Floristic and Taxonomy Laboratory, Department of UG, PG & Research in Botany, Karnatak University’s, Karnatak Science College, Dharwad - 580001, Karnataka, India

^*Corresponding author: Mouna S, Floristic and Taxonomy Laboratory, Department of UG, PG & Research in Botany, Karnatak University’s, Karnatak Science College, Dharwad - 580001, Karnataka, India; E-mail: mouna.sidd@gmail. com

Copyright: © Mouna and Kotresha. 2022. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Article Information: Submission:19/09/2022; Accepted: 20/10/2022; Published: 24/10/2022

An alien plant also referred to as exotic, introduced, foreign, non-indigenous or non-native, is one that has been introduced by humans intentionally or otherwise through human agency or accidentally from one region to another. Those naturalized aliens that become so successful as to spread in the flora and displace native biota or threatens valued environmental, agricultural, or personal resources by the damage it causes are considered invasive. Devarayanadurga Reserve Forest (DRF) in Tumakuru District is a tropical dry deciduous type, comparatively dense forest with predominant tree species. It is known for harboring varieties of medicinal plants. During the present study a total of 144 Invasive Alien Species (IAS) belonging to 130 genera of 51 families were recorded. Fabaceae is the dominating invasive family with 27 species followed by Asteraceae and Malvaceae with 11 and 8 species respectively. 105 IAS were reported to be affecting ecosystem functions and services, 56 IAS to be causing biodiversity loss and 81 IAS to be causing economic loss and health hazards of either human or wildlife or both. 111 IAS shows continuous spread in DRF with range extension. IAS affects the ecosystem of the region, the economy of the surroundings, habitat destruction, biodiversity loss, human health, and livelihood. Hence timely monitoring of the phenology and distribution pattern studies of IAS should be undertaken to successfully eradicate them and re-establish native species.

Alien species; Biodiversity; Invasive flora, Ecological impact, Tumakuru

Invasive Alien Species (IAS) is one of the major threats to global and local biodiversity. In forest ecosystems, the threats caused by IAS include hybridization, transmission of diseases and species competition [1]. An alien plant also referred to as exotic, introduced, foreign, non-indigenous or nonnative, is one that has been introduced by humans intentionally or otherwise through human agency or accidentally from one region to another. An alien plant that has escaped from its original ecosystem and is reproducing on its own in the regional flora is considered a naturalized species. Those naturalized aliens that become so successful as to spread in the flora and displace native biota or threaten valued environmental, agricultural, or personal resources by the damage it causes are considered invasive. Monitoring is required in invasive species management to determine the location and early detection of problematic species, whether a species is likely to become a problem in an area, whether a species is responding to management efforts and the impact of alien plant control methods on native species. Monitoring of invasion can be done through qualitative approach like species inventory (seasonally) and quantitative approach using phytosociological methods and mapping by ground-based methods (Via map overlays or GPS), remotely sensed images (aerial photos, high-resolution multispectral digital data). General methods practiced for the eradication of IAS include chemical methods, biological methods, and physical methods. Native plants can act as a sink for air pollutants and contribute significantly to carbon sequestration. Therefore, the loss of native plant diversity through invasive plant pathogens may indirectly affect human healththrough perturbations in environmental quality [2].

Tumakuru is located at 13^ο.34” N, 77^ο. 1” E., situated 70 km northwest of Bengaluru [3]. Devarayanadurga Reserve Forest (DRF) in Tumakuru District spread over 6194.57ha. is a tropical dry deciduous type, comparatively dense forest with predominant tree species. It is known for harboring varieties of medicinal plants and economically important plants. It is elevated at a height of 1188m above mean sea level.

The average annual rainfall in the district is about 680 mm. The soil type here is red loamy with neutral pH of 7.2, with electrical conductivity being normal at 0.22. Available nitrogen is 156.6 kg per acre, P₂O₅ is 26.3 kg per acre and K2O is 44.83 kg per acre which is moderate.

The forests in the district are confined mostly to the lower slopes of the hill ranges and are spread over the entire district in small blocks. The forests are mostly open and consist of mixed species varying from dry deciduous to thorny bushes [4]. The dominant tree species found in Devarayanadurga Reserve Forest includes, Anogeissus latifolia, Pterocarpus marsupium, Terminalia tomentosa, Terminalia chebula, Terminalia arjuna, Tamarindus indica, Tectona grandis, Santalum album, Albizzia lebbeck, Boswellia serrata, Hardwickia binata, Buchnania angustifolia and Terminalia bellerica. In addition to the higher order species, lower order species such as Acacia catechu, Wrightia tinctoria, Canthium parviflorum, Dodonaea viscosa, Cassia auriculata, Cassia fistula, and Albizia amara are also found.

Subsequent field visits were conducted to DRF, and plants were surveyed in the following spots i.e., Urdigere entry spot, University sanctioned land spot, lower slopes, and around Bhoga Narasimha Swamy temple and Yoga Narasimha Swamy temple, upper slopes and aroundVidyashankara temple, and in and around Namada chilume. The species were identified using Flora of Presidency of Madras Vol. I to III and Flora of Tumkur District [5,6].

Ecological impact studies were done using ‘Invasive Attributes’ (Sandilyan et al., 2019). The spread and invasiveness, range extension studies of IAS in DRF were studied using the data provided in different regions of the country [8-13].

In DRF a total of 144 Invasive Alien Species belonging to 130genera of 51 families were recorded. Out of these 3 are Pteridophytes and the remaining 141 species are Angiosperms. Among these, 59 herbs (41%), 23 shrubs (16%), 38 trees (28%), 12 climbers (8%), 5 Lianas (4%), 6 Climbing Shrubs (4%) and one species (1%) is a parasite (Figure 1) (Table 1). The species are distributed throughout the forest from lower elevations of 300 m to higher elevations of up to 1500 m. In the documented alien flora Fabaceae members are the dominant invasive species with 27 species, followed by Asteraceae with 11 species, Malvaceae with 8 species, Apocynaceae and Lamiaceae with 6 species each which is then followed by Asparagaceae and Convolvulaceae with 5 species each.

Of the documented IAS, 53species show different medicinal uses (28%), 32 tree species are harvested for timber (17%), 18 species are edible with fruits or leaves used in local culinary (10%), 15 species were introduced for ornamental purposes (8%), 12 species hold regional cultural values and are used in local festivities (6%), 8 species show high economical value by providing raw materials such as resins, and plant parts for pharmacy and biofuel (4%). Another 51 species have miscellaneous uses (27%) (Figure 2) (Table 1).

Three main attributes of ‘ecological impacts’ are given, namely, Invasiveness including IE - Invasive Elsewhere, RMS - Rapid Multiplication and Spread in Different Ecosystems, MMR - Multiple Modes of Reproduction, and MMD - Multiple Modes of Dispersion, Impacts including B1 - affecting ecosystem functions and services, B2 - biodiversity loss, and B3 - economic loss and health hazard (human and wildlife), and Invasion areas (Continues spread) including RE - Range Extension. The IAS was assigned respective attributes based on field observations and relevant literature. Among the documented IAS 114 species are invasive elsewhere, 115 species show rapid multiplication and spread in different ecosystems, 35 species show multiple modes of reproduction, and 65 species show multiple modes of dispersion. 105 IAS were reported to be affecting ecosystem functions and services, 56 IAS to be causing biodiversity loss and 81 species to be causing economic loss and health hazards to either humans or wildlife or both. 111 IAS shows continuous spread in DRF with range extension (Figure 3) (Table 2).

The IAS are ought to compete with the native species for nutrition, light, and hence affects the regeneration capacity of native species. Hybridization of alien plant species with native species causes gene mixing leading to reduced disease resistance in native plants. Allelopathic interaction of IAS impacts the fertility of soil and degradation of the native species. Of the documented IAS Jacaranda mimosifolia D.Don (Bignoniaceae) is an IUCN Red Listed as Vulnerable (VU) tree species [14]. The tree species was introduced as an ornamental plant which eventually was used for timber by the local villagers around the DRF. Many such species were either introduced for aesthetics or came to the study area by accidental movement through man or wildlife and now are invasive within native species.

Among the documented IAS 79.16% of species are invasive elsewhere, 79.86% of species show rapid multiplication and spread in different ecosystems, 24.30% of species show multiple modes of reproduction, and 45.13%of species show multiple modes of dispersion. 72.91% IAS was reported to be affecting ecosystem functions and services, 38.88% IAS to be causing biodiversity loss and 56.25% of species to be causing economic loss and health hazards to either humans or wildlife or both. 77.08% IAS show continuous spread in DRF with range extension. Hence timely monitoring of the distribution pattern of IAS should be undertaken to successfully eradicate them and reestablish native species.

The authors are thankful to Karnatak University’s Karnatak Science College for academic support, Karnataka Science and Technology Promotion Society (KSTePS)- Karnatak Department of Science and Technology, GOK for fellowship funding, and the Karnataka Forest Department, Tumkur Division for their permit and support during the field studies.