Presentation on theme: "Assigned readings Simon, R. et al. 1999. Floral acoustics: conspicuous echoes of a dish- shaped leaf attract bat pollinators. Science 333: 631-633 Anderson,"— Presentation transcript:
Assigned readings Simon, R. et al. 1999. Floral acoustics: conspicuous echoes of a dish- shaped leaf attract bat pollinators. Science 333: 631-633 Anderson, B. et al. 2005. Specialized bird perch aids cross-pollination. Nature 435: 41-42. *van Leeuwen, J.L. 2010. Launched at 36,000g. Science 329: 395- 396. Whitaker, D.L. & Edwards, J. 2010. Sphagnum moss disperses spores with vortex rings. 329: 406. Some journals now add a ‘popularized’ article* that interprets one of the more interesting papers in an issue; this is often an easier way to approach the material.
bambooweb Many animals (including beetles, ants, hawkmoths) are vectors and feed on the pollen and nectar rewards of plants.
Sensory capacities of animals differ: different sensory modalities are emphasized by different species: sight, sound, smell: light, mechanical waves, chemicals. Both katydids and dogs hear ultrasonic sound frequencies. Dogs access a world of smells we cannot. The vision of a hawk circling on high is of such superior resolution (fovea: special high-density of visual receptors) it can see and strike on mice or small birds far below. A flowering plant, under selection to reproduce, must set signals appropriate to the sensory biases of its pollen-carrying vectors. Appropriate signals will be different for nocturnal beetles than hummingbirds. Hummingbirds are particularly sensitive to red and plant species pollinated by hummingbirds set red flowers. There will be strong matches between sensory capacities of vectors and flowers. In like manner flowers pollinated by bats may use something appropriate to the bat’s acoustic specializations: to its echolocation by ultrasonic sounds.
Simon R., Holderied M.W., Koch C.U., von Helversen O. 2011. Floral acoustics: conspicuous echoes of a dish-shaped leaf attract bat pollinators. Science 333: 631-633. A sound-reflecting leaf specialized to orient bat pollinators. A bat-pollinated rainforest vine Marcgravia, has evolved a dish- shaped leaf (sometimes 2) with the upper concave side facing oncoming bat pollinators. This ‘dish’ reflects back the echoes made by the bat as a ‘echo signature’, localizing the flower within the sensory surround of the bat. A Leaf shaped to reflect a characteristic ‘echo signature’. In behavioural experiments the foraging time of the bats was significantly affected by the presence of the leaf.
Flower shape may be adapted to only allow access by humming birds, e.g., long-deep corolla requiring a long thin beak to access nectar. Selection discriminates between the effective pollinator and other species that are less so. Unlike bees, hummingbirds don’t collect pollen; they go for the nectar with specially modified tongues and beaks; but they do pick up pollen and transfer it. From the plant’s point of view its a good thing the bird doesn’t groom as much as bees.
Anderson B., Cole W.W., Barrett S.C.H. 2005. Specialized bird perch aids cross-pollination. Nature 435: 41-42. In South Africa a plant, Babiana, is called ‘rat’s tail’ because it grows a “curious sterile infloresence axis”. The function of this plant part is to provide a perch for visiting, and pollinating, sunbirds. The paper by Anderson et al. describes experiments demonstrating perch removal reduces the plant’s fertility.
Northwest of Upsala Ontario on the Trans Canada hwy Sphagnum refers to a genus of roughly 150-350 mosses found in cold and temperate climates, primarily in the Northern Hemisphere but also in New Zealand, Tasmania, and parts of South America. Sphagnum spp. belong to the phylum Bryophyta, the plant taxon containing mosses and liverworts.
Sphagnum is not what is called a vascular plant, i.e., no xylem or phloem, such vascular tissues being associated with adaptations for height. Sphagnum grows primarily in thick carpets with densities of 1-7 shoots per cm 2 depending on the species …can hold 15-20 X the moss's dry weight in water. This water retention allows for the spread of Sphagnum into drier areas, which in turn is responsible for the creation of large peatland mires. It is from this process that Sphagnum derives its common name: peat moss. Moreover, in addition to merely spreading, Sphagnum creates wet, acidic, anoxic conditions wherever it grows. These conditions are ideal for the moss and inhospitable to competing species. Peat mosses Sphagnum 285 spp.
Hyaline cells of Sphagnum with pores absorb water.
Spore capsules of Sphagnum, some already discharged. Epidermis of capsule dries in sun and shrinks capsule volume increasing internal air pressure. Pressure is a force. S. Whitehead As a bryophyte Sphagnum moss lacks a vascular system, making it incapable of growing tall. This is a problem, because the plant disperses its spores via moving air currents that begin 10-15 cm above the ground. Sphagnum shoots cannot grow nearly that high, so spores have to travel through a significant region of still air out of the boundary layer, to reach the air currents that are necessary for dispersal.
Spore discharge. J L van Leeuwen Science 2010;329:395-396 Published by AAAS Spore capsule (A); initially spherical the capsule containing spores is dried by the sun, changing to a cylindrical shape with elevated internal pressure; lid (operculum) gives way and pressure force launches making a toroid vortex (vortex ring) in air (fluid); toroid apparently returns force to spore mass during ‘lift off’ increasing height achieved. Importance of getting out of the still boundary layer where breezes and winds can keep the spores aloft and above terminal velocity. Spore discharge. (A) Spore capsule of Sphagnum fimbriatum on a short stalk. (B) The wet spherical capsule becomes cylindrical by drying. Quick release of the lid triggers spore discharge by internal air pressure. The jet of spores and air rolls up into a turbulent ring vortex that carries spores up to 15 to 20 cm.