Sexual Reproduction in Plants Movement onto land is an issue for sexual reproduction in plants unlike for animals Pollination Biology real story of the birds bees and beetles bugs butterflies bats Sexual Reproduction in Plants Pollination and seed dispersal important aspects of biosystematics in plants Gene flow Outcrossing vs inbreeding Reproductive isolation Speciation Co speciation coevolution pollination biology seed dispersal rely on movement of 1 pollen and 2 young embryo encased in a seed or fruit pollination biology seed dispersal Coevolution Coevolution interactions between two different clades as selective forces on each other resulting in adaptations that increase their interdependency Animal flowering plant interaction is a classic example of coevolution Plants evolve elaborate methods to attract animal pollinators Animals evolve specialized body parts and behaviors that aid plant pollination Divergence vs Convergence the dual issue of divergence of closely related taxa and convergence of distantly related taxa is important in biosystematic studies of seed dispersal and pollination biology Divergence vs Convergence classic example of both divergence and convergence in pollination is the family Polemoniaceae frequent shifts to different pollination syndromes from ancestral bee pollination V Grant hummingbird bat Zjhra Olmstead Sytsma 2004 Divergence vs Convergence neater example is evolution of orchid floral form in Platanthera of Northern Hemisphere read Hapeman Inoue paper Platanthera leucophaea Prairie fringed orchid Divergence vs Convergence DNA relationships indicate remarkable divergent and convergent shifts what kinds of floral changes have been involved with 3 separate shifts to nocturnal hawkmoth pollination Platanthera leucophaea Prairie fringed orchid Mullerian Batesian Convergence Mullerian Batesian Convergence interesting example of convergence in pollination among three genera of unrelated families in American tropics orange and yellow pigments used as animal signalling interesting example of convergence in pollination among three genera of unrelated families in American tropics a third genus shares the pollination signal but offers no nectar reward coloration pattern used by unrelated nectarbearing genera to attract butterflies and bees Peruvian assassin bug Asclepias milkweed Mullerian mimicry reinforcing signal Lantana sage Seed vs Pollen Dispersal Seed dispersal more important in field of plant geography the study of distributions of plant taxa Peruvian assassin bug Asclepias milkweed Batesian mimicry exploiting the signal Lantana sage Epidendrum orchid What is Pollination Pollination The transfer of pollen from the male anther to the female stigma in same plant or between two plants Pollination Syndromes morphologically convergent adaptive trends exhibited by the floral features of pollinated plants and in animal pollination the mouthpart structure and other flowerinteractive features of the pollinators Passive Active 1 Wind anemophily 3 Animal zoophily ornithophily entomophily 2 Water hydrophily Why do Animals Pollinate Plants Food reward in exchange for moving their pollen to another flower Nectar a sugary solution produced in special flower glands called nectaries Nectar concentration matches energy requirements of the pollinator bird and beepollinated flowers have different sugar conc Pollen is high in protein some bees and beetles eat it Flowers sometimes produce two kinds of pollen a normal and a sterile but tasty kind for the insect Evolution of the Flower Evolution of the flower is linked with evolution of pollination syndromes and why divergence convergence is pervasive in floral features Evolution of the Flower closed carpel for protection of ovules and seeds bisexual flowers to bring male and female parts closer primitive flowers had separate pollen and carpel bearing structures such as in Archaefructus and in all gymnosperms Archaefructus Drimys basal angiosperm Evolution of the Flower fusion of carpels into one pistil efficient deposition of pollen and movement of pollen tubes down one or few style lobes Evolution of the Flower exotic landing platforms spurs nectaries etc specialization for specific pollinators Evolution of the Flower epigyny protection of ovules from probing animals fusion of floral parts tubular structures for restricting nectar access Evolution of the Flower Placement of both stamens and carpels in the same flower causes inbreeding subsequent selection for outcrossing protogyny or protandry temporal sequence of anthesis or stigma receptivity 1 female phase 2 male phase Protogyny in Asimina pawpaw Annonaceae Evolution of the Flower Placement of both stamens and carpels in the same flower causes inbreeding subsequent selection for outcrossing self incompatibility chemical on surface of pollen and stigma style that prevent pollen tube germination on the same flower S allele incompatibility system Evolution of the Flower Placement of both stamens and carpels in the same flower causes inbreeding subsequent selection for outcrossing heterostyly reciprocal separation of anthers stigmas unisexuality reversal back to separate sexes in flowers Primula primrose Cucurbita zucchini Pollination Syndromes Caveats Pollination Syndromes Caveats not all visitors are pollinators many plant species with a specific syndrome have a surprising suite of effective pollinators Sunbird on bee pollinated Asclepias robber hummingbird on Campsis robber lycaenid on Lotus Halictid bee and vespid wasp pollinating mothpollinated Silene vulgaris Pollination Syndromes Caveats Insect Pollination Entomophily insect lineages diversified prior to angiosperms but coopted by and responded to by angiosperms Modern insect pollinators Beetles Coleoptera Flies Diptera Ants Hymenoptera Butterflies Lepidoptera Moths Lepidoptera Bees Hymenoptera Primitive type of insect pollination appears to be beetle or fly pollination ANITA Pollination Beetle Pollination likely that beetle first visited the female cones of conifers and fed on the pollination droplet exudates function of pollination droplet originally for capture of wind blown pollen shift as food attractant for beetles as in Welwitschia Welwitschia American Journal of Botany January 2009 ANITA grade has surprising number of pollination types including thermophily heat to volatize scents for fly pollination in Illicium floridanum Beetle Pollination Beetle Pollination beetle flowers usually have numerous parts