A comparative analysis of terrestrial arthropod assemblages from a relict forest unveils historical extinctions and colonization differences between two oceanic islands

Abstract

During the last few centuries oceanic island biodiversity has been drastically modified by human-mediated activities. These changes have led to the increased homogenization of island biota and to a high number of extinctions lending support to the recognition of oceanic islands as major threatspots worldwide. Here, we investigate the impact of habitat changes on the spider and ground beetle assemblages of the native forests of Madeira (Madeira archipelago) and Terceira (Azores archipelago) and evaluate its effects on the relative contribution of rare endemics and introduced species to island biodiversity patterns. We found that the native laurel forest of Madeira supported higher species richness of spiders and ground beetles compared with Terceira, including a much larger proportion of indigenous species, particularly endemics. In Terceira, introduced species are well-represented in both terrestrial arthropod taxa and seem to thrive in native forests as shown by the analysis of species abundance distributions (SAD) and occupancy frequency distributions (OFD). Low abundance range-restricted species in Terceira are mostly introduced species dispersing from neighbouring man-made habitats while in Madeira a large number of true rare endemic species can still be found in the native laurel forest. Further, our comparative analysis shows striking differences in species richness and composition that are due to the geographical and geological particularities of the two islands, but also seem to reflect the differences in the severity of human-mediated impacts between them. The high proportion of introduced species, the virtual absence of rare native species and the finding that the SADs and OFDs of introduced species match the pattern of native species in Terceira suggest the role of man as an important driver of species diversity in oceanic islands and add evidence for an extensive and severe human-induced species loss in the native forests of Terceira.

Taxonomic and functional diversity of insect herbivore assemblages associated with the canopy-dominant trees of the Azorean native forest

“…These characteristics are particularly evident in the Azores, a relatively young and remote oceanic archipelago located in the North Atlantic [34,35]. The quite recent age of the Azorean islands and their remoteness, coupled with their history of volcanism along with modern human-driven disturbance, have been pointed out as major determinants for the low species richness and endemism in this archipelago [36–38]. Presently, the native biodiversity can mainly be found in the remaining forest patches on the different Azorean islands, where some microhabitats (like the canopies of endemic trees) accommodate a considerable fraction of native non-endemic and endemic species [39–41].…”

Housing Buildings’ Characterization at Corvo Village (Azores) Historical Center: Towards a Sustainable Rehabilitation Process

“…Generally, acacia, oak, chestnut, and cedar were the ones composing the native forest. In 1850 only 5.44 km 2 of the island was native forest [33], and it was extinguished during the mid-20th century [34]. Pine tree wood was not present in the original forest, and its current presence in construction materials and elements indicates that this material came from shipwrecks that occurred near the island.…”

SLAM Project - Long Term Ecological Study of the Impacts of Climate Change in the natural forest of Azores: I - the spiders from native forests of Terceira and Pico Islands (2012-2019)

“…In 2012, a long-term project to monitor the distribution and abundance of arthropods in native forests was set up in the Azores named as SLAM -"Long Term Ecological Study of the Impacts of Climate Change in the natural forest of Azores" (Borges et al 2017b, Matthews et al 2018, Borges et al 2020. In this contribution, we describe this project and the first taxon for which data are readily available for the majority of the samples, i.e.…”

“…In the past decades, many studies have aimed to understand diversity, abundance and phylogeographic patterns of this group, in both native and anthropogenic habitats, as well as their ecology and habitat affinities (Borges and Brown 2001, Borges and Brown 2004, Borges and Wunderlich 2008, Florencio et al 2013, Florencio et al 2015, Parmakelis et al 2015. Others have also focused on this group for inter-archipelago comparisons, trying to understand the reason behind the present patterns (Cardoso et al 2010, Boieiro et al 2018. Further works have also tried to detect which areas are of particular conservation interest in the Azores , Gaspar et al 2011.…”

“…Further works have also tried to detect which areas are of particular conservation interest in the Azores , Gaspar et al 2011. The main threats to the Azorean spider fauna include the colonisation and spread of exotic species and habitat degradation Wunderlich 2008, Cardoso et al 2010), which may have already caused the extinction of many endemic spider species in the past (Borges and Wunderlich 2008, Cardoso et al 2010, Boieiro et al 2018, Crespo et al 2021. The impact of climatic changes should also be considered as one of the main drivers of biodiversity erosion for this taxon in the Azores (Ferreira et al 2016).…”