Mocko, Kerri , Jones, Cynthia .
Stomatal behavior and integration of functional traits are consistent with climate of origin for co-occurring congeners.
While isohydric and anisohydric behaviors have been described in many systems, so far little work has been done linking these strategies to traits or evolutionary history. In other words, can functional traits tell us how stomata behave, and to what extent do co-occurring congeners from different lineages differ in their stomatal responses? To answer these questions, we measured stomatal conductance, photosynthetic rate and predawn water potential of Pelargonium species from the two major clades at sites where they co-occur across South Africa throughout the growing season. We also measured leaf traits such as LMA, leaf longevity, and carbon and nitrogen isotopes. The two major clades in Pelargonium, clades A and C, have contrasting evolutionary histories that we found are reflected in their physiology at sites where they presently co-occur; species displayed a continuous range of isohydric and anisohydric behaviors but clade-specific patterns emerged. Clade A species exhibited far less stomatal control (more anisohydric) than clade C species, irrespective of site. Evolution in clade C species began when South Africa was experiencing a mesic-subtropical climate, while clade A species diversified during a period of increasing aridity and seasonality in the winter rainfall region. Under winter growing conditions, when conditions are cool and wet and evaporative demand is low, the evolution of anisohydry in clade A promotes rapid carbon gain during a short growing season followed by dormancy during a hot, dry summer. In contrast, with warm temperatures, high insolation and therefore high evaporative demand during the growing season, isohydric clade C species preserve leaf function by closing stomata to maintain plant water status. Furthermore, while physiology reflects adaptations to historical climates, variation in leaf traits such as LMA may reflect the integration of leaf longevity and photosynthetic capacity with drought strategy. Our study is unique in that it investigates isohydry and anisohydry in an ecological and evolutionary context by assessing the relationship between plant function and leaf structure over the course of a growing season in many co-occurring congeners.
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1 - University Of Connecticut, Ecology And Evolutionary Biology, U-3043, 75 N. Eagleville Rd, Storrs, CT, 06269, USA
2 - University Of Connecticut, Department Of Ecology & Evolutionary Biology, 48 Echo Rd., Mansfield Ct., CT, 06250, USA
functional leaf traits
Presentation Type: Oral Paper:Papers for Topics
Location: Salon 16/The Shaw Conference Centre
Date: Tuesday, July 28th, 2015
Time: 10:45 AM
Candidate for Awards:Physiological Section Physiological Section Li-COR Prize