We can successfully predict the future arrangements of matter based on knowledge of the laws of physics that govern the interactions between particles. When too many particles exist to make detailed predictions about individual particles, we can use statistical physics to predict generally true and reliable outcomes of the larger system of particles. The 2nd law of thermodynamics provides us with a familiar example of outcomes based on statistical physics. If the future forms of living organisms are predictable, it will likewise be due to the ensemble of their systems of particles obeying fundamental laws of physics. “Evolution” is not a “law of physics” that is independent of or supersedes other known laws of physics.
Organisms respond in similar ways to similar circumstances.
KEY TAKEAWAYS
- Evolution has long been viewed as a largely unpredictable process, influenced by chaotic factors like environmental disruptions and mutations.
- However, researchers have demonstrated cases in some organisms of “replicated radiation,” in which similar sets of traits evolve independently in different regions. Now, researchers report the first evidence for replicated radiation in a plant lineage.
- As biology learns more about phenomena like replicated radiation, we might be able to predict the course of evolution.
Evolution has a reputation for being unpredictable, yet orderly. With mutations and the environment playing huge roles, it seems that predicting which species will evolve which traits is much like guessing the roll of a single die with millions of faces.
However, in some cases, researchers have found that the die rolls the same way again and again. A combination of separate organisms’ natural development and the environmental pressures placed on them can create very similar forms, or ecomorphs. Researchers call this phenomenon replicated radiation. (Sometimes, the term adaptive radiation is used synonymously.)
In a new paper published in the journal Nature Ecology & Evolution, an international group of researchers demonstrated that a plant lineage living in 11 geographically isolated regions independently evolved new species with similar leaf forms. This marks the first example of replicated radiation in plants, and the groundbreaking research gives us more insight into the possible future workings of evolution.
Note: Reason suggests that the development of “similar leaf forms” stems from the fact that they all started from the same “plant lineage.” Furthermore, reason suggests that the original plant lineage had a built-in genomic variability that allowed the variant leaf forms to dominate when environmental pressures favored that form.
The article continues: Different species of Oreinotinus [Viburnum] have different types of leaves. Simply put, some have a large, hair-covered leaf, and others have a smaller, smooth leaf. Originally, experts postulated that both leaf forms evolved early in the group’s history and then dispersed separately through various mountain ranges, carried perhaps by birds. But the distribution pattern of the species, combined with the striking differences in leaf traits, gave researchers an ideal system to explore the possibility that these leaf forms evolved independently across different regions. In other words, they could explore whether this was a case of replicated radiation.
If replicated radiation is occurring, the researchers would expect two key results. First, species in the same area should be more closely related to each other than to species in different regions. Second, similar leaf traits should be present in most areas, but they should evolve independently of one another.
Turning over the same leaf
As Oreinotinus diversified, four major leaf types evolved independently from an ancestral leaf form. The four forms varied in size, shape, margin — that is, whether the edge of the leaf is smooth or toothed — and the presence of leaf hairs. The study grouped the leaves into four types. The researchers also backed up their assessments with a statistical analysis based on these characteristics.
Nine of the 11 areas harbor at least two leaf forms; four areas include three forms; and one, Oaxaca, is home to four. Based on simulations and models, the authors rejected the simple evolutionary model in which the leaf forms evolved before the species dispersed. They also found that chance alone does not likely explain why nine areas of endemism host two or more leaf forms. Based on these lines of evidence, the team concluded that leaf forms evolved separately within multiple regions. The leaf morphs did not originate early in Oreinotinus evolution. Rather, as different lineages diversified within different areas, each lineage “traversed the same regions of leaf morpho-space.”
So what is this clade telling us when it evolves different leaf forms? As it turns out, different leaves provide different advantages that suit particular climate niches. For example, the smaller leaves would allow more precise thermoregulation — the leaf won’t get too hot or too cold as the weather changes. On the other hand, large leaves would be better for lower-light, frequently cloudy environments, because they improve light capture and make photosynthesis more efficient. So the different leaf ecomorphs are adapted to specific sets of subtly different but often adjacent environmental niches.
The future of evolution
Researchers can now add Oreinotinus to an exclusive list of other groups of organisms known to have undergone replicated radiation, such as Anolis lizards in the Caribbean, cichlid fishes in African rift lakes, and spiders in Hawaii.
With a plant on the list, evolutionary biologists know this is not a trend exclusive to animals isolated on islands, where most of the other examples come from. Like island archipelagos, the cloud forest environments of Oreinotinus are separate from one another. A plant example will help evolutionary biologists pinpoint the broad circumstances under which we can make solid predictions about evolution.
Whether it’s Darwin’s finches, Oreinotinus, or a group of sugar-hungry E. coli, we are all subject to the mysterious workings of evolution. But perhaps, as a diverse set of research groups work to tackle the problem, the mystery will fade. As Michael Donoghue, a co-corresponding author of the Oreinotinus study, said in a statement, “Maybe evolutionary biology can become much more of a predictive science than we ever imagined in the past.”
Full article at Big Think.
Predictive success alone does not guarantee the success of a theory of how nature works. Additional consequences of a theory must also make sense and not contradict established laws of nature. Naturalistic evolution still contradicts the principle that natural causes will on average degrade the information content (loss of functional complexity) of a system over time.