Distribution
and habitat preferences of tiger beetles (Coleoptera:
Cicindelidae) of the riverine ecosystems of Sri Lanka
Chandima D. Dangalle 1,
Nirmalie Pallewatta 2
& Alfried P. Vogler
3
1,2 Department of
Zoology, Faculty of Science, University of Colombo, Cumaratunga
Munidasa Mawatha, Colombo
03, P.O. Box 00300, Sri Lanka
3 Department of
Entomology, The Natural History Museum, Cromwell Road, London, SW7 5BD, United
Kingdom
1 cddangalle@gmail.com
(corresponding author), 2 nirmalip@yahoo.com, 3 a.vogler@nhm.ac.uk
Abstract: Tiger beetles
have been observed in many riverine ecosystems of Sri Lanka. However, current locations, species,
distribution of species, habitat preferences and possible interactions between
species are unknown. The present
study intends to investigate these details and provide information that can be
used in further studies. Tiger
beetles are sampled from 15 riverine locations and examined for identification,
body weight and body length. The
riverine locations are analysed for locational,
climatic and soil parameters and microhabitat details are recorded. Statistical analysis using One-Way
Analysis of Variance and Tukey’s pair comparison
method of Minitab 16.0 statistical software package is conducted to compare the
body sizes of species. Further, a
statistical comparison between the climatic and soil parameters of the
locations of Cylindera (Ifasina) labioaenea
and that of other species are carried out.
The study reveals five tiger beetle species Cylindera
(Ifasina) labioaenea
Horn, Cylindera (Ifasina)
willeyi Horn, Cylindera
(Ifasina) waterhousei
Horn, Calomera cardoni
Fleutiaux, Calomera
angulata Fabricius,
from the riverine ecosystems of Sri Lanka. Cylindera
labioaenea is the most common species; C.
willeyi and C. waterhousei
are endemic to Sri Lanka. Cylindera labioaenea,
C. willeyi and C. waterhousei are small, while Calomera
cardoni and Calomera
angulata are medium in size. Cylindera
labioaenea is significantly smaller than C.
willeyi and C. waterhousei,
and resides in locations with significantly higher air temperatures, solar
radiations and significantly lower relative humidity than the other two
species. An optimal temperature
range for the riverine tiger beetles is suggested and their preferences to soil
moisture, soil temperature, soil colour
and soil salinity are discussed.
The occurrence of C. labioaenea
as a single species population while the fact that other species co-exist may
be due to a defensive strategy.
Keywords: Body size, Cicindelidae, climatic and soil preferences, riverine
ecosystems, tiger
beetles.
doi: http://dx.doi.org/10.11609/JoTT.o3674.6195-203
| ZooBank: urn:lsid:zoobank.org:pub:2AFE4FBF-85CB-4804-A120-C17F3F9550F7
Editor: Anonymity
requested. Date
of publication: 26 August 2014 (online & print)
Manuscript details: Ms # o3674 |
Received 22 June 2013 | Final received 12 July 2014 | Finally accepted 28 July
2014
Citation: Dangalle, C.D., N. Pallewatta & A.P. Vogler (2014). Distribution and
habitat preferences of tiger beetles (Coleoptera: Cicindelidae) of the riverine ecosystems of Sri Lanka.
Journal of Threatened Taxa 6(9): 6195–6203; http://dx.doi.org/10.11609/JoTT.o3674.6195-203
Copyright: © Dangalle et al. 2014. 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: The study has
been supported by grant number RG/2003/ZOO/01 and RG/2012/NRB/02 from the
National Science Foundation of Sri Lanka.
Competing Interest: The authors
declare no competing interests.
Author Contribution: CDD conducted the
literature survey on distribution and habitat preferences of tiger beetles of
Sri Lanka and conducted field studies and sampling. She contributed towards
research design and methodology and writing of the paper. NP contributed
towards formulating the initial concept, research design and methodology. APV
contributed by formulating the initial concept.
Author Details: Dr. Chandima Dangalle is a senior
lecturer in Zoology. Her expertise lies in the fields of entomology and
molecular biology. Her research focuses on collecting baseline data on the
distribution and habitat preferences of tiger beetles in Sri Lanka and in
evolution and phylogeny of the species. Dr. Dangalle
conducted her PhD in the Department of Zoology, University of Colombo, Sri
Lanka and Department of Entomology, Natural History Museum, London, United
Kingdom. Dr. Nirmalie
Pallewatta is a senior lecturer and the
current head of the Department of Zoology, University of Colombo, Sri Lanka. A
zoologist by training, Pallewatta received her PhD in
1986 from the Imperial College of Science, Technology and Medicine at the
University of London, United Kingdom. Prof.
Alfried Vogler works
on the molecular systematics of Coleoptera. He has a
joint position at the Natural History Museum and at Imperial College, London,
United Kingdom. Together with PhD students and postdocs, he is currently
working on the insect fauna of Madagascar, to establish the causes of endemicity and diversity, based on large-scale DNA
sequencing of entire communities.
Acknowledgements: We wish to thank
the Department of Wildlife Conservation, Ministry of Environment, Sri Lanka for providing permits necessary for field work and
sample collection. We are grateful to Prof. Nimal Dangalle, Department of Geography, University of Kelaniya, Sri Lanka for his
assistance in the preparation of maps and list of locations.
For
figures, images, tables -- click here
Introduction
Tiger beetles (Coleoptera: Cicindelidae) are colourful insects that are distributed worldwide. They have been studied intensively in
many countries and are among the few insect groups for which endangered species
are declared and placed on national Red Lists (Pearson 2011).
Fifty-nine species
of tiger beetles have been recorded from Sri Lanka, of which 39 are endemic (Dangalle et al. 2012a). The genera Collyris, Neocollyris,
Tricondyla and Derocrania
consists of arboreal species, while the majority of species are
included in the genus Cicindela (currently
split into a large number of genera, according to Pearson et al. 2006) which is
terrestrial (Dangalle et al. 2011a). The terrestrial species are found in a
variety of sandy, open environments of which most tend to prefer the riverine
habitat because of close proximity to water and food resources and safety from
predators (Bhargav & Uniyal
2008; Dangalle et al. 2012a). Only nine species of tiger beetles are
so far known from the riverine ecosystems of the island amongst vegetation and
on sandy banks along small to large rivers (Table 1).
Currently,
riverine ecosystems of many countries are facing threats from land development
and agricultural practices that lead to loss of riverine invertebrates (Hudgins
et al. 2011). Off-road vehicles and
human traffic along Genesee River, New York has caused local extinctions of
Cobblestone tiger beetles (Cicindela marginipennis) (Hudgins et al. 2011), while toxic
chemicals and other water-borne pollutants in the Red River, China has
threatened the survival of several tiger beetles (Shook & Xiao-Qiang 2006). In
Sri Lanka, the endemic species Cylindera (Ifasina) willeyi
has become locally extinct from its historical riverine locations in the
Central Province and Labugama, Western Province due
to unsuitability and loss of these former habitats (Dangalle
et al. 2011). However, records on
tiger beetles of the riverine ecosystems of Sri Lanka are few, and specific
habitat requirements and distribution of species are poorly understood. The increase in the island’s population,
accompanied by expansion of the land area under urban, agricultural and
industrial development have contributed to the loss and reduction of extents of
natural ecosystems their inherent species as well as genetic diversity. Therefore, it is imperative that the
tiger beetles inhabiting the riverine ecosystems of Sri Lanka be recorded and
investigated. The present study
intends to record the tiger beetles of riverine ecosystems of Sri Lanka,
investigate their current locations and distribution and record habitat
preferences. The study will provide
preliminary information that can be used in future studies for assessing their
conservation status.
Materials and Methods
Study Area
Forty-two riverine
locations of Sri Lanka were investigated for the occurrence of tiger beetles
from June 2003 to October 2006 and May 2013 to May 2014. These locations were situated in
Colombo, Gampaha and Kalutara
districts of the Western Province; Ratnapura and Kegalle districts of the Sabaragamuwa
Province; Puttalam and Kurunegala
districts of the North-Western Province; Anuradhapura District of the
North-Central Province; Nuwara, Nuwara
Eliya and Matale districts
of the Central Province, and Hambantota District of
the Southern Province. The
locations consisted of major rivers, streams, water canals, ferrys
and waterfalls. Each location was visited twice during the study period and river banks, sand bars, moist rocks and shrub areas were
searched for beetles between 9.00 and 17.00 hr.
Collection and
Identification
Tiger beetles were
collected using a standard insect net and preserved in 70% alcohol. Permission to make collections was
obtained through a permit issued by the Department of Wildlife Conservation,
Ministry of Environment and Natural Resources of Sri Lanka.
Species
identification was carried out according to the taxonomic keys of the Cicindela of the Indian Subcontinent by Acciavatti & Pearson (1989), and descriptions of Horn
(1904) and Fowler (1912). Nomenclature is based upon Wiesner
(1992) except for the use of Calomera instead
of Lophyridia, based upon Lorenz (1998).
Measurement of
body weight and body length
Body weight and
body length were estimated for 42 tiger beetles, viz:
21 specimens of Cylindera (Ifasina) labioaenea,
eight specimens of Cylindera (Ifasina) willeyi,
seven specimens of Cylindera (Ifasina) waterhousei,
three specimens of Calomera cardoni and three specimens of Calomera
angulata.
Body weight of the
alcohol fixed beetles was determined to the nearest mg using an analytical
balance (Chyo JL180, Chyo
Balance Corp., Japan).
Body length was
estimated by measuring the distance from the frons of the head to the elytral apex when the head was in the normal feeding position. Caudal spines on the elytral
apex were disregarded. Based on the
references of Acciavatti & Pearson (1989), McCairns et al. (1997) and Zerm
& Adis (2001), body length of beetles were
categorized as follows: less than 8mm - very small, 8–10 mm - small,
10–15 mm - medium, 15–20 mm - large, more than 20mm - very large.
Measurements of
body length were taken using a dissecting microscope (Nikon Corporation SE,
Japan) with an ocular micrometer (Nikon, Tokyo, Japan) that was calibrated by a
stage micrometer (Olympus, Japan).
Measurement of
Habitat Parameters
Climatic and soil
parameters of the riverine locations of tiger beetles were recorded in each
visit using standard methods. The
air temperature, solar radiation, relative humidity and wind speed were
measured using a portable integrated weather station (Health Enviro-Monitor, Davis Instrument Corp., Hayward, USA). The soil temperature (using Insert soil
thermometer SG 680-10), soil pH (using portable soil pH meter Westminister No.259), soil salinity (using an YSI model 30
hand-held salinity meter) and soil colour (measured
by comparison with a Munsell soil colour
chart (Year 2000 revised washable edition) were estimated in each selected
habitat. Soil moisture was detected
using a gravimetric method (determined by selecting five random spots of a
given site, collecting samples to a depth of 10 cm and estimating the
difference in weight before and after oven drying to 107–120 0C
in the laboratory).
Statistical
Analysis
The body weights
and body lengths of the five species were statistically compared. The climatic and soil parameters of the
10 locations of Cylindera (Ifasina) labioaenea
were compared with the five locations of other species willeyi,
waterhousei, cardoni,
and angulata). Statistical comparisons were
done using One-Way Analysis of Variance and Tukey’s
pair comparison method of the Minitab 16.0 statistical software package.
Results
Locations of tiger
beetles
Tiger beetles were
encountered in 15 riverine locations of 42 locations investigated. They were recorded in the districts of
Colombo, Gampaha, Kalutara
of the Western Province; Ratnapura
and Kegalle districts of the Sabaragamuwa
Province and Puttalam, Kurunegala
of the North-Western Province of Sri Lanka (Fig. 1 and Table 2). Beetles were found inhabiting river banks, amongst shrubs and grasses near the river and
on moist rocks (Table 2).
Recorded Species
Five species Cylindera (Ifasina)
labioaenea, Cylindera
(Ifasina) willeyi,
Cylindera (Ifasina)
waterhousei, Calomera
cardoni, Calomera
angulata, were recorded from riverine locations
of Sri Lanka (Image 1). C. labioaenea was the
most common species and dominated the other species in terms of occurrence
(Fig. 2). C. willeyi and C. waterhousei
are endemic to Sri Lanka.
Body Size
Small and medium
sized tiger beetles were recorded from riverine locations. Cylindera
labioaenea, C. willeyi
and C. waterhousei were
categorized as small tiger beetles and Calomera
angulata and C. cardoni
were categorized as medium sized tiger beetles. When considering the body length, labioaenea was significantly smaller than willeyi and waterhousei,
and angulata was significantly smaller
than cardoni. However, significant differences were
only evident between small and medium sized beetles according to body weight
(Table 3).
Habitat Parameters
The climatic and
soil parameters for the riverine locations of tiger beetles
is given in Table 4. When
considering the comparison between habitat parameters of the locations of labioaenea and locations of other species,
significant differences were evident.
Air temperature and solar radiation was high (p<0.05) in the
locations of labioaenea than of the other
species, while relative humidity was significantly low (Table 5).
Discussion
Cylindera (Ifasina) labioaenea was the most common tiger beetle species
and occurred as a single species population in all its locations. Calomera
cardoni co-occurred with Calomera
angulata at Ma Oya, while willeyi co-occurred with waterhousei at the stream in Handapangoda.
When examining the
body size of species, labioaenea was the
smallest species with a significantly lower body weight and body length. In turn, the habitats of the species had
a significantly high air temperature and solar radiation, and a low relative
humidity reflecting comparatively warm, dry environments. In terrestrial arthropods the body size
of ants has been shown to decrease with temperature whereas bees, butterflies
and moths show a variety of body size-climate patterns (Entling
et al. 2010). In tiger beetles
large body size has been associated with coastal and reservoir habitats with
high wind speed, low soil moisture and high soil pH, while species with small
body have been associated with riverine habitats with low wind speed, high soil
moisture and low soil pH (Dangalle et al. 2013). The interspecific mechanism, starvation
resistance predicts an increase in body size towards cold environments
(Greenberg 1979; Entling et al. 2010), while
accelerated maturation leads to smaller adult size at high temperatures (Entling et al. 2010).
Increased temperature is known to increase development and growth rates,
shortening development time resulting in reduced adult size (Kingsolver &
Huey 2008). Thus, in light of these
conditions smaller tiger beetles can be expected in warmer riverine ecosystems
while comparatively larger species may occur in more moist,
cold riverine habitats.
We further
observed that C. labioaenea occurs
as a single species population in all its locations while the other species
co-exist. Hoback
et al. (2001) has shown that in sympatric tiger beetles, larger species may act
as intraguild predators on smaller species. In the present study, C. willeyi and C. waterhousei
that co-existed at Handapangoda were statistically
similar in size (body lengths 9.19±0.11 and 8.80±0.27 respectively), while the
sympatric Calomera cardoni
and C. angulata were both in the medium
size range (body lengths 13.18±0.74 and 10.72±0.10 respectively). According to Hoback
et al. (2001), smaller species compensate for predation risk by defensive behaviours including a shift in habitat use and a change in
foraging activity in the presence of the larger species. However, the present study indicates
that the smallest species, C. labioaenea,
may have completely avoided the habitats of the larger species as a defensive
strategy after experiencing predatory encounters. More investigations and more sampling in
riverine locations are required to provide more evidence to this fact.
When considering
the habitat preferences tiger beetles, were found foraging at air temperatures
of 35.13±0.53 0C. Tiger
beetle activity is highly dependent on air temperature and many species display
maximum activity at an optimal temperature range that
is decided by thermoregulatory mechanisms, desiccation and prey availability (Dreisig 1980; Schultz & Hadley 1987). Our data suggests that the optimal
temperature range of the riverine tiger beetles lies between 31.00–41.00 0C.
Tiger beetles are
also sensitive to soil moisture, soil salinity and soil temperature of
locations due to preferences in oviposition and
larval development (Romey & Knisley
2002; Cornelisse & Hafernik
2009). When considering soil moisture,
high percentages are found in riverine ecosystems (16.31±3.68) when comparing
with the reservoir ecosystems (4.25±0.67) (Dangalle
et al. 2012) and coastal ecosystems (4.60±1.41) (Dangalle
et al. 2013b) of tiger beetles. As C. labioaenea,
C. willeyi, C. waterhousei and Calomera
cardoni were restricted to riverine ecosystems
and not observed in other habitat types, it is possible that soil moisture is a
key factor contributing to the habitat preference of species. Soil temperature
in riverine ecosystems is low (31.54±0.62 0C) when comparing with
reservoir ecosystems (33.64±2.11 0C) (Dangalle
et al. 2012) and coastal ecosystems (34.71±0.95 0C) (Dangalle et al. 2013b) suggesting that this factor may also
contribute to the habitat preferences of riverine tiger beetles. When considering soil colour, tiger beetles are known to occur in soils which match their structural colouration. Blending of structural colouration with the colour of
the surrounding soil enables tiger beetles to evade attack from natural enemies
such as birds, bats and robberflies (Seago et al. 2009). As tiger beetles collected from riverine
habitats were mainly dark brown and bronze with light yellow elytral maculations and spots,
their preference to soils of yellow to dark brown is apparent. Further, we observed that tiger beetles
of riverine ecosystems prefer soils with non-saline conditions.
Calomera angulata which is common to reservoir habitats of Sri Lanka (Dangalle et al. 2012) was also observed in riverine
ecosystems. However, as they were
discovered in only two locations, the preference of the species for riverine
habitats needs to be further investigated.
As the riverine
ecosystems provide refugia to two endemic tiger
beetle species of the country as well as other tiger beetles better decisions
regarding the design, planning and implementation of conservation strategies of
these ecosystems are required.
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