**1. Introduction**

Cities in the world have faced steady growth in the last decades caused by migration from rural areas. As a result, the urban population is around 55%, and the UN estimates that the world urban population might increase by over 68% by the year 2050, which will demand faster urban expansion. The changes resulting from urbanization will affect mainly medium-sized cities (between 500 thousand and one million inhabitants), where half of the world's urban population currently lives [1]. Usually, the urbanization process in tropical and developing countries is not planned and causes drastic changes in the landscape, often irreversible, such as the increase of impervious areas (pavement, asphalt, buildings) and the destruction of wild vegetation. The great challenge for these cities is the sustainable growth that guarantees housing, transport system and energy for the population, combined with environment preservation and conservation of biodiversity [2].

The expansion of urban areas is one of the leading causes of pollinators' decline [3–5]. Among the affected pollinators are the wild bee species (Hymenoptera, Apoidea). Many bee species have a short lifecycle and high sensitivity to temperature, luminosity and humidity, responding to changes caused by urbanization [6]. Bees vary in their nesting location, build nests in the ground, in preexisting cavities in hollows in tree trunks and branches, human constructions such as walls and poles, or even exposed, out of cavities [7]. Bee species also differ in the degree of sociality, ranging from solitary to highly eusocial, and in the degree of specialization or generalization in the choice of resources [8]. Therefore,

**Citation:** Guimarães Alves, S.; Gaglianone, M.C. Bee Guilds' Responses to Urbanization in Neotropics: A Case Study. *Diversity* **2021**, *13*, 365. https://doi.org/ 10.3390/d13080365

Academic Editor: Eric Buffetaut

Received: 20 July 2021 Accepted: 4 August 2021 Published: 7 August 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

the bee community suffers direct influence from the availability of plant resources in the environment. Vegetation offers substrates such as trunks and hollows of trees for nesting, and their flowers provides resources such as nectar, pollen, oils and resin for feeding and provisioning the nests [7,9]. These different bees' biological characteristics determine how these insects interact with the environment and how they tolerate changes [10].

On the other hand, urban green areas (UGAs) such as squares, parks, urban forests and gardens are growing in importance, considering bee-friendly spaces with potential to act as a refuge for bees [11]. Urban green areas are patches of vegetation within cities, where there is a lower application of pesticides when compared to agricultural areas. The vegetation in these urban areas is composed of wild or exotic plants inserted through landscaping projects that can result in a more heterogeneous environment. In addition, these green areas' characteristics can provide nesting sites, foraging and sources of other materials for bees [12]. Therefore, even small green areas have importance and can function as ecological corridors, connecting patches of vegetation to improve bee distribution [13].

However, there is still no consensus on which characteristics of urban green areas are essential to conserving the bee community in cities [11]. One expects that pollinators respond to urbanization with positive and negative effects observed depending on taxon and environment traits. Urban expansion is not homogenous and has a significant variation in different countries and ecosystems [14]. The available data are not representative enough to guide pollinators' conservation actions globally, because most focus on North America and Western Europe with specific taxonomic groups and geographic situations. The results cannot be applied in other regions or taxa [15]. A recent systematic review of 141 peer-reviewed journals, that aimed to understand how urbanization affects pollinators' communities, showed that tropical regions remain little studied [16]. It is a significant gap that needs to be fulfilled, considering that these regions have incredible biodiversity, and many places are hotspots threatened by fast urban growth. South American countries already have an urban population of over 80%, and Brazil is at the top of the list, with more than 200 million people living in cities [1].

Here, we used a medium-sized Brazilian city to investigate which conditions of urban green areas and their surroundings can potentially contribute to shelter and conserve bees' communities. Considering biological and functional traits, we also grouped bees in guilds to provide data that can increase the efficiency of management and conservation of bee and plant species [17]. Therefore, this work aims to answer the following questions: (1) What is the community structure found in urban green areas associated with a medium-sized city in Brazil? (2) How do the different bee guilds respond to the conditions of urban green areas? Answering these questions, we intend to test two hypotheses. First, urban green areas can provide nesting sites and foraging resources to provide refuge for the bees' community. Second, bee species respond to urbanization according to their nesting behavior, nest site and trophic specialization.
