Forest and connectivity loss simplify tropical pollination networks

Abstract

Mutualistic interactions between plants and pollinators play an essential role in the organization and persistence of biodiversity. The structure of interaction networks mediates the resilience of local communities and ecosystem functioning to environmental changes. Hence, network structure conservation may be more critical for maintaining biodiversity and ecological services than the preservation of isolated species in changing landscapes. Here, we intensively surveyed seven 36 km 2 landscapes to empirically investigate the effects of forest loss and landscape configuration on the structure of plantpollinator networks in understory vegetation of Brazilian Atlantic Forest. Our results indicate that forest loss and isolation affect the structure of the plant-pollinator networks, which were smaller in deforested landscapes, and less specialized as patch isolation increased. Lower nestedness and degree of specialization (Hʹ 2 ) indicated that the remaining plant and bee species tend to be generalists, and many of the expected specialized interactions in the network were already lost. Because generalist species generate a cohesive interaction core in these networks, these simplified networks might be resistant to loss of peripheral species, but may be susceptible to the extinction of the most generalist species. We suggest that such a network pattern is an outcome of landscapes with a few remaining isolated patches of natural habitat. Our results add a new perspective to studies of plant-pollinator networks in fragmented landscapes, showing that those interaction networks might also be used to indicate how changes in natural habitat affect biodiversity and biotic interactions.

Abundance and phenology drive plant–pollinator network responses to restoration in the Southern Atlantic rainforest in Brazil

“…In addition, the similar responses of plant-pollinator interactions among both restoration strategies reflect the landscape context since the restoration study sites are embedded in a matrix of natural landscapes (Kauano et al 2013) probably maintaining similarly some processes, such as natural recruitment of seedlings and seeds from late successional species (Cheung et al 2010). It is already known that the landscape context influences the resilience of forest recovery (Kauano et al 2012) and plant-pollinator interactions (Menz et al 2011;Ferreira et al 2020) and, for the restoration study sites, the results indicate that both strategies have the potential to maintain the ecological conditions needed for interaction establishment. Furthermore, the similar responses among areas under different restoration strategies might have also arisen from the strong resilience of plant-pollinator interactions in restoration areas (Lomov et al 2010).…”

Do bipartite binary antagonistic and mutualistic networks have different responses to the taxonomic resolution of nodes?

“…Our findings can help studies with data obtained from large areas and comparative network studies. By using a lower resolution to identify these network nodes, it is possible to compare networks with different species sets in studies that require large sample sizes and the use of network metrics as response variables, such as in landscape ecology studies (Moreira et al ., ; Ferreira et al ., ). Moreover, adjusting the taxonomic resolution to a proper, more functional or easy to observe level can lead to alternative ways of thinking about or collect network data, reducing the effects of missing or forbidden links and cryptic species in the data set.…”

Specialist Bee Species Are Larger and Less Phylogenetically Distinct Than Generalists in Tropical Plant–Bee Interaction Networks

“…However, several studies have indicated that the abundance and diversity of bees are declining and that some species are clearly at risk of extinction (Gallai et al, 2009;Garibaldi et al, 2009;Lever et al, 2014). In particular, specialist species (i.e., those that interact with a smaller number of partners) seem to be the most vulnerable to habitat loss (Bommarco et al, 2010;Aizen et al, 2012;Ferreira et al, 2020). Bees are considered the main taxon of pollinators, so understanding bee pollination networks and bee specialism patterns may provide effective support to conservation and restoration programs (Hallett et al, 2013).…”

“…However, such network-based approaches to determining ecological specialization are strongly influenced by sampling methods, and failure to use standard survey methods can produce inaccurate assessments of plant-bee interactions (Vázquez and Simberloff, 2002;Vázquez and Aizen, 2003;Dorado et al, 2011). For example, in tropical regions, mainly in tropical forests with high canopies, bee sampling is usually restricted to flowers in the lower strata of vegetation (Ferreira et al, 2020).…”