Native and Non-Native Supergeneralist Bee Species Have Different Effects on Plant-Bee Networks

Abstract

Supergeneralists, defined as species that interact with multiple groups of species in ecological networks, can act as important connectors of otherwise disconnected species subsets. In Brazil, there are two supergeneralist bees: the honeybee Apis mellifera, a non-native species, and Trigona spinipes, a native stingless bee. We compared the role of both species and the effect of geographic and local factors on networks by addressing three questions: 1) Do both species have similar abundance and interaction patterns (degree and strength) in plant-bee networks? 2) Are both species equally influential to the network structure (nestedness, connectance, and plant and bee niche overlap)? 3) How are these species affected by geographic (altitude, temperature, precipitation) and local (natural vs. disturbed habitat) factors? We analyzed 21 plant-bee weighted interaction networks, encompassing most of the main biomes in Brazil. We found no significant difference between both species in abundance, in the number of plant species with which each bee species interacts (degree), and in the sum of their dependencies (strength). Structural equation models revealed the effect of A. mellifera and T. spinipes, respectively, on the interaction network pattern (nestedness) and in the similarity in bee’s interactive partners (bee niche overlap). It is most likely that the recent invasion of A. mellifera resulted in its rapid settlement inside the core of species that retain the largest number of interactions, resulting in a strong influence on nestedness. However, the long-term interaction between native T. spinipes and other bees most likely has a more direct effect on their interactive behavior. Moreover, temperature negatively affected A. mellifera bees, whereas disturbed habitats positively affected T. spinipes. Conversely, precipitation showed no effect. Being positively (T. spinipes) or indifferently (A. mellifera) affected by disturbed habitats makes these species prone to pollinate plant species in these areas, which are potentially poor in pollinators.

Massively Introduced Managed Species and Their Consequences for Plant–Pollinator Interactions

“…3E) than most pollinators in the network. These results thus support the idea that A. mellifera tends to be a highly generalist pollinator species that contributes to network nestedness and acts both as a connector within its own module as well as between modules (Giannini et al, 2015;Santos et al, 2012).…”

“…However, network connectance was not affected by A. mellifera removal and authors did not find any correlation between network structure and the proportion of interactions made by A. mellifera in the networks. Giannini et al (2015) studied 21 plant-bee weighted interaction networks from different ecosystem types, also in Brazil. They found that A. mellifera generalism and mean interaction strength was correlated to nestedness and plant niche overlap in their networks.…”

When invasion may not be harmful: niche relations in a lizard assemblage

“…We expect that generalist species may be able to shift part of their behavior or resource use when faced with a newly arrived species, in this case, a NIS. Eventually, the community will adjust to the presence of this NIS as has been observed for Apis mellifera in Brazilian bee communities (Giannini et al 2015).…”

“…Eventually, the community will adjust to the presence of this NIS as has been observed for Apis mellifera in Brazilian bee communities (Giannini et al . ).…”

Ecological Responses to Climate Change at Biogeographical Boundaries

“…Giannini et al [42] observed invasive super-generalist bee species in Brazil replacing native super-generalist species which can modify the interactions in networks. The non-native, super-generalist bee species invaded into the core of the networks rapidly.…”