An empirical experiment confirms a new hypothesis on the evolution of life
Many theories and hypotheses suggest that competition tends to differentiate ecological requirements after repeated interactions and allows biodiversity. Even if the mechanisms that allow species to evolve, coexist, compete, cooperate, or become extinct are becoming more and more understood, the factors that allow species to coexist in a given time within the same environment are still debated. From Gause’s principle of competitive exclusion to Connell’s ghost of competition in the past, the importance of intra- and interspecific competition for the evolution of biodiversity has been stressed. Recently, the principles based on competitive interactions for the explanation of biodiversity have been criticized from both theoretical and empirical approaches. Since Hutchinson proposed the provocative “paradox of plankton” a series of alternative hypothesis has been proposed to explain why the principle of competitive exclusion is not found in “real nature”. The reason probably lies in the fact that ecologists have not questioned some of the principles of evolution. In fact, most ecological models are too simplistic and are often considered outdated.
A new conceptual evolutionary model first proposed in 2015 in bioRXiv and then published this year in the journal Biologia by Roberto Cazzolla Gatti, associate professor of ecology and biodiversity at Tomsk State University (Russia), reviewed the debated mechanism of speciation, suggesting that competition and a struggle for the existence are not the main drivers of evolution. This research points out the importance of avoidance of competition, biological history, endogenosymbiosis, and three-dimensionality as the main forces that structure ecosystems and allow the evolution of biological diversity.
This model remained a theoretical and hypothetical, but intriguing, explanation for less than a year. A few weeks ago, researchers from the University of Bern in Switzerland published an empirical experiment that proves it. David Marques and colleagues demonstrated that a population of stickleback fish that breed in the same lake (Lake Constance, where they were introduced around 150 years ago) was splitting into two separate species before their eyes, and at rapid speed. The study shows that even if both types of fish breed in the same streams at the same time of year and have been interbreeding all along, they are splitting into two genetically and physically different types.
“It has been argued that true sympatry may not exist in nature, or can be – at least – genetically constrained – wrote Roberto Cazzolla Gatti in his paper (Cazzolla Gatti R., A conceptual model of new hypothesis on the evolution of biodiversity, Biologia, 71(3), 343-351, 2016) – This is because small variations in the microhabitat preference can still create allopatry and recent investigations in habitat suitability studies seem to reveal these differences. But if we consider sympatry as a spatial variable, the ‘microhabitat preferences’ are not properly sympatric but instead represent a niche displacement. I suggest that sympatric speciation should be reconsidered as one of the main mechanisms that lead to species coexistence and to the evolution of biodiversity. In fact, if interspecific competition and the principle of competitive exclusion between different meta-populations (and then, species) were to take place, probably the coexistence of different species would never realize. We would see rather the survival of the most efficient one (which accumulates enough mutation to adapt and not to differentiate) and the extinction of the ancestor or those species belonging to other phyletic lines. My model predicts that the coexistence of two species in a sympatric way can happen only if there is low competition or weak competitive exclusion between them and a kind of avoidance of competition that leads to a slight shift of the niche of a meta-population, which accumulated a series phenotypic difference due to genomic inclusions coming from other sources of genes. Thus, eventually, it’s the avoidance of competition and the process that I call endo-geno-symbiosis (i.e., the capacity of endogen ‘gene carriers’ to share parts of their genome in a symbiotic relationship with their hosts, after the idea of ‘endosymbiosis’ proposed by Sagan, 1967) that drives the expansion of the diversity of living beings. Competition and mutation (i.e., the classic idea of natural selection), on the other hand, lead to preserving and adapting species and not to diversifying them. This confirms what has been previously suggested: in reality we cannot attend the competition in the present since all niches of the relevant species in an ecosystem seem to be unique and different, even though overlapping on various degrees.”
There are numerous examples of rapid evolution, from cancers becoming resistant to drugs to pests becoming resistant to pesticides. Even some species of fish are evolving smaller to avoid being fished. This very rapid evolution through sympatry, thanks to the avoidance of competition, may be the norm rather than the exception.
Marques and colleagues wrote: “We cannot know for sure that the Lake Constance sticklebacks will continue evolving until they become two non-interbreeding specie. But evidence for sympatric speciation is growing, from mole rats in Israel to palms on Lord Howe Island, Australia, and apple maggots evolved from hawthorn maggots in North America, leading some evolutionary biologists to think it could be surprisingly common.”
Roberto Cazzolla Gatti, who began to be interested in the role of cooperation in evolution since 2011, when he published a controversial paper titled “Evolution is a cooperative process: the biodiversity-related niches differentiation theory (BNDT) can explain” concluded: “These theoretical findings, confirmed by empirical approaches, should motivate our species to think before it is too late about how human competition, for the first time in the history of life on Earth, has been systematically leading to the extinction of animals and plants. My new model of evolution does not only attempt to explain some of the mechanisms that underlie the current presence of the myriad forms of life, but it also sheds new light on the need of periods of sufficient time scale to generate the awesome number of species that currently inhabit our planet. If humanity does not stop its ‘unnatural’ competitive spirit in the massive elimination of species, more billions of years could be needed before the diverse set of living beings that we now call biodiversity can be regenerated. And the extinguishing power of the sun will not allow it.”
ORIGINAL JOURNAL ARTICLE: http://dx.doi.org/10.1515/biolog-2016-0032