Insect Pest Management, A Current Scenario, 2011 (ed.), Dunston P. Ambrose, Entomology Research Unit, St. Xavier’s College, Palayamkottai, India, pp.123-129. 123 LIN EAR REGRESSION COEFFICIEN T VALUES (R) OF POSTEMBRYON IC DEVELOPMEN TAL MORPHOMETRY AS A TOOL IN THE BIOSYSTEMATICS OF FOUR RHYN OCORIS SPECIES (HEMIPTERA: REDUVIIDAE: HARPACTORIN AE) V. JEBA SINGH, S. JESU RAJAN AND DUNSTON P. AMBROSE* Entomology Research Unit, St. Xavier’s College (Autonomous), Palayamkottai - 627 002, Tamil Nadu, India. email: eruxavier@gmail.com ABSTRACT Linear regression coefficient values (R) of postembryonic developmental morphometry of head, cephalic appendages, thorax, thoracic appendages and abdomen of life stages of four Rhynocoris species viz., R. fuscipes (F.), R. kumarii Ambrose and Livingstone, R. longifrons (Stål) and R. marginatus (F.) were analysed. Twenty one such computed values were analysed at two levels i.e., intraspecific and interspecific to find out the biosystematics utility, if any. The affinity was calculated by identifying exact or closely related values. The values were subjected to cluster analysis and a dendrogram was constructed and the similarity index was calculated. The characters analysed exhibited similarity among the four Rhynocoris species, unique characters in each species and closer affinity between R.kumarii and R. marginatus. This model study suggests the biosystematics utility value of morphometry as a tool at intraand interspecies levels and the observations are discussed. Key words: Linear regression coefficient values, postembryonic development morphometry, biosystematics tool, Rhynocoris Information regarding postembryonic developmental characteristics of insects has been used as a tool in the biosystematics of insects (Daly, 1985 and Rohlf, 1990). Ambrose and Ambrose (2003) studied the linear regression coefficient (r) values of morphometry of various parts of life stages of thirty species of reduviids belonging to three major subfamilies namely Harpactorinae, Reduviinae and Peiratinae to explore the possibilities of utilising these values as a tool in the biosystematics of Reduviidae. Ambrose and Ambrose (2009) analysed 36 morphometric indices belonging to 27 species, 14 genera and 3 subfamilies viz., Harpactorinae, Peiratinae and Reduviinae by direct observation as well as unweighted pair group method using arithmetic mean (UPGMA) incorporating * Corresponding author Euclidean distances, Nei and Li’s genetic distance coefficient and Jaccard’s coefficient reveals diagnostic intra- as well as intersubfamilial and generic affinities. Moreover, it gives an insight into the placement of genera in the existing divisions (tribes) of subfamilies and their phylogenetic relationship. Further, it clearly suggests a two diversified lines of evolution of Peiratinae and Reduviinae from Harpactorinae than the earlier suggested straight line evolution of these two subfamilies from Harpactorinae. The present investigation explore the biosystematics utility value of linear regression coefficient values (r) of postembryonic developmental morphometry of four species of a harpactorinae reduviid genus Rhynocoris. 124 MATERIALS AND METHODS MTL), 18. Prothoracic length/ Hind tibial length (PTL/ HTL), 19. Prothoracic length/ Abdominal The linear regression coefficient (r) values length (PTL/ AL), 20. Prothoracic length/ on the morphometry of life stages (I nymphal Abdominal width (PTL/ AW) and 21. Abdominal instar to adult) of four Rhynocoris species length / Abdominal width (AL/AW) (Rukmani, namely, R. fuscipes (F.), R. kumarii Ambrose and 1992; Das, 1996) (Table 1a and b). Livingstone, R. longifrons (Stål) and R. Cluster analysis was made using the marginatus (F.) were calculated from the morphometry data retrieved from the literature software in A MultiVariate Statistical Package (Ambrose, 1987; 1996; 1999) and analysed from for Windows, ver. 3.1. A dendrogram was constructed with Unweighted Pair Group Method current work. with Arithmetic Mean (UPGMA) clustering and The measurement of one body part (a) was the similarity matrix index was calculated by the compared to that of another (b) from the first per cent similarity coefficient (Kovach, 2007) nymphal instar to the adult. Thus six pairs of (I, (Fig. 1). II, III, IV, V nymphal instars and adult) (a) and RESULTS AND DISCUSSION (b) values were computed together and the regression coefficient (r) was calculated for a particular part. Equal number of males and 1. Head length/ Head width (HL/HW) The (r) values are exactly similar (0.99) females represented the adult measurement. Twenty one such sets of values were computed among three species R. kumarii, R. longifrons and the regression coefficient values were and R. marginatus, but slightly differs in R. analysed to find out the biosystematics fuscipes (0.97). significance, if any. Affinity was calculated by 2. Head length/ Prothoracic length (HL/PTL) identifying exact values or relatively closer Though the (r) values are exactly similar values. The analysed sets of values include: (0.83) in R. kumarii and R. marginatus but greatly 1. Head length/ Head width (HL/HW), 2. Head length/ Prothoracic length (HL/PTL), 3. Head length/ Abdominal length (HL/AL), 4. Head length/ Diameter of eye (HL/DE), 5. Head width/ Width between eyes (HW/WBE), 6. Head width/ Prothoracic width (HW/PTW), 7. Entire Antennal length/ Head length (EAL/HL), 8. Entire Antennal length/ Prothorax length (EAL/ PTL), 9. Entire Antennal length/Foretibial length (EAL/FTL), 10. Entire Antennal length/ Abdominal length (EAL/AL), 11. Rostral length/ Head length (RL/HL), 12. Rostral length/ Prothoracic length (RL/ PTL), 13. Rostral length/ Foretibial length (RL/ FTL), 14. Rostral length/ Abdominal length (RL/ AL), 15. Prothoracic length/ Prothoracic width (PTL/ PTW), 16. Prothoracic length/ Foretibial length (PTL/ FTL), 17. Prothoracic length/ Midtibial length (PTL/ it differs in R. fuscipes (0.76) and R. longifrons (0.93). 3. Head length/ Abdominal length (HL/AL) The (r) values are exactly similar in R. kumarii and R. marginatus (0.96) and are almost similar in R. fuscipes (0.87) and R. longifrons (0.86). 4. Head length/ Diameter of eye (HL/DE) The (r) values are exactly similar (0.99) in all the four species viz., R. fuscipes, R. kumarii, R. longifrons and R. marginatus. 5. Head width/ Width between eyes (HW/WBE) The (r) values are exactly similar (0.98) in R. kumarii, R. longifrons and R. marginatus but it is slightly higher in R. fuscipes (0.99). 125 6. Head width/ Prothoracic width (HW/PTW) 14. Rostral length/ Abdominal length (RL/ AL) The (r) values are similar in (0.98) R. fuscipes The (r) values are closer among R. fuscipes (0.88) and R. kumarii (0.86), but it much differs and R. kumarii but slightly greater in in R. longifrons (0.90) and R. marginatus (0.83). R.marginatus (0.99) and lesser in R. longifrons (0.97). 7. Entire Antennal length/ Head length (EAL/ HL) 15. Prothoracic length/ Prothoracic width The (r) values are similar in R. kumarii and (PTL/ PTW) R. marginatus (0.99) but it slightly differs in R. The (r) values are exactly similar (0.99) in longifrons (0.98) and R. fuscipes (0.96). all the four species viz., R. fuscipes, R. kumarii, 8. Entire Antennal length/ Prothorax length R. longifrons and R. marginatus (EAL/PTL) 16. Prothoracic length/ Fore tibial length The (r) values are exactly similar in R. (PTL/ FTL) fuscipes and R. kumarii (0.89) but it is lesser in The (r) values are closer among R. kumarii R. longifrons(0.88) and R. marginatus(0.86). (0.87) and R. marginatus (0.89) but greater in R. 9. Entire Antennal length/Foretibial length (EAL/FTL) fuscipes (0.94) and R. longifrons (0.92). 17. Prothoracic length/ Midtibial length (PTL/ The (r) values are similar in R. kumarii and MTL) R.marginatus (0.99) but it is lesser in R. fuscipes The (r) values are closer among R. kumarii (0.97) and R. longifrons (0.96). (0.87) and R. marginatus (0.85), but slightly 10. Entire Antennal length/ Abdominal length greater in R. longifrons (0.90) and much greater (EAL/AL) in R. fuscipes (0.94). The (r) values are similar (0.98) in R. kumarii 18. Prothoracic length/ Hind tibial length and R. longifrons but it is lesser in R. fuscipes (PTL/ HTL) (0.95) and R. marginatus (0.97). The (r) values are exactly similar (0.88) in 11. Rostral length/ Head length (RL/HL) R. kumarii and R. marginatus but slightly greater The (r) values are similar (0.98) in R. in R. fuscipes (0.90) and much greater in R. longifrons and R. marginatus slightly greater in longifrons (0.94). R. kumarii (0.99) but much lesser in R. fuscipes 19. Prothoracic length/ Abdominal length (0.92). (PTL/ AL) 12. Rostral length/ Prothoracic length (RL/ PTL) The (r) values are closer among in all the four species viz., R. fuscipes (0.96), R. kumarii (0.95), The (r) values are similar (0.89) in R. kumarii R. longifrons (0.93) and R. marginatus (0.94). and R. longifrons but it is much greater in R. 20. Prothoracic length/ Abdominal width fuscipes (0.94) and R. marginatus (0.91). (PTL/ AW) 13. Rostral length/ Foretibial length (RL/ FTL) The (r) values are exactly similar (0.98) in The (r) values are exactly similar (0.99) in all the four species viz., R. fuscipes, R. kumarii, R. kumarii and R. marginatus but much lesser in R. fuscipes (0.90) and R. longifrons (0.92). R. longifrons and R. marginatus. 126 21. Abdominal length / Abdominal width (AL/ Closer (r) values AW) 1. R. fuscipes and R. kumarii have one closer (r) The (r) values are exactly similar (0.98) in values i.e., in Head width/ Prothorax width (HW/ R. kumarii and R. longifrons but slightly lesser PTW). in R. fuscipes (0.96) and greater in R. marginatus 2. R. fuscipes, and R. longifrons have five closer (0.99). (r) values i.e., Head length/ Abdominal length Exactly similar (r) values (HL/AL), Entire Antennal length/ Head length (EAL/HL), Entire Antennal length/Fore tibial 1. All the four species of Rhynocoris viz., R. length (EAL/FTL), Prothoracic length/ Hind fuscipes, R. kumarii, R. longifrons and R. tibial length (PTL/ HTL) and Prothoracic length/ marginatus have 3 similar (r) values i.e., in Head Abdominal width (PTL/ AW). length/ Diameter of eye (HL/DE), Rostral length/ Fore- tibial length (RL/ FTL) and Prothoracic 3. R. fuscipes and R. marginatus have 3 closer length/ Prothoracic width (PTL/ PTW). Hence, (r) values i.e., Entire Antennal Length/ these values could be considered as generic Abdominal length (EAL/AL), Rostral length/ markers. Prothoracic length (RL/ PTL) and Abdominal length / Abdominal width (AL/AW). 2. R. fuscipes and R. kumarii have 2 similar (r) values i.e., Entire Antennal length/ Prothorax 4. R. fuscipes, R. kumarii, R. longifrons and R. length (EAL/PTL) and Rostral length/ marginatus have 3 closer (r) values i.e., Abdominal length (RL/ AL). Prothoracic length/ Abdominal length (PTL/ AL), Prothoracic length/ Foretibial length (PTL/ FTL) 3. R. kumarii, and R. longifrons have 3 similar and Prothoracic length/ Midtibial length (PTL/ (r) values i.e., Entire Antennal length/ Abdominal MTL). length (EAL/AL), Rostral length/ Prothoracic length (RL/ PTL) and Abdominal length / 5. R. longifrons and R. marginatus have 2 closer Abdominal width (AL/AW). (r) values i.e., Entire Antennal length/ Prothorax length (EAL/PTL) and Rostral length/ 4. R. kumarii and R. marginatus have 6 similar Abdominal length (RL/ AL). (r) values i.e., Head length/ Prothoracic length (HL/PTL), Head length/ Abdominal length (HL/ Cluster analysis AL), Entire Antennal length/ Head length (EAL/ The dendrogram (Fig.1) of linear regression HL), Entire Antennal length/Foretibial length coefficient values (r) of postembryonic (EAL/FTL), Prothoracic length/ Hind tibial developmental morphometry constructed with length (PTL/ HTL) and Prothoracic length/ UPGMA clustering revealed interspecific Abdominal width (PTL/ AW). relationships among four Rhynocoris species 5. R. kumarii, R. longifrons and R. marginatus with highest similarity in HL/DE, RL/ FTL and have 2 similar (r) values i.e., Head length/ Head PTL/PTW (100%); EAL/HL and AL/AW width (HL/HW) and Head width/ Width between (99.87%); HW/WBE and RL/AL (99.61%); eyes (HW/WBE). EAL/AL and RL/HL (99.35%); PTL/FTL and PTL/MTL (99.16 %); HW/PTW and EAL/PTL 6. R. longifrons and R. marginatus have one (98.71%) and HL/AL and PTL/AW (98.25%). similar (r) values i.e., Rostral length/ Head length (RL/HL). The analysis of linear regression coefficient values (r) of postembryonic developmental 127 morphometry of four Rhynocoris species can be used as a tool for generic identity and interspecific differentiation and affinity. For instance, three exactly similar (r) values viz., HL/ DE, RL/FTL and PTL/PTW could be considered as Rhynocoris generic markers. R. kumarii and R. marginatus are more closer with six similar values showing greater affinity among the four Rhynocoris species. From this group R. kumarii exhibits greater affinity to R. marginatus with six similar values. The affinity between R. kumarii and R. longifrons with three similar values is greater than that between R. fuscipes and R. kumarii with two similar values. Three species viz., R. kumarii, R. longifrons and R. marginatus share affinity among them with two similar values. Thus R. fuscipes distinguishes itself from the other three Rhynocoris species. R. longifrons and R. marginatus also have separate affinity with one similar value. R. fuscipes has unique RL/HL character and differs from the other three Rhynocoris species and R. fuscipes and R. longifrons also has unique HL/ PTL character and differs from the other two Rhynocoris species. CONCLUSION The analysis of linear regression coefficient values (r) of postembryonic developmental morphometry of four Rhynocoris species revealed that the following three characters HL/ DE, RL/FTL and PTL/PTW could be considered as Rhynocoris generic markers. Those characters confirmed by the dendrogram showed in 100 % similarity among the four Rhynocoris species. The morphometry showed greater affinity between R. kumarii and R. marginatus among the four Rhynocoris species. This affinity was also confirmed by dendrogram node of grouped characters in HL/AL and PTL/AW showed in 98.25% similarity in R. kumarii and R. marginatus (Fig. 1). The above said analysis of linear regression coefficient values (r) of postembryonic developmental morphometry suggests its utility as a biosystematics tool at generic and species levels. However, the sample size taken for the present study is inadequate. Hence, further studies with more number of species and genera from different subfamilies are imperative to realize the multidisciplinary facts of biosystematics with postembryonic developmental morphometry as a tool. Figure 1. Phylogenetic affinity among four Rhynocoris species based on postembryonic developmental morphometry regression coefficient (r) values analysed by UPGMA clustering method (per cent similarity coefficient). 128 Table 1a. Linear regression coefficient values (r) of postembryonic developmental morphometry of four Rhynocoris species (contd.). STAGE HL/HW HL/PTL HL/AL HL/DE HW/WBE HW/PTW EAL/HL EAL/PTL EAL/FTL EAL/AL R. fuscipes 0.97 0.76 0.87 0.99 0.99 0.88 0.96 0.89 0.97 0.95 R. kumarii 0.99 0.83 0.96 0.99 0.98 0.86 0.99 0.89 0.99 0.98 R. longifrons 0.99 0.93 0.86 0.99 0.98 0.90 0.98 0.88 0.96 0.98 R. marginatus 0.99 0.83 0.96 0.99 0.98 0.83 0.99 0.86 0.99 0.97 Table 1b. Linear regression coefficient values (r) of postembryonic developmental morphometry of four Rhynocoris species. STAGE RL/HL RL/PTL RL/FTL RL/AL PTL/PTW PTL/FTL PTL/MTL PTL/HTL PTL/AL PTL/AW AL/AW R. fuscipes 0.92 0.94 0.99 0.98 0.99 0.94 0.94 0.90 0.96 0.90 0.96 R. kumarii 0.99 0.89 0.99 0.98 0.99 0.87 0.87 0.88 0.95 0.98 0.98 R. longifrons 0.98 0.89 0.99 0.97 0.99 0.92 0.90 0.94 0.93 0.92 0.98 R. marginatus 0.98 0.91 0.99 0.99 0.99 0.89 0.85 0.88 0.94 0.98 0.99 129 ACKNOWLEDGEMENTS Ambrose, A.D. and Ambrose, D.P. 2003 Linear regression coefficient (r) of postembryonic developmental morphometry as a tool in the biosystematics of Reduviidae. (Insecta: Hemiptera). Shaspha, 10(1): 57-66. The authors are grateful to the authorities of St. Xavier’s College, Palayamkottai for facilities. One of us (DPA) thank Council of Scientific and Industrial Research (R.No.37(1310)/07/EMR-II) Ambrose, A.D. and Ambrose, D.P. 2009. Morphometric indices in the biosystematics of Reduviidae (Insecta: and University Grants Commission (F.No.33Hemiptera). Indian Journal of Entomology, 71(1): 330/2007(SR)) New Delhi for financial 18-28. assistance. REFERENCES Ambrose, D.P. 1987. Biological, behavioural and morphological tools in biosystematics of Reduviidae. (Insecta: Hemiptera). Proceedings of Indian Academy of Sciences (Animal Science), 96(5): 499-508. Ambrose, D.P. 1996. Biosystematics, distribution, diversity, population dynamics and biology of reduviids of Indian subcontinent - an overview. In: Biological and Cultural Control of Insect Pests, an Indian Scenario, (ed.) Ambrose, D.P., Adeline Publishers, Tirunelveli, India, pp. 93- 102. 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