Functional and Taxonomic Beta Diversity of Saproxylic Beetles in Mediterranean Forests: On What Factors Do They Depend?

Abstract

Understanding how biodiversity is distributed across geographical and environmental gradients is a main goal of diversity sciences. However, since ecosystem processes are linked to variation in functional traits of the biota, examining functional beta diversity is particularly important. Our objective was to analyze the taxonomic and functional beta diversity patterns of saproxylic beetle assemblages in evergreen Quercus forest of Spain. We tested whether environmental or geographical distance had a greater influence on taxonomic and functional beta diversity, and if both measures of beta diversity were affected by the same environmental variables. We used 45 flight interception traps distributed in three protected areas over a 12-mo period to sample saproxylic beetles. We measured 13 environmental variables around each trap and the geographical distance between traps. For functional composition, we used 12 functional traits from four functional groups (morphological, phenological, trophic, and a surrogate of physiological). Our results showed that environmental differences between areas influenced the taxonomic and functional beta diversity components (replacement and loss/gain) but in different ways. While replacement components (higher for taxonomic composition) increased with environmental distance, the loss or gain components (higher for functional composition) remained constant, indicating that species replacement mostly involved functionally redundant species. Besides, environmental variables influencing both taxonomic and functional composition were strongly dependent on each area. In conclusion, in well-preserved Mediterranean forests, environmental filtering determines the taxonomic and functional composition of saproxylic beetle assemblages, by favoring species replacement but filtering species traits.

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

“…The availability of multiple complementary species traits is essential to calculate valid measures of the functional diversity of species assemblages (Petchey & Gaston, 2006). In the field of deadwood ecology, such measures can be applied to explain the responses of saproxylic beetles to climate and local habitat properties (Pérez‐Sánchez et al., 2020; Thorn et al., 2018). Functional diversity measures of saproxylic species have also been integrated in biogeographical studies (Hagge et al., 2019) as well as in studies on interaction networks (Wende et al., 2017).…”

Physical and biotic factors driving the diversity of spider assemblages in tree hollows of MediterraneanQuercusforests

“…The deciduous character of Q . pyrenaica can contribute to a major change for the portion of the assemblage that hunts in the canopy (Szinetár & Horváth, 2005; Pérez‐Sánchez et al ., 2020). Furthermore, in predator assemblages such as spiders, this high temporal segregation may be helping to reduce competition (Valderrama, 2000; Richards & Windsor, 2007) in this confined microhabitat as demonstrated for dragonflies in tropical tree hollows (Fincke, 1999).…”

“…A dominance of temporal turnover over nestedness was also observed in saproxylic Coleoptera (Ramilo et al, 2017), although turnover was much higher in spider than in beetle assemblages (0.81 for spiders vs. 0.68 for beetles). The deciduous character of Q. pyrenaica can contribute to a major change for the portion of the assemblage that hunts in the canopy (Szinetár & Horváth, 2005;Pérez-Sánchez et al, 2020). Furthermore, in predator assemblages such as spiders, this high temporal segregation may be helping to reduce competition (Valderrama, 2000;Richards & Windsor, 2007) in this confined microhabitat as demonstrated for dragonflies in tropical tree hollows (Fincke, 1999).…”

Dispersal limitation and environmental filtering effects: The taxonomic and functional beta diversity of ground beetles along the altitudinal gradient in Chinese warm‐temperature forests

“…Therefore, the taxonomic and functional beta diversity of carabids might be influenced by environmental filtering and dispersal limitation. These effects on taxonomic and functional beta diversity are complex (Leão‐Pires et al., 2018 ; Pérez‐Sánchez et al., 2020 ). Specifically, environmental filtering may favor species turnover but filters for functional traits (Geldenhuys et al., 2022 ), species with different dispersal abilities are affected to varying degrees by spatial and environmental factors; therefore, the response of functional traits related to dispersal to spatial factors may be stronger than to environmental factors (Dalmolin et al., 2019 ; Heino, 2013 ).…”