Variation in and adaptive plasticity of flower size and drought-coping traits

Abstract

Although phenotypic plasticity of morphological and physiological traits in response to drought could be adaptive, there have been relatively few tests of plasticity variation or of adaptive plasticity in drought-coping traits across populations with different moisture availabilities. We measured floral size, vegetative size, and physiological traits in four field populations of Leptosiphon androsaceus (Polemoniaceae) that were distributed across a rainfall gradient in California, USA. Measurements were made over 5 years that varied in precipitation. We also conducted a growth chamber experiment in which half-sibs from three populations were divided equally among a well-watered and a drought treatment. We tested for selection on traits in each of the watering treatments, and evaluated whether traits exhibited plasticity. In the field, plant traits exhibited substantial variation across populations and years. Flower size, leaf size, and water-use efficiency (WUE) were generally higher for populations that received greater average rainfall. However, in dry years, we observed a decrease in flower and leaf size, but an increase in WUE across the populations. In the growth chamber experiment, leaf and physiological traits exhibited plasticity, with smaller leaves and higher WUE found in the drought, as compared to the well-watered treatment. Only specific leaf area exhibited differentiation in plasticity among populations. Although there was no observed plasticity in floral size, selection favored smaller flowers in the drought treatment and larger flowers in the well-watered treatment. Our results suggest that moisture availability has led to trait variation in L. androsaceus via a combination of selection and phenotypic plasticity.

Evolutionary and plastic changes in a native annual plant after a historic drought

“…Water loss from flowers may also influence flower size. Work with L. bicolor and the closely related L. androsaceus has demonstrated that flowers of Leptosiphon lose substantial amounts of water, and plants may produce smaller flowers in drier locations or conditions in order to limit that loss (Lambrecht, 2013; Lambrecht, Morrow, & Hussey, 2017). Floral water loss of Leptosiphon and other plant species has been shown to affect leaf physiology and can lead to reduced gas exchange, particularly in dry conditions (Dudley, Arroyo, & Fernandez‐Murillo, 2018; Galen, Sherry, & Carroll, 1999; Lambrecht, 2013).…”

Temperature and water stress affect plant–pollinator interactions in Borago officinalis (Boraginaceae)

“…Flower size reduction was previously reported in response to drought. Carroll et al (2001) observed a reduction of 33% in flower size after 12 days of drought for Epilobium angustifolium, and Lambrecht et al (2017) reported a decrease in flower size of Leptosiphon androsaceus in response to dry years. The high water costs of flowering influence flower morphology (De la Barrera & Nobel, 2004).…”

“…We observed that B. officinalis decreased E i and g s under water stress. A decrease in E i is a common response to water stress; plants close their stomata to limit water loss (Lambrecht, Morrow, & Hussey, 2017;Qaderi et al, 2012). Decreasing g s usually reduces plant photosynthesis (Adejare & Umebese, 2007;Khan et al, 2010).…”

“…Nevertheless, we observed that the net photosynthetic rate was only slightly affected by water stress in our experiment due to an increase in intrinsic WUE. High WUE has been reported as a strategy to increase resource use efficiency in several species (Gomes et al, 2009;Lambrecht et al, 2017;Quinet, Descamps, Coster, Lutts, & Jacquemart, 2015).…”

Bumblebee Behavior on Flowers, but Not Initial Attraction, Is Altered by Short-Term Drought Stress

“…Such responses are not limited to vegetative traits but can also be present in floral traits. For example, a decrease in flower size, in the number of flowers and/or in floral height under drought conditions can reduce transpirational water loss through flowers ( Feild et al, 2009 ; Teixido and Valladares, 2014 ; Lambrecht et al, 2017 ) and can decrease water consumption for flower maintenance ( Galen et al, 1999 ). However, these changes are often species-specific ( Burkle and Runyon, 2016 ; Descamps et al, 2018 , 2020 ; Glenny et al, 2018 ).…”