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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 Southern brown kiwi Paradise shelduck Weka Kakapo NZ quail NZ pigeon Kea North Island kokako 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 Ferns Gymnosperms Lots! Angiosperms 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 Ferns Gymnosperms 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 Chatham seedlings NZ seedlings litter Chatham saplings: non thorn Chatham saplings: thorn NZ saplings: thorn NZ saplings: non thorn 29 NZ spp NZ adults Chatham adults 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?