1. Exploration of the Ecological Niche of
Chacoan Species in Environmental Space
Pinotti, Juan Diego1,2, Ferreiro, Alejandro Manuel1,2 ,
Chiappero, Marina B. 1,2, Gonzalez-Ittig, Raul E. 1,2
1: Universidad Nacional de Córdoba, Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Genética de Poblaciones y Evolución.
Córdoba, Argentina.
2: Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Diversidad y Ecología Animal (IDEA). Córdoba,
Argentina.

2. Introduction
The Chaco is the only subtropical dry forest in the planet, it contains high levels of
endemism and diversity of species1, 2. The destruction of chacoan habitats has been
identified as one of the worst environmental disasters in South America3, 4.
Ecological niche models (ENMs) allow relating species presences data with
information about the environmental characteristics of these ocurrences5. Several
studies had implemented ENMs to infer the potential distribution of chacoan species6, 7,
but all of them were focused in the geographic space. Regarding that niches are
modelled in environmental space8, the characterization of the environmental niche of
chacoan species would bring new information about the biogeography of this region.
Based on this, we modelled the niches of four predominantly Chacoan taxa with a
minimum ellipsoid model (MVE) in the environmental space. We also calculate niche
volumes and overlap between them.
1.Kuemmerle et al. (2017). Forest conservation: remember gran chaco. Science, 355(6324), 465-465. 2. Morrone, J. J. (2017). Neotropical biogeography: regionalization and evolution. CRC Press.
3. Taber et al (1997). A new park in the Bolivian Gran Chaco–an advance in tropical dry forest conservation and community‐based management. Oryx, 31(3), 189-198. 4. Vallejos et al (2014).
Dynamics of the natural cover transformation in the Dry Chaco ecoregion: A plot level geodatabase from 1976 to 2012. Journal of Arid Environments. 5. Soberón & Nakamura (2009). Niches and
distributional areas: concepts, methods, and assumptions. PNAS, 106(2), 19644-19650. 6. Medina et al. (2016). Environmental, land cover and land use constraints on the distributional patterns of
anurans: Leptodacylus species (Anura, Leptodactylidae) from Dry Chaco. PeerJ, 4, e2605. 7.Camps et al. (2018). Genetic and climatic approaches reveal effects of Pleistocene refugia and climatic
stability in an old giant of the Neotropical Dry Forest. Biological Journal of the Linnean Society, 125(2), 401-420. 8. Peterson et al. (2011). Ecological niches and geographic distributions (MPB-49)
(Vol. 49). Princeton University Press.

3. Methodology
Occurrences were obtained from field trips and the Global
Biodiversity Information Facility (www.GBIF.org) for four species
distributed mainly in Chaco:
● Bulnesia sarmientoi (Bs),
● Calomys callosus (Animalia, Rodentia, cricetidae) (Cc),
● Leptodactylus bufonius (Animalia, Leptodactylidae)(Lb),
● Tolypeutes matacus (Animalia, Xenarthra,) (Tm).
Records were spatially filtered with a 15 km distance in spThin
package in R9. Bioclimatic variables from WorldClim 1.4 at a 2.5
min resolution were used10. Variables mixing temperature and
precipitation were excluded. We determined the accessible
historical area of the species with an ecoregional criteria. A
Principal Component Analysis (PCA) was performed with the
cropped variables. The three first components of the PCA were
used to build niches in environmental space. MVE Niche
models were constructed and plotted using the software
NicheAnalyst v.3.011. Niche volume and overlap were obtained
using the same software.
Figure 1: Records of the species
(Bs in blue, Cc in red, Lb in green
and Tm in green.
9. Aiello‐Lammens et al. (2015). spThin: an R package for spatial thinning of species occurrence records for use
in ecological niche models. Ecography, 38(5), 541-545. 10. Hijmans et al. (2005). WORLDCLIM–a set of global
climate layers (climate grids). International Journal of Climatology, 25, 1965-1978. 11. Qiao et al. (2016). NicheA:
creating virtual species and ecological niches in multivariate environmental scenarios. Ecography, 39(8), 805-813.

4. Results
Bs Cc Lb Tm
Bs 23.63 13.17 21.59 23.03
Cc - 25.23 16.09 18.47
Lb - - 133.79 72.14
Tm - - - 83.77
Table 1: Niche volumes and overlaps in
environmental space. The niche volumes are
shown in the central diagonal (bold) and the
niche overlaps are the numbers above the
diagonal.
Figure 2: Representation of the ecological niches in environmental space
(Bulnesia sarmientoi in blue, Calomys callosus in red, Leptodactylus bufonius
in green and Tolypeutes matacus in black. Grey dots represent the accessible
historical area of the species.

5. Discussion and Conclusion
Our results show two species with broader niches (L. bufonius and T. matacus)
and two with narrower ones (B. sarmientoi and C. callosus). Interestingly, the
species with broader niches reach lower latitudes in geographical space (Fig. 1).
Regarding the niche overlaps, we see that all of them are overlapped. In fact,
there is a zone of the environmental space in which the four species overlap.
In this first analysis of chacoan species, we include a woody plant (B. sarmientoi)
a rodent (C. callosus) an armadillo (T. matacus) and a frog (L. bufonius). We could
model their niches in environmental space and calculate some metrics to
characterize them. We think that this approach could be useful to test different
biogeographical hypothesis or could complement ecological or taxonomic studies
of chacoan species.