Phenology and pollination Flashcards
Phenology
study of the timing of recurring biological events
e.g. leafing, flowering, fruiting, breeding, migration
changes in palnt and animal phenology are often among the first impacts of climate change
Reproductive phenology
Flowers (pollinators)
->
Fruits (dispersers)
->
Germination and growth
4 general temporal patterns of phenology
Continual
Sub-annual
annual
supra-annual
Why so much variability in phenological patterns?
Abiotic factors (climatic condition)
Biotic factors (interaction with animals, sychrony among plant species, asynchrony among plant species)
Relationship with other phenophases
factors related to duration of pollination, predation etc
Frequency of pollination
see also sildes
Continual flowering
Continuous flowering is not common for individual plants
Continual flowering of populations is more common, most notably in figs, where it is necessary to maintain species specific pollinator populations
See slide for life cycle
the figs produce crops year-round and (in most species) without synchronization between individual trees, this reflects specifity and short life-span of the pollinators
Episodic flowering
episodic but synchronized (population) flowering is the most common phenological pattern
(sub-annual, annual, supra-annual)
resources can be stored and energy can be put in large flowering which attracts more pollinators
they are less dependant on a particular pollinator
synchronization ensures cross-pollination and out-crossing
big fruit crops attract more dispersers
synchronized fruiting might satiate predators
“Big band” strategy
Synchronized flowering, fruiting and death occurring across long supra-annual intervals. In some bamboos the interval is more than 100 years
What might be benefits to the big bang strategy?
Sudden superabundance of food provided by huge seed crops satiates seed predators ensuring that some escape (dispersal)
However, multi-decade intervals are far longer than needed to stop the build-up of seed predator populations
one hypothesis for bamboo is that episodic death encourages fire, which helps germination and survival of seeds / seedlings
for other plant taxa, the flowering event may be powerful enough to attract huge pollinator populations from long distances (in addition to seed predator satiation)
the ultimate big bang “general flowering” in lowland dipterocarp forests
Synchronization of reproduction at the population level is usual in large tropical trees, and supra-annual (> 12 month) cacles are common but..
the dipterocarp-dominated lowland tropical rainforests of TEA show a unique phenomenon called “general flowering”
Synchronized supra-annual flowering at the community level
Intervals of 1-9 years
Typically involves most dipterocarp species, many other canopy trees, and a variety of other plants, including herbs, climbers and epiphytes
There has been a lot of interest in trying to decipher the environmental cues for general flowering
What are cues for mass flowering?
see slide
Drought seems to be correlated to flowering and fruiting
subsequent flowering events are substiantally smaller than the first one
El niño and la niña
occasional, varied alterations to temperature and precipitation
These anomalies are important in an aseasonal environment that may normally lack triggers
el niño is when you typically have a warmer than a normal year, la niña is the opposite
also the same with precipitation, el niño drought conditions, la niña more precipitation
these anomalies have been hypothesized to be triggers of mass flowering in SE Asia
Consequences of general flowering / mass fruiting to animals
rapid populations build-ip during peaks, e.g. flower-feeding thrips (but impossible for vertebrates)
Storing food, e.g. soical bees
Migration, e.g. Apis dorsata, bearded pigs, birds
diet switching e.g. macaques from leaves to fruits, beetles from leaves to flowers etc, common strategy in SE Asia
Specialization on the few species that are always available, such as figs
As a result, flower- fruit and seed-feeding vertebrates appear to have less specialized diets in SE Asian rainforests than their counterparts in African or Neotropical rainforests
movement of organisms
allows the colonization of new areas increasing the likelihood of species persistence. at individual level it decreases risk of density-dependent mortality
Movement of genes
Supports outcrossing, which is beneficial to species vigor
Pollination (gene flow)
Transfer of pollen from the male part (stamen) of a flower to the female part (stigma) of another flower by wind, water or animals
Seed dispersal (immigration, gene flow)
The transport of seeds away from the parent plant to a site suitable for germination and growth, by wind, water or animals
Main pollen and seed dispersal vectors
Wind
Water
Animals
Gravity
Wind pollination
globally ~20% of flowering plants are pollinated by wind but this is rare in tropical forests because:
- low wind-speeds below forest canopy
- low denisty fo tropical tress species
exceptions:
grasslands
Montane (oaks)
Coastal
Animal pollinators provide critical ecosystem services
Animal pollination
~80% of all flowering plants use animal vectors for pollination
Most important: bee species
Other pollinators:
Beetles
Flies
Birds
Bats
How to attract a pollinator
Attributes of the “premordial” flower to attract pollinators:
Bisexual (both male and female parts)
Radially symmetric
More than two whorls of three separate paerianth organs each
More than two whorls of three separate stamens each
More than five spirally arranged separate carpels
In other words, a generalist advertisment
Why so much diversity in pollination syndromes (strategies)?
Generalist flowers:
Low efficiency, low fidelity, but low risk associated with pollinator loss
Specialist flowers:
high efficiancy, high fidelity, but high risk associated with pollinator loss
Main factors associated with insect declines
intensive agriculture
pesticides
ecological traits
urbanisation
deforestation
warming
wetland/rivers alteration
other pollutants
pathogens
fires
introduced species
