Parasitoids [Elektronische Ressource] : metapopulation ecology and genetics, mating behaviour, and aphid host resistance / von Franklin N. Nyabuga

Franklin Nyabuga

Informations

• Publié par: friedrich-schiller-universitat_jena
• Publié le: 01 janvier 2010
• Nombre de lectures: 14
• Langue: English
• Poids de l'ouvrage: 9 Mo

Extrait

Friedrich-Schiller Universität

Parasitoids: metapopulation ecology and genetics,
mating behaviour, and aphid host resistance


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 MSc. (Crop protection) Franklin N. Nyabuga
Geboren am 07.07. 1976 in Kisii/ Kenia


















Gutachter:


1. Prof. Dr. Wolfgang W. Weisser

2. Prof. Dr. Hugh D. Loxdale

3. Prof. Dr. Christoph Vorburger


Tag der Doktorprüfung und öffentlichen verteidigung: Jena, 23 März 2010







Table of Contents
Introduction .................................................................................................................................... 1
Article I: Microsatellites from Lysiphlebus hirticornis Mackauer (Hymenoptera: Braconidae), a
specialist primary parasitoid attacking the specialist tansy aphid, Metopeurum fuscoviride
Stroyan (Hemiptera: Aphididae) .................................................................................................. 13
Article II: Spatial population dynamics of a specialist aphid parasitoid, Lysiphlebus hirticornis
Mackauer (Hymenoptera: Braconidae: Aphidiinae): evidence for philopatry and restricted
dispersal ....................................................................................................................................... 19
Article III: The consequences of an unstable relationship: genetical metapopulation dynamics of
Lysiphlebus hirticornis Mackauer, a specialist parasitoid attacking a specialist aphid host on
common tansy .............................................................................................................................. 39
Article IV: Population structure of the tansy aphid, Metopeurum fuscoviride and its specialist
parasitoid Lysiphlebus hirticornis ................................ 69
Article V: Mating strategies in solitary aphid parasitoids: effect of patch residence time and ant
attendance..................................................................................................... 81
Article VI: Effects of pea aphid secondary endosymbionts on aphid resistance and development
of the aphid parasitoid, Aphidius ervi: a correlative study ........................................................... 99
General discussion ..................................................................................... 121
Summary .................................................................................................................................... 129
Zusammenfassung ...................................................................................................................... 133
References .................................. 137
Acknowledgements .................................................................................................................... 155
Declaration ................................. 157




General Introduction
Introduction
Introduction to problem statement
Insect parasitoids are ubiquitous members of natural insect communities and important agents of
population regulation through biological control. Understanding, therefore, the parasitoid
population structure and their ecological and evolutionary interactions with their hosts is of great
practical and theoretical interest. Given that parasitoids need to parasitize hosts and that, by
definition, they kill their host as part of their normal lifecycle, there is bound to be reciprocal
coevolution whereby the hosts develop resistance with negative consequences for their
parasitoids. The mating patterns of the solitary parasitoids of gregarious hosts may be influenced
by adult parasitoid resource use behaviours on the natal patch, in addition to other interacting
organisms such as trophobiotic ants on those natal patches. This section contains a review of
literature on aphid hosts and their parasitoids’ genetic metapopulation structure, evolving mating
opportunities, aphid host resistance and its effect on parasitoid fitness, research questions, brief
introduction to the methodologies, justification of the study and a brief overview of the
manuscripts discussed in this thesis.

Parasitoid and host metapopulation genetic structure
The spatial distribution of interacting species affects their coexistence and co-evolution
(Thompson, 1994). Althoff & Thompson (1999) found incongruent geographical genetic
structures and subsequently established that the patchy distribution of the host food plant
contributed to the genetic structure of the Aganthis parasitoids (Althoff & Thompson, 2001).
Before, it had been realized that many species consist of assemblages of ephemeral
subpopulations or demes that persisted over time in a dynamic balance between local extinction
and recolonization termed ‘metapopulations’ (Levins, 1969). A metapopulation is defined as a
population of populations with an age structure established by the birth of populations through
colonization and their death through extinction, a description since broadened to cover any
population system in which discrete subpopulations exchange genes with one another through
dispersal (Pannell & Charlesworth, 2000).
In a field survey, Weisser (2000) established that an aphid host-parasitoid system comprising
the specialist wasp parasitoid, Lysiphlebus hirticornis Mackauer (Hymenoptera: Braconidae:
Aphidiinae) attacking the specialist aphid, Metopeurum fuscoviride Stroyan (Hemiptera:
Aphididae), which feeds exclusively on common tansy plants, Tanacetum vulgare L. (family
Asteracae), has a classic metapopulation structure. The system was characterized by
1 General Introduction
subpopulations that occurred in discrete resource patches and individuals dispersed between
patches but such dispersal events were rare (Harrison & Taylor, 1997; Hanski, 1999). Rauch &
Weisser (2007) found parasitism in plants some 192m away from the release plant and
concluded that, even though L. hirticornis could colonize plants at this distance, such events
were rare. Given this seemingly limited dispersal, there was paucity of information on L.
hirticornis population genetic structure.
Roslin (2001) showed, with the specialist dung beetle Aphodius fossor L. (Coleoptera:
Scarabaeidae), that though the spatial population structure was highly aggregated, due to
aggregated distribution of cattle pastures, the genetic structure was strikingly homogenous,
suggesting extensive gene flow and homogenous populations. Johannesen & Seitz (2003) found
higher population genetic sub-structuring of the univoltine oligophagous primary parasitoid,
Eurytoma robusta Mayr (Hymenoptera: Eurytomidae) compared to its univoltine gall forming
fly, Urophora cardui L. (Diptera: Tephritidae). Likewise, Anton et al. (2007) found higher
overall genetic differentiation in the specialist univoltine parasitoid Neotypus melanocephalus
Gmelin (Hymenoptera: Ichneumonidae) compared with its univoltine host, the Dusky large blue
butterfly, Maculinea nausithous Bergsträsser (Lepidoptera: Lycaenidae). In spite of the fact that
they share the same host, the Glanville fritillary butterfly, Melitaea cinxia L., Cotesia
melitearum Wilkinson (Braconidae: Microgastrinae) showed substantial genetic structure
compared with Hyposoter horticola Gravenhorst (Ichneumonidae: Campopleginae) (Kankare et
al., 2005). These four articles (Roslin, 2001; Johannesen & Seitz, 2003; Kankare et al., 2005;
Anton et al., 2007) discuss the importance of dispersal and gene flow on population structuring
in a metapopulation and show that, even in closely interacting species, the population genetic
structure at one trophic level does not necessarily influence the genetic structure of another
trophic level. Population genetic studies are therefore necessary to establish whether L.
hirticornis is influenced by that of its host and possibly the host plant. High population
differentiation in M. fuscoviride has been documented; Massonnet (2002), using six
microsatellite markers on seven subpopulations (five from the Alsace region of France and two
from Germany), reported high population differentiation and of the 21 pairwise F ST
comparisons, 18 were significant.
Massonnet et al. (2002b) found high genetic differentiation among a third of the local
populations of the aphid Macrosiphoniella tanacetaria Kaltenbach (Homoptera: Aphididae) in
Germany, as well as significant deviations from Hardy-Weinberg and linkage disequilibria in
these populations. They concluded that frequent local extinction and colonization events had
created a hierarchical metapopulation structure in the aphid. In host-parasitoid interactions,
2 General Introduction
studies show that parasitoids can cause host extinctions (Lei & Hanski, 1997; Weisser, 2000; van
Nouhuys & Tay, 2001). For example, Weisser (2000) found that the specialist parasitoid, L.
hirticornis caused