DIVERSITY AND ABUNDANCE OF COLEOPTERA IN AN OAK FOREST OF KUMAUN
A. Garia*, D. Goswami and B. R Kaushal
Post Graduate Department of Zoology,
Kumaun University, Nainital-263002, India
Received: 04-07-2019 Accepted: 25-12-2019
Species richness, abundance and biomass and species diversity of Coleoptera in an oak forest of Kumaun Himalaya, Uttarakhand were determined during August 2013 to July 2015. A total of 18 species belonging to 7 families were collected. Maximum abundance and biomass were 16 ind. ha-1 and 1565 mg ha-1, respectively. Family Chrysomelidae was the dominant family with maximum number of individuals (37.9%). Shannon-Wiener diversity index (H’) ranged from 0 to 0.28 and Evenness (E) ranged from 0 to 0.033 indicating lower values were due to lower number of species and individuals recorded. Further, 12 species of pollinators were recorded visiting different plants and trees regularly.
Key words: Coleoptera, species richness, abundance, species diversity, pollinators, oak forest.
The kingdom Animalia is represented by 1,552,319 species under 40 phyla. Among these, the phylum Arthropoda alone represents 1,242,040 species, or about 80 per cent of the total. The most successful group, the Insecta (1,020,007 species), accounts for about 66 percent of all animals. The most diverse and successful insect order, Coleoptera (387,100 species), represents about 38 percent of all insect species (Zhang 2011).
Beetles (Coleoptera) are considered the most taxonomically diverse insect group that comprises major components of ecosystems in terms of biomass, species richness and ecological roles (Stack 2015). About 400,000 species have been described (Hammond 1992), comprising about 25% of the Earth’s total animal diversity (Rosenzweig 1995; Hunt et al. 2007). Beetles play important roles in pollination, herbivory, granivory, predator-prey interactions, decomposition and nutrient cycling, and soil disturbances (Huffaker and Gutierrez 1999).
The diversity of beetles is very wide. They are found in all major habitats, except marine and the Polar regions. There are particular species that are adapted to practically every kind of diet. The family Scarabaeidae is the largest family of insects which contains more than 30000 species in the world (Fincher et al., 1981). Coleoptera are found in nearly all natural habitats, that is, vegetative foliage, from trees and their bark to flowers, leaves, and underground near roots, even inside plants like galls, tissue, including dead or decaying ones (Gullan and Cranston, 2010). About 3/4 of beetle species are phytophagous in both the larval and adult stages, living in or on plants, wood, fungi, and a variety of stored products, including cereals, tobacco, and dried fruits.
The present investigation is aimed at understanding certain structural and functional aspects of an oak forest community in Kumaun Himalaya. The main objectives were to determine species richness, abundance and biomass, species and trophic level diversity, secondary net production and role of insects as pollinators in an oak forest from August 2013 to July 2015.
Study Area: The study site Naina Devi Himalayan Bird Conservation Reserve is located at Kilbury (290 39 ‘N and 790 44’E longitude; altitude 2528m) about 13 km from Nainital. The area studied is approximately 2 ha and is dominated by Quercus leucotrichophora A. Camus, Q. floribunda Lindl., Q. semecarpifolia Smith, Q. lanuginosa D. Don and Q. glauca Thunb. tree species. Temperature ranged from 4.60C to 25.70C (June). Maximum rainfall (69.2%) was reported during the months of July to September. On this basis, the year can be divided into three seasons namely, rainy (July to October), winter (November to February) and summer (March to June).
MATERIALS AND METHODS
Sampling of insects was done at an interval of 30 days. The insects were collected by “Sweep sampling method (Gadagkar et al., 1990) and hand-picking (Jonathan, 1990). The collected insects were killed in jars containing ethyl acetate and were oven-dried to constant weight (600C for 24 h). Each dried specimen was weighed in a single pan electric balance (0.01 mg accuracy) for biomass estimation. The collected insects were identified at Forest Research Institute, Dehradun.
Species Diversity and Evenness: Species diversity H’ (S) was calculated using Shannon-Wiener expression (1963):
H’ (P) = Type equation here. S
H’(S) = – Σ pi log pi
Where Pi = ni/N; ni is the number of species present in the season; and N is the number of individuals, S denotes the number of seasons.
Evenness (Buzas and Gibson’s evenness) E2: Buzas and Gibson’s Evenness (E2) was calculated using:
E2= e H / S
Where, S is the number of taxa and H is the Shannon Index.
Secondary production comprises that portion of energy which is assimilated by the consumer and is transferred into organic matter, useful as source of energy for other organisms in ecosystem. Time series biomass data was analyzed using Wiegert’s (1965) equation for the estimation of secondary production:
P = S + Σ (Ni + Ni– 1) (Wi – Wi-1)
Ni = Number of insect present at time 1,
Wi = Mean weight per insect at time 1,
i = Sampling time (Date)
S = Standing crop at time when i = 1
It was assumed that Ni ≤ Ni-1 and Wi ≥ Wi-1. However, when Wi was less than Wi-1, the production was considered to be zero.
RESULTS AND DISCUSSION
Species richness: A total of 193 individuals belonging to 18 species of 7 families were collected (Table 1). Family Coccinellidae was dominant both in terms of number of species (33.3%) and individuals (32.7%) collected (Table 2).
Monthly variation in the species content is presented in Table 3. Maximum numbers of species (09) were recorded in the months of June and July while Coleopterans were completed absent during winters in the months of (January and February).
Species richness was positively correlated with maximum temperature (r=0.88; P≤0.01; df=12) (Fig.1a), minimum temperature (r=0.75; P≤0.01; df=12) (Fig. 1b), and rainfall (r=0.7; P≤0.01; df=12) (Fig. 1c).
ABUNDANCE AND BIOMASS: Inter-annual variations in population density occurred: density ranged from 0 ind. ha-1 (30 December) to 11 ind. ha-1 (30 August) during August 2013 to July 2014, and from 0 ind. ha-1 (30 December) to 30 ind. ha-1 (30 June) during August 2014 to July 2015.
.Abundance of Coleoptera was positively correlated with maximum temperature (r=7580; p≤0.01; df=12), (Fig. 2a), minimum temperature (r=0.873; p≤0.01; df=12) (Fig. 2b), and rainfall (r=0.738; p<<0.05; df=12) (Fig. 2c).
Table 3: Shannon-Wiener diversity index (H’) and Evenness of Coleopteron in an oak forest during August, 2013 to July, 2015
Biomass values ranged from 0 mg ha-1 (30 December) to 1095 mg ha-1 (30 August) during August 2013 to July 2014, and from 0 mg ha-1 (30 December) to 2960 mg ha-1 (30 June) during August 2014 to July 2015.
Biomass of Coleoptera was positively correlated with maximum temperature (r=0.749; p≤0.01; df=12), (Fig. 3a), with minimum temperature (r=0.738; p≤0.01; df=12) (Fig. 3b), and with rainfall (r=0.745; p<<0.05; df=12) (Fig. 3c).
Abundance and biomass of Coleopteron were also positively correlated with maximum temperature (r=0.998; p≤0.01; df=12), (Fig. 4).
Species Diversity and Evenness: Shannon index of diversity is considered to be the most complete measures of diversity because it takes into account both number of species and the abundance of each species (Shannon and Wiener, 1963). The Shannon Wiener Diversity Index (H’) and Evenness (E) calculated for each month is presented in Table 3.
Species diversity varied from 0 to 0.33.Maximum species diversity (0.33) in the month of July and minimum (Zero) during the months of January and February.
Buzas’s Evenness which takes into account the distribution of species and their numbers across gradients has returned low values between 0 to 0.080.
Monthly fluctuations recorded were due to changes in the numerical importance of some of the species. Diversity was zero during the months of January and February when insects were not recorded due to extreme cold conditions.
Diversity of order Coleoptera varies with season, being abundant for only a few months and absent or rare during other months of the year.
Insects as Pollinators: Twelve species of coleopteran pollinators visiting different plants and trees were recorded in the present study. Pollinators are essential for survival of forest ecosystems and strongly influence ecological interactions, floral diversity and genetic variation in the plants community. Although 80% the insect pollination is performed by Hymenoptera, bees in particular (Sihag, 1988; Taha and Bayoumi, 2009; Joshi and Joshi, 2010) but also by Lepidoptera (Hodges et al., 2002, Sharma and Mansotra, 2015, Kumar et al., 2016 and Sharma et al., 2020), Coleoptera (Pande, 2013 and Joshi, et al., 2016) and Diptera (Larson et al., 2001). Pollinators recorded in the present study could also thus fulfill ecological functions such as pollination and plant-insect interactions.
It is thus concluded from the present study that population of coleoptera is influenced by environmental factors and refuge habitat. Low species Diversity (H’) and Evenness (E) could be attributed to low species richness and abundance of insects. Natural habitats conservation is very important for the existence of coleopterans species. Further studies are required for the identification of rare species of coleoptera.
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