Abstract
AbstractUrbanization affects pollinator diversity and plant–pollinator networks by changing resource availability locally and in the surrounding landscape. We experimentally established (N = 12) standardized plant communities in farmland, villages, and cities to identify the relative role of local and landscape effects on plant–pollinator communities along this urbanization gradient. We found that the number of flower visits by solitary bees, but not bumblebees, was highest in cities and lowest in farmland, with villages being intermediate, whereas syrphid flies exhibited lowest numbers in cities. Villages supported the richest pollinator communities, as they appeared to benefit from both farmland and city communities. Plant–pollinator network metrics such as robustness, interaction evenness, and interaction diversity decreased with increasing urbanization, although local plant richness increased toward urban areas. In conclusion, pollinator communities were most diverse and stable in farmland and village sites, despite the high plant richness in cities. The different composition of pollinator communities along the urbanization gradient suggests considering all three landscape types for conservation schemes.
Highlights
The predominant landscape type worldwide is farmland interspersed with urban areas, but urbanization is steadily growing in importance
Plant species richness was positively correlated with the level of urbanization as plant richness was higher in villages and cities compared to farmland (Fig. 3)
Pollinator visitation The pollinator group identity and the amount of urban area influenced the number of visits by pollinating insects with solitary bees and syrphid flies visiting flowers most often, but in different landscape types (Fig. 4, Table 1)
Summary
The predominant landscape type worldwide is farmland interspersed with urban areas, but urbanization is steadily growing in importance. The surprising diversity of flower-visiting taxa (Baldock et al 2015, Sirohi et al 2015) is linked to the generally higher plant richness in urban areas, mostly due to the presence of many non-native plants in urban gardens (Pysek 1998) that can play an important role as pollen and nectar resources (Ahrne et al 2009). Ahrne et al (2009) and Verboven et al (2014) found that bumblebee and syrphid fly richness both show a negative relationship with increasing urbanization. These contrasting results illustrate that urbanization effects on pollinators may be diverse
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