Data from: Landscape variation in defense traits along gradients of multiple resources in a tropical savanna plant

Many plant species are widely distributed and consequently are exposed to
multiple abiotic factors and diverse herbivores, each of which may
distinctly affect the magnitude of different defense
traits. Alternative theories for optimal allocation to plant
defense traits predict both positive and negative associations between
magnitude of defense and resource availability. These predictions may
apply even within species. This suggests potential for a single species‘
patterns of association of defense traits and resources to vary with both
the type of defense and identity of resource, but relatively few studies
have explored intraspecific variation in multiple defense traits along
several resource gradients simultaneously. In order to address this gap,
especially in an ecosystem dominated by large mammalian herbivores, we
assessed relationships between multiple resources (rainfall, soil N, and
soil P) and plant defense traits (prickle density, phenolics, and lignin
content) using a widely distributed tropical savanna herb, Solanum
incanum, growing in naturally occurring resource gradients within the
Serengeti National Park. We found substantial intraspecific variation in
all three defense traits across sites (n =43). Variation in prickle
density was positively associated with rainfall and soil P, but not soil
N. In contrast to prickle density, phenolics and lignin were uncorrelated
with all three resource gradients. This independent association of soil P
with a carbon-based defense, prickle density, suggests potential for
resources that are not components of defenses to influence allocation to
defense traits. Such influence may reflect association between resource
and herbivore abundance and/or preference. These varied patterns in
resource-defense associations further emphasize the tremendous variation
in anti-herbivore traits which may be influenced by different plant
resources and highlight the need to consider multiple resource gradients
in understanding evolution of plant traits.