Tritrophic Interactions and the Evolution of Diet Breadth in Insect ...

Tritrophic Interactions and the Evolution
of Diet Breadth in Insect Herbivores
John T. Lill
Department of Biological Sciences

3 rd (Carnivores)
-
+
2 nd (Herbivores)
-
1 st (Producers)

Plants as Protection
The Devil and the Deep Blue Sea
“Plant-feeding insects live in a world dominated
on the one hand by their natural enemies and on
the other by a sea of food, that at best, is often
nutritionally indadequate and, at worst, is simply
poisonous” (Lawton and McNeil, 1979)
Recognized that for many insects, choice of host plant
(individual or species) may have important repercussions
for its risk of attack by enemies

Ecological Tradeoff
Fitness in the presence of enemies
Low quality, Low risk
High quality, High risk
Fitness in the absence of enemies

Euclea delphinii development time
90
80
Mean days to maturation
70
60
50
40
30
20
10
0
Green
Ash
White
Oak
Hickory Beech Black
Gum
Red Oak Cherry Black
locust
Redbud
ANOVA:
F 7,83 = 14.08; P < 0.0001

100
80
Host plant-specific Parasitism
Adoneta
Isa
Isochaetes
Lithacodes
Prolimacodes
Parasitism (%)
60
40
20
0
Beech White oak Red oak
Host Plant