Differential temporal beta‐diversity patterns of native and non‐native arthropod species in a fragmented native forest landscape

Abstract

An important factor that hinders the management of non‐native species is a general lack of information regarding the biogeography of non‐natives, and, in particular, their rates of turnover. Here, we address this research gap by analysing differences in temporal beta‐diversity (using both pairwise and multiple‐time dissimilarity metrics) between native and non‐native species, using a novel time‐series dataset of arthropods sampled in native forest fragments in the Azores. We use a null model approach to determine whether temporal beta‐diversity was due to deterministic processes or stochastic colonisation and extinction events, and linear modelling selection to assess the factors driving variation in temporal beta‐diversity between plots. In accordance with our predictions, we found that the temporal beta‐diversity was much greater for non‐native species than for native species, and the null model analyses indicated that the turnover of non‐native species was due to stochastic events. No predictor variables were found to explain the turnover of native or non‐native species. We attribute the greater turnover of non‐native species to source‐sink processes and the close proximity of anthropogenic habitats to the fragmented native forest plots sampled in our study. Thus, our findings point to ways in which the study of turnover can be adapted for future applications in habitat island systems. The implications of this for biodiversity conservation and management are significant. The high rate of stochastic turnover of non‐native species indicates that attempts to simply reduce the populations of non‐native species in situ within native habitats may not be successful. A more efficient management strategy would be to interrupt source‐sink dynamics by improving the harsh boundaries between native and adjacent anthropogenic habitats.

Increase of insular exotic arthropod diversity is a fundamental dimension of the current biodiversity crisis

“…Contrasting with recent studies on the European and North American mainland, our study shows no evidence of a decline of overall species diversity for endemic and native non‐endemic species, although the data are limited to 6 years of sampling. Yet, our study clearly identified three important patterns: (i) an increasing diversity of exotic species over time; (ii) the high temporal dynamism of exotic species (see also Matthews et al ., 2019b) and (iii) some evidence of a tendency for decreasing abundance for some endemic species.…”

“…In previous studies we observed that exotic species are already permeating Azorean indigenous arthropod communities (Gaston et al ., 2006; Rigal et al ., 2013), being however only abundant in anthropogenic habitats (Cardoso et al ., 2009). Rapid demographic fluctuations (Matthews et al ., 2019b) and contingent spatial factors related with native forest fragmentation and land‐use changes (Cardoso et al ., 2009; Florencio et al ., 2016) are surely involved on the increased diversity through time of exotic species in the Azores. It is worth noting that the increasing diversity of exotic species in 6 years is mostly due to juveniles.…”

“…In this contribution, we use a unique time‐series dataset of arthropods sampled in Azorean native forest over 6 years (2013–2018) (see Borges et al ., 2017 b; Matthews et al ., 2019b) to investigate recent trends in arthropod diversity and composition. The Azores is one of the world's most isolated archipelagos made of nine main islands aligned on a WNW–ESE axis in the Atlantic Ocean.…”

Arthropod diversity in two Historic Gardens in the Azores, Portugal

“…4 ). Even though these traps were initially designed to target flying arthropods, it has been proved that other non-flying species can get trapped as they climb up the mesh or the trees from where the SLAM traps hang ( Borges et al 2017b , Matthews et al 2019 ). The sampling recipients of the SLAM traps were set in April 2017 for both public gardens and checked monthly during six consecutive months until September 2017 (six samples for each garden).…”

Drought alters the functional stability of stream invertebrate communities through time

“…Experiments are regarded increasingly as a key biogeographical research tool (Alexander, Diez, Hart, & Levine, ; Pearse et al, ). While the theoretical concepts outlined above have application at biogeographical scales, an experimental approach is first necessary to rigorously test the effects of drought on temporal beta diversity (a measure of the difference in community composition between times at the same location; Matthews, Sadler, Carvalho, Nunes, & Borges, ) without the confounding effect of environmental gradients that undermine field studies and most meta‐analyses. Here, we examine partitioned temporal beta diversity calculated using presence–absence data and abundance data from a 2‐year stream mesocosm experiment, in which habitat was subjected to either continuous flow or repeated episodes of stream drying, to test how drought as a disturbance influences temporal changes in the structure and function of aquatic invertebrate communities.…”