Variation in the Distribution of Four Cacti Species Due to Climate Change in Chihuahua, Mexico

Abstract

This study is about four cacti species in the state of Chihuahua, (Coryphantha macromeris, Mammillaria lasiacantha, Echinocereus dasyacanthus and Ferocactus wislizenii). Geographic distribution was inferred with MaxEnt. Projection was estimated under three scenarios simulated from IPCC (A2, B1 and A1B) and four periods (2000, 2020, 2050 and 2080) with 19 climatic variables. MaxEnt projects a species decrease in 2020 under scenario A2, increasing in the following years. In 2080 all species, except E. dasyacanthus, will occupy a larger area than their current one. Scenario B1 projected for 2050 a decrease for all species, and in 2080 all species except E. dasyacanthus will increase their area. With A1B, C. macromeris decreases 27% from 2020 to 2050. E. dasyacanthus increases from 2020 to 2050 and decreases 73% from 2020 to 2080. M. lasiacantha decreases 13% from 2020 to 2080 and F. wislizenii will increase 13% from 2020 to 2080. Some species will remain stable on their areas despite climate changes, and other species may be affected under the conditions of the A1B scenario. It is important to continue with studies which give a broader perspective about the consequences of climate change, thus enabling decision-making about resource management.

Full text

Int. J. Environ. Res. Public Health 2014, 11, 390-402; doi:10.3390/ijerph110100390
International Journal of
Environmental Research and
Public Health
ISSN 1660-4601
www.mdpi.com/journal/ijerph
Article
Variation in the Distribution of Four Cacti Species Due to
Climate Change in Chihuahua, Mexico
Leonor Cortes
1,
*, Irma Domínguez
1
, Toutcha Lebgue
1
, Oscar Viramontes
2
, Alicia Melgoza
1
,
Carmelo Pinedo
1
and Javier Camarillo
1
1
Facultad de Zootecnia y Ecología, Universidad Autónoma de Chihuahua, Periférico R. Almada Km 1,
Chihuahua, Chih. 31000, Mexico; E-Mails: evelina_p7@hotmail.com (I.D.);
tlebgue@uach.mx (T.L.); amelgoza@uach.mx (A.M.); cpinedo@uach.mx (C.P.);
jcamarillo@uach.mx (J.C.)
2
Facultad de Contaduría y Administración, Universidad Autónoma de Chihuahua, Circuito
Universitario #1, Nuevo Campus Universitario, Chihuahua, Chih. 31000, Mexico;
E-Mail: oviramon@uach.mx
* Author to whom correspondence should be addressed; E-Mail: lcortes@uach.mx;
Tel./Fax: +52-614-434-0303.
Received: 6 November 2013; in revised form: 26 November 2013 / Accepted: 27 November 2013 /
Published: 24 December 2013
Abstract: This study is about four cacti species in the state of Chihuahua,
(Coryphantha macromeris, Mammillaria lasiacantha, Echinocereus dasyacanthus and
Ferocactus wislizenii). Geographic distribution was inferred with MaxEnt. Projection was
estimated under three scenarios simulated from IPCC (A2, B1 and A1B) and four periods
(2000, 2020, 2050 and 2080) with 19 climatic variables. MaxEnt projects a species
decrease in 2020 under scenario A2, increasing in the following years. In 2080 all species,
except E. dasyacanthus, will occupy a larger area than their current one. Scenario B1
projected for 2050 a decrease for all species, and in 2080 all species except
E. dasyacanthus will increase their area. With A1B, C. macromeris decreases 27% from
2020 to 2050. E. dasyacanthus increases from 2020 to 2050 and decreases 73% from 2020
to 2080. M. lasiacantha decreases 13% from 2020 to 2080 and F. wislizenii will increase
13% from 2020 to 2080. Some species will remain stable on their areas despite climate
changes, and other species may be affected under the conditions of the A1B scenario. It is
important to continue with studies which give a broader perspective about the
consequences of climate change, thus enabling decision-making about resource management.
OPEN ACCESS

Int. J. Environ. Res. Public Health 2014, 11 391
Keywords: MaxEnt; modelation; cacti; climatic change; Coryphantha macromeris;
Mammillaria lasiacantha; Echinocereus dasyacanthus; Ferocactus wislizenii; distribution
1. Introduction
In the last decades, planet Earth has been warming up and it is clear that human activities have
affected the weather and the balance of the planet’s natural cycles. [1] Weather phenomena depend on
a number of factors that interact in complex ways, in contrast to the traditional notion, which is the set
of variables that impact directly the way the atmosphere restructures itself with a series of interactions
that occur with the sea and continents in different time and spatial frames. The costs of global warming
arise from high temperatures produced by continuous damage to the environment, caused by sudden
events in terms of climatic catastrophes [2]. The inherent problem is that there is considerable
uncertainty associated to these two types of events [3]. Since global warming is a very complex
problem and its signs are sometimes difficult to see, there is without a doubt a high level of uncertainty
among population about the existence of global warming.
Mexico is among the 70 countries with greater Greenhouse Gas Emissions (GGE) per capita,
because it produces 0.96 tonnes of carbon dioxide every year that go into the atmosphere; 30.5% of the
emissions are directly involved in activities of soil usage change and deforestation [4]. In this respect,
animal and vegetal species, as yet endangered because of human activities, will be also endangered
because of Climatic Change (CC).
Due to its geographic location and complex landscape Mexico is one of the countries with greater
species diversity. Besides, many of the species in this country are endemic [5]. In the state of
Chihuahua half of the ecosystems are arid and semi-arid zones. The potential of these zones has to be
evaluated for a proper resource management, since these ecosystems are fragile and have a
slow restoration [6].
The Chihuahua desert is, biologically speaking, one of the richest in the World. It covers an
approximate area of 391,046 sq. mi., and approximately 30% of cacti species grow in this desert [5].
Cacti are important because of their endemism and their wide distribution in the American continent [7].
The cacti family, known collectively as cactus or cacti, is one of the most typical groups of succulents
and most of them have spines [8]. Out of the total that exist in Mexico, about 35% have a risk status,
and the Northwest region of the country houses the higher diversity and endemism, unfortunately this
diversity is threatened due to man’s activities [6]. Cacti may be exploited in different ways, including
as hedges and as cattle food, however their most common usage is as ornamental plants and as part of
the human diet.
Tellez-Valdez and Davila-Aranda say that ecological niche modeling allows for the analysis of
factors associated with different populations of a particular species with different degrees of impact [9].
The information that was analyzed by algorithms enables the projection in the geographical level of the
potential area covered by the species. The results of the spatial studies may provide critical information
about the diversity present on certain geographic areas and they can be used for different purposes,
such as assessing of the current state of plant species conservation or prioritizing conservation areas [10].

Int. J. Environ. Res. Public Health 2014, 11 392
There are general factors that affect species distribution: temperature, water availability and
topography. More particularly they can be described as soil types, evapotranspiration, light quality or
days with temperatures below the freezing point, among others [11]. It is important to know that niche
modeling represents an approximation of the species’ ecological niche in the dimensions in the
environmental crusts used [12].
There are modeling efforts where the MaxEnt program was applied, including those by Carroll who
evaluated and modeled with the relations that exist between weather and vegetation variables,
concluding that MaxEnt has a good performance in contrast with 15 alternative methods in a wide taxa
variety in different regions. The variables measured were temperature and precipitation, provided for
the three simulations of the future climate during two time periods (2011 to 2040 and 2061 to 2090) [13].
Colombo and Joly [14] worked on a zone in the Atlantic Forest. The data about species distribution
were taken from Oliveira and Scudeller and Martins [15,16], who compared more than 100 lists of tree
species, and 38 were selected for which there were not enough data about their current distribution.
The selected variables were slope, diurnal temperature range, average annual precipitation and vapor
pressure (annual averages 1960–1990). Regarding to future scenario projection, CC crusts were used
for the next 50 years (IPCC 2001) and the same data for topographical issues, taking into account the
little possibility of topographical changes in the next 50 years. It was concluded that all the MaxEnt
projection models on the current area covered by the 38 species, present a high significance level
(binomial test: two ratios, p < 0.05 for all species). Based on the above, the objective of the research
reported herein was to evaluate the impact of the climate change on the geographical distribution of
four cacti species found in the state of Chihuahua.
2. Materials and Methods
2.1. Description of the Area of Study
The distribution areas for the selected species are found in the state of Chihuahua. The state is
formed by three major regions: the Sierra, Plateau and Desert, which occur from west to east in the
form of big stripes. This results in the greatly contrasting weather and geographical conditions that
give the State its better known images, its great deserts, mountains, canyons and forests [5]. The
Chihuahua desert is, biologically speaking, one of the richest in the World. This territory is mostly flat,
though it has low sierras across, most of them north to south [17]. The desert weather in this region is
very dry, yearly rainfall is less than 0.54 in. (350 mm); average temperatures go from 55.4 °F (13 °C)
in January to 96.8 °F (36 °C) in June, reaching 122 °F (50 °C) in the hottest days of the year, with
frosts in winter. Snow also appears in this region, though less frequently.
2.2. Selected Species
Four cacti species with distribution on Chihuahua Desert were selected. These species were selected
from collected previously registers, they are: Coryphantha macromeris, Mammillaria lasiacantha,
Echinocereus dasyacanthus and Ferocactus wislizenii [8].

Int. J. Environ. Res. Public Health 2014, 11 393
2.3. Modeling and Simulation
Taking into account the literature research of methodologies used already, the process to be
followed for the species’ distribution modeling and simulation is described in the following
paragraphs. It is necessary to collect bio-climatic crusts (these crusts were downloaded from
WorldClim, with a resolution of 1 Km., for four periods of time 2000, 2020, 2050 and 2080, under
three different scenarios A2, B1 y A1B [18]) and georefencered data. Georeferenced data are saved on
spreadsheets such as MS Excel files in UTM format. The next step is to convert or save these data in
formats that can be read with modeling niche programs. This task is made through the Geographic
Information Systems (GIS) such as ArcMap with the option “Conversion Tools”, which allows the
crusts to be saved in ASCII format so they can be read by MaxEnt [19]. Finally the MaxEnt program is
run, taking geolocalities and climatic crusts data, it generates an area map of species’ potential
location, and these files can be seen in GIS (ArcMap).
3. Results and Discussion
The data presented in Table 1 show the results from MaxEnt modeling. It is observed how the four
cacti species will be located on scenario A2 (Figures 1, 2, 3 and 4), with a decrease in relation to the
potential area by the year 2020. This decrease can be taken as non-significant for the
Coryphantha macromeris and Mammillaria lasiacantha species because in the years 2050 and 2080
they have a major increase in their potential area that in the case of Coryphantha macromeris is larger
than it is currently.
Table 1. Current and future Potential Areas of the species in km
2
.
Scenario A2 B1 A1B A2 B1 A1B
Coryphantha macromeris Mammillaria lasiacantha
2000 121,643 ND ND 177,557 ND ND
2020 101,611 126,127 107,183 148,620 175,365 180,743
2050 129,173 100,073 78,228 173,681 170,489 123,352
2080 135,566 112,298 138,631 179,172 174,472 157,051
Echinocereus dasyacanthus Ferocactus wislizenii
2000 134,720 ND ND 85,531 ND ND
2020 131,951 147,397 128,736 86,285 79,520 67,551
2050 130,401 137,911 130,518 86,883 65,355 80,185
2080 127,423 136,181 33,789 90,957 75,627 78,144
Note: ND: Data non available for these scenarios.

Int. J. Environ. Res. Public Health 2014, 11 394
Figure 1. Potential distribution models (MaxEnt) for Coryphantha macromeris considering
a liberal A2 temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2000
121,643 km
2
Year 2020
101,611 km
2
Year 2050
129,173 km
2
Year 2080
135,566 km
2
Figure 2. Potential distribution models (MaxEnt) for Mamillaria lasiacantha considering a
liberal A2 temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2000
177,555 km
2
Year 2020
148,620 km
2
Year 2050
173,681 km
2
Year 2080
179,172 km
2

Int. J. Environ. Res. Public Health 2014, 11 395
Figure 3. Potential distribution models (MaxEnt) for Echinocereus dasyacanthus
considering a liberal A2 temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2000
134,720 km
2
Year 2020
131,951 km
2
Year 2050
130,401 km
2
Year 2080
127,423 km
2
Figure 4. Potential distribution models (MaxEnt) for Ferocactus wislizenii considering
a liberal A2 temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2000
85,531 km
2
Year 2020
86,284 km
2
Year 2050
86,883 km
2
Year 2080
90,957 km
2
Both species, Echinocereus dasyacanthus and Ferocactus wislizenii, present a decrease in their
areas in the year 2050, unlike Echinocereus dasyacanthus, and the Ferocactus wislizenii species will
increase its area in 2080, to larger than its current area.
The study showed about the variable contribution percentage of the variables that temperature has a
greater influence in species distribution. The variables were: 10 (Average temperature of the hotter
quadrimester) more significant for Coryphantha macromeris; variable 1 (Average annual temperature)

Int. J. Environ. Res. Public Health 2014, 11 396
for Mammillaria lasiacantha; variable 8 (Average temperature of the rainiest quadrimester) for
Echinocereus dasyacanthus and variable 7 (Annual tolerance range) for Ferocactus wislizenii. Taking
into account that climate change causes an increase in the planet’s temperatures and being the
temperature variables those with a greater influence on these cacti species, it is reasonable to say that
the tolerance range for these species is wide since MaxEnt did not indicate a noticeable decrease about
the species’ potential distribution area.
The results estimated for scenario B1 are similar to scenario A2 (Figures 5, 6, 7 and 8); all species
except Echinocereus dasyacanthus show a decrease from the year 2020 to the year 2050 and later in
the year 2080 an increase in their distribution area. In the case of Echinocereus dasyacanthus the
decrease in its potential distribution area is constant in the three time periods.
Figure 5. Potential distribution models (MaxEnt) for Coryphantha macromeris considering
a liberal B2 temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2020
126,127 km
2
Year 2050
100,073 km
2
Year 2080
112,298 km
2
Figure 6. Potential distribution models (MaxEnt) for Mamillaria lasiacantha considering a
liberal B1 temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2020
175,365 km
2
Year 2050
170,489 km
2
Year 2080
174,472 km
2
Figure 7. Potential distribution models (MaxEnt) for Echinocereus dasyacanthus
considering a liberal B1 temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2020
147,397 km
2
Year 2050
137,911 km
2
Year 2080
136,181 km
2

Int. J. Environ. Res. Public Health 2014, 11 397
Figure 8. Potential distribution models (MaxEnt) for Ferocactus wislizenii considering
a liberal B1 temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2020
79,520 km
2
Year 2050
65,355 km
2
Year 2080
75,627 km
2
In spite of scenario B1 being about a reduction in the use of materials, a cleaner technology and
a more efficient resource usage including global solutions to environmental sustainability, we can
observe a difference about the species’ total distribution area for both scenarios. An important
observation concerning the B1 scenario is that in the four cases the distribution area is smaller from
year 2080 to 2020, where Coryphantha macromeris will decrease in 10.96%, Mammillaria lasiacantha
in 0.5%, Echinocereus dasyacanthus in 7.6% and Ferocactus wislizenii in 4.89%.
The MaxEnt model shows an overview of the species spatial conditions, it is an approximation to
reality that serves as starting point decision making in species conservation. Even though in the results
we can see a resistance of cacti to CC, it is important to take into account other important factors such
as soil usage or species trafficking that place them in risk.
The most important results were projected by MaxEnt for the scenario A1B (Figures 9, 10, 11 and 12).
For Coryphantha macromeris it shows a decrease of 27% from the year 2020 to 2050, but the area will
increase in 2080 to 86.14 sq. mi. which represents an increase of 22% from the projection for 2020.
Mammillaria lasiacantha decreases from 2020 to 2050 and increases in 2080, being left with
a distribution area 13% smaller than in 2020. Echinocereus dasyacanthus presented a decrease in the
three time periods in scenario A2 as well as in scenario B1, this shows it as the only constant species in
both scenarios, however for scenario A1B it will have a slight increase of 1.38% by 2050 and similar
to the previous scenarios it will decrease, in this case 73% smaller than in 2020. Finally
Ferocactus wislizenii increases in 15% from 2020 to 2050 and for 2080 it decreases 2.5%.
Figure 9. Potential distribution models (MaxEnt) for Coryphantha macromeris considering
a liberal A1B temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2020
107,183 km
2
Year 2050
78,228 km
2
Year 2080
138,631 km
2

Int. J. Environ. Res. Public Health 2014, 11 398
Figure 10. Potential distribution models (MaxEnt) for Mamillaria lasiacantha considering
a liberal A1B temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2020
180,743 km
2
Year 2050
123,352 km
2
Year 2080
157,051 km
2
Figure 11. Potential distribution models (MaxEnt) for Echinocereus dasyacanthus
considering a liberal A1B temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2020
128,736 km
2
Year 2050
130,518 km
2
Year 2080
33,789 km
2
Figure 12. Potential distribution models (MaxEnt) for Ferocactus wislizenii considering a
liberal A1B temperature climatic scenario (current, 2020, 2050 and 2080).
Year 2020
67,551 km
2
Year 2050
78,228 km
2
Year 2080
78,144 km
2
The description given by IPCC for the A1B scenario is made as part of the A1 scenario where it is
supposed that economic growth is fast, with an accelerated population growth that peaks in the
twenty-first century and decreases afterwards; a world where there is a quick introduction of new and
efficient technologies, especially in A1B which would have a balance of all energy sources.
The following Figures 13–16 show the behavior of the four species on the IPCC different scenarios
and time periods.

Int. J. Environ. Res. Public Health 2014, 11 399
Figure 13. Coryphantha macromeris dispersal area on the different scenarios (A2, B1
and A1B) in km
2
.
Figure 14. Mammillaria lasiacantha dispersal area on the different scenarios
(A2, B1 and A1B) in km
2
.
Figure 15. Echinocereus dasyacanthus dispersal area on the different scenarios (A2, B1
and A1B) in km
2
.

Int. J. Environ. Res. Public Health 2014, 11 400
Figure 16. Ferocactus wislizenii dispersal area on the different scenarios (A2, B1 and A1B) in km
2
.
4. Conclusions
The results show stability regarding the present and future distribution of cacti species under
scenarios A2 and B1, and the most significant changes were for scenario A1B. In the first scenario A2,
the species Coryphantha macromeris decreases 16.46% in the first period of time from 2000 to 2020,
but for the following periods it increases 25.04% from 2020 to 2080. In scenario B1 it decreases
20.65% from the year 2020 to 2050, ending in 2080 with 10.88% more. Finally this species in the
scenario A1B presents a decrease of 27.01% in its distribution area from 2020 to 2050 and it has
an increase of 43.57% by 2080. The species Mammillaria lasiacantha presents a decrease of 16.29%
in the period 2000–2020 for the case of the first scenario A2; however both in the period of 2020–2050
and 2050–2080 it presents an area increase of 14.42% and 3.06% respectively. In the case of scenario
B1 the species has a decrease for the first period but for the following years it increases, projecting
a loss of only 0.5% from 2020 to 2080. In the third scenario the results of the distribution area present
like to the previous one a decrease in the first period from 2020 to 2050 of 31.75% and it repeats the
same pattern increasing 21.45% in the second period from 2050 to 2080. The third species
Echinocereus dasyacanthus presents in the first scenario A1, a decrease of 5.41% from 2000 to 2080.
The behavior of this species in the scenario B1 is the same as in the previous scenario with a decrease
from 2020 to 2080, being in this case of 7.60%. In the following scenario A1B this species shows
an increase in its area of 1.36% in the first period 2020–2050, but the decrease in the second period
2050-2080 is significant, with 74.11% of its potential distribution area. Finally, the species
Ferocactus wislizenii presents an increase of 5.96% from 2000 to 2080 in the first scenario A2.
The scenario B1 presents a decrease of 17.81% in the first period 2020–2050 and it increases 13.58% in
the final period 2050–2080. The scenario A2B for this species starts with an increase of 17.81% in the
first period 2020–2050 and it decreases 2.54% in the final period 2050–2080.
Although cacti distribution was not affected significantly by climate change, we should continue
research to know the state of other species in Mexico. It is also important to take into account other
factors such as changes in soil usage that affect the species distribution directly, decreasing
their distribution.

Int. J. Environ. Res. Public Health 2014, 11 401
Since damage can be done silently, slowly and many times continuously; at first sight the alteration
is not evident. MaxEnt allows for the diagnosis of the present and/or future to envision possible
solutions to preserve these species. It is necessary to analyze the effects that climate change may have
on the different species distribution areas.
Conflicts of Interest
The authors declare no conflict of interest.
References
1. Magaña, V. El cambio Climático Global: Comprender el Problema. In Cambio Climático: Una
Visión Desde México; Martinez, J., Bremauntz, A.F., Eds.; Secretaria de Medio Ambiente
y Recursos Naturales, Instituto Nacional de Ecología: Coyoacán, Mexico, 2004
2. Baranzini, A.; Chesney, M.; Morisset, J. The impact of possible climate catastrophes on global
warming policy. Ener. Pol. 2003, 31, 691–701.
3. Joireman, J.; Barnes, H.; Duell, B. Effect of outdoor temperature, heat primes and anchoring on
belief in global warming. J. Environ. Psychol. 2010, 30, 358–367.
4. Arriaga, L.; Gómez, L. Posibles Efectos del Cambio Climático en Algunos Componentes de la
Biodiversidad de México. In Cambio Climático: Una Visión Desde México; Martinez, J.,
Bremauntz, A.F., Eds.; Secretaria de Medio Ambiente y Recursos Naturales, Instituto Nacional de
Ecología: Coyoacán, Mexico, 2004.
5. WWF México. Available online: http://www.wwf.org.mx/wwfmex/prog_desierto.php (accessed
on 7 September 2012).
6. Flores, M.; Castro, P. Las cactáceas de la región semidesértica del estado de Chihuahua México.
Tesina licenciatura, Universidad Autónoma de Chihuahua, Chihuahua, Chih, México, 2010.
7. Lebgue, T.; Viramontes, O.; Soto, R.; Quiñonez, M.; Balderrama, S.; Aviña, E. Cactáceas
endémicas y raras del estado de chihuahua, México. Tecnociencia Chihuahua 2011, 5, 27–33.
8. Cactáceas de Chihuahua Tesoro estatal en peligro de extinción. Lebgue, T., Quintana, G. Eds.;
Fondo Mixto-Conacyt, Gobierno del Estado de Chihuahua: Instituto Chihuahuense de la Cultura,
Chihuahua, México, 2010.
9. Téllez-Valdés, O.; Dávila-Aranda, P. Protected areas and climate change: A case study of the
cacti in the Tehuacán-Cuicatlán Biosphere Reserve, México. Conserv. Biol. 2002, 17, 846–853.
10. Manual de Capacitación en Análisis Espacial de Diversidad y Distribución de Plantas Bioversity
International; Scheldeman, X., Zonneveld, M., Eds.; Bioversity international: Roma, Italia, 2011.
11. Martínez, N. Apuntes sobre modelación de nichos ecológicos. In Laboratorio de Evolución
Molecular y Experimental; Instituto de Ecología de la, Universidad Nacional Autónoma de
México, 2010.
12. Rodríguez, A. Aplicación de los modelos de distribución geográfica para la conservación y
reintroducción en el hábitat natural de Lychnophora ericoide. Tesis Licenciatura, Universidad
Internacional de Andalucía, España, México, 2011.

Int. J. Environ. Res. Public Health 2014, 11 402
13. Carroll, C. Role of climatic niche models in focal-species-based conservation planning: Assessing
potential effects of climate change on Northern Spotted Owl in the Pacific Northwest, E.U.A. Biol.
Conserv. 2010, 143, 1432–1437.
14. Colombo, F.; Joly, C. Brazilian Atlantic Forest lato sensu: The most ancient Brazilian forest, and
a biodiversity hotspot, is highly threatened by climate change. Braz. J. Biol. 2010, 3, 697–708.
15. Oliveira, R. Análise da variação florístico-estrutural das florestas atlánticas. Tesis doctoral,
Biology Institute State University of Campinas, São Paulo, Brasil, 2001.
16. Scudeller, V.; Martins, F.; FITOGEO—um banco de dados aplicado à Fitogeografia.
Acta Amazon. 2003, 33, 9–21.
17. Instituto de la candelilla. Available online: http://www.candelilla.org (accessed on 15 February 2013).
18. Worldclim. Available online: http://www.worldclim.org/ (accessed on 15 January 2013).
19. Maxent software. Available online: http://www.cs.princeton.edu/~schapire/maxent/ (accessed on 15
January 2013).
© 2013 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article
distributed under the terms and conditions of the Creative Commons Attribution license
(http://creativecommons.org/licenses/by/3.0/).