Introduction

Cotton whitefly, Bemisia tabaci (Aleyrodidae: Hemiptera: Insecta: Arthropoda) is one of the invasive pest species and a global threat to biodiversity as well as to agriculture and human interests. B. tabaci has been recorded from all continents of the world except Antarctica. Globally B. tabaci is known to infect 900 host plants and it is also a vector of over 100 plant viruses. It spreads rapidly and causes severe economic damage to crops around the globe through its feeding habits and transmission of viral diseases1.

The Indian subcontinent has been speculated as the center of origin for B. tabaci2. The diversity of B. tabaci sibling species complex has been extensively investigated and the different genetic groups have been compared using biological and molecular characteristics such as plant host preference, fecundity, ability to transmit begomoviruses, dispersal, insecticide resistance and mitochondrial cytochrome oxidase I (mtCOI) DNA sequences. Recently, unique molecular markers have been employed in phylogenetic analysis to identify the several global populations of B. tabaci. Sequencing a 657 bp region of mtCOI resulted in the identification of novel B. tabaci species and gave rise to the new term “cryptic species complex” based on 3.5% pairwise divergence in mtCOI sequences within B. tabaci species3,4,5,6.

Whitefly, B. tabaci has been proven to be a species complex comprising of 46 cryptic species3 and nearly 13 genetic groups have been recorded so far from India viz., Asia I, Asia I -India, Asia II 1, Asia II 5, Asia II 6, Asia II 7, Asia II 8, Asia II 11, Asia II 13, Middle East Asia Minor (MEAM)−1, MEAM-K, China 3 and China 73,4,5. The genetic groups of B. tabaci such as Asia II 1 and Asia II 7 are dominant genetic groups in Delhi, India7 whereas Asia II 1 has been reported most prevalent on cotton in Punjab, India8. Particularly, Asia II 1 has distributed predominantly in cotton leaf curl disease prone areas as it is a major vector of this viral disease8,9. B. tabaci has evolved resistance to insecticides of diverse modes of action. Among the B. tabaci cryptic species, MED (Biotype Q) has developed a high level of resistance to most of the insecticides10 and in the recent past, MEAM1, Asia I and Asia II-1 recorded resistance against various classes of insecticides11,12. Pesticide use may have an influence on biotype displacement. Research suggests that biotype Q has great fitness than biotype B when neonicotinoids and pyriproxyfen are used for control10,13.

Biotypes and genetic groups were reported to differ in their biological parameters with respect to hostplants on which they appear and their geographical locality. Biotype Q in comparison to biotype B, may be able to adapt to a broader range of plant species and cultivars. Biotype B is capable of minimizing or avoiding competitive encounters with indigenous congeneric competitors. A study with Asian genetic groups, Asia I, Asia II 1 and Asia II 7 revealed variations in biological attributes between them with Asia I having comparatively longer developmental period than other two genetic groups. While, they showed negligible differences with respect to survival rates, pre-oviposition period, egg stage, fourth instar and lifespan lengths on the other hand, were shown to be significantly different between these three cryptic species14. The developmental biology of B. tabaci MED (Mediterranean) showed that whiteflies attained the first instar stage 21.2 days post-oviposition, the second instar after 29.9 days, the third instar after 36.5 days and the fourth instar after 43.2 days, followed by adult eclosion at 57.3 days, with adult longevity averaging 33.9 days15. Despite inherent disparities in reproductive behaviour, the life history parameters of MEAM1 and MED may fluctuate based on the host plant16. MEAM1 exhibits a higher intrinsic rate of population increase on tomato than MED at 30 °C17while MED has shorter developmental durations on chilli18. The total developmental period from egg to adult for B. tabaci Asia II 5 genetic group was 22.82 days. Adult longevity, fecundity and adult emergence in B. tabaci Asia II 5 were observed to be 6.80 days, 73.33 eggs per female and 86.59%, respectively. The egg hatching and survival rates in B. tabaci Asia II 5 were found to be 91.68% and 78.09% respectively19.

The choice of simple demographic models such as lifetables with clear biological material is a significant step toward a deeper understanding of the biology and population dynamics of insect pests. Detailed understanding of the biological traits of the pest in relation to its development and reproduction over the hostplants can be used as a tool in designing pest management strategies20. Life table analysis is a powerful approach to analyze insect biology and ecology21,22,23 and also to understand the agricultural pests and their biological control24,25,26,27. Substantial progress has been made in developing integrated pest management (IPM) strategies to economically and efficiently manage pest populations in infested crops. These management systems were focused on a sound understanding of the population dynamics of B. tabaci where life tables have been a crucial tool in building this understanding possible28,29,30. Very little information is available on the life history traits and demographic parameters within the Asian genetic groups of B. tabaci. Hence this study was taken up to explore the life history traits and demographic parameters of Asia II 1, Asia II 5 and Asia II 7 genetic groups of B. tabaci which are widely prevalent in India.

Materials and methods

Collection and maintenance of whitefly populations

Populations of B. tabaci were collected from farmer fields located in four agro climatic regions of India, namely New Delhi (Delhi: 28.6377° N, 77.1571° E), Sri Ganganagar (Rajasthan: 29.9320° N, 73.8922° E), Indore (Madhya Pradesh: 22.7196° N, 75.8577° E) and Coimbatore (Tamil Nadu: 11.0152° N, 76.9326° E), and the location are shown in Fig S1 and Sup. Table S1. Adults of B. tabaci were collected early in the morning using a handheld aspirator. Infested leaves containing the nymphs and pupae were also collected manually. Whiteflies collected were transported to the laboratory in ventilated cages where leaflets infested with nymphs and pupae were inserted into wet sponges. All the B. tabaci populations used in this study were established on insecticide-free seedlings of cotton, brinjal and tomato in individual net cages under standard laboratory conditions of 27 ± 2 °C, 60 per cent relative humidity and 14-hour light/10-hour dark photoperiod in insect-proof climate control chambers at the Division of Entomology, Indian Agricultural Research Institute, New Delhi, India.

Genomic DNA isolation, PCR and sequencing

Individual whitefly was selected from each population and washed twice with sterile water before DNA extraction. Total genomic DNA was extracted from a single adult using DNASure Mini Tissue Kit (Nucleopore, Genetix NP61305) according to the manufacturer’s protocol. Partial mtCOI region was amplified in a thermal cycler by following standardized PCR conditions, initial denaturation for 10 min at 94 °C followed by 35 cycles of 94 °C for 30 s, 48 °C for 30 s of annealing and 72 °C for 40 s of extension with a final extension step for 5 min at 72 °C. A negative control was included each time containing no DNA template to confirm amplification. PCR amplification was carried out in 25 µl reaction mixture containing 12.5 µl of ready to use PCR master mix with loading dye (Emerald Amp GT, Takara), 5.5 µl of nuclease free water, 1 µl each of forward and reverse primers, namely, C1-J-2195 (5’ - TTGATTTTTTGGTCATCCAGAAGT-3’) and TL2-N-3014 (5’ - TCCAATGCACTAATCTGCCATATTA-3’)31 and 5 µl of insect DNA. Thermal cycling was performed on a 96-well thermal cycler (Applied Biosystems, Thermo Fisher Scientific). The confirmed amplified PCR products were purified and subjected to bidirectional Sanger sequencing at AgriGenome, Kochi, India.

Genetic group characterization based on phylogeny

The mtCOI sequences obtained from this study along with curated dataset of reference sequences of B. tabaci genetic groups 5,32 were aligned using BioEdit v7.2. Putative pseudogenes along with ambiguous sites were removed and gap adjustment and trimming of overhangs were manually carried out. The aligned sequences were subjected to Basic Local Alignment Search Tool (BLASTn) to confirm the genetic identity of B. tabaci. The four newly characterized haplotype sequences were submitted to NCBI and assigned with accession numbers, and the genetic group identity was further confirmed by phylogenetic and molecular evolutionary studies using global whitefly genotype database including six outgroups species, namely B. afer, B. barbericola, B. atriplex, B. subdecipiens, B. tuberculata and Trialeurodes vaporariorum using ClustalW programme with default parameters in MEGA X. Phylogenetic tree was constructed using “maximum-likelihood approach” and the four sequences obtained from this study were assigned with the genetic group identity based on clade grouping.

Biological traits and lifetable parameters

Clip cages (made of thick transparent cellophane sheets of the size 5 cm diameter and 6 cm height, with pin holes for gas exchange) were used to confine whitefly adults for recording the biological traits and life table parameters. Four different B. tabaci populations as mentioned above were used in this study. The cotton seedlings of 3-4 leaf stage were used where the genetic groups were maintained in separate chambers under standard laboratory conditions of 27 ± 2 °C, 60 per cent relative humidity and 14-hour light/10-hour dark photoperiod in insect-proof climate control chambers at Division of Entomology, Indian Agricultural Research Institute, New Delhi, India. For the life table study, 20 pairs of newly emerged whiteflies for each genotype were released into clip cages and each cage was considered as a replicate and 20 biological replicates were maintained for each set. The creamy-white eggs laid within 24 h were recorded under stereo zoom microscope. Only one egg was kept untouched in each clip cage and the remaining eggs were brushed with a fine insect brush under the microscope and the single egg in each cage was marked with a non-toxic marker to locate them easily. A single clip cage was used per leaf and a small numbered tag was tied to the petiole of the leaf for reference. The developmental stage and survival status of each individual egg were recorded daily at a fixed time in a day from starting to end of the experiment. To determine the fecundity and adult longevity, newly emerged adults from each genotype were collected and paired in clip cages and checked daily for their survival and fecundity until the death of all individuals.

Statistical analysis

The life history data of B. tabaci obtained from each of the genotype were entered separately into TWOSEX-MS Chart. The software vastly simplifies the complicated and time-consuming process of calculating many population parameters individually. The life table parameters calculated using raw data are presented in Supplementary Table. The duration of development, fecundity, adult preoviposition period (APOP) and total preoviposition period (TPOP) and other population parameters were calculated with the TWOSEX-MS Chart program22. According to the age-stage, two-sex life table principle, the following parameters were computed as given by the respective formulas: Age-stage-specific survival rate (Sxj): \(\:{\text{S}}_{\text{x}\text{j}}=\frac{{\text{n}}_{xj}}{{n}_{01}}\), age-specific survival rate (lx): \(\:{l_x} = \sum\limits_{j = 1}^m {{{\mathbf{S}}_{{\mathbf{xj}}}}}\); age-stage-specific fecundity (fxj); age-specific fecundity (mx): \(\:{m_x} = \frac{{\sum\nolimits_{j = 1}^m {{S_{xj\:}}{f_{xj}}} }}{{\sum\nolimits_{j = 1}^m {{S_{xj\:}}} }}\); age-specific maternity (lx*mx), age-stage-specific life expectancy (exj): \(\:{e_{xj}} = \sum\nolimits_{i = x}^\infty {\sum\nolimits_{y = j}^m {S\prime {\:_{iy}}} }\); age-stage-specific reproductive value (Vxj): \(\:{{\text{V}}_{{\text{xj}}}} = \frac{{{e^{r(x + 1)}}}}{{{{\text{S}}_{{\text{xj}}}}}}\sum\nolimits_{i = x}^\infty {{e^{ - r(i + 1)}}} \sum\nolimits_{y = j}^m {{\text{S}}\prime {\:_{{\text{iy}}}}{{\text{f}}_{{\text{iy}}}}}\), intrinsic rate of increase (r): \(\sum\nolimits_{x = 0}^\infty {{e^{ - r(x + 1)}}\:\:{l_x}\:{m_{x\:}} = 1.}\), finite rate of increase (λ): \(\:\varvec{\uplambda\:}={e}^{r}\), net reproductive rate (R0): \(\:{R_0} = \sum\nolimits_{x = 0}^\infty {{l_x}\:{m_{x\:}}}\), mean generation time (T): \(\:\text{T}=\frac{\text{l}\text{n}\:\:{\text{R}}_{0}}{r}\). The age-stage, two sex life table is useful because it enables users to precisely describe demographic characteristics, while, it also considers differences among stages and between sexes33. To minimize the variability in the results, the mean, standard error, and variances of the population were calculated using a bootstrap procedure (100,000 replications) available in the TWOSEX-MS Chart program34. Differences in the means of the duration (days) of the developmental stages of B. tabaci genetic groups were compared using Tukey’s HSD multiple range test in the R software package. Microsoft Excel 2019 was used to generate the graphs.

Results

Genetic group characterization based on phylogeny

All four newly characterized haplotype sequences, after contig preparation, were submitted to NCBI and assigned accession numbers, namely: New Delhi (MN830439), Sri Ganganagar (MN830430), Indore (MN830433) and Coimbatore (MN830438). Phylogenetic analysis of mtCO1 sequences revealed that the Sri Ganganagar and Indore populations belong to Asia II 1 (The Asia II 1 population from Indore, Madhya Pradesh, India, is denoted as Asia II 1-Indore throughout the manuscript) while the Coimbatore population belongs to Asia II 5, and the New Delhi population clustered as Asia II 7. The sequences obtained from the study are represented in red in the phylogenetic tree. All four populations showed 100% similarity with the reference sequences of their respective genetic groups within the B. tabaci species complex (Fig. 1).

Fig. 1
figure 1

Phylogenetic tree of mtCOI haplotypes of B. tabaci including some outgroups and cryptic species of B. tabaci using maximum likelihood approach in MEGA X. The sequences represented in red color are generated from the present study.

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Biological traits of genetic groups

The Duration (days) of the developmental stages and reproduction parameters of B. tabaci genetic groups are presented in the Table 1 and the duration in days of the developmental stages of all the three genetic groups of B. tabaci under study were pictorially depicted in Fig. 2. The incubation period of egg was shortest in Asia II 7 (6.8 ± 0.14 days) while it was longest in Asia II 5 (9.6 ± 0.13 days) where Asia II 1 Sri Ganganagar and Asia II 1 Indore population recorded 8.1 ± 0.1 days and 7.7 ± 0.11 days respectively (Supp. Table S2). The significant differences observed in the total pre-adult duration including egg and nymphal instars (L1-L4) was highest in Asia II 5 (25.61 ± 0.27 days) and lowest in Asia II 7 (20.38 ± 0.32 days) however it was 22.47 ± 0.36 days and 21.72 ± 0.33 days for Asia II 1 and Asia II 1 Indore respectively. The highest adult longevity was observed in Asia II 5 (23.39 ± 0.44 days) and lowest in Asia II 1 Indore (21.83 ± 0.41 days) whereas it was 22.24 ± 0.25 and 22.38 ± 0.30 days for Asia II 1 and Asia II 7 respectively. The mean fecundity differed significantly among genetic groups and was highest in Asia II 7 with 52.33 ± 1.26 eggs, in turn, it was in the ascending range of 36.43 ± 1.87, 43.79 ± 2.83 and 45.79 ± 2.4 eggs respectively for Asia II 5, Asia II 1 Sri Ganganagar and Asia II 1 Indore. The adult pre-oviposition period (APOP) is the duration from adult emergence to the first reproduction by females whereas the total pre-oviposition period (TPOP) is the period from birth (when the egg is laid) to the first reproduction by females. The APOP was found to be same in all the genetic groups under current study with no significant differences (1.00 ± 0.0 days) whereas TPOP found highest in Asia II 5 (26.57 ± 0.33 days) followed by 21.5 ± 0.42, 22.79 ± 0.39 and 23.5 ± 0.44 days in Asia II 7, Asia II 1 Indore and Asia II 1 respectively. The mean oviposition days observed to be highest in Asia II 7 (4.33 ± 0.14) followed by Asia II 1 Indore (3.86 ± 0.18), Asia II 5 (3.57 ± 0.14) and Asia II 1 (3.5 ± 0.14). Principal component analysis (PCA) for the variations between the developmental stages and reproductive parameters of genetic groups showed that the first two principal components explain approximately 68.83% and 20.02% of the total variance, respectively. The plot illustrates how the different B. tabaci genetic groups relate based on their developmental and reproductive parameters (Fig. 3A). The significant differences observed within the reproductive parameters such as fecundity, APOP, TPOP and oviposition days were depicted using PCA biplot, which categorized the variation in principal components with approximately 90.6% and 9.2% of the total variance within genetic groups (Fig. S2). Biological differences among genetic groups for life history traits were also represented using a bipartite network. The network clearly shows the differential relationship between the parameters among the genetic groups (Fig. S3).

Table 1 Duration (days) of the developmental stages and reproduction parameters of B. tabaci genetic groups.
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Fig. 2
figure 2

Duration in days of the developmental stages of all the three genetic groups of B. tabaci.

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Fig. 3
figure 3

(A) Principal component analysis depicting the variations among the mean values of developmental stages of three genetic groups of B. tabaci (B) Comparative analysis depicting the variations among the mean values of developmental stages, reproductive and demographic parameters of three genetic groups of B. tabaci.

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Life table parameters of genetic groups

The developmental stages and life table parameters were calculated using the TWOSEX-MS Chart program. The age-stage specific survival rate (sxj) represents the probability that an individual survives to age x and stage j, where k denotes number of stages. The whitefly genetic groups were studied for their Age-stage specific survival rate (sxj) that showed the likelihood of survival of newly deposited eggs of B. tabaci through age x and stage j. All the genetic groups survived to age x and stage j but not much difference was observed among the four genetic groups, although Asia II 1 showed higher survival rates in the nymphal stage (Fig. 4). The age specific survival rate (lx), age specific total fecundity of the whole population (mx), age-stage specific fecundity (f(x)) and age specific maternity (lxmx) were shown in the Fig. 5. As the age increases, the lx of the genetic groups decreases. The peaks of mx curve were highest at 28.0 days (8.10 eggs) for genotype Asia II 5 and lowest at 22.0 days (7.23 eggs) for Asia II 7. Similarly, the peaks of fx were recorded highest at 20.0 days (29 eggs) for Asia II 1 genotype and lowest at 25.0 days (10.5 eggs) and 23.0 days (10.5 eggs) for genetic groups Asia II 5 and Asia II 1 Indore, respectively. The age specific maternity (lxmx), calculated from fx and mx, was highest for genotype Asia II 5 at days 28.00 (7.3 eggs) and least for Asia II 7 at 21.00 days (5.25 eggs) (Fig. 5).

Fig. 4
figure 4

Age-stage-specific survival rate S(xj) of Genetic groups of B. tabaci (A) Asia II I (B) Asia II I-Indore (C) Asia II 5 (D) Asia II 7.

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Fig. 5
figure 5

Age-stage-specific female fecundity (fxj), Age-specific fecundity (mx), Age-specific net maternity (lxmx) and Age-specific survival rate (lx) of Genetic groups of B. tabaci (A) Asia II I (B) Asia II I-Indore (C) Asia II 5 (D) Asia II 7.

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The age specific fecundity (mx) proposes the number of female offspring per female of age x and stage j. The highest number of eggs laid were observed to be 8.1 by the genotype Asia II 5 at the age 28 days, while the other genetic groups Asia II 1 (Indore), Asia II 1 and Asia II 7 exhibited their highest fecundity at days 24 (7.5), 24 (7.11) and 22 (7.2) respectively (Fig. 6). The age-stage reproductive value (vxj) reveals the contribution of an individual to the age x and stage j of the future population. In the current study, the reproductive values of the genotype Asia II 1 Sri Ganganagar spiked to 60.30 when the females started to emerge at the day 19. Parallelly, the reproductive values increased distinctly to 43.57, 42.82 and 35.68 in the genetic groups Asia II 7, Asia II 1 (Indore) and Asia II 5, respectively when females started to appear at the day 19 wherein Asia II 1, the emergence of the females started 3 days later than the other genetic groups (Fig. 7). Based on the age-stage, two-sex life table analysis, the age-stage specific life expectancy(exj) gives the expected life span of an individual of age x and stage j, can live after age x. The age-stage life expectancy (exj) of the four genetic groups were shown in the Fig. 8. The maximum life expectancy of the females was 25.71 days in Asia II 1. The corresponding life expectancy values of Asia II 1(Indore), Asia II 5 and Asia II 7 female adults were 24.87, 24.25 and 23.75 days respectively.

Fig. 6
figure 6

Age-specific fecundity (mx) of Genetic groups of B. tabaci (A) Asia II I (B) Asia II I-Indore (C) Asia II 5 (D) Asia II 7.

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Fig. 7
figure 7

The age-stage reproductive value (vxj) of Genetic groups of B. tabaci (A) Asia II I (B) Asia II I-Indore (C) Asia II 5 (D) Asia II 7.

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Fig. 8
figure 8

Age-stage specific life expectancy (exj) of Genetic groups of B. tabaci (A) Asia II I (B) Asia II I-Indore (C) Asia II 5 (D) Asia II 7.

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Demographic parameters

The demographic parameters of B. tabaci genetic groups are presented in Table 2. The significant differences were observed in the demographic parameters of genetics groups under this study. Net reproductive rate (R0) is the total number of offspring that an average individual (including females, males, and those died in immature stage) can produce during its lifetime. R0 was significantly higher in Asia II 1(Indore) with the value 31.08 ± 4.95 while found to be lowest in Asia II 5 (25.27 ± 4.16) succeeded by Asia II 1 (30.34 ± 4.97) and Asia II 7 (31.08 ± 4.95). Finite rate of increase (λ) is the finite rate in the population growth rate as the time approaches infinity and the population reaches the stable age-stage distribution. The population size will increase at the rate of λ per time unit or number of females that produce one female per day. The highest value for the λ shared by Asia II 7 (1.158 ± 0.0) and Asia II 1 Indore (1.151 ± 0.0) while the lowest in Asia II 5 (1.120 ± 0.0) and it was 1.145 ± 0.0 in Asia II 1.

Table 2 Population parameters of B. tabaci genetic groups.
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Intrinsic rate of increase (r) is the population growth rate as time approaches infinity and the population reaches the stable age stage distribution. The intrinsic rate of increase recorded its highest in Asia II 7 (0.146 ± 0.0) followed by Asia II 1 Indore (0.141 ± 0.0) and Asia II 1 (0.136 ± 0.0) and found lowest in Asia II 5 (0.114 ± 0.0) (Supp Table S3). Mean generation time (T) is the period that a population requires to increase to R-fold of its size as time approaches infinity and the population settles down to a stable age-stage distribution or the time that passes between first and next-generation oviposition. Longest mean generation time recorded for Asia II 5 (28.36 ± 0.34) followed by Asia II 1 (25.15 ± 0.55) Asia II 1 Indore (24.62 ± 0.39) and shortest in Asia II 7 (23.46 ± 0.38). The PCA results for demographic parameters among the genetic groups showed that the first two principal components explain approximately 98.86% and 1.1% of the total variance, respectively. The plot illustrates how different the B. tabaci genetic groups related based on their demographic parameters (Fig. S2).

According to the objective of this study, the resulted mean values with respect to comparative analysis of life history traits of three different genetic groups showed significant differences in their biological cycle. These observed variations were graphically represented using the boxplot which show-off the overall variation among the genetic groups for developmental, reproductive and population parameters (Fig. 3B).

Discussion

Insects are age-stage structured. Insect physiology, biochemistry, ecology and other fields necessitate stage differentiation, which is critical when measuring the damage caused by a pest population or the control efficacy of bioagents or natural enemies. The two-sex life table gives the most comprehensive description and analysis of the survival and reproduction of a population and thus, this method may be highly beneficial in revealing the difference in the two populations. This method takes into account the male population and the variable developmental rate occurring among individuals and can overcome the shortcoming of the traditional female-based, age-specific life table method, which ignores the male individuals, the stage of differentiation, and variable developmental rates among individuals. The general description of the lifecycle of B. tabaci stating that at 25 °C, eggs will hatch in 6–7 days. First instar will last for 2–3 days after egg is hatched and upon feeding, they will moult to the second instar. The second, third and fourth nymphal instars are immobile with atrophied legs and antennae but bears a pair of tiny eyes. The duration of second and third nymphal instars last about 2–3 days each while the fourth instar typically called red-eyed nymphal stage or pupal stage requires 5–6 days. Adults on emergence finds for mate and upon successful mating, female lays as many as 200 eggs in her lifespan and the total duration of development is around 40 days from egg to adult depending on temperature and other parameters35,36. Winged adults on emergence fly around and between the crops37 and the plant species fed by the adult vary in quality, some influences best for survival and some other plant species enhances egg production39. Longevity of the adult is lasts for a week or more and the fecundity of the female depends on the amount of food ingested during adulthood40.

The significant disparities were observed in the life history traits of genetic groups (Asia II 1, Asia II 7 and Asia II 5) under this present investigation. Findings of the present study reveals that the total developmental time from egg to adult was significantly least in Asia II 7 and observed highest in Asia II 5 compared to Asia II 1 and Asia II 1 Indore. our results are at par with previous results indicating total developmental periods of Asia I, Asia II 1 and Asia II 7 ranged from 23.80 to 25.75 days14. The previous reports showed that the total developmental duration of Asia II 5 observed to be 22.8 days19 whereas in case of MEAM1 and MED, developmental times on capsicum are shorter for MED than MEAM118 where hostplant also influence the developmental duration of genetic groups. The highest adult longevity was observed in Asia II 5 and lowest in Asia II 1 Indore followed by Asia II 7 and Asia II 1 respectively. The mean fecundity observed to be highest in Asia II 7, in turn followed in the ascending order Asia II 5, Asia II 1 and Asia II 1 Indore in the current investigation and these results are similar with the previous report depicting that mean fecundity of Asia II 7 is highest followed by Asia II 1and Asia I14. The earlier study conducted to unravel the differences in life history parameters of B. tabaci genetic groups of India14 reveals that the developmental period found slightly longer in Asia I than in the Asia II and the female longevity was found highest in the Asia I followed by Asia II 1 and Asia II 7. Significant differences were observed for total developmental time, egg duration and duration of the fourth instars of Asia I, Asia II 1 and Asia II 714.

Another similar study conducted to compare the differences in biological traits between two cryptic species, MEAM1 and Asia II 1 on two different kinds of hosts reveals that the MEAM1 developmental periods did not differ significantly across hosts, whereas Asia II 1 developed more slowly on vegetables than on cotton. MEAM1 longevity and fecundity were highest on tomato, while Asia II 1 longevity and fecundity were highest on cotton8. The previous study also reports that females are always more numerous than males regardless of cryptic species. The highest sex ratio was recorded in Asia II 7 followed by Asia II 1 and lastly by Asia I. The male longevity found in the declining order, Asia II 7 > Asia I > Asia II 1 whereas the female longevity was in the declining order, Asia I > Asia II 1 > Asia II 7. The mean fecundity observed to be in the declining order, Asia II 7 > Asia II 1 > Asia I14. Even the host plants have a significant effect on the longevity and fecundity of B. tabaci7,40,41 where significant variation observed in the longevity of both the male and the female ranging from 12.3 to 17.6 days despite being on the same host plant cotton. Age-stage two-sex life table studies of the B. tabaci B biotype on tomato, cotton, pepper and okra hosts revealed that tomato had the longest pre-adult developmental period, highest survival rate and maximum fecundity, while okra showed the lowest42. MEAM1 and MED genetic groups laid around the equivalent number of eggs on most of the host plants43.

The present study depicted the significant variations in the biological parameters of major genetic groups of B. tabaci viz., Asia II 1, Asia II 7 and Asia II 5. The major significant differences were found in developmental time, duration of instars, fecundity, adult longevity and lifetable parameters. Similar studies with other genetic group also revealed the disparities where the developmental biology of B. tabaci MED (Mediterranean) showed that the whiteflies attained the first instar stage 21.2 days post-oviposition, the second instar after 29.9 days, the third instar after 36.5 days and the fourth instar after 43.2 days, followed by adult eclosion at 57.3 days, with adult longevity averaging 33.9 days and these biological values are significantly higher compared to our Asia II 1, Asia II 7 and Asia II 515. The life history parameters of MEAM1 and MED may vary depending on the host plant, despite their innate differences in reproductive behaviour16. While MED has shorter developmental periods on chilli18MEAM1 shows a greater intrinsic rate of population increase on tomato than MED at 30 °C17. A comparative study was conducted wherein the total developmental period from egg to adult was 22.82 and 23.40 days for B. tabaci Asia II 5 and T. vaporariorum respectively, with no significant differences. The T. vaporariorum showed significantly better adult longevity, fecundity and adult emergence than B. tabaci Asia II 5 genetic group. Similarly, T. vaporariorum also depicted a greater egg hatching and survival rate than B. tabaci Asia II 519.

Age-stage specific survival rate (sxj) observed with least significant differences in the survival rates among the four genetic groups where Asia II 1 showed higher survival rates in the nymphal stages. The maximum age-stage specific life expectancy (exj) was observed for females. Asia II 1 females recorded highest life expectancy followed by Asia II 1(Indore), Asia II 5 and Asia II 7 and these results were supported by the previous findings which revealed that the mean percentage of survivorship was found nearly equal in all the 3 cryptic species, and these ranged from 68.49 to 69.12 per cent14. MEAM1 survival was highest on tomato (53.5 ± 1.1%), while Asia II 1 survived best on cotton (67.3 ± 11.6%)8. Results of the present investigation also revealed that highest finite rate of increase (1.15), highest intrinsic rate of increase value (0.14) and shortest mean generation time (23.46 days) observed in Asia II 7 as compared to Asia II 1, Asia II 1 Indore and Asia II 5. Similar kind of study with other genetic groups of B. tabaci showed that the MEAM1 intrinsic rates of increase (rm) on cotton and vegetable were similar (0.08 to 0.10), whereas the Asia II 1 rm on cotton (0.15) was higher than on vegetables (0.11 to 0.13). The biology of MEAM1 from Pakistan was compared with several published studies; it had a consistently slower rate of development, lower percentage survival, lower adult longevity, longer generation time, lower net reproductive rate and lower rm8. The intrinsic rate of natural increase of A and B biotype reared on cotton shows 0.1010 and 0.1033 respectively and almost the equal rm observed for Q-biotype of B. tabaci reared on tomato (0.106)44. B. tabaci fed on cotton and tomato have higher population parameters (R0, r, and λ) than pepper and okra. The mean generation time in okra varied significantly across all studied genotypes43.

Interestingly, the differences were also observed in the biological traits when B. tabaci fed on Bt and non-Bt cotton but no studies were conducted yet with genetic groups of B. tabaci. One such study with B. tabaci population reveled that Incubation, nymphal period and pupal durations were shorter on Bt cultivars and longer on non-Bt cultivars. Adult longevity increased in Bt cultivars but decreased in non-Bt cultivars. Pre-oviposition was higher in non-Bt cultivars but lower in Bt cultivars. Bt cultivars had longer oviposition times than non-Bt cultivars. Fecundity was higher with Bt (57.5 eggs/female), but lower with non-Bt (48.2 eggs/female). Age-survivorship declined with age, and the highest mortality was recorded at the egg stage, with non-Bt having a longer life span than Bt cultivars. Bt cultivars had the highest net reproduction rate and the lowest intrinsic rate of increase. Non-Bt cultivars had the highest finite rate of increase, mean generation time, and population doubling time, whereas Bt cultivars had the lowest. The experimental results revealed that Bt was somewhat more suited for developing B. tabaci than non-Bt cultivars45. This kind of studies are lacking with genetic groups of B. tabaci and are need of the hour.

An integrative study of how variations in life-history traits, mating behaviors, and the ability to respond to selection may create a solid basis for predicting whitefly species extinction in both laboratory and field trials. While the key traits influencing exclusion or coexistence varied by region, reproductive interference resulting in a reduction in the production of fertile females in one whitefly species compared to another emerges as a significant mechanism that could drive rapid species exclusion under various conditions46. Heritable bacterial symbionts are widespread in arthropods that may have significant impacts on the biology of their hosts. These effects are mostly mediated by the ecology of the host. Rickettsia symbiont of B. tabaci provide a strong fitness advantage to its host under laboratory and field conditions, moreover the frequency of the endosymbiont is heterogenous across field population indicating that the benefits of the symbiont impinge on additional factors47. Physiological and genetic differences, such as the presence of odorant-binding proteins and chemosensory proteins, play a crucial role in host location, oviposition site selection, and insecticide resistance, as their abundance and expression levels vary across different genetic groups of B. tabaci12,48,49. Temperature50,51,52host plant suitability53,54natural enemies55,56 and management aspects17 are the key factors responsible for regulation of biology and population dynamics of whiteflies. Formulating an effective pest management system requires adequate knowledge on ecological aspects of the pest concerned and its host plants, climatic factors etc44,57. It is interesting that genetically different haplotypes under the same species actually have different biological characteristics8,13 have already shown that not all haplotypes under the same species have the same potential to invade. Future research should focus on finding local land races or developing new varieties that hinder or discourage the pest while promoting parasitoids. An additional option for enhancing mortality could be the introduction of exotic parasitoids to augment the native species following rigorous climate matching studies58. The recent study on Asia II 1 revealed that the Asia II 1 genetic group of B. tabaci is increasingly dominant across Asia due to its extensive presence, damage potential and ability to outcompete other species. This rapid expansion, particularly in countries like India and Pakistan, can be linked to dynamic changes in haplotype and nucleotide diversity, high gene flow, adaptability to various host plants, swift insecticide resistance, and competitive advantages59. The results obtained from the present investigation are definitely useful in understanding the biology of various whitefly genetic groups but further field studies at large scale will be helpful to validate them.

Biological attributes differ amongst genetically distinct haplotypes of the same species. There has been limited or no recorded comparison of biology amongst B. tabaci genetic groups. Judging from past findings on biological variation in genetic groups of B. tabaci, it is crucial to showcase those abundant genetic groups in specific regions with specialized interactions may differ in biology. The significant differences were observed in the developmental stages, reproductive and population parameters among the genetic groups under this investigation. The interesting thing that observed in this investigation was, variations observed within the same genetic group Asia II 1 collected from different agro climatic zones i.e., Asia II 1 from Sri Ganganagar and Indore, India. Comparison of various life history and demographic parameters from this study revealed that Asia II 7 observed with lowest total developmental time from egg to adult, shortest duration of the egg, lowest total developmental duration of larvae, L1-L4, highest mean fecundity, longest mean oviposition days, highest finite rate of increase, highest intrinsic rate of increase value and shortest mean generation time compared to Asia II 1 and Asia II 5 genetic groups. The biological and lifetable parameters observed to have differences within and among the genetic groups of B. tabaci. The peculiar genetic group feeding on different hostplants, collected from different agro climatic zones may definitely show disparities in their biology. The accurate information on reproductive biology and population growth of these whitefly genetic groups may facilitate the prediction of predator-prey population dynamics between whitefly and its natural enemies. These results also aid in uncovering the clues behind the insecticide resistance, resurgence, virus transmission efficiencies of these predominant Asian genetic groups in India and Asia.