A group of entomologists decided to explain where the ancestors of modern red cockroaches came from and how they took over human settlements on almost all continents. To do this, scientists sequenced the DNA of nearly 300 insects and modeled the most likely distribution scenarios based on genetic information.
No matter where a person lives, there will be insects such as cockroaches in his home. So where did they come from? Where did humanity get these pests? The history of the appearance of the most common cockroaches – this is how the red ones became among more than 4,000 species (Blattella germanica) or cockroaches, as they are also called, are shrouded in mystery. These insects are easy to find in homes but are almost never found in nature. In temperate and cold latitudes, cockroaches are forced to live with humans because they will freeze outside. That’s why they became synanthropic.
The red cockroach was first described by Carl Linnaeus in 1767, and the widespread distribution of this insect in Europe was reported in the early 19th century. True, its close relatives come from Africa and Asia, and the Asian cockroach was once proposed as an ancestor (Blattella asahinai) lives in India, Myanmar, and after introduction in the USA. Although the DNA of red cockroaches has been studied in sufficient detail, it was not possible to reconstruct the possible route of spread earlier due to insufficient information about these insects.
An international group of entomologists from China, Singapore, India, Europe and other countries decided to fill the gap. Scientists identified the cockroach’s genetic structure using genomic markers from 281 samples collected from 17 countries on all continents (except Antarctica). The researchers then reconstructed the insect’s spread route using demographic modeling and evaluated the most likely scenarios. The results of the scientific study are published in the journal. Proceedings of the National Academy of Sciences .
Genetic information for previously collected insects was obtained from two crushed legs of each specimen, but most were captured alive. The DNA of cockroaches (all treated as a single population) was compared to the reference. Blattella germanica . Three generations of models changed in one year, and scientists determined the rate of mutations using the example of Drosophila. Entomologists found a small 0.59% difference between red and Asian cockroaches based on mitochondrial genes. In other family groups, the differences were much more significant; More than 5%.
The Asian species was indeed the ancestor of the red cockroach, and scientists believe it coexisted with humans as early as 2,100 years ago, when human civilization was flourishing in the Asian region. The red cockroach started in two directions from the territory of modern India or Myanmar. He went west about 1,200 years ago; This may be related to the development of trade and the development of the army of the Islamic caliphs. The path to the east began about 390 years ago; this may have been facilitated by European colonial trade with Southeast Asia (possibly the Dutch and British East India Companies).
The modeled time of arrival in Europe – about 270 years ago – coincided with early historical records of the 18th century. Later, due to the development of transport, global trade and increased housing comfort (heating and water supply), red cockroaches settled in previously unsuitable and inaccessible regions – for example, Russia or Australia. In other words, man himself created all the conditions for the spread of this insect throughout the world.
Source: Port Altele
