DOI: 10.5061/dryad.7bc88
title: Data from: Nectar sugar composition of European Caryophylloideae (Caryophyllaceae) in relation to flower length, pollination biology and phylogeny

description: Floral nectar composition has been explained as an adaptation to factors
 that are either directly or indirectly related to pollinator attraction.
 However, it is often unclear whether the sugar composition is a direct
 adaptation to pollinator preferences. Firstly, the lower osmolality of
 sucrose solutions means that they evaporate more rapidly than hexose
 solutions, which might be one reason why sucrose-rich nectar is typically
 found in flowers with long tubes (adapted to long-tongued pollinators),
 where it is better protected from evaporation than in open or short-tubed
 flowers. Secondly, it can be assumed that temperature-dependent
 evaporation is generally lower during the night than during the day so
 that selection pressure to secrete nectar with high osmolality (i.e.
 hexose-rich solutions) is relaxed for night-active flowers pollinated at
 night. Thirdly, the breeding system may affect selection pressure on
 nectar traits; that is, for pollinator-independent, self-pollinated
 plants, a lower selective pressure on nectar traits can be assumed,
 leading to a higher variability of nectar sugar composition independent of
 pollinator preferences, nectar accessibility and nectar protection. To
 analyse the relations between flower tube length, day vs. night
 pollination and self-pollination, the nectar sugar composition was
 investigated in 78 European Caryophylloideae (Caryophyllaceae) with
 different pollination modes (diurnal, nocturnal, self-pollination) using
 high-performance liquid chromatography (HPLC). All Caryophylleae species
 (Dianthus and relatives) were found to have nectar with more than 50%
 sucrose, whereas the sugar composition of Sileneae species (Silene and
 relatives) ranged from 0% to 98.2%. In the genus Silene, a clear
 dichotomous distribution of sucrose- and hexose-dominant nectars is
 evident. We found a positive correlation between the flower tube length
 and sucrose content in Caryophylloideae, particularly in day-flowering
 species, using both conventional analyses and phylogenetically independent
 contrasts.
description: Nexus file of
 CaryophylloideaeNexus file of the
 phylogenetic relationships among the investigated Caryophylloideae. Our
 analyses were based on an unresolved phylogeny constructed using published
 molecular phylogenies and taxonomic groupings. The file was used in
 MESQUITE for further analyses.Caryophylloideae-nexus.nexFigure 1 - model (as MS powerpoint file)Figure 1. Factors that might affect evaporation of water from nectar. (A) Flower nectar depth (nectar is hidden in long-tubed flowers), (B) hydrolyis of sucrose by invertase into hexoses (increase in osmolality), (C) Relation between activity time of flowers (diurnal vs. nocturnal) and temperature (higher during the day) and humidity (higher during the night), (D) features of the anthophore (an elongated internodium above the calyx found in some Caryophylloideae) like its length and hairs. Note: While for hypotheses (A) and (B) evidence can be found in the literature (see text), (C & D) has been tested in this study.Figure 1 - model.pptxFigure 2 - flower morphology (as Ms powerpoint file)Figure 2. Floral features in Silene: A. Half-drawing of a hypothetical female Silene flower (with sterile anthers and nectar along the anthophore) illustrating where nectar is located and how flower structure (here the protruding corona scales) may affect the functional flower length for flower visiting insects. B. Silene colorata; showing how the petal claws and corona scales may increase the functional flower length. C. Anthophore of Silene dichotoma with nectar.Figure 2 - flower morphology.pptxFigure 3 - phylogeny (CorelDRAW file)Figure 3. Phylogenetic distribution of nectar sugar composition, flower tube length and pollination modes in 78 Caryophylloideae. Nectar sugar composition according to the classification system of Baker & Baker (1983); Flower tube length data (gray box; according to Jürgens (2006) and this study. Pollination modes: blue = day-flowering, black = night-flowering, white = self-pollination.Figure 3 - phylogeny.cdrFigure 4 - correlation (MS powerpoint file)Figure 4. Correlation between functional flower tube length [mm], as the distance from the bottom of the calyx to the end of the calyx tube, or the petal claws, or the corona scales (which ever is extending functional tube length the most), and median amount of sucrose (%) in 78 Caryophylloideae in relation to pollination system (A), and phylogeny (B) (Spearman (all species) rS = 0.542, p &lt; 0.05; Spearman (nocturnal) rS = 0.39, p &lt; 0.05; Spearman (diurnal) rS = 0.84, p &lt; 0.05); Spearman (self-pollinated) rS = 0.31, ns). Dianthus glacialis 1* (mainly selfing), data from Erhardt & Jäggi (1995); Dianthus gratianopolitanus 2* (intermediate between butterfly and moth pollination), data from Erhardt (1990).Figure 4 - correlation.pptxAppendix 1-6Appendix 1: Origin of plants sampled for analysis of nectar sugar composition. Vouchers have been deposited in the herbaria of the Universities of Ulm and/or Bayreuth. Appendix 2 (Data from Jürgens et al., 2002). Pollination mode of Dianthus, Saponaria, Vaccaria, Agrostemma and Silene species based on information from the literature. Appendix 3 (Data from Witt, 2003). Average reproductive success of bagged hermaphrodite flowers of 66 Caryophylloideae species sorted by fruit set, seed set per fruit, and seed set of all bagged flowers. Appendix 4. Flower tube length, anthophore length, hair length and hair density on anthophores of 78 Caryophylloideae. Appendix 5 – SEM of the anthophore region of selected Caryophylloideae. Appendix 6. Species of which a few samples contained traces of possibly other sugars in addition to the main nectar sugars (sucrose, glucose, fructose). Reference list for Appendix.