I am a scientific researcher at Research Centre on Geo-Spatial Science (CICGE-Centro de Investigação em Ciências Geo-Espaciais) of the University of Porto.

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GIS for Spatial Biology

Spatial Biology analyses how space influences species, communities, individuals, and any other ecological processes. Geographical Information Systems (GIS) are essential in this discipline, together with remote sensing, spatial statistics, and ecological niche modelling. In this chapter, we present a detailed review about the importance of GIS in spatial biology. Several case studies are organised at three levels, depending on the sampling unit: species, populations, and individuals. Examples are offered on species' distributions atlases; determination of chorotypes, biogeographical areas, and protected areas; modelling of species distributions, range shifts, species' dispersions, species' invasions, and hybrid zones; phylogeography and systematics; landscape connectivity; home ranges, and modelling road-kills.

Sillero, N.; Vale, C.G.; Beukema, W. (2018): GIS for Spatial Biology: the geographical component of life. In: Teodoro, A.C. (Ed.): GIS - An overview of Application. Frontiers in Information System, 201(1): 149-183. eBook Series. Bentham Science.

Parthenogenetic Darevskia lizards also mate

Several Caucasian rock lizards of the genus Darevskia of hybrid origin are known to reproduce parthenogenetically. Local communities can be composed exclusively of parthenogens, though syntopy with bisexual members of the genus may occur. In some localities, reproduction between bisexual and parthenogenetic Darevskia has been previously reported based on lizard intermediate morphology and karyology (3n, 4n). However, the frequency of such heterospecific matings remains unknown. We indirectly quantified the reproductive interactions through the inspection of copulation marks in females in a mixed Darevskia community from Kuchak (Armenia) composed of two hybrid parthenogens (D. armeniaca and D. unisexualis), one bisexual species (D. valentini) and their putative backcrosses.

Carretero, M.; García-Muñoz, E.; Argaña, E.; Freitas, S.; Corti, C.; Arakelyan, M.; Sillero, N. (2018): Parthenogenetic Darevskia Lizards Mate Frequently if they have the Chance. A Quantitative Analysis of Copulation Marks in a Sympatric Zone. Journal of Natural History 52 (7–8): 405–413.

Distribution of smooth newt species complex

The ‘smooth newt’, the taxon traditionally referred to as Lissotriton vulgaris, consists of multiple morphologically distinct taxa. Given the uncertainty concerning the validity and rank of these taxa, L. vulgaris sensu lato has often been treated as a single, polytypic species. A recent study, driven by genetic data, proposed to recognize five species, L. graecus, L. kosswigi, L. lantzi, L. schmidtleri and a more restricted L. vulgaris. The Carpathian newt L. montandoni was confirmed to be a closely related sister species. We propose to refer to this collective of six Lissotriton species as the smooth newt or Lissotriton vulgaris species complex. Guided by comprehensive genomic data from throughout the range of the smooth newt species complex we 1) delineate the distribution ranges, 2) provide a distribution database, and 3) produce distribution maps according to the format of the New Atlas of Amphibians and Reptiles of Europe, for the six constituent species. This allows us to 4) highlight regions where more research is needed to determine the position of contact zones.

Wielstra, B., Canestrelli, D., Cvijanović, M., Denoel, M., Fijarczyk, A., Jablonski, D., Liana, M., Naumov, B., Olgun, K., B., Pabijan, M., Pezzarossa, A., Popgeorgiev, G., Salvi, D., Si, Y., Sillero, N., Sotiropoulos, K., Zieliński, P., Babik, W. (2018): The distributions of the six species constituting the smooth newt species complex (Lissotriton vulgaris sensu lato and L. montandoni) – an addition to the New Atlas of Amphibians and Reptiles of Europe. Amphibia-Reptilia.

Home ranges of Darevskia lizards

We analysed the home ranges of a community of Darevskia rock lizards composed of a bisexual species (D. valentini), two parthenogenes (D. armeniaca and D. unisexualis), and two backcross forms between bisexual and unisexual forms. We estimated home range (HR) areas of ink-marked, GPS-located lizards using Minimum Convex Polygon (MCP) and 95% of the locations for those individuals with five or more sightings. We compared home range size, perimeter, and total travelled distance between species accounting for lizards' morphology. We also counted the number of individual HRs intersecting other individual HRs and those with no overlap and measured the overlap proportion among MCP intersections. The bisexual D. valentini was the species with the largest home ranges, travelled distances, and the most intersections. No differences between unisexual species and backcrosses were recorded for any comparison. In males, HR size and perimeter were related to morphological characteristics. Contrarily to what has been described in allopatry, unisexual species showed smaller HR and less overlaps than sympatric bisexual species.

Sillero, N.; Corti, N.; Carretero, M.A. (2016): Home ranges of parthenogenetic and bisexual species in a community of Darevskia lizards. Zoology of the Middle East 62(4): 306–318.

Spatial segregation in a community of lizards

Plant and animal individuals can have a random, regular, or clustered distribution across space. The analyses of these patterns are important to understand how environment influences the spatial structure of species communities. We studied the local spatial segregation in a lizard community  that is composed by four species in Salamanca (Spain). We inferred if habitat and / or competition are segregating factors. We used Ripley’s K function to determine the distance threshold of clustering of the whole community and of each species separately, Delaunay’s triangulation (using as clustering distance threshold the Nearest Neighbor Index) to identify spatial species’ clusters, and an overlapping analysis (using buffers around species records), as well as a distance comparison analysis (among intra‐species and inter‐species distances), to measure the species’ spatial segregation.

Sillero, N.; Gomes, V. (2016): Living in clusters: the local spatial segregation of a lizard community. Basic and Applied Herpetology 30, 61-75.

Effects of partial distributions on ecological niche models.

Ecological niche models (ENM) will successfully identify a species' ecological niche, provided that important assumptions are fulfilled, namely environment equilibrium and niche equality across the distribution. Violations may seriously affect ENM reliability, leading to erroneous biogeographic conclusions and inappropriate conservation prioritisation. We evaluate the robustness of ENMs against incomplete knowledge of distribution with a real example, the threatened Iberian lizard Podarcis carbonelli, whose distribution was gradually discovered over a long time period.

Carretero, M.A.; Sillero, N. (2016): Evaluating how species niche modelling is affected by partial distributions with an empirical case. Acta Oecologica 77, 207-216.

A robotic device for detecting amphibians roadkills.

We presents a road surface scanning system that operates with a trichromatic line scan camera with light emitting diode (LED) lighting achieving road surface resolution under a millimeter. Sustained operating trailer speeds of up to 30 km/h are achievable without loss of quality at 4096 pixels’ image width (1 m width of road surface) with 250 μm/pixel resolution. This article is part of the Roadkills project funded by by the Portuguese Science and Technology Foundation (FCT).

Lopes, G.; Ribeiro, A.; Sillero, N.; Gonçalves-Seco, L.; Silva, C.; Franch, M.; Trigueiros, P. (2016): High Resolution Trichromatic Road Surface Scanning with a Line Scan Camera and Light Emitting Diode Lighting for Road-Kill Detection. Sensors 16(4): 558.

The use of remote sensing in the spatial ecology of Iberian lizards.

Remote sensing is applied as main source of environmental data to analyse the home ranges and their influence in the escape behaviour of Iberian lizards. Fieldwork was conducted inside a 400 m2 mesocosm. A total of 3016 GPS points were recorded and processed into a Digital Elevation Model (DEM), with a pixel resolution of 2 cm. Then, 1156 aerial photos were taken and processed to create an orthophoto. A refuge map, containing possible locations for retreats was generated with supervised image classification algorithms, obtaining four classes (refuges, vegetation, bare soil and organic soil). Fifty data-loggers were randomly placed, recording evenly through the area temperature and humidity every 15’. Some lizards escaped outside their home ranges, but at close distances.

Dos Santos, R.; Teodoro, A.C.; Carretero, M.A.; Sillero, N. (2016): Remote sensing as a tool to analyse lizard's behaviour. Proc. SPIE 9998, Remote Sensing for Agriculture, Ecosystems, and Hydrology XVIII, 99981Z.

Join us in the second edition of our course on ecological niche modelling!!

18-22 July 2016
Observatório Astronómico Prof. Manuel de Barros
Faculty of Sciences • University of Porto
Alameda do Monte da Virgem, Vila Nova de Gaia, Portugal

More information on https://sites.google.com/site/neftalisillero/Home/enm-course

Biogeographic analysis of Caucasian rock lizards (genus Darevskia)

Darevskia rock lizards include both sexual and parthenogenetic species, mostly distributed in the hetero- geneous and ecologically diverse Caucasus. The parthenogenetic species originated via directional hybri- dogenesis, with only some of the sexual species known to serve as parentals. However, it remains unclear when and where these events happened and how many parental lineages were involved. We performed a multilocus phylogeographic analysis together with Maxent models on the parthenogens D. unisexualis, D. bendimahiensis and D. uzzeli, and their putative maternal species D. raddei.

Freitas, S., Rocha, S., Campos, J., Ahmadzadeh, F., Corti, C., Sillero, N., Ilgaz, Ç., Kumlutaş, Y., Arakelyan, M., James Harris, D., Carretero, M.A. (2016) Parthenogenesis through the Ice Ages: a biogeographic analysis of Caucasian rock lizards (genus Darevskia). Molecular Phylogenetics and Evolution 102, 117–127.

Spatial Biodiversity Patterns of Madagascar's Amphibians and Reptiles

Madagascar has become a model region for testing hypotheses of species diversification and biogeography, and many studies have focused on its diverse and highly endemic herpetofauna. We combine species distribution models of a near-complete set of species of reptiles and amphibians known from the island with body size data and a tabulation of herpetofaunal communities from field surveys to infer and compare biogeographic patterns in these groups.

Brown JL, Sillero N, Glaw F, Bora P, Vieites DR, Vences M (2016) Spatial Biodiversity Patterns of Madagascar's Amphibians and Reptiles. PLoS ONE 11(1): e0144076.

Application of spatial statistics to lizard thermoregulation behaviour

In heliothermic ectotherms, such as lizards, solar radiation is a crucial resource used in thermoregulation and can be limited, especially in species inhabiting forest habitats where open areas suitable for basking are scarce. Lizards Podarcis muralis and Iberolacerta horvathi are similar in morphology and ecology, but show some degree of dissimilarity in physiology, have a widely sympatric distribution but with a partial altitudinal segregation pattern (altitudinal contrasting species densities). We applied spatial statistics to analyse movements in lab experiments with adult male lizards of both species were set up to first test if the presence of conspecifics or heterospecifics has an influence on their thermoregulation.

Žagar, A., Carretero, M.A., Osojnik, N., Sillero, N., Vrezec, A., 2015. A place in the sun: interspecific interference affects thermoregulation in coexisting lizards. Behavioral Ecology and Sociobiology 69, 1127–1137.

NA2RE project

The NA2RE project compiles updated data about the distribution of European amphibians and reptiles. NA2RE is an evolution of the Atlas of European Amphibians and Reptiles published by the Societas Europaea Herpetologica in 1997 and reedited in 2004 (with a new chapter about taxonomical changes). NA2RE is based in a system of distributed online databases. Find more information at:

Sillero, N., Oliveira, M.A., Sousa, P., Sousa, F., Gonçalves-Seco, L. (2014): Distributed database system of the New Atlas of Amphibians and Reptiles in Europe: the NA2RE project. Amphibia-Reptilia 35 (1): 33-39.

The New Atlas of Amphibians and Reptiles in Europe

A precise knowledge of the spatial distribution of taxa is essential for decision-making processes in land management and biodiversity conservation, both for present and under future global change scenarios. For European amphibians and reptiles, the last comprehensive compilation of their distribution was the atlas by Gasc et al. published in 1997 by the Societas Europaea Herpetologica (SEH). The maps of this standard work have however not been made available in digital formats suitable for analysis in geographic information systems, and due to taxonomic progress and intensified mapping efforts at regional and national levels, are partly outdated. As a first step to an interactive atlas grounded on a distributed database of records (http://na2re.ismai.pt/) the mapping committee of SEH has compiled a dataset of over 384 000 grid and locality records distributed across 40 European countries. In a paper published in Amphibia-Reptilia we analyze these data from a biogeographical perspective and, most importantly, identify taxonomic and spatial gaps of knowledge which require intensified research. To stimulate further mapping and research projects, the preliminary maps for all European amphibian and reptile species are made available open-access on the journal webpage of Amphibia-Reptilia and are also available from the link below, including GIS-shapefiles for free use.

Sillero, N., J. Campos, A. Bonardi, C. Corti, R. Creemers, P.-A. Crochet, J. Crnobrnja Isailovic, M. Denoël, G. F. Ficetola, J. Gonçalves, S. Kuzmin, P. Lymberakis, P. de Pous, A. Rodríguez, R. Sindaco, J. Speybroeck, B. Toxopeus, D.R. Vieites, M. Vences (2014): Updated distribution and biogeography of amphibians and reptiles of Europe. Amphibia-Reptilia 35: 1-31.

Spatial structure analysis of a reptile community with airborne LiDAR data

The analysis of the spatial structure of animal communities requires spatial data to determine the distribution of individuals and their limiting factors. Data from airborne LiDAR (Light Detection and Ranging) sensors can provide digital models of ground and vegetation surfaces with pixel sizes of less than 1 m. We present the first study in terrestrial herpetology using LiDAR data where we identified the spatial patterns of a lizard community of four species and to determine how the habitat is influencing the distribution of the species spatially.

Sillero, N., Gonçalves-Seco, L. (2014): Spatial structure analysis of a reptile community with airborne LiDAR data, International Journal of Geographical Information Science, 28:8, 1709-1722.

What does ecological modelling model?

Species distribution model is the term most frequently used in ecological modelling, but other authors used instead predictive habitat distribution model or species-habitat models. A consensual ecological modelling terminology that avoids misunderstandings and takes into account the ecological niche theory does not exist at present. Moreover, different studies differ in the type of niche that is represented by similar distribution models. I propose to use as standard ecological modelling terminology the terms “ecological niche”, “potential niche”, “realized niche” models (for modelling their respective niches), and “habitat suitability map” (for the output of the niche models). Therefore, the user can understand more easily that models always forecast species' niche and relate more closely the different types of niche models.

Sillero, N. (2011): What does ecological modelling model? A proposed classification of ecological niche models based on their underlying methods. Ecological Modelling 222, 1343–1346.