Natural Variation in Flower Color and Scent in Populations of Eruca sativa (Brassicaceae) Affects Pollination Behavior of Honey Bees

Abstract

Plants of Eruca sativa Mill. (Brassicaceae) from desert and Mediterranean populations in Israel differ in flower color and size. In the desert habitat, the population has higher abundance of flowers with cream color and longer petals, whereas in the Mediterranean habitat, the population has higher abundance of flowers with yellow and shorter petals. Choice experiments with honey bee foragers (Apis mellifera Linn., Apidae, Hymenoptera), the main pollinator in the natural habitat in Israel, confirmed that they are more attracted to the yellow flower morph than to the cream one. A proboscis extension response test indicated that honey bees are able to discriminate between flower scents of the desert and Mediterranean populations. Considering the advantage of plants of the yellow morph in attracting pollinators, we further tested in a common garden experiment whether these possess higher fitness than plants of the desert population. Indeed, a significant association was found between flower color and fruit set, and seed mass. In general, our results provide evidence for ecotypic differentiation between populations imposed by pollinators. The advantage of the yellow color morph in attracting pollinators may explain its dominance among plants of the Mediterranean population. We discuss why the cream color morph may be dominant in the desert habitat, considering the possibility of different pollinators, tradeoffs between traits, or pleiotropy.

Phenotypic differentiation and diversifying selection in populations of Eruca sativa along an aridity gradient

“…However, Pau et al [ 41 ] emphasized the relative importance of biotic drivers that change over the growing season to the shaping of phenological traits. Thus, the relative role of plant community structure, herbivore pressure and pollinator availability that differentiate the desert and Mediterranean populations of E. sativa [ 25 , 28 , 31 ] cannot be ruled out. Nevertheless, the differences between flowering duration in the three populations led to almost twice the reproductive biomass (total seed weight per plant) of the arid and semi-arid populations (SA and BS) in comparison to the Mediterranean population.…”

“…In the eastern Mediterranean, populations of E. sativa are distributed along a narrow geographical range from the southern Golan Heights in the north, to the Jordan Valley in the south, across a steep north–south climatic gradient changing from mesic Mediterranean to arid-hot desert conditions [ 20 , 25 ]. We previously showed phenological and phenotypical variations among populations of E. sativa along this aridity gradient [ 25 , 28 – 30 ]. More recently, we also reported on genetic differentiation and additive genetic variance for flowering time plasticity in response to the plant hormone jasmonate in these populations [ 31 ].…”

Phenotypic plasticity guidesMoricandia arvensisdivergence and convergence across the Brassicaceae floral morphospace

“…This niche is even shared by their closest relatives, such as Rytidocarpus moricandioides or Eruca spp. (G omez et al, 2016Barazani et al, 2019;Shakeel et al, 2019), and was reconstructed as the most likely pollination niche of the Moricandia ancestor. However, the summer floral morph of M. arvensis is pollinated by a different set of insects and belongs to a different pollination niche associated with short-tongued small and medium-size bees (G omez et al, 2020).…”

Comparative anatomical and transcriptomic analyses of the color variation of leaves in Aquilaria sinensis

“…In the plant kingdom, color variation has been widely reported in leaf, culm, flower, fruit, seed coat and other tissues derived from different plants ( Ahmed, Hayashi & Yazawa, 2004 ; Barazani et al, 2019 ; Brand et al, 2014 ; Xia et al, 2015 ; Yang et al, 2010 ). Some phenotypes about color variation could be found in the whole tissue while others could show diversified phenotypes such as color stripes or banding mosaic ( Wang et al, 2019 ; Xia et al, 2015 ).…”

“…Accompanied with the changes in appearance, a battery of characteristics in botany or ecology could be different. For example, the flowers of Eruca sativa with different color display diverse attraction for their main pollinator because of the discrimination of the scents in flowers of different colors ( Barazani et al, 2019 ). In Capsicum annuum L., the plant samples differing in leaf color are accompanied with different combinations of pigments which could influence the resistance of these plants against whitefly ( Cheng et al, 2018 ) which is a kind of pest damaging plants seriously ( Ullah & Lim, 2016 ).…”