Degree of urbanization influences the persistence of Dorytomus weevils (Coleoptera: Curculionoidae) in Beijing, China

As degree of urbanization continues to increase, a better understanding of the relationship between degree of urbanization and level of biodiversity is important for developing strategies to mitigate detrimental impacts of urbanization and to build sustainable cities. Dorytomus Gemar weevils are host specific on Salix L. and Populus L. trees which are commonly used for urban afforesting and greening and abundant in Beijing metropolitan area which can be divided into five concentric zones. We aim to reveal their distribution pattern and identify important determinants of their persistence in those zones. Our results showed that Dorytomus species number and abundance decreased gradually from outskirt to urban center. This pattern could be predicted by built-up ratio within 1–3 km, distance to urban centre and to a possible nearest population source in outskirt, but not by hostplant species number and abundance, habitat size and shape measured at habitat scale. The results indicate that (i) there is a negative relationship between degree of urbanization and Dorytomus species persistence in urban areas; (ii) efforts for Dorytomus weevil conservation should not only focus on remnant revegetation, but also be directed to regulate the ratio of built-up area and minimize isolation from nearby occupied patches; and (iii) built-up ratio in inner city should be lower as urban sprawls. To better understand the relationship between urbanization degree and species persistence and to offer realistic suggestions for urban landscape planners, further research involving multiple taxa and the synthesis of the ecological responses of different taxonomical groups are needed.