The Elements of Evolution (51-3) Plant Life-History Variables


The ideal plant design would depend strongly on what other plant species were doing. ~ English botanist Michael Crawley

Plants have their own life-history variables, manifest by their tailoring for the specific habitats to which they are adapted. The more extreme biomes, such as deserts, rain forests, and the polar regions, result in a remarkable degree of evolutionary convergence.

Conversely, areas with temperate climate are typically home to a vast diversity of coexisting vascular plants, each with its own life history. There is marvelous diversity in the growth regimes of plants. Genotypic changes can be passed on in any part of a plant. This demonstrates the difficulty of readily categorizing a spectrum of floral life-history facets as can be done with animals.

Plants vary not just in their pace of life, but also in their reproductive output and frequency of reproduction. ~ English ecologist Dave Hodgson

Small plants generate seeds as often as the odds are that some of the next generation may survive. That said, many annuals adopt a mixed strategy for their seeds of intended destination and the precise conditions under which their seeds will attempt their start in life.

The calculus changes when competition toughens. To forge their spot in the Sun, trees delay investment in reproduction until they have gained enough girth to ensure their own survival over a protracted period. Only then do they devote resources to reproduction, but strictly when a plant thinks its offspring may fare well: during times of high productivity, in years of good weather for pollination, or when herbivores are scarce. Trees unable to obtain a place in the canopy usually die without leaving any progeny at all.

One life-history-variable commonality plants share with animals is relative size. Short plants live in the evolutionary fast lane. Short plants have up to 5 times the adaptive ability of tall ones. Growth rate makes the difference. Small plants grow faster.

Taller plants have lower rates of molecular evolution. ~ English evolutionary biologist Robert Lanfear et al