RESEARCH ARTICLE Mark-release-recapture meets Species Distribution Models: Identifying micro- habitats of grassland butterflies in agricultural landscapes 1 2 3 Jan C. HabelID *, Mike Teucher , Dennis RoÈ dder 1 Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, School of Life Sciences Weihenstephan, Technische UniversitaÈt MuÈnchen, Freising, Germany, 2 Department of Remote Sensing and Cartography, Institute of Geosciences and Geography, UniversitaÈt Halle, Halle, Germany, 3 Zoologisches Forschungsmuseum Alexander Koenig, Bonn, Germany a1111111111 * [email protected] a1111111111 a1111111111 a1111111111 Abstract a1111111111 Habitat demands and species mobility strongly determine the occurrence of species. Sed- entary species with specific habitat requirements are assumed to occur more patchy than mobile habitat generalist species, and thus suffer stronger under habitat fragmentation and OPEN ACCESS habitat deterioration. In this study we measured dispersal and habitat preference of three selected butterfly species using mark-release-recapture technique. We used data on spe- Citation: Habel JC, Teucher M, RoÈdder D (2018) Mark-release-recapture meets Species Distribution cies abundance to calculate Species Distribution Models based on high-resolution aerial Models: Identifying micro-habitats of grassland photographs taken using RGB / NIR cameras mounted on a UAV. We found that microhabi- butterflies in agricultural landscapes. PLoS ONE 13 tats for species with specific habitat requirements occur spatially restricted. In contrast, suit- (11): e0207052. https://doi.org/10.1371/journal. able habitats are more interconnected and widespread for mobile habitat generalists. Our pone.0207052 models indicate that even managed grassland sites have comparatively little habitat quality, Editor: Petr Heneberg, Charles University, CZECH while road verges provide high quality micro-habitats. In addition, dispersal was more REPUBLIC restricted for specialist butterfly species, and higher for the two other butterfly species with Received: June 21, 2018 less ecological specialisation. This study shows synergies arising when combining ecologi- Accepted: October 9, 2018 cal data with high precision aerial pictures and Species Distribution Models, to identify Published: November 28, 2018 micro-habitats for butterflies. This approach might be suitable to identify and conserve high Copyright: © 2018 Habel et al. This is an open quality habitats, and to improve nature conservation at the ground. access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All data underlying Introduction the study are within the paper and its Supporting Habitat configuration and habitat quality significantly influence the occurrence and persis- Information files. tence of species [1]. Today, many remaining habitats are small and geographically isolated Funding: The authors received no specific funding from each other, as most semi-natural calcareous grasslands across agricultural landscapes of for this work. Central Europe [2]. Recent studies showed that continuing fragmentation of remaining habi- Competing interests: The authors have declared tats and further intensification of agriculture in between lead to barriers for many species [3]. that no competing interests exist. Furthermore, habitat quality in remaining habitat patches becomes deteriorated due to the PLOS ONE | https://doi.org/10.1371/journal.pone.0207052 November 28, 2018 1 / 10 High precision SDMs for butterfly conservation influx of pesticides, pollutants and nitrogen [4±5]. These factors drive species losses and the reduction of species abundances, as identified for grassland butterfly species, particularly on calcareous grasslands [6]. This situation becomes even more precarious due to the fact that most remaining habitats are small and geographically isolated and many butterfly species show sedentary dispersal behaviour, with limited migrations across the landscape matrix [7± 8]. This may accelerate local extinctions with the result that many potential suitable habitats remain `un-occupied [9]. Species demanding specific habitat requirements and with restricted dispersal suffer in particular under habitat fragmentation and the deterioration of habitat qual- ity [10]. In nature conservation, especially high quality habitats considered a priority for habitat management and the protection of sites. Remote sensing techniques and high resolution aerial photographs may help to identify such high value sites. In this study we measure the availabil- ity of suitable microhabitats for three butterfly species differing in habitat specialisation and dispersal behaviour [11±20]. To identify these microhabitats we assessed species abundances at points which were randomly set. In parallel, we performed mark-release-recapture tech- niques to quantify the dispersal behaviour of our targeted species. To identify the spatial com- position availability of microhabitats we used high-resolution aerial pictures taken from a UAV equipped by RGB / NIR cameras. Subsequently, Species Distribution Models were run (i) based on species' presence/absence, and (ii) species abundance of individuals of the respec- tive species reflecting home range preferences. We will interpret our model-outcome against the background of species specific dispersal behaviour obtained from our mark-release-recap- ture data. Based on our data we test the following hypothesis: (i) Suitable habitats for specialist butterflies occur patchy and are mainly restricted to managed sites if compared with habitat generalist butterflies; (ii) Specialist species show more restricted dispersal behaviour if com- pared with generalist species. Material and methods Study species Our selected butterfly species occur in high population densities across our study area. Mela- nargia galathea is a common habitat generalist found at flower-rich fresh to dry grassland sites, which uses a comparatively broad ecological niche and occurs in high densities in exten- sively used grasslands, along road verges and forest edges [11±14]. Caterpillars feed on differ- ent species of grasses [11±14]. The species can be classified as a mobile butterfly [13], see also previous MRR studies [15]). The two other butterflies, Erebia medusa and Coenonympha arca- nia are more specialised than M. galathea. Erebia medusa occurs at nutrient-poor semi-open habitats like extensively used meadows and young fallows, fens, marshy forest meadows and clear cuttings and needs wind protecting structures as forest edges or hedge rows [16]. Its lar- val food plants are grasses (Poaceae mainly) [12]. The butterfly species requires specific open sites within the swards for oviposition. Eggs are deposited mostly more than 10 cm above ground so that moving before the eclosion of the caterpillars (i.e. before mid- to end-June) will destroy the next generation [16]. Consequently, the species decreases strongly on the landscape level due to agricultural intensification and afforestation [17]. This butterfly shows a sedentary dispersal behaviour [18]. Similarly specialised and sedentary is Coenonympha arcania. This butterfly occurs restricted to structure-rich, nutrient-poor grasslands, especially near forests, clearings in flood plain woodlands, but also in light sunny forests with a lot of understory [13]. Its larvae feed on various grass species. Coenonympha arcania is strongly declining in some regions of Central Europe due to the vanishing of extensively used fresh grasslands and young heterogeneous fallow land (mosaic of woody-open structures) [17, 19±20]. PLOS ONE | https://doi.org/10.1371/journal.pone.0207052 November 28, 2018 2 / 10 High precision SDMs for butterfly conservation Study area As study area we selected the managed calcareous grassland site `Dietersheimer Brenne (45ha), surrounded by agricultural land, forest, roads and paths. Our study area is located south of the city Freising (48.29N, 11.68E). The `Dietersheimer Brenne is characterised by high intensity of solar radiation, high temperature peaks, and dry climatic conditions [21]. Mesobromion is the dominating vegetation formation which consists of a species rich flora and fauna, including many rare and protected taxa [2]. Current conservation management antagonise the reforestation of this grassland site. Aerial pictures Aerial pictures were taken with a UAV (DJI Phantom 3 Professional) equipped with a 3-axis gimbal, standard DJI RGB camera (1/2.3º CMOS sensor), and a modified DJI camera for acquisition of Near Infrared Imagery (3.97mm f/2.8 82Ê HFOV Red + NIR channel) [22]. The flight was conducted in August 2017 at a height of 60 m aboveground using an orthogonal camera attachment with 12MP resolution, 94Ê field of view (FOV), 20mm focus equivalent and 2s time lapse interval while flying with 5 m/s. Flight path was prepared using the software Litchi for DJI Phantom [23], with stop and turn curve mode settings. Missions were prepared with minimum 50% overlap between consecutive pictures and between neighbouring flight lines to minimize lens distortion effects on results. In total, four flight lines in one flight mis- sion (15 min) were conducted with each flight line of 250 m length composed as rectangular shape. For NIR photographs we used the MAPIR Camera Reflectance Calibration Ground Target Package