Researchers studying the effects of urbanization on insects have found that some insects are better adapted to living in urban environments than others. In the midst of the hustle and bustle of city life, there are many different creatures, from insects to spiders to ants, that are often overlooked but have a significant impact on urban ecosystems. A recent study by Austrian scientists published in Frontiers in Ecology and Evolution found a link between the degree of urbanization and the prevalence of arthropods, which are invertebrate animals with exoskeletons such as bees, insects and spiders.
A researcher at the University of Innsbruck, Austria, first author Dr. “We show that as the transition from rural to urban areas occurs, the richness and diversity of arthropods in trees and shrubs decreases,” said Marion Chatlain. “We show that urbanization is unfavorable for wingless groups, especially on trees. In fact, spider mites and pinworms are less common in the city, whereas aphids, woodlice and flies are more common in the city.”
“In this study, we compared how different indicators of urbanization shape arthropod communities,” explained Chatelain. To do this, they collected arthropod samples at 180 sites in an area of ​​56.5 square meters. km in and around Innsbruck, Austria.
At each site, samples were taken in three microenvironments: tree crowns, bark, and shrub layer. By measuring the percentage of paved and built area, vegetation or trees, Chatelain and colleagues estimated the level of urbanization within 100, 500, and 1,000 meters around each area. They then tested the effect of this on the total number of arthropods (abundance), how many different taxonomic groups were present (wealth), and which arthropods were present. The team also looked at diversity, a measure that measures both well-being and wealth. Measuring the level of urbanization at different scales allowed us to better explain the impact of urbanization on arthropod populations.
Their results showed a relationship between the level of urbanization and the total number of arthropods in the shrub layer. The more urbanized the area, the more bark beetles and crab spiders lived in the bushes; this is a pattern that may have to do with the more nutritious leaves in the undergrowth of cities. As a genus, some species, such as flies, increased in urbanized areas, while certain groups of spiders were less common. This could indicate a preference for winged arthropods in cities, possibly due to their increased ability to move between isolated green spaces.
Chatelain and his team also observed certain effects on insects. For example, they found that the density of web-making spiders was consistently lower than that of actively hunting spiders, such as crab spiders. This suggests that the decrease or increase of spider groups is related to hunting methods. The fewer occurrences of four of the ten spider families studied, pointing to a direct impact on plant-eating insects found mostly in urban environments.
According to scientists, some groups of arthropods do well in cities while others do not. However, this does not directly understand the total number of insects: “As some groups thrive and others are filtered out from urban areas, there are at least as many arthropods in the city as in the countryside,” Chatelain said. “There are actually more arthropods in the city, especially bark beetles and crab spiders.”
The researchers also noted possible effects on insect-eating birds. “Our results suggest that urbanization affects the availability of arthropod prey, which is expected to affect predator nutritional status, feeding behavior, reproductive success, survival and distribution in the urban landscape,” Chatelain said. “This study is part of a larger project to examine the effects of urbanization on food availability, diet and nutritional status of great tit and bluefin fish.”
Source: Port Altele
