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