Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 February 2022 | 14(2): 20597–20605
ISSN 0974-7907
(Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.6999.14.2.20597-20605
#6999 | Received 16
December 2020 | Final received 19 November 2021 | Finally accepted 08 January
2022
Ecological niche modeling for reintroduction and conservation of Aristolochia cathcartii
Hook.f. & Thomson (Aristolochiaceae),
a threatened endemic plant in Assam, India
Bhaskar Sarma
1 & Bhaben
Tanti 2
1 Department of Botany, Dhemaji College, Dhemaji, Assam
787057, India.
2 Department of Botany, Gauhati University, Guwahati, Assam 781014, India.
1 bhaskarsarma252@gmail.com (corresponding
author), 2 btanti@gauhati.ac.in
Editor: G. Fauzul
Azim Zainal Abidin, Ecological Spatial Data
Infrastructures (ESDI), Selangor, Malaysia. Date
of publication: 26 February 2022 (online & print)
Citation: Sarma,
B. & B. Tanti (2022). Ecological niche modeling for reintroduction and conservation of Aristolochia cathcartii
Hook.f. & Thomson (Aristolochiaceae),
a threatened endemic plant in Assam, India. Journal of Threatened Taxa 14(2): 20597–20605. https://doi.org/10.11609/jott.6999.14.2.20597-20605
Copyright: © Sarma
& Tanti 2022. Creative Commons Attribution
4.0 International License. JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: None.
Competing interests: The authors
declare no competing interests.
Author details: Bhaskar
Sarma completed his PhD in Cytology and
Genetics (2015) from Gauhati University. Presently he
is serving as Assistant Professor at Dhemaji College
(Dibrugarh University), Assam, India. His research interest in plant tissue
culture, genetics, molecular marker and ecological modeling. He has more than 24 publications in peer-
reviewed journals including conference papers and book chapters. He is the
author of two books written for UG and PG students. He has three years of teaching experience. Bhaben Tanti is a Professor and Head,
Department of Botany, Gauhati University, India. His
area of research is molecular stress physiology of the traditional crops of the
region, climate change and conservation biology. In his 22 years of academic and research
careers, published 108 research papers, eight book chapters.
Author contributions: Both the authors contributed
equally.
Acknowledgements: We express gratitude to Late Sailendra Prasad Borah, Professor of Gauhati
University for explaining the significance of the plant. We are also grateful
to principal of Dhemaji College for logistics and
support.
Abstract: Aristolochia
cathcartii Hook.f.
& Thomson is a medicinal plant species native to Assam (India). Karbi people have traditionally used the plant to treat a
variety of ailments. The population stock of this species has been rapidly
depleting in its natural habitats due to over-utilization, habitat fragmentation,
and other anthropogenic activities. Extensive field surveys were carried out to
investigate the population status of A. cathcartii
in various forest areas of Assam’s Karbi Anglong district. In 20 km of transects, a total of 36
quadrats were observed. A. cathcartii density,
frequency of occurrence, and abundance were recorded to be 0.65, 17.8, and
3.81, respectively. Ecological niche modelling was used to identify suitable
habitat for the reintroduction and conservation of this plant in Assam in order
to prevent its extinction in the future. The maximum entropy distribution
modelling algorithm was used to identify suitable areas and habitat for the
species’ reintroduction and conservation. Primary data on the occurrence of A.
cathcartii was gathered from the natural habitat
of Karbi Anglong district,
Assam, for modelling. The model identified various forest areas in northeastern India that have suitable climatic conditions
for plant reinforcement.
Keywords: Abundance, DIVA GIS, forest,
habitat, medicinal plant, MaxEnt, NDVI, occurrence,
population, survey.
INTRODUCTION
Aristolochia cathcartii,
belonging to
the family Aristolochiaceae, is a large climber.
Traditionally, A. cathcartii has been used by
the Karbi community of Assam to treat cholera,
stomach pain, fever, and poisonous bites (Sarma et
al. 2015, 2017). Overexploitation, climate change, habitat fragmentation and
loss, and rapid urbanization cause gradual depletion of this medicinally
important plant from its natural habitat. Species reinforcement is the best
technique for the restoration of depleted species populations and degraded habitats
and ecosystems (Leaper et al. 2006; Martinez-Meyer et al. 2006; Kuzovkina & Volk 2009; Ren et al. 2009;
Rodríguez-Salinas et al. 2010; Polak & Saltz 2011). Ecological niche modeling
helps in identifying sites of species occurrence and also helps to spot other
suitable habitats for reintroduction. Ecological niche modeling
(ENM) is a tool in geographic information system (GIS) software that uses
occurrence data of a species across landscapes and correlates them with digital
raster GIS coverage to develop a model of environmental conditions that meet
ecological requirements and identify the suitable environment of the species (Guisan & Zimmermann 2000; Elith
et al. 2006; Kozak et al. 2008). ENM facilitates interpolation as well as the
extrapolation of species distributions in geographic space across different
periods and it helps to prepare habitat distributional maps by spotting areas
suitable for reintroduction of threatened species (Irfan-Ullah et al. 2006;
Kumar et al. 2009; Ray et al. 2011). For conservation strategy, it is essential
to identify areas which bear appropriate environmental conditions suitable for
the species persistence. Therefore, the present work was undertaken to study
the population distribution status of A. cathcartii
and to model the habitat distributional map in its native range.
MATERIALS
AND METHODS
Plant material
A. cathcartii Hook.f.
& Thomson belonging to the family Aristolochiaceae
is a large climber, with corky furrowed bark; young branchlets, and petioles
villous. Leaves 5.5–10 by 3.5–6.5 inch, broadly ovate, sometimes
ovate-lanceolate, acute or acuminate, entire; base cordate, sometimes slightly
lobed along the sinus, 3-nerved or pedately 5-nerved, thinly coriaceous,
pubescent along the midrib and larger nerves especially towards the base,
otherwise glabrous above, clothed, often felted with
long silky hairs beneath; lateral nerves excluding the basal 5–6 on either
side; petioles 1.5–4 inch long, sometimes twining. Flowers usually in short
brown villous cymes from axils of existing or fallen
leaves; pedicels 0.6–1 inch long, villous. Perianth yellowish-white, with
purple veins clothed with spreading hairs outside, 2.5–3 inch long along the
bends, sac bent near the short neck, mouth square, densely purple papillose
along the edge and the recurved lip. Capsule about 6.5 by 1.7 inch,
linear-oblong, bluntly apiculate, softly tomentose,
6-ribbed, grooved between the furrows; seeds about 0.4 inches long, not winged,
obovate, acute at the base, margins slightly incurved on the inner face,
dorsally more or less truncate and margined (Kanjilal
& Bor 1940). This plant is native to Assam,
Bangladesh, China south-central, eastern Himalaya, Myanmar, Nepal, and Tibet
(Plants of the world online, Royal Botanic Gardens, Kew).
Survey of the plant species and
its population status
A frequent field visit was
carried out to record the population status of A. cathcartii
in Dhansiri, Kalioni, Nambar, Lahorijan, and Matipung Reserve Forest of KarbiAnglong
district, Assam (India). The forest of KarbiAnglong
is moist semievergreen and moist mixed deciduous
type. The total population of A. cathcartii
was calculated through a direct count method for all individuals. The grid size
was taken 250 Ï 250 m and individuals were categorized as seedlings (<1 m
height), saplings (>1 m height), and matured individuals (≥1.37 m height).
The density, frequency, and abundance of the plant species were calculated with
the following formulae:
Total number of individuals of a species in all quadrats
Density = ––––––––––––––––––––––––––––––––––––––––––––––––
Total number of
quadrats studied
Number of quadrats in which the
species occured x 100
Frequency (%) =
–––––––––––––––––––––––––––––––––––––––––––
Total number of quadrats studied
Total number of individuals of a species in
all quadrats
Abundance =
––––––––––––––––––––––––––––––––––––––––––––––
Total number of quadrats in which the species occured
Ecological niche modeling
Primary locations of the species
were collected through field surveys. To record the coordinates of occurrence
points of the species global positioning system (GPS) was used to an accuracy
of 10–40 m. Then the coordinates were translated to decimal degrees to be used
in habitat distribution modeling software (Adhikari
& Barik 2012). For ecological modeling different
types of environmental datasets are available in public domain websites. In our
study, the index of normalized difference vegetation (NDVI) was used to model
the distributional pattern of A. cathcartii in
northeastern India (Table 2). The NDVI was obtained
from Global Land Cover Facility (GLCF, University of Maryland). All the
analyses were conducted at the spatial resolution of 250 m.
Validation of model robustness
For habitat modeling
of A. cathcartii, the NDVI and the maximum
entropy modeling (MEM) was used to develop the model
(Adhikari & Barik 2012). MaxEnt uses
presence-only data to predict the geographic location of a species based onthe principle of maximum entropy (Phillips et al. 2006; Elith et al. 2011). For the calibration, we used the
presence and background data locations where 75% of the records were used for
training the model and 25% for the test (Adhikari & Barik 2012). We conducted
20 replicated model runs and the replicated run type was cross-validation with
a 10-percentile threshold rule of training presence to validate the model
robustness (Adhikari & Barik 2012; Sarma et al.
2018). Since the program is already calibrated, therefore, other parameters
were set as default (Adhikari & Barik 2012). Replicated runs generated
average, maximum, minimum, median, and standard deviation. Quality of the model
was assessed based on area under curve (AUC) value and the model was classified
according to Thuiller et al. (2007) as very good
(0.95 < AUC < 1.0), good (0.9 < AUC < 0.95), fair (0.8 < AUC
< 0.9), and poor (AUC < 0.8).
Population status vis-à-vis model
thresholds
Extensive field visits were
executed to investigate the robustness and relevance of the model in predicting
the population status of A. cathcartii in each
occurrence area as predicted under various model thresholds. The total
population of the species was calculated by direct count of all individuals of
seedlings, saplings, and mature individuals in each 250 × 250 m grid of
occurrence within the predicted localities. The population data of A. cathcartii in each occurrence area was then correlated
with the corresponding threshold level of the distribution models to check
whether regions fell under higher threshold level sustain higher populations
thus favoring improved habitat conditions for species
establishment and vice versa.
Analysis of habitat status and
recognition of areas for reintroduction
We analyzed
the habitat type in the occurrence areas of the species as well as the
predicted potential areas through repeated field surveys. To identify the
actual habitat of the species, we imported the ASC (Action Script
Communication) file of the model output to Diva GIS ver. 7.3, and then we
exported the Grid file as KMZ (Keyhole Markup
Language Zipped) format for display in Google Earth (Adhikari & Barik 2012;
Sarma et al. 2018; Baruah et al. 2016; Deka et al.
2018). Then we superimposed the exported KMZ files on Google Earth Pro
satellite imageries to determine the actual habitat condition of the areas of
occurrence and areas that prevailing the same habitat for the reintroduction of
the species (Thuiller et al. 2007; Adhikari &
Barik 2012; Baruah et al. 2016; Deka et al. 2017; Deka et al. 2018; Sarma et al. 2018).
RESULTS
Population distribution status of
Aristolochia cathcartii
The
population distribution status of a species indicates its importance in
conservation. Species with a limited range of distribution needs to be
protected more than a wide range of distribution. Considerable field surveys
were conducted to explore the population status of A. cathcartii
in each occurrence area. A total of 36 numbers of quadrats were observed along
20 km of transects. The density, frequency of occurrence, and abundance of A.
cathcartii are shown in Table 1. The observation
tabulated below depicted the mean density of A. cathcartii
as 0.65, frequency of occurrence 17.77, and abundance concerning other
associated species as 3.81.
Calibration of models
The model calibration test for A.
cathcartii yielded satisfactory results (AUC
test= 0.96 ± 0.002).
Response curves
The response curves (Figure 1)
reflect the dependence of predicted suitability both on the selected variable
and on dependencies induced by correlations between the selected variable and
other variables. The curves show the mean response of the 20 replicate Maxent
runs (red) and the mean +/- one standard deviation (blue, two shades for
categorical variables).
Analysis of variable
contributions
The table 2 gives estimates of
relative contributions of the environmental variables to the Maxent model.
Figure 2 shows the results of the jackknife test of
variable importance. The environmental variable with the highest gain, when
used in isolation, is eu5_1_eur (May), which therefore appears to have the most
useful information by itself. The environmental variable that decreases the
gain the most when it is omitted is eu4_1_eur (April), which therefore appears
to have the most information that isn’t present in the other variables. Values
shown are averages over replicate runs.
Population status vis-à-vis model
thresholds
A total of 589 number of
individuals were recorded within the area of occurrence spread over 25 250 x
250 m grids. Of these 345 numbers of individuals were adults, 187 numbers of
individuals were sapling and 57 numbers of individuals were seedlings (Table
3). The analysis of population structure at each locality revealed that the
highest number of adult individuals were in Dhansiri
(78), Daldali (75), Lahorijan
(67), Matipung (65), and Nambar
(60). The population size including all adults, saplings, and seedlings was
larger in the areas under the high suitability threshold category followed by amedium to low category (Table 3). Areas predicted as a
medium to high suitable classes represent 84% of the total population followed
by a low threshold. This establishes the strong correlation between population
size and level of the model threshold. Of the 25 localities, nine localities
fell under high class, 11 localities under medium, and five localities fell
under low habitat suitability class.
Saplings were poorly represented
in most of the areas. The number of seedlings was also very poor even absent in
some areas. The number of seedlings was highest in Daldali
with 13 seedlings, followed by Matipung with 12
seedlings, Nambar, and Lahorijan
with 11 seedlings each, and Dhansiri with 10
seedlings. Similarly, the number of saplings also highest in Daldali with 48 individuals, followed by Nambar with 40 individuals, Lahorijan
with 35 individuals, and Dhansiri and Matipung with 32 individuals each. The population structure
based on a seedling, sapling, and adult individuals revealed that good
regeneration takes place in the moist semi-evergreen habitat followed by mixed
deciduous habitat whereas in other habitats it depicted poor regeneration
(Table 3).
Habitat status assessment and
identification of areas for reintroduction
Field surveys for assessing the
habitat type of A. cathcartii in the predicted
potential areas revealed that the species occurred in moist semi-evergreen and
mixed deciduous forests. Superimposition of the predicted potential habitat
distributional map of the species on Google Earth Pro, satellite imageries
showed that the areas with high habitat suitability for the species were moist
semi-evergreen and evergreen forests. The areas with medium habitat suitability
were mixed deciduous forests and grasslands. The areas with low habitat
suitability were degraded open forests and homestead gardens (Table 4).
The superimposition of predicted
potential habitat distribution map on Google Earth Pro imageries identified
different forest areas of northeastern India, viz., KarbiAnglong (Rangapahar, Bokajan) district of Assam, foothills of Assam-Nagaland
border (Mokokchung, Wokha,
Kohima), Meghalaya (West Khasi Hills, Ri Bhoi),
Arunachal Pradesh (East Siang, Papumpare) (Image 1).
These areas could be used as in situ conservation and reintroduction of A. cathcartii in the wild.
DISCUSSION
A. cathcartii, is best known among the Karbi community of Assam for its high medicinal value.
Locally this plant is called ChongaLota. Due to
overexploitation of this plant by the local community, and other natural, as
well as anthropogenic activities, the population stock of this plant, has been
exhausting very fast from its natural habitat. In primary field surveys in different
forest areas of KarbiAnlong district, we found the
mean density 0.65, frequency 17.77, and abundance 3.81 of A. cathcartii concerning other associated species. To save
this plant species from extinction from its near future, we conducted ENM to improve
the conservation status of this plant. In our present study, ENM gave a good
result in its native range. NDVI parameters used in the modeling
algorithm offered a reasonable explanation in the determination of the habitat
suitability of the species. In determining the boundaries of the potential
habitat of species, NDVI acts as powerful and informative alternate variables,
which represent the complex formulations of the underlying environmental
factors (Baruah et al. 2016; Deka et al. 2017; Sarma
et al. 2018; Baruah et al. 2019). Overall, the results of actual habitat
assessment through Google Earth superimposition and field surveys were
identical. The ENM in the present study showed a good overall result (based on
Area Under Curve (AUC) value and threshold test) in its native range. The high
AUC value, i.e., 0.96 ± 0.002 indicates the good performance of the model.
Habitat status analysis through primary field surveys and secondary surveys
using Google Earth Pro satellite imageries established that the predicted
potential areas of the species fell under all suitability threshold levels,
i.e., low to high suitability. Within 25 250 x 250 m grids, 589 individuals
were counted, of which 345 were adults, 187 saplings, and 57 seedlings. The
number of saplings and seedlings were very poor in most of the occurrence areas
of the species. Areas identified as medium to high suitable classes represent
84% of the total population and it establishes a strong correlation between the
population size and the model thresholds. In the present study, evergreen,
moist semievergreen, and mixed deciduous forests
offer potential habitats at higher levels of probability. Hence, for in situ
conservation and reintroduction of A. cathcartii,
such forest areas could serve as suitable habitats. The present study
demonstrates that habitat distribution modeling
serves as an important tool in identifying the potential habitats for the
reintroduction of threatened species. The areas identified in the present study
for reintroduction would help in the improvement of the conservation status of
species population of A. cathcartii.
Therefore, the results would be quite helpful in the management of this species
in its natural habitat and conservation of overall biological diversity in the
region.
CONCLUSIONS
We present an ecological niche
model of Aristolochia cathcartii
Hook.f. & Thomson, a potential medicinal
plant found in some forest pockets of Assam’s KarbiAnlong
district. We were able to create a distributional map of A. cathcartii using our modelling approach. The areas
identified in this study for reintroduction would aid in improving the
conservation status of the A. cathcartii
species population. As a result, the findings would be extremely useful in the
management of this species in its natural habitat as well as the conservation
of the region’s overall biological diversity.
Table 1. Population status of A.
cathcartii.
Grid no. |
No. of adult plants within 250
m2 grid |
No. of saplings within 250 m2
grid |
No. of seedlings within 250 m2 grid |
Total no. of quadrats of
occurrence of A. cathcartii within 250 m2
grid |
Density within 250 m2
grid |
Frequency within 250 m2
grid |
Abundance within 250 m2 grid |
1 |
15 |
4 |
0 |
5 |
0.53 |
13.9 |
3.8 |
2 |
17 |
7 |
5 |
8 |
0.81 |
22.2 |
3.6 |
3 |
17 |
6 |
2 |
6 |
0.69 |
16.7 |
4.2 |
4 |
13 |
7 |
3 |
6 |
0.64 |
16.7 |
3.8 |
5 |
16 |
8 |
0 |
4 |
0.67 |
11.1 |
6 |
6 |
10 |
9 |
2 |
7 |
0.58 |
19.4 |
3 |
7 |
14 |
9 |
6 |
9 |
0.81 |
25 |
3.2 |
8 |
18 |
11 |
5 |
8 |
0.94 |
22.2 |
4.3 |
9 |
16 |
10 |
0 |
7 |
0.72 |
19.4 |
3.7 |
10 |
17 |
9 |
0 |
7 |
0.72 |
19.4 |
3.7 |
11 |
12 |
10 |
6 |
9 |
0.78 |
25 |
3.1 |
12 |
10 |
9 |
0 |
6 |
0.53 |
16.7 |
3.2 |
13 |
11 |
5 |
0 |
5 |
0.44 |
13.9 |
3.2 |
14 |
11 |
7 |
3 |
8 |
0.58 |
22.2 |
2.6 |
15 |
16 |
9 |
2 |
6 |
0.75 |
16.7 |
4.5 |
16 |
13 |
4 |
0 |
7 |
0.47 |
19.4 |
2.4 |
17 |
15 |
9 |
4 |
6 |
0.78 |
16.7 |
4.7 |
18 |
13 |
5 |
0 |
6 |
0.5 |
16.7 |
3 |
19 |
15 |
10 |
5 |
8 |
0.83 |
22.2 |
3.8 |
20 |
11 |
7 |
2 |
7 |
0.56 |
19.4 |
2.9 |
21 |
13 |
6 |
4 |
6 |
0.64 |
16.7 |
3.8 |
22 |
12 |
6 |
3 |
4 |
0.58 |
11.1 |
5.3 |
23 |
11 |
7 |
2 |
6 |
0.56 |
16.7 |
3.3 |
24 |
14 |
8 |
2 |
4 |
0.67 |
11.1 |
6 |
25 |
15 |
5 |
1 |
5 |
0.58 |
13.9 |
4.2 |
Table 2. List of NDVI and
variable contribution used in the model.
Variable |
Description of the variable |
Percent contribution |
Permutation importance |
eu5 |
NDVI May |
38.9 |
45.5 |
eu4 |
NDVI Apr |
20.9 |
15 |
eu8 |
NDVI Aug |
11.6 |
11.9 |
eu3 |
NDVI Mar |
9.7 |
9.5 |
eu6 |
NDVI June |
7.8 |
0.5 |
eu10 |
NDVI Oct |
6.7 |
15.8 |
eu7 |
NDVI Jul |
2.2 |
1.2 |
eu2 |
NDVI Feb |
2.1 |
0.6 |
eu9 |
NDVI Sep |
0 |
0 |
eu1 |
NDVI Jan |
0 |
0 |
eu12 |
NDVI Dec |
0 |
0 |
eu11 |
NDVI Nov |
0 |
0 |
Table 3. Population status of A.
cathcartii related to model thresholds.
Occurrence localities |
Habitat suitability thresholds |
Current habitat status |
Number of individuals in
occurrence localities |
|||
Adult |
Sapling |
Seedling |
Total |
|||
Dhansiri |
Low |
Degraded open forest |
15 |
4 |
0 |
19 |
Dhansiri |
High |
Moist semi evergreen |
17 |
7 |
5 |
29 |
Dhansiri |
High |
Moist semi evergreen |
17 |
6 |
2 |
25 |
Dhansiri |
Medium |
Mixed deciduous |
13 |
7 |
3 |
23 |
Dhansiri |
Medium |
Mixed deciduous |
16 |
8 |
0 |
24 |
Daldali |
Low |
Degraded open forest |
10 |
9 |
2 |
21 |
Daldali |
Medium |
Mixed deciduous |
14 |
9 |
6 |
29 |
Daldali |
Medium |
Mixed deciduous |
18 |
11 |
5 |
34 |
Daldali |
High |
Moist semi evergreen |
16 |
10 |
0 |
26 |
Daldali |
High |
Moist semi evergreen |
17 |
9 |
0 |
26 |
Nambar |
High |
Moist semi evergreen |
12 |
10 |
6 |
28 |
Nambar |
High |
Moist semi evergreen |
10 |
9 |
0 |
19 |
Nambar |
Low |
Degraded open forest |
11 |
5 |
0 |
16 |
Nambar |
High |
Moist semi evergreen |
11 |
7 |
3 |
21 |
Nambar |
Medium |
Mixed deciduous |
16 |
9 |
2 |
27 |
Lahorijan |
Medium |
Mixed deciduous |
13 |
4 |
0 |
17 |
Lahorijan |
Medium |
Mixed deciduous |
15 |
9 |
4 |
28 |
Lahorijan |
Low |
Degraded open forest |
13 |
5 |
0 |
18 |
Lahorijan |
Medium |
Mixed deciduous |
15 |
10 |
5 |
30 |
Lahorijan |
High |
Moist semi evergreen |
11 |
7 |
2 |
20 |
Matipung |
High |
Moist semi evergreen |
13 |
6 |
4 |
23 |
Matipung |
Medium |
Mixed deciduous |
12 |
6 |
3 |
21 |
Matipung |
Medium |
Mixed deciduous |
11 |
7 |
2 |
20 |
Matipung |
Medium |
Mixed deciduous |
14 |
8 |
2 |
24 |
Matipung |
Low |
Degraded open forest |
15 |
5 |
1 |
21 |
Total |
|
|
345 |
187 |
57 |
589 |
Table 4. Habitat types of A. cathcartii identified through field surveys and high resoultion Google Earth Pro satellite imageries.
Habitat suitability thresholds |
Habitat types identified using
high resolution Google earth satellite imageries |
High |
Moist semi evergreen forests
and evergreen forests |
Medium |
Mixed deciduous forests and
grasslands |
Low |
Degraded open forests and home
stead gardens |
For
figures & image - - click here
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https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:92813-1#distribution-map