Tag: bumblebees

Natural history collections shed light on bumblebees’ modern struggles

Using pollen metabarcoding, researchers analyzed historical and recent bee specimens, revealing significant shifts in foraging patterns.

A new study highlights potential causes for changing foraging habits of bumblebees. Using advanced molecular techniques called pollen metabarcoding, researchers investigated interactions between bumblebees and plants in Cuxhaven, Germany, and how they changed over 60 years. Their findings can help us understand the connections between availability of floral resources and changing landscapes.

The study, led by the Botany Department of the University of Kassel (Germany) in collaboration with the Leibniz Institute for the Analysis of Biodiversity Change (Germany), used bumblebee specimens from historical museum collections dating back to 1968/69 and compared them with bumblebees collected in the field in 2019. By analyzing pollen samples attached to the bodies of the bees, the researchers were able to identify the plant species they had interacted with.

The results revealed significant shifts in the foraging habits of bumblebees between the late 1960s and more recent sampling periods. In particular, there was a noticeable decrease in interactions with Fabaceae plants in 2019 compared to the past. “This suggests that changes in the landscape have led to alterations in the availability of floral resources, which may contribute to the decline of specialized bee species,” the researchers explain.

“The successful application of scalable molecular techniques to analyze historical pollen samples highlights the value of museum collections as a valuable resource for biodiversity research,” they add. “This study, published in the journal Metabarcoding and Metagenomics, serves as a proof of concept for comparative analysis of recent and historical pollination data, providing important insights into the changes in foraging trends of bumblebees over time.”

“In conclusion, this study contributes to our understanding of bumblebee interactions with foraging resources and the impact of landscape changes on their foraging habits,” say the researchers. Their findings underscore the importance of conserving and restoring suitable habitats for pollinators.

“Future research in this field is expected to provide valuable insights for the conservation and management of pollinators and their critical role in maintaining ecosystems,” they conclude.

Original source:

Kolter A, Husemann M, Podsiadlowski L, Gemeinholzer B (2023) Pollen metabarcoding of museum specimens and recently collected bumblebees (Bombus) indicates foraging shifts. Metabarcoding and Metagenomics 7: e86883. https://doi.org/10.3897/mbmg.7.86883

Images by Andreas Kolter

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Bee diversity and richness decline as anthropogenic activity increases, confirm scientists

The researchers compared wild bee communities in the tropical dry forest of Mexico living in three habitat conditions: preserved vegetation, agricultural sites and urbanised areas

Changes in land use negatively affect bee species richness and diversity, and cause major shifts in species composition, reports a recent study of native wild bees, conducted at the Sierra de Quila Flora and Fauna Protection Area and its influence zone in Mexico.

Having registered a total of 14,054 individual bees representing 160 species, 52 genera, and five families over the span of a year, the scientists conclude that the studied preserved areas demonstrated “significantly greater” richness and diversity.

In their paper, published in the open-access Journal of Hymenoptera Research, a research team from the University of Guadalajara, Mexico, led by Alejandro Muñoz-Urias, compare three conditions within the tropical dry forest study site: preserved vegetation, an agricultural area with crops and livestock, and an urbanised area.

This bee species (Aztecanthidium xochipillium) is known exclusively from Mexico.

The researchers confirm earlier information that an increase in anthropogenic disturbances leads to a decrease in bee richness and diversity. While availability of food and nesting sites are the key factors for bee communities, changes in land use negatively impact flower richness and floral diversity. Thereby, turning habitats into urbanised or agricultural sites significantly diminishes the populations of the bees which rely on specific plants for nectar and pollen. These are the species whose populations are threatened with severe declines up to the point of local extinction.

According to their data, about half of the bees recorded were Western honey bees (49.9%), whereas polyester bees turned out to be the least abundant (1.2 %).

On the other hand, some generalist bees, which feed on a wide range of plants, seem to thrive in urbanised areas, as they take advantage of people watering wild and ornamental plants at times where draughts might be eradicating native vegetation.

“That is the reason why bees that can use a wide variety of resources are often able to compensate when circumstances change, although some species disappear due to land use changes,” explain the scientists.

This is a tropical dry forest in the dry (left) and rainy season (right).

In conclusion, the authors recommend that the tropical dry forests of both the study area and Mexico in general need to be protected in order for these essential pollinators to be conserved.

“Pollinators are a key component for global biodiversity, because they assist in the sexual reproduction of many plant species and play a crucial role in maintaining terrestrial ecosystems and food security for human beings,” they remind.

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Original source:

Razo-León AE, Vásquez-Bolaños M, Muñoz-Urias A, Huerta-Martínez FM (2018) Changes in bee community structure (Hymenoptera, Apoidea) under three different land-use conditions. Journal of Hymenoptera Research 66: 23-38. https://doi.org/10.3897/jhr.66.27367

Claims that declines of pollinator species richness are slowing down in Europe revisited

Having conducted a thorough interpretation of the results of a recent study that inferred decrease in the biodiversity loss among pollinators across Europe, Dr Tom J. M. Van Dooren reveals that this conclusion cannot in fact be drawn. It is only supported for the bee fauna in the Netherlands. His study is published in the open access journal Nature Conservation.

Changes in pollinator abundances and diversity are of major concern. Pollinator diversity is quantified by their species richness: the number of species from a specific taxonomic group of pollinating animals present at a given time in a given area. A recent study, adopted in the recent UN IPBES Pollination Report draft summary, inferred that pollinator species richnesses are decreasing more slowly in recent decades in several taxonomic groups and European countries.

However, Dr Tom J. M. Van Dooren, affiliated with both Naturalis Biodiversity Center, the Netherlands, and the Institute of Ecology and Environmental Sciences of Paris, France, has now published his own study to show in detail the inaccuracies that the earlier conclusion has been based on.

Among other points, the scientist notes that the earlier study contained no explicit statistical comparisons between species richness changes in different periods. The earlier study also treated richness changes at country level and small spatial resolution as equivalent, while they probably represent different processes.

“Plants in Great Britain at the smallest spatial scales suggest a reduced rate of changes, but the results for larger spatial scales are not significant,” he illustrates. “The same holds for butterflies in the Netherlands.”

Dr Tom J. M. Van Dooren only finds support in the results of the earlier publication for a decelerating decline in bumblebees and other wild bees in the Netherlands. “This is in fact one taxon, the bees Anthophila, in a single country, the Netherlands”, he notes.

“The lack of robustness points again to the possibility that results found in the data can be due to changes in the shapes of species accumulation curves,” Dr Tom J. M. Van Dooren summarises. “Therefore the status of the statement on decelerating declines in the Pollination Report should be adjusted accordingly.”

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Original source:

Van Dooren TJM (2016) Pollinator species richness: Are the declines slowing down? Nature Conservation 15: 11-22. doi: 10.3897/natureconservation.15.9616

 

Photo credit: 

Aiwok, Wikimedia Commons, CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)