Standardised inventories of lepidopterans and odonates from Serra da Estrela Natural Park (Portugal) - setting the scene for mountain biodiversity monitoring

Abstract Background Mountain insect biodiversity is unique, but is menaced by different drivers, particularly climate and land-use changes. In mainland Portugal, the highest mountain - Serra da Estrela - is one of the most important biodiversity hotspots, being classified as Natural Park since 1976. Many lepidopteran and odonate species, including rare and protected species, are known to occur in Serra da Estrela, but basic knowledge on their abundance, distribution and ecology is still lacking. Standardised sampling of these communities is crucial to provide valuable biological information to support short-term decision-making for conservation management, setting simultaneously the standards for mountain biodiversity monitoring aiming to tackle the effects of environmental change in the long-term. New information This study reports novel information on lepidopteran and odonate species diversity, distribution and abundance from Serra da Estrela Natural Park (Portugal). Seventy-two lepidopteran and 26 odonate species were sampled in this protected area, including the first findings of Apaturailia (Denis & Schiffermüller, 1775), Macromiasplendens (Pictet, 1843) and Vanessavirginiensis (Drury, 1773). New populations of Euphydriasaurinia (Rottemburg, 1775) and Oxygastracurtisii (Dale, 1834), protected species under the Habitats Directive, were found in this Natural Park and novel distribution and ecological data were collected for most species, including several rare species and subspecies [e.g. Aeshnajuncea (Linnaeus, 1758), Coenonymphaglycerioniphioides Staudinger, 1870, Cyanirissemiargus (Rottemburg, 1775) and Sympetrumflaveolum (Linnaeus, 1758)]. All data were collected using standardised sampling allowing its use as a baseline for biodiversity monitoring in Serra da Estrela.


Introduction
Mountain ecosystems are crucial for global biodiversity conservation since they host high numbers of plant and animal species, including many rare, endemic and those of conservation concern (Hodkinson and Jackson 2005). During the last few decades, research and monitoring of mountain biodiversity has been key to unveiling the drivers of species diversity and community composition and to provide scientifically-supported guidance to manage these unique and fragile ecosystems (Nogués-Bravo et al. 2008, Ashton et al. 2011. For instance, the Global Mountain Biodiversity Assessment (GMBA) initiative has been key on the assessment, conservation and sustainable management of mountain biodiversity (see Payne et al. (2017)). This is extremely important as mountain ecosystems worldwide are menaced by various threats, such as global warming, species introductions, vegetation/land-use changes and water extraction, that often act synergistically (Schmeller 2022). Climate change is considered one of the most impactful threats to mountain biodiversity with many reports stating changes in species composition of mountain communities, upslope shifts of species ranges and even local extinctions in response to temperature increases (Sekercioglu et al. 2008, Chen 2009, Lenoir and Svenning 2015. In addition, human activities have historically played (and still play) an important role as drivers of biodiversity patterns in mountain ecosystems; often mountains supported intensive and/or extensive agricultural, forestry and livestock production practices, were subjected to frequent fires, water extraction and recreational activities. The biodiversity of Iberian mountains, including Serra da Estrela, face this same kind of threats (Wilson et al. 2007, Múrria 2020 and, due to the vulnerability of these ecosystems to environmental change, is key for implementing long-term biodiversity monitoring programmes to tackle changes in abiotic and biotic conditions and supporting decisionmaking for conservation management. Several invertebrate groups have been the target of biodiversity monitoring programmes in mountain ecosystems worldwide since they provide valuable information on the state of the environment in an effective and efficient way. Lepidopterans and (to a less extent) odonates are two invertebrate groups often selected in biodiversity monitoring since they have a well-known ecology and taxonomy, and are cost-effective to survey (Oertli 2008, Kessler 2011, Acquah-Lamptey et al. 2013, Gerlach et al. 2013, Zografou 2014. In this study, we provide novel information on lepidopteran and odonate species diversity, distribution and abundance from representative habitats of Serra da Estrela Natural Park (Portugal) following a standardised sampling protocol, aiming to set a reference work for biodiversity monitoring in this emblematic protected area.

General description
Purpose: We present new taxonomic, distribution and abundance data on the lepidopterans and odonates of Serra da Estrela Natural Park following an extensive survey of adult forms using standardised sampling. The data encompass the elevation gradient of Serra da Estrela, the highest mountain in mainland Portugal and includes information from a variety of habitat types (mountain streams, mountain lakes and montane vegetation) during two consecutive years (2013 and 2014).

Project description
Title: Biodiversity, endemic and protected species associated with mountain lakes and streams of Serra da Estrela Personnel: Mário Boieiro, José Conde and Artur Serrano planned the project and designed the sampling strategy; Sandra Antunes, Albano Soares, Hugo Figueiredo, Ana Lopes, Eva Monteiro, Patrícia Garcia-Pereira, Carla Rego, José Conde and Mário Boieiro participated in fieldwork. Mário Boieiro and Paulo Borges performed the biodiversity data curation in Darwin Core format.

Study area description:
The study took place in Serra da Estrela, the highest mountain in continental Portugal (with 1993 m). Serra da Estrela includes the western extreme of the Iberian Central System which is considered one of the main mountain systems in the Iberian Peninsula. Serra da Estrela is classified as Natural Park since 1976, is part of the Natura 2000 network and its upper areas are included in the Ramsar Convention (ICNF 2022). All study sites are included in the Serra da Estrela Natural Park, encompassing a considerable elevation gradient and habitat diversity. The study area is characterised by Atlantic and Mediterranean climates and different biogeographic regions, being an important area for biodiversity conservation, particularly for montane species (ICNF 2022).
Design description: Sampling of lepidopterans and odonates took place in three main habitat types, namely mountain streams, mountain lakes and montane vegetation ( Fig. 1; Table 1). We sampled the margins of three mountain streams (Fervença, Caniça and Loriga) at three elevation levels (approximately 500, 1000 and 1500m) (Fig. 1a) and 18 mountain lakes (including both natural and artificial lakes), most of them being located in the Central Plateau of Serra da Estrela (Fig. 1b). Lepidopterans and odonates were also sampled from 12 sites of representative montane vegetation of Serra da Estrela, including Juniperus-, Erica-and Genista-dominated scrublands and Nardus-dominated grasslands (Fig. 1c). Overall, 39 sites were sampled during this study (

Description:
The study was carried out in Serra da Estrela Natural Park encompassing the elevation gradient and the diversity of habitats of this protected area.
Sampling description: Lepidopterans and odonates were sampled using a standardised methodology to ensure the possibility of biodiversity data comparison between study sites and to set a reference for mountain biodiversity monitoring in Serra da Estrela Natural Park. Insect sampling followed the Pollard and Yates methodology (Pollard and Yates 1993 ): a 150 m linear transect was set in each study site and adult insects of the target groups were recorded when observed at a distance of up to 5 m ahead of the researcher and 2.5 m from each side. The insects were captured with the help of a sweeping net only in case of need to confirm their species identity, being immediately released afterwards. Sampling was carried out between 10 am and 6 pm and under favourable climatic conditions (i.e. sampling was not performed under rainy, windy, cloudy and hot weather conditions). The data were collected during the seasonal peak of activity of adult lepidopterans and odonates in Serra da Estrela in two consecutive years (2013 and 2014). The three main habitat types sampled in this study. Description: The dataset was published in the Global Biodiversity Information Facility platform, GBIF (Boieiro 2022a). 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 245 records (eventID). This IPT (Integrated Publishing Toolkit) 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 (Boieiro 2022a).

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 (Boieiro 2022b). 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 172 records (eventID). This IPT (Integrated Publishing Toolkit) 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 (Boieiro 2022b).

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 (Boieiro 2022b). 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 520 records (occurrenceID). This IPT (Integrated Publishing Toolkit) 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 (Boieiro 2022b).

Column label 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 Darwin Core standard. organismQuantityType The type of quantification system used for the quantity of organisms.
lifeStage The life stage of the organisms captured.

establishmentMeans
The process of establishment of the species in the location, using a controlled vocabulary: 'native', 'introduced', 'endemic', "unknown". taxonRank Lowest taxonomic rank of the record.
scientificNameAuthorship Name of the author of the lowest taxon rank included in the record.

Results
During the two-year study, we observed 7339 adult insects from 98 species of the two target groups (Lepidoptera and Odonata) in Serra da Estrela Natural Park. Overall, we identified 72 lepidopteran species (3971 observed individuals) from five different families (Table 2) and 26 odonate species (3368 observed individuals) from ten different families (Table 3), being 11 zygopterans and the remaining 15 anisopterans. We report for the first time the finding of Apatura ilia, Macromia splendens and Vanessa virginiensis in this protected area, jointly with the location of new populations of the Habitats Directive protected species Euphydrias aurinia and Oxygastra curtisii (Fig. 2a).

Family Species/Subspecies Abundance Occupancy
Hesperiidae  species in Portugal and both classified as threatened (Maravalhas and Soares 2013), were found in several sites, mostly located in the Central Plateau of Serra da Estrela (Fig. 2c, d). Several lepidopteran and odonate species (including the newly-recorded species Apatura ilia, Macromia splendens and Vanessa virginiensis) were found to be rare in the study area, occurring in low abundance in just a few sites.  The species abundance distributions of the two study groups show a bimodal pattern with high number of species in moderately low and moderately high abundance classes; fewer species were found to be low-or high-abundant (Fig. 3a). Five lepidopterans, including the montane Satyrus actaea (Esper, 1781), occurred in high abundance (> 256 individuals) in the study area and two odonates [Enallagma cyathigerum (Charpentier, 1840) and Libellula quadrimaculata Linnaeus, 1758] were also very abundant (> 512 individuals). The occupancy frequency distributions of the two study groups followed a common pattern: most species were found in a few number of sites and a scarce number of species was widespread (Fig. 3b). Only two lepidopterans, Colias croceus (Geoffroy, 1785) and Pieris rapae (Linnaeus, 1758) were found in most study sites (respectively 38 and 36, out of 39).
Average values of lepidopteran and odonate species richness were higher in mountain streams and lakes (Fig. 4). Fewer species were detected in sites in montane vegetation.

Discussion
The diversity of lepidopteran and odonate species in Serra da Estrela is one of the highest in Portugal since the elevation gradient of this mountain determines marked differences in abiotic and biotic conditions at relatively short distances, thus driving habitat diversity, species distributions and spatial patterns of biodiversity (Ferreira et al. 2009). Additionally, due to its geophysical characteristics, Serra da Estrela has several montane habitat types that are exclusive or poorly represented in the country (Jansen 2002), where we can find a b Species abundance distributions (SADs) and occupancy frequency distributions (OFDs) of lepidopterans and odonates from the study sites in Serra da Estrela.
a: SADs of lepidopterans and odonates. Data were binned in modified log2 abundance classes following Gray et al. (2006). b: OFDs of lepidopterans and odonates. Data were grouped in site occupancy frequency classes, each comprising 12.5% of the total number of sampling locations.
During the two-year study, we sampled the lepidopteran and odonate communities from 39 sites in Serra da Estrela Natural Park, improving the species inventory by recording three new species to this protected area and collecting novel data on species abundance, distribution and ecology for nearly one hundred species, including two protected under the Habitats Directive. Interestingly, a number of lepidopteran and odonate species were found in low abundance in a few number of sites (Tables 2, 3; Fig. 3), suggesting the need to further investigate the distribution and population size of these species in Serra da Estrela. Despite the occurrence of several odonate and lepidopteran species of conservation concern in Serra da Estrela (both listed in the Habitats Directive or classified as threatened by national experts, see Maravalhas (2003), Maravalhas and Soares (2013)), we are unaware of studies targeting the collection of crucial baseline data on species abundance, distribution and threats that are much needed to support their conservation in this Natural Park. In addition, it will be important to sample a higher number of sites and habitats in this large protected area (with nearly 90,000 ha) to ascertain the rarity of several species that may in fact be undersampled. The combined analysis of species abundance distributions and occupancy frequency distributions also highlighted a few species that are relatively abundant and widespread in Serra da Estrela, like the odonates Enallagma cyathigerum and Libellula quadrimaculata and the lepidopterans Colias croceus and Pieris rapae. These species are common in the country (Maravalhas 2003, Maravalhas and Soares 2013) and seem to cope with the wide variety of ecological conditions through the elevation gradient of Serra da Estrela. Not surprisingly, we found a higher average number of odonate and lepidopteran species in mountain streams and lakes than in montane vegetation. Odonates depend on these aquatic ecosystems for reproduction and larvae development, while lepidopterans seem to benefit from a larger diversity of host plants.
Our study presents baseline information on species abundance and distribution following standardised sampling in representative habitats of Serra da Estrela, aiming to set a reference for long-term monitoring of biodiversity in this mountain. The biodiversity of Serra da Estrela faces several threats, particularly due to climate change, wildfires, the spread of invasive species and excessive water extraction, all of which are crucial for assessing their impact on montane plant and animal communities. Both odonates and lepidopterans are important bioindicators and many studies showed that they may provide valuable information as global change sentinels since their populations respond quickly to environmental change and at very fine scales (Hassall 2015, Hill et al. 2021).