been extensively tested within populations and along phylogenies. Common
patterns found indicate that plants and herbivores constitute a selective context
for each other, and that plant secondary metabolites are adaptations that constraint
phytophagous insects to use a plant as a host or as a food source. Herbivorism is
strongly implicated in the evolution of specialized associations that are usually
mediated by a conserved biochemical machinery of host plants. The evolution of
specialism appears to be correlated to speciation events and even with adaptive
radiations. However, there is little evidence that these correlations reflect a causal
relationship. Perhaps the most compelling evidence linking macroevolutionary
patterns and mechanisms that produce new species is the matching of the genetic
machinery responsible for the evolution of chemical novelty on plants and major
emergency events of plants and herbivore lineages. This body of work developed
from the study of the antagonistic association of plants and herbivores in more
than 60 years has evince the great potential of adaptive evolution to generate
much of the Earth’s biodiversity.
Keywords
Adaptive evolution · Plant defense · Coevolution · Herbivory · Secondary
metabolites · Antagonistic interactions · Diversification
1
Introduction
Why is there such a large diversity of secondary metabolites produced by plants?
And, why relationship between numerous taxa of plants and animals is constant?
Both are questions that, from entomology to chemical ecology, and from evolutionary biology to genetics, have been linked in the effort to be answered for many
decades. Already in the late nineteenth century, the botanist Ernst Sthal had
documented that secondary metabolites (i.e., compounds not involved in the primary
metabolism) produced by plants provide them protection against herbivores [154].
Although some evidence of the ecological role of plant secondary metabolites was
collected over the early twentieth century (e.g., [27]), the hypothesis of the defensive
function of plant compounds was formally introduced by mid 1950s (see [39, 40,
62]), replacing the previous conception of secondary metabolites as “waste products” of the primary metabolism. Framed on this adaptive notion, several models
were elaborated, mainly based on the effects of plants’ compounds on organisms and
the environment, and on the comparison of their distribution and the phylogenetic
relationships of plants that produced them. Theory of plant-herbivore coevolution, in
particular the model of “escape and radiation” [48], has provided for the last decades
an articulated framework for the study of plant and arthropods codiversification. This
model has also contributed to the development of hypothesis that attempt to explain
both the phytochemical diversity and the longstanding associations of plants and
animals which lead in some cases to specialization habits. In essence, the model
proposes that sequential responses to selection pressures exerted by plants and their
48
E. Kariñho-Betancourt
patterns found indicate that plants and herbivores constitute a selective context
for each other, and that plant secondary metabolites are adaptations that constraint
phytophagous insects to use a plant as a host or as a food source. Herbivorism is
strongly implicated in the evolution of specialized associations that are usually
mediated by a conserved biochemical machinery of host plants. The evolution of
specialism appears to be correlated to speciation events and even with adaptive
radiations. However, there is little evidence that these correlations reflect a causal
relationship. Perhaps the most compelling evidence linking macroevolutionary
patterns and mechanisms that produce new species is the matching of the genetic
machinery responsible for the evolution of chemical novelty on plants and major
emergency events of plants and herbivore lineages. This body of work developed
from the study of the antagonistic association of plants and herbivores in more
than 60 years has evince the great potential of adaptive evolution to generate
much of the Earth’s biodiversity.
Keywords
Adaptive evolution · Plant defense · Coevolution · Herbivory · Secondary
metabolites · Antagonistic interactions · Diversification
1
Introduction
Why is there such a large diversity of secondary metabolites produced by plants?
And, why relationship between numerous taxa of plants and animals is constant?
Both are questions that, from entomology to chemical ecology, and from evolutionary biology to genetics, have been linked in the effort to be answered for many
decades. Already in the late nineteenth century, the botanist Ernst Sthal had
documented that secondary metabolites (i.e., compounds not involved in the primary
metabolism) produced by plants provide them protection against herbivores [154].
Although some evidence of the ecological role of plant secondary metabolites was
collected over the early twentieth century (e.g., [27]), the hypothesis of the defensive
function of plant compounds was formally introduced by mid 1950s (see [39, 40,
62]), replacing the previous conception of secondary metabolites as “waste products” of the primary metabolism. Framed on this adaptive notion, several models
were elaborated, mainly based on the effects of plants’ compounds on organisms and
the environment, and on the comparison of their distribution and the phylogenetic
relationships of plants that produced them. Theory of plant-herbivore coevolution, in
particular the model of “escape and radiation” [48], has provided for the last decades
an articulated framework for the study of plant and arthropods codiversification. This
model has also contributed to the development of hypothesis that attempt to explain
both the phytochemical diversity and the longstanding associations of plants and
animals which lead in some cases to specialization habits. In essence, the model
proposes that sequential responses to selection pressures exerted by plants and their
48
E. Kariñho-Betancourt