Ornamental plants as a source of pesticide exposure for pollinators

Ornamental plants for sale to the public were the focus of a recent study by scientists from Italy and the UK.  The goal was to determine whether pollinator-attracting flowering plants, from local garden centres in East Sussex, England, were a source of toxic pesticides with potential to contaminate pollinators (e.g. bees, hover flies, butterflies, etc.).

Leaf samples were collected from 29 different species/varieties, and pollen samples were collected from 18 species/varieties.  Pesticides chosen for analyses were those most widely used in the UK, including 5 neonicotinoid insecticides, 2 pyrethroid insecticides, 1 organophosphate insecticide, and 16 fungicides.

Plants from each supplier contained pesticide residues.  Of the 29 different species/varieties analyzed, only 2 (a daffodil and a salvia) did not contain residues of any of the pesticides being tested for on leaves, whereas 23 contained more than one pesticide, 2 of which contained a mixture of 7 (an ageratum) and 10 (a heather) different insecticides and fungicides.  This indicates that the leaves of ornamental plants can often be contaminated with mixtures of insecticides and fungicides.  Neonicotinoids were detected in more than 70% of the plants analyzed; the organophosphate was detected in 10%; pyrethroids in 7%; and fungicides in 38%.

A total of 13 different pesticides were found in pollen samples.  When examining individual plants, there was a highly significant correlation between systemic pesticide concentrations detected in leaves and those detected in pollen.  This suggests that systemic pesticides are easily transported to the pollen.  In addition, some contact pesticides and localized penetrant pesticides were also detected in pollen, likely due to pesticide spraying during flowering.

Many ornamental flowering plants are a rich source of pollen and nectar in urban environments, and pollinators are often attracted to these plants.  Many gardeners purchase plants with the intention of providing wildlife habitat, including providing forage for pollinators.  Pollinators foraging at the flowers analyzed here would likely be exposed to a mixture of chemicals, and numerous studies report pesticides as having additive, or even synergistic, effects when used in combination with other pesticides.

Many ornamental plants are bought and planted in spring, which may expose bumblebees to pesticides at a critical period during early development of bumblebee colonies.  The safest option for anyone wishing to help pollinator populations would be to buy plants from organic nurseries or grow plants from seed.  Hopefully, growers will begin to add pesticide exposure information to plant labels, allowing consumers to make an informed choice.

LINK to Lentola et al.'s 2017 article in Environmental Pollution.

New approach to prioritizing conservation for Europe's bumblebees

Bees are increasingly a focus of conservation action, as large-scale declines are reported, and bumblebees (Bombus spp.) are often of special interest to conservation biologists.  Although bumblebees live in a wide range of latitudes and habitats, they tend to be adapted to cold and temperate regions of the northern hemisphere.  Many species have relatively narrow range sizes (e.g. high elevation mountain ranges where the threats of current and future climate warming are especially severe), and narrow range size can potentially increase a species's vulnerability.

Analyzing molecular phylogeny alongside recent data on distribution and conservation status, of different bumblebee species in Europe, has been recently introduced as a powerful synergistic set of tools for the conservation of Europe's bumblebees.  The International Union for Conservation of Nature's (IUCN) Red List of Threatened Species is a great reference for conservation planning.  However, today's conservation biologists are challeneged with setting priorities within groups of species which are often highly diverse and include many species categorized as "Data Deficient".  In these cases, a species's contribution to phylogenetic diversity can be taken into account for conservation planning.  Of course, contribution to phylogenetic diversity can also be taken into account for species that are not data deficient.

Some threatened bumblebee species in Europe, for example B. mendax, are relatively genetically-unique, and their extinction would represent a relatively greater loss of phylogenetic diversity.  In contrast, the loss of B. fragrans and B. distinguendus, both threatened with extinction, might not result in the loss of the bumblebee subgenus Subterraneobombus, since B. subterraneus is listed by IUCN as "Near Threatened".  Similarly, it is unlikely that phylogenetic diversity within the subgenera Alpinobombus and Thoracobombus will be lost as a whole, as this would require the loss of species like B. balteatus and B. mesomelas, both of which are listed by IUCN as species of "Least Concern".

There is then the question of whether geographically-restricted bumblebee species are more vulnerable to extinction.  In theory, it can be expected that narrow range size potentially increases a species's vulnerability.  A typical example of this is B. mendax, a species listed as only near-threatened, yet having a range size restricted to high altitude habitats of the Cantabrian Mountains (where this species is very rare), the Pyrenees, and the Alps.

An EDGE (evolutionarily distinct, globally endangered) metric was developed in order to better combine phylogenetic uniqueness and IUCN Red List category into one integrated analysis. It was concluded that the species with the highest EDGE scores, and thus those deserving the most conservation attention, are B. fragrans, B. armeniacus, B. zonatus, and B. brodmannicus.  It is important to note that each of these species are listed as endangered in the IUCN Red List, and each are characterized as having an unusually small range size.

An integrated analysis of evolutionary distinctiveness and range size (EDR) was then performed, in order to better target species that are both phylogenetically unique and have restricted range sizes, irrespective of their IUCN category.  B. brodmannicus was shown to have a high EDR score, and this species is listed as endangered in the IUCN Red List due to its small range size and disjunct distribution between the Alps and the Caucasus.  This status should help in prioritizing conservation action for B. brodmannicus.  Mentioned already above, B. mendax, though listed as near-threatened, has a comparatively high EDR score, suggesting that this species should also receive conservation attention, as it is both evolutionarily unique and highly restricted to high alpine and subalpine areas as already mentioned above.

The use of species distribution models for identifying key biodiversity areas and regions with higher phylogenetic endemism is an essential next step.  This should be done using conventional yet successful tools like the IUCN Red List alongside functionally- or phylogenetically-informed approaches to conservation prioritization.  Unique phylogenetic diversity contributions, such as that of B. mendax, should be incorporated into conservation planning by upscaling its IUCN Red List status accordingly.  For this species as well as those already listed by IUCN as endangered, this assessment should be taken into account when identifying key biodiversity areas.

LINK to Nicolas J. Vereecken's 2017 article in Biological Conservation.