Journal of
Threatened Taxa | www.threatenedtaxa.org | 26 July 2018 | 10(8): 12027–12034
The amphibian diversity
of selected agroecosystems in the southern Western Ghats, India
M.S. Syamili1 & P.O. Nameer2
1,2 Centre for
Wildlife Studies, College of Forestry, Kerala Agricultural University, Thrissur, Kerala, 680656, India
1 syamilimanojcof@gmail.com, 2 nameer.po@kau.in
(corresponding author)
Abstract: A study was conducted to
evaluate amphibian diversity in selected agroecosystems
of central Kerala within the southern Western Ghats of India, from January to
May 2017. A total of 10 anurans were
recorded from cashew plantation, coconut plantation, homegarden and rubber plantation using a combination
of quadrat sampling and visual encounter survey. We recorded three species endemic to the
Western Ghats: Minervarya keralensis,
Pseudophilautus wynaadensis
and Indosylvirana urbis
from these agroecosystems. Pseudophilautus
wynaadensis is a threatened species with
Endangered status as per the IUCN Red List.
The present study shows a strong relationship between the types of agroecosystems and abundance of different amphibian
species. This study highlights the
potential of agroecosystems within and adjacent to
the Western Ghats mountains to act as important abodes
to conserve generalist species of amphibians and to provide a suitable habitat
for threatened and endemic species.
Keywords: Endangered, Minervarya keralensis, frog, Indosylvirana
urbis, Pseudophilautus wynaadensis, threatened species, Thrissur.
doi: http://doi.org/10.11609/jott.3653.10.8.12027-12034
| ZooBank:
urn:lsid:zoobank.org:pub:2C0BC2C3-66A3-4BE0-86FF-D8306F4A9398
Editor: Mirco Solé, Universidade
Estadual de Santa Cruz, Bahia, Brasil. Date of publication: 26 July 2018 (online &
print)
Manuscript details: Ms
# 3653 | Received 26 October 2017 | Final received 30 June 2018 | Finally
accepted 18 July 2018
Citation: Syamili, M.S & P.O. Nameer (2018). The amphibian diversity of selected agroecosystems
in the southern Western Ghats, India. Journal of Threatened Taxa
10(8): 12027–12034; http://doi.org/10.11609/jott.3653.10.8.12027-12034
Copyright: © Syamili & Nameer 2018. Creative Commons
Attribution 4.0 International License. JoTT
allows unrestricted use of this article in any medium, reproduction and
distribution by providing adequate credit to the authors and the source of
publication.
Funding: Kerala Agricultural University.
Competing interests: The authors declare no competing interests.
Author
Details: M.S.
Syamili is
an Assistant Professor and works primarily on herpetofauna
and birds. P.O. Nameer is a Professor and his
research interest include the taxonomy, biogeography
and ecology of the vertebrates except fishes.
Author
Contribution: Both the
authors contributed equally to the field work,
morphometric data collection, analysis and manuscript preparation.
Acknowledgements: We express our deep sense of gratitude and thanks to Dr. Neelesh Dahanukar, IISER, Pune who helped us for analysing
the data. Sreekumar,
E.R. and Harikrishnan, S. helped us in various ways
during the course of the study. We thank the Dean, College of Forestry, Kerala Agricultural University for the financial and
technical support. Azhar Ali, A, Jobin
Joseph, U.S. Amal, Afthab
Faisal, Habeel Sahal, Abhin M. Sunil, Abhirami M. Jayakumar, Dilgith Surendran, M.R. Bharath and
Francis Scaria helped us in the field work. We also
thank the anonymous reviewers and the Subject Editor for their critical
comments.
Introduction
Amphibians are important predator
and prey species in both aquatic and terrestrial habitats, especially in the
tropics where the diversity and abundance of taxa are high. According to Whiles et al. (2006) loss of one
species is akin to loss of two species in the case of amphibians. Baillie et al. (2004) stated that among the
vertebrates of the world, amphibians are the most threatened taxa and have the
highest proportion of species on the verge of extinction. The most pervasive threats to amphibians are
habitat loss and habitat degradation.
For the amphibians of the Western
Ghats the species accumulation curve has not yet reached a plateau (Aravind et al. 2004).
According to Nameer et al. (2015) & Das
(2015) 90% of amphibians in Kerala are endemic to the Western Ghats and 33%
belong to various threatened categories.
Generally, protected area networks are considered as the corner stone of
biodiversity conservation efforts.
Perfecto & Vandermeer (2008) commented
that conservation strategies which focus on tropical forests while ignoring the
multiple land uses in which they are embedded are failed strategies. According to Nair (2008), agroforests can be considered as potential oases for
disappearing species, even though they cannot substitute for natural
forests. Wanger
et al. (2009) assessed the herpetological diversity in cacao agroforests of Southeast Asia, where they observed that
certain habitat features like increase in leaf litter favour
the richness and abundance of disturbance-tolerant species. Bionda et al.
(2011) worked on the amphibians of various agroecosystems
in Argentina and found that there are species which
take advantage of the hydrology and hydroperiod of agroecosystems for their survival. Not all agroecosystems
contribute equally towards conservation.
Hence, for a realistic conservation
strategy one should evaluate the conservation value of these multiple land use
systems such as agroecosystems. The present study is expected to shed light
on the amphibian diversity and richness in agroecosystems
of Kerala.
Study Area
The
study was conducted in the selected agroecosystems in Thrissur
District, southern Western Ghats, Kerala (10.53–10.55 0N &
76.27–76.280E, 20–70 m). The
chosen agroecosystems include, cashew plantation,
coconut plantation, homegarden and rubber plantation (Fig. 1). The study area chosen mostly comes within the
main campus of the Kerala Agricultural University, in Kerala, southern
India. The campus has a total area of
391.44ha and is located very close to the Peechi-Vazhani
Wildlife Sanctuary. The major habitats
include gardens, botanical garden, plantations of
rubber, coconut, plantain, cacao, and orchards of mango, jackfruit, sapota and guava.
The whole area must have been under the forests about one and a half
century or so and was subsequently converted mostly into rubber
plantations. Later the land was handed
over to the Kerala Agricultural University (KAU) in 1971, and the KAU had
developed these areas into the different land uses as is explained above. The 14-year mean minimum temperature is 23.30C
and 10-year mean maximum is 31.90C.
The area receives south-west and north-east
monsoons, the greater portion of the rainfall, however is received from the
south-west monsoon between June and September.
The mean annual rainfall is 2,803.4mm.
The mean number of rainy days per year is 112 days (KAU Weather Station
2014).
The
study was conducted in four selected agroecosystems
such as cashew plantation which is 16 years old and spreads over an area
of 90 acres, a coconut plantation, which is about 35 years old and has an
extent of 50 acres, a homegarden covering eight acres
about 40 years old, and a rubber plantation with an extent of 60 acres and is
about 67 years old.
Methods
The study was conducted from January
2017 to May 2017. Quadrat sampling was
the primary method adopted for the study and was supplemented with visual
encounter survey.
Quadrat Sampling
One hundred quadrats each having a
size of 10m × 10m were deployed in the study area randomly with a minimum
distance of 10m between two quadrats.
The observations were taken between 19:00hr and 20:30hr. Two observers surveyed the quadrat from
opposite corners approaching the center in a clockwise manner for thorough
search of the ground-dwelling amphibians (Harikrishnan
et al. 2012).
Visual Encounter Survey
Visual encounter survey was
conducted in the study locations (Harikrishnan et al.
2012). This was done between 20:30–21:30
hr. LED torches and head lamps were used
to spot the amphibians. During the
survey, a range of possible microhabitats where the amphibians could be seen,
such as rocks, marshes, fallen logs, tree holes, snags and water bodies were
thoroughly examined.
Results and Discussion
Amphibian diversity of selected agroecosystems
A total of 10 anurans belonging to
five families were recorded from the selected agroecosystems
of central Kerala (Table 1). This
includes two species each from the families Microhylidae,
Ranidae and Rhacophoridae,
three species from Dicroglossidae and one species
from Bufonidae.
Dicroglossidae represented 30% of the
amphibians encountered during the present study,
however, these are commensal and generalist species. These include Euphlyctis cyanophlyctis,
Hoplobatrachus crassus and Minervarya
keralensis.
According to Gururaja et al. (2007),
anthropogenic changes in land use type, canopy cover and hydrological regimes
support the presence of more generalist amphibian species.
Three species that are endemic to
Western Ghats namely Minervarya keralensis, Pseudophilautus wynaadensis and Indosylvirana
urbis were reported from the agroecosystems that were studied (Biju
et al. 2004, 2014; Biju & Bossuyt
2009; Gururaja 2012; Das 2015; Sanchez et al. 2018).
Pseudophilautus wynaadensis,
an Endangered species (Biju et al. 2004)
was found to be present in all the agroecosystems
surveyed during the present study (Table 2).
Rathod & Rathod (2013) reported highest
diversity of amphibians from organic coffee plantations of Kodagu
District where diversity of native rainforest trees was also high. Chemical contamination by the use of
fertilizers and pesticides in the agricultural fields lead to incidence of
abnormalities among common frog species as their breeding period coincides with
the time of agrochemical application in the fields (Gurushankara
et al. 2007; Kittusamy et al. 2014; Krishnamurthy et
al. 2008). No abnormalities, however,
were observed among the 569 individuals of amphibians recorded during the
current study.
Quadrat sampling recorded only seven
species from the study location. Though
visual encounter survey also recorded seven species, it recorded three species
that were not recorded through quadrat sampling (Table 1). It is potentially possible to obtain the
complete species inventory of the sampled area when visual encounter survey is
combined with another sampling technique (Eekhout
2010).
Duttaphrynus melanostictus (Schneider, 1799)
During the present study, Common
Indian Toad (Image 1) was encountered from cashew and rubber plantations. It was also sighted in different colour morphs (Images 1A–D) and all individuals were
adults.
Euphlyctis cyanophlyctis (Schneider, 1799)
Skittering Frog (Image 2) was
sighted only at the pond in the rubber plantation. In this case also only adult individuals were
sighted.
Hoplobatrachus crassus (Jerdon, 1853)
Jerdon’s Bullfrog (Image 3) is another species which
was detected only at the pond within the rubber plantation. The individuals sighted included both adults
and juveniles. Hoplobatrachus
crassus as well
as Euphlyctis cyanophlyctis
are species that prefer water bodies, thus justifying their presence at the
pond.
Minervarya keralensis (Sanchez et al. 2018)
Kerala Warty Frog (Images 4A–B) was
detected from the homegarden and from the pond within
the rubber plantations. Only adult
individuals were sighted for this species.
This species was formerly under the genus Fejervarya,
but now is under the new genus Minervarya (Sanchez et al. 2018).
Microhyla rubra (Jerdon, 1854)
Reddish Narrow-mouthed Frog (Image
5) was sighted from the premises of the pond in the rubber plantation during
visual encounter survey. Interestingly,
all the individuals recorded were juveniles of very small size.
Uperodon taprobanicus (Parker, 1934)
Painted Frog was spotted from a tree
hole within the coconut plantation. This
species was sighted only once during the study period.
Hydrophylax malabaricus (Tschudi, 1838)
Fungoid
frog (Image 6) was detected only from the rubber plantation. It was found in the moist areas of the
plantation.
Indosylvirana urbis (Biju et al.,
2014)
Urban
Golden-backed Frog (Image 7) was found on the rocky patches near the pond
within the rubber plantation.
Polypedates maculatus (Gray, 1834)
Common
Indian Tree Frog (Image 8) is one of the most common tree frogs in Kerala. During the visual encounter survey, a male
and female of the species were recorded from the coconut plantation. After the first summer shower in May, one
additional individual was also observed from the coconut plantation.
Pseudophilautus wynaadensis (Jerdon, 1853)
Jerdon’s Bush Frog (Image 9) was the most common frog during the present study
and was recorded from all the agroecosystems selected
for the present study. We observed four
colour morphs of the species during the study period (Image 9A–D). All the 25 quadrats in the homegarden detected the presence of this species. The highest count of the species was from
rubber plantation where there were 30–40 individuals on a single herb of Rauwolfia tetraphylla near
a moist area, due to a leakage in the irrigation pipeline that passed through
the rubber plantation.
It may
be noted that all the amphibians sighted within the rubber plantations were
either located in a pond in the rubber plantation or from artificially wet areas.
Association between the agroecosystems and abundance of amphibians
The
null hypothesis is that there is no association between the type of agroecosystem and abundance of different amphibian
species. The Chi-square test (Chi-square
= 236.6, df = 27, P < 0.0001) suggested that there
is a strong association between the type of agroecosystem
and abundance of different amphibian species (Fig.
2). Correspondence analysis was
performed to understand the association between selected agroecosystems
and amphibian abundance.
Polypedatus maculatus and Uperodon taprobanicus were only present in coconut plantation
and this agroecosystem was not preferred by other
species of amphibians encountered in the study (Fig. 2). All other species of amphibians
prefered rubber plantation. Hoplobatrachus
crassus,
Hydrophylax malabaricus, Euphlyctis cyanophlyctis, Indosylvirana urbis and Microhyla rubra were
exclusively present in the rubber plantation, while Minervarya
keralensis and Pseudophilautus
wynaadensis also preferred homegardens
at some level, while Duttaphrynus melanostictus showed a preference to the cashew
plantation (Fig. 2).
Amphibian abundance and richness was
found to be higher in rubber plantation followed by homegarden
(Fig. 3). This higher amphibian
diversity and abundance in the rubber plantation could be an artifact because
of the presence of a pond as well as the presence of a couple of wet areas due
to anthropogenic interventions, in the rubber plantations. This could also explain the presence of
species such as Euphlyctis cyanophlyctis,
Hoplobatrachus crassus,
Indosylvirana urbis, and Microhyla rubra only from the
rubber plantation, even during the summer months. According to Neckel-Oliveira
& Gascon (2006), presence of an aquatic habitat
is crucial for the existence of certain species of amphibians.
Rathod & Rathod (2013) explained that an
open canopy can increase the temperature and
evaporation and decrease the persistence of moist areas. This can be one reason for fewer encounters
with amphibians from coconut plantation and cashew plantation.
Table 1. Species diversity of amphibians of selected agroecosystems of Thrissur
District, Kerala
Common name |
Scientific name |
Family |
Quadrat sampling |
Visual encounter survey |
IUCN status |
Common Indian Toad |
Duttaphrynus melanostictus |
Bufonidae |
1 |
1 |
LC |
Skittering Frog |
Euphlyctis cyanophlyctis |
Dicroglossidae |
1 |
0 |
LC |
Jerdon’s Bullfrog |
Hoplobatrachus crassus |
Dicroglossidae |
1 |
0 |
LC |
Kerala Warty Frog |
Minervarya keralensis |
Dicroglossidae |
1 |
1 |
LC |
Reddish Narrow-mouthed Frog |
Microhyla rubra |
Microhylidae |
0 |
1 |
LC |
Painted Frog |
Uperodon taprobanicus |
Microhylidae |
0 |
1 |
LC |
Fungoid Frog |
Hydrophylax malabaricus |
Ranidae |
1 |
1 |
LC |
Urban Golden-backed Frog |
Indosylvirana urbis |
Ranidae |
1 |
0 |
NE |
Common Indian Tree Frog |
Polypedates maculatus |
Rhacophoridae |
0 |
1 |
LC |
Jerdon’s Bush Frog |
Pseudophilautus wynaadensis |
Rhacophoridae |
1 |
1 |
EN |
EN - Endangered; LC - Least Concern; NE - Not Evaluated. 0 - Not encountered; 1 – Encountered
Table 2. Amphibian diversity and abundance from selected agroecosystems
Species |
Cashew Plantation |
Coconut Plantation |
Home garden |
Rubber Plantation |
Total |
Duttaphrynus melanostictus |
1 |
0 |
0 |
6 |
7 |
Euphlyctis cyanophlyctis |
0 |
0 |
0 |
5 |
|
Hoplobatrachus crassus |
0 |
0 |
0 |
14 |
|
Minervarya keralensis |
0 |
0 |
3 |
12 |
|
Microhyla rubra |
0 |
0 |
0 |
1 |
1 |
Uperodon taprobanicus |
0 |
1 |
0 |
0 |
1 |
Hydrophylax malabaricus |
0 |
0 |
0 |
1 |
1 |
Indosylvirana urbis |
0 |
0 |
0 |
20 |
|
Polypedates maculatus |
0 |
3 |
0 |
0 |
3 |
Pseudophilautus wynaadensis |
5 |
7 |
143 |
347 |
502 |
Total |
6 |
11 |
146 |
406 |
569 |
Conclusion
Protected areas cover 18% of the
Earth’s land area and 8% of Kerala’s geographical area, and they are considered
to be corner stones of biodiversity conservation. It is a fact that most of these protected
areas are virtual islands embedded within a matrix of multiple land uses. A large proportion of biodiversity coexists
with humans in their managed ecosystems, which can hold minimum viable
populations of rare and endangered native fauna and flora. The potential of such landscapes in
conserving native biodiversity is still untapped. The present study showed that agroecosystems have not only the potential to conserve
generalist species, but also help to provide suitable habitat for some
threatened and endemic species of amphibians.
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