Plant-Insect Interactions I & II

Flashcards covering plant-insect interactions, including pollination syndromes, insect mutualisms, orders Thysanoptera and Hemiptera, phytophagy feeding modes, and plant defense mechanisms.

How does pollination occur during sexual reproduction in flowering plants?

Pollen (male germ cells) is transferred from the anthers to the stigma. A pollen tube then grows from the stigma down the style to an ovule in the ovary, where it fertilizes the egg to form a future seed.

What are the primary disadvantages of wind pollination compared to insect pollination, and what is a classic plant example?

Plants must produce enormous quantities of pollen (resulting in a high pollen-to-ovule ratio) with no guarantee that airborne pollen will reach a conspecific individual; a common example is ragweed (Ambrosia artemisiifolia).

Which ancient gymnosperm lineage and insect order represent one of the earliest known examples of specialized insect pollination?

Cycads (gymnosperms) and their specialized beetle pollinators (Coleoptera).

What is the botanical definition of a flower, and in which plant group are flowers exclusively found?

A flower consists of the sexual reproductive organs of a plant, often accompanied by modified vegetative structures to attract animals; by definition, true flowers occur only in angiosperms.

What reproductive benefits do plants gain by employing animal pollinators over abiotic wind pollination?

Plants achieve a lower pollen-to-ovule ratio by minimizing wasted pollen, dramatically increase the likelihood of conspecific pollen delivery, can pollinate successfully in environments where wind is ineffective, and maximize the number of coexisting plant species in a habitat.

What nutritional rewards do flowers provide to insect pollinators?

Pollen, nectar, and additional food tissues such as feeder anthers and fleshy petals.

Which major insect orders serve as primary pollinators, and which group is considered the most common?

The primary pollinating orders are Diptera, Coleoptera, Lepidoptera, and Hymenoptera; Hymenoptera (primarily bees, along with wasps and ants) are the most common.

What is a pollination syndrome, and what floral factors determine its specificity?

A pollination syndrome is a suite of flower traits evolved to attract a specific pollinator group, determined by attractants (color, scent), flower and inflorescence morphology, and daily flowering schedule.

What floral characteristics define the beetle pollination syndrome (cantharophily)?

Flowers are typically white or dull-colored, produce abundant pollen, lack nectar guides, offer extra food tissues with little or no nectar, and emit fruity odors or no scent at all.

What floral characteristics define the fly pollination syndrome (myophily/sapromyophily)?

Flowers typically exhibit carrion-like odors and visual cues resembling decaying organic matter, such as purple, reddish, or brownish coloration (exemplified by corpse flowers).

What floral traits characterize the butterfly pollination syndrome (psychophily)?

Flowers have an open landing platform, sweet scents, red, yellow, or blue petals, and provide nectar as the main reward (since butterflies cannot digest solid pollen), accessed via a long, thin proboscis.

What floral traits characterize the moth pollination syndrome (phalaenophily), as shown in Darwin's star orchid?

Flowers are white or greenish, bloom at night, produce sweet scents, and contain copious nectar concealed in deep structures, such as the $1.5\,\text{ft}$ nectar spur of the Madagascar star orchid.

What floral traits characterize the bee pollination syndrome (melittophily)?

Flowers are showy, brightly colored, bowl-shaped or bilaterally symmetric, provide sucrose-dominant nectar and pollen, and feature landing pads and nectar guides, including patterns visible under ultraviolet light.

How does deceit pollination operate in sexually deceptive orchids?

The flower mimics the visual appearance and female sex pheromones of specific insects without providing food rewards, luring males into pseudocopulation that attaches coherent pollen packets called pollinia to the insect's body.

What developmental sequence occurs in the mutualism between the Moreton Bay fig (Ficus macrophylla) and the fig wasp (Pleistodontes froggatti)?

Female wasps enter the syconium during the female phase to oviposit and pollinate; seeds and wasp larvae develop during the interfloral phase; and in the male phase, newly emerged winged females mate with wingless males, collect pollen, and depart to seek a new syconium.

What is myrmecochory, and what specific reward induces ants to disperse seeds?

Myrmecochory is seed dispersal by ants (found in at least $4.5\%$ of angiosperms); ants gather hard, inedible seeds to consume the elaiosome, a lipid- and nutrient-rich appendage attached to the seed coat.

What morphological characteristics define members of the order Thysanoptera ("thrips")?

Minute size ($0.5\text{--}15\,\text{mm}$, mostly $< 3\,\text{mm}$), fringed wings edged with long hairs, and asymmetrical mouthparts featuring a vestigial right mandible and a piercing stylet formed from the left mandible.

What unusual developmental and social characteristics occur within Thysanoptera?

They are haplodiploid (diploid females, haploid males), frequently parthenogenetic, can exhibit primitive eusociality with non-reproductive soldier castes, and undergo a hemimetabolous life cycle that includes a quiescent "pupal" stage with extensive tissue reorganization and occasional cocoon spinning.

What are the core morphological features of the order Hemiptera ("true bugs")?

Piercing-sucking mouthparts where the mandibles and maxillae are modified into needle-like stylets containing two canals, housed inside a grooved labium; hemimetabolous development; and thickened forewings (often hemelytra).

Why is the traditional suborder "Homoptera" no longer used in modern insect classification?

"Homoptera" was demonstrated to be a paraphyletic group.

What are the geographic distribution and dietary habits of moss bugs (suborder Coleorrhyncha)?

An ancient relict group of $< 30$ species restricted to the Southern Hemisphere (Australia, New Zealand, New Caledonia, and South America) that feed exclusively on mosses or liverworts.

What morphological modification distinguishes treehoppers (Membracoidea) within Cicadamorpha?

An elaborately enlarged, often ornate pronotum that extends back over the abdomen and mimics thorns, foliage, or other natural structures.

How does the trophobiotic mutualism between ants and sternorrhynchans (such as aphids) function?

Aphids suck plant sap and excrete excess sugary fluids known as honeydew, which ants collect as food; in exchange, the ants aggressively protect the aphids against predators and parasitoids.

What is phytophagy, and what specialized terms describe feeding on leaves, seeds, stems, flowers, and roots?

Phytophagy is the consumption of living plant tissues; feeding specializations include folivory (leaves), seed predation (seeds), stem boring (stems/wood), florivory (flowers), and rhizovory (roots).

How do host plant breadths compare between the monarch caterpillar and the fall webworm (Hyphantria cunea)?

Monarch larvae are extreme specialists restricted exclusively to milkweeds, whereas fall webworms are extreme generalists documented to feed on $636$ different plant species.

What is leaf mining, and which insect orders contain leaf-mining larvae?

Leaf mining is internal feeding where larvae consume tissue between the upper and lower epidermal layers of a leaf; it is practiced by larvae of Diptera (e.g., Agromyzidae), Lepidoptera, Coleoptera, and Hymenoptera.

What major agricultural pest belongs to Coleoptera: Curculionidae and infests cotton bolls?

The boll weevil (Anthonomus grandis).

What are plant galls, and which insect orders are primarily responsible for inducing them?

Galls are abnormal plant tissue growths formed in response to insect biochemical and mechanical activity, predominantly induced by Diptera, Hemiptera, and Hymenoptera (particularly gall wasps in Cynipidae).

What are the primary physiological and ecological challenges faced by herbivorous (phytophagous) insects?

Remaining attached to the plant surface, coping with higher rates of desiccation than in soil or litter, obtaining adequate nutrition from tissues that are deficient in proteins and vitamins compared to animal prey, and overcoming plant physical and chemical defenses.

What chemical classes serve as direct toxic defenses in plants against phytophagous insects?

Cyanide, cardiac glycosides, alkaloids, and juvenile hormone analogues.

What is the primary difference between constitutive and induced plant defenses?

Constitutive defenses are permanently synthesized and maintained, whereas induced defenses are activated or upregulated only following herbivore damage, conserving energy and metabolic resources when pests are absent.

What specialized anatomical structures do myrmecophytic plants provide to maintain defensive ant mutualists?

Hollow structural cavities called domatia (such as swollen thorns) for nesting shelter, Beltian food bodies produced at leaf tips as a source of proteins and lipids, and extrafloral nectaries (EFN) providing sugar solutions.