TITLE:
Characterization of sugar diversity in floral and extra-floral nectar from the Coastal Coral Tree (Erythrina caffra Thunb.) in Southern California
AUTHORS:
Vіctor D. Carmona-Galindo, Kenny Morales, Renee Maser, Julius Doyle, Mera Gobrial
KEYWORDS:
Chemical Ecology; Diversity Index; Exotic Species biology; Myrmecophyte; Nectar Chemistry
JOURNAL NAME:
Open Journal of Ecology,
Vol.4 No.2,
February
8,
2014
ABSTRACT: The
Coastal Coral Tree (Erythrina caffra Thunb.) produces floral nectar (FN)
that serves to attract pollinating insects, but also secretes nectar from
extra-floral (EFN) glands that serves to attract predatory insects, such as
ants. While studies on myrmecophytes (i.e. specialized plants that attract and interact with ants) have primarily focused
on interspecific evaluations of EFN chemistry, the Coastal Coral tree offers an
opportunity to contrast intraspecific nectar chemistry with differing
evolutionary and ecological functions. We hypothesized that the richness of
(molecular) sugar species, relative concentrations, and diversity of sugars in
FN and foliar EFN would diverge due to differences in the ecological role of
the two types of nectar. High performance liquid chromatography with refractive
index detection was used to identify the richness of sugar species (based on
retention time), measure the relative concentrations, and evaluate the
diversity of sugars in FN and foliar EFN secretions. We detected sugar species
unique to each gland type and reported significant differences in the relative
concentration of one sugar species common to both gland types. While the mean
diversity index of sugars was similar for both gland types, the diversity of foliar
EFN sugars was significantly more variable than that of FN sugars. The
composition of FN showed little variation, and was reflective of its
fundamental role in plant reproduction. Foliar EFN, however, demonstrated the variability expected of a
context-dependent myrmecophyte that interacts with a facultative ant species assemblage
across a mosaic of abiotic and biotic conditions.