A method to quantify how much pollen bats deposit on a flower’s stigma

Nicotiana otophora

by Hoyos Díaz et al.

How can we determine if an animal visiting a flower is actually pollinating it? The only direct evidence is the presence of its pollen deposited on the flower's stigma. Traditionally, this is assessed by exposing virgin flowers to a single visit and then collecting the stigma to count the pollen grains using different types of microscopes. More recently, double-sided adhesive tape either placed directly on the stigma or rolled into a cylinder, has been used to capture pollen deposited by bats, hummingbirds, and insects in across various plant species.

This work proposes a modification to that procedure by designing a fingernail-sized adhesive surface that is placed over the flower's stigma and can be replaced in seconds after each visit. To validate the methodology, we used Nicotiana otophora (Solanaceae), a species that is suspected to be visited and pollinated by bats, although this has never been confirmed by direct evidence. We demonstrated that in 80 to 100% of cases, the bats left pollen on the adhesive surface by testing three different adhesive materials and filming the visits of two species of nectarivorous bats, Glossophaga soricina and Anoura caudifer (Phyllostomidae, Glossophaginae), with night-vision cameras, occasionally with records of more than 3000 grains in a single visit. Likewise, we found no differences between the adhesive materials or between the bat species, supporting the consistency of the method examined.

Our results are doubly valuable. Firstly, through direct evidence, we have proved that both bat species are effective pollinators of N. otophora in the southernmost extreme locations in the Neotropics where these nectarivorous bats live. Secondly, we have developed a methodological improvement to a simple, affordable, and reusable tool applicable to flowers with stigmas large and exposed enough to support the pollen-collecting sheet without altering its geometry. This allows for more accurate estimates of pollen deposition by biotic pollinators.
  

Read the scientific article in JPE. 

Testing the efficacy of artificial flowers as a novel attractant for automated pollinator monitoring

by Ash et al.

Pollinating insects like bees, hoverflies, and wasps are declining worldwide, and tracking their numbers usually requires walking surveys or stationary traps such as pan traps or sticky paper, both of which can be labour-intensive, lethal to insects, and difficult to standardise across different locations. Automated insect camera traps use cameras to record insects in the field without killing them. This a promising alternative for long-term monitoring, but very little research has explored what should be put in front of these cameras to attract insects in to be photographed.
To address this gap, we designed realistic 3D-printed artificial flowers, shaped like buttercups and painted in three UV-reactive colours (yellow, white, and blue). We compared these artificial flowers against two established, non-lethal attractants designed to resemble pan traps and sticky paper. We filmed insect visits to the attractants over several weeks in a UK wildflower meadow, recording whether insects approached or landed on each attractant, which colours they preferred, and how long they stayed.
Overall, insects favoured the artificial flowers over the traditional attractants. Hoverflies and bumblebees, both important pollinators, showed a clear preference for the artificial flowers, with hoverflies landing on them far more often than on the other options. Smaller insects also preferred the flowers, although a couple of groups, including wasps and non-hoverfly flies, favoured the traditional attractants instead. Importantly, insects that did land tended to stay for several seconds, long enough for an automated camera to capture a usable image, with yellow flowers performing especially well for keeping hoverflies and solitary bees in place.
These findings suggest that artificial flowers could offer a more effective, standardised, and non-lethal way to attract key pollinators for automated camera monitoring. This could support wider efforts to track pollinator populations consistently across sites, informing conservation policy and helping safeguard the ecosystem services these insects provide.
 

Read the scientific publication in JPE HERE. 

Reproductive ecology of the aromatic plant Agastache mexicana (Lamiaceae): A valuable species to be used in urban pollinator gardens

Papilio multicaudata visiting the 
inflorescence of Agastache mexicana

by Carbajal-Velázquez et al. 

Pollinator gardens promote the conservation of pollinators within the urban landscape by offering various resources and friendlier habitats. Native plants are a key aspect for the success of these gardens as they are species that pollinators have historically interacted with and usually perform better than exotic plants. Although Mexico has a wide plant diversity, few species are available in nurseries to be used in the implementation of gardens. In this study, we focused on Agastache mexicana (Lamiaceae), deeply studied and commercially used plant for its medicinal properties. Specifically, we evaluated its potential to attract flower visitors and some aspects of its reproductive biology in a recently implemented pollinator garden. Over 276 hours of observation, 860 visits were recorded from 66 morpho species, distributed across 12 taxonomic orders. Interestingly, records included pollinators (26%), nectar robbers (57%) and 17% of contact species (i.e., animals using plants for predation, mating, nesting). A GLMM showed positive effects of ambient temperature, and a marked influence of co-flowering species present in the garden. Visits by pollinators and nectar robbers may be related to the presence of long-lasting inflorescences composed of large tubular nectar rewarding flowers in A. mexicana. According to our results A. mexicana contributes to the attraction of high taxonomic and functional diversity, including mutualistic and antagonistic interactions, highlighting its value for implementation in the design of urban gardens focused on pollinator conservation. 

Read the scientific publication in JPE here! 

 

Native plants and pollinators in the city: the case of Abutilon grandifolium in Buenos Aires

Honey bee visiting Abutilon grandifolium

by Cáceres et al.

Urban green spaces can be important places for plants and insects. Parks, reserves and even small public squares can provide important spaces for plants, insects and the ecological interactions that connect them. In Buenos Aires, urban green spaces now include native plants but we still know relatively little about how these plants reproduce and which insects visit their flowers.

In this study, we worked with Abutilon grandifolium, a native shrub with orange-yellow flowers. We studied plants growing in two urban green spaces: an ecological reserve and a public square planted with native species to recreate local habitats. We studied its floral biology, reproductive system and flower visitors to understand how this plant reproduces and how it interacts with pollinators in the city.

We found that A. grandifolium can produce fruits and seeds by self-pollination, meaning that it does not strictly need pollinators to reproduce. Even so, its flowers attracted several insects, especially bees and native halictid bees.

Honey bees were the most frequent visitors, ut they did not always act as good pollinators: in many cases, they collected nectar without touching the reproductive parts of the flower. Native halictid bees, instead, moved inside the flower and touched both the pollen and the stigmas, making them particularly important pollinators. Other insects, such as large bees, hoverflies and beetles, also visited the flowers, although less frequently. By observing their behaviour and analysing where pollen was carried on their bodies, we were able to distinguish visitors that likely contributed to pollination from those that mainly collected floral rewards without effectively transferring pollen.

An interesting result was that the public square supported a community of floral visitors similar to that of the ecological reserve. In fact, visitor richness was even higher in the square. This suggests that small urban green spaces planted with native species can help maintain pollination processes and may act as stepping-stones for biodiversity within the city.

Our results show that bringing native plants back into urban landscapes is more than a matter of beauty or gardening. These plants can help create living networks between flowers and insects, supporting pollinators and ecological interactions even in the middle of a large city.

Read the scientific article in JPE here.