INCIDENCE AND BIODIVERSITY OF RICELAND SPIDERS

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Indo-Am. J. of LifeSc & Bt., 2014 Rajendra Singh and B B Singh, 2014

INCIDENCE AND BIODIVERSITY OF RICELAND SPIDERS(ARTHROPODA : ARACHNIDA) IN NORTHEASTERN

UTTAR PRADESH, INDIA

B B Singh1 and Rajendra Singh2*

Spider samples were taken after planting the rice crop until harvesting at 15 days interval(DAT) at randomly selected 8 sites in four districts (Kushinagar, Deoria, Gorakhpur andMahrajganj) of northeastern Uttar Pradesh, India. A total of 13,303 individuals belongingto 58 species, 28 genera and 10 families were collected. Among them, 9 (53.3%), 11(33.6%), 35 (12.8%), and 3 (0.3%) species were most dominant, dominant, agrophile andrare, respectively. The most dominant species was Tetragnatha javana (7.23%) followedby Pardosa pseudoannulata (6.89%); Tetragnatha mandibulata (6.34%); Pardosa birmanica

(6.33%); Hippasa holmerae (5.70%); Tetragnatha maxillosa (5.46%); Oxyopes javanus (5.31%);Hippasa partita (5.05%); and Camaricus formosus (4.95%), Araneus ellipticus (4.89%),Clubiona japonicola (4.43%), Leucauge decorata (4.19%), Neoscona theisi (3.88%), Lycosa

mackenziei (3.86%), Plexippus paykulli (3.00%), Plexippus calcutaensis (2.52%), Plexippus

petersi (2.01%), Leucauge celebesiana (1.99%), Pardosa sumatrana (1.58%), and an araneidspecies (1.29%). Of the total catch, 30.9% were juveniles and proportion of males was0.72. Lycosidae and Tetragnathidae accounted for the largest population, eachrepresenting 29.85% and 27.95%, respectively. Among six foraging guilds, orb weabers(44.3%) formed the most dominant guild followed by ground runners (30.0%), stalkers(15.2%), foliage runners (5.3%), ambusers (5.1%) and space builder (0.1%). Differentecological indices were calculated at all 8 locations and 8 DATs and its consequenceswere discussed.

Keywords: Riceland, Spiders, Ecological indices, Biodiversity of spiders, Foraging guilds

*Corresponding Author: Rajendra Singh � [email protected]

INTRODUCTIONSpiders are potential biological control agentsin agroecosystems (Riechert, 1984; Barrion andLitsinger, 1995). Many workers have described

1 Department of Agricultural Zoology and Entomology, PG College, Itawah, UP.2 Department of Zoology, DDU Gorakhpur University, Gorakhpur-273009, UP, India.

Indo-Am. J. of LifeSc & Bt., 2014 ISSN 2347-2243 www.iajlb.com

Vol. 2, No. 1, February 2014

© 2014 IAJLB. All Rights Reserved

Research Paper

spider species abundance or its composition indifferent agroecosystems (Wisnieswka andProkopy, 1997; Rodrigues et al., 2009),quantitative observations on the abundance of

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spiders (Carroll and Hoyt, 1984; Sudhikumar etal., 2005a, b) or recorded spider predation events(Tahir and Butt, 2008; Chauhan et al., 2009). Arice (Oryza sativa Linn.) field is a complexagroecosystem, containing many aquatic, semi-aquatic, and terrestrial species. Spiders are wellrepresented among the many predators foundin this habitat (Barrion and Litsinger, 1994,1995). Numerous surveys of spiders have beenconducted in the rice growing regions of Asia(Heong et al., 1991, Misra and Srivastava, 1993;Barrion and Litsinger, 1995; Kim, 1995a, b;Barrion and Schoenly, 1999; Mukhtar, 2004;Sebastian et al., 2005). The spider fauna of therice fields in India has been studied by manyauthors in the different parts of the country(Anbalagan and Narayanaswamy, 1999; Pathakand Saha, 1999; Bhattacharya, 2000). However,it is a less common practice among workers tocompare spider abundance at different stages ofcrop growth with the exception of the work ofBanerji et al. (1993) and Sudhikumar et al.(2005a). There has been less study on the

seasonal variation of spiders and their ecologicalimpact. In this work, the data were presented tocompare the abundance and richness of spidersduring different stages of the crop growth.

MATERIALS AND METHODS

Site of InvestigationThe present investigation was carried out for aperiod of crop (kharif) seasons, 2008. Samplingwas conducted at the following randomly selected8 sites: 1. Padrauna (26° 53’ 44" n, 83° 58’ 21" E,84 m asl), 2. Ramkola (26° 54’ 09" N, 83° 50’ 31"E, 84 m asl) (District - Kushinagar); 3. Deoria(26° 30’ 46" N, 83° 48’ 60" E, 77 m asl), 4.Bhatparrani (26° 17’ 44" N, 84° 02’ 24" E, 70 masl) (District - Deoria); 5. Chaurichaura (26° 38’40" N, 83° 34’ 38" E, 78 m asl), 6. Pipraich (26°49’ 25" N, 83° 31’ 06" E, 84 m asl) (District -Gorakhpur); 7. Mahrajganj (27° 08’ 33" N, 83°34’ 15" E, 93 m asl) and 8. Partawal (26° 57’ 55"N, 83° 36’ 03" E, 89 m asl) (District - Mahrajganj)(Figure 1). Two districts Kushinagar and

Figure 1: Map of the Study Site (1-8) in 4 Districts of Northeast Uttar Pradesh(Courtesy www.mapofindia.com)

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Mahrajganj are adjacent and near the foot ofHimalayas with typical terai climate. Remainingtwo districts, Deoria and Gorakhpur are southto the above districts. All the districts are wellinundated by several rivers and riverines. Morethan 80% of the total annual rainfall is receivedduring the crop season, July to October.

Sampling MethodsSampling of spiders was done followingSudhikumar et al. (2005) every 15 Days AfterTransplantation (DAT) of crop from 4 quadrates(1 x 1 m) placed at four corners of 10 x 10 m areaby visual search method between 9.00 – 11.00a.m. A sufficient core area was left to avoid edgeeffects. All 4 quadrates were searched for a totalof one hour. Eight visits were made per site. Atotal of 32 quadrates were studied per site.Spiders were also collected from the groundstratum and from the terminals of plants.Specimens from each quadrate were preservedin 75% alcohol in the field and identified andcounted under a stereo-zoom microscope in thelaboratory. Each mature specimen that could notbe identified was included as a species, but itsgenus was not added in the total genera.

Spiders were classified as most dominantspecies (> 5.0% of the total population), dominant(1-5% of the total population), agrophile (0.1-1.0%of the total population) and rare (< 0.1% of thetotal population).

DATA ANALYSIS FOR DIVERSITYINDICESIn this study, the Shannon-Wiener diversityindex (H), which is sensitive to changes in theabundance of rare species in a community, wasapplied because it incorporated the speciesrichness and evenness and adapted to a simplestatistical analysis. In addition, Simpson index(l), which is sensitive to changes in the mostabundant species in a community, Margalefrichness index (R) and Pielou’s evenness index(E) of spider communities were also calculated

for a comparison. Characteristics of each indexare given below.

a. Shannon-Wiener Diversity Index (H):Historically, the Shannon-Wiener diversityindex has been used to measure the effects ofhabitat quality such as effects of pollutioneffluents. Recently, this index has fallen out offavor, because it does not take into accounthabitat specific parameters required by specificspecies. Though the results of the Shannon-Wiener index needs to be used with caution, itstill provides a good learning tool for comparingtwo distinct habitats. It combines twoquantifiable measures: the species richness(the number of species within the community)and the species equitability (how even are thenumbers of individual species). It is computedby using following equation: H = –Σpi ln pi, wherepi = the observed proportion of a particularspecies (Solow, 1993). A value near to zero wouldindicate that every species in the sample is thesame. A value near 4.6 would indicate that thenumber of individuals are evenly distributedbetween all the species. Values in the middleare ambiguous which is an obvious flaw of thisindex and, thus, care are taken when using thisindex.

b. Simpson Index (l) and Simpson’s DiversityIndex (D): Simpson’s diversity index (also knownas species diversity index) is often used toquantify the biodiversity of a habitat. It takesinto account the number of species present, aswell as the relative abundance of each species.The Simpson index represents the probabilitythat two randomly selected individuals in thehabitat will not belong to the same species. It iscomputed by using following equation: l = Σni (ni-1)/[N (N-1)], where ni = the number ofindividuals of species i, and N = Σni (Solow, 1993).The value of l ranges between 0 and 1. With thisindex, 0 represents infinite diversity and 1, nodiversity. That is, the bigger the value of l, thelower the diversity. This is neither intuitive norlogical, so to get over this problem, l is often

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subtracted from 1 to give Simpson’s index ofdiversity D = 1 – l. The value of this index alsoranges between 0 and 1, but now, the greaterthe value, the greater the sample diversity. Thismakes more sense. In this case, the indexrepresents the probability that two individualsrandomly selected from a sample will belong todifferent species.

c. Margalef Richness Index (R): This indexprovides a measure of species richness that isroughly normalized for sample size withoutusing more complex rarefaction techniques. Itis calculated by using following equation : R = N-1/In (n), where N = total number of species in acommunity, and n = total number of individualsobserved. The Margalef’s index of speciesrichness minimizes the effect of sample sizebias (Odum, 1971) as N and R are simple andeasy to calculate, but sensitive to sample size(Magurran, 1988). This index has been usedwith success in spider related studies, e.g.,Norris (1999).

d. Pielou’s Evenness Index (E): Pielou’sevenness is a diversity index, a measure ofbiodiversity which quantifies how equal thecommunity is numerically. The evenness of acommunity can be represented by the Pielou’sevenness index: E = H/Hmax, where H is thenumber derived from the Shannon diversityindex and Hmax is the maximum value of H, equalto: Hmax = - S [1/S.ln S] = ln S, where S is thetotal number of species. Thus : E = H/ln S, E isembarrassed between 0 and 1. The higher valueof E refers to the less variation in communities

between the species.

e. Tukey’s Test: The mean differences caused

by the two variables (locations and days of

transplantation of crop) were tested by using

Tukey’s “Honestly Significantly Different” (HSD)test which is based on what is called the

“studentized range distribution”. To test all

pairwise comparisons among means using theTukey HSD, computed t for each pair of means

using the formula: ts = (Mi-Mj)/(MSE/nh)0.5 where

Mi - Mj is the difference between the ith and jth

means, MSE is the Mean Square Error, and nh

is the harmonic mean of the sample sizes ofgroups i and j.

RESULTS

Species CompositionThe list of spiders collected from the rice fieldsin northeastern Uttar Pradesh and their relativeabundance is displayed in Table 1 while thedistributions of the spiders at different DAT (dataof locations were pooled) and at differentlocations (data of DAT were pooled) are shown inTables 2 and 3, respectively.

A total of 13,303 individuals belonging to 58species, 28 genera and 10 families were collectedduring the study period, 2008 (Table 1). Of the totalspecies, 9 species were most dominant (accountedfor 53.3% of the total population), 11 species weredominant (accounted for 33.6% of the totalpopulation), 35 species were agrophile (accountedfor 12.8% of the total population), and 3 specieswere rare (accounted for 0.3% of the totalpopulation). The most dominant species of overalldata were Tetragnatha javana (Thorell) (7.23%);Pardosa pseudoannulata (Bösenberg and Strand)(6.89%); Tetragnatha mandibulata Walckenaer(6.34%); Pardosa birmanica Simon (6.33%); Hippasaholmerae Thorell (5.70%); Tetragnatha maxillosaThorell (5.46%); Oxyopes javanus Thorell (5.31%);Hippasa partita (OP-Cambridge) (5.05%); andCamaricus formosus Thorell (4.95%). Next 11species, viz., Araneus ellipticus (Tikader and Bal)(4.89%), Clubiona japonicola Boesenberg and Strand(4.43%), Leucauge decorata (Blackwall) (4.19%),Neoscona theisi (Walckenaer) (3.88%), Lycosamackenziei Gravely (3.86%), Plexippus paykulli(Audouin) (3.00%), Plexippus calcutaensis (Tikader)(2.52%), Plexippus petersi (Karsch) (2.01%), Leucaugecelebesiana (Walckenaer) (1.99%), Pardosasumatrana (Thorell) (1.58%), and an unidentifiedaraineid species (1.29%) collectively constituteabout 87% of the individuals collected from rice

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Table 1: List of Spiders Collected From the Riceland in NortheasternUttar Pradesh and Their Relative Abundance

Family/Species No. of Individuals

1. Araneidae (Orb weavers) 2172

1. Araneus ellipticus (Tikader and Bal, 1981) 651

2. Araneus mitificus (Simon, 1886) 126

3. Araneus sp. A 30

4. Araneidae sp. A. 23

5. Araneidae sp. B. 172

6. Argiope aemula (Walckenaer, 1842) 35

7. Argiope catenulata (Doleschall, 1859) 48

8. Cyclosa bifida (Doleschall, 1859) 112

9. Cyclosa mulmeinensis (Thorell, 1887) 36

10. Cyrtophora citricola (Forskål, 1775) 31

11. Eriovixia excelsa (Simon, 1889) 36

12. Eriovixia laglaizei (Simon, 1877) 48

13. Gasteracantha diadesmia Thorell, 1887 37

14. Gasteracantha kuhlii C.L. Koch, 1837 22

15. Gea subarmata Thorell, 1890 58

16. Larinia phthisica (L. Koch, 1871) 22

17. Neoscona molemensis Tikader and Bal, 1981 41

18. Neoscona nautica (L. Koch, 1875) 36

19. Neoscona theisi (Walckenaer, 1842) 516

20. Nephilengys malabarensis (Walckenaer, 1842) 46

21. Parawixia dehaanii (Doleschall, 1859) 34

22. Poltys illepidus C. L. Koch, 1843 12

2. Clubionidae (Foliage runners) 669

23. Clubiona drassodes O.P.-Cambridge, 1874 29

24. Clubiona japonicola Boesenberg and Strand, 1906 589

25. Clubiona sp. A. 51

3. Gnaphosidae (Ground runners) 25

26. Urozelotes rusticus (L. Koch, 1872) 15

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Table 1 (Cont.)

27. Gnaphosidae sp. A. 10

4. Lycosidae (Ground runners) 3971

28. Hippasa holmerae Thorell, 1895 758

29. Hippasa partita (O.P.-Cambridge, 1876) 672

30. Lycosa mackenziei Gravely, 1924 513

31. Lycosa sp. A. 26

32. Pardosa birmanica Simon, 1884 842

33. Pardosa pseudoannulata (Bösenberg and Strand, 1906) 916

34. Pardosa sp. A 34

35. Pardosa sumatrana (Thorell, 1890) 210

5. Oxyopidae (Stalkers) 725

36. Oxyopes javanus Thorell, 1887 707

37. Oxyopes sp. A. 18

6. Pholcidae (Space builders) 12

38. Pholcus phalangioides (Fuesslin, 1775) 12

7. Salticidae (Stalkers) 1296

39. Harmochirus brachiatus (Thorell, 1977) 64

40. Hasarius adansoni (Audouin, 1826) 93

41. Plexippus calcutaensis (Tikader, 1974) 335

42. Plexippus paykulli (Audouin, 1826) 399

43. Plexippus petersi (Karsch, 1878) 268

44. Myrmarachne sp. A. 76

45. Myrmarachne sp. B. 43

46. Phintella sp. 18

8. Sparassidae (Foliage runners) 34

47. Heteropoda venatoria (Linnaeus, 1767) 34

9. Tetragnathidae (Orb weavers) 3718

48. Leucauge celebesiana (Walckenaer, 1842) 265

49. Leucauge decorata (Blackwall, 1864) 558

50. Tetragnatha javana (Thorell, 1890) 962

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Table 1 (Cont.)

51. Tetragnatha mandibulata Walckenaer, 1842 844

52. Tetragnatha maxillosa Thorell, 1895 727

53. Tetragnatha sp. A 45

54. Tetragnatha sp. B. 109

55. Tetragnatha sp. C. 117

56. Tetragnathidae sp. D. 91

10. Thomisidae (Ambushers) 681

57. Camaricus formosus Thorell, 1887 659

58. Thomisidae sp. A. 22

Total 13303

Table 2: Number of Individuals Collected from Rice-Agroecosystem FromNortheastern Uttar Pradesh at Different Days of Transplantation (DAT)

of Crop Growth (Data of All Locations Pooled)

Species

Days after transplantation (DAT) Total

15 30 45 60 75 90 105 120

Araneidae species A. 0 0 1 2 3 5 8 4 23

Araneidae species B. 0 5 15 22 54 47 21 8 172

Araneus ellipticus 7 38 67 128 157 102 110 42 651

Araneus mitificus 9 11 17 23 31 19 12 4 126

Araneus sp. A 0 0 1 1 5 8 9 6 30

Argiope aemula 0 0 1 4 9 12 5 4 35

Argiope catenulata 0 0 0 2 8 11 14 13 48

Camaricus formosus 12 37 58 112 154 165 87 34 659

Clubiona drassodes 0 0 1 1 5 8 12 2 29

Clubiona japonicola 9 14 56 114 128 126 98 44 589

Clubiona sp. A. 2 5 4 8 6 12 9 5 51

Cyclosa bifida 2 7 9 13 18 28 21 14 112

Cyclosa mulmeinensis 1 0 1 4 5 7 9 9 36

Cyrtophora citricola 0 0 0 2 4 4 12 9 31

Eriovixia excelsa 0 0 2 8 14 4 5 3 36

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Table 2 (Cont.)

Species


15 30 45 60 75 90 105 120

Eriovixia laglaizei 1 1 0 2 8 10 15 11 48

Gasteracantha diadesmia 0 1 2 4 8 7 6 9 37

Gasteracantha kuhlii 0 0 1 1 1 6 10 3 22

Gea subarmata 0 0 0 2 9 15 18 14 58

Gnaphosidae species A. 0 0 0 1 4 3 1 1 10

Harmochirus brachiatus 0 0 1 5 8 14 21 15 64

Hasarius adansoni 1 3 5 11 14 27 19 13 93

Heteropoda venatoria 0 0 0 2 5 11 11 5 34

Hippasa holmerae 12 32 83 118 162 198 110 43 758

Hippasa partita 3 28 54 124 138 182 108 35 672

Larinia phthisica 0 0 1 0 2 5 9 5 22

Leucauge celebesiana 9 15 26 40 64 93 12 6 265

Leucauge decorata 12 19 42 94 116 137 85 53 558

Lycosa mackenziei 11 18 44 54 103 117 84 82 513

Lycosa sp. A. 0 0 0 0 4 12 5 5 26

Myrmarachne sp. A. 1 2 4 9 18 17 20 5 76

Myrmarachne sp. B. 0 0 2 3 8 14 14 2 43

Neoscona molemensis 1 1 0 5 6 8 11 9 41

Neoscona nautica 0 0 1 3 8 9 9 6 36

Neoscona theisi 9 14 29 48 91 86 142 97 516

Nephilengys malabarensis 0 0 1 5 4 12 19 5 46

Oxyopes javanus 20 32 74 136 178 142 101 24 707

Oxyopes sp. A. 1 2 5 7 2 1 0 0 18

Parawixia dehaanii 0 0 1 4 7 10 8 4 34

Pardosa birmanica 12 19 62 113 154 216 205 61 842

Pardosa pseudoannulata 13 21 84 115 243 274 117 49 916

Pardosa sp. A 0 0 1 3 5 7 14 4 34

Pardosa sumatrana 3 14 16 27 55 42 45 8 210

Phintella sp. 1 1 2 2 4 5 3 0 18

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Table 2 (Cont.)

Species


15 30 45 60 75 90 105 120

Pholcus phalangioides 0 1 2 1 4 2 2 0 12

Plexippus calcutaensis 11 18 34 41 92 44 64 31 335

Plexippus paykulli 15 24 31 48 65 78 98 40 399

Plexippus petersi 9 18 29 57 71 53 19 12 268

Poltys illepidus 0 0 1 2 2 4 1 2 12

Tetragnatha javana 12 37 110 178 247 219 105 54 962

Tetragnatha mandibulata 15 24 34 95 149 251 197 79 844

Tetragnatha maxillosa 9 14 57 125 184 197 93 48 727

Tetragnatha sp. A 0 0 0 0 6 18 14 7 45

Tetragnatha sp. B. 2 5 8 11 22 34 18 9 109

Tetragnatha sp. C. 3 8 11 23 27 16 18 11 117

Tetragnathidae sp. D. 0 0 1 10 16 29 18 17 91

Thomisidae sp. A. 0 0 0 2 6 5 4 5 22

Urozelotes rusticus 0 1 1 2 3 4 3 1 15

Total 228 490 1093 1977 2924 3192 2308 1091 13303

Table 3: Number of Individuals of Spiders Collected From Rice-lands From NortheasternUttar Pradesh at Different Locations (1. Padrauna, 2. Ramkola, 3. Deoria, 4. Bhatparrani,

5. Chaurichaura, 6. Pipraich, 7. Mahrajganj and 8. Partawal) (data of days ofTransplantation (DAT) of Crop Growth Pooled)

Species

Locations Total

1 2 3 4 5 6 7 8

Araneidae species A. 5 1 4 5 5 1 1 1 23

Araneidae species B. 11 20 31 33 31 20 17 9 172

Araneus ellipticus 48 88 110 122 100 87 67 29 651

Araneus mitificus 14 24 27 23 24 14 0 0 126

Araneus sp. A 0 6 5 4 7 5 3 0 30

Argiope aemula 0 3 8 7 8 7 2 0 35

Argiope catenulata 6 10 4 9 6 8 4 1 48

Camaricus formosus 58 105 102 128 88 80 58 40 659

Clubiona drassodes 0 6 6 6 5 6 0 0 29

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Table 3 (Cont.)

Species

Locations Total

1 2 3 4 5 6 7 8

Clubiona japonicola 35 97 80 104 111 68 58 36 589

Clubiona sp. A. 8 9 13 6 9 4 2 0 51

Cyclosa bifida 4 22 18 19 21 17 11 0 112

Cyclosa mulmeinensis 6 6 10 4 6 4 0 0 36

Cyrtophora citricola 3 3 7 5 7 5 1 0 31

Eriovixia excelsa 0 9 8 9 4 6 0 0 36

Eriovixia laglaizei 1 5 9 7 8 7 7 4 48

Gasteracantha diadesmia 0 7 10 9 8 2 1 0 37

Gasteracantha kuhlii 0 7 6 4 4 1 0 0 22

Gea subarmata 1 9 13 17 8 6 4 0 58

Gnaphosidae species A. 3 2 1 0 0 3 1 0 10

Harmochirus brachiatus 7 6 12 13 11 8 5 2 64

Hasarius adansoni 11 16 24 15 15 10 2 0 93

Heteropoda venatoria 0 2 10 7 5 7 1 2 34

Hippasa holmerae 73 108 124 146 116 95 62 34 758

Hippasa partita 52 84 139 98 103 93 67 36 672

Larinia phthisica 2 4 5 6 3 2 0 0 22

Leucauge celebesiana 14 35 42 58 39 36 25 16 265

Leucauge decorata 28 72 94 111 92 79 50 32 558

Lycosa mackenziei 38 92 109 98 71 47 44 14 513

Lycosa sp. A. 3 3 4 4 4 4 4 0 26

Myrmarachne sp. A. 8 14 13 14 14 10 3 0 76

Myrmarachne sp. B. 0 8 8 9 8 8 2 0 43

Neoscona molemensis 8 10 6 9 6 2 0 0 41

Neoscona nautica 6 6 7 9 5 3 0 0 36

Neoscona theisi 42 80 118 104 77 51 39 5 516

Nephilengys malabarensis 3 7 12 11 7 6 0 0 46

Oxyopes javanus 47 99 104 101 89 101 116 50 707

Oxyopes sp. A. 1 9 5 3 0 0 0 0 18

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Table 3 (Cont.)

Species

Locations Total

1 2 3 4 5 6 7 8

Parawixia dehaanii 3 5 4 6 6 4 6 0 34

Pardosa birmanica 71 132 145 144 124 124 68 34 842

Pardosa pseudoannulata 100 213 145 128 111 82 83 54 916

Pardosa sp. A 5 8 9 6 5 1 0 0 34

Pardosa sumatrana 9 26 34 35 36 44 23 3 210

Phintella sp. 6 4 0 2 3 2 0 1 18

Pholcus phalangioides 4 6 0 1 1 0 0 0 12

Plexippus calcutaensis 19 45 59 41 48 47 43 33 335

Plexippus paykulli 20 50 87 83 71 56 24 8 399

Plexippus petersi 12 39 49 58 49 34 18 9 268

Poltys illepidus 4 5 1 1 1 0 0 0 12

Tetragnatha javana 76 122 135 149 156 108 108 108 962

Tetragnatha mandibulata 69 99 123 134 126 102 100 91 844

Tetragnatha maxillosa 36 101 114 123 98 105 102 48 727

Tetragnatha sp. A 5 6 7 9 6 6 6 0 45

Tetragnatha sp. B. 10 16 23 15 17 19 9 0 109

Tetragnatha sp. C. 8 14 19 23 25 16 12 0 117

Tetragnathidae sp. D. 9 13 13 15 10 18 7 6 91

Thomisidae sp. A. 5 4 6 5 2 0 0 0 22

Urozelotes rusticus 0 11 3 0 1 0 0 0 15

Total 1017 2013 2284 2315 2021 1681 1266 706 13303

fields of northeastern Uttar Pradesh. Rest of the38 species represents only 13% of the collectedindividuals. Of the total catch, 30.9% werejuveniles (4111 individuals) and sex ratio(proportion of males in the population) was 0.72,i.e., 72% of the adults were males (6618individuals).

The family Pholcidae and Sparassidae arecomposed of single species each. FamilyLycosidae and Tetragnathidae accounted for the

largest population of the species of spiders, eachrepresenting 29.85% and 27.95% of all thespecies, respectively, followed by Araneidae(16.33%) and Salticidae (9.74%). The above 4families constituted 83.87% of the totalcatchments (13,303 individuals). The rest of thesix families are poorly represented (Oxyopidae –5.4%); Thomiicidae – 5.1%; Clubionidae – 5.0%;Sparassidae – 0.3%; Gnaphocidae – 0.2%;Pholcidae - 0.1%).

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Foraging GuildsThe collected spiders were grouped into foragingguilds according to Utez et al. (1999). Theseguilds were orb weabers (Araneidae andTetragnathidae), stalkers (Oxyopidae andSalticidae), ground runners (Lycosidae,Gnaphosidae), foliage runners (Clubionidae,Sparassidae), space builders (Pholcidae), andambushers (Thomisidae). Orb weabers (44.3%)formed the most dominant guild followed byground runners (30.0%). Stalkers (15.2%), foliagerunners (5.3%) and ambushers (5.1%) were lesscommon while very few specimens of spacebuilders (0.1%) were caught in the study area.

Table 4 displays the data of foraging guilds ofspiders in rice fields of northeastern UttarPradesh at different DAT of crop growth whendata of all locations were pooled. It demonstratedthat stalkers reached the peak population after75 DAT of crop while other kinds of foragersattained the peak population during 90 DAT ofcrop growth. Figure 2 illustrated the relativenumber of different kinds of foragers at differentDAT of crop. The data of all locations were pooled.

Likewise, Table 5 displays the data of foragingguilds of spiders in rice fields of northeasternUttar Pradesh at different locations when dataof all DAT of crop growth were pooled. Itdemonstrated that orb weabers, ground runnersand stalkers were more dominant at location 3and 4 (district Deoria) followed by location 5(district Gorakhpur) than other places. Figure 3illustrated the relative number of different kindsof foragers at various locations when the DAT ofcrop were pooled.

Diversity, Evenness and RichnessIndicesFrom the data displayed in Tables 1 and 2, 4ecological indices, viz., Shannon-Weinerdiversity index (H), Simpson diversity index (D),Margalef richness index (R) and Pielou evennessindex (E) were calculated to observe the diversity,richness and evenness of the species of spiders

in the target area in the fields of rice (Tables 6and 7).

a. Shannon-Wiener Diversity Index (H):Shannon-Wiener index provides a good learningtool for comparing two distinct habitats. Itcombines two quantifiable measures: thespecies richness (the number of species withinthe community) and the species equitability (howeven are the numbers of individual species). Avalue near zero indicate no diversity in thespecies in the samples while a value near 4.6indicate that the number of individuals areevenly distributed between all the species.

Table 8 demonstrates the values of Shannon-Weiner diversity indices of spiders collected atdifferent locations (8 locations) at different DAT ofcrop growth. Most of the values (83%) rangedbetween 2.5 to 3.5 which demonstrated that everyspecies in the sample is not the same, butindicated that the number of individuals aresomewhat evenly distributed between all thespecies. The data was analyzed by using 2-wayANOVA. Results showed a non-significantvariation in the values of Shannon-Weinerdiversity indices caused by either due to DAT (F7,

49 = 2.60, not significant) or locations (F7, 49 = 1.64,not significant). However, the results of Tukey’stest showed that the diversity of spiders wassignificantly different in 4 locations (5, 6, 7, 8) fromsite 1. It implies that the diversity of species ofspiders in northern part of study site (Kushinagarand Mahrajganj) is somewhat different from thesouthern part (Deoria and Gorakhpur). Thediversity of spiders in the samples collected atdifferent days of transplantation of crop was alsosame for the 15-90 DAT of crop growth. However,during the maturing of crop, the diversitydecreases (Table 8).

b. Simpson Diversity Index (D): Simpson’sdiversity index (D) is calculated by substractingSimpson index (l) from 1, i.e., D = 1 – l, and isusually used to quantify the biodiversity of ahabitat. It takes into account the number of

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Table 4: Foraging Guilds of Spiders in Rice Fields of Northeastern Uttar Pradeshat Different Days After Transplantation (DAT) (Data of All Locations Were Pooled)

DAT Orbweavers Stalkers Ground Runners Foliage Runners Space Builders Ambushers Total

15 92 59 54 11 0 12 228

30 200 100 133 19 1 37 490

45 440 187 345 61 2 58 1093

60 861 319 557 125 1 114 1977

75 1285 460 871 144 4 160 2924

90 1413 395 1055 157 2 170 3192

105 1034 359 692 130 2 91 2308

Table 5: Foraging Guilds of Spiders in Rice Fields of Northeastern Uttar Pradesh at DifferentLocations (1. Padrauna, 2. Ramkola, 3. Deoria, 4. Bhatparrani, 5. Chaurichaura, 6. Pipraich,

7. Mahrajganj and 8. Partawal) (Data of Days After Transplantation (DAT) Were Pooled)

Locations Orb Stalkers Ground Foliage Space Ambushers TotalWeavers `Runners Runners Builders

1 422 131 352 48 4 60 1017

2 812 290 676 120 6 109 2013

3 1000 361 708 108 0 107 2284

4 1060 339 659 122 1 134 2315

5 919 308 572 130 1 91 2021

6 748 276 496 79 0 82 1681

7 577 213 358 60 0 58 1266

8 352 103 175 36 0 40 706

Total 5890 2021 3996 703 12 681 13303

species present, as well as the relative

abundance of each species. The value of D

ranges between 0 and 1. With this index, 1

represents infinite diversity and 0, no diversity,

i.e., the greater the value, the greater the

sample diversity. In this case, the index

represents the probability that two individuals

randomly selected from a sample will belong to

different species.

Table 9 displays the values of Simpsondiversity indices for all locations and all days of

transplantation of crop. Its values rangedbetween 0.741 to 0.999. The 2-way ANOVA didnot yield any significant variation in the indiceswhen the samples were taken from differentlocations (F7,49= 1.275) or different days oftransplantation of crop (F7, 49= 1.104). It showedthat the diversity of spider species with referenceto their abundance is greater in thenortheastern Uttar Pradesh in rice fields and ineach sample, the probability that two individualsselected randomly will belong to different speciesis very high.

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Table 6: Parameters and Indices of Spider Community Observed in Riceland Ecosystemat Different Days of Transplantation (DAT) of Crop Growth (Data of All Locations Pooled)

(N: Number of Individuals, S: Number of Species, H: Shannon Index, Ë: Simpson Index,D: Simpson’s Index of Diversity, R: Margalef Richness Index, E: Pielou’s Evenness Index,

SR: Sex Ratio (Proportion of Male), JR: Juvenile Ratio (Proportion of Juveniles))

DAT N S H Ë D R E SR JR

15 228 31 3.316 0.049 0.951 5.526 0.900 0.110 0.075

30 490 34 3.345 0.049 0.951 5.327 0.893 0.839 0.041

45 1093 48 3.287 0.053 0.947 6.717 0.810 0.866 0.142

60 1977 55 3.321 0.134 0.866 7.115 0.802 0.759 0.303

75 2924 58 3.392 0.048 0.952 7.142 0.812 0.735 0.315

90 3192 58 3.428 0.048 0.952 7.065 0.820 0.703 0.367

105 2308 58 3.563 0.044 0.956 7.360 0.841 0.687 0.340

120 1091 58 3.711 0.042 0.958 8.149 0.852 0.660 0.408

Total 13303 58 3.420 0.045 0.955 6.003 0.828 0.720 0.309

Table 7: Parameters and Indices of Spider Community Observed in Riceland Ecosystemat Different Locations in Northeastern Uttar Pradesh (Data of Days of Transplantation

(DAT) of Crop Growth Pooled). (N: Number of Individuals, S: Number of Species,H: Shannon Index, Ë: Simpson Index, D: Simpson’s Index of Diversity, R: MargalefRichness Index, E: Pielou’s Evenness Index, SR: Sex Ratio (Proportion of Male),

JR: Juvenile Ratio (Proportion of Juveniles)]

DAT N S H Ë D R E SR JR

1 1017 49 3.314 0.049 0.951 6.932 0.851 0.630 0.298

2 2013 58 3.384 0.046 0.954 7.493 0.834 0.730 0.341

3 2284 56 3.409 0.042 0.958 7.112 0.847 0.875 0.328

4 2315 56 3.384 0.043 0.957 7.099 0.841 0.846 0.344

5 2021 56 3.385 0.043 0.957 7.226 0.841 0.785 0.387

6 1681 53 3.347 0.044 0.956 7.001 0.843 0.714 0.352

7 1266 42 3.123 0.055 0.945 5.739 0.835 0.682 0.382

8 706 27 2.806 0.076 0.924 3.964 0.851 0.648 0.341

Total 13303 58 3.364 0.045 0.955 6.003 0.828 0.720 0.309

c. Margalef Richness Index (R): Margalefrichness index (R) provides a measure of speciesrichness that is roughly normalized for samplesize without using more complex rarefactiontechniques. Table 10 displays the variations inthe R in the samples taken from different sites

and time (DAT). Most of the data (95%) rangedbetween 2.5 to 9.59. Two-way ANOVA revealedsignificant effect on R of different localities (F7,

49 = 2.327, P < 0.05) and days of transplantationof crop growth (F7, 49 = 2.975, P < 0.05). Itdemonstrated that the species richness of the

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Table 8: Shannon-Wiener Index of Spider Community Observed in Ricel and Ecosystem atDifferent Days of Transplantation (DAT) of Crop Growth at Different Locations

DAT Locations

1 2 3 4 5 6 7 8 Mean±SD

15 2.885 3.065 3.056 3.144 3.131 3.195 3.323 2.885 3.123±0.127b

30 3.046 3.269 3.190 3.228 3.244 3.336 3.384 3.046 3.278±0.143b

45 2.906 3.195 3.183 3.192 3.337 3.381 3.450 2.906 3.253±0.173b

60 2.837 3.010 3.097 3.210 3.345 3.380 3.412 2.837 3.210±0.211b

75 2.536 2.915 2.952 2.685 3.266 3.354 3.412 2.536 3.046±0.324b

90 0.732 2.483 2.836 2.481 3.257 3.145 3.357 0.732 2.688± 0.861ab

105 1.931 2.039 2.657 2.107 2.952 2.967 3.078 1.931 2.596± 0.491ab

120 1.993 0.939 2.042 1.474 2.628 2.599 2.714 1.993 2.102±0.629a

Mean 2.358 2.614± 2.877± 2.690± 3.145± 3.170± 3.266± 3.175± 2.912±±SD ±0.781a 0.790ab 0.383ab 0.642ab 0.245b 0.272b 0.251b 0.336b 0.575

Table 8: Shannon-Wiener Index of Spider Community Observed in Ricel and Ecosystem atDifferent Days of Transplantation (DAT) of Crop Growth at Different Locations

DAT Locations

1 2 3 4 5 6 7 8 Mean±SD

15 2.885 3.065 3.056 3.144 3.131 3.195 3.323 2.885 3.123±0.127b

30 3.046 3.269 3.190 3.228 3.244 3.336 3.384 3.046 3.278±0.143b

45 2.906 3.195 3.183 3.192 3.337 3.381 3.450 2.906 3.253±0.173b

60 2.837 3.010 3.097 3.210 3.345 3.380 3.412 2.837 3.210±0.211b

75 2.536 2.915 2.952 2.685 3.266 3.354 3.412 2.536 3.046±0.324b

90 0.732 2.483 2.836 2.481 3.257 3.145 3.357 0.732 2.688± 0.861ab

105 1.931 2.039 2.657 2.107 2.952 2.967 3.078 1.931 2.596± 0.491ab

120 1.993 0.939 2.042 1.474 2.628 2.599 2.714 1.993 2.102±0.629a

Mean 2.358 2.614± 2.877± 2.690± 3.145± 3.170± 3.266± 3.175± 2.912±±SD ±0.781a 0.790ab 0.383ab 0.642ab 0.245b 0.272b 0.251b 0.336b 0.575

spiders varied with collection sites and time(DAT) in northeastern Uttar Pradesh. The Tukey’test revealed that the spider richness incollection sites 1, 2 and 3 are different to that ofsites 6, 7, and 8. Similarly the richness indiceswere greater up to 75 days of transplantation of

crop than later periods due to less availability ofpreys.

d. Pielou Evenness Index (E): Pileou evennessindex (E) is a measure of biodiversity whichquantifies how equal the community isnumerically. Its values ranged between 0 and 1.

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Table 9: Simpson’s Index of Diversity of Spider Community Observed in Riceland Ecosystemat Different Days of Transplantation (DAT) of Crop Growth at Different Locations

DAT Locations

1 2 3 4 5 6 7 8 Mean±SD

15 0.952 0.950 0.937 0.941 0.941 0.944 0.951 0.944 0.945±0.005b

30 0.948 0.956 0.999 0.947 0.944 0.949 0.953 0.961 0.957±0.018c

45 0.940 0.953 0.951 0.950 0.955 0.956 0.958 0.953 0.952±0.006c

60 0.936 0.945 0.947 0.951 0.956 0.955 0.957 0.956 0.950±0.007c

75 0.921 0.944 0.942 0.969 0.955 0.957 0.960 0.958 0.951±0.015c

90 0.778 0.917 0.940 0.970 0.957 0.956 0.958 0.959 0.929±0.063ab

105 0.882 0.880 0.931 0.974 0.941 0.940 0.948 0.957 0.932±0.034 ab

120 0.887 0.741 0.880 0.980 0.925 0.921 0.926 0.939 0.900±0.071a

Mean± 0.905± 0.911± 0.941± 0.960± 0.947± 0.947± 0.951± 0.953±SD 0.057a 0.073a 0.032ab 0.015c 0.011ab 0.012ab 0.011ab 0.008b 0.939±0.039

Table 10: Margalef Richness Indices of Spider Community Observed in Riceland Ecosystemat Different Days of Transplantation (Dat) of Crop Growth at Different Locations

DAT Locations

1 2 3 4 5 6 7 8 Mean±SD

15 5.525 6.188 6.581 7.384 7.300 7.442 8.116 7.222 6.970±0.822b

30 5.924 6.948 7.088 7.801 8.647 9.102 8.871 9.592 7.997±1.266b

45 5.037 5.968 6.040 6.543 7.556 8.325 8.754 8.767 7.124±1.424b

60 4.757 4.798 5.251 6.623 8.201 8.444 8.417 7.997 6.811±1.661b

75 3.970 4.877 4.494 6.093 7.495 8.395 8.627 7.814 6.471±1.853b

90 0.910 3.526 4.109 4.768 6.560 7.136 8.386 7.773 5.396±2.525ab

105 2.817 2.701 3.778 3.873 4.972 5.482 6.131 6.647 4.550±1.484ab

120 2.525 0.910 2.378 2.776 3.407 3.385 4.279 3.877 2.942±1.050a

Mean± 3.933± 4.490± 4.965± 5.733± 6.767± 7.214± 7.698± 7.461± 6.032±2.154SD 1.722a 2.011a 1.577ab 1.761a 1.756ab 1.906b 1.633b 1.70b

The higher value of E refers to the high evennessor less variation in communities between thespecies.

Table 11 displays the variations in the E inthe samples taken from different sites and time

(DAT) which ranged between 0.273 to 0.885. Two-way ANOVA revealed significant effect oflocations on E (F7, 49 = 3.455, P < 0.05) but did notyield significant effect of DAT of crop growth(F7, 49 = 1.325). It demonstrated that the evenness

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Table 11: Pielou Evenness Indices of Spider Community Observed in Riceland Ecosystemat Different Days of Transplantation (Dat) of Crop Growth at Different Locations

DAT Locations

1 2 3 4 5 6 7 8 Mean±SD

15 0.885 0.862 0.694 0.645 0.586 0.580 0.627 0.718 0.700±0.118b

30 0.820 0.757 0.611 0.560 0.529 0.542 0.589 0.705 0.639±0.108ab

45 0.732 0.681 0.601 0.550 0.536 0.541 0.581 0.643 0.608±0.071ab

60 0.750 0.657 0.581 0.545 0.538 0.538 0.574 0.644 0.603±0.075ab

75 0.719 0.646 0.577 0.455 0.532 0.542 0.589 0.620 0.585±0.080a

90 0.667 0.625 0.583 0.422 0.548 0.522 0.587 0.640 0.574±0.078a

105 0.777 0.612 0.590 0.371 0.524 0.508 0.555 0.651 0.574±0.118a

120 0.719 0.427 0.540 0.273 0.527 0.489 0.528 0.589 0.511±0.128a

Mean± 0.759± 0.658± 0.597± 0.477± 0.540± 0.533± 0.579± 0.651± 0.599±0.107SD 0.068c 0.125b 0.044b 0.120a 0.020a 0.027a 0.029b 0.042b

of spider communities varied with collectionsites in northeastern Uttar Pradesh. However,The Tukey’ test revealed that the evenness incollection sites 1 is significantly different fromall other sites while sites 2, 3, 7 and 8 haveequally even community and differed from sites4, 5 and 6.

Population GrowthThe population growth showed a gradual increasein the 30th and 45th DAT and reached the peakon 60th DAT and then showed a decline in the90th to 120th DAT. (Figure 3). The number ofspecies collected during the sampling showed agradual increase in number as the growth of the

Figure 2: Foraging Guilds of Spiders in RiceFields of Northeastern Uttar Pradesh at

Different Days After Transplantation (DAT)of Crop Growth (Data of all Locations

were Pooled)

Figure 3: Foraging Guilds of Spidersin Rice Fields of Northeastern Uttar Pradesh

at Different Locations (Data at DaysAfter Transplantation (DAT)of Crop Growth were Pooled)

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plants advanced and the maximum number of58 species was collected on the 30th DATsampling. The number of individuals alsoincreased as the crop growth advanced and themaximum number (3192 spiders) was collectedin the 90th DAT and at the site 4 (2315 spiders)(total number of spiders collected from all sites:13303). The spiders double its population eachfortnight since beginning upto 60 DAT, thereafterthe growth of the population slow down. The valueof the Shannon index also showed an gradualincrease except in the 60th DAT with an averageof 2.91 during the entire growth. But theSimpson index value registered an irregularityand the maximum value (0.96) was reached onthe 120th DAT and the minimum (0.90) on the15th DAT with an average of 0.94. The richnessindex value initially increased reaching its peakduring the 30th DAT (7.99) and thereafter,decreased up to 120 DAT (2.94). The value ofPielou’s evenness index showed more similarityin the 15th, 30th, 45th and 60th DAT than 75th, 90th

and 105th DAT.

DISCUSSIONTen spider families recorded from northeasternUttar Pradesh rice agroecosystem representabout one-sixth of the families reported from thecountry (Siliwal et al., 2005). The number offamilies found here is lower than the numberrecorded in rice fields elsewhere (Barrion andLitsinger, 1994, 1995; Sudhikumar et al., 2005a;Tahir and Butt, 2008) or for other biomessurveyed in India (Jose et al., 2006). Thenumbers of taxa recorded are generally lowerthan those reported for other surveys of riceecosystems. Barrion and Litsinger (1984)collected 13,270 specimens belonging to 51genera and 64 species under 16 families duringa 3-year study; Sudhikumar et al. (2005a)collected 17,717 individual spiders belonging to20 families, 64 genera and 94 species while, inPakistan, Tahir and Butt (2008) recorded 27658specimens representing 12 families, 30 generaand 44 species. In other studies on rice fields,

different number of species have been reported,such as 92 species from India (Sebastian et al.,2005), 60 species from Sri Lanka(Bambaradeniya and Edinisinghe, 2001), 44species from Texas (Marsha and Richard, 1976),40 species from Arkansas (Heiss and Meisch,1985), 28 species from California (Oraze et al.,1988), and 21 species from Korea (Okuma et al.,1978).

Lycosidae was the most dominant familyfollowed by Tetragnathidae. Similar results werereported in the studies of Settle et al. (1996),Sebastian et al. (2005) and Tahir and Butt (2008).Sudhikumar et al. (2005a) observed Tetragnathidaeas dominant families followed by Linyphiidaeand Lycosidae. Strangely, none of the specimenof the family Linyphiidae was observed innortheastern Uttar Pradesh while twounidentified species were reported fromPakistan (Tahir and Butt, 2008). The dominanceof these spiders in the rice ecosystem might beexpected as this wet habitat provides congenialconditions for these families (Sebastian et al.,2005). The phenological patterns of lycosidpopulations in the fields were similar to that ofIida and Fujisaki (2005, 2007), Huusela-Veistola(1998), Maelfait and De Keer (1990), andJalaluddin et al. (2000).

Although collection effort of present study wasextensive yet families Eresidae, Filistatidae,Linyphiidae, Miturgidae, Theridiidae andUloboridae recorded from south India were notrepresented in the present study.

The crop phenology and irrigation method and

patterns were similar at all collection sites. A

fewer number of spider species in rice ecosystem

than other crops such as wheat and maize (Rezac

et al., 2006) could be attributed to the practice of

monoculture prevailing in the study areas. Inaddition, the difference in quantity and quality

of spider fauna is also related to the time of the

collection and method of sampling (Tahir and

Butt, 2008). There are many environmental

82



factors like seasonality, spatial heterogeneity,

competition, predation, habitat type,

environmental stability and productivity that canaffect species diversity of spiders (Riechert and

Bishop, 1990; Kato et al. 1995; Rosenzweig, 1995).

The most common explanation for theobserved pattern of the spider guild structure

includes its structural diversity, microenvironment,

or the level of disturbance. Complex habitat

maintains diverse spider assemblage (Wagner

et al., 2003). The structural complexity (increase

in the number of tillers per hill in rice plant,more weeds and extended field margins) results

in an increase abundance and diversity of food

for spiders, which promote rapid population

growth, leading to elevated spider densities

(Wardle, 1995). It has been found that arable

fields are regularly recolonized from theperennial habitats (Schmidt and Tschamtke,

2005). Perennial habitats such as field

boundaries may provide food, refuge and over

wintering sites for many invertebrate species

including many natural enemies of major crop

pests, thus act as a source of dispersal to arablefields, which are frequently disturbed by different

management practices (Pfiffener and Wyss,

2004). Conventional management practices

such as tillage, burning and insecticide

application have numerous indirect effects on

the spider population. Insecticides can reducepopulations of phytophagus insects, which result

in less available prey for spiders (Amalin et al.,

2001; Fountain et al., 2007).

Studies of Russell-Smith (2002) establishedthe importance of rain fall in the regional spiderdiversity. In the tropics, a continuum of specieswith extended seasonal ranges has been found(Basset, 1991), which would give rise to variablesamples at different times of the year. Mostspiders are limited to a certain extent byenvironmental conditions. In general, differentspecies have varying humidity and temperaturepreferences and are limited to those seasons

which offer a microclimate within the range oftheir physiological tolerances. So the differencein species diversity between the DATs andlocations is likely to be due to the difference inthe amount of rainfall and temperature. Adiversity index incorporates both speciesrichness and evenness in a single value(Magurran, 1988). Diversity indices used hereare Shannon-Wiener index (H), which issensitive to changes in the abundance of rarespecies in a community, and Simpson index (D),which is sensitive to changes in the mostabundant species in a community. In thepresent study, the value of H increased as cropgrowth advanced. This indicates the presenceof some rare species in the spider communityas crop growth advanced. A higher value of D ascrop growth in the present study indicates thedominance of some spiders like tetragnathidsand lycosids in the initial period of crop growth.Emergence of new vegetation during Augustaltered the distribution of different life forms,which caused increase in richness during thismonth. After August abundance and diversity ofspiders continuously increased because ofincrease in crop foliage till maturity of rice crop(between first and second week of October). Adecline in abundance and diversity of spiderswas observed after milking stage till harvestingof the crop (after mid October to end ofNovember).

Species richness examines the number ofspecies occurring in a habitat. Overall speciesrichness is the most widely adopted diversitymeasure. However, since R depends on thesample size, it is limited as a comparative index.Hence, a number of indices have been proposedto measure species richness that isindependent of the sample size. They are basedon the relationship between R and total numberof individuals observed, n, which increases withincreasing sample size. When all species in asample are equally abundant an evenness indexwill be at its maximum, decreasing towards zero

83



as the relative abundance of the speciesdiverges away from evenness. Probably, the mostcommon evenness index used by ecologists isE. An evenness index should be independent ofthe number of species in the sample. It hasshown that the addition of a rare species to asample that contains only a few species greatlychange the value of E. Additionally, there aremany factors that determine the speciescomposition. This may be related to the changesin the vegetation structure of the habitat.Longback, Kajak (1965) found that relative spiderand prey densities were related to the structuraldiversity of the habitat, and Turnbull (1966)attributed similar relative predator and preydensities to environmental conditions operatingin both groups. According to Turnbull (1973),most webs have specific attachment and spacerequirements. Cherrett (1964) found that adultorb weavers in a grass land habitat needed avertical space of at least 25-30 cm2 for webplacements, a factor which strongly limited thosespiders to certain habitats. Other workers havealso found the availability of specific structuralfeatures to limit the habitats occupied by variousweb-builders (Duffey, 1962). Structurally complexcrops, providing a wider assortment of resources,would be predicted to support a more diversespider assemblage, thus increasing the chancesof the “best” match between spiders and insectpests. The results of this study also indicate theinfluence of vegetation structure on the diversityof resident spider community. The web buildingand plant wandering spiders rely on vegetationfor some part of their lives, either for findingfood, building retreats or for web building. Thestructure of the vegetation is, therefore,expected to influence the diversity of spidersfound in the habitat. Studies have demonstratedthat a correlation exists between the structuralcomplexity of habitat and species diversity (Uetz,1979; Andow, 1991). Uetz (1991) suggests thatstructurally more complex plants can support amore diverse spider community. Downie et al.

(1999) and New (1999) have demonstrated thatthe spiders are extremely sensitive to smallchanges in the habitat structure; includinghabitat complexity and microclimatecharacteristics. Thus the physical structure ofthe environments has an important influenceon the habitat preferences of spider speciesespecially web-building species (Hurd and Fagan,1992). Vegetation structure seems to influencethe spider composition on family level becausesimilar families cluster within a similar habitattype. The result also indicates that similarspecies are present at specific stage of cropgrowth. This provides valuable insights as to whycertain species may dominate at different timesof the season. Vegetation architecture plays amajor role in the species composition foundwithin a habitat (Greenstone, 1984; Scheidler,1990), and vegetation which is structurally morecomplex can sustain higher abundance anddiversity of spiders (Hatley and MacMahon,1980). The final stage of the crop results in ahabitat that is more complex and can supporthigher diversity. Surveys have demonstratedthat spiders respond numerically to the diversityand complexity of the vegetation (Rypstra, 1983;Halaj et al., 1998; Sudhikumar et al., 2005a, b).In addition, the difference in the seasonalabundance of spiders may be due to the variationin patterns of activity of individual spiders andthe phenology of total spider community (Coreyet al., 1998).

An increase in the spider populationaccording to the plant growth tends to depend onprey availability and, if the density of preybecomes higher, spiders are expected to

increase proportionally to some extent. The peakof population density of spiders coincides with

an increase of insect pests (Kiritani et al., 1972,

Kiritani, 1979). It has already been pointed out

by Kobayashi (1961) that the values of correlation

coefficients between the population density of

insect pests and that of spiders tend to increasefrom negative to positive form as crop growth

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advanced. As no quantitative evaluation was

done on the insect pest density during this study,

further investigations should be carried out toreveal the influence of insect pests on the

resident spider community. The amount of preys

alone does not affect the density of spiders. What

can be cited as other important factors is the

number of surviving individuals after

hibernation and other repair works related toagriculture. The growth of weeds quickens the

time of draining water from paddy fields and this

is considered to promote migration of spiders

from dikes to paddy fields and dikes can act as

an over wintering place of pests and as a source

of spiders (van den Bosh and Telford ,1964). Thechanges noted in spider association with specific

crop stage at different sampling times were

related to the flowering state of the crop.

Although it is reasonable to expect a significant

influence of crop characteristics on structuring

the resident spider community, the importanceof adjacent habitats must also be considered

(Duelli et al., 1990). Neighboring habitats may

also influence the composition of crop spider

fauna indirectly by modifying the dispersal of

potential spider prey and predators in the patchy

agricultural landscapes (Polis et al., 1998). Thequality of the adjacent habitats influences the

spider composition of the focal habitat via

multitudes of direct and indirect channels. Since

no data were collected from the adjacent

habitats and bunds, more studies are needed to

reveal the influence of these habitats on theoccurrence of spiders in the rice field proper.

CONCLUSION• Spiders are potential predators of insects

feeding on rice and help in maintaining theirpopulation under check.

• Before this study, no work was carried outabout the species composition of spiders andtheir diversity in riceland ecosystem inNortheastern Uttar Pradesh.

• The survey conducted in four district ofGorakhpur Division, viz., Kushinagar,Maharajganj, Gorakhpur and Deoria revealedthe presence of 58 species under 28 generain 10 families. Out of this figure only 41species were identified up to species taxon.Rests were identified only up to generic orfamily level.

• The most dominant species were Tetragnathajavana (Thorell) followed by Pardosapseudoannulata (Bösenberg and Strand),Tetragnatha mandibulata Walckenaer, Pardosabirmanica Simon, Hippasa holmerae Thorell,Tetragnatha maxillosa Thorell, Oxyopesjavanus Thorell, Hippasa partita (O.P.-Cambridge), and Camaricus formosus Thorell.

• Of the total catch (13,303), 30.9% werejuveniles (4111 individuals) and sex ratio(proportion of males in the population) was0.72, i.e., 72% of the adults were males (6618individuals).

• The spiders form 6 foraging guilds : (a) orbweabers (Araneidae and Tetragnathidae), (b)stalkers (Oxyopidae and Salticidae), (c) groundrunners (Lycosidae, Gnaphosidae), (d) foliagerunners (Clubionidae, Sparassidae), (e) spacebuilders (Pholcidae), and (f) ambushers(Thomisidae).

• Orb weabers (44.3%) formed the mostdominant guild followed by ground runners(30.0%), stalkers (15.2%), foliage runners(5.3%), ambusers (5.1%) and space builders(0.1%).

• Data demonstrated that stalkers reached thepeak population after 75 days oftransplantation of crop while other kinds offoragers attained the peak population during90 days of transplantation of crop growth.

• From the data of field study, 4 ecologicalindices, viz., Shannon-Weiner diversity index(H), Simpson diversity index (D), Margalefrichness index (R) and Pielou evenness index

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(E) were calculated to observe the diversity,richness and evenness of the species ofspiders in the target area in the fields of rice.

• The values of Shannon-Weiner diversityindices of spiders ranged between 2.5 to 3.5which demonstrated that every species in thesample is not the same but indicated that thenumbers of individuals are somewhat evenlydistributed between all the species.

• Simpson’s diversity index (D) ranged between0 and 1 which represents the probability thattwo individuals randomly selected from asample will belong to different species.

• The variations in Margalef richness index (R)demonstrated that the species richness of thespiders varied with collection sites and time(DAT) in northeastern Uttar Pradesh.

• Pileou evenness index (E) values rangedbetween 0 and 1 that demonstrated that theevenness of spider communities varied withcollection sites in northeastern UttarPradesh.

• The population growth of spiders in ricelandecosystem in northeastern Uttar Pradeshshowed a gradual increase in the 30th and 45th

DAT and reached the peak on 60th DAT andthen showed a decline in the 90th to 120th DAT.

ACKNOWLEDGMENTThe authors thank the Head of the Departmentof Zoology, DDU Gorakhpur University forproviding necessary facilities. The authorsdeclare that there is no conflict of interestsregarding the publication of this article.

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INCIDENCE AND BIODIVERSITY OF RICELAND SPIDERS