Abstract
How we measure diversity can have important implications for understanding the impacts of anthropogenic pressure on ecosystem processes and functioning. Functional diversity quantifies the range and relative abundance of functional traits within a given community and, as such, may provide a more mechanistic understanding of ecosystems. Here, we use a novel approach to examine how lepidopteran richness and diversity, weighted by species abundance, differ between habitats under different disturbance regimes (highly disturbed non‐native plantations and less disturbed broadleaf woodlands), both with and without constraining by similarity due to shared taxonomy or functional traits. Comparisons of diversity between the two habitats differed according to which metric was being used; while species richness was 58% greater in broadleaf woodlands, after accounting for species similarity due to shared functional traits, there was little difference between woodland types under two different disturbance regimes. Functional diversity varied within the landscape but was similar in paired broadleaf and plantation sites, suggesting that landscape rather than local factors drive biotic homogenization in plantation dominated landscapes. The higher richness in broadleaf sites appears to be driven by rare species, which share functional traits with more common species. Moth populations in disturbed, plantation sites represent a reduced subset of moth species compared to broadleaf sites, and may be more vulnerable to disturbance pressures such as clear‐felling operations due to low community resilience.
Highlights
Widespread concerns about the impact of human activities on eco‐ systems have made the accurate measurement and assessment of biodiversity increasingly important
This study demonstrates that non‐native coniferous plantations harbor similar moth functional diversity to native broadleaf wood‐ lands, but the level of functional redundancy in plantations is lower, for certain functional traits
Naïve rich‐ ness and diversity was significantly lower in habitats characterized by an intense disturbance regime, when we constrain by functional similarity there appears to be little difference in richness and di‐ versity
Summary
Widespread concerns about the impact of human activities on eco‐ systems have made the accurate measurement and assessment of biodiversity increasingly important. Species richness has long been the most commonly employed measure of biological diversity, stemming from the premise that species delineations are distinct, but this can be contentious (Hooper et al, 2002). In most indices of species diversity all species are treated as different from each other, whereas this is clearly not the case (Chao, Chiu, & Jost, 2014; Leinster & Cobbold, 2012). A community comprising distantly related species has more evolutionary diversity. |2 than a community with only closely related species. An as‐ semblage in which species share similar functional traits is less di‐ verse than an assemblage with a range of functional traits, and may correspondingly result in reduced ecosystem functioning
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