Host phytochemicals in regulation of nutritional ecology and population dynamics of Podontia quatuordecimpunctata L. (Coleoptera: Chrysomelidae)  

Roy N
M. U. C. Women’s College, Department of Zoology, Ecology Research Unit, Burdwan-713104, West Bengal, India
Author    Correspondence author
International Journal of Horticulture, 2015, Vol. 5, No. 4   doi: 10.5376/ijh.2015.05.0004
Received: 18 Feb., 2015    Accepted: 13 Mar., 2015    Published: 16 Apr., 2015
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Roy, 2015, Host phytochemicals in regulation of nutritional ecology and population dynamics of Podontia quatuordecimpunctata L. (Coleoptera :Chrysomelidae), International Journal of Horticulture, 2015, Vol.5, No.4 1-11 (doi: 10.5376/ijh.2015.05.0004)

Abstract

Determination ofhost preference depends on chemical cues including nutritional requirements is a cornerstone in insect pest ecology and their control. Their nutritional ecology and demographic parameters are co-related with the variation of host phytochemical regime. Here, the host preference in relation to feeding dynamics and life table parameters of Podontia quatuordecimpunctata L. were studied under laboratory conditions. The feeding indices and population parameters of P. quatuordecimpunctata were significantly higher (P < 0.05) on Spondias pinnata relative to S. dulcis (Anacardiaceae) due to the variation in their phytochemical regime of the respective host plants. The pest on S. pinnata has shorter mean generation time (Tc) of 143.333±0.265 days with higher net reproductive rate (R0) of 31.160±2.553. Their generation survival (GS) on S. pinnata (0.663) is significantly higher than S. dulcis (0.513) with reverse of total generation mortality (K). Thus, the pestshowed more feeding preference and higher reproductive growth to its host plant, S. pinnata than S. dulcis. This research supports the previous studies on insect nutrition in relation to their host phytochemicals and support to find the most vulnerable stage of this pest for appropriate control measures. It also provides the importance of S. pinnata as a trapping plant to avoid or minimum invasion of this pest towards S. dulcis for their better yields.

Keywords
Host preference; Nutritional ecology; Demographic parameters; Feeding dynamics; Phytochemical regime; Ttrapping plant

The hog-plum, Spondias dulcis and S. pinnata (Anacardiaceae) are popularly used for fruits in different parts of India including west Bengal, Assam, MP, UP, Punjab, Maharastra, etc. (Verheij and Coronel, 1991). The hog-plum, S. pinnata is a wild form of S. dulcis and both cultivated from the Himalayas of northern India to the Andaman Islands and also cultivated throughout Southeast Asia and Malaysia. The fruit of S. pinnata is smaller than the S. dulcis and inferior in quality but has the same uses. Different parts of the plants have several ethnopharmacological uses due to presence of different phytochemical constituents for nutritional, clinical and veterinary relevance in different parts of the world (Das et al., 2011). The leaf beetle, Podontia quatuordecimpunctata L. (Coleoptera:Chrysomelidae) is the best-known Podontia species of Blepharida-group because both adults and larvae severely defoliate the whole hog-plum plants (Pramanik and Basu, 1973; Deka and Kalita, 2002a). It was first reported by Bateman from Kolkata in 1895 (Stebbing, 1914) and further it was reported to occur in India (West Bengal, Assam, Sikkim, Meghalaya, Uttar Pradesh, and Andaman Islands), Mayanmar, Bangladesh and Malayasia (Stebbing, 1914; Deka and Kalita, 2002b ). Beside the two host plants they occationally attack Ficus elastic and Duabanga grandiflora (Singh and Misra, 1989; Baksha, 1997). The beetle is univoltine and both the larvae and the adults act as defoliator of hog-plum (Beeson, 1941). Generally they prefer the tender leaves but during severe infestation they consume the mature leaves, tender parts of stems, and even green barks of the plant (Howlader, 1993; Deka and Kalita, 2002c). They appear during July to September and disappear in October or November having peak infestation period during August to September (Beeson, 1941; Baksha, 1997; Deka and Kalita, 2002d). During this period complete defoliation caused stunting growth of the tree and leads to the reduction of fruiting, fruit size and yield. Still there is no suitable control measure against this insect defoliator except some non-specific insecticide to reduce their population. There are several reports regarding their taxonomy and life cycle (Corbett and Yusope, 1921; Pramanik and Basu, 1973; Husain and Ahmad, 1977; Sardar and Mondal, 1983; Singh and Misra, 1989; Baksha, 1997; Deka and Kalita, 1999; Becerra, 2004) but their feeding preference in terms of feeding dynamics, survivability and population parameters on the two host plants are unknown. Present study provide the knowledge on nutritional ecology and life table parameters of P. quatuordecimpunctata in relation to their respective host phytochemical regime, which will enable growers to employ the most appropriate control tactics towards integrated crop management (ICM) for hog-plum cultivation.

1 Results
1.1 Phytochemicals
The biochemical constituents of the two host plant, S. dulcis and S. pinnata, leaves are presented in Table 1. The primary metabolites i.e., total carbohydrates, proteins and lipids including amino acids content was higher in S. pinnata leaves (81.556±0.434, 15.656±0.519, 6.013±0.111 and 1.960±0.059µg/mg dry wt., respectively) and varied significantly with S. dulcis leaves (F2,4= 76.273, 44.864, 40.848 and 41.776, respectively, P<0.005) (Table 1). Total nitrogen and moisture content were higher whereas ash content was lower in S. pinnata (2.503±0.082, 58.596±0.398 and 0.130±0.012%, respectively) relative to S. dulcis (1.880±0.040, 54.740±0.903 and 0.203±0.015%, respectively) and also significantly differed (F2,4=46.563, 15.287 and 15.613, respectively, P>0.05) (Table 1). Among the secondary metabolites, total phenols and flavonoids concentration was lower in S. pinnata leaves (3.590±0.217 and 8.940±0.243µg/mg dry wt., respectively) and phenols content was significantly different from S. dulcis (F2,4=8.613, P < 0.05), but flavonoids was not significantly differed (F2,4=4.480, P > 0.05) (Table 1). On the other hand, tannin, saponin, alkaloids, phytate and oxalate content were highest in S. dulcis leaves (8.243±0.117, 14.350±0.051, 12.630±0.068, 5.150±0.044 and 2.636±0.115µg/mg dry wt., respectively) relative to S. pinnata (6.350±0.040, 11.323±0.050, 10.040±0.095, 4.133±0.035 and 1.276±0.084µg/mg dry wt., respectively) with highly significant differences (F2,4=235.149, 1792.313, 494.455, 328.710 and 91.464, respectively, P< 0.001) (Table 1). Thus, the nutritional factors (primary metabolites including nitrogen and moisture contents) relative to the anti-nutritional factors (Secondary metabolites) in S. pinnata leaves were always higher than S. dulcis.


Table 1 Phytochemical variations of the hog-plum, S. dulcis and S. pinnata leaves. Mean ± SE of 3 observations with F and P values are representing different significant level (ANOVA), while comparing one type of host plant with the other


1.2
Feeding dynamics
The life cycle and food utilization indices of this leaf beetle, P. quatuordecimpunctata were investigated in the laboratory condition by providing two types of host leaves separately and showed four distinct stages with four larval instars (i.e., egg, larva, pupa, and adult) (Figure 1). As the larval stages including adults defoliate the plants, the food utilization indices were relevant only for these stages which lead to the variation in total life history parameters including larval duration, fecundity, survivability and other population parameters of that beetle.


Figure 1 Schematic representation of the life cycle of Podontia quatuordecimpunctata L.


The developmental duration (i.e., larval and post larval duration) of the different stages of
P. quatuordecimpunctata on S. pinnata was shorter than S. dulcis but the adult longevity was always longer on S. pinnata. Food utilization efficiency measures of the all four instars and their adults of P. quatuordecimpunctata are given in Tables 2-6. They displayed higher value of food utilization indices (GR, CR, RGR, CI, ER, HCR, AD, ECI, ECD and HUE) when reared on S. pinnata leaves compare to S. dulcis as their host plant and showed different pattern of significance throughout all the feeding stages (Tables 2~6). The first instar larvae have no significant difference in all feeding indices except CR (Table 2), whereas, adults have highly significant differences for all feeding indices between the host plants (Table 6). In second, third and fourth instars RGR, CI, HCR and ECI values were significantly different (P<0.05) instead, GR and CR for second instar (Table 3), ER for second and third instar as well as AD and HUE for third and fourth instar (Table 4 and 5) are also significantly differed (P<0.05). The accumulated survivability throughout the developmental stages were greatest when the insects fed with S. pinnata leaves (R2=0.9988) instead of S. dulcis (R2=0.9932) leaves and significantly differed (P<0.05) (Figure 2). The adult emergence was significantly higher (F1,4=21.560, P< 0.01) on S. pinnata leaves (39.12±1.91%) relative to S. dulcis leaves (28.42±1.29%) (Figure 2). The fecundity was always higher on S. pinnata leaves (156.67±1.76 eggs/female) than S. dulcis (140.67±3.53 eggs/female) and significantly differed (F2,4=16.457, P< 0.01) (Figure 3). The FI (F2,4=18.451, P< 0.001) and GI (F2, 4=24.643, P< 0.01) of P. quatuordecimpunctata was higher on S. pinnata (0.015±0.027 and 0.741±0.340, respectively) than S. dulcis (0.014±0.015 and 0.647±0.260, respectively) (Figure 4).


Figure 2 Accumulated survivability (%) of P. quatuordecimpunctataon S. dulcis and S. pinnata leaves. Mean ± SE of 3 observations are significantly different (P < 0.05), while comparing one type of host plant as food with the other



Figure 3 Fecundity of P. quatuordecimpunctataon S. dulcis and S. pinnata leaves. Mean ± SE of 3 observations are significantly different (P < 0.05), while comparing one type of host plant as food with the other



Figure 4 Feeding index (FI), Growth index (GI), Generation mortality (K) and Generation survival (GS) of P. quatuordecimpunctataon S. dulcis and S. pinnata leaves. Mean ± SE of 3 observations are significantly different (P < 0.05), while comparing one type of host plant as food with the other



Table 2 Feeding dynamics of first instar larva of P. quatuordecimpunctataon S. dulcis and S. pinnata leaves



Table 3 Feeding dynamics of second instar larva of P. quatuordecimpunctataon S. dulcis and S. pinnata leaves



Table 4 Feeding dynamics of third instar larva of P. quatuordecimpunctataon S. dulcis and S. pinnata leaves



Table 5 Feeding dynamics of fourth instar larva of P. quatuordecimpunctataon S. dulcis and S. pinnata leaves



Table 6 Feeding dynamics of adults of P. quatuordecimpunctataon S. dulcis and S. pinnata leaves


1.3
Population dynamics
The population dynamics of P. quatuordecimpunctata was calculated on their two host plant leaves, S. dulcis and S. pinnata, separately and showed different pattern with highly significant differences in different population parameters.
The three cohorts containing 146,142,134 eggs for S. dulcis and 160, 156, 154 eggs for S. Pinnata were reared separately to construct the demographic data of P. quatuordecimpunctata and they represent similar pattern of development with significant variations (p< 0.05). The proportion of surviving (lx) and the survivorship (sx) of P. quatuordecimpunctata on the two host plants gradually decrease throughout the developmental stages (Table 7 and 8). The average population alive in each stage (Lx) was also gradually decreased in the development of egg to adult stage (Table 7 and 8) and always significantly higher on S. Pinnata than S. dulcis leaves throughout the developmental stages (F1,4> 12.482, P<0.02). Life expectancy (ex) followed the same pattern of lx for each host plants (Table 7 and 8) and always significantly higher on S. Pinnata relative to S. dulcis (F1,4> 9.730, P<0.05). The killing power (Kx) was always higher in the early stages than the advanced stages for both host plants (Table 7 and 8) and higher on S. Pinnata relative to S. dulcis leaves throughout the developmental stages.


Table 7 Stage-specific pooled life table of P. quatuordecimpunctata

International Journal of Horticulture
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