Landscape or local? Distinct responses of flower visitor diversity and interaction networks to different land use scales in agricultural tropical highlands

Abstract

Land use change has been identified as a cause for biodiversity loss and has significant effects on pollinators and their interactions with plants. Interaction network analyses complement diversity estimators by providing information on the stability and functionality of the plant-pollinator community in an ecosystem. However, how land use changes affect insect diversity, and the structure of their plant-insect interaction networks, could depend on the intensity of the disturbance but also may be a matter of scale. Our study was carried out in a tropical highland landscape dominated by intense, yet diverse, small-scale agriculture. We studied the effects of land use, at a landscape scale, and local cover and plant ecological descriptors, at a local scale; on diversity descriptors of insect pollinator communities, the abundance of the most frequent flower visitors, and their interaction networks. Seminatural vegetation favored insect flower visitors at both scales. At the landscape scale, human settlements positively influenced bee diversity, and seminatural areas favored the abundance of frequent hoverfly and bumblebee species. At the local scale, bare soil cover negatively influenced honeybee abundance while flower-rich covers positively related to bumblebee abundance. Only local scale variables had influence on network metrics. Bare soil cover was related to higher network specialization, probably due to a low rate of honeybee interactions. Flower-rich covers negatively influenced network connectance but favored modularity. These results suggest that flower resources, provided by weed areas and flowering crops, promote a high rate of interactions between trophic levels and a non-random structure in the interaction networks that may be helping to sustain network stability. Our results highlight the role of seminatural vegetation, at both scales, in maintaining stable insect pollinator communities and interactions in heterogeneous agricultural landscapes of the tropics.

Fruit production in coffee (Coffea arabica L.) crops is enhanced by the behaviour of wild bees (Hymenoptera: Apidae)

“…Several studies on coffee have already observed the positive effect of the proximity of natural areas on the diversity of floral visitors (Bravo‐Monroy et al 2015; Ricketts 2004; Ricketts et al 2008). Other studies in coffee plantations have also shown that wild bees, especially the social ones as stingless bees, were enhanced in the presence of high shade coffee and tree diversity, as in our agroecological sites (González‐Chaves et al 2020; Jha & Dick 2010; Jha & Vandermeer 2009, 2010; Munyuli 2011) and floral resource availability (Escobedo‐Kenefic et al 2020, 2022; Landaverde‐González et al 2017). This proximity and higher proportion of natural areas in our study sites could have contributed to favoured pollination by wild bees.…”

“…At the same time, the presence of other floral heterogeneous resources such as co‐flowering crops can cause competition and stress within coffee crops, more strongly affecting the availability in coffee of social bees such as honeybees and stingless bees (Bänsch et al 2021; Geeraert et al 2019; Ludewig, Götz, et al 2023; Peters et al 2013; Ricketts 2004; Veddeler et al 2006). However, these are hypotheses that are out of the scope of this study and future studies that consider the effect of floral heterogeneity at landscape and local scales (Escobedo‐Kenefic et al 2022) and competition between species in cash crops should be assessed.…”

“…Further, the abundance, richness and density of flower resources have been observed to be a positive driver of pollinator diversity and visitation behaviour (e.g., increase of visitation rate) in both tropical (Caudill et al 2017; Escobedo‐Kenefic et al 2020, 2022; Fisher et al 2017; Hipólito et al 2018; Landaverde‐González et al 2017; Vergara & Badano 2009) and temperate regions (Theodorou et al 2017, 2020). However, some studies, mainly in coffee crops, also suggest that other floral resources and co‐flowering crops may have no effect at the field scale or may compete for pollinators with mass flowering crops as coffee (Bänsch et al 2021; Geeraert et al 2019; Peters et al 2013; Ricketts et al 2008; Veddeler et al 2006).…”

The human touch: a meta-analysis of anthropogenic effects on plant-pollinator interaction networks

“…However, in the long term, an even more intense reduction in diversity can be observed, also impacting generalist species ( Burkle & Knight, 2012 ). Furthermore, the increase and lack of effect on nestedness in the 11 presented studies could be linked to the concentration of interactions by generalist species, both in plants and pollinators ( Jauker et al, 2019 ; Díaz Infante, Lara & Arizmendi, 2020 ; Morrison & Dirzo, 2020 ; Motivans Švara et al, 2021 ; Escobedo-Kenefic et al, 2022 ).…”

“…Regarding the effects of anthropization on the structural patterns of interaction networks, previous research supports our results, concluding that the metrics used are particularly sensitive to environmental changes ( Aguilar et al, 2009 ; Ferreira, Boscolo & Viana, 2013 ; Soares, Ferreira & Lopes, 2017 ). However, contrary to our findings, other studies have indicated that empirical data available suggest that nestedness is not affected by habitat disturbance ( e.g ., Hagen & Kraemer, 2010 ; Jauker et al, 2019 ; Morrison & Dirzo, 2020 ; Escobedo-Kenefic et al, 2022 ). Instead, H 2 ’ metrics show responses similar to those obtained in this study.…”