Tropical Botany Exam 2

What two features most broadly define a lowland tropical rainforest?

Complex structure and high biodiversity — not "thick jungle everywhere," and not neat, sharp layers.

Why is "dense jungle" a poor description of mature rainforest?

"Jungle" is thick, sunny regrowth in disturbed spots. A healthy, closed-canopy forest floor is actually open and shady.

What is an emergent tree?

A tree tall enough that its crown pokes above the main canopy — that's a position, not a type of plant.

Why is the classic "4-layer" rainforest diagram misleading?

Real layers blend together and vary a lot; they aren't neatly separated like the diagram shows.

What creates a "shifting mosaic" in rainforest structure?

Treefalls/storms open a gap -> sun-loving pioneer plants grow in -> shade-tolerant plants replace them as the canopy closes back up.

What is a buttress root for?

Helps hold the tree up, and sits near the nutrient-rich litter at the surface.

Heteroblasty vs. plasticity — which is which?

Heteroblasty = shape changes as the plant grows up (age-based). Plasticity = shape changes because of surroundings (like shade from neighbors).

What is "crown shyness," and what species shows it?

Small gaps between touching treetops of the same species. Seen in Borneo camphor (Dryobalanops aromatica).

Which plant family dominates many SE Asian rainforests, known for fast growth & big carbon storage?

Dipterocarpaceae

10|What is special about the Brazil nut tree (Bertholletia excelsa)?

One of the Amazon's most common big canopy trees. Pollinated by animals; seeds spread by agoutis (rodents) that bury/cache them.

Most rainforest trees are pollinated by ___ and dispersed by ___.

Animals; animals

How much annual rainfall is generally enough for many "rainforest" traits?

About 200 cm (79 in) or more per year.

What % of sunlight may be absorbed before reaching the rainforest floor?

Up to 99% — that's why the floor is so shady and often bare.

What is an epiphyte?

A plant that grows ON another plant just for support/light, but gets its own water and nutrients. Not a parasite.

How do tank bromeliads capture resources?

Their overlapping leaf bases form a little cup that holds rainwater and debris — like a mini pond.

Name 3 orchid adaptations for epiphytic life.

Roots for clinging on, water-storing pseudobulbs/thick leaves, and tiny seeds that drift on the wind.

Where on a tree are epiphytic orchids usually most diverse?

In the middle branches — not right at the trunk base, and not way out on the most exposed twigs.

What's the proposed function of Bird's Nest Anthurium's rosette and root shape?

Catches falling leaves for nutrients, and helps anchor the plant to the branch.

How does a strangler fig actually "strangle" its host?

It starts as an epiphyte, sends roots down to the ground, then wraps around the host trunk and shades out its crown. It does NOT tap into the host directly.

20|What is the phyllosphere?

The surface of a leaf — home to tiny bacteria, fungi, lichens, and liverworts ("epiphylls").

Give the +/- signs for: Mutualism, Commensalism, Parasitism, Competition, Amensalism.

Mutualism +/+ · Commensalism +/0 · Parasitism (or herbivory) +/- · Competition -/- · Amensalism -/0

Bentley & Carpenter 1984 — what did the PALM leaf gain from growing with epiphylls?

Noticeably more new nitrogen than a palm leaf growing alone.

Bentley & Carpenter 1984 — did the EPIPHYLL itself show a nitrogen benefit?

No clear benefit was found — but the overall relationship can still count as a mutualism.

Who actually fixes nitrogen in the palm/liverwort epiphyll system?

Cyanobacteria living on the leaf — not the liverwort tissue itself.

What is the "drip tip" hypothesis?

Pointed leaf tips help water drain off fast, which may keep leaves drier and cut down epiphyll growth.

Vine vs. liana — what's the difference?

Vine = soft-stemmed climber. Liana = woody climber. Both just use a host for support — not for food or water.

Why might climbers have more energy for growth/reproduction than a similar-sized tree?

They lean on a host for support, so they don't need to build a thick, self-supporting trunk.

What is skototropism? Give an example.

Growing toward darkness, to find a tree trunk to climb. Seen in young Rhaphidophora cryptantha seedlings.

Passiflora coccinea vs. Passiflora caerulea — pollinators?

P. coccinea (red flowers) = hummingbirds. P. caerulea = large bees.

30|What is a "nectar thief"?

A visitor (like a small stingless bee) that steals nectar without pollinating the flower.

How do Aristolochia grandiflora/gigantea deceive pollinators?

They smell/look like rotting flesh but give no real reward — "pollination by deceit."

How does Aristolochia maxima differ in strategy from A. grandiflora?

It actually gives the pollinator a real place to lay eggs — the trick evolved into a true mutualism.

How does the liana Alsomitra macrocarpa disperse its seeds?

By wind — its seeds have wings and glide. Unusual, since most rainforest lianas use animals instead.

Pollination vs. dispersal — how are they different events?

Pollination moves pollen to a flower. Dispersal moves seeds away from the parent plant. Different timing, often different helpers.

What is cauliflory? Give 3 examples.

Flowers (and fruit) growing straight out of the trunk or old branches. Examples: cacao, jackfruit, calabash.

Cauliflory vs. "large fruit" — what's the key distinction?

Cauliflory is about WHERE flowers grow (on the trunk). Big fruit size is a separate trait that may be helped by that position.

Warren & Emamdie 1997 — trunk vs. canopy flowers in cacao/Brownea?

Trunk flowers attracted more pollinators and made more fruit than canopy flowers.

How does Aristolochia arborea attract pollinators at its trunk base?

It mimics mushrooms to lure in fungus gnats.

What is hypothesized to pollinate the cauliflorous liana Uvaria elmeri?

Cockroaches.

40|Theobroma cacao — understory cauliflorous tree — what pollinates it?

Tiny midges (a type of fly).

"Walking palm" Socratea exorrhiza — what's actually true?

It has stilt roots that help it stand on uneven ground. It does NOT actually walk.

Backscatter hypothesis (red Begonia leaf underside) — what did Hughes et al. 2008 find?

No real difference in photosynthesis between the red and green parts of the leaf. The hypothesis wasn't supported.

Amorphophallus titanum vs. Rafflesia arnoldii — single flower or inflorescence?

Amorphophallus = one giant inflorescence (many tiny flowers together). Rafflesia = one single giant flower.

Define hemiparasite, holoparasite, and mycoheterotroph with an example each.

Hemiparasite = still photosynthesizes, but also taps a host (Macrosolen). Holoparasite = no photosynthesis, fully depends on host (Rafflesia). Mycoheterotroph = gets its carbon from fungi instead (Voyria).

Epiphyte vs. parasite — what's the key resource difference?

Epiphyte only uses the host for physical support and gets its own water/nutrients. Parasite actually taps the host for water, nutrients, or carbon.

What is a haustorium?

The special structure a parasitic plant uses to tap into its host for water and nutrients.

How is Macrosolen (a mistletoe relative) pollinated?

By birds — the flower only opens when a bird grips it, which dusts pollen onto the bird.

What is Rafflesia's host plant?

Tetrastigma, a woody vine in the grape family.

What is unique about Balanophora's tissue, and its sexual system?

It's a root parasite whose tissue actually blends with its host's tissue (a "chimera"). It's monoecious — male and female flowers on the same plant.

50|Okoubaka aubrevillei ("the death tree") — what's the puzzling evidence?

It kills nearby trees through underground connections, but doesn't seem to grow any better for it. So is it really a parasite, or just clearing out competition?

Why might Rafflesia flowers have evolved to be so enormous?

Carrion flies prefer bigger carcasses, so a bigger "fake corpse" flower may attract more flies and pollinate better.

What two floral organs can form Rafflesia's giant central chamber?

Either a ring of growing tissue, or petal tissue, depending on the species. Gigantism evolved twice, in two different ways.

What is the leading hypothesis for how Rafflesia seeds disperse and infect a new host?

Ants may be drawn to oily seeds and carry them near host roots — but this still isn't confirmed.

Give 3 reasons Rafflesia's phylogeny is hard to reconstruct, even with DNA.

It has no leaves, stems, or roots to compare; it lost its chloroplast DNA (usually key for plant studies); and it picked up a lot of its host's genes, which confuses the DNA tree.

What % of Rafflesia's genome came from its host via horizontal gene transfer?

About 2-3% of its nuclear DNA, but up to half of its mitochondrial DNA.

What is thermogenesis, and why does Rafflesia use it?

Making its own heat — it helps spread its rotting-meat smell to attract flies.

Define domatia, extrafloral nectaries (EFNs), and food bodies.

Domatia = hollow spaces that house ants. EFNs = nectar glands outside the flower. Food bodies = nutrient packets plants grow just for ants to eat.

Myrmecophyte vs. myrmecophile — what's the difference?

Myrmecophyte = a plant that actually houses ants. Myrmecophile = a plant ants just visit, with no housing.

What is myrmecochory?

Seed dispersal by ants, usually because a food reward is attached to the seed.

60|Urera baccifera — what do ants AND birds both do for this plant?

Both help spread its fruit/seeds. Ants visiting for food rewards also help scare off herbivores.

Myrmecodia — what houses the ants, and what do the ants give back?

Swollen stem chambers house the ants; ant waste fertilizes the plant.

Dischidia major's "urn" leaf — what 3 functions does it combine?

Shelters ants, absorbs nutrients from their waste (via roots inside), and uses the ant-enriched air inside for gas exchange.

Squamellaria — why is this called ant "domestication" of a plant?

Ants plant its seeds, live inside its chambers, and feed it with waste and nectar — basically farming it.

Cecropia and Macaranga are unrelated trees on different continents with similar ant partnerships — what does this show?

Convergent evolution — two unrelated plants independently evolved the same ant partnership.

What is a "devil's garden," and which tree is a classic example?

A patch of forest where one ant-friendly tree species grows almost alone, unnaturally. Duroia hirsuta (Amazon) is the classic example.

Frederickson et al. 2005 — how did they prove ANTS (not tree chemicals) create devil's gardens?

They planted seedlings inside and outside the gardens, with and without ant access. Seedlings only got killed inside gardens that still had ants.

Which ant "weeds" the devil's garden, and with what weapon?

Myrmelachista schumanni — kills other plants with formic acid.

Linsenmair et al. 2001 — do ants benefit Macaranga plants?

Yes — plants with ants grew much better than plants without ants.

Linsenmair et al. 2001 — do the ants benefit from Macaranga?

Yes — more food bodies meant bigger ant colonies, and taking food bodies away shrank the colonies. A two-way mutualism.

70|What's one potential "cost" that ants can bring a Macaranga plant?

Ants often protect scale insects (for their honeydew), and those scale insects can hurt the plant.

Species richness vs. evenness — define both.

Richness = how many species are present. Evenness = how evenly individuals are spread among those species.

What is "hyperdominance" in the Amazon (Ter Steege et al. 2013)?

Just 227 tree species make up about half of all individual trees in the Amazon — even though total richness is huge.

Hyperdominance vs. monodominance — what's the scale difference?

Hyperdominance = a few species dominate numbers across a whole region. Monodominance = one species dominates a single forest patch.

Muthuramkumar et al. 2006 (Western Ghats) — how did fragment size affect tree vs. understory diversity?

Bigger forest fragments had more tree species, but understory diversity didn't increase the same way.

Xu et al. 2016 — average phosphorus or phosphorus VARIATION: which predicted tree diversity?

Variation (patchiness) in soil phosphorus predicted diversity. The average amount did not.

According to the topography study, are rainforest trees associated with conspecifics, topography, or both?

Both — trees cluster near others of their own kind, and also favor certain elevations/slopes.

What is the refugial hypothesis for Amazon diversity?

During dry ice-age periods, rainforest shrank into separate "island" patches where species evolved apart, then mixed back when the forest regrew.

Bush & Oliveira 2006 — did Amazon sediment pollen support the refugial hypothesis?

Not really — grass pollen wasn't much higher during the ice age, so there's little evidence savanna replaced most of the rainforest.

What does the intermediate disturbance hypothesis predict?

Diversity is highest with a moderate amount of disturbance. Too little lets one species take over; too much leaves only fast pioneers.

80|Molino & Sabatier 2001 (French Guiana) — what pattern did they find?

Tree diversity peaked at a moderate level of disturbance — supporting the hypothesis.

What is monodominance? Give two examples.

One tree species taking over a forest stand, unusual for typically diverse tropical forests. Examples: Gilbertiodendron dewevrei (Congo), Dicymbe corymbosa (Amazon).

What is the Janzen-Connell hypothesis?

Pests/diseases that target one species build up near its parent trees, killing nearby seedlings of that species — which stops it from taking over.

Dipteryx oleifera example — what's the key Janzen-Connell distinction?

Seeds land mostly near the parent tree, but they survive better farther away. Landing somewhere isn't the same as surviving there.

Peay et al. 2013 (Peruvian Amazon) — which fungi correlated with plant richness?

Pathogens and endophytes were linked to tree diversity; mycorrhizal fungi were a weaker link; yeasts showed no link at all.

Moles et al. 2011 — is herbivory definitely greater in the tropics?

No — the data are mixed. There isn't enough evidence to say herbivory is truly higher in the tropics.

Salazar et al. 2016 (Piper) — which chemical diversity deters generalists vs. specialists?

More variety in low-volatility chemicals cuts damage from generalist herbivores. More variety in high-volatility chemicals cuts damage from specialist herbivores.

How might Caladium steudneriifolium's leaf variegation deter herbivores?

Its pale patches may look like existing leaf-miner damage, tricking herbivores into thinking the leaf is already "used up."

What is the "Red Queen" hypothesis (Heliconius butterflies & Passiflora)?

Plants and herbivores keep evolving to outdo each other — better plant defenses push herbivores to adapt, which pushes plants to defend even more, forever.

Radhamani et al. 1995 — what did Passiflora foetida's sticky bracts protect most?

Flower buds — way less damage with the sticky bracts than without them. Fruit damage wasn't really affected.

90|Niche differentiation vs. environmental filtering vs. neutral theory — one line each.

Niche differentiation = species split up resources, ending up more different than random. Environmental filtering = similar conditions favor similar traits, ending up more alike than random. Neutral theory = it's basically random chance.

Baraloto et al. 2012 — which assembly hypothesis did the big tropical tree dataset support?

Environmental filtering — species living together had more similar traits than you'd expect by chance.

What is neutral theory (Hubbell 2001)?

A model where species are treated as basically identical, and community patterns come from random births, deaths, dispersal, and extinction — no special "rules."

Name 5+ potential causes of landscape vegetation mosaics (e.g., rainforest/dry forest/cerrado/caatinga patches).

Rainfall patterns, water/drainage, soil nutrients, topography, fire, herbivory, and human land use.

Domestication vs. cultivation — what's the difference?

Domestication = the plant's genes actually changed from human breeding. Cultivation = just growing/tending a plant — it can still be genetically wild.

What kind of genes drove dramatic maize-from-teosinte changes?

Mostly a handful of major genes, plus many smaller-effect genes adding up.

Can cultivation happen without domestication?

Yes — you can grow and care for a plant that's still genetically wild.

Marula (Sclerocarya birrea) has separate male and female TREES — what sexual system is this?

Dioecy (separate male and female individuals). Monoecy would mean both sexes on the same plant.

Leakey et al. 2005 — what marula fruit pattern hinted at early domestication?

Farmer-grown trees tended to have more large fruits than wild trees — a hint (not proof) of early selection.

Match the use: Hevea brasiliensis, Copaifera langsdorfii, Allanblackia, Dioscorea.

Hevea = rubber latex. Copaifera = oily "diesel tree" resin. Allanblackia = seed oil. Dioscorea = starchy yam tuber.

100|Vietmeyer's jojoba story — how did one desert plant help "save the whales"?

Jojoba oil is a lot like sperm whale oil, so using it instead helped cut down on whale hunting.