Plant Animal

8/3/2019 Plant Animal

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Pollination in the Tropics

1. Pollination BasicsA. Biotic Pollination

B. Abiotic Pollination

2. Pollination SyndromesA. Bees

B. Flies and BeetlesC. Moths

D. Butterflies

E. Bats

F. Birds

3. Weird Reproduction

4. Pollination in major

tropical ecosystems

5. Humans and Pollination


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The perfect flower:


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Pollination basics

Pollination = the transfer of pollen

(male microgametophyte) to receptive

female stigmas for reproduction.

Plants may be hermaphroditic,

dioecious or monecious.

Some plants are self-compatible, while

others are obligate outcrossers.

Pollen may be transferred by abiotic

vectors (wind, water) or biotic vectors

(animals such as insects, birds, bats).


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Abiotic Pollination

No need to attract pollinators

No production of nectar, no loss of

pollen, no production of flowers or

aromas

The plant can invest all of its energyinto making lots of pollen

In tropical regions, usually in

seasonally dry areas, such as in

savannas where grasses form anherb layer.

Not very common in rainforests


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Wind pollination isusually seen in

grasses, sedges,

pines, some palm

trees, and otheropen area species.

Wind

pollination


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Why wind pollination doesnt work well in tropical wet

forests:

It is a passive process, and

depends on environmental

conditions to be successful

Lack of consistent windmakes it ineffective in a

rainforest

High diversity makes it

unlikely that a pollen grain will land on a conspecific stigma

Lack of a leafless stage: its hard for pollen to get around

High humidity and rainfall reduce amounts of pollen in the air


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Biotic Pollination

Mutualistic relationship benefits both the plant and the animal

Animals: Benefit from an easy source of food (pollen or nectar)

Get as much as they can at each stop

Prefer lots of flowers close together, or a few big ones (expend

less energy on foraging)

Plants:

Benefit from dispersal of pollen to as many conspecifics as

possible: the further the better

Do not benefit from investing too much in showy flowers,

scents, attractants

Benefit from providing as little reward (pollen, nectar) as

possible for animal consumption


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250 + MYA

(late Paleozoic, Mesozoic)

e.g. Cycadales, seed ferns

Probably Beetles

Pollination perhaps inadvertent initially,

but floral traits that increased chances ofpollination and encouraged visits by most

efficient pollinators were favored by

selection

The carpel (female reproductive structure)

was originally leaf-shaped. It became foldedon itself to enclose and protect the ovule

from being eaten by the pollinators. Plants

with protected ovules would have a

selective advantage - angiosperms

Pollination Evolved from Pollinivory in early seed plants


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2/3 + of Angiosperms are animal pollinated + a smallproportion of Gymnosperms (e.g. Ephedra, cycads)

Pollinators include:

Flies (Diptera), Ants, bees, and wasps(Hymenoptera), Beetles (Coleoptera), Butterflies andmoths (Lepidoptera)

Hummingbirds, sunbirds, honey eaters

Bats, rodents, small marsupials

Oddities: Frogs, slugs, earthworms

Taxonomic Distribution


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Honey guides


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Pollination Syndromes

Often, plants that are visited by particular types ofpollinators will have things in common, especially

in their flowers, such as certain colors, shapes,

smells, etc.

These are generalizations though, not hard and fast rules!


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PollinatorFlowerColor

FlowerShape Scent Rewards

Bees Blue,

yellow,have UVpattern

Landing

platform,corolla tube

Sweet Usually nectar,

pollen, resin, orhormoneprecursors

Beetles Drab Open (flat) Strong; spicy,fruity, or smelly

Nectar, petals, orspecialized food

bodiesFlies Drab Open (flat) Strong; spicy or

smellyMoths Light

(white or

cream)

Tubularcorolla or

spur

Strong, sweet;produced in

evening

Nectar

Bats Dull Very longtubes

Very strongfermenting orfruity

Lots of nectarand pollen; flowerparts

Birds Red or

orange

Tubular Little or none Nectar, flower

parts, insects


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Bees

Bees are important in all tropical

communities.In rainforests, bees alone pollinate

almost half of all canopy trees and

lianas.

Bee pollinated flowers:

are often blue or yellow

have guide marks that are

visible in UV light

have a landing pad


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Flies and Beetles

Many fly- or beetle-pollinated plants mimic the

odor and/or appearance of dung or rotting flesh

to entice insects for feeding or oviposition.

They tend to be

brown or dull-colored.

Traps and windows are common. There

is often no nectar. This is called deceit

pollination.


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Mostly nocturnal

Moth pollinated flowers tend to be pale

Petals tend to be flat or recurved

Very strong, sweet scent

May only be open or producing scent or

nectar at night

Many moths have extremely long tongues,and feed on nectar from flowers with very

long corolla tubes, matching the their

tongue length.

Some moths that fly in

the day can be mistaken

for hummingbirds!

Moths


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Butterflies

Diurnal, good vision - see the color

red

Flowers pollinated by diurnal

butterflies are often colorful andodorless

Many butterfly flowers occur in

clusters - Asteraceae, milkweed


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Bats (Chiropterophily)Nocturnal nectar feeding bats have long

muzzles and weak teeth, and long tongues

to scoop pollen. Their flowers are often

pale, mustily scented, with long tubes and

wide mouths.

Pollen from these plants is

often high in protein and

important amino acids.


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Birds

Bird pollination is extremely important

in the tropics.Birds are visually oriented, and so their

flowers often are red, orange, purple or

yellow.

They tend to be unscented, with long

tubes and recurved petals.


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Pollinator Specialization

Generalist plants: a variety of smallinsects visit the flowers

Specialists: the plant is pollinated by a particular

assemblage of animals. Examples: orchids and

euglossines,Heliconia and hummingbirds.

Extreme specialists: almost one-to-one

host specificity, exemplified by figs and

fig wasps. This is rare.


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Freaky Reproduction

Examples of highly specialized plant-pollinator

interactions in the tropics are ubiquitous. However, some

plants have co-evolved with their pollinators to extremes

that seem almost bizarre.


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Aroids

2,500 described species,most pantropical.

Produce a huge variety of

scents, from nauseating toblissful.

Many have heat-

producing structures: this

helps diffuse the odors.

Often pollinated by flies

or beetles.


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Some aroids use modified leaves to trap

pollinators. When insects are attracted to the

dung-odor ofArum nigrum, they fall into a

dungeon and are prevented from leaving byone-way filaments. If the insects are carrying

pollen it is transferred to

the receptive female

flowers. Nectar isproduced to feed the

insects. Twenty-four

hours later, the male

flowers mature. The

filaments shrivel and

the insects escape -

but are covered with

pollen as they exit.

http://www.youtube.com/watch?v=4P8YhP5_oig&feature=related
http://www.youtube.com/watch?v=4P8YhP5_oig&feature=relatedhttp://www.youtube.com/watch?v=4P8YhP5_oig&feature=related


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This Titan Arum can be 12 feet

tall, and emits a strong smell of

decay! People used to believe itwas pollinated by elephants.

The stench attracts insects,

perhaps carrion beetles, for longdistances to lay their eggs. They

enter and transfer or receive

pollen.

Male and female flowers matureat separate times to avoid self

pollination.


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Sauromatum guttatum


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Over 25,000 species

described.

Nearly all orchids are

pollinated by insects -

notably bees and wasps,

but also butterflies, ants,

flies and others.

However, almost everyorchid species is

pollinated by just one or

two kinds of insects.

Tight relationship withpollinator: a species of

orchid may go extinct if

its pollinator insect dies

out.

Orchids


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Orchids as pollinator traps

Pollinators ofCoryanthes sp. fit

exactly to the size of a tunnel

formed by the lip and the column.

Approaching male euglossine

bees are excited by the fragrance,

and fall into the liquid-filled

bucket. The only way out is to

climb up the callus and squeeze

past the lip, first passing the

stigma (where pollinia are scrapedoff) and then the pollinarium

which is stuck onto the body of

the departing bee.Coryanthes gernotii

http://www.youtube.com/watch?v=CP1A6TLDQLQ&NR=1
http://www.youtube.com/watch?v=CP1A6TLDQLQ&NR=1http://www.youtube.com/watch?v=CP1A6TLDQLQ&NR=1


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Pseudocopulation

Ophrys is pollinated by several genera ofsolitary bees and wasps. It emits a

pheromone that mimics the scent of a

female pollinator, and even looks like one.

Males are highly attracted to the flowers.

Their repeated attempts at copulation

transport the pollinaria between orchids.Often these orchids bloom prior to the

emergence of the real females.


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Pseudoaggression

This orchid (Oncidium planilabre) mimics a male bee.

When a real bee spots this orchid he attacks it, attemptingto drive the intruder away. He strikes the inflorescence,

and pollinia are stuck on his head. When he attacks

another orchid the pollinaria are transferred.


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Figs and Fig Wasps

~1000 species ofFicus (Moraceae), each with own wasppollinator

fig fruit is a synconium: the inside is full of male and femaleflowers.

Male and female fig wasp

(Pleistodontes imperialis). Themale has a greatly reduced body

with two primary purposes: (1)

Inseminating the female and (2)

Drilling exit tunnels through the

syconium wall.

V i l i d i i b lli d l d


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Very precisely timed interaction between pollinators and male andfemale flowers. Female wasps enter a fig with receptive female flowers, ovipositsin sterile flowers and dies.

Males hatch first, mate with unborn females. Then they chew exittunnels out of the fig before dying. Male flowers are starting tomature and producepollen.

Newly hatchedfemales leave throughthe tunnels, but pickup pollen in doing so.When they enter a

new fig they depositthe pollen onreceptive femaleflowers as they searchfor oviposition sites.


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Pollination in major tropical

ecosystems Dry Forest - Santa Rosa

Lowland Rainforest - La Selva

Moist Forest - BCI

Montane Forest - Yanayacu

Mangrove - Milne Bay

Savannah - Serengeti

Desert - Sahara


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Dry forest - Santa Rosa

Lower species diversity than other

forest types

High degree of seasonality

restricts most pollination activity

to rainy seasons

Bees and moths most important

pollinators, some bats

Beetle, butterfly, and

hummingbird pollination are rare


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Lowland rainforests - La Selva

Very high diversity of trees -plants are widely distributed, butlocally rare

Pollination syndromes andcoevolution are common

Large, showy bracts are common Many tree species are

outcrossers, some understoryspecies are self-compatible

Mostly pollinated by bees,especially the canopy

Flowering time is variable


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Moist Forest - BCI

Has a more pronounced

dry season

More seasonal flowering


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Sequential blooming and simultaneous

fruiting in 6 species ofShorea


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Montane forests - Yanayacu

Wet and cold with greaterseasonality than lowland rainforest

Weather fairly unpredictable

Lower overall diversity thanlowland rainforest

Relatively higher diversity ofepiphytes

Many tree species are self-compatible or dioecious, long

lasting flowers More hummingbird pollinators,

fewer bees


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Mangroves

Old world mangroves

tend to be morediverse than those in

the new world.

Diverse pollination

mechanisms,including bats, birds,

bees and wind.

Some bear propagules

rather than seeds;similar to bearing live

young.


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Savannah and Desert

Many plants found in grasslands and deserts

are wind pollinated, which is possible in

these open, often windy habitats.

Vegetation includes perennial

grasses, shrubs, and trees at

oases.


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Desert - Sahara

Euphorbiaceae - same ecological niche as the

cacti of the New World deserts produce milky latex

small flowers in complex inflorescences

(cacti usually have large single flowers)

flowers often surrounded by large,

colorful bracts - pollinator attraction


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Humans and pollination

Efficient pollination is critical for agriculture.

Most food crops require animal pollination Beekeepers have used European honeybees for this in many

places.

1/3 of human food is derived from plants pollinated by wildpollinators

In the US, the value of wild, native pollinators is in thebillions of dollars each year.


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References:

Bawa, K.S. 1990. Plant-pollinator interactions in tropical rain

forests. Annu. Rev. Ecol. Syst. 21:399-422

Bawa, K.S., and M. Hadley (eds). 1990. Reproductive Ecology of

Tropical Forest Plants. UNESCO. Kricher, J. 1997. A Neotropical Companion. Princton Univ

Press.

Meeuse, B. and S. Morris. 1984. The Sex Life of Flowers.

Rainbird Pub. Grp. Ltd., London UK

Proctor, M., P. Yeo, and A. Lack. 1996. The natural history ofpollination. Timber Press, Portland OR.

Raven, P.H., R.F. Evert, and H. Curtis. 1976. Biology of Plants,

2nd ed. Worth Pub., New York NY

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Plant Animal