Chemical communication in an aphid-natural enemy system: new mechanisms of aphid alarm signalling and wing induction [Elektronische Ressource] / von Eduardo Hatano

Eduardo Zamacois

Sujets

• Biologie

Informations

• Publié par: friedrich-schiller-universitat_jena
• Publié le: 01 janvier 2010
• Nombre de lectures: 6
• Langue: English
• Poids de l'ouvrage: 17 Mo

Extrait

Friedrich-Schiller-Universität
Jena

Chemical communication in an aphid-natural enemy
system: new mechanisms of aphid alarm signalling
and wing induction



Dissertation
Zur Erlangung des akademischen Grades
doctor rerum naturalium (Dr. rer. nat.)



vorgelegt dem Rat der Biologisch-Pharmazeutischen Fakultät
der Friedrich-Schiller-Universität Jena




von Master of Science (M.Sc.) in Applied Biosciences
Eduardo Hatano
geboren am 02.07.1980 in São Bernardo do Campo, Brazil





















































































Gutachter

1) Prof. Dr. Wolfgang W. Weisser – Friedrich-Schiller-Universität


2) Prof. Dr. Jonathan Gershenzon – Max-Planck-Institut für chemische Ökologie


3) Prof. Dr. Yannick Outreman – INRA-Agrocampus Ouest-Université Rennes



Tag der öffentlichen Verteidigung:


18 Januar, 2010


















































Table of contents

1. Introduction …………………………………………………………………………... 1
1.1. Aphids: life cycle, reproduction and morphs ……………………………………... 2
1.2. Natural enemies and defences of aphids ………………………………………… 3
1.3. Ecology of aphid alarm pheromones ……………………………………………… 5
1.4. Wing induction in parthenogenetic aphids ……………………………………….. 6
1.5. Aims and questions …………………………………………………………………. 7
1.6. Overview of manuscripts …………………………………………………………… 9
2. Manuscripts …………………………………………………………………………... 12
2.1. Manuscript I
Aphid wing induction and ecological costs of alarm pheromone emission under
field conditions ……………………………………………………………………………. 12
2.2. Manuscript II
Chemical cues mediating aphid location by natural enemies ……………………….. 24
2.3. Manuscript III
Aphid alarm pheromone mediates avoidance of habitats with increased risk of
intra-guild predation ……………………………………………………………………… 35
2.4. Manuscript IV
Do aphid colonies amplify their emission of alarm pheromone? ……………………. 49
2.5. Manuscript V
Don’t talk so loud: the emission of aphid alarm pheromone regulated by social
conditions …………………………………………………………………………………. 54
2.6. Manuscript VI
Entomopathogenic fungi stimulate transgenerational wing induction in pea aphids,
Acyrthosiphon pisum (Homoptera: Aphididae) ……………………………………….. 72
3. General discussion ………………………………………………………………….. 87
4. Summary……………………………………………………………………………….. 94
5. Zusammenfassung …………………………………………………………………. 96
6. References ……………………………………………………………………………. 98
7. Acknowledgments …………………………………………………………………… 104
8. Statement of independent assignment ………………………………………….. 105
9. Curriculum vitae ……………………………………………………………………... 106
10. List of publications ………………………………………………………………… 108



























INTRODUCTION

1. INTRODUCTION



Communication is the act of conveying information from one organism, the signaller, to
another, the receiver, and elicits specific behavioural or physiological or morphological responses
from the latter (Théry & Heeb, 2008). It is essential for organisms living in colonies to share the
collected information of the surrounding habitat with conspecifics to predict risks and
opportunities, and coordinate the group to enhance direct and/or indirect individual fitness
(Fletcher, 2007; Huang & Robinson, 1992). Therefore, by mediating and modifying the behaviour
of an individual, communication strongly affects the evolutionary and population ecology of
species (Dicke & Grostal, 2001). In many circumstances, the social interactions of the group, and
therefore communication among individuals, may mediate the division of labour and phenotypic
plasticity within a colony (Huang & Robinson, 1992; Robinson, 1992).
A signal may convey different ecological information, e.g. the availability of resources (Alcock,
1998a; Wright & Schiestl, 2009) or shelter (Visscher, 2007), the presence of potential sexual
mates (Alcock, 1998c; Cardé & Baker, 1984), and the population density (de Kievit & Iglewski,
2000). Signalling the presence of a predator for synchronization of defence is a central trait
necessary for the evolution of other traits (Pike & Foster, 2008), because predation causes more
serious, immediate and direct fitness costs than do other factors, e.g. starvation (Inman & Krebs,
1987; Lima & Dill, 1990). Alarm signalling is one strategy that evolved in many animal species to
alert conspecifics and thereby reduces their risk of being preyed on. Signals can be of many
kinds: acoustical (Hollen & Radford, 2009; Kelley, 2004), visual (Brown et al., 1999) or chemical
(Harborne, 1993; Law & Regnier, 1971), and may have two modes of action for the preys. First it
can alert conspecifics which may react with escaping (Alcock, 1998b), thanatosis so as to be
undetected (Miyatake et al., 2009), hiding in shelters (Venzon et al., 2000), or attacking (Rhoden
& Foster, 2002). The signaller may also benefit from mutualistic interactions and rely on
protection from interspecific organisms (Fiedler et al., 1996; Flatt & Weisser, 2000). Second it can
directly deter the predator attack (Ruxton et al., 2004).
Chemical compounds play an important role in mediating the communication of cells, tissues,
multicellular organisms and finally groups of individuals. Because compounds may have different
structures and traits and there are many environmental influences, species or groups of
taxonomically related species, communicate using one or a few stereotyped compounds. Volatile
organic compounds, for instance, are highly lipophilic products of low molecular weights that are
important for relative long-distance communication especially for insects and plants (Tholl et al.,
2006). Insects make use of volatile compounds as alarm pheromones to alert conspecifics of the
presence of predators. The chemical structures of alarm pheromones vary greatly among species.
If a signal were perceived by a non-target insect it could have high costs to signallers and
original receivers (Blum, 1969; Mustarpa, 1984). However, insect chemoreceptors and odorant-
binding proteins in insect antennae can differentiate specific structures from other similar
structures or isomers (Matsuo et al., 2007; Pelosi et al., 2006; Xu et al., 2005). In addition, some
insect species may use more than one compound and a certain optimal ratio among the
1 INTRODUCTION

compounds that trigger the alarm behaviour, while single compounds may cause no or little
response (Bruce et al., 2005). These two traits, alone or combined, may assist insects in reliably
discriminating the relevant alarm pheromones from compounds of other sources and is especially
relevant for alarm pheromones, since among all pheromones, they are the least specific
compounds (Blum, 1969).
If a species use more than one system to avoid predators when alarmed, it may optimize its
strategy by reallocating their resources to different types of responses to trade-off the benefits
and risks (Dicke & Grostal, 2001; Kats & Dill, 1998). Insects respond to alarm pheromones in
various ways: some may initiate a defence, some may disperse or keep feeding depending on
other factors, e.g. the presence of competitors, mates, natural enemies, climate conditions, the
availability of resources and previous experiences (Dicke & Grostal, 2001; Tollrian & Harvell,
1998). Aphids, for instance, are highly dependent on their alarm pheromones to survive an
imminent predator attack. A remarkable characteristic of aphids is their phenotypic plasticity:
aphids can produce individuals with different morphologies according to different stimuli, including
the emission of alarm pheromones and, therefore, the presence of a natural enemy. Because all
offspring produced by parthenogenesis are clones of their mothers and exhibit different
polyphenisms, aphids are an ideal organism for studying the influence of external factors on
phenotype while excluding genetic variation. However, the morphological, physiological and
behavioural responses of aphids when alarmed cannot be generalized because they vary among
and within species according to the ecology of each individual.


1.1. Aphids: life cycle