Species inventory of Arthropoda across anthropogenically-impacted habitats in the Azores archipelago

Plant identifications were performed by the botanist Luis Silva, from the University of the Azores. Arthropoda sampling was performed by José A. P. Marcelino, António O. Soares, Patrícia V. Garcia and Roberto Resendes. Sorting, morphospecies IDs, image gallery stocks, digital data assembling and 96% EtOH-based collections, required a substantial number of technical staff (circa 15 people from 2010 to 2013). Species identifications were performed, initially, by José A. P. Marcelino, corroborated by Fernando Pereira and Paulo A. V. Borges using a reference collection (Dalberto Teixeira Pombo insect collection from the University of the Azores) and, subsequently, by reference taxonomists on the different Arthropoda groups, i.e. Collembola (Felipe Soto-Adames, Florida Dept. Agriculture and Consumer Services, USDA, Florida, USA), Araneae (Paulo Borges, University of the Azores), Hymenoptera (Kees van Achterberg, National History Museum Netherlands and Vladimir Žikić, University of Niš, Serbia), Coccinellidae (António O. Soares and Isabel Borges, University of the Azores), Staphylinidae (Volker Assing, Hannover, Germany) and one new record of Carabidae for the Azores by Bob Davidson at Carnegie Museum on Natural History, USA. Collembola were also genetically profiled (Marcelino et al. 2011), as well as Staphylinidae (Marcelino et al. 2016).

We selected the Islands, based on the relative proportion of land used in agriculture and pristine areas (based on published data by Costa et al. 2014), taking into consideration all possible combinations, i.e. São Miguel (SMG), with a high proportion of land allocated to pastureland (61%) and a low proportion of scattered native and naturalised habitats (19.1%); (ii) Terceira (TER), with high proportion of pastureland (66.9%) and a similar proportion of native and naturalised habitats as SMG, but less fragmented (21.3%); (iii) Pico (PIC), with high proportion of pastureland (50.3%) and medium/high proportion of native habitats at higher elevation (35.5%); (iv) Flores (FLO), with scarce agricultural development (17.7%) and a high proportion of native and naturalised habitats (43%); and, (v) Santa Maria (SMR), with high proportion of agricultural land (56.7%) and a low proportion of native and naturalised habitats (17.3%) (Table 1).

The importance of incorporating ecological gradients, such as an anthropogenic impact gradient, in biodiversity and conservation projects, has been previously highlighted. They constitute valuable scenarios to infer possible causes for the distribution of species across the landscape (Ulrich et al. 2009). We therefore selected habitats that represented a gradient of increasing anthropogenic impact and management intensity. Nine habitat types, divided between herbaceous and arborescent habitats, were selected to represent a comprehensive range of the flora and fauna communities. We determined consistency, prevelance and fidelity of a given plant species across all habitats to define them, based on their flora. We used a metric called IndVal and developed another called SiteVal which can now be used to assign a location to a given habitat (and anthropogenic level of influence) (see more details in Marcelino et al. 2013, Marcelino et al. 2014, Silva et al. 2017). The herbaceous habitat gradient (Table 2) ranged from natural meadows (MED) to corn fields (COR). The arborescent habitat gradient (Table 2) ranged from natural pristine forests of Laurus azorica (NAT) to orchards of Citrus sp. (ORC). Pristine meadows were not present on Santa Maria and Terceira and semi-natural pastures at low altitude (SNPL) were used as a surrogate for MED on these Islands.

In order to obtain the maximum information on arthropod biodiversity, all strata present at a given habitat type were sampled, i.e. micro-epigean fauna (Berlese-Tullgren trapping), soil fauna (Pitfall trapping), aerial vagility fauna (Suction with an aspirator) and canopy fauna (sweeping nets).

One Island per week was sampled during the summer 2009 (July-August). This eliminated seasonal effects in the sampling. The total number of samples was 4800 [80 sampling sites x 4 different types of traps x 15 samples per site].

The samples were subsequently processed in laboratory facilities and assigned to morphospecies groups, progressing to higher taxonomic degrees of identifications. Species richness and abundance were recorded. Species accumulation curves were performed for inventory completeness using EstimateS (using the ratio of observed to the estimated species richness with the non-parametric estimator Jackknife) (Colwell 2013). Inventory completeness was 70-75% for Staphylinidae and Collembola (Marcelino et al. 2011, Marcelino et al. 2016), reaching 80% for Araneae and Hymenoptera parasitoids (data not published).

This study was financially supported by FLAD – Fundação Luso-Americana para o Desenvolvimento and by the Direção Regional da Ciência e Tecnologia (DRCT) & PROEMPREGO, of the Azores. This study was also financed by FEDER in 85% and by Azorean Public funds by 15% through Operational Programme Azores 2020, under the following projects AZORESBIOPORTAL –PORBIOTA (ACORES-01-0145-FEDER-000072), and under the project ECO²-TUTA (ACORES-01-0145-FEDER-000081).

Five Islands of the Azores: Santa Maria, São Miguel, Terceira, Pico and Flores.

Suction (SU), sweeping (SW) and soil (BT) sampling were obtained in parallel with the pitfall traps (PF) in the sites previously listed (Table 1), in equal numbers of samples and distance.

SU and SW were done to record species at strata other than the epigeic stratum. SU was made with a hand-held aspirator (Stihl BG55), collecting the arthropods in shrubs, when available. SU was made individually for ca. 8 seconds, at each of four exposures (i.e. N, S, W, E) of the shrub or agro-culture plant. The specimens from all four cardinal exposures were transferred to a single cup for each SU and SW sampling spot, respectively. SW was made by gently sweeping with a 64 cm diameter sweeping net.

Berlese-Tullgreen sampling (BT) was made by collecting ca. 100 grams of soil litter per sampling unit (15 samples for each transect established at PF sampling spots). Samples were immediately stored in a cooler to avoid proliferation of saprophytic fungi and sent by air transportation to the Department of Biology, University of the Azores, Ponta Delgada where they were placed in a cooling chamber at 4°C for subsequent processing in BT traps. BT trap units consisted of two plastic darkened containers, assembled together to provide an upper vented area (14 cm diameter x 11.5 cm high) with 4 openings (1 cm diameter covered with a 0.3 x 0.3 mm diameter mesh) and coupled with a 15 W lamp on top. The lower collecting area (13 cm diameter x 10 cm high) was partially filled with ca. 80 ml of the same mixture used in PF. Litter samples were placed on a 1.8 x 1.8 mm mesh, attached to a plastic funnel positioned in the assembling zone between the two halves of the device. In order to avoid heat and dryness, Collembola and other micro-arthropods crawled downwards to the littler sample and dropped through the funnel into the collecting mixture. Litter samples remained for 72 h in BT before specimen sorting at laboratory facilities.

Two parallel transects with fifteen pitfall traps (PF) were placed in 150 x 150 m geo-referenced plots. PF consisted of plastic cylinder cups 78 mm deep and 42 mm diameter filled with ca. 80 ml of a mixture of 96% Ethanol and 0.05% liquid detergent. PFs were buried in the soil so that the lid was flush with the surface and covered with a plastic plate at ca. 3 cm height, to avoid desiccation, flooding or insectivore predation. Traps remained in the soil for 7 days prior to collection. For each habitat type and Island, two replicate sites were monitored (with a minimum distance of 5 km apart), for a total of 80 sampling sites (i.e. 5 Islands x 8 habitat types per Island x 2 sites for each habitat type).

All specimens where stored in 96% EtOH in order to maintain viability for future genetic and/or taxonomic work, as well as voucher exchanges with other institutions.

Identifications were conducted in a progressive higher degree of taxonomy resolution, i.e. 1) morphospecies were generated and, concomitantly, an ongoing web-based image gallery stock was created (at www.eden-azores.webs.com). This secured consistency in assigning specimens to morpho-species without duplications; 2) voucher specimens of all morphospecies were taxonomically assigned to a genus and, if possible, to species level; 3) species of Collembola and Staphylinidae were genetically profiled to match genetic and morphological IDs; 4) All voucher specimens where sent to taxonomist referees in the respective Order, family, genus or group (taxonomists listed in the Personnel section of this report), which corroborated identifications from steps 1, 2 and 3.

Azores (Portugal). Islands of Santa Maria, São Miguel, Terceira, Pico and Flores

36.906 and 39.589 Latitude; -31.311 and -24.961 Longitude.

Widely distributed Arthropoda groups are reported, i.e. Araneae, Collembola, Hymenopteran parasitoids and beneficial Coleoptera (e.g. Carabidae, Coccinellidae, Staphylinidae). In addition, Dermaptera, Hemiptera, Neuroptera, Orthoptera, Psocoptera and Thysanoptera. Information can be retrieved in the data resources below (Table of Species Occurrence).