How plants affect the evolution of animals
The very base of the food chain is occupied by plants, which use sunlight directly. These primary producers then become nourishment for the primary consumers, and indirectly for all other organisms, up to the superpredators.
The fact that plants are at the base, implies that almost all other living beings depend on them, as well as the course of their evolution.
This is also due to the fact that the generational turnover of plants is extremely long compared to that of the vast majority of animals, and therefore the mutations, and their relative spread in a population is much slower, and it wouldn’t be able to keep up and react to the evolution of the consumers. Indeed, the very opposite is true: it is other animals that generally adapt to plants.
The different varieties of plants become different kinds of food for which different species specialize (like browsing and grazing herbivores).
The amount of plant biomass also regulates the size of the populations of all other organisms: constant rainfall and abundant light, which is what plants need, make the tropics an ecosystem teeming with highly diverse life forms, while at the poles the lack of sunlight supports far fewer herbivores (both in terms of species and population) and even fewer carnivores.
An animal that feeds on grass can afford not to compete with one that feeds on leaves, shrubs or fruit: offering different ways to feed and new shelters, multiplies the available ecological niches that consumers can occupy, and incentivizes them to diversify.
The most important mutations in the history of plant evolution have always heavily influenced the animals that lived at that time:
- The purpose for which fruits evolved is to use the animals that feed on them to spread the seeds more efficiently. Plants have encouraged animals to collaborate by rewarding them with a meal rich in easily digestible sugars, which has also modified their digestive systems (while previously they had to feed on the rest of the plant, which is energetically very expensive to digest) and made available ecological niches that also include that of primates.
- Another crucial point was the evolution of vascular plants, where the presence of cellulose provided the stiffness necessary to make very tall trees possible, which in turn created a new three-dimensional habitat for life on land.
- Another great explosion of diversity in the animal world was caused by the evolution of flowers as a reproductive mean. With the birth of the angiosperms, which then took over the gymnosperms (which reproduced without flowers) social insects and many other animals were born.
- The extinction of ferns and cycads, the dominant trees back then, and the development of broad-leaved trees is one of the factors that led to the extinction of large reptiles and allowed mammals to thrive.
- And obviously, the oxygen that today is used by almost all organisms on Earth was produced by plants, which were also the first beings to colonize the surface and make it habitable for other animals.
It is therefore clear that it is plants that affect animals, not the other way around.
So far we have talked about the changes that have already occurred to animal evolution due to plants, but it is very likely that future mutations that will prove beneficial will give birth to entire groups of new animals (It already happened with terrestrial creatures first and with social insects and mammals then), so much so that it would be very difficult to make predictions.
It is plausible that the next mutations will introduce improvements in the reproductive strategy of plants.
A hypothesis put forward by Dougal Dixon in the book After Man is that of a plant that is fertilized in a normal way, but whose fruit does not fall even when ripe, instead starting to develop on the mother plant itself until a herbivore with the necessary anatomical characteristics moves it to an area more exposed to the sun where it can finally grow and reach sexual maturity.
It’s clear that this is only a very speculative example, but the concept is that a change of this caliber in plants would induce the birth of a whole range of animals with modified digestive and reproductive tracts, and even sensory organs, habits and intelligence different from the usual, along with new habitats and materials.
Usually the less specialized animals of the dominant groups (such as rodents in mammals or crows in birds) and those with a smaller size are the ones that take advantage of this kind of opportunity.
Opportunities so new and unusual that have the potential to create animals that will seem as distant from mammals as mammals today are from reptiles or amphibians.