lecture10 reproductive strategies notes

Reproductive and life history strategies: 

Reproductive and life history strategies Pollination syndromes Breeding systems Plant Gender and Mating systems Timing/frequency of reproduction Seed dispersal and dormancy

Parts of a Flower: 

Parts of a Flower

Pollination syndromes: 

Pollination syndromes Statistical constructs; particular floral traits tend to be over-represented among plant species that rely on particular pollinator species Our pollination lab will examine syndromes with morning glories Pollination syndromes

Wind pollination: 

Wind pollination Scentless, rewardless, colorless/green, usually small pollen grains, often aerodynamically complex under magnification Pollination syndromes Bird flowers Diurnal, often red, no scent, tubular, often pendent or horizontal, large quantities of dilute nectar

Bat/mammal flowers: 

Bat/mammal flowers Nocturnal, white or drab, fermentation odor, large and sturdy, nectar and pollen rewards Pollination syndromes Moth flowers Dusk and nocturnal, white, strong scent at night, long floral tubes, ample nectar

Butterfly flowers: 

Butterfly flowers Diurnal, orange or yellow, weak scent, long floral tubes, ample nectar Pollination syndromes Bee and beefly flowers Diurnal, often yellow or blue, with concentrated nectar rewards, bilateral symmetry, landing surfaces, nectar guides

Carrion flies and beetles: 

Carrion flies and beetles Diurnal, brown or purple, smell of decaying protein, presented near ground, can be traplike, no reward Pollination syndromes Female impersonators Some orchids are pollinated by deceit: take advantage of naïve males, look or smell like female bees or wasps, no reward

Plants and pollinators: 

Plants and pollinators Interactions are rarely specific Two exceptions: obligate mutualisms between figs/fig wasps, yuccas/yucca moths Pollination syndromes

Yuccas and figs: 

Yuccas and figs Insect pollinates flowers, lays eggs in developing fruit Insect larvae are seed predators An ongoing arms race: fruits with too much predation aborted in yucca; in figs, two kinds of flowers, only some can be predated Pollination syndromes

Breeding systems: 

Breeding systems Most appropriately, refers to variation in outcrossing rates Ranges from obligately self-pollinated to obligately outcross-pollinated Breeding systems

Slide11: 

Vogler and Kalisz, Evolution 55:202-204 Breeding systems

Why variation in selfing/outcrossing rates?: 

Why variation in selfing/outcrossing rates? We see intermediates in animal-pollinated spp, but fewer in wind-pollinated species Intermediate selfing may have something to do with pollinators? Many models of the problem…we need to start with definitions Breeding systems

Types of selfing: 

Types of selfing Geitonogamy: selfing within a plant, via pollinator movement Large floral displays increase chance of geitonogamy Breeding systems

Types of selfing: 

Types of selfing Cleistogamy: obligate selfing within a flower that never opens Most plants with cleistogamous flowers have chasmogamous (open pollinated) flowers as well Breeding systems

Cleistogamy and bet-hedging: 

Cleistogamy and bet-hedging A desert annual, Gymnarrhena micrantha Underground cleistogamous flowers produced regularly Outcrossed chasmogamous flowers produce smaller seeds with a pappus (for wind dispersal) More outcrossed seeds produced in wet (good) years Breeding systems

Slide16: 

Am Nat 112:636-639 Breeding systems

Types of selfing: 

Types of selfing Autogamy: selfing within a flower. Three types, defined by timing and whether pollinators are required Prior Delayed Facilitated Autonomous selfing Pollinator required Breeding systems

One mechanism of delayed selfing: 

One mechanism of delayed selfing Dole 1992. AJB 79:650-659 Breeding systems

When is selfing good?: 

When is selfing good? Automatic transmission advantage Mixed mating parent contributes three gametes, outcrossing pollen or seed parent only two Own seeds (female) Other’s seeds (male/pollen) Other’s seeds (male/pollen) Own seeds (male/pollen) Own seeds (female) Outcrosser Mixed mating Breeding systems

When is selfing good?: 

When is selfing good? No pollinators available (reproductive assurance) Selfing is good whenever it means you can have offspring by yourself. Baker’s rule: colonizing species are often capable of selfing. Breeding systems

Reproductive assurance in Collinsia: 

Reproductive assurance in Collinsia Emasculated flowers can only make seeds if visited by a pollinator; intact flowers can self Selfing ability usually related to flower size E. Elle and R. Carney, AJB 90:888-896 Breeding systems

When is selfing good?: 

When is selfing good? Habitat is ephemeral (time limitation) Selfing species are often found in deserts or other ephemeral habitats, e.g. Clarkia Runions and Geber 2000. AJB 87: 1439-1451. Breeding systems

Small-flowered Collinsia are found in drier habitats and flower earlier than large-flowered plants: 

Small-flowered Collinsia are found in drier habitats and flower earlier than large-flowered plants R2 = 0.75, P = 0.011 Elle 2004 (each point is a population mean) Breeding systems

When is selfing bad?: 

When is selfing bad? Pollen and Seed discounting Selfing reduces opportunities for outcrossing (your pollen or seeds are ‘wasted’ on selfing; reduction in outcross success = ‘discount’) Breeding systems

When is selfing bad?: 

When is selfing bad? Inbreeding depression Lower fitness of selfed relative to outcrossed progeny Breeding systems

Problem 5!!: 

Problem 5!! A researcher (Chris Eckert of Queens U.—I’m not making this up) has documented (using genetic markers) that selfing rates are high in Aquilegia canadensis. Design an experiment for Chris that will help him distinguish among four possible modes of selfing (geitonogamy and the three types of autogamy) that are possible in chasmogamous flowers. Be specific about your treatments—not how you’ll do them (I realize many of you won’t know what columbines look like), but what you need to manipulate and/or control, and what your expected results would be, to experimentally address the question.

How is outcrossing enforced?: 

How is outcrossing enforced? Herkogamy: distance between anthers and stigma (usually a continuous variable) In Datura wrightii, greater outcrossing with increased herkogamy Elle and Hare 2002. Functional Ecology 16:79-88 Breeding systems

How is outcrossing enforced?: 

How is outcrossing enforced? Heterostyly: fixed differences in positions of anthers and stigma. Breeding systems

How is outcrossing enforced?: 

How is outcrossing enforced? Dichogamy: differences in timing of different sex functions within flowers Protandry: male first Protogyny: female first Breeding systems

How is outcrossing enforced?: 

How is outcrossing enforced? Self incompatibility: genetic systems that prevent (potential) relatives from making offspring Gametophytic SI: haploid genotype of pollen grain recognized Sporophytic SI: diploid genotype of pollen parent recognized Breeding systems

Slide31: 

Breeding systems

Slide32: 

Breeding systems

Slide33: 

Breeding systems

Summary: Pollination and Breeding: 

Summary: Pollination and Breeding Floral morphology can often be used to form a hypothesis about both the pollen vector and the breeding system Breeding systems are highly variable in plants (because most are hemaphrodites) and are under complex selection