SLAM Project - Long Term Ecological Study of the Impacts of Climate Change in the natural forests of Azores: V - New records of terrestrial arthropods after ten years of SLAM sampling

Abstract Background A long-term study monitoring arthropods (Arthropoda) is being conducted since 2012 in the forests of Azorean Islands. Named "SLAM - Long Term Ecological Study of the Impacts of Climate Change in the natural forest of Azores", this project aims to understand the impact of biodiversity erosion drivers in the distribution, abundance and diversity of Azorean arthropods. The current dataset represents arthropods that have been recorded using a total of 42 passive SLAM traps (Sea, Land and Air Malaise) deployed in native, mixed and exotic forest fragments in seven Azorean Islands (Flores, Faial, Pico, Graciosa, Terceira, São Miguel and Santa Maria). This manuscript is the fifth data-paper contribution, based on data from this long-term monitoring project. New information We targeted taxa for species identification belonging to Arachnida (excluding Acari), Chilopoda, Diplopoda, Hexapoda (excluding Collembola, Lepidoptera, Diptera and Hymenoptera (but including only Formicidae)). Specimens were sampled over seven Azorean Islands during the 2012-2021 period. Spiders (Araneae) data from Pico and Terceira Islands are not included since they have been already published elsewhere (Costa and Borges 2021, Lhoumeau et al. 2022). We collected a total of 176007 specimens, of which 168565 (95.7%) were identified to the species or subspecies level. For Araneae and some Hemiptera species, juveniles are also included in this paper, since the low diversity in the Azores allows a relatively precise species-level identification of this life-stage. We recorded a total of 316 named species and subspecies, belonging to 25 orders, 106 families and 260 genera. The ten most abundant species were mostly endemic or native non-endemic (one Opiliones, one Archaeognatha and seven Hemiptera) and only one exotic species, the Julida Ommatoiulusmoreleti (Lucas, 1860). These ten species represent 107330 individuals (60%) of all sampled specimens and can be considered as the dominant species in the Azorean native forests for the target studied taxa. The Hemiptera were the most abundant taxa, with 90127 (50.4%) specimens. The Coleoptera were the most diverse with 30 (28.6%) families. We registered 72 new records for many of the islands (two for Flores, eight for Faial, 24 for Graciosa, 23 for Pico, eight for Terceira, three for São Miguel and four for Santa Maria). These records represent 58 species. None of them is new to the Azores Archipelago. Most of the new records are introduced species, all still with low abundance on the studied islands. This publication contributes to increasing the baseline information for future long-term comparisons of the arthropods of the studied sites and the knowledge of the arthropod fauna of the native forests of the Azores, in terms of species abundance, distribution and diversity throughout seasons and years.


Introduction
A common finding all over the globe is that arthropods are the major taxa involved in ecosystems services (Weisser and Siemann 2013, Gullan and Cranston 2014, Jones et al. 2014, Jankielsohn 2018. Some of these services are now well studied, such as pollination (Pey et al. 2014, Cross et al. 2015 or biological control, food provisioning and recycling organic matter (Noriega et al. 2018). Nevertheless, to fully understand how these taxa shape human activities, the first step is to survey their diversity, abundance structure and variation through time (Dornelas et al. 2013). Although the arthropod fauna is one of the most diverse taxon on Earth (Gullan andCranston 2014, Aberlenc 2020), its diversity is still poorly documented (Sallé et al. 2021, Bukowski et al. 2022. Islands are critical places for the conservation of biodiversity, there being a critical need to gather knowledge to support conservation management in such extremely dynamic and changing ecosystems (Whittaker and Fernández-Palacios 2007, Fernández-Palacios et al. 2021, Wyckhuys et al. 2022. They harbour a unique diversity with often high levels of endemicity amongst many taxa (MacArthur and Wilson 2001, Fernández-Palacios et al. 2021, Florencio et al. 2021). However, as a consequence of their particular evolutionary process, island communities are also very sensitive to the introduction of exotic species (Sax andGaines 2008, Pyšek et al. 2020). These new arrivals are more and more frequent due to the increase in the transit of people and goods, which offers new opportunities for species to spread rapidly over large areas (Jenkins 1996, Nentwig 2008, Kueffer et al. 2010. Therefore, monitoring and documenting changes in arthropod communities are urgent, especially on islands, to guide and improve biodiversity management strategies (Loh et al. 2005, Blüthgen et al. 2022. Standardised tools and protocols offer the possibility to reproduce science and more defined results on species distributions and their dynamics (Carvalho et al. 2012, Malumbres-Olarte et al. 2019. Furthermore, importance must be given to the new records as they appear to be new pieces in the complex puzzle of life (Borges and Wunderlich 2008, Bolu and Varga 2021, Borges et al. 2022a, especially on islands where they are more likely to be introduced species that can threaten the sustainability of ecosystems (Tylianakis et al. 2008, Albrecht et al. 2014, Heleno et al. 2020. biodiversity erosion on Azorean native forests (Azores, Portugal) (see previous data papers in Costa and Borges (2021), Borges et al. (2022c), Borges et al. (2022d), Lhoumeau et al. (2022)).
This long-term project aims to (Costa and Borges 2021): 1.
collect long-term ecological data to evaluate species distributions and abundance at multiple spatial and temporal scales, responding to the Wallacean and Prestonian shortfalls (Cardoso et al. 2011a); 2.
identify biodiversity erosion drivers impacting oceanic indigenous assemblages under global change for conservation management purposes; 3.
investigate species-environment relationships and use species distribution and abundance data in model-based studies of environmental change in different islands; 4.
contribute to clarify the potential occurrence of an "insect decline" in the Azores (see ) and identify the spatial and temporal invasion patterns of exotic arthropod species (see Borges et al. (2022c)); 5.
contribute with temporal data to re-assess the IUCN Red-list status of Azorean endemic arthropods (Cardoso et al. 2011b);6. perform studies about the relationship between diversity (taxonomic, functional and phylogenetic) and ecosystem functions.

Additional information:
The year 2012 marks the beginning of the SLAM traps survey of arthropods on Terceira Island, within the Project NETBIOME ISLANDBIODIV. This first survey was then followed by several others within the Azores Archipelago with the purpose of sampling and describing all arthropods inside native forest fragments using passive SLAM traps (Sea, Land and Air Malaise trap, Fig. 1). During the last years, the data from these SLAM traps have been used to respond to several ecological and conservation questions (for example, see , ), de Vries et al. (2021).

Project description
Title: SLAM -Long Term Ecological Study of the Impacts of Climate Change in the natural forest of Azores.

Personnel:
The project was conceived and is being led by Paulo A.V. Borges

Study area description:
The Azores Archipelago comprises nine volcanic Islands and is located in the Atlantic Ocean between latitudes 37° and 40° N (Fig. 2), situated in the mid-Atlantic Ocean spreading over 500 km in a W/NW-E/SE direction. All Islands are oceanic of recent volcanic origin and the prevalent climate is temperate, with no dry seasons and mild summers. Santa Maria and Graciosa are the driest Islands and the prevalent climate in these Islands is temperate with dry and warm summers.
Based on the recent forest classification proposal of Elias et al. (2016), most of the studied sites are located in the Juniperus-Ilex forests and Juniperus woodlands (between 600 m and 1000 m a.s.l.) (see Table 1), with some few remants of the Laurus Submontane Forests in Terceira (Fig. 10) and Pico Islands. All these forests are hyper-humid, densely covered by ferns and mosses at all strata (Fig. 11).
Design description: We sampled on the Azorean Islands of Flores, Faial, Pico, Graciosa, Terceira, São Miguel and Santa Maria, four times per year between 2012 and 2021

Sampling methods
Description: Overall, we sampled a total of 42 plots (seven in Flores, three in Faial, two in Graciosa, ten in Pico, 16 in Terceira, three in São Miguel and one in Santa Maria), using passive SLAM traps (Table 1). The plots are located in some of the best preserved wet forest patches of the seven Islands, having only limited human disturbance (Borges et al. 2017).

Sampling description:
We used passive flight interception SLAM traps (Sea, Land and Air Malaise trap; 110 x 110 x 110 cm) (MegaView Science Co. Ltd., Taichung City, Taiwan) ( Fig. 1) to sample native forest plots in several Azorean Islands, with one trap placed at each plot.
The trapped arthropods crawl up the mesh and then fall inside the sampling recipient. Each recipient is filled with propylene glycol (pure 1,2-propanediol) to kill the captured arthropods and conserve the sample between collections, enabling also the preservation of DNA for future genetic analyses. Although this protocol was developed to sample flying arthropods, by working as an extension of the tree, non-flying species, such as spiders, can also crawl into the trap, widening the range of groups that can be sampled by this technique.
Quality control: In the laboratory, specimen sorting and arthropod identification followed standard procedures, using somatic and genitalic features for species identification. A reference collection was made for all collected specimens (whether or not identified at species level) by assigning them a morphospecies code number and depositing them at the Dalberto Teixeira Pombo Insect Collection (DTP), University of Azores (Terceira Island).

Traits coverage
Functional traits of Araneae including detailed morphometric measurements for most of the studied species can be accessed in the publication by Macías-Hernández et al. (2020).
Trophic preference for all other arthropods are assessed using the publication by .

Temporal coverage
Notes: Despite our efforts, not all islands could be continuously monitored. The temporal graph hereafter ( Fig. 12) shows the range of temporal coverage for all traps.

Usage licence
Usage licence: Creative Commons Public Domain Waiver (CC-Zero) Temporal coverage of each plot. Codes of sites as in Table 1.

Description:
The dataset was published in the Global Biodiversity Information Facility platform, GBIF (Borges and Lhoumeau 2022). The following data table includes all the records for which a taxonomic identification of the species was possible. The dataset submitted to GBIF is structured as a sample event dataset that has been published as a Darwin Core Archive (DwCA), which is a standardised format for sharing biodiversity data as a set of one or more data tables. The core data file contains 893 records (eventID). This GBIF IPT (Integrated Publishing Toolkit, Version 2.5.6) archives the data and, thus, serves as the data repository. The data and resource metadata are available for download in the Portuguese GBIF Portal IPT (Borges and Lhoumeau 2022).

Column label Column description
id Unique identification code for sampling event data.

Description:
The dataset was published in the Global Biodiversity Information Facility platform, GBIF (Borges and Lhoumeau 2022). The following data table includes all the records for which a taxonomic identification of the species was possible. The dataset submitted to GBIF is structured as an occurrence table that has been published as a Darwin Core Archive (DwCA), which is a standardised format for sharing biodiversity data as a set of one or more data tables. The core data file contains 14824 records (occurrenceID). This GBIF IPT (Integrated Publishing Toolkit, Version 2.5.6) archives the data and, thus, serves as the data repository. The data and resource metadata are available for download in the Portuguese GBIF Portal IPT (Borges and Lhoumeau 2022 ).

Column description
id Unique identification code for species abundance data. Equivalent here to eventID. type The nature or genre of the resource, as defined by the Dublin Core standard. In our case "PhysicalObject".
licence Reference to the licence under which the record is published. institutionID The identity of the institution publishing the data. collectionID The identity of the collection publishing the data. institutionCode The code of the institution publishing the data. collectionCode The code of the collection where the specimens are conserved.

Additional information
We collected a total of 176007 specimens from which 168565 (95.7%) were identified at species or subspecies level. These identified specimens belong to 25 orders, 106 families, 260 genera and 316 species or subspecies. In this pool of 316 named species and subspecies, a total of 132 species are considered introduced, 88 native non-endemic, 55 endemic and 41 have indeterminate colonisation status.
Based on a comparison with the previous Azorean arthropod checklist ), we recorded a total of 72 unique new records at Island level ( Koch, 1864 Westring, 1851 Arachnida Araneae Drassodes lapidosus (Walckenaer, 1802) Koch, 1838 Arachnida Araneae Lathys dentichelis (Simon,    , that is a saprophagous species commonly found in several habitats in Azores (native and exotic forests, entrance of caves).

Conservation remarks
We recorded 23 introduced species which are new to the Islands of the Azores Archpelago. This number of new records is higher than for the endemic (n = 4), native (n = 21) and indeterminate (n = 8) species. These new records increase the diversity of the species at island scale. They must be considered with particular attention as they might rapidly increase their distribution. However, we need to be careful with these new records because they could represent an effect of the past low sampling effort and not recent introductions. Indeed, not all Islands were sampled with the same intensity through time. In order to provide better time series analysis, we must continue sampling arthropods over all Islands with increasing regularity.
Introduced species are the greatest part of the new records, but also the most diverse group of species over all the Archipelago (Fig. 13). In all Islands we monitored with this programme, introduced species represent almost 25% of the species richness of a given Island. Graciosa (42%), Pico (41%) and Flores (38%) are the three Islands with the highest percentage of introduced species sampled (Fig. 13). It is a strong and critical signal for Graciosa as this is the Island where the temporal coverage of sampling is the lowest (Fig.  12), but with the highest proportion of introduced species. This result must be the consequence of the limited amount of native forest on this Island. Indeed, there is no fragment of native forest remaining on this Island, only a small secondary patch dominated by the endemic tree species Erica azorica, as an early succession shrub (see Species of Habitat management areas in Fig. 5). Furthermore, Graciosa Island is the second smallest island of the Archipelago (after Corvo Island) and the lowest in altitude. All these parameters can explain that the quality of the fragment where we sampled is poor in comparison to other Islands (like Terceira Island, where the greatest fragments of native forest occur) (Triantis et al. 2010). Indeed, other long term monitoring studies performed in non-native environments , Borges et al. 2022a, Borges et al. 2022b showed that it is more likely to find exotic arthropods species in such disturbed places. Therefore, in Graciosa, monitoring programmes should be encouraged to obtain time series of arthropod communities so that trends can be detected and forecast. In any case, particular attention must be given to exotic species as they are part of the global biodiversity crisis experienced in the Archipelago , Singh 2002.
A positive output of this study is the non-dominance of introduced species in native forest patches, a result that coincides with a recent study conducted on a native forest fragment Terra-Brava on Terceira (see Borges et al. (2017)). Fig. 14 shows that almost all of the seven Islands we monitored have less than 20% of their total species abundance composed of introduced species (except for Flores Island where 22% of the total abundance of arthropods sampled are introduced). However, we detected that the highest proportion of the abundance in Graciosa Island is attributed to native non-endemic species. Further analysis is needed to explore links between such dominance of native nonendemic species and the quality of the habitat. Variations of the proportion of exotic species amongst the Islands are likely to be the consequence of difference of habitat quality, age and size of the Island and human activities and interaction between these factors (Borges et al. 2006).  All of the seven Islands monitored showed that introduced arthropod species are the most diverse group, but not the dominant one, which suggest that introduced species are mostly vagrants with large turnover rates across space and time. Such turnover on oceanic islands is common to other taxa like plants (Gilbert andLechowicz 2005, Kueffer et al. 2010). A future analysis of beta diversity drivers through time can shed light on the dynamics of invasions on these Islands (Carvalho et al. 2012, Legendre andDe Cáceres 2013). Finally, our results show that the forest fragments where we performed our samplings are likely to be resistant to an increasing pressure of the constant introduction of exotic species (but see ). However, monitoring needs to be continued to detect the crossing of a potentially dramatic threshold (Xie et al. 2019) leading to profound and irreversible changes in the composition and functioning of native Azorean ecosystems.
PAVB: Conceptualisation; Methodology; Research (field and laboratory work); Resources; Data Curation; Darwin Core dataset preparation; Formal analysis and interpretation; manuscript writing.
ARP, RC and AL: Research (field and laboratory work); Resources; Data Curation.
All the remaining authors participated in data interpretation and manuscript revision.