The inventory of selected groups of terrestrial arthropods in three coastal wetlands from Terceira Island (Azores)

The inventory was conducted during two years (2016-2017) under the responsibility of Paulo A. V. Borges with constant participation of César Pimentel. For the night sampling, additional help in the field was provided by Rosalina Gabriel and Mariana Brito. A large group of taxonomists contributed for the species identification: Luís Crespo (Araneae); Artur Serrano (Insecta, Coleoptera); Volker Assing and Michael Schülke (Coleoptera, Staphylinidae); António O. Soares (Coleoptera, Coccinellidae); Simone Fattorini (Coleoptera, Tenebrionidae); Peter Stüben (Coleoptera, Curculionidae). Finally, in the lab, we had the support of Alejandra Ros-Prieto in vouchers management for the University of Azores Insect Collection "Dalberto Teixeira Pombo" and Enésima Mendonça for the database management.

Terceira Island (area: 400.6 km²; elevation: 1,021.14 m) is one of the nine islands from the Azores archipelago, located in the North Atlantic, roughly at 38°43′49″N 27°19′10″W. The climate in the Azores is temperate oceanic, with regular and abundant rainfall, with high levels of relative humidity and persistent winds, mainly during the winter and autumn seasons.

Terceira Island is known for the presence of some very important pristine areas at high elevation (Gaspar et al. 2011). However, few natural areas still remain at lower elevations, notably in Praia da Vitória county. Three wetland areas, Paul da Praia da Vitória (PPV), Paul do Belo Jardim (PBJ) and Paul da Pedreira do Cabo da Praia (PPCP) (Figs 1, 2) were studied in this project. Coastal vegetation dominates, namely Juncus acutus and still includes some arboreal cover by the native shrub Morella faya. The Erica-Morella coastal woodlands as described in Elias et al. (2016) are not present and the exotic invasive species Arundo donax is very common.

Figure 1.  

General aspect of Paul da Praia da Vitória with its islands and the surrounding urban area (Photo by Paulo A.V. Borges).

Figure 2.  

Detail of the recently created islands of Juncus acutus habitat in Paul da Praia da Vitória (Photo by Paulo A.V. Borges).

The PPV (Fig. 1) was a large coastal salty marshland with associated dunes, which was largely transformed and reduced for urban development and underwent several dynamic changes in the last 500 years of human occupation. After some major work performed between 2006 and 2010, PPV is currently characterised by a large waterbody with islands of Juncus acutus isolated by channels (Fig. 2). PBJ was originally one of the largest dune areas from the Azores (Fig. 3), but after the construction of the Praia da Vitória harbour, it was reduced to a very small wetland area, with a dune covered partially by J. acutus (Fig. 4). Of particular relevance is the presence of a small stream adding some diversity of vegetation and arthropods (Borges et al. 2017). The case of PPCP is completely different, since this is a recently created wetland (Fig. 5), resulting from the removal of large amounts of stones for the construction of the Praia da Vitória harbour, around 1980 (Fig. 6). As a consequence a new ecosystem was created, the quarry of Cabo da Praia (Morton et al. 1997).

Figure 3.  

Paul do Belo Jardim dune area (Photo by Paulo A.V. Borges).

Figure 4.  

Paul do Belo Jardim Juncus effusus area (Photo by Paulo A.V. Borges).

Figure 5.  

Paul da Pedreira do Cabo da Praia (Photo by Paulo A.V. Borges).

Figure 6.  

Paul da Pedreira do Cabo da Praia detail of margins (Photo by Paulo A.V. Borges).

In each of the three wetland areas, transects were setup to allow the sampling of epigean arthropods in the main habitats.

In PPV, three main transects were setup: i) PPV-T200 (Paul da Praia Vitória - Margins) that covers the main margins of the water bodies; ii) PPV-T201 (Paul da Praia Vitória - Island) that covers some of the isolated islands; iii) PPV-T205 (Paul da Praia Vitória - Cerrado São Lazaro) to sample an historical locality with a high diversity of ground-beetle species (Borges 1995; Borges et al. 2017).

In PBJ, two transects were setup: i) PBJ-T203 (Paul do Belo Jardim - Margins), which was located within the Juncus acutus plants; ii) PBJ-T204 (Paul do Belo Jardim - Stream), which was setup in a small stream.

In PPCP, only one transect was setup, PPCP-T202 (Paul da Pedreira do Cabo da Praia - Margins), which covers the main margins of the water.

The beating and sweeping samples were conducted both during the day and night and were undertaken by walking randomly within the sites.

This study was financed by the project LIFE+ (LIFE12 BIO/PT/000110: Ecological Restoration and conservation Infrastructure Green Wet Coast Praia da Vitória) (2013-2018).

This study covers a small coastal area with 3.58 km extension between PPV and PPCP.

In each site, arthropods were sampled during the summers of 2016 and 2017 using a combination of standardised methods inspired by the COBRA protocol (Cardoso 2009):

• Nocturnal active aerial searching (AAS): Four samples were obtained by four trained collectors (Paulo Borges, Mariana Brito, Rosalina Gabriel, César Pimentel) targeting active arthropods found above knee-level by hand, forceps, pooter or brush and immediately transferring them into vials containing alcohol. All the time spent in searching (one hour per researcher) was accounted for.
• Foliage Beating (FB): During daytime, ten samples from each dominant tree or bush were taken. A 110 cm × 80 cm sheet with a frame was used as a drop-cloth (beating tray) and a wooden pole of at least 1.5 m was used to beat tree branches, as high as possible. The plants selected were: A. donax and M. faya in PPV and PPCP and A. donax and J. acutus in PBJ. In 2017, in addition, two samples during the night (FSN) were obtained (one hour each sample covering several plants).
• Foliage sweeping (FS): A round sweep net with an opening diameter of 46 cm was used to sweep bushes and tall herbs. All time spent sweeping or searching for dislodged arthropods was accounted for. Two samples during daytime (FSD) were obtained (one hour each sample). In 2017, in addition, two samples during the night (FSN) were obtained (one hour each sample).
• Pitfall (PIT): Pitfall traps (4.2 cm wide at the top and approximately 7.2 cm deep) were placed immediately outside the perimeter of each lake, spaced 10 metres apart. Traps were filled with 3–4 cm of 100% propylene glycol and left in the field for seven days. Traps were protected from predation, inundation with rainwater and unwanted vertebrate capture by using plates sitting on stilts 2 cm above the ground surface. In PBJ, two transects were performed with 30 traps in the main transect and 15 traps in a secondary transect covering a small stream. In PPV and PPCP, single transects of 30 traps each were setup in the margins of water bodies. In PPV, half of the traps were in the margins of the largest “island”. In 2017, additional traps were setup in Cerrado São Lazaro (PPV-T205 Paul da Praia Vitória).

For each site, a total of four samples of AAS, 20 samples of FB, two samples of FS and 30 main samples of PIT were obtained, totalling 56 samples per site and an overall 168 samples in 2017. Further, in 2017, additional pitfall traps in the PBJ small stream added 15 more samples totalling 183 samples. The main 56 samples per site included the sampling of two main sub-habitats, the aerial vegetation with 26 samples (20 beatings during the day, two sweeps during the day and four night aerial searches) and the ground habitat with 30 pitfall samples.

In 2017, the additional samples made during the night added four samples for each site, totalling 60 samples per site. Accumulation curves were performed and completeness was high for all sites (see Borges et al. 2017).

The correct identification of the sampled taxa is crucial. We followed a three-step process to identify arthropod species: (1) for arthropod orders for which there was taxonomic expertise, one of us (CP) performed morphospecies sorting using a parataxonomy approach (see Oliver and Beattie 1993) with a reference collection; (2) a trained taxonomist (PAVB) corrected all the splitting and lumping errors and identified most of the species; and 3) the morphospecies for which a correct identification was not possible were sent to experts for identification. Taxonomic nomenclature followed the arthropod checklist in Borges et al. (2010) and for the new six taxa the following taxonomic references were used: Lohse 1984, Quinn and Hower 1986, Smaili et al. 2009, Schülke and Smetana 2015.

Terceira Island (Azores), Macaronesia, Portugal

38°42’47.95’; 27°03’40.93’ and .

Arthropods including Diplopoda, Chilopoda, Arachnida (Opiliones; Pseudoscorpiones; Araneae) and Hexapoda (Microcoryphia; Zygentoma; Odonata; Orthoptera; Phasmatodea; Dermaptera; Psocoptera; Hemiptera; Thysanoptera; Neuroptera; Coleoptera; Lepidoptera; Hymenoptera - Formicidae)

Additional information on this study may also be requested to the first author