Pollination

What is Pollination?

Pollination is nature's matchmaking service—the critical moment when pollen from a flower's male parts reaches its female parts, allowing fertilization and seed production. Without pollination, most of our food crops, garden flowers, and forest trees couldn't reproduce. In Costa Rica's forests, an intricate dance between plants and pollinators sustains incredible biodiversity.

The Pollination Process

Step 1: Pollen Production

Anthers:

• Male reproductive organs at top of stamens
• Produce thousands to millions of pollen grains
• Each grain contains male gametes (sperm cells)
• Pollen released when mature

Pollen Characteristics:

• Wind-pollinated: Tiny, smooth, lightweight, produced in massive quantities
• Animal-pollinated: Larger, sticky, sculptured surface, fewer produced
• Species-specific shapes and structures

Step 2: Pollen Transfer

Vectors (Carriers):

• Wind (anemophily)
• Insects (entomophily)
• Birds (ornithophily)
• Bats (chiropterophily)
• Water (hydrophily)
• Other animals (zoophily)

Landing Site:

• Pollen must reach stigma (female receptive surface)
• Stigma often sticky to capture pollen
• May be highly selective (accepts only right species)

Step 3: Fertilization

Pollen Tube Growth:

• Pollen grain germinates on stigma
• Grows tube down through style
• Reaches ovary (can take hours to days)
• Delivers sperm cells to egg

Fertilization:

• Sperm cell fuses with egg cell
• Forms zygote (fertilized egg)
• Develops into embryo
• Ovary develops into fruit
• Ovules become seeds

Types of Pollination

Self-Pollination (Autogamy)

Definition:

• Pollen from same flower fertilizes same flower
• OR pollen from different flower on same plant

Advantages:

• Guaranteed reproduction (no mate needed)
• Works in isolated situations
• Every individual can produce seeds
• Efficient in stable environments

Disadvantages:

• Reduced genetic diversity
• Inbreeding depression
• Accumulation of harmful mutations
• Less adaptability to change

Examples:

• Many agricultural crops (wheat, rice, beans)
• Some pioneer species
• Plants in marginal habitats

Cross-Pollination (Allogamy)

Definition:

• Pollen moves between different plants
• Requires pollinator or wind
• Ensures genetic mixing

Advantages:

• Genetic diversity
• Hybrid vigor
• Adaptability to environmental change
• Disease resistance

Disadvantages:

• Requires nearby compatible plants
• Depends on pollinators/wind
• More energetically expensive
• Less reliable

Examples:

• Most forest trees
• Dioecious species (male and female plants)
• Many fruit trees

Pollination Syndromes

Wind Pollination (Anemophily)

Plant Characteristics:

• Small, inconspicuous flowers
• No petals or reduced petals
• No nectar or scent
• Feathery stigmas (capture airborne pollen)
• Exposed stamens
• Enormous pollen production

Examples:

• Oaks (Quercus): Catkins release clouds of pollen
• Grasses: All wind-pollinated
• Palms: Most wind-pollinated
• Conifers: Classic anemophilous

Costa Rican Examples:

• Highland oaks (Roble de Altura)
• Coconut palm (Coco)
• Grasses (various native species)

Insect Pollination (Entomophily)

Bee Pollination:

• Flowers: Yellow, blue, white, UV patterns
• Shape: Landing platforms, tubular
• Reward: Nectar, pollen
• Scent: Sweet, fresh
• Time: Daytime

Costa Rican Bee-Pollinated Trees:

• Guanacaste (Enterolobium cyclocarpum): Ball-like flower clusters
• Poró (Erythrina): Bright red tubular flowers
• Mango (Mangifera indica): Small flowers, heavy honey production

Butterfly Pollination:

• Flowers: Bright red, orange, pink
• Shape: Long tubular, landing platform
• Reward: Nectar (no pollen collection)
• Scent: Light, pleasant
• Time: Daytime

Beetle Pollination (Cantharophily):

• Flowers: Large, bowl-shaped, primitive
• Color: White, cream, greenish
• Scent: Fermented fruit, spicy (attracts beetles)
• Reward: Pollen (beetles eat it), sometimes nectar
• Structure: Sturdy (withstand beetle movement)

Costa Rican Example:

• Magnolia species: Ancient beetle-pollinated lineage

Bird Pollination (Ornithophily)

Hummingbird Pollination:

• Flowers: Tubular, no landing platform
• Color: Bright red, orange, pink (birds see red well)
• Reward: High-energy nectar (20-30% sugar)
• Scent: None (birds have poor sense of smell)
• Time: Daytime
• Structure: Sturdy (withstand hovering)

Costa Rican Hummingbird-Pollinated Trees:

• Poró (Erythrina poeppigiana): Brilliant red flowers
• Madero Negro (Gliricidia sepium): Pink tubular flowers
• Corteza Amarilla (Handroanthus ochraceus): Yellow trumpets (also bee-pollinated)

Other Birds:

• Some parrots pollinate while feeding
• Tanagers may pollinate accidentally
• Orioles visit some flowers

Bat Pollination (Chiropterophily)

Characteristics:

• Flowers: Large, sturdy, open at night
• Color: White, cream, pale (visible at night)
• Scent: Musty, fermented, strong (bats navigate by smell)
• Reward: Copious nectar, pollen
• Position: Outside foliage (easy bat access)
• Time: Nocturnal opening

Costa Rican Bat-Pollinated Trees:

• Pochote (Pachira quinata): Large white nocturnal flowers
• Ceiba (Ceiba pentandra): White shaving-brush flowers
• Balsa (Ochroma pyramidale): Pale flowers open at dusk

Bat Species:

• Glossophagine bats (nectar-feeders)
• Co-evolved with flowering plants
• Travel long distances (gene flow)
• Critical rainforest pollinators

Water Pollination (Hydrophily)

Rare in Trees:

• Mostly aquatic plants
• Mangroves (some species)
• Pollen floats on water surface
• OR underwater pollination

Pollination Strategies

Temporal Separation

Protandry (Male First):

• Anthers mature before stigma receptive
• Reduces self-pollination
• Common strategy
• Examples: Many Fabaceae (legumes)

Protogyny (Female First):

• Stigma receptive before pollen released
• Ensures cross-pollination
• Less common than protandry
• Examples: Some figs, magnolias

Spatial Separation

Herkogamy:

• Physical separation of anthers and stigma
• Different heights in flower
• Different positions
• Mechanical barriers

Dioecy:

• Male and female flowers on separate plants
• Guarantees cross-pollination
• 50% of plants don't produce fruit
• Examples: Papaya, some palms

Monoecy:

• Male and female flowers on same plant
• Separated spatially or temporally
• Self-pollination possible but reduced
• Examples: Oaks, corn, some Pochote

Chemical Barriers

Self-Incompatibility:

• Genetic system rejects own pollen
• Pollen won't germinate or grow
• Forces outcrossing
• Common in fruit trees

Heterostyly:

• Two or three flower forms
• Different anther/stigma heights
• Pollen from one form works on another
• Examples: Some Rubiaceae

Pollinator Relationships

Generalist Pollination

Multiple Pollinators:

• Flowers accessible to many species
• No highly specialized features
• More reliable (backup pollinators)
• Examples: Many temperate trees

Trade-offs:

• Less efficient pollen transfer
• Pollen may go to wrong species
• But more resilient system

Specialist Pollination

One or Few Pollinators:

• Highly co-evolved relationships
• Very efficient pollen transfer
• Plant and pollinator depend on each other

Examples:

Fig-Fig Wasp:

• Each fig species has specific wasp
• Wasp breeds inside fig
• Only that wasp can pollinate that fig
• Perfect mutualism

Yucca-Yucca Moth:

• Moth actively collects and places pollen
• Lays eggs in ovary
• Larvae eat some seeds
• Plant couldn't reproduce without moth

Costa Rican Example:

• Various palm species and specific weevils
• Some orchids and specific bees

Pollination Mutualisms

Benefits to Plant:

• Reliable pollen transfer
• To correct species
• Often long-distance (genetic diversity)

Benefits to Pollinator:

• Nectar: Energy (sugars)
• Pollen: Protein for larvae/adults
• Oils: Some bees collect floral oils
• Resins: For nest construction
• Shelter: Some flowers provide housing

Pollination by Deceit

No Reward:

• Flower offers no food
• Mimics another flower
• OR mimics female insect
• OR traps and releases pollinator

Examples:

• Some orchids mimic female bees
• Trap flowers capture insects temporarily
• Carrion flowers smell like rotting meat

Costa Rican Pollination Ecology

Seasonal Patterns

Dry Season Flowering (Dec-April):

• Many trees flower when leafless
• High visibility to pollinators
• Competition for pollinators intense
• Synchronized flowering common

Rainy Season Flowering (May-Nov):

• Constant food for year-round pollinators
• Less competition
• Flowers may last longer (less heat stress)

Altitudinal Variation

Lowland Rainforest:

• High pollinator diversity
• Many specialists
• Bat and insect pollination dominant
• Year-round activity

Highland Cloud Forest:

• Hummingbird pollination common
• Fewer bat pollinators
• Cooler temperatures
• Seasonal patterns

Dry Forest (Guanacaste):

• Highly seasonal
• Intense dry season flowering
• Migratory pollinators important
• Bat pollination in big trees

Threats to Pollinators

Habitat Loss:

• Forest fragmentation
• Loss of nesting sites
• Reduced flower abundance

Pesticides:

• Neonicotinoids harm bees
• Kill non-target insects
• Persistent in environment

Climate Change:

• Timing mismatches (phenology)
• Range shifts
• Extreme weather events

Invasive Species:

• Africanized bees outcompete natives
• Non-native plants may not support pollinators

Pollination and Fruit Production

Pollination Requirements

Self-Fertile Trees:

• Can self-pollinate
• Single tree produces fruit
• Examples: Mango (some varieties), Papaya (hermaphrodite)

Self-Sterile Trees:

• Need cross-pollination
• Require two or more trees
• Examples: Avocado (complex), many apple varieties

Dioecious Trees:

• MUST have male and female trees
• Only female produces fruit
• Examples: Papaya (usually), some palms

Pollination Services

Ecosystem Service Value:

• 75% of food crops require pollinators
• $235-577 billion globally per year
• Critical for biodiversity
• Undervalued and at risk

In Costa Rica:

• Coffee pollination by native bees
• Passion fruit by carpenter bees
• Native forests support crop pollinators

Human Intervention

Hand Pollination

When Needed:

• Greenhouse crops (no pollinators)
• Rare species conservation
• Breeding programs
• No pollinators available

Technique:

• Collect pollen from anthers
• Transfer to stigma with brush/cotton swab
• Labor intensive
• Ensures pollination

Commercial Use:

• Vanilla (always hand-pollinated)
• Date palms (sometimes)
• Greenhouse tomatoes (vibration)

Managed Pollinators

Honeybees:

• European honeybee (introduced)
• Hives rented for crop pollination
• Not native to Americas
• Can outcompete native bees

Native Bees:

• Stingless bees (Meliponini)
• More efficient for some crops
• Traditional Mayan beekeeping
• Increasingly managed

Pollinator Gardens

Supporting Pollinators:

• Plant diverse native flowers
• Bloom sequence through year
• Avoid pesticides
• Provide nesting habitat (wood, stems, ground)
• Water sources

Native Costa Rican Plants:

• Flowering trees (Poró, Madero Negro)
• Shrubs (various Inga species)
• Vines (passion flowers)
• Herbs (mints, salvias)

Why It Matters

Understanding pollination helps with:

• Fruit Production: Know pollination requirements
• Garden Planning: Plant for pollinators
• Conservation: Protect pollinator habitats
• Biodiversity: Recognize plant-pollinator networks
• Food Security: Value pollination services
• Reforestation: Include pollinator-supporting species
• Climate Adaptation: Understand vulnerability
• Education: Teach ecological connections

Observing Pollination

In the Field

Look For:

• Insects visiting flowers
• Pollen on insect bodies
• Hummingbirds at tubular flowers
• Bats at large nocturnal flowers
• Wind-dispersed pollen clouds
• Fruit development after flowering

Best Times:

• Early morning (most bee activity)
• Dusk (bat-pollinated flowers open)
• Dry season (mass flowering events)
• After rain (fresh flowers)

Identifying Pollinators

Behavior Clues:

• Pollinator: Methodical, visits many flowers, carries pollen
• Nectar thief: Bites through flower base, avoids pollen
• Pollen eater: Consumes pollen without pollinating

Conservation Implications

Pollination Crisis

Global Declines:

• Bee populations declining
• Monarch butterflies at risk
• Bat populations threatened
• Hummingbird habitat shrinking

Consequences:

• Reduced crop yields
• Wild plant reproduction failing
• Cascading ecosystem effects
• Economic losses

Protection Strategies

Habitat Conservation:

• Protect forests (pollinator homes)
• Create wildlife corridors
• Preserve old trees (nesting sites)
• Maintain flower diversity

Agricultural Practices:

• Reduce pesticide use
• Plant hedgerows and borders
• Leave wild areas
• Diverse crop planting

Climate Mitigation:

• Reduce warming (timing mismatches)
• Protect refugia
• Assisted migration if needed

Field Recognition

Pollination Event Checklist:

• ✓ Insect/bird/bat visiting flower
• ✓ Pollen visible on visitor
• ✓ Visitor probing flower interior
• ✓ Repeated visits to same species
• ✓ Pollen transfer visible
• ✓ Appropriate timing (day/night)
• ✓ Visitor behavior matches flower type
• ✓ Fruit developing after flowering

Signs of Successful Pollination:

• Flowers wilt and drop petals
• Ovary swells
• Fruit begins developing
• Seeds maturing inside

Failed Pollination:

• Flowers drop without fruit
• Ovary shrivels
• No seed development
• Common in isolated trees