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Abstract Detail


Dudley, Leah [1], Emms, Simon [2], Hove, Alisa [3], Mazer, Susan [4].

Instantaneous and long-term water use efficiencies in two pairs of Clarkia taxa with contrasting mating systems.

The adaptive significance of variation in plant mating systems has long attracted the attention of evolutionary biologists. The evolution of self-fertilization, for example, has been described as an evolutionary dead-end due to its detrimental genetic effects. In the genus Clarkia (Onagraceae), selfing taxa have diverged from outcrossing taxa numerous times. Selfers are often found near their outcrossing counterpart’s range edge under environmental extremes. In the Sierra Nevada, selfing Clarkia taxa occupy sites that are drier, flower earlier and have shorter life-cycles than their outcrossing counterparts. The selfers’ shorter life-cycles may be a strategy to avoid late-season drought, while the outcrossers, which are typically the last spring wildflowers in the region, must likely tolerate drying soils as summer progresses. Here, we explore two pairs of sister taxa that differ in mating system: the outcrossing C. unguiculata and its selfing sister species, C. exilis (hereafter unguiculata and exilis), and the outcrossing C. xantiana ssp. xantiana and its selfing sister subspecies C. x. ssp parviflora (hereafter xantiana and parviflora). We measured two water-use traits in three populations per taxon in 2010: instantaneous WUE (WUEi) prior to and during flowering and δ13C (long-term WUE estimate) during flowering. If mating system has evolved in response to late season water limitation, then water-use should differ between sister taxa, with outcrossers being relatively efficient with their water-use compared to selfers. Prior to flowering, exilis and unguiculata exhibited similar WUEi, while during flowering exilis exhibited significantly lower WUEi than unguiculata. Parviflora exhibited lower WUEi than xantiana early in the season, while xantiana exhibited lower WUEi than parviflora during flowering. With respect to δ13C, exilis and unguiculata did not differ significantly; however, parviflora exhibited a less negative δ13C (lower WUE) than xantiana. We also aimed to detect the adaptive significance of WUE by estimating fitness associated with variation in WUE. During flowering, at the time of gas-exchange measurements, we estimated individual fitness as the total number of buds, flowers and fruits produced. Linear regressions of fitness on WUE (instantaneous and δ13C analyzed separately) show a stronger, positive relationship for selfers compared to their outcrossing counterparts, indicating a potential selective advantage associated with higher WUE in the selfers. The generally low WUE in the selfers are surprising given the apparent selective advantage. We predicted, however, that selfers should avoid late season drought, so perhaps they exhibit lower WUE than outcrossers because the selfers have greater access to early-season soil moisture

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1 - 7056 Cyrus Canyon Road, PO Box 563, Kernville, CA, 93238, USA
3 - Warren Wilson College, Biology Department, PO Box 9000, Asheville, NC, USA
4 - University of California Santa Barbara, Department of Ecology & Marine Biology, 4119 Life Sciences Building, Santa Barbara, CA, 93106, USA

water-use efficiency
plant mating systems

Presentation Type: Oral Paper:Papers for Topics
Session: 27
Location: Elmwood/Riverside Hilton
Date: Tuesday, July 30th, 2013
Time: 10:15 AM
Number: 27001
Abstract ID:886
Candidate for Awards:None

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