What does a threatened saproxylic beetle look like? Modelling extinction risk using a new morphological trait...

Area of Science:

• Ecology
• Conservation Biology
• Entomology

Background:

• Species extinction is non-random, necessitating understanding of extinction risk factors for effective conservation.
• Functional trait-based approaches are crucial for assessing extinction risk, particularly for forest-dwelling, deadwood-dependent (saproxylic) beetles.
• Limited availability of suitable morphological traits has historically hindered extinction risk analyses in saproxylic beetles.

Purpose of the Study:

• To investigate the relationships between morphological features and extinction risk in European saproxylic beetles.
• To identify specific morphological traits that predict higher extinction risk in this group.
• To establish a standardized protocol and database for morphological trait measurements in saproxylic beetles.

Main Methods:

• Developed a protocol for measuring 37 morphological traits and created a database for 1,157 European saproxylic beetle species.
• Selected 13 independent traits related to color, body shape, locomotion, sensory perception, and foraging.
• Utilized a proportional-odds multiple linear mixed-effects model to assess the correlation between these traits and German Red List categories for 744 species.

Main Results:

• Six of the 13 morphological traits significantly correlated with extinction risk.
• Larger body size, a broader and rounder body shape, and shorter wings were associated with higher extinction risk.
• Increased extinction risk was also linked to decreased wing load and a higher mandibular aspect ratio (indicating shorter, more robust mandibles).

Conclusions:

• Morphological traits, beyond body size, significantly influence the extinction risk of saproxylic beetles.
• A selection of 13 traits can comprehensively represent the morphological characteristics relevant to extinction risk.
• These findings provide a foundation for functional trait-based conservation analyses for deadwood-associated insects.