Arthropod traits and assemblages differ between core patches, transient stepping-stones and landscape corridors

Scott M Pedley,Paul M Dolman

doi:10.1007/s10980-020-00991-0

Scott M Pedley, Paul M Dolman

Open Access

https://doi.org/10.1007/s10980-020-00991-0

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Abstract

ContextRestoring landscape connectivity can mitigate fragmentation and improve population resilience, but functional equivalence of contrasting elements is poorly understood. Evaluating biodiversity outcomes requires examining assemblage-responses across contrasting taxa.ObjectivesWe compared arthropod species and trait composition between contrasting open-habitat network elements: core patches, corridors (allowing individual dispersal and population percolation), and transient stepping-stones (potentially enhancing meta-population dynamics).MethodsCarabids and spiders were sampled from core patches of grass-heath habitat (n = 24 locations across eight sites), corridors (trackways, n = 15) and recently-replanted clear-fells (transient patches, n = 19) set in a forest matrix impermeable to open-habitat arthropods. Species and trait (habitat association, diet, body size, dispersal ability) composition were compared by ordination and fourth corner analyses.ResultsEach network element supported distinct arthropod assemblages with differing functional trait composition. Core patches were dominated by specialist dry-open habitat species while generalist and woodland species contributed to assemblages in connectivity elements. Nevertheless, transient patches (and to a lesser degree, corridors) supported dry-open species characteristic of the focal grass-heath sites. Trait associations differed markedly among the three elements. Dispersal mechanisms and their correlates differed between taxa, but dry-open species in transient patches were characterised by traits favouring dispersal (large running hunter spiders and large, winged, herbivorous carabids), in contrast to wingless carabids in corridors.ConclusionsCore patches, dispersal corridors and transient stepping-stones are not functionally interchangeable within this system. Semi-natural core patches supported a filtered subset of the regional fauna. Evidence for enhanced connectivity through percolation (corridors) or meta-population dynamics (stepping stones) differed between the two taxa.

Highlights

Restoring functional connectivity is promoted in conservation strategies to facilitate biodiversity resilience and population survival in the face of anthropogenic landscape fragmentation, land-use intensification and climate change (Chetkiewicz et al 2006; DEFRA 2018; Isaac et al 2018)
Core patches were dominated by specialist dry-open habitat species while generalist and woodland species contributed to assemblages in connectivity elements
Trait associations differed markedly among the three elements. Dispersal mechanisms and their correlates differed between taxa, but dry-open species in transient patches were characterised by traits favouring dispersal, in contrast to wingless carabids in corridors

Summary

Introduction

Restoring functional connectivity is promoted in conservation strategies to facilitate biodiversity resilience and population survival in the face of anthropogenic landscape fragmentation, land-use intensification and climate change (Chetkiewicz et al 2006; DEFRA 2018; Isaac et al 2018). While the optimal level of site aggregation or dispersion may differ between the aims of enhancing local persistence or favouring large-scale range-expansion (Hodgson et al 2011), functional connectivity at both scales requires appropriate interventions within local landscapes (Jongman et al 2004, 2011) Within such local networks, some generalist species may disperse through surrounding matrix habitats, for specialist species population connectivity often requires connectivity elements of suitable quality and type, with corridors, stepping stones, or a less hostile matrix (Bennett 2003) intended to improve dispersal and functional connectivity between ‘core patches’ or ‘ecological refuges’—relict fragments of natural or semi-natural habitat that have retained local species-populations over decadal timescales (Davis et al 2013). Examining responses in terms of assemblages’ trait- rather than species-composition supports generalisation to other ecological systems (McGill et al 2006; Pedley and Dolman 2014; Santini et al 2016)

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