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Occurrence of a new type of stingless bee in Kerala. Evidence from morphometric analysis

von Prem Jose Vazhacharickal (Autor) Sajan Jose K. (Autor)

Wissenschaftliche Studie 2016 36 Seiten

Biologie - Zoologie

Leseprobe

Table of contents

Table of figures

List of abbreviations

Occurrence of a new type of stingless bees in Kerala: Evidence from morphometric analysis

1. Introduction

2. Materials and Methods
2.1 Study area
2.2 Study design and data collection
2.3 Morphometric measurements
2.4 Statistical analysis

3. Results
3.1 Descriptive analysis
3.2 Correlation analysis
3.3 Principal component analysis

4. Discussion

5. Conclusions

Acknowledgements

References

Table of figures

Figure 1. Morphometric characters considered for the analysis of worker and drone bees of stingless bees in Kerala: 1 = head length, 2 = head width, 3 = proboscis length, 4 = distance between two dorsal ocelli, 5 = dorsal ocello-ocular distance, 6 = antennal length, 7 = fermur length, 8 = tibia length, 9 = metatarsus length, 10 = metatarsus width, 11 = forewing length, 12 = forewing width, 13 = pterostigma length, 14 = pterostigma width, 15 = hind wing length, 16 = hind wing width, 17= number of hamuli, 18 = tergite length, 19 = sternite length, 20 = width of sternum, 21 = mandible length, 22 = mandible width.

Figure 2. Habitats of the newly reported stingless bees a) small entrance tube on laterite rock; b) breaking of laterite rock using iron wedges; c) cut opened laterite rock showing internal tunnel and brood; d) laterite rock part showing internal tunnel structure; e) honey pots; f) pollen pots; g) brood structure.

Figure 3. Habitats of the newly reported stingless bees in wooden log nest a) wooden log nest; b) nest opened showing internal structures; c) honey and pollen pots; d) bees with brood cells; e) and f) honey pots; g) entrance tube.

Figure 4. Scree plot for finding the various components to be extracted during Principal Component Analysis among stingless bee workers.

Figure 5. Component plot in rotated space during principal component analysis among stingless bee workers.

Figure 6. Distribution of factor scores among stingless bee workers across various locations in Kerala.

Table of tables

Table 1. Description of the morphometric variables used to classify Trigona iridipennis Smith in Kerala, India.

Table 2. Site description of the selected farms (D1-D9) across Kerala, India for collecting drone bees during 2011-2013.

Table 3. Description of Trigona iridipennis Smith worker and their morphometric characteristics.

Table 4. Description of some morphometric of Trigona iridipennis Smith worker and their characteristics.

Table 5. Pearson correlation coefficients between various morphometric characters of Trigona iridipennis Smith workers (n=30) in the various districts across Kerala, India during 2011-2013.

Table 6. Pearson correlation coefficients between various morphometric characters of Trigona iridipennis Smith workers (n=30) in the various districts across Kerala, India during 2011-2013.

Table 7. Eigenvalues and percentage of variance explained by the first four components in a PCA of Trigona iridipennis Smith worker in Kerala.

Table 8. Component matrix in a PCA of Trigona iridipennis Smith worker in Kerala.

Table 9. Rotated component matrix in a PCA of Trigona iridipennis Smith worker in Kerala.

Table 10. Component score coefficient matrix in a PCA of Trigona iridipennis Smith worker in Kerala.

List of abbreviations

Abbildung in dieser Leseprobe nicht enthalten

Occurrence of a new type of stingless bees in Kerala: Evidence from morphometric analysis

Prem Jose Vazhacharickal1* and Sajan Jose K2

* premjosev@gmail.com

1 Department of Biotechnology, Mar Augusthinose College, Ramapuram, Kerala, India-686576

2 Department of Zoology, St. Joseph’s College, Moolamattom, Kerala, India-685591

Abstract

Stingless bees are limited to tropics and subtropics with diversity in species and share morphological and behaviour patterns. Stingless bees are major pollinators of flowering plants in the tropics and improve crop productivity. Trigona iridipennis Smith are kept in India for centuries for the high medicinal value of honey as well as propolis and bee wax. A wide range of variations especially worker and drone body size and measurement were reported. Morphometric and geometric analysis provide a valuable tool for the discriminating variations among various honey bees and stingless bees. Based on these back ground, our objectives of this study were to 1) to characterize the morphometric aspects of workers in this reported new species of stingless bees 2) to identify the various similarities and differences existed among based on factor and principal component analysis with Trigona iridipennis Smith. A total of 30 samples of workers were collected and analyzed various morphometric characters including head length (HL), head width (HW), proboscis length (PL), distance between two dorsal ocelli/lower intercocular distance (DBO), dorsal ocello-ocular distance (DOOD), antennal length (AL), thorax femur length (TFL), thorax tibia length (TTL), thorax metatarsus length (TML), thorax metatarsus width (TMW), thorax forewing length (TFWL), thorax forewing width (TFWW), pterostigma width (PtStW), pterostigma length (PtStW), hind wing length (HWL), hind wing width (HWW), number of hamuli (HAM), abdominal tergite length (AbTL), abdominal sternum width (AbSW), mandible length (MdL) and mandible width (MdW), head length width ratio (HLW), thorax metatarsus length width ratio (TMLW) and thorax forewing length width ratio (TFWLW). One sample (SS1) from showed distinct differences in habitat preference (Laterite rock), appearance (size and colour), behaviour (passive) and nest architecture (narrow round entrance tube, snow white brood, cream white food pots). The present study based on the morphometry of stingless bees across Kerala shows that, in spite of the morphological and behavioural variations exhibited by the bees, members of all samples belong to Trigona iridipennis. But one sample (SS1) shows entirely different morphometric characteristics. It was found that this sample belongs to genus Lisotrigona

Keywords: Stingless bees; Meliponiculture; Cerumen; batumen; Brood.

1. Introduction

The decline in honey bee population happen due to destruction of natural habitat, intensive agriculture, diseases and climate change despite of role in pollination and ecosystem services ( et al., 2008; Stingless bees are limited to tropics and subtropics with diversity in species and share morphological and behaviour patterns (. The stingless bee found in Kerala is Trigona iridipennis Smith also called ‘dammer bees’ locally known as ‘Cherutheneecha’ in Malayalam (Singh, 2013).

Trigona iridipennis Smith are kept in India for centuries for the high medicinal value of honey as well as propolis and bee wax (Rasmussen, 2013; Cortopassi-Laurino et al., 2006; Virkar et al., 2014; Kumar et al., 2012; Andualem, 2013; Choudhari et al., 2013; Choudhari et al., 2012; Rasmussen, 2013) and serves a high demand from pharmaceutical sector (Kumar et al., 2012). Recent studies also showed the various nesting behaviour of Trigona iridipennis Smith in natural habitat as well as its adaptability various antroropoegnic habitats (Virkar et al., 2014; Singh, 2013; Nair and Nair, 2001; Kumar et al., 2012; Jose and Thomas, 2012; Jose and Thomas, 2013). A wide range of variations especially worker and drone body size and measurement were reported (Pignata et al., 1996; Vijayakumar and Jayraj, 2013; Danaraddi and Viraktamath, 2010; Danaraddi et al., 2012). Morphometric and geometric analysis provide a valuable tool for the discriminating variations among various honey bees and stingless bees (Vijayakumar and Jayraj, 2013; Wappler et al., 2012; Monteiro et al., 2002; Hernández et al., 2007; Francoy et al., 2011; Quezada-Euán et al., 2011; Hartfelder and Engels, 1992). These tools were sucessfuly utilized for the genetic lineage, geographic origin, heritability of shape, gender identification, differtiation and conservation (May-Itzá et al., 2012; May-Itzá et al., 2010; Quezada-Euán et al., 2011; Francoy et al., 2011; Francoy et al., 2009; Hernández et al., 2007; Monteiro et al., 2002; Rattanawannee et al., 2010; Combey et al., 2013). Further possibilities of phylogentic relationships were explored using advanced molecular biology tools especially DNA microsatellites, AFLP markers, mitochondrial DNA and nuclear DNA (Arias and Sheppard, 2005; Francisco et al., 2008; Arias et al., 2006; Theeraapisakkun et al., 2010a; Theeraapisakkun et al., 2010b; Theeraapisakkun et al., 2011; May-Itzá et al., 2012). We report a new species of stingless bees in Kerala which are different from the morphometric studies of the Trigona iridipennis Smith. Based on these back ground, our objectives of this study were to 1) to characterize the morphometric aspects of workers in this reported new species of stingless bees 2) to identify the various similarities and differences existed among based on factor and principal component analysis with Trigona iridipennis Smith .

2. Materials and Methods

2.1 Study area

Kerala state covers an area of 38,863 km2 with a population density of 859 per km2 and spread across 14 districts. The climate is characterized by tropical wet and dry with average annual rainfall amounts to 2,817 ± 406 mm and mean annual temperature is 26.8°C (averages from 1871-2005; Krishnakumar et al., 2009). Maximum rainfall occurs from June to September mainly due to South West Monsoon and temperatures are highest in May and November.

2.2 Study design and data collection

Two locations (panchayaths) of these new stingless bees were located and collected based on farmer’s information and initial baseline survey. A total of 10 worker samples were collected from these locations. The bees were caught using a self-designed net trap of size (200 µm) and the bees were immediately paralysed using chloroform solution (70%v/v) and later stored in eppendof vials with 70% alcohol. Non-destructive methods were followed using sample collection process. The samples were labelled according to the location and stored in airtight boxes until morphometric analysis were conducted. The positions of the locations were recorded with the help of a Trimble Geoexplorer II GPS (Trimble Navigation Ltd, Sunnyvale, CA, USA).

2.3 Morphometric measurements

The bees are dried at 60°C for 24 h in a hot air oven (Labtech 112, lantech, Mumbai) to obtain their dry weight. After the weighing, the bees were rehydrated in glycerol solution (70%v/v) to soften their body. The head and thorax were dissected, and size of the following variables were recorded: head length (HL), head width (HW), proboscis length (PL), distance between two dorsal ocelli/lower inter-ocular distance (DBO), dorsal ocello-ocular distance (DOOD), antennal length (AL), thorax femur length (TFL), thorax tibia length (TTL), thorax metatarsus length (TML), thorax metatarsus width (TMW), thorax forewing length (TFWL), thorax forewing width (TFWW), pterostigma width (PtStW), pterostigma length (PtStW), hind wing length (HWL), hind wing width (HWW), number of hamuli (HAM), abdominal tergite length (AbTL), abdominal sternum width (AbSW), mandible length (MdL) and mandible width (MdW). Head length width ratio (HLW), thorax metatarsus length width ratio (TMLW) and thorax forewing length width ratio (TFWLW) were also determined. The morphometric measurements were made using steromicroscope (Leica E24D, Leica Microsystems, Switzerland) and analysed using LAS EZ version 1.4.0 (IBM Inc., CA, USA).

2.4 Statistical analysis

Descriptive statistics using SPSS 12.0 (SPSS Inc., Chicago, IL, USA) were conducted to summarize the data and graphs were generated using Sigma Plot 7 (Systat Software Inc., Chicago, IL, USA). The data were checked for normal distribution using Kologovic-Smiroff (KS) test. A comparison size metrics among the special samples collected from two different locations were compared with the usual samples collected across various districts and were analysed by means of Principal Component Analysis (PCA). Value scores for each worker and drone bees for each principal component were obtained from the first three components of PCA. Data were analysed by comparing the means at univariate level using ANOVA and multivariate approach (PCA). Colony scores from PCA were compared by means of ANOVA and plotted against pairs of factors.

A principal component analysis (PCA) was performed on the morphometric variables for the data reduction and obtain single measure of size (Wiley, 1981; Pignata and Diniz-Filho, 1996; Quezada-Euán et al., 2007). The PCA was carried out based on a correlation matrix (verified by means of Keiser-Meyer-Olkin measure of sampling adequacy and Bartlett’s test of sphericity) and later analysed using VARIMAX axis rotation. The correlation matrix was selected as the derived principal component 1. A final measure of body size was given by the PC scores that were calculated for each individual as the product of the resulting coefficients in each PC (Quezada-Euán et al., 2007).

3. Results

3.1 Descriptive analysis

The cropping pattern of the collected sites vary with a wide variety plantation crops were natural rubber dominates all the other crops. The morphometric characters of workers varied widely across all the samples. Significant variations in the morphometric characters were observed for workers expect for PL; TML; MdW and AbTL. Highly significant difference (P< 0.001) were observed for HW; DBO; DOOD; AL; TFL; TTL; TMW; MdL; TFWL; TFWW; PtstW; PtstL; HWL and AbSW. The lowest HW among workers was 1.13 ± 0.04 (SS1) while height up to 1.60 ± 0.09 (S1). The lowest AL was seen in SS1 (1.36 ± 0.02) and highest in S1 (1.97 ± 0.04). The lowest MdL and MdW were 0.44 ± 0.01 and 0.16 ± 0.01 respectively. Even though numerical significance were observed in PL; TML; MdW and AbTL, but not able to prove their significance statistically.

3.2 Correlation analysis

Person correlation analysis showed considerable correlation among various morphometric characters in worker and drone bees across Kerala. Highly significant positive correlations were observed among HL and DL, HL and AL, HL and MdL, HL and TFL, HL and TTL, HW and DBO, HW and DOOB, HW and AL, HW and MdL, HW and MdW, HW and TFL, HW and TTL, DBO and AL, DBO and MdL, DBO and TFL, DBO and TTL, DOOB and AL, DOOB and TFL, DOOB and TTL, Al and MdW, Al and TFL, MdL and TFL, MdL and TTL, MdW TFL, MdW and TTL, TFL and TTL. Despite of strong positive correlations, strong negative correlation was observed among PL and DOOB, TMWL and PtStL, TML and PtStL, TWL and PtStL.

3.3 Principal component analysis

The validity PCA of 21 morphometric characters were justified as indicated by the Kaiser-Meyer-Olkin measure of sampling adequacy of 0.65. Bartlett’s test of sphericity was significant (<0.001), indicating that the matrix was equally distributed and thus, suitable for PCA. The components were decided using scree plot and fixed to 4 components. The first three PCs explained 57.2, 12.3 and 10.1% of the total variation in the morphometric data respectively.

Abbildung in dieser Leseprobe nicht enthalten

Figure 1. Morphometric characters considered for the analysis of worker and drone bees of stingless bees in Kerala: 1 = head length, 2 = head width, 3 = proboscis length, 4 = distance between two dorsal ocelli, 5 = dorsal ocello-ocular distance, 6 = antennal length, 7 = fermur length, 8 = tibia length, 9 = metatarsus length, 10 = metatarsus width, 11 = forewing length, 12 = forewing width, 13 = pterostigma length, 14 = pterostigma width, 15 = hind wing length, 16 = hind wing width, 17= number of hamuli, 18 = tergite length, 19 = sternite length, 20 = width of sternum, 21 = mandible length, 22 = mandible width.

Abbildung in dieser Leseprobe nicht enthalten

Figure 2. Habitats of the newly reported stingless bees a) small entrance tube on laterite rock; b) breaking of laterite rock using iron wedges; c) cut opened laterite rock showing internal tunnel and brood; d) laterite rock part showing internal tunnel structure; e) honey pots; f) pollen pots; g) brood structure.

Figure 3. Habitats of the newly reported stingless bees in wooden log nest a) wooden log nest; b) nest opened showing internal structures; c) honey and pollen pots; d) bees with brood cells; e) and f) honey pots; g) entrance tube.

Table 1. Description of the morphometric variables used to classify Trigona iridipennis Smith in Kerala, India.

Abbildung in dieser Leseprobe nicht enthalten

Table 2. Site description of the selected farms (S1, S2, SS1, S3) across Kerala, India for collecting drone bees during 2011-2013.

Abbildung in dieser Leseprobe nicht enthalten

Table 3. Description of Trigona iridipennis Smith worker and their morphometric characteristics.

Abbildung in dieser Leseprobe nicht enthalten

Numbers represent means ± one standard deviation (SD) of the mean.

Table 4. Description of some morphometric of Trigona iridipennis Smith worker and their characteristics.

Abbildung in dieser Leseprobe nicht enthalten

Numbers represent means ± one standard deviation (SD) of the mean.

Table 5. Pearson correlation coefficients between various morphometric characters of Trigona iridipennis Smith workers (n=35) in the various districts across Kerala, India during 2011-2013.

Abbildung in dieser Leseprobe nicht enthalten

*Significant at the level of P< 0.05.

**Significant at the level of P< 0.01.

Table 6. Pearson correlation coefficients between various morphometric characters of Trigona iridipennis Smith workers (n=35) in the various districts across Kerala, India during 2011-2013.

Abbildung in dieser Leseprobe nicht enthalten

*Significant at the level of P< 0.05.

**Significant at the level of P< 0.01.

Table 7. Eigenvalues and percentage of variance explained by the first four components in a PCA of Trigona iridipennis Smith worker in Kerala.

Abbildung in dieser Leseprobe nicht enthalten

Table 8. Component matrix in a PCA of Trigona iridipennis Smith worker in Kerala.

Abbildung in dieser Leseprobe nicht enthalten

Table 9. Rotated component matrix in a PCA of Trigona iridipennis Smith worker in Kerala.

Abbildung in dieser Leseprobe nicht enthalten

Table 10. Component score coefficient matrix in a PCA of Trigona iridipennis Smith worker in Kerala.

Abbildung in dieser Leseprobe nicht enthalten

Figure 4. Scree plot for finding the various components to be extracted during Principal Component Analysis among stingless bee workers.

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Details

Seiten
36
Jahr
2016
ISBN (eBook)
9783668371750
ISBN (Buch)
9783668371767
Dateigröße
1.6 MB
Sprache
Englisch
Katalognummer
v349889
Note
Schlagworte
occurrence kerala evidence

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Titel: Occurrence of a new type of stingless bee in Kerala. Evidence from morphometric analysis