communities, biogeography, and selective forces: flora (including nz flora and moa herbivory)

Communities, biogeography, and selective forces: Flora (including NZ

flora and moa herbivory)

Questions

• Discussions: – Maria P: posting paper and questions for this

week– Jose Luis: will be picking a paper to post for next

week

• Any questions?

NZ

• Shearing: Sheep grazing• Sheep (60 m) outnumber people (3m) by 20:1

NZ

NZ herbivorous birds

• NZ lacked native mammals (except 2 bats)• 50% terrestrial birds eat non reproductive

plant parts

North Island kokako

Weka

NZ pigeon

Kakapo

KeaNZ quail

Paradise shelduck Southern brown kiwi

Moas

• Largest herbivores in scrub and forest up to 1800 m– Ratites: ~10 species in 6 genera of moas (20-200 kg)– Tallest stood ~ 2.5-3 m (giant moa)– Hunted to extinction in 15th century (along with 50% of

endemic birds, 40% of all birds)

Moas

• Closest relatives emus, cassowaries, tinamous, rheas, kiwis

• Snapping: Ostrich feeding

Moas: coprolites and gizzards

• Many twigs of shrubs and trees• Despite large size, they were feeding on small

herbs (<30 cm) and many rare species• Probably strongly shaped vegetation structure

(e.g., reduced niches of broad leaved woody species)

Flora

• High endemism and numerous trees (215 spp)– Many trees are short statured– Divaricating (wire plants): 10% of all woody plants

(overall common on islands: e.g., Madagascar, Hawaii, New Caledonian)

• Thin spreading branches

– Heteroblasty: 200 tree species• Changing leaf morphology with age

– Colour change with age

FernsGymnosperms

Angiosperms

Lots!

Flora

• Why my these evolve?– Divaricating– Heteroblasty– Colour change

Functions?

• Physiological tolerance of low temperatures, high wind or high light

• Moa herbivory

Evidence

• Cafeteria style feeding trials with emus and ostriches: Divaricating habit suffered 30-70% less herbivory

• Most divaricating, poisonous and deciduous species are short

• Small stature, deciduousness and divaricating, teeth increase with latitude

• Reversions to homoblasty found in Chatham Islands lacking moas

Evolution of colour changes

Evolution of colour changes

FernsGymnosperms

Angiosperms

Pseudopanax crassifolius

Pseudopanax crassifolius

Pseudopanax crassifolius

• Seedling leaves: dull and mottled brown due to anthocyanin production– Produced in plants <10 cm tall

• Juvenile leaves: long, linear, toothed with light areas near teeth– Produced in plants <3 m tall

• Adult leaves: oblong of more typical size and shape– Produced in plants >3 m tall

Pseudopanax chathamicus

Questions

• Could moa herbivory be a selective pressure leading to colour changes seen in P. crassifolius?– Compared spectral reflectance of different stages

to leaf litter– Compared spectral reflectance to a closely related

species (P. chathamicus) from nearby Chatham Islands (800 km from NZ) lacking moas with a flora derived from NZ

NZ seedlings

Chatham seedlings

litter

NZ saplings: thorn

Chatham saplings: thorn

NZ saplings: non thorn

Chatham saplings: non thorn

NZ adults

Chatham adults

29 NZ spp

Questions

• Could moa herbivory be a selective pressure leading to colour changes seen in P. crassifolius?– Compared spectral reflectance of different stages

to leaf litter– Compared spectral reflectance to a closely related

species (P. chathamicus) from nearby Chatham Island (700 km) lacking moas

– What do we think?