INSECT PLANT INTERACTIONS

INTERPRETATIVE WRITEUP ON INSECT PLANT INTERACTIONS BY DENNIS OWUSU BOATENG COCOA HEALTH & EXTENSION DIVISION (GHANA COCOA BOARD) Contact: +233-240296835, polonium90@yahoo.com Introduction  Insects and plants begun to co-evolve together when they come on the planet earth.  Insects and plants have a live style that helps each other to exist in the ecosystem.  Plants in order sense can be described as consumers while insect are producer.  This normally happens in carnivorous plants. Types of insect plant interactions  Interactions existing between insects and plants can either be; 1. Mutualistic 2. Parasitic/Predatory Mutualistic interactions  An interaction is said to be mutualistic when both parts enjoys or benefits.  There is a benefit to the plant as well as the insect.  Eg. Bees pick pollen from plant to prepare royal jelly and during this process pollination take place.  The process of pollination is described on the next slide. List of mutualistic interactions  Pollination  Seed dispersal  Domatia  Phytotelmata Pollination  Transfer of pollen grains from the male structure of a plant to the female structure of a plant. It can either be artificial or natural.  This is described as mutualistic because the insect turn to feed on the pollen through the process transferring the pollen to another place where germination can take place. Aspect of plant attracted by insects  Scent  Color  Nectar  Mimicry  Shape Pollination type for each insect  Bee pollination is described as melittophily.  Flies pollination is described as myophily.  Wasp pollination is described as sphecophily.  Beetle pollination is described as cartharophily.  Moth pollination is described as phaloenophily.  Butterfly pollination is described as psychophily. Seed and Fruit dispersal (Anemochory)  The spreading around of plant seeds is commonly referred to as dispersal.  Seeds that grow too near to their parent plants, have to compete with the parent plants for food, light and space.  Seeds therefore need to be spread away from their parent plant if they are to avoid this competition, and grow into well developed and healthy new plants. Modes of Seed Dispersal  There are a number of modes or ways by which seeds may be dispersed, these include: 1. Wind dispersal 2. Water dispersal 3. Animal dispersal 4. Mechanical dispersal  Ant pollination is termed as myrmeochory.  Elaiosomes are seed appendages that attract ants for pollination and seed dispersal because they contain high lipids and protein. Plate 1 Plate 2 Domatia  Domatia (meaning home) are tiny chambers produced by plants that house arthropods.  Domatia differ from galls in that they are produced during plant growth process rather than being induced by their inhabitants.  Most domatia are either inhabited by mites or ants, in which can be a mutualistic relationship, but other arthropods such as thrips may take advantage of the protection offered by this structure.  Domatia are often formed on the lower surface of leaves, at the juncture of the midrib and the veins.  They usually consist of small depressions partly enclosed by leaf tissue or hairs. Many members of the Lauraceae family have developed leaf domatia.  Domatia are also found in some rainforest tree species in the family’s Alangiaceae, Elaeocarpaceae, Icacinaceae, Meliaceae, Rubiaceae and Simaroubaceae. Phytotelmata  Phytotelma (plural phytotelmata) is a term for water bodies held by plants.  The water accumulated on these plants may serve as substratum for associated fauna, and often the fauna associated with phytotelmata is unique.  Examples of plants with phytotelmata are bamboo and pitcher plant. Parasitic/Predatory interactions  An interaction is described as parasitic when there is no mutual benefit between both partners.  There is a loss to one organism which may even lead to death.  This mostly happen during the process of feeding down by insects and other arthropods Phytophage or Herbivory  Process of insects feeding on plants is called either herbivory or Phytophagy.  Insects that eats plants are referred to as phytophagous species.  Phytophagous insects may be grouped into three types, 3 Types of Phytophage  Monophagous: meaning an insect that feeds only on one kind of plant (perhaps only one species). Eg silkworm.  Oligophagous: meaning insects feeding on several different kinds (or species) of plants. Eg. Spruce budworm.  Polyphagous: meaning insects feeding on a wide variety of plants. Eg. Armyworm. Phytophagous behavior that can be observed by insect activities  Leaf Chewing  Plant mining & plant boring  Sap sucking  Seed predating  Nectar or pollen feeding  Gall forming Leaf Chewers  Eat entire leaves or large portions of leaves  Primary groups: lepidopteran larvae (caterpillars), coleopterans (both adults and larvae), and orthopterans (both adults and nymphs).  Also sawflies and walking sticks can be considered.  Leaf-chewers can cause lots of economic damage leading to 5-20% of total leaf area per plant. Plate 3 Plant miners & plant borers  Plant mining involves burrowing into leafs or (less frequently) just below the surface of stems, fruits or roots.  Typically leaves a narrow trail or patch (especially in leaves), often filled with frass.  Done primarily by larvae of dipterans and lepidopterans; less frequently by larvae of coleopterans and hymenopterans  Causes economic damage by affecting health and/or appearance of plant.  Plant boring involves burrowing more deeply into stems, roots, or fruits. Always done by larvae. Borers may feed on living or dead tissue  Stalk borers include sawflies and some lepidopterans  Wood borers include coleopterans, lepidopterans and hymenopterans  Root borers include coleopterans and lepidopterans  Fruit borers include dipterans, coleopterans, and lepidopterans Plate 4 Sap suckers  Sucking pests, as the name implies, refers to a group of insects that insert their mouth parts into the plant cells and suck the sap, generally causing the cells to collapse and die.  Those that attack the leaves can leave white stippling or fine brown spotting as evidence of their presence.  They are generally found on the underside of the leaves.  Other leaf feeding pests affect the new growth by causing the leaves to curl and can also stunt the plant.  Plants can generally withstand a small amount of this type of damage but large numbers of sap sucking pests can seriously affect plant growth.  Sap sucking pests also attack the developing pods, causing scarring that results in twisted and misshapen pods, or small depressions in the pods. Aphids on a Cabbage Plant Plate 5 Nectar or pollen feeders  Nectar is high in sugars (carbohydrates) but low in proteins, while pollen is high in proteins but low in carbohydrates.  Nectar feeders generally have highly modified haustellate mouthparts Includes many hymenopterans, lepidopterans, coleopterans, dipterans, and thysanopterans Plate 6 Gall formers  Galls may have evolved from either mining/boring or surface feeding  The gall itself is beneficial to the insect, but probably not to the plant  Acts as shelter and probably increased food availability  However, galls are also obvious and so may attract predators, parasitoids or “squatters” (inquilines) Plate 7 Seed predators  Seed predation includes any process inflicted on a plant’s seeds by an animal that results in the inviability of the seed.  It can also refer to the consumption and digestion of the seed, but also includes the parasitization of seeds by insect larvae.  The high nutrient content of seeds makes them a valuable food source for many mammals, birds and insects.  Seed predation is an important ecological process that can affect the reproductive success of individual plants.  The dynamics of plant populations, and the evolution of defensive dispersal mechanisms and plant morphological traits.  Additionally the presence of seeds on a plant may be advertised, intentionally or unintentionally, by the presence of flowers or fruits.  Animals preying on undispersed seeds are typically small insects, such as flies, beetles, and moth larvae, with limited mobility.  These predators are often specialist feeders, restricted to one or a few plant species eg some seeds have special structures called elaiosomes which are edible; ants will carry seeds to a nest and eat this, thus dispersing the seed. References 1. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved 2. Kitching, R L (2000) Food webs and container habitats: The natural histor and ecology of phytotelmata. Cambridge University Press. ISBN 0-521-77316-4 3. Williams, J.B; Harden, G.J.; McDonald, W.J.F. (1984). Trees and Shrubs in Rainforests of New South Wales and Southern Queensland. Botany Department, University of New England. 4. Janzen, D.H. (1971) Seed predation by animals. Annual Review of Ecology and Systematics, 2, 465-492. 5. Harper, J.L. (1977) Population Biology of Plants, New York: Academic Press.