Climate change is not new to penguins. Their bodies are extremely adapted for some of Earth's most harsh situations since their life history has been sculpted by increasing and declining temperatures.
However, due to what seems to be the lowest evolutionary rates ever found in birds, experts are afraid that the evolutionary trajectory of the penguin may be coming to a standstill.
One of the most thorough analyses of penguin evolution to date, which is the first to incorporate information from both extant and extinct penguin species, has just been released by a group of worldwide researchers.
The study reveals the turbulent life history of penguins in general, with three-quarters of all species currently only being recorded by fossils.
These recognizable birds have evolved into highly specialized marine predators over a period of 60 million years and are now well suited to some of the most severe habitats on Earth, according to the scientists.
They currently serve as sentinels emphasizing the fragility of cold-adapted animals in a rapidly warming planet, however, as their evolutionary history demonstrates.
With their ungainly shuffle and apparently pointless wings, penguins might seem a little ludicrous while on land. However, when they are submerged, their bodies change into hydrodynamic torpedoes that would make any fish trying to escape wish it could fly.
Before the polar ice sheets formed 60 million years ago, penguins had already given up flying in favor of wing-propelled diving.
The distinctive characteristics that permit penguins' aquatic lives appear to have evolved early in the group's history, with rates of evolutionary change usually going downward through time, according to fossil evidence and genetic data.
The Gondwanan microcontinent known as Zealandia, which is now largely buried under the water, is where experts believe penguins first evolved.
The article hypothesizes that crown penguins, the progenitors of contemporary penguins, appeared around 14 million years ago, or 10 million years after genetic tests have shown.
This phase would fall within the middle Miocene climate transition, a period of worldwide cooling. However, within the last 3 million years, several genetic lineages of living penguins have diverged.
Before repeatedly dispersing to South America and Antarctica, penguins dispersed over Zealandia. Later groups are thought to have taken a ride on the Antarctic Circumpolar Current.
The researchers discovered that during the Last Glacial Period, practically all penguin species went through a period of physical isolation.
During this period, groups were compelled to dwell in more dispersed habitat regions farther north where they could still obtain food and shelter, limiting their interaction with other penguin species.
As a result, each group's DNA pool shrank, further separating species genetically.
They went back towards the poles during the subsequent warming phase, and some groups—now considerably more genetically distinct—came into contact with one another once more.
It provides insight on how some groups of penguins could adapt to climate change induced by humans based on how they experienced these major climate events.
The groups that multiplied as the climate warmed all had the traits of being migratory and foraging offshore. The capacity to look farther out for prey and to relocate to lower latitudes are two characteristics that the researchers believe helped them adapt to shifting climates more effectively.
On the other hand, those who became fewer in number tended to dwell in one location and hunt for food closer to the coast—a way of life that doesn't fare well when the circumstances "at home" change significantly.
But penguins' capacity for change may be constrained by factors more than merely way of life; these factors appear to be ingrained in their DNA.
It turns out that penguins and their sister order, Procellariiformes, which includes birds like petrels and albatrosses, have the lowest evolutionary rates ever seen in bird species.
Using a number of genetic characteristics strongly associated to rates of evolutionary change, the researchers evaluated an aggregate 17 distinct orders of birds.
They discovered that aquatic birds often evolved more slowly than their terrestrial relatives, and they hypothesize that adopting an aquatic lifestyle may be associated with sluggish evolution. They also believe that birds evolve more slowly in colder areas.
Waterfowl (order Anseriformes) had far lower rates than earthbound fowl like turkeys, chickens, and quails. The order Pelecaniformes, which includes seabirds like pelicans and cormorants, was close to third for lowest evolutionary rate (order Galliformes).
Even while the researchers point out that the ancestor crown penguins developed more quickly than current penguins, this process was nonetheless sluggish in comparison to other birds.
According to biologists, the sluggish rates of evolution and specialized lifestyles of half of the extant penguin species might lead to the species' extinction.
Penguins' capacity for adaptation will probably be significantly outstripped by the present speed of warming paired with the Southern Ocean's few refugia, the authors write.
As penguin populations in the Southern Hemisphere deal with fast human climate change, the hazards of future collapses are always there.
This research was published in Nature Communications.
