Insects decline with host plants but coextinctions may be limited

Area of Science:

• Ecology and conservation biology
• Entomology
• Botany

Background:

• Wild plant population loss is often linked to insect coextinctions, especially for specialized species.
• Global declines in terrestrial insects and plants highlight the need to understand their interaction dynamics.
• The precise relationship between plant population trends and insect coextinction risk remains largely unexplored.

Purpose of the Study:

• To analyze the relationship between population trends of insects and their host plants in Germany.
• To assess the impact of simulated host plant extinctions on insect coextinction risk.
• To evaluate the resilience of insect-plant interaction networks.

Main Methods:

• Analysis of population trends for insects and host plants in Germany.
• Inclusion of over 150,000 interactions among 3,429 plant and 2,239 insect species (pollinators and herbivores).
• Simulation of threatened host plant extinctions to estimate insect coextinction rates.

Main Results:

• Parallel population declines observed between insects and host plants, with generalist hoverflies as an exception.
• Simulated extinctions of threatened host plants resulted in limited insect coextinctions.
• A high percentage of insect species (96%) retained over 25% of their host plant diversity, with 98% retaining at least one common host species.

Conclusions:

• Insect coextinctions are not a direct 1:1 match with plant extinctions, challenging common assumptions.
• Declining plant abundance contributes to insect decline, but threatened plant extinctions do not necessarily trigger widespread insect extinction waves.
• Insect-plant interaction networks demonstrate significant resilience, even with specialized insect species potentially relying on non-threatened plants.