Cities “wake up” sleeper species

Frank, S. D., & Just, M. G. (2020). Can Cities Activate Sleeper Species and Predict Future Forest Pests? A Case Study of Scale Insects. Insects, 11(3), 142. MDPI AG. Retrieved from http://dx.doi.org/10.3390/insects11030142.

Summary

Climate warming can increase the abundance of insect pests and the damage they cause in forests. In part this is due to innocuous native and non-native insects that become more damaging as temperatures increase. Often called ‘sleeper species’, these pests take on traits common to invasive species such as high reproduction, range expansion, and escape from natural enemies. Urban areas are hotter than surrounding rural areas (the “urban heat island effect”) and in some cases can be used to predict the effects of warming and other environmental changes on ecosystems. In this paper, the authors summarize examples and common traits of native sleeper species, then provide two case studies of scale insects, small sap-sucking insects that have become major pests of urban trees due to the urban heat island effect. The two focal scale species (Oak lecanium and Gloomy scale) benefit from warmer urban temperatures by escaping from predation, increasing growth and reproduction, and range expansion. Similar responses have been documented in warming natural forests. This demonstrates that cities can help identify sleeper species and predict their impacts ahead of climate-driven range expansion.

Take home points

  • Native species can expand their ranges (nuisance neonatives) or acquire new, more damaging, traits with warming.

  • These damaging native pest species identified in urban areas are potential ‘sleeper species’ that could invade natural ecosystems as they warm.

  • Research in cities can help identify which native species will become a nuisance with climate change.

Management implications

  • Managers need to prepare not just for the next exotic insect but also for native sleeper species.

  • Urban heat islands allow sleeper species to develop large populations north of their natural range. As the rural climate catches up, these species could move into forests.

  • Managers can test and refine tactics on urban trees to prepare for management in forests.

Keywords

Range Expansion; Impact Study; Latent Invasive Species; Urban; Warming