Coevolution of Insects and Coevolution of Insects and (Flowering) Plants(Flowering) Plants

Photographs in this presentation © Pearson Education or Fred M. Rhoades unless otherwise listed in notes.

CoevolutionCoevolution

• Mutual evolutionary influence between two species

• Insects and flowering plants are coevolved

• Which group “led” is in contention

Characteristics of InsectsCharacteristics of Insects

Nature of wings used to define insect orders

• Segments fused:

* Head

• Compound eyes

• Mouth parts: sucking, chewing, laping

• Other paired appendages

* Thorax

• 3 pairs of legs

• Wings: none, 1 or 2 pairs

* Abdomen

• “Visera” (reproduction, digestion, etc.)

Fig 33.33, part

Characteristics of Insects, Characteristics of Insects, cont.cont.

• Like all arthropods, insects molt

• Complete metamorphism

* Larva (feeding)

* Pupa (metamorph)

* Adult (reproduction)

• Incomplete metamorphism

* Immature look like small adults

* Gradual increase in size from molt to molt

Excellent web site on evolution of insect flight (and other insect facts) at the Hooper Virtual Micropaleontological Museum

Insect diversityInsect diversity

• Some 30 Orders

Insect evolutionInsect evolution

• Arthropods followed plants onto land

• Insects evolved on land

• First insect in Mid Paleozoic (springtail)

• Insect diversity explosion in Late Paleozoic

• Plants used for food and shelter

• Early seed plant pollen a food source?

• Further coevolution with plants in Mesozoic and Cenozoic

Plant spores and pollen are Plant spores and pollen are wind dispersedwind dispersed

• Spores:* Bryophytes* Ferns, etc.

• Pollen:* Gymnosperms (conifers, etc.)

• Exceptions (past and present):* A few, unusual mosses – Splachnum* Several cycads* Several Gnetophyta* Most flowering plants (but not all)Most flowering plants (but not all)

Splachnum moss grows on dung and spores are dispersed by flies.All that is seen here is the end of the sporophytes.

GymnospermsGymnosperms

• Cycads

• Gnetophytes

• Some are pollinated by beetles

Cycads in Univ. of Georgia Botany Dept. Greenhouse Pollination of Dioon (cycad) by beetles

Flower evolutionFlower evolution• Gymnosperm pollen or ovule predation by beetles• Some pollination occurred• First flowers

* Pistils hold ovules* Numerous, generalized parts* Lots of pollen

• Later flowers* Fusion of parts* Tubular* Bilateral symmetry* More colors

Benefits to the plantsBenefits to the plants

• Efficient pollen transfer • More outcrossing

Salmonberry flowers are hummingbird pollinated

Benefits to the pollinators.Benefits to the pollinators.• 70% of flowers

pollinated by insects• 30% of flowers

pollinated by wind, bats, birds

• Benefits* Pollen

• rich food source

* Nectar• average ~ 40% sugar

* No benefit? - Trickery• pseudocopulation

Bee Ophrys – diagram from Charles Darwin

Important pollinatingImportant pollinatingInsect OrdersInsect Orders

• Coleoptera – Beetles

• Diptera – Flies

• Hymenoptera – Bees, Wasps & Ants

• Lepidoptera – Moths & Butterflies

Coleoptera = “Coleoptera = “sheath-wings”sheath-wings”• Beetles (not Beatles)• 250,000+ named species • Chewing mouthparts• Beetle flowers

* Dull, light color* Strong odors: fruity,

spicy or fetid* Pollen, nectar, other

flower partsPhratora beetle head SEM by Alfred

Köpf - Sonoma State University

Magnolia

Amborella

Skunk Cabbage, Lysichticum

Diptera = “two-wings”Diptera = “two-wings”• Flies• 85,000+ named species• Most attack animals • Lapping, sucking or sawing

mouthparts• Fly flowers (carrion flies)

* Dull, dark colors* Fetid odors (dead meat) * Few pollen or nectar rewards

Blowfly SEMs - “tongue” ↑← head

Stapelia – “Carrion Flower” or “Starfish Flower”

Hymenoptera = “Hymenoptera = “membrane-wings”membrane-wings”

• Bees, Wasps, and Ants

• 110,000+ named species• Chewing & lapping mouthparts• Hairy bodies• Complex social behavior• “Bee” flowers

* bilaterally symmetrical* short fused petal tubes* yellows and blues* patterns visible in UV* nectar guides

Honey bee head SEM - University of Bath

Bumble bee stealing nectar from a Comfrey flower

Collinsia

Viola

Lepidoptera = “scaly-wings”Lepidoptera = “scaly-wings”• Moths (nocturnal) & Butterflies

(diurnal)• 150,000+ named species• Sucking mouthparts• Butterfly & moth flowers

* Like bee flowers, but with:* Long fused petal tubes* Butterfly colors: yellow, red* Moth colors: white or pale, fragrant

Cabbage Butterfly head SEM - University of Bath

Butterfly on Oregano flowers

Convolvulus“Morning Glory”

OdonataOdonata

• Grasshoppers, etc.

• Not pollinating insects

• But eat a lot of plant biomass with chewing mouthpart

Unsuspecting “bee fly” pollinator Unsuspecting “bee fly” pollinator gets nabbed for visiting marigoldgets nabbed for visiting marigold

There are dangers to being a pollinatorThere are dangers to being a pollinator