POLLINATORS POLLINATION AND FOOD PRODUCTION

THE ASSESSMENT REPORT ON POLLINATORS, POLLINATION AND FOOD PRODUCTION
also affect pollination patterns, through effects on plants
(e.g., nectar and production), pollinators (access to floral
resources), or both. Phenological mismatches between
plants and pollinators are also likely to become increasingly
common (Thomson, 2010; McKinney et al., 2012).
In a long-term view we also need to consider the
evolutionary future of a world with an altered pollinator
environment (Guimarães et al., 2011). The features of
flowers, their scents and colours, are the result of natural
selection imposed by pollinators. Faced with increasing
pollen limitation, plants may either come under selection to
enhance attractiveness, or alternatively to enhance selfpollination
(Cox, 1991; Fishman and Willis, 2008; Mitchell
and Ashman, 2008; Harder and Aizen, 2010). The latter
trajectory is expected to lead to smaller and less attractive
flowers, as shown experimentally by Bodbyl-Roels and Kelly
(2011). Evidence for such a trend comes from a study of
urban versus rural populations of a Japanese Commelina
species, which display traits that promote self-pollination
only in an urban context (Ushimaru et al., 2014). Animal
traits may also evolve in response to human-induced
changes in the architecture of plant-pollinator interaction
networks. For example, Smith et al. (1995) detected an
evolutionary change in bill size in the Hawaiian honeycreeper
(Vestiaria coccinea) resulting from an apparent dietary shift
caused by dramatic anthropogenic declines and extinctions
of lobelioids, a historically favoured nectar source.
3.7 AGRICULTURAL
POLLINATOR DEPENDENCE
3.7.1 Outline of section
This section reviews the dependence of crops and global
agriculture on animal pollination, trends of increased
pollinator-dependency of agriculture over time, and spatialtemporal
variation among among regions in the world. Also,
it discusses potential uncertainty associated with the use of
FAO data and crop categories of pollinator dependency.
3.7.2 Crop and agriculture
pollinator dependency
Animal pollination is critical for, or enhances the reproduction
of, many cultivated crops. Some estimates have shown
that pollinators (mainly, but not exclusively bees) increase
the productivity of ca. 70% of 1,330 tropical crops (Roubik,
1995), 85% of 264 crops cultivated in Europe (Williams,
1994), and about 70% of the world’s 87 leading crops (Klein
et al., 2007). Given that pollinator dependence for increasing
yield is highly common, there have been breeding programs
to make some crops less dependent on animal pollination.
For instance, inbred, pollinator-independent varieties of
some crops, like tomato (Solanum lycopersicum) have been
artificially selected (Peralta and Spooner, 2007). Also, selfcompatible
cultivars of almond, Prunus amygdalus, have
been developed from crosses between self-incompatible
varieties (e.g., Kodad and Socias I Company, 2008),
whereas gynoecious (i.e. female) lines of parthenocarpic
cucumbers (Cucumis sativus) have been obtained through
controlled crosses between parents carrying this partially
recessive, genetic-based trait (Yan et al., 2008). On the other
hand, many entomophilous crops, like sunflower (Helianthus
annuus) rely on the sowing of commercially-produced hybrid
seed harvested on male-sterile plants, a process for which
insect pollination is absolutely essential (Perez-Prat and van
Lookeren Campagne, 2002). Also, some outcrossing crop
species maintained as populations, such as alfalfa and white
clover, will become increasingly less productive without
abundant and effective pollinators because of increasing
inbreeding depression (Jones and Bingham, 1995). Even
self-compatible crops that have been highly genetically
engineered, like rapeseed (Brassica napus), can be largely
pollinator-dependent (Morandin and Winston, 2005), the
same as largely parthenocarpic crops, like seedless varieties
of Citrus (Chacoff and Aizen, 2007) or triploid seedless
watermelon (Walters, 2005). Because of these opposing
examples, there seems not to be a net trend for agriculture
to become less pollinator-dependent through crop breeding.
Because there is wide variation among crops and varieties
within crops in their degree of pollinator dependency (Klein
et al., 2007), the question that follows is not how dependent
are individual crops, but rather how dependent is global
agriculture on animal pollination. Overall, animal-pollinated
crops represent about one-third of global agricultural
production volume (i.e., metric tons), but because of only
partial pollinator-dependence of those crops (Richards,
2001; Klein et al., 2007), pollinators only account for
5-8% of total production (Aizen et al., 2009). These latter
figures are minimum estimates, however, because they
only consider the direct role of pollinators in producing the
seeds and fruits we consume in terms of weight, but not
(i) the indirect role of pollinators in producing the seeds of
many vegetable or fibre crops we sow (Klein et al., 2007);
(ii) pollinators´ contribution to food quality in terms of the
disproportionate concentration of micronutrients, including
many vitamins, contained in different organs of animalpollinated
plants (Eilers et al., 2011, Delaplane et al., 2013),
particularly in tropical regions (Chaplin-Kramer et al., 2014);
(iii) pollinators´ relevance in the pollination of fodder crops
and pasture (Fairey et al., 1998); (iv) pollinators´ importance
in the production of non-timber forest products (Rehel et al.,
2009); and (v) pollinators´ role in the pollination of medicinal
plants and plant species of traditional use (Joy et al., 2001).
In addition, because of the low yield of many pollinatordependent
crops (compared to non-dependent crops), the
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3. THE STATUS AND TRENDS IN POLLINATORS
AND POLLINATION