Abstract Detail

Ecophysiology

Randall, Joshua [1].

Whole Plant Physiological Evolution following the Radiation of the Genus Silphium into Mesic Habitat.

The ability for plant taxa to make rapid ecological transitions has been an area of great concern in recent years. This change is highly reliant on the accessibility of an adjacent ecological space and pre-adapted structures relevant to physiologic constraints of the environment. The genus Silphium saw a rapid expansion of the sub-taxa Silphium coinciding with the movement out of dry habitat, into mesic habitats. The sub-taxa Silphium is differentiated from Composita by its tall sunflower-like growth habit, as opposed to a geophytic structure. In order to investigate the transition between these two groups and to what extent the drought tolerant strategy of the ancestors to the radiation was maintained, species from both taxa were compared using anatomical, physiological, phylogenetic, and biochemical tests. Across these considerations, there were reductions in traits linked to drought tolerance strategies in Silphium compared to Composita with the most recently diverged species representing the least drought tolerant. A gene tree for the NAC family showed recent divergences in several orthologs important for lignin production and transportation in Silphium relative to Helianthus. Silphium was found to have higher stomatal density, thinner xylem walls, leaves with smaller carbon investments, lower embolism resistance, and less cellulose and heavy polysaccharides. These represent selection for tradeoffs between increased hydraulic and photosynthetic machinery and decreased drought tolerance. These findings suggest that many of the pre-adapted features of Silphium were lost prior to the transition to mesic habitat. Whether there are any apomorphic structures or pathways that supported this transition has yet to be shown.

1 - Yale University, Ecology and Evolutionary Biology

Keywords:
leaf economics
phylogenetics
hydraulics
Asteraceae.

Presentation Type: Poster
Session: P2, Ecophysiology Posters
Location: Virtual/Virtual
Date: Tuesday, July 20th, 2021
Time: 5:00 PM(EDT)
Number: P2PE007
Abstract ID:1078
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize