We’ve spent some time before discussing the nature of the term ‘species’ and what it means in reality. Of course, answers to questions in biology are always more complicated than we wish they might be, and despite the common nomenclature of the word ‘species’ the underlying definition is convoluted and variable.
To expand on this, we’re going to look at a few different models of how the spatial distribution of populations influences their divergence, and particularly how these factor into different processes of speciation.
What comes first, ecological or genetic divergence?
The order of these two processes have been in debate for some time, and different aspects of species and the environment can influence how (or if) these processes occur.
Different spatial models of speciation
Generally, when we consider the spatial models for speciation we divide these into distinct categories based on the physical distance of populations from one another. Although there is naturally a lot of grey area (as there is with almost everything in biological science), these broad concepts help us to define and determine how speciation is occurring in the wild.
A step closer in bringing populations geographically together in speciation is “parapatry” and “peripatry”. Parapatric populations are often geographically close together but not overlapping: generally, the edges of their distributions are touching but do not overlap one another. A good analogy would be to think of countries that share a common border. Parapatry can occur when a species is distributed across a broad area, but some form of narrow barrier cleaves the distribution in two: this can be the case across particular environmental gradients where two extremes are preferred over the middle.
This can be tricky to visualise, so let’s invent an example. Say we have a tropical island, which is occupied by one bird species. This bird prefers to eat the large native fruit of the island, although there is another fruit tree which produces smaller fruits. However, there’s only so much space and eventually there are too many birds for the number of large fruit trees available. So, some birds are pushed to eat the smaller fruit, and adapt to a different diet, changing physiology over time to better acquire their new food and obtain nutrients. This shift in ecological niche causes the two populations to become genetically separated as small-fruit-eating-birds interact more with other small-fruit-eating-birds than large-fruit-eating-birds. Over time, these divergences in genetics and ecology causes the two populations to form reproductively isolated species despite occupying the same island.
As you can see, the processes and context driving speciation are complex to unravel and many factors play a role in the transition from population to species. Understanding the factors that drive the formation of new species is critical to understanding not just how evolution works, but also in how new diversity is generated and maintained across the globe (and how that might change in the future).
Like many people, from a young age I was obsessed and interested in works of fantasy and science fiction. To feel transported to magical worlds of various imaginative creatures and diverse places. The luxury of being able to separate from the mundanity of reality is one many children (or nostalgic adults) will be able to relate to upon reflection. Worlds that appear far more creative and engaging than our own are intrinsically enticing to the human psyche and the escapism it allows is no doubt an integral part of growing up for many people (especially those who have also dealt or avoided dealing with mental health issues).
The intricate connection to the (super)natural world drove me to fall in love with the natural world. Although there might seem to be an intrinsic contrast between the two – the absence or presence of reality – the truth is that the world is a wondrous place if you observe it through an appropriate lens. Dragons are real, forms of life are astronomically varied and imaginative, and there we are surrounded by the unknown and potentially mythical. To see the awe and mystification on a child’s face when they see a strange or unique animal for the very first time bears remarkable parallels to the expression when we stare into the fantasy of Avatar or The Lord of the Rings.
It might seem common for ‘nerds’ (at least under the traditional definition of being obsessed with particular aspects of pop culture) to later become scientists of some form or another. And I think this is a true reflection: particularly, I think the innate personality traits that cause one to look at the world of fantasy with wonder and amazement also commonly elicits a similar response in terms of the natural world. It is hard to see an example where the CGI’d majesty of contemporary fantasy and sci-fi could outcompete the intrigue generated by real, wondrous plants and animals.
Seeing the divine in the mundane
Although we often require a more tangible, objective justification for research, the connection of people to the diversity of life (whether said diversity is fictitious or not) should be a significant driving factor in the perceived importance of conservation management. However, we are often degraded to somewhat trivial discussions: why should we care about (x) species? What do they do for us? Why are they important?
If we approach the real world and the organisms that inhabit it with truly the same wonder as we approach the fantastical, would we be more successful in preserving biodiversity? Could we reverse our horrific trend of letting species go extinct? Every species on Earth represents something unique: a new perspective, an evolutionary innovation, a lens through which to see the world and its history. Even the most ‘mundane’ of species represent something critical to functionality of ecosystems, and their lack of emphasis undermines their importance.
The biota of Earth are no different to the magical fabled beasts of science fiction and fantasy, and we’re watching it all burn away right in front of our eyes.