The effect of human activity on the natural world is profound, and if we want to gain a complete understanding of how it is altering the biosphere, then examining speciation is important.
We know that speciation does exist, and so does human-induced speciation. If we want to use biodiversity as a measure of our impact on the biosphere, then surely speciation needs to be considered.
Speciation can occur rapidly, and is not necessarily slower than extinction, so it is certainly relevant.
It is often said that we are living through one of our planet’s great mass extinction events, and that the cause is humanity. This loss of biodiversity is tragic not only for how it can and will affect our physical well being, but also for how it seems to make the world a poorer place to live in aesthetically and emotionally.
But while human activity can lead to the decline and extinction of species, it can also lead to the emergence of new species. From domestication to the creation of new ecosystems, human activity has proven an effective driver of speciation. But there is little data to quantify this phenomenon, and it is largely overlooked when discussing humanity’s impact on the natural environment.
What separates similar populations into distinct species is, of course, not always clear, but the road to speciation can be understood well enough. When a species becomes divided into different populations that cannot interbreed, and when new selection pressures are apparent, separate populations can begin to develop new traits and make steps towards speciation. Human activity has done much to create barriers to breeding, and to create new selection pressures.
Creating new species
Many of the ways in which humans can drive speciation are the same ways that humans drive extinction. The introduction of species to new habitats is one example. Invasive species can out-compete natives and drive them to extinction. But the new environment in which animals and plants find themselves, and their isolation from other populations, can encourage morphological changes to develop, as well. Data from an Australian study found that 70 percent of introduced plants had developed a new morphological trait over 150 years. On top of that, invasive species introduce new pressures on native species, which can also encourage them to change.
Domestication is perhaps the most obvious way in which humans have promoted genetic diversity. Wolves have been bred into over 400 varieties of domestic dog, and the range of crops bred by humans includes many that can be regarded as totally separate species.
Anthropogenic climate change is altering environments across the globe and creating new selection pressures. There is even evidence to show it has increased biodiversity on mountaintops. Rates of genetic change in populations hunted by humans have been shown to be greater than for populations that are not hunted.
In the future, the possible recreation, or de-extinction, of animals such as the wooly mammoth, and even the movement of organisms to extra-terrestrial bodies such as Mars, could create further opportunities for speciation. There seems no end to humanity’s power as a force for evolution.
So what, if anything, does this mean for conservation?
The effect of human activity on the natural world is profound, and if we want to gain a complete understanding of how it is altering the biosphere, then examining speciation is important. We know that speciation does exist, and so does human-induced speciation. If we want to use biodiversity as a measure of our impact on the biosphere, then surely speciation needs to be considered. Speciation can occur rapidly, and is not necessarily slower than extinction, so it is certainly relevant.
Considering speciation leads us to a number of questions. Should we consider only species loss, or net species loss, when thinking about biodiversity? Can human-induced speciation compensate for human-induced extinctions? If we are creating as many new species as we are destroying, then should we be content? The answer most people would give to this last question is almost certainly ‘no.’
The one property of a species that is not quantifiable in a simple number is the meaning it has for people. When we look at an animal, it is not just its physical properties that are important, but the impression it makes upon us. The very idea of biodiversity has emotional meaning to people, such that any loss of species, even if countered by the introduction of new species, is usually seen as tragic.
What this says about the value we place on a species, and the reasons we value biodiversity, is perhaps something that ought to be discussed.
This article was inspired by a study recently published in the Proceedings of the Royal Society B.
- Bull, J. W., & Maron, M. (2016, June). How humans drive speciation as well as extinction. In Proc. R. Soc. B (Vol. 283, No. 1833, p. 20160600). The Royal Society. doi:10.1098/rspb.2016.0600
- Buswell, J. M., Moles, A. T., & Hartley, S. (2011). Is rapid evolution common in introduced plant species?. Journal of Ecology, 99(1), 214-224. doi:10.1111/j.1365-2745.2010.01759.x
- Stenseth, N. C., & Dunlop, E. S. (2009). Evolution: unnatural selection. Nature, 457(7231), 803-804. doi:10.1038/457803a
- Walther, G. R., Beißner, S., & Burga, C. A. (2005). Trends in the upward shift of alpine plants. Journal of Vegetation Science, 16(5), 541-548. doi:10.1658/1100-9233(2005)16[541:TITUSO]2.0.CO;2