Data from: Nectar sugar composition of European Caryophylloideae (Caryophyllaceae) in relation to flower length, pollination biology and phylogeny

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.