How Do Plants Vary In The Range Of Animal Spp They Use To Disperse Seeds/ Pollen? Give Examples Of How Fruit And Flowers Can Be Adapted To Use Specific Dispersers And Suggest Evolutionary Costs And Benefits Of Specialist Vs Generalist Strategies

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ADV of specialisation

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efficiency of pollination- plants have evolved to obtain max pollen transfer for minimum reward. different pollinators have different efficiencies. floral traits affect efficiency of transfer.
pollinator constancy: pollinator focuses on one spp of plant and ignores other- dont drop pollen on stigma of other flowers of diff spp. limited capacity to learn how to handle flowers- can only efficiently gather rewards from one flower.

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adv of generalisation

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pollinators fluctuate in abundance and activity independently of their plants, any one spp may fail to pollinate in a particular year. plant may be at an adv if it attracts several spp or types of pollinators, ensuring pollen transfer every year. plants do have self pollination.

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reevaluation of syndromes

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although some are functionally specialised, others are visited by v different pollinators. strict specialisation of plants relying on 1 pollinator spp rare- results in variable repro success across years. pollination syndromes= extremes of a continuum of greater or lesser specialisation or generalisation onto particular functional groups of pollinators that exert similar selective pressures.

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pollination syndromes

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convergent evolution towards phenotypes that limit no of spp that visit the plant, increase functional specialisation of plant w regard to pollination, may not affect ecological specialisation. responses to common selection pressures exerted by shared pollinators/ abiotic pollen vectors, generate correlations among traits.

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bee pollination

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variable in size shape and colouration. open and bowl shaped (radially symmetrical) or more complex and non-radially symmetrical (zygomorphic) e.g. foxgloves. tend to be yellow or blue, w UV guides and scent. nectar, pollen offered in varying amounts, sugar sucrose dominated. bees diverse. some plants only pollinated by bees through sonication. bumblebees sonicate, honeybees don't.

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butterfly pollination

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large and showy, pink or lavender, landing are, usually scented, dont digest pollen, more nectar offered. flowers have simple nectar guides, nectaries hidden in narrow tubes or spurs- long tongue.

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moths

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most nocturnal or crepuscular- flowers tend to be white, night opening, lage and show w tubular corollas, strong sweet scent, produced early morning or evening, night. lot of nectar produced for moth's high metabolic rates. other moths settle on flower, dont require as much nectar, flowers tend to be smaller.

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fly pollination

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imp in high altitude and latitude systems- numerous where others are lacking. myophily and sapromyophily. myophily- flys feed on nectar and pollen as adults, hoverflies- regularly visit flowers. fruit flies enticed by specific floral attractants emitted by some wild orchids, dont produce nectar-act as a sex pheromone precursor/ booster. myophilous plants dont emit strong scent, purple, violet and white, open dishes or tubes.
sapromyophiles- visits dead animals or dung, attracted to flowers that mimic this odor. no reward- leave quickly unless trapped

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birds

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hummingbirds oldest group-- large red or orange tubes, a lot of dilute nectar secreted during the day. odorless.
perching birds such as sunbirds need platform, less associated w tubular flowers

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bats

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large and showy, white or light coloured, open at night, strong odors. large and bell shaped. bats drink nectar. sight, smell, echolocation used to find them. New world- sulfur scented compounds in bat pollinated flowers. bigger pollen

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beetle

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large, greenish, off-white, heavily scented- spicy, fruity or similar to decaying organic material. flattened or dish shaped, easily accessible pollen. may include traps. ovaries protected from biting mouth parts. imp in semi-arid s africa.

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Johnson and steiner 2000

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surveys of plant families reveal strong differences in degree of specificity in pollination systems reflected by median no of pollinators per plant spp. asteraceae, ranunculaceae generalist, polemoniaceae, asplediadaceae and orchidaceae specialist

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examples of specialised pollination systems

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bats, hawkmoths, crepuscular beetles, fig wasps, resin collecting, oil collecting and euglossine bees

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south africa

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existence of numerous highly specialised pollination systems often involving 1 pollinator. one guild=20 plant spp pollinated by Moegistorhynchus longirostris a fly with a 60-100mm proboscis. plants pollinated by this fly have long narrow corolla tubes, flower only during weeks of year fly is active. oil producing flowers in many southern african spp belonging to Orchidaceae freq involve just one/two oil collecting spp

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Europe and eastern and northern North America

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few specialised pollination systems. pollinator fauna dominated by opportunistic social bees, limits possibilities for floral specialisation. generalised polliantion systems might have been adv for plants colonising post-glacial landscapes as well as modern agri-urban mosaics

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plants with generalist pollination systems less likely to experience what

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strong directional selection on floral traits.

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plants that depend on single spp more at risk of what

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extinction

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generalised systems might be what

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resilient to loss of some pollinator spp

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some plants w specialised pollination systems have what > what can this lead to

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compensatory mechanisms such as clonality, longevity and facultative self pollination. delayed extinction

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Waser et al 1996

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specialisation rare. generalisation common. moderate gen most common. mostly based on studies on single or few spp

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Fenster et al 2004-

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441 flowering plant spp within 10 miles of Carlinville, Illinois- same one examined by waser who said 91% of 375 taxa visited by 2+ animal spp, therefore generalised. 75% of flowering plant spp exhibit specialisation onto functional groups e.g. long tongued flies, small nectar collecting bees. pollination of each plant by small subset of available pollinators common- these subsets fall into functional groups in which visitors are likely to share attributes of behaviour, functional groups predicted on basis of pollination syndrome traits

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Vazquez and Aizen 2003

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unusually high no of extreme specialists and extreme generalists. even though sp distributed along continuum, extreme spec and gen may represent two highly adaptive alternative strategies.