165 years later it turned out: Darwin (again) was right (roughly)

On February 12 of each year, “Darwin Day” is celebrated around the world, marking the birthday of the father of evolution, Charles Darwin. Many of Darwin’s hypotheses have received extensive scientific support in the many years since he conceived them, but one of them, known as the “wind hypothesis” which he developed about 165 years ago, remains only a reasoned hypothesis to this day. really.

According to this hypothesis, wingless insects are able to thrive better on islands where the winds are stormy than insects with wings, because winged insects can drift in flight in the powerful wind current during storms. Darwin’s arguments for hypothesis were somewhat lacking, but recently researchers have finally been able to prove his point.

The question of what environmental pressures determine whether a particular species of insect will develop wings or not has long intrigued scientists. Darwin first thought of the issue in January 1831, while visiting Madeira, an island belonging to Portugal and located off the coast of Morocco. Following a cruise around the island’s shores, Darwin noticed something strange: many local beetles were wingless. He suggested that if the wingless beetles were able to fly, they would be flown off the island during a flight by the strong winds that prevailed in the place. Therefore, he hypothesized that wingless beetles are more adapted to this environment – and therefore, as evolutionary theory dictates, survive more.

“The development of insect wings has enabled them to reach many new niches and settle various habitats,” says Dr. Jonathan Marsman, a researcher at the Steinhardt Museum of Nature and the Tel Aviv University School of Zoology under the guidance of Dr. Neta Dorchin and Dr. Gal Rybak. “The wings allowed the insects to get further, and to adapt to the new environment.”

In the new study, the researchers examined data collected over three decades on the different characteristics of many insects, the stability of their habitats and the prevailing climate (micro-climate). The researchers focused on different species of insects that live in Antarctica and 28 islands in the Southern Ocean (located about halfway between Antarctica and Australia), and which are considered to be some of the most turbulent places on Earth.

The researchers found that about 47 percent of the insect species that developed in the areas studied did not have wings. This is an unusual number – almost ten times the world prevalence of wingless insects, which stands at about 5 percent. They found that the strong winds in these areas, as well as the low air pressure and freezing temperatures, made the flight almost impossible for the local insects.

However, the researchers also found that although his hypothesis was verified, Darwin was completely wrong – because he believed that evolutionary adjustments stemmed solely from the strength of the winds in islands that could fly insects flying far into the ocean, while the researchers found that in addition to direct wind influence The insect flight is more difficult to perform and more “expensive” and energetic, leaving less flying insects left to find mates, mate, produce healthy sperm, produce eggs and produce offspring. Thus, active wingless insects that stopped investing energy in flight operation and maintaining their energy-consuming “machines” (the wings, on their developed muscles), gained an advantage, and were able to divert these resources, including reproduction, and thus become unusually dominant in this environment.

“Aviation is definitely a very‘ expensive ’traffic route,” Marsman says. “This is an unstable movement, and a lot of energy is needed to maintain stability and directionality in the air. On the other hand, it is efficient in terms of utilizing time and space.”

The flight characteristics and wings of insects influence and are greatly influenced by their lifestyle, the environment in which they live and their evolutionary needs. For example, a study by Marsman examines how the structure of the wings and the flexibility it gives them are related to the flight style of the Scarabaeidae, a diverse group of beetles to which most species called “garbage beetles” belong.

“At one end of the specialized scale of manure there are beetles that feed on animal droppings, and fly to the vicinity of the food source but look for it while walking on the ground, and at the other end there are manure that feeds on pollen, which should land very precisely on the flowers,” says Marsman. “That is, adjustments are needed in the beetle flight so that they can reach the type of food they consume and utilize it in the most accurate way.”

The research success in proving Darwin’s hypothesis is significant because it is another example of how environments shape the animals that inhabit them. There is no doubt that in many cases animals can adapt well to their environment, even if it changes (and in the case of humans – also significantly affect it back).

However, animals, including insects, are unable to cope with any change. A number of studies from recent years have revealed severe damage to the insect population in the world due to human activity. In Germany, for example, a decrease of no less than 76 percent in the various insect populations in the country’s nature reserves during the years 2016-1989 was revealed. Similar numbers have also been found in other countries around the world.

One of the main reasons for the disappearance of insects is the loss of habitats due to increasing human development. Other causes are habitat fragmentation by infrastructure and human development and reduction, as well as damage from human disturbances, such as light pollution at night. Agricultural pesticides also harm insects, as well as invasive species that spread human activity and take over habitats and repel the native species. Another reason for the deterioration in insect populations is the climate crisis, which is having a widespread impact on all ecosystems.

Although insects are small, they are far more significant to the environment and man than we would think, since all terrestrial ecosystems depend on them. One of their main functions is pollination of flowers, a process on which a significant part of the agricultural crops that provide our food depends. Some insects also play a significant role in eradicating pests from agriculture as the natural enemies of those pests. Beyond that, they constitute an important tier in the food web, and damage to their frequency can affect the entire web. Various measures must be taken to ensure the conservation of endangered species, such as protecting their habitats, reducing the use of pesticides and integrating natural habitats into agricultural space, so that whether they fly or not, the beneficial insects will not go with the wind.