A long-term 10 year active, field study has revolutionized our understanding of evolution on Lizard Island in Florida in real time

Recommendable! A remarkable study! How does natural selection actually work. How changing circumstances drive evolution.

"... Now spanning 10 years, 10 generations and five species, our Lizard Island dataset represents one of the longest-running active studies of its kind in evolutionary biology. By tracking which individuals survive and reproduce, and linking their success to specific physical traits and performance abilities, we’re documenting natural selection with unprecedented detail.

So far we have uncovered two fascinating patterns. Initially, it didn’t pay to be different on Lizard Island. Anoles with very average shapes and sizes lived longer compared with those that are slightly different. But when the crested anoles arrived, everything changed: Suddenly, brown anoles with longer legs had a survival advantage. ...

By watching natural selection unfold in response to environmental changes, rather than inferring it from fossil records, we’re providing cutting-edge evidence for evolutionary processes that Charles Darwin could only theorize about. ..."

From the abstract (1):

"From experimental evolution in the laboratory to sustained measurements of natural selection in the wild, long-term studies have revolutionized our understanding of evolution. By directly investigating evolutionary dynamics in real time, these approaches have provided unparallelled insights into the complex interplay between evolutionary process and pattern. These approaches can reveal oscillations, stochastic fluctuations and systematic trends that unfold over extended periods, expose critical time lags between environmental shifts and population responses, and illuminate how subtle effects may accumulate into significant evolutionary patterns. Long-term studies can also reveal otherwise cryptic trends that unfold over extended periods, and offer the potential for serendipity: observing rare events that spur new evolutionary hypotheses and research directions. Despite the challenges of conducting long-term research, exacerbated by modern funding landscapes favouring short-term projects, the contributions of long-term studies to evolutionary biology are indispensable. ... In this Review article, we showcase the groundbreaking discoveries of long-term evolutionary studies, underscoring their crucial role in advancing our understanding of the complex nature of evolution across multiple systems and timescales."

From the significance and abstract (2):

"Significance

Stabilizing selection has been widely invoked to explain why many species’ phenotypes experience little to no change through time. However, microevolutionary field studies have revealed that stabilizing selection is very rarely detected in natural populations. Here, we show that species’ phenotypes can be maintained through time in the absence of consistent stabilizing selection that continually favors a central optimal phenotype. Instead, species are maintained on fitness peaks through the accumulation of selection that fluctuates in form, strength, direction, or existence through many independent time periods. In multispecies communities, this accumulation of selection creates a rugged community-wide fitness landscape on which different species occupy divergent adaptive peaks separated by fitness valleys that reinforce species distinctness through time.

Abstract

Species’ phenotypic characteristics often remain unchanged over long stretches of geological time. Stabilizing selection—in which fitness is highest for intermediate phenotypes and lowest for the extremes—has been widely invoked as responsible for this pattern. At the community level, such stabilizing selection acting individually on co-occurring species is expected to produce a rugged fitness landscape on which different species occupy distinct fitness peaks. However, even with an explosion of microevolutionary field studies over the past four decades, evidence for persistent stabilizing selection driving long-term stasis is lacking. Nonetheless, biologists continue to invoke stabilizing selection as a major factor explaining macroevolutionary patterns.

Here, by directly measuring natural selection in the wild, we identified a complex community-wide fitness surface in which four Anolis lizard species each occupy a distinct fitness peak close to their mean phenotype. The presence of local fitness optima within species, and fitness valleys between species, presents a barrier to adaptive evolutionary change and acts to maintain species differences through time. However, instead of continuously operating stabilizing selection, we found that species were maintained on these peaks by the combination of many independent periods among which selection fluctuated in form, strength, direction, or existence and in which stabilizing selection rarely occurred. Our results suggest that lack of substantial phenotypic evolutionary change through time may be the result of selection, but not persistent stabilizing selection as classically envisioned."

From the abstract (3):

"Ecological character displacement, whereby shifts in resource use in the presence of competing species leads to adaptive evolutionary divergence, is widely considered an important process in community assembly and adaptive radiation. However, most evidence for character displacement has been inferred from macro-scale geographic or phylogenetic patterns; direct tests of the underlying hypothesis of divergent natural selection driving character displacement in the wild are rare. Here, we document character displacement between two ecologically similar lizards (Anolis sagrei and A. cristatellus) experiencing novel contact. We identify directional selection during the incipient stages of sympatry in a new community that corresponds to repeated trait divergence across multiple established sympatric communities. By identifying the role of natural selection as character displacement unfolds, we connect how natural selection operating at short timescales may drive broader patterns of trait distributions at larger spatial and temporal scales."

Amid a tropical paradise known as ‘Lizard Island,’ researchers are cracking open evolution’s black box – scientist at work

Long-term studies provide unique insights into evolution (1) (no public access)

Fluctuating selection maintains distinct species phenotypes in an ecological community in the wild (2) (open access)

Observing character displacement from process to pattern in a novel vertebrate community (3) (open access)

Fig. 1 Anolis lizard study community.