Like many “Nerds by Profession” (scientists), much of my love for evolutionary biology as a young kid was fostered by an amazing diversity of creatures, both real and fictional. A formative influence in the latter category for me was through gaming – while I hold love for many great gaming franchises, the Nintendo series Pikminholds a special place in my heart. The series of puzzle-cross-strategy games primarily following the misadventures of diminutive space explorer Captain Olimar, who crash lands on what is heavily implied (and later confirmed) to be a post-human Earth (or PNF-404, as it’s known). There, he is greeted by a strange plant-like species called Pikmin, who assist him in repairing his ship or collecting treasure (depending on the game). The Pikmin games require a certain degree of strategy, planning and time-efficiency in order to complete the necessary tasks within the limited timeframe of the game (or individual day).
One of the most obvious ways the evolution of two different species can interact is in predator and prey relationships. Naturally, prey species evolve to be able to defend themselves from predators in various ways, such as crypsis (e.g. camouflage), toxicity or behavioural changes (such as nocturnalism or group herding). Contrastingly, predators will evolve new and improved methods for detecting and hunting prey, such as enhanced senses, venom and stealth (through soft-padded feet, for example).
The pine marten is a species in the mustelid family, along with otters, weasels, stoats, and wolverines. Like many mustelids, they are carnivorous mammals which feed on a variety of different prey items like rodents, small birds and insects. One of the more abundant species that they prey upon are squirrels: both red squirrels and grey squirrels are potential food for the cute yet savage pine marten.
In a similar vein to predator and prey coevolution, pathogenic species and their unfortunate hosts also undergo a sort of ‘arms race’. Parasites must keep evolving new ways to infect and transmit to hosts as the hosts evolve new methods of resisting and avoiding the infecting species. This spiralling battle of evolutionary forces is dubbed as the ‘Red Queen hypothesis’, formulated in 1973 by Leigh Van Valen and used to describe many other forms of coevolution. The name comes from Lewis Carroll’s Through the Looking Glass, and one quote in particular:
‘Now, here, you see, it takes all the running you can do, to keep in the same place’.
Plenty of other strange and unique mechanisms of coevolution exist within nature. One of them is mimicry, the process by which one species attempts to look like another to protect itself. The most iconic group known for this is butterflies: many species, although they may be evolutionarily very different, share similar colouration patterns and body shapes as mimics. Depending on the nature of the copy, mimicry can be classified into two broad categories. In either case, the initial ‘reference’ species is toxic or unpalatable to predators and uses a type of colour signal to communicate this: think of the bright yellow colours of bees and wasps or the red of ladybirds. Where the two categories change is in the nature of the ‘mimic’ species.
Coevolution of species and the importance of species interactions
There are countless of other species interactions which could drive coevolutionary relationships in nature. These can include various forms of symbiosis, or the response of different species to ecosystem engineers: that is, species that can change and shape the environment around them (such as corals in reef systems). Understanding how a species evolves within its environment thus needs to consider how many other local species are also evolving and responding in their own ways.