Linking Specialisation and Stability of Plant ... - OPUS Würzburg

6.2 consequences of climate change 117
quences of asynchronous shifts of specific plants and pollinators
largely depend on the degree of dependence of each species
on the availability of particular mutualists. Since species using
a restricted range of resources are generally thought to be less
flexible in their interactions (see chapter 1), specialist plants
and pollinators are expected to be most vulnerable to phenological
desynchronisation. Following this idea, in chapter 5 we
used data on phenology and interactions of plants and pollinators
along an elevation gradient to evaluate the importance of
phenological synchrony with particular plant species for pollinators
of different degrees of specialisation. Contrary to our
expectation, we found that even locally specialised pollinator
species did not depend on synchrony with the flowering phenology
of particular plants, but were flexible in their use of floral
resources at different altitudes. This result is in agreement
with studies of the temporal dynamics of plant-pollinator networks
which report a high degree of flexibility in the structure
of interactions from year to year due to variation in species’ phenology
and abundance (Alarcon et al., 2008; Burkle & Alarcon,
2011). Thus, although some interactions may be lost through
asynchronous shifts in phenology, even relatively specialised
species seem to be flexible enough to interact with new mutualistic
partners when they become available.
If a species’ response to climate change results in a strongly
maladaptive phenology (e.g. desynchronisation of a plant’s
flowering phase with its only pollinator), the species may be
rescued from extinction by rapid evolution of the traits that
determine its response to environmental cues such as photoperiod
and temperature (Miller-Rushing et al., 2010; Gilman et al.,
2012). In general, such an evolutionary response is possible
if the population is genetically diverse and the selection pressure
sufficiently strong. However, the availability of mutualistic
partners is not the only factor influencing the evolution of
phenology. For plants as well as insects, abiotic factors and
biotic interactions with competitors, predators or herbivores,
parasites and pathogens may affect the optimal timing of flowering
or emergence (Elzinga et al., 2007; Miller-Rushing et al.,
2010). Thus, it remains uncertain whether species that are not
flexible enough to switch to new interaction partners can be
rescued from phenological mismatches by a rapid evolutionary
response.