illinois University, Biological Sciences, 1425 W. Lincoln Hwy, DeKalb, IL, 60115, United States
2 - Northern Illinois University, Plant Molecular And Bioinformatics Center And Department Of Biology, 1425 W Lincoln Hwy, Dekalb, IL, 60115, United States

Keywords:
Grasses
Poaceae
Panicoideae
Ancestral character estimation
C4 Photosynthesis
morphology
anatomy
divergence time.

Presentation Type: Oral Paper
Number:
Abstract ID:463
Candidate for Awards:None


Copyright © 2000-2018, Botanical Society of America. All rights reserved