Bees play a key role in maintaining ecological balance and nearly 78 to 94% of wild plants depend on bees for pollination (Ollerton et al., 2011). They also ensure food production as they are the key pollinators of many crops (Kremen et al., 2002; Klein et al., 2007; Corlett, 2010; Abrol et al., 2012; Garibaldi et al., 2013; Ghosh & Jung, 2016). Bees occupy a variety of terrestrial ecosystem and are found on all the continents except Antarctica. About 25,000 bee species have been identified so far, distributed across 11 families (Ascher & Pickering, 2020; Orr et al., 2021). Most of the species are solitary, with no social organization. However, honey bees (family Apidae) are highly evolved eusocial bees (Wilson & Hölldobler, 2005). Adaptation of bee species to their immediate environment and to changes in the environment is an important aspect of their distribution. Bees have exhibited high degree of adaptations to cope with diverse environmental conditions (Vorhees et al., 2013). Species cope with such changes through migration, plasticity, and adaptive evolution (Williams et al., 2008). Honey bees belonging to the genus Apis are found throughout the world and have adapted to a wide range of environmental conditions and geographical locations. (Hargasim, 1974; Sihanuntavong et al., 1999; De La Rúa et al., 2000; Takahashi et al., 2007; Gupta, 2014; Kükrer et al., 2017; Agra et al., 2018). Engel (1999) and Otis (1996) have reported a total of nine species of which eight are native to Asia (Radloff et al., 2010; Yu et al., 2019), three of them, namely giant honey bee (Apis dorsata), Asian honey bee (Apis cerana), and dwarf honey bee (Apis florea), are native to the Indian subcontinent.
Bees are quick to respond to changes in the environment, they are highly adaptable insects that have evolved a wide range of morphological (Cardinal & Packer, 2007; Vinutha & Naresh, 2022), behavioural (Noll, 2002) and physiological adaptations (Kapheim et al., 2012; Vorhees et al., 2013) to thrive in diverse environments and several coevolutionary traits can be seen among such geographically adapted communities (Thompson, 1999). The dynamic interaction of bee species with the flora and environmental conditions of an area is reported to be a major force in the process of adaptive diversification (Ehrlich & Raven, 1964; Thompson, 2013), Among many taxa eusocial honey bees have evolved into many geographical subspecies and ecotypes mainly as a result of their adaptation to a range of geographical conditions (Ruttner, 1988; Meixner et al., 2010). Five ecotypes of the Asian honey bee (A. cerana) are reported to be widely distributed across Asia (Radloff et al., 2010). The subspecies and ecotypes of the honey bee differ genetically as a result of their adaptation to specific geographical area (De La Rúa et al., 2000; Ma et al., 2019). Additionally many studies have reported genetic differentiation in Apis species in response to changes in the geographical location (Smith, 1991; Arias & Sheppard, 1996; Smith et al., 2000; Tanaka et al., 2001). Factors such as elevation, conditions in deserts, availability of water in mountains, and the geographical isolation of species between islands and continents have resulted in genetic differentiation in honey bees (Smith et al., 2000; Songrarn et al., 2006; Warren et al., 2015). The genetic diversity of geographical populations can reflect important information on the phylogenetic origin, population dispersal, the gene pool, and the mating system operating within the populations (Allendorf et al., 2007; Teichroew et al., 2017) which also provide information on their response to influencing conditions within an ecosystem (Thompson, 1999; Hatjina et al., 2014; Chen et al., 2018).
Urbanization and urban expansion have resulted in the conversion of natural habitats into manmade landscapes, making urban habitats increasingly significant as terrestrial ecosystem. However, this transformation poses a negative consequence on bio biodiversity. Many bee species have experienced significant declines globally due to the intentional changes in land use associated with urbanization and other human activities (Goulson, 2008; Cameron et al., 2011; Zattara & Aizen, 2021). Climate change and anthropogenic activities resulting in fragmentation and degradation of habitats and the growing intensification of agriculture have led to changes in the species distribution, which intern have changed the physiology, phenology, and the genetic composition of bees (Karan & Parkash, 1998; Cowling & Pressey, 2001; Gilchrist et al., 2004). However, urban green spaces play a crucial role in urban ecological diversity worldwide. Many urban green spaces across the world are crucial to urban ecological diversity (Modi & Dudani., 2013; Müller, 2013). Similarly, several studies also reflect the shift in the bee diversity in the manmade fragmented urban green habitats (Bhatta & Naresh 2020, 2021; Prendergast et al., 2022) than the natural vegetation (Thompson et al., 2003). Purpose-built areas covered with semi-natural green networks such as parks, gardens, and avenue trees dominated by ornamental trees and a mix of native and exotic plant species, despite being part of the ‘concrete jungle’, have become an integrated system of aesthetic and biological importance (Good, 2000; Meurk et al., 2013). Bees have demonstrated resilience and ability to adapt to manmade urban area despite many ecological and environmental challenges. Urban habitats offer certain advantages for bees, including floral diversity, nutritional resources, connectivity, and nesting opportunities in manmade structures. These factors make urban habitats potential hotspots for conserving bee diversity and facilitating the recovery and restoration of bee species (Hinners et al., 2012; Bhatta and Naresh., 2021, 2022).
By recognizing the challenges of urban habitats and implementing conservation strategies, it is possible to mitigate the decline in bee diversity and support the survival of important pollinators. Fragmentation of natural habitat and increased human disturbances can result in geographical isolation of bee population affecting the rate of gene flow and genetic equilibrium due to inbreeding in bee population (Cao et al., 2007; Johnson and Munshi-South, 2017). Additionally, exotic floral community and altered floral phenology in the urban habitat can affect the physiology, foraging behaviour and reproductive success which collectively exert strong selection pressure on bees (Arien et al., 2018; Brant et al., 2022).Snice genetic pool of bees are evolving due to their adaptation to environmentally and anthropogenically induced changes (Louveaux et al., 1996) genetic analysis of urban bee populations can through light on the effect of landscape features on the population structure, and genetic diversity of urban populations (Manel et al., 2003). Such understanding can also supply useful insights into the underlying strategies that bees adopt in response to the changes (Radloff et al., 2010; Teichroew et al., 2017). Successful planning for species conservation in manmade habitat depends on preserving the genetic diversity of native species. Therefore, mapping of genetic diversity establishes the fitness of individual taxa, pattern of migration, gene flow, genetic selection in an ecosystem (Avise, 1995). Additionally, the genetic studies provide valuable insight into the status of their adaptability in the changing manmade habitats (Allendorf et al., 2010). Therefore, understanding the genetic diversity of geographical species their response to urban land use changes can contribute to the protection and conservation of bee species (Manning et al., 2006; Dellicour et al., 2015). Molecular markers (DNA markers) are extensively used as standard tools for genetic analyses to understand genetic diversity, population structure, and the evolutionary origin of native species. Microsatellite DNA analysis is considered highly useful in determining genetic diversity, genetic variation, and population structure (Franck et al., 2001; Techer et al., 2015). Microsatellite markers also provide valuable information on phylogeny and phylogeography among different populations within a species, which can be adopted for the conservation of bees (Chapman et al., 2008; Kence et al., 2009).
Science bee are the focal point of terrestrial ecosystem and food security, their conservation is of great concern (Dicks et al., 2013). Establishing genetic diversity and phylogeograpy of such pollinators and their long-term conservational approach in urban green areas is the need of the hour especially in a fast-developing country like India with an unprecedented urbanization and urban expansion. Though studies have suggested the increasing species diversity in Indian cities, their genetic diversity and conservational concern of such urban adapted species are poorly documented. It was against this background that the present study sought to understand the effect of urbanization by comparing the genetic diversity and phylogeography of A. cerana indica), native honey bee populations from three different habitats, namely an urban green space, the rural, and a natural but preserved forest. The effect was studied in terms of genome wide microsatellite allelic polymorphism, genetic diversity; genetic association, genetic differentiation, and population structure, the genetical relations between bees from the urban area and non-urbanized areas were examined to establish the effect of fragmented urban habitat on bees.