Influence of land use types on plant – pollinator interactions in an urban landscape
Pollination is the basis of sexual reproduction in plants and hence crucial for thriving of life on earth. It is carried out mostly by biotic agents. About 60%-90% of wild plant species require animal pollinators for successful pollination. Pollinator in return is rewarded with nectar, pollen, fragrance and other floral resources. Various anthropogenic activities led to changes in the land use and landscape structure through habitat conversion, fragmentation, constructing roads, boundary separating two vegetation, intensive monoculture cultivation, degradation, etc. Influence of change in land use and landscape structure on pollinators, their target plants and interaction at individual, population, community is immense. Land use change alters the distribution of both floral and nesting resources. The study of influence of land use types on plant – pollinator interactions in an urban landscape is the need of the hour. Growing urbanisation has demanded a study to understand natural responses of pollinators with respect to plant species in a given area. Therefore, the present study attempts to understand the plant - pollinator interaction with respect to the different land use types and study the floral visitation, their visitation frequency, and foraging behaviour.
Keywords: urbanisation, anthropogenic activities, floral visitation, visitation frequency, foraging behaviour
|LUT||Land use type|
|LSE||Land use Element|
|IVI||Importance Value Index|
INTRODUCTION AND REVIEW OF LITERATURE
Urbanization can be described as the proportion of total population or area in cities or towns or the increase of this proportion over time. So, it represents the level of urban development relative to overall population, or it may represent the rate at which the urban proportion is increasing. Plant–pollinator interactions are affected by global change, with largely negative impacts on pollination and plant reproduction (Harrison and Winfree 2015). Urban areas provide a unique and productive study system to understand the impacts of urbanization on plant–pollinator interactions.
Urbanization is a measure of development in modern world. However, no regional natural creatures are considered during the same. All inhabitants in the urban area depend other areas for getting their resources supply. There is hardly any space left in metro cities where development is happening in a faster rate. Exposed soil area is getting reduced as widening of roads, tiling of courtyards, etc. are getting increased. Natural habitats in cities that are fast approaching a metro status are getting wiped out rapidly.
Kochi is an urban agglomeration centred around the city of Kochi, in Ernakulum district, Kerala, India. With a population of more than 2.1 million within an area of 440 km², it is the largest and most populous metropolitan area in Kerala. Rapid industrialisation, infrastructure development, construction of roads and bridges, rail corridor, metro, smart city project etc make the city of Kochi a suitable area to study the effect of urbanization on plant- pollinator interaction.
Destruction of natural habitats has resulted in replacement of native plants with exotic species and hence led to changes in the insect populations pool (Grimm et al. 2008). Anthropogenic habitats provide more opportunities for conservation of species for the purpose of survival of many species (Gascon et al. 1999). Hence city-dwelling species provides greater opportunities for researchers to demonstrate the importance of conservation to society. Studying plant-pollinator networks is important to understand the links between plant and pollinator communities and the consequence of species loss (Fontaine et al. and Biesmeijer et al. 2006).
Land Use Types
Land use is the function or functions that humans apply to the land available to them. Any kind of permanent or cyclic intervention of a land can be referred to as land use. Land use is an emerging socio-economic activity wherein a region of one major specific purpose utility may be converted into another land for general purpose utility. The process of urbanization is characterized by development of areas containing fragments of open space such as open spaces, reserves, parks and gardens (Harrison and Winfree 2015). Hence changes in different land use types, human trend and movement modulate the process of urbanization.
In India, broad land use classes include -Arable land, area under forest, plantation, built-up and non-agricultural lands, scrub and pastures, wasteland, wetland and water bodies and snow fields and glaciers. The land use types taken into consideration for the study are non- agricultural lands. These includes lands adjacent to urban settlements, buildings, roads, railways, lake side and other land put to uses other than agriculture.
Influence of Urbanization on Biodiversity
Urbanization has resulted in increasing homogenization of the biodiversity as well as extinction of species (Anibal et al. 2006). Habitat alteration is another effect of it which is causing threat to human civilization and to the other organisms. Humans are modifying the globe at an unprecedented rate, leading to huge irreversible losses of biodiversity (Newbold et al. 2016). Human impacts such as fragmentation, degradation and destruction of natural habitat and creation of new anthropogenic habitats have resulted in modification of landscape and hence the shift to urbanization.
Influence of Different Landuse on Biodiversity
Importation of vast resources of energy and materials from the local natural environment to cities caused a disequilibrium condition and resulted in homogenization of physical environment for the purpose of fulfilling only human needs. Ever expanding cities in the planet increases biological homogenization with similar in structure and similar species. Further, cities are expanding worldwide in almost every locality. The world’s population is projected to increase by more than one-third over the next 30 years, adding two billion people with almost all expected growth in the world’s population is concentrated in urban areas (United Nations 2004). Many studies show that the construction and expansion of towns and cities promote the loss of native species and their replacement by non-native species.
Spatial patterns of the replacement of native with non-native species also happened as a result of urbanisation (Mckinney 2006). Increasing intensity of urban activity i.e. the shift to more urban colonies, development of roads, railways and other urban components causes non-native species to increase in abundance and species richness leading to declining of native species. Disturbance promotes the establishment of non-native species (Antonio and Meyerson 2002).
Pollination can be defined as the successful transfer of pollen grains from anther to stigma of same or a different flower. It is an ecosystem function that is required for sexual reproduction of flower. Pollination takes place by two means- self -pollination (either between an anther and a stigma of the same flower, or different flowers on the same plant species) and cross pollination (between anthers and stigmas of different plants of the same species Pollen transfer in plants occur with the aid of animals to a great extent and a small proportion with the help of abiotic agents such as wind, water , etc. (Shivanna 2014). Plant-pollinator relationships are one of the major areas of animal- plant interaction (Kearn et al. 2007). Insects and other animals pollinate over 300000 plant species, comprising 87.5% of the world’s total flowering plants (Ollerton et al. 2011).
Based on the type of pollinators, three different types of pollination systems have been identified; generalized pollination system, specialized pollination system and super specialized pollination system. Generalized pollination system occurs in flowers with exposed anthers and pistil, for eg- mustard, apple and rose (Shivanna 2016). Pollination system occurs in flowers which have complex to varying degrees of floral resources, such as those with hidden floral rewards either at the bottom of corolla tube or in spurs of various length, for eg.- Balsam, Angraecum sesquipedale orchid (Shivanna 2016). In super specialization, one plant is visited by just one pollinator, eg.- Ficus and Yucca.
On the basis of agents involved in pollination, there are five major types of pollination identified; anemophily (wind), entomophily (insects), hydrophily (water), ornithophily (bird) and zoophily (other animals) (Shivanna 2016). Further, based on the origin of pollen involved in the process, it is classifies into three major types: autogamy – transfer of pollen grains from anther to the stigma of the same flower, geitonogamy- transfer of pollen from the anther to the stigma of another flower of same plant or of another plant of same clone and xenogamy – transfer of pollen from the anther o the stigma of different plant (Shivanna et al. 2014).
Pollination by means of animals is the prevailing and most successful mode of pollination among several types. Among animals, insects are considered to be the major floral visitors and pollinators, among which, bees (Hymenoptera), wasps (Hymenoptera) and ants (Hymenoptera), beetles (Coleoptera), flies (Diptera), butterflies and moths (Lepidoptera) and Thrips (Thysanoptera) are the major groups. Bats and birds are also important pollinators among animals other than insects. Pollination can be nocturnal (Moths, bats and birds) or diurnal animals depending upon the flower activity and visitor behaviour. Cockroaches, reptiles, squirrels and even snails are reported as pollinators in some plant species (Shivanna 2016). However, recently several studies revealed that several other groups of animals are also involved in pollination. One such recent emerging pollination is ants. Ant pollination is reported to be restricted to herbaceous annular plants but recently ants were found to be the major pollinator for a tree species as well (Kuriakose et al. 2018). Plant–pollinator interactions are largely mutualistic; they result in reciprocal benefits to both the partners. It is a form of “biological barter” and involves exchange of resources of the plant such as pollen and nectar with the services of the pollinator (Ollerton 2006).
Pollinators and Their Services
Pollinators provide valuable services for multitude of crops as well as reproduction of wild plant species. Pollinator services provided by insects in urban areas include pollination for urban food production and pollination of native plant species that grow in urban areas. Bees, wasps, butterflies, flies, moths etc are important pollinators of vegetations in an urban gradient. However, bees play the most significant role in successful pollination in human-dominated habitats. Plant-pollinator interaction is strongly influenced by variety of bees in an urban gradient. According to Banaszak and Zmihorski (2011) ‘The urbanized landscape can act as a filter for the bee community since some specific ecological traits facilitate colonization of the city centre’.
Some of the prominent bee families found are: Apidae, Megachilidae, Andrenidae, Halictidae and Colletidae. Important species of bees belonging to these families are Apis dorsata, Apis cerana indica, Apis florea, Apis mellifera, and Trigona iridepennis. Wasp and bees are found in urban environment occupying different microhabitats (eg- walls, roofs, ceilings etc) (Fowler et al. 1983). A study in brazil found that the abundance of advanced eusocial bees (i.e. stingless bees) which are more dominant species, was directly affected by the loss of vegetation cover and the increase of buildings associated with urbanization. It also had a negative effect on the abundance and species richness of advanced eusocial wasps such as Trigona. Nesting sites are getting destroyed due to urbanisation and therefore, pollinator decline happens and consequently to the services it provides.
Influence of Urbanization on Pollinators
Changes in land-use and landscape structure influences pollinators, target plants and their interactions at individual, population and community scales. The loss and fragmentation of natural habitat reduces gene flow and re-colonization rates resulting in lowered persistence not only of subpopulations but also of meta -population networks (Hanski 1998, Zayed et al. 2005).
Diversity and abundance of wild-insect pollinators have declined in many agricultural landscapes. Managed and wild bees are declining in many regions of the world, due to a mix of parasites, diseases, habitat loss, and pesticides (Bartomeus et al. 2013, Goulson et al. 2015, Potts et al. 2016). Effects of urbanization on insects in general and pollinators in particular remain ambiguous and are not comprehensively understood (Threlfall et al. 2015).
Habitat loss and fragmentation can change flower visitation rates and pollination success through changes in pollinator foraging behaviour or through population-level effects on pollinators. It may also alter pollinator visitation to plants by causing declines in pollinator populations and changes in pollinator community composition. Open flower plant species and their specific flower-visitors are especially sensitive to increasing urbanisation (Geslin et al. 2013).
Urban areas offer unique ecological environment with warm climate and high habitat diversity leading to diverse nesting and foraging opportunities (Ahrne et al. 2009). For bees, urbanization may results change in the availability of nesting sites as well as the quality and accessibility of food plants. It can also affect bees through habitat fragmentation (McIntyre and Hostetler 2001, Cane 2005, Frankie et al. 2005, Ahrne et al. 2009). Regularly disturbed habitats in an urban environment creates communities which are dynamic and development of some species-specific traits may facilitate existence of pollinators and urbanization may affect different species differently. Urbanization tends to alter species composition from that of the surrounding landscape. (Bankowska 1980, 1981, Niemela et al. 2000, McIntyre et al. 2001).
However, Cibicka and Zmihorskiin (2011) have reported that diversity of the bee community can remain relatively stable across an urban gradient. Furthermore, plant species richness is usually higher in urban than in rural areas (Kuhn et al. 2004)
Influence of Different Land Use Types (LUT) on Pollinators
The role of different LUTs on pollinators is poorly understood, but it plays an important role in structuring the diversity of pollinators observed in comparative to the rural pollinator diversity. Changing human population centres, denser pattern of homes are examples of changing land use types. Species diversity did not show a clear trend along the urban gradient. The specific impact of urbanization on species richness will vary, depending on many geographical, historical and economic factors that are unique to each land use types of the city (McKinney 2008). For conservation of local fauna and biodiversity, green areas within the city has become a very important place (McIntyre and Hostetler 2001, McKinney 2002, Cane et al. 2006).
The massive disturbances created by city growth not only destroy the habitat of native species but they create habitat for a relatively few species that are adapting to urban and suburban conditions.This process of replacing localized native species with increasingly widespread non-native species promotes biotic homogenization (McKinney and Lockwood 2001). ‘‘Edge species’’ are the species which are considered to be the urban adapter adapted to forest edges and surrounding open areas (Adams 1994).For animals, another key factor is vegetation, which becomes less common, with more non-native species toward the urban core (Kowarik 1995).
Pollinators with narrow habitat requirements and low mobility has resulted in specialist pollinators and declination of the generalists. While the diversity of pollinators in urban environments has been addressed in a range of recent studies, many of these focussed on a classical range of urban green spaces (e.g., cemeteries, gardens, parks).Urban areas also include flower rich green areas that can provide forage for a high diversity of pollinators (Frankie et al. 2005, Gaston et al. 2005, Loram et al. 2007).
Significance of the Present Study
Effects of urbanization on insects in general and pollinators in particular remain ambiguous and are not comprehensively understood (Threlfall et al. 2015). Urban climate conditions are considered similar to the changing global climate conditions, therefore, studying urbanized areas as small scale experiments, or modals, of global climate change (Ziska et al. 2003) will help in envisaging the bigger problems threatening human existence and survival of other organisms. Deeper understanding of how cities can help mitigate biodiversity loss is urgently needed, especially for pollinators (Cibicka and Zmihorski 2012,Baldock et al. 2015).
The diversity and abundance of plant communities that appears in clumps with single or few species in different urban habitats, has been associated with land use and urbanisation gradients (McDonell and Pickett 1990). Another challenge of urban growth is replacement of native species by ‘weedy’ non-native species, which results in biotic homogenization that threatens to reduce the biological uniqueness of local ecosystems (Blair 2001). This homogeneity in diversity of plants increases towards the centres of urbanization, while the number of native species decreases. Hence this project focusses on studying the effect of changing species richness pattern and its influence on the pollinators.
Urban environments allow researchers to identify habitat fragments more clearly than in many other environments. Physiological, behavioural and reproductive processes that characterize the plant–pollinator interactions and change in it due to global changes owing to urbanization can be studied in a broader scale. ‘Urban land use is a driver of global change in its own right, and therefore, studies on specific urban drivers or combinations of drivers are needed to predict the effects of future urban expansion, which is expected to increase globally by 285% between 2000 and 2030’ (Seto, Guneralp and Hutyra 2012).These raises the significance of studying the effect of urbanization on plant- pollinator interactions in an urban area.
Objectives of the Study
1. To study the pattern of distribution of vegetation in different Land Use Types (LUT) in the urban landscape of Kochi.
2. To study the effect of different LUTs on pollinator diversity.
3. To identify different pollinators of plants in different LUTs and their visitation pattern.
MATERIALS AND METHODS
Study area: The study area selected was the city of Kochi in Kerala comprising different land use types as National highway, State highway, Pocket roads, Open Space (School/College garden), Railway tracks and Abandoned land. The period of study extended for two months ie. from 27 May 2019 to 26 July 2019. The study area lies between 9.93120 N and 76.26730 E with an elevation 0 to 10mm. Being a major port city on the south-west coast of India with an urban population of more than 2.1 million within an area of 440 km2, the growing urbanisation with rapid change in the land use types makes it an ideal place to study the influence of it on the plant and pollinator.
Selection of study area: National highway, State highway, Pocket roads, Open Space (eg. Open Gardens), Railway Tracks and Abandoned Lands were the land use types (LUT) selected for the present study. For roads, transects were laid on either sides. At least 10 quadrants in each transects were laid. For each land use three habitat are taken.
Selection of quadrants: Quadrant of size 2X2m2 was considered. Utmost care has been taken not to disturb the study area while laying the quadrate. Adjacent quadrats were kept at least 25 m apart from each other.
- Plants were identified upto species by using standard taxonomic keys, with the help of experts or using relevant online resources (eg. Efloraofindia, face book groups). In case if online resources were used, an expert opinion had taken before validating the identification. Number of individuals belonging to each species was recorded. Phenology of the flowering plant was marked with alphabetical code – A, B, C, D for 25%, 50%, 75% and 100% flowering intensity respectively. Number of pollinators visiting each species and number of visitations per bout was also recorded from 7:00 am to 1 pm.
- At least one specimen belonging to each morpho-species of floral visitor found during the study was collected by using a wide mouth bottle. It was stored in 60% alcohol for identification.
- Identification of bees were done by Dr. Jobiraj T, Assistant Professor, Department of Zoology, Government college, Kodanchery.
- Analysis: The data collected were put into an Excel sheet. These data are arranged on the pivot table as required. Statistical analysis including Pearson (r) and Spearman’s D test were performed to find significant difference between each attribute.
Correlation between variables are carried out using two correlation statics methods:
1. Pearson ( Linear r): The Pearson product-moment correlation coefficient, also known as r, R, or Pearson's r, is a measure of the strength and direction of the linear relationship between two variables that is defined as the covariance of the variables divided by the product of their standard deviations. This is the best known and most commonly used type of correlation coefficient; when the term "correlation coefficient" is used without further qualification, it usually refers to the Pearson product-moment correlation coefficient. Pearson correlation coefficient is a measure of the linear correlation between two variables X and Y, developed by Karl Pearson .
2. Spearman’s D : Spearman's rank correlation coefficient or Spearman's rho, named after Charles Spearman is a nonparametric measure of rank correlation . It assesses how well the relationship between two variables can be described using a monotonic function. The Spearman correlation between two variables is equal to the Pearson correlation between the rank values of those two variables; while Pearson's correlation assesses linear relationships, Spearman's correlation assesses monotonic relationships (whether linear or not).
There are two methods to calculate Spearman's correlation depending on whether: (1) data does not have tied ranks or (2) data has tied ranks. The formula for when there are no tied ranks is (Formula 1):
where di = difference in paired ranks and n = number of cases. The formula to use when there are tied ranks is (Formula 2):
Some data were log-transformed before and distribution was checked graphically using diagnostic plots. Location was considered a random effect to meet the requirements for testing samples. Dominancy of the species in an LSE is measured using Importance value Index (IVI).
Study Sites: The different land use types used for the purpose of studying plant -pollinator influence was –
Open space: Open space is any open piece of land that is undeveloped (has no buildings or other built structures) and is accessible to the public. Open space can include: Green space (land that is partly or completely covered with grass, trees, shrubs, or other vegetation). Green space includes parks, community gardens, college gardens and playground.
The open space considered for the study in this project were School / College Gardens. The field area i.e. the vegetation of Sacred Heart College Ground College, Maharaja College Ground and Indian Maritime University Ground were studied. The common species of plants found in these grounds were Kyllinga brevifolia, Cleome rutidosperma, Mimosa pudica, Spermacoce ocymoids and Scoparia dulcis. Since college ground are area with human influence, the vegetation growing in it is constantly under disturbance.
Abandoned Land: Abandoned lands are the area which is undisturbed of human influence or vacated place which has been totally taken over by the wild vegetation. Three replicated of Abandoned land i.e. in Thevara, Maradu and Tirunettoor were studied. Since its undisturbed area, many shrubs have taken over the field area and hence influenced the type of vegetation. Shrubs like Lantana camara, Desmodium triflorum and Clitoria ternatea were abundantly found which is unusual in the other land use types.
National Highways: National Highway 66 and National Highway 85 and National Highway 183 criss -crosses city of Kochi. Vegetations across the two transects of National Highways passing through Naval Base, Vathuruthy and Kundannoor were studied. National highways as a land use type are demarcated by the wider length of road which completely separates vegetation across the both sides. Cleome, Alternanthera, Euphorbia are the common plant species found.
State Highways: State highways are less wide than the National Highways and hence the distance between the two transects are less. This distance between the two transects influence the pollinators and plant species across it. State Highways in Kannangatu, Shanthinagar and Maradu were the three study sites chosen. Phyla nodiflora, Boerhavia diffusa, Cleome sp., Mimosa pudica are the common plant species recorded.
Pocket Roads: Pocket Roads are roads which are narrow. These are least maintained roads and comparatively smaller than the other roads. This allows the vegetation as well as pollinators across two transects to interact. It is also influenced by the other natural habitats around it. It is least disturbed as compared to National Highways and State Highways. Kundannoor, Maradu and Kannangattu were the sites of study. Cyanotis, Desmodium triflorum, Eclipta prostrata etc were some of the plant species recorded in the pocket roads.
Railway Tracks: Vegetation along the Railway Tracks holds an important place for conservation of biodiversity. This Land Use Type is constantly under disturbance of human influence and also many diverse species of plant have been recorded from it. Substantial numbers of pollinators also added up to rich diversity of along the railway tracks. Study sites considered were Railway Tracks at Maradu, Tirunettoor amd Vathuruthy. Microstachys chamaelea and Acalypha sp. are some of the distinct species found abundantly in this LUT.
The locations of different land use area and its coordinates are mentioned in Figure 1. Map-1 shows the Google Earth image of different study sites for the present study.
Distribution of Vegetation in Different Land Use Types
A total of 36 transects were laid with 10 quadrates each. Altogether there were 40493 individuals belonging to 36 species of flowering plants recorded during the study. In all quadrates plants were growing mostly in clumps. There were six types of land use types identified in Kochi. The land use types are-Abandoned, Open space, National Highway, State Highway, Pocket Roads and along Railway tracks. A total of 14 species of insect pollinators were found in these different land use types.
Abundance of plant species in different land use types
Among the LSE’s studied, state highway has the maximum abundance of plant species with a mean abundance of 44.80 (±33.77, N=30) followed by Railway Tracks and National Highway with a mean abundance of 36.09 (±30.85, N=30) and 32.41 (±22.57, N=30) respectively.
Pocket road has the least abundance. The difference in the abundance of species in different land use types is not statistically significant. Standard deviation recorded of the data of Open space is higher than the mean (Figure-2).
Species richness and abundance across different land use types
Alternanthera ficoidea was recorded with the highest IVI value (20.06) followed by Cleome viscosa (17.06) and Tridax procumbens (15.96), while Eclipta prostrata recorded the least IVI value (5.08) (Table 1).
|Sl. No.||Scientific Name||Family||IVI|
Altogether 36 species of plants were found in six land use types. Maximum diversity was reported from Railway tracks followed by State highway and Open space. Pocket roads had the least plant diversity. (Figure-3). Other LSE types were more or less common in terms of plant diversity and abundance.
Abundance and Visitation
Phyla nodiflora is the species that received maximum visitation followed by Kyllinga brevifolia and Justicia simplex. Whereas, Momordica charantia, Eleucine indica were found to be the least visited plant species (Figure-4).
The maximum number of individuals and visitation was recorded from LSE State highways (Figure-5). The abundance and visitation are statistically positively correlated with Spearman’s correlation (D) analysis (p = 0.002 i.e.< 0.05). From matrix data of Spearman’s correlation (D) of visitation by all insect pooled data across different land use types suggested that visitation at Railway Tracks and National highway were significantly positively correlated. The correlation between abundance and visitation in State highway and Abandoned LSE’s was also found to be of significant positive correlation. (Table-2 and Table-3.)
|Abandoned||National Highway||Open Space||Pocket Roads||Railway tracks||State Highway|
|Land Use Types||Abandoned||National Highway||Open Space||Pocket Roads||Railway tracks||State Highway|
Maximum visitation of insects to flowers in the study area has been recorded during 08.00 to 09.00hrs and gradually decreased towards noon (Figure-6).
Some of the common visitors are shown in the Plate 1 and Plate 2. Correlation between abundance and rate of visitation of pollinators in different land use types has been plotted in Plate-3.
Rate of Visitation of Different Pollinators
About 304 number of individuals of insect specimens were recorded from the field. Out of which, there were 266 number of individual of bees belonging to 10 bee species were found. Other than bees, pollinators like butterflies, fly, moth and wasp were recorded. The most abundant species among floral visitors was Apis cerana with 84 recorded individuals, which therefore accounted for about 27.63% of all pollinators. The different species of bees recorded were Gnathonomia sp., Amegilla sp., Halictus sp., Apis mellifera, Ceratina smaragdula, Crocisaspidia sp., Hoplonomia sp. and Tetragonula iridipennis.
Apis cerana was the most important floral visitor with maximum visitation in Abandoned LSE followed by Gnathonomia sp. and Apis mellifera. In National Highway LSE, Gnathonomia sp. was the floral visitor with maximum number of visitations followed by Apis cerana and Apis mellifera. Whereas Apis cerana was the most frequent visitor in open space LSE followed by Apis dorsata and Gnathonomia sp.. In Pocket roads, Apis cerana had the highest rate of visitation followed by Gnathonomia sp. and Hoplonomia sp. In Railway tracks, Gnathonomia sp. followed by Apis cerana and Ceratina smaragdula and in State highway Apis cerana followed by Gnathonomia sp. and Halictus sp. respectively were the most frequent visitors (Plate-4).
Urban areas have extremely high spatial habitat heterogeneity produced by many different land uses at small spatial scales (Thompson et al. 2003). Several studies have reported that different land use patterns may increase species diversity by increasing habitat diversity and hence result in greater species richness (Zerbe and Cierzniak 2003). As per observation, State Highways has the highest number of abundances of plant species but it is almost similar to National highways and along railway tracks. This is because increase in distance between two replicates of a transects results in diverse plant species from one another and in National Highways and State Highways the distance is wider comparatively to the other land use types. Pocket roads which contains least gap between two replicates results in homogeneity of species and the abundance is comparatively lesser.
But overall, there is no clear difference in the abundance pattern of the different Land Use Elements type in urban landscape as urban habitats tends to be very similar and similar human activities in land use types produce similar structure as reported by McKinney, Clergeau, and Savard 2001.
Human influence and disturbances promote non-native species (Antonio and Meyerson 2002). Many non-native species such as Wedelia chinensis, Alternanthera ficoidea, Lantana camara were recorded during the study in different land use types and hence also has an influence in the abundance of other plant species.
Alternanthera ficoidea, Cleome viscosa, Tridax procumbens, Mimosa pudica, Euphorbia hirta and Cleome rutidosperma are the most commonly occurred species in different land use types. Importance Value Index (IVI) value of the plant species found in different land use types resulted highest IVI value for Alternanthera ficoidea followed by Cleome viscosa, Tridax procumbens and Mimosa pudica. This is because these plant species were recorded growing in clumps and Alternanthera forms mat like structure with a massive underground root system spreading over a larger surface.
The maximum diversity was reported in Railway tracks followed by state highways and open space. This is relatable to the disturbance caused to the Land use elements. More heterogeneity is recorded in LUTs where the human interaction or influence is more. Since vegetation along the railway tracks are constantly under disturbances, more diverse plant species adapting to the land use were found.
Peak time recorded for most number of visitation of bees is between 8:00 AM- 9:00AM. This is the time when both smaller as well as larger bees were found foraging since the environment remains humid but higher intensity of sunlight in the noon makes the bees forage less. Further, most of the flowers were active at this time with maximum pollen and nectar in offer. The positive effect of increasing temperatures on nectar volume is masked by a stronger, negative effect of decreasing air humidity and soil moisture throughout the day (Muniz et al. 2013) and hence bee abundance decreases towards the noon. Phyla nodiflora being grown in clumps received maximum bee visitation. The flower being attractive provides forage to large number of bees specially Apis cerana. Kyllinga brevifolia and Justicia simplex respectively also has the highest visitation rate accordingly.
Plant species richness is usually high in an urban gradient (Kuhn et al. 2004). State Highways has the highest number of individual and visitation. This can be justified by the presence of diverse vegetation along the State Highways and pollinators look for heterogeneity. The presence of other habitat such as maintained places for the growth of vegetation and walking pave way along the state highways are some other factor may cause more abundance and visitation rate. State Highways were followed by Pocket roads which show high abundance and visitation. Pocket roads are the least maintained and narrower. Also other natural habitat close to the pocket roads has influence on the abundance of pollinators and their visitation. Presence of other habitat results in easy pollination and alternative pollination choices and abundance in such cases will be more. Abandoned area being conquered by big trees, also influence the abundance as it is monodominant. The clumpiness become homogenate in the abandoned area.
It was found that visitation at Railway tracks and National Highways were comparable. This is due to the vegetation characteristics such as similar composition, timing of flowering, etc. along Railway tracks and National Highways, they are constantly under disturbance which resulted in significant positive correlation between visitation and abundance.
Apidae was the most representative family mainly due to the eusocial behaviour, the longevity of the colony, and the generalist foraging (Roubik 1992). Apis cerana and Gnathonomia sp. were found to be the most common bee species in different Land use Types. Body size of these species also responds positively to urbanization (Wray et al. 2014). They have ability to withstand higher temperature and forage scarcity and are non-nomadic in nature. These bees possess populous colonies and communicate the location of food sources to other workers (Lindauer and Kerr 1960), permitting the meeting of a large number of individuals from the same colony. The observations from the present study supports reports of Banaszak-Cibicka and Mihorski (2011) that diversity of the bee community can remain relatively stable across an urban gradient.
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At the outset, I wish to express my indebtedness to Dr. Giby Kuriakose, Assistant Professor Department of Botany Sacred Heart College Thevara, supervisor guide for his sustained encouragement, valued suggestions and unparalleled patience without which this project work would not have been materialized.
My profound thanks are due to Fr. Dr. Jose John, Head of the Department, Department of Botany, Sacred Heart College, Thevara, for his adequate support for the project work. I express my sincere gratitude to all other teaching faculties of Department of Botany Sacred Heart College Thevara for their suggestions and encouragements.
I owe much to Fr. Dr. Prasanth Palackapillil, Principal, Sacred Heart College, Thevara for rendering all required facilities for the completion of this work.
I also sincerely express my thanks to Dr. Jobiraj T., Assistant professor, Department of Zoology, Government College, Kodanchery for his immense help in identification of pollinators and Dr. Shyam Kumar, Department of Botany , Maharaja’s College and Dr. K. N. Krishnakumar, Principal, Maharaja’s College, Ernakulam for permitting me to carry out part of my field studies in the college campus.
I am grateful to Mr. Manu S. Mohan and other non-teaching staffs of the Department of Botany who have provided support and help during the course of work.
Lastly, I would like to express my sincere gratitude from the bottom of my heart to my beloved parents, brother and all people associated with my work for their unstinted support which was indeed instrumental in the successful accomplishment of this Summer Fellowship.