![lineage w bug lineage w bug](https://c8.alamy.com/comp/W85D8A/assassin-bug-rhinocoris-iracundus-corfu-greece-may-W85D8A.jpg)
Cropland areas can provide exploitable resources, e.g. In some instances, habitat loss can limit the geographic range of endemic species, although certain species may thrive in their new surroundings. Fragments of native vegetation become embedded in a matrix of cropland and pasture that will eventually affect the species and ecosystem dynamics 16. The expansion of agricultural frontiers necessitates conversion of the native habitat to agriculture 15. Recent human impacts on these biomes, particularly the expansion of agricultural areas, have drastically changed the landscape and likely the connection between ecosystems, rearranging patterns that began to be formed millions of years ago. This belt of mostly sparse dry vegetation is known as the ‘major South American disjunction’ 3, 10, 11 and forms a natural barrier preventing the movement of organisms between the northern Brazilian biomes and the Atlantic Forest 12, 13, 14. Today, the Amazon and Atlantic forests are separated by a unique mosaic composed of savannas and woodlands that covers a large area between the two forest biomes, from Argentina and Paraguay (the Argentinean and Paraguayan Chaco) and continues through the central Brazilian Cerrado to the Caatinga in northeastern Brazil. Recent findings suggest that forest expansion and contraction and ‘historically stable areas’ may also have played a major role in the differentiation of lineages 9.
![lineage w bug lineage w bug](https://i.pinimg.com/originals/ee/0b/35/ee0b3580125a71d194120fede5241f0d.jpg)
Due to this complexity and landscape composition, the processes of diversification by vicariance and habitat refugia are frequently invoked to explain the high levels of species endemism and diversity in this part of the planet 5, 6, 7, 8. The four major Brazilian biomes, the Atlantic Forest (AF), Cerrado (central savannas), Amazon and Caatinga (seasonally dry tropical forest) have undergone profound changes during glaciation and interglacial cycles 4. The drastic climate changes during the Plio-Pleistocene have been considered the main cause of high levels of diversification in many areas in Brazil 1, 2, 3. Individuals adapted to different environmental conditions and to large monocultures might currently be combining into a panmictic and hard-to-control pest population. Secondary contact between the main lineages is now occurring, mainly in areas of intensive farming and particularly in the Cerrado, an important agricultural frontier. Euschistus heros populations are expanding in size and range but at different rates, strongly affected by environmental variables. The northern lineage is older, more diverse, and prevalent in the Amazon and Caatinga, while the southern lineage is younger, less diverse, and prevalent in the Atlantic Forest and Chaco biomes. heros populations, which differentiated further in several biomes. Historical changes during the Plio-Pleistocene led to significant genetic differences between E. Two deep lineages that diverged in the Pliocene (4.5 Myr) occur over wide areas of Brazil. We examined mitochondrial (COI and Cyt b) and nuclear (ITS1) gene regions of 21 populations of the stink bug Euschistus heros, to investigate the genetic diversity, genetic structure, and demographic history of this emerging soybean pest in South America. The rapid pace of conversion of natural areas to agricultural systems is highly concerning, and the consequences for conservation and pest management are not yet fully understood.