Spatial occupancy patterns of the nursery pollinator Derelomus chamaeropis at its host plant, Chamaerops humilis (Arecaceae)

Weevil Derelomus on the dwarf palm Chamaerops

By Moreno et al.

This study investigated how the weevil Derelomus chamaeropis—a specialist pollinator—and its host, the dioecious (individuals with separated sexes) dwarf palm (Chamaerops humilis), interact in nature. In particular, we evaluated how the spatial arrangement of these palms affects pollination and fruit production. We discovered that weevils prefer female palms and while the small-scale clustering of palms affects where weevils choose to settle, the dense groups of palms help improve fruiting. This study highlights how both the behavior of pollinators and the way plants are arranged can significantly influence pollination outcomes. 

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A survey of summer pollinator assemblies in two contiguous Richmond, Virginia (U.S.A.), urban green spaces

 By Ruppel & Trapp

A carder bee (Anthidium)

About 70% of the global human population is expected to reside in cities by the year 2050, further increasing our urban footprint and reducing wildlife resources. Green infrastructure incorporates natural elements into city spaces often heavily laden by concrete and can provide ecosystem resources for declining insects.  Pollinators, in particular, benefit from greater access to foraging rewards and nest sites. In this study, we surveyed two contiguous urban gardens which sit adjacent to substantial amounts of impervious surfaces, two active railroad tracks, and the Kanawha Canal in Richmond, Virginia (U.S.A). These gardens were planted with a preference toward Virginia-state native plants, and contain 70 unique species made up of flowering trees, shrubs and herbaceous perennials.

Our aim was to identify insects using the urban gardens for floral resources, like pollen and nectar. We surveyed floral visitor interactions on 19 plant species at Great Shiplock Park and the Low Line Gardens from June to August in 2023. Flower visiting insects were visually-identified in the field or via photography/specimen collection. Overall, 110 distinct floral visitors were observed over the ten weeks and categorized as a bee (25% of all observations), wasp (18%), butterfly/moth (16%), fly (15%), beetle, or true bug. We found that insect visitation varied by category across the surveyed plant species, and the two gardens hosted a broad range of both generalists and specialists. For example, the common eastern bumblebee (Bombus impatiens) was identified on all nineteen plant species. Meanwhile, many of the observed taxa were seen on four or fewer of the monitored plant species. Of the 11 bee species observed on four or fewer flowers were two rare bumblebee species, the golden northern bumblebee (Bombus fervidus) and southern plains bumblebee (Bombus fraternus), which were both recently recommended for federal protection.

The results of this survey provide a regional and seasonal perspective on urban green space ecosystem dynamics, and a reference that new green infrastructure projects can utilize. Our observations, especially for bees, were similar to another assessment recently conducted in the region. Furthermore, the outcome of this inventory can be used to assess impacts of urbanization on plant-pollinator interactions with response to pressures like climate change.

 

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Increased reliance on diurnal pollination in a geographically and morphologically atypical sand verbena

Abronia ameliae visited by butterfly

By Jaeger et al.

Traditional pollination syndromes describe sets of floral traits that have converged based on pollinator selection. Closely related species are expected to maintain similar syndromes if pollinators remain stable over evolutionary time. However, deviations from ancestral floral traits may signal previously unrecognized pollinator shifts. Abronia ameliae (heart’s delight) presents a combination of traits typical for moth pollination — strong scented, tubular flowers — but also exhibits features unusual for nocturnal pollination, including pink, diurnally open flowers and large, upright inflorescences.

To investigate its pollination system, we conducted pollinator-exclusion experiments in both a natural population and a common garden, assessing the independent reproductive contributions of diurnal and nocturnal pollinators. Additionally, we characterized the floral volatile profile, which is an important trait in the attraction of many floral visitors. Our results indicate that A. ameliae is primarily diurnally pollinated, with visits from butterflies and day-flying moths leading to significantly higher seed set than nocturnal moth visits. However, nocturnal pollination still contributes meaningfully to reproduction, and the floral volatile emissions predominantly include compounds commonly associated with moth attraction.

These findings suggest that A. ameliae may have transitioned to a mixed pollination strategy, evolving traits that facilitate diurnal as well as nocturnal pollination. This shift challenges rigid pollination syndrome classifications and suggests the evolutionary flexibility of floral traits in response to changing pollination pressures.

Read the scientific publication in JPE