Expanding insect pollinators in the Anthropocene

Abstract

Global changes are severely affecting pollinator insect communities worldwide, resulting in repeated patterns of species extirpations and extinctions. Whilst negative population trends within this functional group have understandably received much attention in recent decades, another facet of global changes has been overshadowed: species undergoing expansion. Here, we review the factors and traits that have allowed a fraction of the pollinating entomofauna to take advantage of global environmental change. Sufficient mobility, high resistance to acute heat stress, and inherent adaptation to warmer climates appear to be key traits that allow pollinators to persist and even expand in the face of climate change. An overall flexibility in dietary and nesting requirements is common in expanding species, although niche specialization can also drive expansion under specific contexts. The numerous consequences of wild and domesticated pollinator expansions, including competition for resources, pathogen spread, and hybridization with native wildlife, are also discussed. Overall, we show that the traits and factors involved in the success stories of expanding pollinators are mostly species specific and context dependent, rendering generalizations of 'winning traits' complicated. This work illustrates the increasing need to consider expansion and its numerous consequences as significant facets of global changes and encourages efforts to monitor the impacts of expanding insect pollinators, particularly exotic species, on natural ecosystems.

Keywords: bees; bumblebees; butterflies; conservation; exotic species; expansion; global change; invasive species.

Fig 1

Visual representation of the factors involved in range expansion in pollinators in the Anthropocene: 1, climate change; 2, anthropogenic transport; 3, reforestation; 4, deforestation; 5, urbanization; 6, pollinator domestication; 7, eutrophication; 8, agricultural intensification; 9, plant invasion. A, carpenter bee moved through wood transport; B, invasive megachilid bee benefitting from bee hotels; C, butterfly co‐expanding with its ornamental host; D, bumblebee nesting in a roof; E, butterfly co‐expanding with nitrophilous host; F, squash bee co‐expanding with crop host; G, bumblebee benefitting from domestication. Blue outlines correspond to climate change and anthropogenic transport, orange outlines to novel anthropogenic habitats and green outlines to agricultural intensification and its consequences. Illustrator: Morgane Goyens.