Pattern of flower size variation along an altitudinal gradient differs between Impatiens textori and Impatiens noli-tangere

Abstract

Studies of factors influencing spatial variation in flower size offer insights into floral evolution. We investigated altitudinal variations in five flower dimensions of two native Japanese Impatiens species (I. textori and I. noli-tangere) and their interactions with their faunal visitors. These two species have similar floral traits, including flower shape, flowering time, and pollinator species; both species are pollinated mainly by Bombus diversus. In I. textori, all measured flower dimensions were negatively correlated with altitude. In contrast, in I. noli-tangere, no measured flower dimensions correlated with altitude. Thus, the altitudinal pattern of flower size variation differed between these congeneric co-habiting herbaceous plant species. The different patterns suggest that the factors (e.g. altitudinal variations of abiotic factors) that cause variation of flower size differ between these two Impatiens species even though focal species have similar floral traits (e.g. flower shape, flowering time, and pollinator species).ARTICLE HISTORY

Intraspecific morphological variation ofBellidiastrum michelii(Asteraceae) along a 1,155 m elevation gradient in the Tatra Mountains

“…Summary of the GAMs are presented in Table 3. Full-size DOI: 10.7717/peerj.11286/fig- 3 2001; Zhao & Wang, 2015;Hattori et al, 2016). Reductions in flower size and mass with increasing elevation can be linked to the more limiting conditions caused by increases in climate severity at high altitudes.…”

“…Moreover, flowers, which are organs that are relatively invariant within species, have been found to vary quantitatively in plants of the same species across mountain elevation gradients (Herrera, 2005;Maad, Armbruster & Fenster, 2013;Seguí et al, 2018). Intraspecific flower size can gradually increase (Kudo & Molau, 1999;Herrera, 2005;Maad, Armbruster & Fenster, 2013;He et al, 2017) or steadily decrease (Totland, 2001;Zhao & Wang, 2015;Hattori et al, 2016) with increasing elevation. Increased intraspecific flower size at high elevations, as observed in some entomophilous species, has been explained by pollinator selection for larger flowers at high elevations.…”

Striking between-population floral divergences in a habitat specialized plant

“…Most floral traits were significantly positively correlated with each other in both I. lawii and I. oppositifolia and in all three experiments (Wild, Transplant and Germination experiments) (S3 Fig) . The overall width of the flower (FW) described the broadest measure of the flower, contributed mainly by the width of the two largest and most conspicuous wing petals which presumably are most important in attracting pollinators [56,57]. FW consistently showed significant positive correlations with all other floral characters in both species, and we use FW to represent flower size variation across plateaus.…”

The relative importance of diurnal and nocturnal pollinators of Platanthera hologlottis Maxim. (Orchidaceae)

“…In some situations, flowers are visited by different pollinator insects, and the specific species of pollinators change not only among populations (Nagano et al 2014;Kuriya et al 2015;Hattori et al 2016) but also within a population (Wolff et al 2003;Cordeiro et al 2016;Funamoto and Ohashi 2017). For example, Isertia laevis (Rubiaceae) is pollinated mainly by hummingbirds (Trochilidae) during the day and by hawk moths at night.…”