Biology Reference
In-Depth Information
the ancestral pollination system of the first colonizers because the nectar
does not reward current pollinators (Bernardello et al., 2000, 2002). For in-
stance, the ancestors of
Pernettya rigida
(Ericaceae) seem to have been
insect-pollinated, but today this cryptically dioecious species is wind-
pollinated and continues to secrete nectar (Anderson et al., 2000a). Similarly,
Wahlenbergia
(Campanulaceae) colonizers are supposed to have been ento-
mophilous, although extant taxa are mostly selfers, with a wind-aided
pollination mechanism in
Wahlenbergia
berteroi
(Anderson et al., 2000b). A
similar situation was reported for
Iris versicolor
in Kent Island, New Bruns-
wick (Zink & Wheelwright, 1997). In another island system, the Hawaiian
Archipelago, shifts in
Schiedea
species (Caryophyllaceae) from biotic—
pollination or autogamy to wind pollination and sexual dimorphism have
been reported (Weller et al., 1998). There, some sexually dimorphic species,
which occur in dry habitats, are wind-pollinated, yet show some nectar pro-
duction from comparatively reduced nectaries (Weller et al., 1998).
Despite these conclusions, Bernardello et al. (2000, 2002) have proposed
that the presence of nectar rewards does not necessarily indicate biotic polli-
nation on oceanic islands: studies of reproductive biology need to be care-
fully done, species by species, before useful generalizations can be made.
3.8
Distribution of nectary types
Although the location of nectaries in flowers is more or less constant within
lower order groups such as genera and families, nectary type and location are
highly variable in the higher taxonomic groupings of orders and superorders
(e.g., Brown, 1938; Fahn, 1979; Cronquist, 1981; Smets, 1986, 1988; Smets
& Cressens, 1988; Smets et al., 2000) and our knowledge of their distribu-
tion and structure in these higher groups is incomplete (Vogel, 1997).
A survey of the distribution of strictly floral nectaries in an evolutionary
context, based on the available literature, is presented here, starting on
page 56. For this purpose, the updated classification of the families of flow-
ering plants by the Angiosperm Phylogeny Group (APG II, 2003) is
followed, particularly the broader monophyletic family circumscriptions fa-
voured therein (e.g., Alliaceae includes Agapanthaceae and Amaryllidaceae,
Buxaceae includes Didymelaceae, etc.). The unplaced families are mentioned
first, followed by the orders accepted for each clade. The orders are treated
as they are in APG II, and the families are listed alphabetically within each
order; to aid identification, these taxa are written in bold face the first time
they are mentioned. It has to be remembered that this survey is based on
available information, which is generally supported by limited publications
