New Zealand Journal of Botany abstracts
Godley Review
Progress in understanding pollination systems in New Zealand
Linda Newstrom
Landcare Research
P.O. Box 69
Lincoln 8152, New Zealand
Alastair Robertson
Ecology Group
Institute of Natural Resources
Massey University
Private Bag 11222
Palmerston North, New Zealand
Abstract Pollination in New Zealand, an isolated
oceanic archipelago in the Southern Hemisphere, has previously been
characterised as having low rates of self-incompatibility and a lack of
specialised pollination, as well as little pollinator dependence. These
features have been interpreted as supportive of “Baker’s Rule”, which
suggests that long-distance colonisation selects for breeding systems
that do not require biparental mating. However, we show that recent
studies of the angiosperm flora reveal sexual systems (sexual
dimorphism, self-incompatibility, monoecy, dichogamy, and herkogamy)
that usually involve a dependence on pollen vectors. The level of
self-incompatibility in the flora, though still poorly known, should be
regarded as moderate rather than unusually low (about 36% of
hermaphrodite populations tested are strongly or partially
self-incompatible), though many more species remain to be tested. As
found elsewhere, incompatibility is higher in the trees and shrubs
(around 80%) compared with herbs (21%). Moreover, high rates of
autonomous selfing have been demonstrated empirically in only 21% of
the self-compatible species, demonstrating that they are not regular
selfers. The pollinator dependence that these features impose makes
much of the flora vulnerable to declines in pollinator service.
Pollination systems in New Zealand have been characterised as
unspecialised, imprecise entomophilous systems that correspond to the
predominance of small white or pale flowers with dish or bowl shapes.
We use a two-tiered conceptual framework incorporating a coarse-scale
blossom class analysis and a finer scale syndrome concept analysis to
assess the level of specialisation in plant-pollinator relationships of
New Zealand. Within each of the syndromes is a continuum of blossom
classes: open-, directed-, and closed-access. Highly specialised
systems are found in closed-access blossoms but they are not common in
New Zealand (e.g., Solanum, Carmichaelia, orchids, and
mistletoes). Large directed-access blossoms are primarily associated
with bird pollination but certain small entomophilous blossoms, called
knob blossoms (Pseudopanax, Geniostoma), are also
important for perching birds and may be considered ornithophilous. Bats
and lizards play a minor role in pollination. Moth pollination is not
well studied and may reveal cryptic specialisation based on scent. The
majority of pollination systems in New Zealand correspond to the small
bee syndrome, which is a generalised bee-pollinated system common
elsewhere and includes visits from flies and other diverse insects.
Naturalised exotic bees may have both positive and negative effects on
indigenous pollination systems and could play a significant role in
invasive mutualisms in which some weeds are specialised to their
services. Future research in New Zealand pollination and breeding
systems needs to focus on endangered mutualisms, particularly in birds;
on invasive mutualisms, particularly for offshore islands; and on
community analyses that evaluate exotic-indigenous interactions and the
potential for specialisation in the poorly known insect pollination
systems.
Keywords autonomous selfing; blossom class;
community analyses; functional pollinator group; breeding system; New
Zealand; pollen limitation; pollination syndrome; pollinator
dependence; pollinator; self-compatibility; sexual system
B04046; Received 24 November 2004; accepted 8 February 2005, online
publication date 17 March 2005.
New Zealand Journal of Botany, 2005,
Vol. 43: 1–59
0028–825X/05/4301–0001 © The Royal Society of New Zealand 2005
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