Input Template for Content Writers (e-Text and Learn More) 1. Details of Module and its Structure Module Detail Subject Name <Botany> Paper Name <Ecology> Module Name/Title <Species Interactions I> Module Id Pre-requisites <Basic knowledge about Interactions in living world> <To make students aware about different kinds of interaction prevailing Objectives among organisms> <Commensalism>,<>,<Protocooperation>,<>; <Mutualism>; < Keywords Coevolution> Structure of Module / Syllabus of a module (Define Topic / Sub-topic of module ) <Introduction>, <Direct and Indirect Interactions>, <Types of Direct <Species Interaction> interactions>, <Positive Interactions>; <.Models of Mutualism> 2. Development Team Role Name Affiliation Savitribai Phule Pune Subject Coordinator <Prof. Sujata Bhargava> University Paper Coordinator <Prof. NSR Krishnayya> MS University Baroda Content Writer/Author (CW) < Prof. Neeta Pandya> MS University Baroda Content Reviewer (CR) < Prof. NSR Krishnayya > Language Editor (LE) < Prof. NSR Krishnayya > Species Interaction I Ecology Interaction prevailing among different species TABLE OF CONTENTS(for textual content) 1. Introduction 2. Direct and Indirect Interactions: 2.1Direct Interactions: i. Positive interactions ii.Neutral interactions iii. Negativeinteractions 2.2Indirect Interactions: 3. Types of Direct interactions: 4. Positive Interactions: 4.1 Scavenging: 4.2 Commensalism: 4.3 Facultative Mutualism: 4.4 Obligate Mutualism: i. Mutualism and Co evolution: 5. Models of Mutualism: 6. Importance of Positive Species interactions: 7. Summary 1. Introduction Organisms do not live alone, all the time they are influenced by their neighbors and show a response to this influence. In ecology this is known as species interaction and is defined as the relation between species that live together in a community. Interactive species have a tremendous influence on the size of each other' populations. The various mechanisms for these biotic influences are quite different from the way in which abiotic factors effect the size of populations. Biotic factors regulate the size of populations more intensely. In an interactive community strong biotic interactions take place among species at the same trophic level within a local habitat (Cornell & Lawton, 1992) .Species interactions are basis for many features ofcommunity and ecosystem. The nature of these interactions can vary depending on the evolutionary context and environmental conditions in which they occur, as a result, ecological interactions between individual organisms and entire species are often difficult to define and measure and are frequently dependent on the scale and context of the interactions . 2. Direct and Indirect Interactions: Relationships between members of an ecological community can be classified within two broad categories, direct interactions and indirect interactions. Direct ones, deal with the direct impact of one individual on another and are not mediated or transmitted through a third individual while in the indirect interactions a species can ,through its direct interaction with some species ,indirectly influences the abundance of another species with which it is not interacting directly (Menge,1995). Species Interaction I Ecology Interaction prevailing among different species 2.1Direct Interactions: The impact of direct interactions can be visualized very clearly,they can be positive (+), neutral (0) or negative (-): i. Positive interactionsare those through which at least one of the species obtains a benefit from another species without damaging to the second individual or altering the course of its life. ii.Neutral interactionsare those in which there is no direct damage or benefit from any of the interactive species. The damage or benefit if taken is always indirect. iii. Negativeinteractionsare those interactions by which one of the species obtains a benefit in detriment of the other species. 2.2Indirect Interactions: The indirect effects are sequential processes in which direct effects are essentially involved, their effects are difficult to be detected as they are complicated by mixing of direct and indirect effects (Moon et al, 2010).Menge (1995) identified different pathways of indirect effects and reported that about 40–45% of all community changes in his study , resulted from indirect effects and suggested that the percentage could reach to 65% at other places. He emphasized that indirect effects are major source of bringing structural and dynamic complexity in communities. 3.Types of Direct interactions: There are eight main types of direct interactions which are classified by the net effect of the relationship on each interactor. Of these interactions mutualism and commensalism are positive interactions, there is no interaction effect in neutralism while the rest of the interactions are negative Commensalism is one sided interaction while mutualism is a cooperative interaction . Among negative interactions predation, parasitism and herbivory benefit one species and harm the other, while in competition the negative effect is on both the interactors. (Table 1).In nature all these interactions are prevalent and play a very important role in the ecological studies, the interactions are exhibited by a wide array of species and can be distinctly observed(Fig.1). Effect on Effect on Species A Species B + 0 - Predation + Commensalism Herbivory Mutualism Parasitism 0 Neutralism - Amensalism Competition Species Interaction I Ecology Interaction prevailing among different species Table 1: Types of Species Interactions. The sign +, 0 & - represent the effect of one species on another and indicate positive, neutral or negative effect respectively. Fig.1. Types of Species Interactions: a. Mutualism; b. Commensalism; c. Predation; d. Herbivory; e. Parasitism; f. Competition (Source: a- www.sciencegeek.com; b- Planetearth7.wiwkispaces.com; c- en.wikipedia.org; d- en.wikipedia.org; e- www.fcps.edu; f- www.kosm.com.my) 4. Positive Interactions: Positive interactions play a critical but underappreciated role in ecological communities by reducing physical or biotic stresses in existing habitats and by creating new habitats on which many species depend(Stachowicz,2001).Positive interactions amongst different species in a community are broadly classified into four types(Table 2). The degree of benefit varies with each type Interaction Effect on species A Effect on species B Nature of Interaction Commensalism (+) (0) One is benefitted, other is unaffected Scavenging (+) (+) Beneficial to both Facultative Mutualism (+) (+) Beneficial to both, but not obligatory Obligate Mutualism (+) (+) Beneficial to both, obligatory Table 2. Types of positive Interactions Species Interaction I Ecology Interaction prevailing among different species 4.1Scavenging: It is a direct food related interspecific interaction in which one partner called scavenger or saprobiont eats the dead bodies of other animals which have died either naturally or were killed by some other animals. Scavengers clean the environment and the available food is ultimately disposed off by which a major part of nutrients again enter for recycling. Animals such as foxes, hyenas, vultures etc. are examples of natural scavengers(Fig.3). Humans are much benefitted by activity of scavengers and have shown an interdependent relationship with them. This relationship has helped in shaping evolution of both, the humans and the scavengers (Moleon et.al., 2014). Decomposing microorganisms are also helping in utrient cycling and are good scavengers. Fig.2 Scavengers : Vultures eating a dead animal ,Fruiting bodies of a decomposing Fungus (Source: A- www.ehow.com, ; B - www.imgarcade.com) 4.2 Commensalism: It is an interaction in which one individual benefits while the other is neither being helped nor harmed,the interaction is "+/0". In this positive interspecific interaction the smaller benefitted member is called 'commensal', while the larger member that is neither benefitted nor harmed is called 'host'. In nature, individuals of one species are often physically attached to members of another. Ex. Epiphytes widely found in tropical rainforests grow on the branches of trees in order to access light, but the presence of the them does not affect the trees The epiphytes absorb water and minerals from the atmosphere by their hygroscopic roots and prepare their own food. In general, the host plant is unharmed, while the epiphyte that grows on it gets benefit of occupying space.In tropical rain forests many species live on a tree together to form a mat .Commensalism can be difficult to identify because the individual that gets benefit may have indirect effects on the other individual that are not readily noticeable or detectable.Other examples of commensalism are several species of Barnacles (molluscs) which grow on the hard shell of Limulus polyphemus (horse shoe crab) and Entamoeba coli ( protozoan) which lives as a commensal in the intestine of man. Species Interaction I Ecology Interaction prevailing among different species A B Fig.3 Many epiphytes growing on a tree trunk (A) ,parts of an epiphyte (B) (Source: A - Blogs.nybg.org, B- www.tutorvista.com) 4.3 Facultative Mutualism: It is a positive inter specific interaction in which both the partners are mutually benefitted and increase the chance of their survival. However, the interaction is not obligatory for their survival as both can live without this interaction. The relationship is also termed as non symbiotic mutualism or diffuse mutualism or protocooperation.