Extensive surveys were conducted for collection, identification and documentation of invasive plant species and native insect herbivores in different districts of Kashmir Himalaya. A total of 09 districts were surveyed for a period of two years (2018-19 & 2019-20). Based on field surveys, highest number of invasive plant species were observed from district Kupwara (41), followed by district Baramulla (37), district Bandipora (31), district Budgam (27), district Kulgam (24), district Ganderbal (19), district Anantnag (17), district Pulwama, (15) and district Srinagar (12) (Fig. 1A) while maximum native insect herbivore species feeding on these invasive plant species were also reported from district Kupwara (15) and district Baramulla (15), followed by district Bandipora (14), district Budgam (12), district Kulgam (11), district Pulwama (10), district Ganderbal (10), district Anantnag (10), and district Srinagar (08) (Fig. 1G). In district Kupwara, 05 sites visited, and data collected suggested Plantago major (92) as the most abundant invasive plant species, followed by Trifolium rapens (91), Taraxacum officinale (78), and Plantago lanceolata (55) while the most abundant herbivores found were Altica himensis (170) followed by Chrysolina herbaceae (112), Agrotis nigrisigna (103) and Nezara viridula (102). In district Baramulla, 05 sites were visited which revealed Ranunculus arvensis (70) as strong invasive species followed by Dactylis glomerata (61), Plantago major (60) and Clinopodium umbrosum (59). The dominant native insect herbivore in district Baramulla was Altica himensis (144) followed by Agrotis nigrisigna (98) and Chrysolina herbacea (87). In case of district Bandipora of the Northern region, 06 sites were selected for the data collection, where Plantago major (88) was the most abundant invasive plant species followed by Cyanodon dactylon (45) Plantago lanceolata (40) and Taraxacum officinale (39) while potential insect herbivores were Altica himensis (120) and Plagiodera sp., (97).
From Central region, three districts were selected with 15 sites, 05 from district Budgam, 04 from district Ganderbal and 06 from Srinagar (Table 1). Plantago lanceolata (50) and Trifolium pratense (50) were reported as the dominant invasive plant species followed by Trifolium rapens (41) and Stellaria media (39) in district Budgam. Native herbivore species sighted here were Chrysolina herbacea (100), the dominant one, followed by Agrotis nigrisigna (72), Plagiodera sp., (72) and Altica himensis (53). Most abundant invasive plant species in district Ganderbal were Plantago major (72) and Trifolium rapens (70) while prospective insect herbivores were Nezara viridula (87), Chrysolina herbacea (62) and Agrotis nigrisigna (60). A total of 05 sites visited in the capital district Srinagar, Trifolium rapens (51), Taraxacum officinale (49), Plantago lanceolata (48), Plantago major (42), Cyanodon dactylon (36), Vulpia myuros (29), Trifolium pratense (24), Veronica persica (20), Anthemis cotula (14), Stellaria media (14) and Ranunculus arvensis (10) were chief invasive plant species whereas only 04 potential insect herbivores namely Chrysolina herbacea (51), Nezara viridula (49) and Agrotis nigrisigna (32) were reported.
From Southern region, a total of 03 districts were selected namely Anantnag, Kulgam and Pulwama with 05, 05 and 06 study sites, respectively (Table 1). In Anantnag district, the data from the select 05 sites revealed that Plantago major (59) is the most abundant invasive plant species followed by Taraxacum officinale (56), Trifolium pratense (48) and Trifolium rapens (48), while potential insect herbivores reported were Nezara viridula (83) followed by Altica himensis (67), Agrotis nigrisigna (64), Chrysolina herbacea (59) and Formica spp. (34). In district Kulgam, a total of 24 invasive plant species were reported from all 05 select sites and the native herbivore species feeding on them were 12 species. Out of all 24 plant species, Taraxacum officinale (60) was the most abundant insect species followed by Trifolium pratense (56), Trifolium rapens (52), Anthemis cotula (40) and Plantago major (40). From all 12 native insect herbivores species feeding on these invasive plant species, 02 insect species Chrysolina herbacea (78) and Altica himensis (73) were found to be potential herbivores attacking primarily Plantago major (40) and Rumex hastatus (09). Similarly, 06 sites were visited in district Pulwama with Taraxacum officinale (70), Trifolium pratense (42) and Plantago lanceolata (38) as the most abundant invasive alien plant species while Nezara viridula (96), Chrysolina herbacea (64) and Plagiodera sp. (59) were abundant insect herbivores.
The significance of the data of 09 districts of Kashmir Himalaya was analyzed by PAST 3, Version 1.0.0.0.0 software by subjecting it to different diversity indices like Shannon-Weiner index (H), Simpson’s index (D), Margalef’s index (MI), Evenness index (J) and Relative Abundance (RA) as depicted in Tables 3 and 4. On comparing the data of invasive plant species in various districts of Southern, Central and Northern regions of Kashmir Himalaya, the total number of invasive plant species was highest in district Kupwara (1017) followed by Baramulla (891) and Bandipora (718) (Fig. 1B). Total number of individuals of native insect herbivores feeding on invasive plants was highest in number in district Kupwara (770) followed by district Baramulla (616) and district Bandipora (615) of Kashmir Himalaya as shown in Table 4 and Fig. 1H. Simpson’s diversity index was highest at district Kupwara (0.955), while least at district Srinagar (0.893) which signified that Kupwara had high dominance of invasive plant species (Fig. 1C). Similarly, Simpson’s index for native insect herbivores was highest at district Bandipora (0.885) and Kupwara (0.879) followed by Baramulla (0.868) and Kulgam (0.859) while it was minimum at Srinagar (0.803) (Fig. 1I). Shannon-Weiner index (H) was highest in the district Kupwara indicating that these districts have maximum diversity of invasive plant species (Fig. 1D). On the other when the same index was applied to native insect herbivores feeding on these invasive plants, data depicted the highest value of H was at districts Bandipora (2.395) and Kupwara (2.358) and least at district Srinagar (1.764), revealing that the Bandipora and Kupwara districts have high diversity of native insects while district Srinagar had least diversity (Fig. 1J). Species evenness for invasive plant species depicted the highest value of 0.880 at district Pulwama and lowest of 0.709 at district Kupwara which illustrated that invasive plant species were more evenly distributed at district Pulwama (Fig. 1E) while in case of native insect herbivores, maximum value of 0.737 was observed at Anantnag and minimum 0.603 at district Baramulla (Fig. 1K). Margalefʹs diversity index (MI) had its peak value at district Kupwara (5.776) and lower most at district Srinagar (1.882) which in other words means that Kupwara shows maximum distribution pattern and richness of invasive plant species while it was minimum in district Srinagar (Fig. 1F). Following results were obtained on applying same index on native insect herbivores feeding on these invasive plants with a peak value of 2.335 at district Baramulla and only 1.334 at district Srinagar (Fig. 1L).
The Relative Abundance of all the invasive plant species and insect herbivore species at nine locations was also worked out by dividing the number of individuals of a species to the total number of individuals of all species and expressed as percentage (Figs. 2 and 3). Perusal of data revealed that Plantago major (9.372%) was the most dominant invasive plant species and highly flourished in Northern regions than Central and Southern regions. It was followed by Taraxacum officinale (8.557%), Trifolium rapens (8.185%), Trifolium pratense (7.104%) and Plantago lanceolata (6.821%). On the other hand, Altica himensis were the most dominant native insect herbivores feeding on these invasive plants with a total percentage of 17.640% followed by Chrysolina herbacea (16.809%), Nezara viridula (15.456%) Agrotis nigrisigna (14.221%) and Plagiodera spp. (9.425%).
Table 3
Diversity indices values of invasive plant species in 09 districts of Kashmir Himalaya.
Zone | North Kashmir | Central Kashmir | South Kashmir |
District | Bandipora | Baramulla | Kupwara | Budgam | Ganderbal | Srinagar | Anantnag | Kulgam | Pulwama |
Species | 31 | 37 | 41 | 27 | 19 | 12 | 17 | 24 | 15 |
No. of Individuals | 718 | 891 | 1017 | 655 | 538 | 345 | 497 | 569 | 414 |
Simpson Index | 0.950 | 0.952 | 0.955 | 0.948 | 0.920 | 0.893 | 0.922 | 0.935 | 0.914 |
Shannon-Weiner Index | 3.193 | 3.244 | 3.37 | 3.087 | 2.708 | 2.335 | 2.658 | 2.902 | 2.58 |
Evenness | 0.786 | 0.693 | 0.709 | 0.811 | 0.789 | 0.860 | 0.839 | 0.759 | 0.880 |
Margalef Index | 4.562 | 5.3 | 5.776 | 4.009 | 2.863 | 1.882 | 2.577 | 3.626 | 2.323 |
Table 4
Diversity indices values of native insect species in 09 districts of Kashmir Himalaya.
Zone | North Kashmir | Central Kashmir | South Kashmir |
District | Bandipora | Baramulla | Kupwara | Budgam | Ganderbal | Srinagar | Anantnag | Kulgam | Pulwama |
No. of species | 15 | 16 | 16 | 13 | 11 | 8 | 11 | 12 | 11 |
No. of individuals | 615 | 616 | 770 | 434 | 391 | 190 | 389 | 409 | 398 |
Simpson index | 0.885 | 0.868 | 0.879 | 0.856 | 0.857 | 0.803 | 0.857 | 0.859 | 0.851 |
Shannon-Weiner index | 2.395 | 2.267 | 2.358 | 2.113 | 2.087 | 1.764 | 2.094 | 2.114 | 2.042 |
Evenness | 0.731 | 0.603 | 0.660 | 0.636 | 0.732 | 0.729 | 0.737 | 0.69 | 0.700 |
Margalef index | 2.18 | 2.335 | 2.257 | 1.976 | 1.675 | 1.334 | 1.677 | 1.829 | 1.67 |
No. of species (A), No. of individuals (B), Simpson index (C), Shannon-Weiner index (D), Species evenness (E) and Margalef index (F) of invasive plants; No. of species (G), No. of individuals (H), Simpson index (I), Shannon-Weiner index (J), Species Evenness (K) and Margalef index (L) of native insect herbivores.
While summarizing the two years data (2018-19 and 2019-20), a total of 42 invasive plant species were recorded, of which 12 are worst invaders namely Plantago major, Taraxacum officinale, Trifolium rapens, Trifolium pratense, Plantago lanceolata, Cyanodon dactylon, Anthemis cotula, Clinopodium umbrosum, Ranunculus arvensis, Veronica persica, Dactylis glomerata and Vulpia myuros. A total of 14 native insect herbivores species were identified on these invasive alien plants, of which the prospect of 06 insect herbivore species as potential biocontrol agents is promising. The rearing of these insect species is worked out under laboratory conditions, followed by green house and in-situ experiments. Overall, 09 districts surveyed during the study period revealed highest number of invasive plant species in district Kupwara of Northern region of Kashmir Himalaya, while the lowest were in district Srinagar. The most dominant invasive plant species from North Kashmir was Plantago major (9.139%) with its maximum dominance in district Kupwara (3.503%). From Central Kashmir, most abundant invasive plant species was found in district Budgam (42.587%), where Trifolium rapens (10.533%) and Plantago major (10.403%) were found dominantly while from South Kashmir, maximum invasive plant species were found in district Kulgam (38.445%) and Taraxacum officinale (12.567%) was the dominant plant species found during our survey. From North Kashmir, Altica himensis was the most dominant native insect herbivore species. Likewise, from Central Kashmir, Chrysolina herbacea was the dominant one while from South Kashmir, Nezara viridula was found to be the most abundant native insect herbivore feeding on various invasive plant species.
Among the collected insect herbivores, a few viz., Chrysolina herbacea, Melanoplus differentialis, Pieris brassicae and Altica himensis are being reared on native and invasive plants under laboratory conditions to check their efficacy as potential biocontrol agents. The field observations of native insect herbivores feeding on invasive plant species in select sites are shown in Fig. 4.
A. Altica himensis feeding on Urtica dioica; B. Larvae of Aglais cashmeriensis feeding on Urtica dioica; C. Damage on Rumex hastatus by Altica himensis; D.Spittle bug on Cannabis sativa; E. Altica himensis feeding on Rumex hastatus; F. Chrysolina herbaceae on Mentha longifolia; G. manual insect collection; H. Chrysolina herbacia feeding on Mentha longifolia; I. Altica himensis feeding on Rumex hastatus; J .Infestation in Vitis flora by Altica himensis; K. Euphorbia flowers with visiting pollinators; L.Mating process of Chrysolina herbacia on Mentha longifolia.