Abstract:
The planners of this conference have asked me for a discussion of the interactions
between legumes and herbivores. This is a request for an examination of
traits of legumes as pertains to herbivores. On the one hand, I am happy to do
this because it is a useful sort of focus. On the other hand, I feel it is a bad
move. Such an approach fosters the tendency to search for and accept single
selective pressures as the evolutionary causes of what appear to be single
traits. A single trait, such as the concentration of canavanine in a Dioclea
megacarpa cotyledon or the force to crush an Enterolobium cyclocarpum
seed is no more the result of a single selective pressure than is the number of
times you can open and close your hand in 30 seconds. A single trait, as we
describe it in biology, is simultaneously i) under contemporary design constraints,
ii) a temporal and spatial anachronism, iii) under contemporary
budgetary constraints, iv) multi-functional, and v) optimal (not maximal) in
performance rate and pattern. The huge fruit of Cassia grandis is photosynthetic,
protective against herbivores with a multitude of defenses, heavy,
derived from a minute tissue, expensive per flower, cheap per seed, indehiscent,
toxic when unripe, edible when ripe, and probably was eaten by mastodons.
We are only just now, again, learning to take a single trait of an organism
and simultaneously explore the significance of that trait to that organism's
physiology, anatomy, ecology, behaviour, and so forth. And I worry
that this review may be taken as a digression from such a holistic approach to
understanding form and function. However, while our contemporary research
may be becoming holistic, it is clear that most of what we have to work with
is not, and that much of the day to day data collection is likewise not. I
proceed accordingly.
