ArticlePDF Available

Abstract and Figures

Despite widespread concern about declines in pollination services, little is known about the patterns of change in most pollinator assemblages. By studying bee and hoverfly assemblages in Britain and the Netherlands, we found evidence of declines (pre-versus post-1980) in local bee diversity in both countries; however, divergent trends were observed in hoverflies. Depending on the assemblage and location, pollinator declines were most frequent in habitat and flower specialists, in univoltine species, and/or in nonmigrants. In conjunction with this evidence, outcrossing plant species that are reliant on the declining pollinators have themselves declined relative to other plant species. Taken together, these findings strongly suggest a causal connection between local extinctions of functionally linked plant and pollinator species.
Content may be subject to copyright.
domain substituted by the hydrophobic tail of
H-Ras was not (Fig. 4D). Ra c1 is of parti c ul ar
importance to Fc receptor-mediated phagocytosis
and accumulates at the base of forming phago-
somes, detaching rapidly upon sealing (Fig. 4, E
and F, and fig. S7A) (10). Rac1(Q61L) also de-
tached from sealing phagosomes with kinetics
indistinguishable from those of wild-type Rac1
(Fig. 4, G and H, and movie S7). Because
Rac1(Q61L) is constitutively bound to guanosine
triphosphate (GTP), its dissociation from phago-
somes was not due to nucleotide hydrolysis or
cessation of nucleotide exchange. Instead, release
waslikelymediatedbytermination of its electro-
static association with the plasmalemma. Accord-
ingly, the C-terminal tail of Rac1 containing the
polybasic domain behaved similarly (fig. S7B).
Our data indicate that the surface potential of
the inner leaflet of the membrane decreases locally
during phagosome formation. The change is at-
tributable primarily to depletion of PIP
and PS,
but depletion of phosphatidylinositol 4-phosphate
was also observed (fig. S3 and movie S5). Activa-
tion of inositide lipases, kinases, and phosphatases
occurs during phagocytosis and bacterial invasion
(3), readily accounting for the changes in PIP
could be converted to PE by decarboxylation or
could be externalized during phagocytosis by
scramblases and/or efflux pumps.
Our results also indicate that the anchor-
age of important signaling molecules, includ-
ing K-Ras and Rac1, can be modulated focally
by localized changes in surface potential. Other
proteins anchored electrostatically to the mem-
brane, such as MARCKS, are equally suscepti-
ble to the charge alterations that accompany
lipid remodeling. Indeed, we also obtained
evidence for localized detachment of the
tyrosine kinase c-Src (fig. S5, B and C).
The consequences of altered surface charge in
other important biological phenomena must be
considered. Activation of phosphoinositide metab-
olism, elevation in cytosolic calcium, and PS
flipping occur after stimulation of multiple
receptors and channels as well as during apoptosis.
The effect of such responses on inner surface
potential may be measurable with the use of
approaches like the one described here. Cycles of
membrane dissociation/reassociation may add a
layer of functional control to complement the
traditional biochemical mode of regulation of sig-
naling proteins.
References and Notes
1. M. Olivotto, A. Arcangeli, M. Carla, E. Wanke, Bioessays
18, 495 (1996).
2. S. McLaughlin, A. Aderem, Trends Biochem. Sci. 20, 272
3. R. J. Botelho, C. C. Scott, S. Grinstein, Curr. Top.
Microbiol. Immunol. 282, 1 (2004).
4. R. Leventis, J. R. Silvius, Biochemistry 37, 7640 (1998).
5. See supporting material on Science Online.
6. M. O. Roy, R. Leventis, J. R. Silvius, Biochemistry 39,
8298 (2000).
7. J. B. McCabe, L. G. Berthiaume, Mol. Biol. Cell 12, 3601
8. J. F. Hancock, H. Paterson, C. J. Marshall, Cell 63, 133
9. D. Michaelson et al., J. Cell Biol. 152, 111 (2001).
10. A. D. Hoppe, J. A. Swanson, Mol. Biol. Cell 15, 3509
11. We thank E. Pick for providing Rac1 and D. Russell for
providing Nucleosil beads. Supported by the Canadian
Institutes for Health Research and an NIH grant, by a
Canadian Institutes of Health Research studentship (T.Y.),
and by the Pitblado Chair in Cell Biology (S.G.).
Supporting Online Material
Materials and Methods
Figs. S1 to S7
Movies S1 to S7
4 May 2006; accepted 5 June 2006
Parallel Declines in Pollinators and
Insect-Pollinated Plants in
Britain and the Netherlands
J. C. Biesmeijer,
S. P. M. Roberts,
M. Reemer,
R. Ohlemu¨ ller,
M. Edwards,
T. Peeters,
A. P. Schaffers,
S. G. Potts,
R. Kleukers,
C. D. Thomas,
J. Settele,
W. E. Kunin
Despite widespread concern about declines in pollination services, little is known about the
patterns of change in most pollinator assemblages. By studying bee and hoverfly assemblages in
Britain and the Netherlands, we found evidence of declines (pre- versus post-1980) in local bee
diversity in both countries; however, divergent trends were observed in hoverflies. Depending on
the assemblage and location, pollinator declines were most frequent in habitat and flower
specialists, in univoltine species, and/or in nonmigrants. In conjunction with this evidence,
outcrossing plant species that are reliant on the declining pollinators have themselves declined
relative to other plant species. Taken together, these findings strongly suggest a causal connection
between local extinctions of functionally linked plant and pollinator species.
nthropogenic changes in habitats and
climates have resulted in substantial re-
ductions in biodiversity among many
vertebrate taxa (1), and evidence has been ac-
cumulating that insect biodiversity is at risk as
well (2). Of particular concern is the possibility
of community-level cascades of decline and
extinction (3), whereby decline of some ele-
ments of the biota lead to the subsequent loss of
other species that directly or indirectly rely upon
them. Here we examine sets of pollinators and
the plants that they pollinate to test (i) whether
species that are linked to one another within
communities show coincident declines and (ii)
whether species with more links within com-
munities are more robust to change because of
the availability of alternative links, if an inter-
acting species is lost.
Any loss in biodiversity is a matter of public
concern, but losses of pollinating insects may
be particularly troubling because of the poten-
tial effects on plant reproduction. Many agricul-
tural crops and natural plant populations are
dependent on pollination and often on the ser-
vices provided by wild, unmanaged, pollinator
communities. Substantial concerns have been
raised about the decline or loss of these services
E(4) but see (5)^, culminating in formal rec-
ognition within the Convention on Biological
Diversity (6)intheS,o Paulo Declaration (7)
and the International Initiative for the Conser-
vation and Sustainable Use of Pollinators (8).
However, the evidence for such declines re-
mains scanty (5).
To adequately demonstrate a decline in pol-
linator services, one would need to document
(i) overall declines in pollinator density; and/or
(ii) reductions in species diversity or substantial
shifts in the species composition of pollinator
communities, combined with changes in the
distribution of traits represented in those com-
munities (thus indicating that the loss of some
pollinators has not been compensated by the
rise of functionally equivalent species); and (iii)
declines in either the reproductive success or
abundance of plant species dependent on these
pollinators. No suitable data are available to
address overall pollinator density, but here we
provide evidence for the remaining points,
using data for bees, hoverflies, and plants from
Britain and the Netherlands.
We compiled almost 1 million records for
bee (all native species except the largely
Institute of Integrative and Comparative Biology and Earth
and Biosphere Institute, University of Leeds, Leeds, LS2 9JT,
Centre for Agri-Environmental Research, University of
Reading, Reading, RG6 6AR, UK.
European Invertebrate
Survey–Netherlands/National Museum of Natural History
Naturalis, Postbus 9517, 2300 RA Leiden, Netherlands.
Department of Biology, University of York, York, YO10 5YW,
Lea-side, Carron Lane, Midhurst, GU29 9LB, West
Sussex, UK.
Department of Animal Ecology, Bargerveen
Foundation, Radboud University of Nijmegen, Postbox 9010,
6500 GL Nijmegen, Netherlands.
Nature Conservation and
Plant Ecology Group, Wageningen University and Research
Centre, Bornesteeg 69, 6708 PD Wageningen, Netherlands.
Umweltforschungszentrum–Centre for Environmental Re-
search Leipzig-Halle, Community Ecology (Biozo
schung), Theodor-Lieser-Strasse 4, 06120 Halle, Germany.
*To whom correspondence should be addressed. E-mail: SCIENCE VOL 313 21 JULY 2006
domesticated honeybee Apis mellifera)and
hoverfly observations for both countries from
national entomological databases (9), focusing
on areas with extensive sets of observations
before and after 1980. We then applied
rarefaction methods to compare species rich-
ness of focal areas over each period (10). This
approach allows valid comparisons between
time periods, despite unequal sample sizes and
the incorporation of records collected by many
recorders who used different collecting tech-
niques over long time spans (10).
Bee diversity declined in large fractions
of the 10 km by 10 km cells analyzed in both
countries (Fig. 1). Bee richness was measured
as the number of distinct species; significant de-
creases in richness were observed in 52% and
È67% of British and Dutch cells, respectively, as
compared with richness increases in 10% and 4%
of cells in the two countries (table S1). Shifts in
hoverfly diversity were less consistent (Fig. 1),
with no significant directional change in richness
for the UK (increases in 25% and decreases in
33% of British cells); however, increases in
hoverfly richness were reported in 34%, versus
decreases in 17%, of Dutch cells (table S1).
These shifts in species richness reflect
shifts in the distributions of many species in
both groups. Our data set does not allow di-
rect measurement of population densities of
the species involved; nonetheless, shifts over
time in the relative number of records for dif-
ferent species can be used as an indicator of
their relative frequency and ubiquity (10).
There has been an increase in the domination of
the pollinator communities of both countries by
a smaller number of species. For both taxa in
both countries, about 30% fewer species ac-
count for half of the post-1980 records (percent-
ages of fewer species: British bees, 29%;
British hoverflies, 29%; Netherlands bees,
32%; Netherlands hoverflies, 36%). In Britain,
the species that increased were dispropor-
tionately the ones that were already common
before 1980; however, in the Netherlands, this
The functional diversity of pollination net-
works contributes to the maintenance of diver-
sity in plant communities (12), with different
groups of pollinators being complementary in
their pollination services and different groups
of plants being complementary in their roles as
food plants for pollinators. Consequently, a de-
cline in pollinator diversity might have little
effect on a community if the fluctuating species
were functionally similar. However, the traits
of increasing and declining species of solitary
bees and hoverflies differ in consistent ways
(Table 1). In both countries and in both groups,
species with narrow habitat requirements have
experienced greater relative declines. In solitary
bees, oligolectic species (those using few flower
taxa as food sources) have declined significant-
ly in Britain, and long-tongued taxa have
declined significantly in the Netherlands. Die-
tary specialization is important in hoverflies as
well, with both adult and larval diets being
strongly related to changes in hoverfly occur-
rence. Migratory hoverflies have fared better
than nonmigratory species in both countries. In
Britain, bee and hoverfly declines are greater
among species with only a single generation per
year; however, this pattern is not found in the
Netherlands. The significant trends indicate that
specialized species Ei.e., in habitat and dietary
requirements and, arguably, tongue length
(12, 13)^ and species characterized by slower
development and lower mobility (those having
fewer generations per year and being non-
migratory) tend to decline more than general-
ist, fast developing, and more mobile species.
Such shifts in pollinator traits suggest pos-
sible shifts in pollination services. Indeed,
recent experiments have shown that the func-
tional diversity of pollinators can affect diver-
sity in plant communities (12). We know of no
data that will allow us to assess directly
whether rates of pollinator visitation or pollen
depositiontoflowershave shifted appreciably
in Britain or the Netherlands. We can, however,
examine shifts in plant species distributions
using floral inventories from both countries
(10, 14, 15) to see whether shifts in plants are
consistent with the observed shifts in pollina-
tors. In Britain, obligately outcrossing plants
reliant on insect pollinators were declining on
average; species reliant on abiotic (wind or
water mediated) pollination were increasing;
and self-pollinating plant species showed an in-
termediate response (Table 2). In the Nether-
lands, changes were not significantly different
among these three groups; however, given the
observed decline in bees and increase in hov-
erflies in the Netherlands, divergent trends
between bee-pollinated plants and other insect-
pollinated plants may be expected there. After
reexamining the data on the insect taxa reported
as pollinators of outcrossing plants (15), we
found that, on average in the Netherlands, plants
that were exclusively pollinated by bees were
declining, but plants pollinated by flies and other
insects (including bees) were increasing. If the
changes among bee-pollinated outcrossers, out-
Fig. 1. Bee and hoverfly richness has changed in many of the 10 km by 10 km cells analyzed for
Britain and the Netherlands. Some British cells contained adequate data only on eusocial or only
on solitary bees (10). Changes in species richness were calculated from rarefaction analyses (10).
21 JULY 2006 VOL 313 SCIENCE
crossers with abiotic pollination, and predomi-
nantly self-pollinating plants are compared, the
trends observed in the Netherlands mirror those
for Britain: Bee-dependent plants have declined,
abiotically pollinated plants have increased, and
plants mainly relying on self-pollination have
shown an intermediate response (Table 2).
We cannot tell from these data whether the
decline of the plants precedes the loss of the
associated pollinators, whether the decline of
the pollinators leads to the loss of reproductive
function and then to the decline of the plants, or
indeed whether the plants and their pollinators
are both responding to some other factor. How-
ever, the results clearly show that linked ele-
ments in biological communities (i.e., specialist
pollinators and the obligately outcrossed plants
that they pollinate) are declining in tandem.
Furthermore, the difference between the two
countries implies that there is probably a causal
link, because it is the corresponding groups of
plants and pollinators in both countries that are
changing. The hypothesis that species that rely
on a broader range of other species within a
community are more robust in the face of change
is supported by the following evidence: Polli-
nators that rely on few plants for their resources
have declined the most, whereas generalists
have prospered Ecompare with (16)^. Moreover,
the decline of bees (specialized as pollinators)
relative to hoverflies (having broader feeding
habits) could be interpreted in this light.
Demonstrating that there are shifts in pol-
linator assemblages and associated changes in
wild plant communities in two countries does
not prove the existence of a global pollination
crisis. Britain and the Netherlands are not only
two of the countries with the best available data
but also two of the most densely populated and
anthropogenically modified landscapes on the
planet. Few British habitats can be thought of
as truly natural, and in the Netherlands the
landscape is largely artificial. Nonetheless, it
seems probable that shifts similar to those
documented for these countries will be found
in other parts of northwest Europe and, in-
creasingly, in other regions (17). Documenting
the geographical extent of the declines shown
here is a priority for future research. It is also
important to begin mechanistic studies of the
causes of these declines, with habitat alteration
(18), climate change (19–21), and agricultural
chemical usage (18, 22) being potential key drivers
of observed shifts (23).
1. S. L. Pimm, G. J. Russell, J. L. Gittleman, T. M. Brooks,
Science 269, 347 (1995).
2. J. A. Thomas et al., Science 303, 1879 (2004).
3. F. S. Chapin III et al., Science 277, 500 (1997).
4. S. Diaz et al., in Ecosystems and Human Well-Being: Current
State and Trends, Volume 1, R. Hassan, R. Scholes, N. Ash.,
Eds. (Island Press, Washington, DC, 2005), pp. 297–329.
5. J. Ghazoul, Trends Ecol. Evol. 20, 367 (2005).
6. Convention on Biological Diversity (
7. International Pollinators Initiative, the Sa
o Paulo Decla-
ration on Pollinators (Brazilian Ministry of the Environ-
ment, 1999); (
8. Agricultural Biodiversity–International Initiative for the
Conservation and Sustainable Use of Pollinators
9. Dutch data on bees are held in the Apidae database of
the European Invertebrate Survey–Netherlands (EIS-NL).
Dutch data on hoverflies are held in the Syrphidae
database of EIS-NL, the Dutch Youth Organisation for
Nature Study, and the Dutch Entomological Society.
British bee data were compiled by S.P.M.R., M.E., and
J.C.B. from data of the UK Bees, Wasps, and Ants
Recording Society. British hoverfly data were obtained
from the National Biodiversity Network
(, largely based on the Hoverfly
Recording Scheme.
10. Materials and methods are available as supporting
material on Science Online.
11. Results of a Mann-Whitney test comparing pre-1980 cell
totals for significantly declining versus significantly
increasing species: British bees, P 0 0.005; British
Table 1. Trait-based patterns in pollinator declines. Proportions are based on species that showed
significant change in the number of cells (n) in which they were reported during the two time
periods (pre- and post-1980). Declining solitary bee and hoverfly species tend to be found more
among the specialists (characterized by narrow habitat ranges, limited dietary choice, slower
development, and greater residency) than among generalist species (characterized by wide habitat
ranges, broader dietary choice, multiple generations per year, and greater tendency toward
migration). Traits were assigned by using methodologies in (25)and(26). Bumblebees and
honeybees were excluded from the analysis (10). Oligo, oligolectic; Poly , polylectic; Uni, univoltine;
Multi, multivoltine; Macro, macroorganisms; Micr o, microorganisms; Res, resident; Mig, migran t.
Britain Netherlands
Solitary bees
Trait Trait category Pn Trait category Pn
(proportion declining) (proportion declining)
Habitat range Narrow Wide Narrow Wide
(0.90) (0.25) 0.0001 32 (0.83) (0.53) 0.090 29
Flower specificity Oligo Poly Oligo Poly
(0.86) (0.41) 0.034 34 (0.55) (0.76) 0.198 36
Tongue length Long Short Long Short
(0.70) (0.41) 0.099 56 (1.00) (0.51) 0.028 49
Generations Uni Multi Uni Multi
(0.60) (0.14) 0.042 44 (0.76) (0.55) 0.433 42
Trait Trait category Pn Trait category Pn
(proportion declining) (proportion declining)
Habitat range Narrow Wide Narrow Wide
(0.96) (0.28) 0.0001 53 (0.52) (0.25) 0.025 67
Adult food Narrow Wide Narrow Wide
(0.63) (0.41) 0.095 60 (0.53) (0.16) 0.0001 86
Larval food Macro Micro Macro Micro
(0.74) (0.43) 0.009 59 (0.59) (0.20) 0.002 79
Generations Uni Multi Uni Multi
(0.80) (0.29) 0.0001 50 (0.43) (0.38) 0.63 88
Migration Res Mig Res Mig
(0.63) (0.20) 0.01 64 (0.46) (0.17) 0.025 88
Table 2. Mean relative change (TSE) in distribution of British (27) and Netherlands (28)plant
species according to their main pollen vector (10). Insect-pollinated outcrossing plants in Britain and
bee-pollinated outcrossing plants in the Netherlands have declined, whereas plants with abiotic
pollination have increased. Plant breeding systems were derived by combining the ECOFL OR (29)and
BIOLFL OR (30) databases (10). British data were tested with an analysis of variance and a post hoc
Tukey test. Netherlands data were tested with a Kruskal-Wallis test and a post hoc multiple comparison
test. Superscripts indicate group differences based on post hoc tests. n, number of plant species; NL,
Obligatory outcrossing,
insect pollinated
Obligatory outcrossing,
wind or water pollinated
self pollinating
Britain –0.22 T 0.06* þ0.18 T 0.14
–0.003 T 0.70*
(n 0 75) (n 0 30) (n 0 116)
Netherlands þ0.10 T 0.08 þ0.18 T 0.08 –0.08 T 0.11 0.091
(n 0 182) (n 0 160) (n 0 143)
NL bee plants –0.12 T 0.13* þ0.18 T 0.08
–0.08 T 0.11*
(n 0 42) (n 0 160) (n 0 143) SCIENCE VOL 313 21 JULY 2006
hoverflies, P G 0.0001; Netherlands bees, P 0 0.07 (the
reverse trend); Netherlands hoverflies, P 0 0.10.
12. C. Fontaine, I. Dajoz, J. Meriguet, M. Loreau, PLoS Biol. 4,
e1 (2006).
13. M. Stang, P. G. L. Klinkhamer, E. Van der Meijden, Oikos
112, 111 (2006).
14. C. D. Preston, D. A. Pearman, T. D. Dines, New Atlas of
the British and Irish Flora: An Atlas of the Vascular Plants
of Britain, Ireland, the Isle of Man, and the Channel
Islands (Oxford Univ. Press, Oxford, 2002).
15. Biobase 2003, Centraal Bureau voor de Statistiek,
Voorburg/Heerlen, The Netherlands (2003).
16. J. Memmott, N. M. Waser, M. V. Price, Proc. R. Soc.
London Ser. B 271, 2605 (2004).
17. J. Banaszak, Ed. Changes in Fauna of Wild Bees in
Europe (Pedagogical University, Bydgoszcz, Poland,
18. J. A. Foley et al., Science 309, 570 (2005).
19. C. D. Thomas et al., Nature 427, 145 (2004).
20. M. S. Warren et al., Nature 414, 65 (2001).
21. C. Parmesan, G. Hoyle, Nature 421, 37 (2003).
22. P. G. Kevan, Biol. Conserv. 7 , 301 (1975).
23. A Europe-wide assessment of the risks associated with
pollinator loss and its drivers is currently being under-
taken within the 6th European Union Framework
Programme–Assessing Large-scale Environmental Risks
for Biodiversity with Tested Methods project [GOCE-CT-
2003-506675 (], of which this
study is a core element (24).
24. J. Settele et al., GAIA 14, 69 (2005).
25. S.P.M.R. compiled trait data of European bees from
published sources (see
26. M. Speight, E. Castella, J.-P. Sarthou, C. Monteil, Eds.,
Syrph the Net on CD, Issue 2. The Database of European
Syrphidae (Syrph the Net Publications, Dublin, 2004).
27. Change indices from (14) were calculated from occu-
pancy data in surveys conducted from 1930 to 1969 and
from 1987 to 1999.
28. Comparison of the number of 5 km by 5 km cells
occupied in 1940 and 1990. Data from Biobase (15)
were organized into frequency classes by A.P.S. (10).
29. The Ecological Flora of the British Isles at the University
of York (
30. S. Klotz, I. Ku
hn, W. Durka, Eds. BIOLFLOR: A Database
on Biological and Ecological Traits of the German Flora
(Bundesamt fu
r Naturschutz, Bonn, 2002).
Supporting Online Material
Materials and Methods
Figs. S1 and S2
Tables S1 and S2
24 March 2006; accepted 6 June 2006
Crystal Structure of a Divalent
Metal Ion Transporter CorA at
2.9 Angstrom Resolution
Said Eshaghi,
Damian Niegowski,
Andreas Kohl,
Daniel Martinez Molina,
Scott A. Lesley,
r Nordlund
CorA family members are ubiquitously distributed transporters of divalent metal cations and are
considered to be the primary Mg
transporter of Bacteria and Archaea. We have determined a
2.9 angstrom resolution structure of CorA from Thermotoga maritima that reveals a pentameric cone–
shaped protein. Two potential regulatory metal binding sites are found in the N-terminal domain that
bind both Mg
and Co
. The structure of CorA supports an efflux system involving dehydration and
rehydration of divalent metal ions potentially mediated by a ring of conserved aspartate residues at
the cytoplasmic entrance and a carbonyl funnel at the periplasmic side of the pore.
ivalent metal cations are essential co-
factors in many proteins. To provide
cells with appropriate concentrations
of divalent metal cations, highly regulated
transporters and channels have evolved to
translocate these ions across the hydrophobic
membranes. CorA is one of the best studied
families of divalent cation transporters (1–9).
It is considered to be the primary Mg
porter of both Bacteria and Archaea and is
ubiquitously distributed (8). Sequence homolo-
gies between members of this family are most
pronounced at the C termini; sequence conser-
vation in the N termini is less significant (fig.
S1). The overall sequence similarity between
eukaryotes and prokaryotes is weak, except for
the highly conserved Gly-Met-Asn (GMN)
motif close to the C termini (10, 11). Never-
theless, some eukaryotic CorA family members
show overlapping activities with the prokary-
otic members that suggests functional, as well
as structural, conservation (4, 10, 12, 13).
Studies of CorA from Salmonella typhimurium,
Escherichia coli, and the Archaeon Methano-
coccus jannaschii demonstrate that ions can be
transported in both directions (1–3, 5, 8, 9).
Kehres and Maguire recently reported two
classes of CorAs among Bacteria and Archaea
(8). The second class, CorA-II, which differs
from the extensively studied S. typhimurium
and E. coli CorAs, was suggested to contain
two transmembrane helices, with both termini
in the cytosol. In the same report, the CorA-II
proteins were suggested to be efflux systems.
Moreover, a novel CorA-related protein, ZntB,
was recently identified in S. typhimurium (14).
ZntB was shown to be a Zn
efflux system
with two predicted transmembrane helices and
both termini facing the cytosol (15). This is in
contrast with the predicted topology of S.
typhimurium and E. coli CorA, with three trans-
membrane helices and the N terminus facing
the periplasm.
Here, we report the crystal structure of a
full-length CorA homolog from Thermotoga
maritima,at2.9) resolution. The recently
reported structure of a pentameric full-length
CorA at 3.9 ) was used for molecular
replacement, revealing two pentamers in
the asymmetric unit (16). The structure has
been refined to an R of 27.6% and an R
29.5% with good stereochemistry (table S1).
The CorA structure reveals a pentamer with
the shape of a cone (Fig. 1). The tip of the cone
is formed by two transmembrane (TM) helical
segments from each monomer and the large
opening of the cone by the N-terminal region
of CorA. The fold of the CorA monomer is
composed of an N-terminal a/b domainwitha
central seven-stranded mixed b sheet lined by
three small helices. Two long a helices cover
one face of the a/b domain and form a bundle
together with a giant a helix 7 constituted by
È70 residues. The C-terminal end of helix 7
constitutes the first transmembrane segments
(residues 291 to 312). Following the large helix
7 is helix 8 (residues 327 to 349), which forms
the second TM helix and packs in a ring around
the TM segment of helix 7 (Fig. 1).
Thermotoga maritima CorA is most closely
related to the class II CorA with both N- and
C-terminal ends facing the cytosol and, there-
fore, is likely to be primarily involved in ion
efflux. The localization of the N termini in the
cytoplasm is also supported by the positive-
inside rule (17)andtheN
topology of
Bhelical hairpin[ structures (18). Sequence
alignment of close homologs of T. maritima
CorA and those of S. typhimurium CorA sup-
port the proposal for two distinct classes of
CorA (fig. S1).
Our structure agrees in all general features
with the structure determined by Lunin et al.
(16) that was used for phasing. However, be-
cause of the higher resolution of 2.9 ), our
structure provides more details of functionally
important regions, including potential regulato-
ry metal binding sites beyond the metal in site 1
(M1) identified in the 3.9 ) structure. Two
putative metal-binding sites are found at each
interface between the N-terminal domains in
the pentamer (Fig. 2). An anomalous difference
map of Co
-soaked crystals shows that Co
Division of Biophysics, Department of Medical Bio-
chemistry and Biophysics, Karolinska Institute, SE-171 77
Stockholm, Sweden.
Department of Biochemistry and
Biophysics, Stockholm University, S-106 91 Stockholm,
Joint Center for Structural Genomics and
Genomics Institute of the Novartis Research Foundation,
San Diego, CA 92121, USA.
*These authors contributed equally to this work.
†To whom correspondence should be addressed. E-mail: (P.N.); (S.E.)
21 JULY 2006 VOL 313 SCIENCE
... Bees are one of the best studied species groups in this respect. Studies show a marked decline in the distribution of populations at national scales and in abundance and richness of populations at the local scale (Wratten et al., 2012;Ghazoul, 2005;Steffan-Dewenter et al., 2005;Biesmeijer et al., 2006;Williams and Osborne, 2009). These have mainly been attributed to habitat loss and fragmentation, intensification of farming, climate change and loss of host plants (Scheper et al., 2014). ...
... Unlike butterflies, that are being monitored in a standardized way by citizen scientists in more than 10 European countries (van Swaay et al., 2008), large-scale surveying of bees by laypersons is challenging because bee species are difficult to identify. Studies examining trends in bee abundance are therefore invariably small-scaled while large scale trends are based on bee distribution data (Biesmeijer et al., 2006), which generally underestimates population trends. There are now advanced proposals for standardized monitoring of pollinators in EU member states (Potts et al., 2021). ...
Full-text available
The abundance and diversity of plants and insects are important indicators of biodiversity, overall ecosystem health and agricultural production. Bees in particular are interesting indicators as they provide a key ecosystem service in many agricultural crops. Worldwide, habitat loss and fragmentation, agricultural intensification and climate change are important drivers of plant and bee decline. Monitoring of plants and bees is a crucial first step to safeguard their diversity and the services they provide but traditional in situ methods are time consuming and expensive. Remote sensing and Earth observation have the advantages that they can cover large areas and provides repeated, spatially continuous and standardized information. However, to date it has proven challenging to use these methods to assess small-scaled species-level biodiversity components with this approach. Here we surveyed bees and flowering plants using conventional field methods in 30 grasslands along a land-use intensity gradient in the Southeast of the Netherlands. We took RGB (true colored Red-Green-Blue) images using an Unmanned Aerial Vehicle (UAV) from the same fields and tested whether remote sensing can provide accurate assessments of flower cover and diversity and, by association, bee abundance and diversity. We explored the performance of different machine learning methods: Random Forest (RF), Neural Networks (NNET) and Support-Vector Machine (SVM). To evaluate the effect of the spatial resolution on the accuracy of the estimates, we tested all approaches using images at the original spatial resolution (∼ 0.5 cm) and re-sampled at 1 cm, 2 cm and 5 cm. We generally found significant relationships between UAV RGB derived estimates of flower cover and in situ estimates of flower cover and bee abundance and diversity. The highest resolution images generally resulted in the strongest relationships, with RF and NNET methods producing considerably better results than SVM methods (flower cover RF R 2 = 0.8, NNET R 2 = 0.79; bee abundance RF R 2 = 0.65, NNET R 2 = 0.54, bee species richness RF R 2 = 0.62, NNET R 2 = 0.52; bee species diversity RF R 2 = 0.54, NNET R 2 = 0.46). Our results suggest that methods based on the coupling of UAV imagery and machine learning methods can be developed into valuable tools for large-scale, standardized and cost-effective monitoring of flower cover and therefore of an important aspect of habitat quality for bees.
... For instance, sunflower blooming stage lasts around four weeks per year [38],which is a short period to fulfil the requirements of wild bee communities. In contrast, the presence of weeds inside or on the edges of the crops, which are more diverse in terms of flowering periods, sizes and shapes, increases pollination rates of wild bees [39] [40] [41] [42]. This goes in line with our study showing that flowering plants pollinated by wild bees are in their majority weeds (93.1%). ...
... In line with our results, previous studies have already indicated that patches of wild vegetation in between the crops provide essential pollen resources when crops are not in flower [43] [37]. In fact, declines in pollinators are known to be linked to local extinctions of wild plants [40]. It is worth remarking that sunflower H. annuus turned out to be neither very abundant (5.7% reads) nor very common (9.1% FOO) floral resource within our study area. ...
Full-text available
Wild bees are known to be efficient pollinators of wild plants and cultivated crops and they are essential ecosystem service providers. However, wild bee populations have been suffering from significant declines in the last decades mainly due to the use of agrochemicals. Within this framework, we aimed to characterize wild bees pollination spectrum (i.e. the community of pollinated flowering plants) in intensive agroecosystems, and describe the environmental variables and wild bee species traits influencing the pollination. To do this, we conducted metabarcoding analyses of pollen loads from wild bees collected in sunflower crops in the French region of Nouvelle-Aquitaine. Our study revealed that wild bees visited flowering plants corresponding to 231 different Operational Taxonomic Units, classified in 38 families of which Asteraceae, Brassicaceae and Apiaceae were the most visited and more than 90% of the visited taxa turned out to be wild flowers. We also analysed the potential effect of environmental variables and wild bee species traits in governing their choice of pollinated plants. The community composition of pollinated plants varied depending on the flowering stages of the sunflower and the farming system. Our results also show that pollination niche breadth (alpha diversity) varied depending on the flowering stages of the sunflower but was not different between organic and conventional farming systems. Regarding wild bee species traits, the community composition of pollinated plants varied in relation to wild bees body sizes and, sociality levels. Our results are consistent with previous studies, suggesting that solitary bees are more specialists when it comes to flower selection than social bees, which are more generalist. The metabarcoding of pollen loads enabled us to draw a global picture of plant-wild bee interactions in an intensive agroecosystem. Our findings support the hypothesis that a higher diversity of weeds may increase wild bee diversity in intensive agroecosystems.
... Insects are key components of biodiversity and provide important ecosystem services, as in the case of those that act as pollinators of many crops and wild plants [1][2][3][4]. It is estimated that pollinators affect 35% of the world's agricultural land and support the Insects 2023, 14, 296 2 of 16 production of 87% of the world's major food crops [5], affecting both their quality and quantity. ...
... More specifically, some important world crops such as melon, zucchini, and apple are almost entirely dependent on pollinating insects [5]. However, we are witnessing a global decline in the abundance and diversity of pollinators [1,3,6,7]. In Europe, with a severe lack of data, it has been estimated that, overall, 9% of bee and butterfly species are threatened, and that regarding the best-known bee species (which represent only 47% of the total), their populations are declining by 37% [3]. ...
Full-text available
Melon is among the most consumed fruits in the world, being a crop that depends almost entirely on insects for its reproduction, which is why it is especially sensitive to declining pollination services. Restoration and maintenance of hedgerows and agricultural borders around crops are generally carried out by sowing flowering herbaceous plants or establishing shrubby species; however, a cost-effective and lower-maintenance alternative for farmers could be as simple as allowing vegetation to regenerate naturally without any management actions. This work aimed to test the effects of three different types of margins (managed herbaceous, managed shrubby, and unmanaged herbaceous) on the overall abundance and richness of wild pollinators in melon crops. The work was performed in three localities in southern Spain over two years. Pollinators were monitored visually using 1 × 1 m sampling squares and pan traps within melon fields. Moreover, crop yield was estimated by measuring fruit weight and the number of seeds. In general, higher abundances of pollinators were observed in melon fields during the second year. In addition, the abundances of Syrphidae, Andrenidae, Apidae (excl. Apis mellifera), and pollinators other than bees, belonging to the orders Diptera, Coleoptera, Hymenoptera, and Lepidoptera, showed higher values in melon fields with shrubby margins than in fields with herbaceous margins (managed or unmanaged). However, no effect of floral margins on the yield of melon crops was found.
... The benefits of understanding relationships that govern these systems and finding traits that enhance them are manifold. In terms of crops, the quality and yield of the produced fruits and seeds increases several times, while in terms of pollinating insects, the conservation of their diversity is enhanced and their number is increased, which are major ecological issues due to their rapid decline [155], and the environmental benefits they provide [156][157][158][159]. Morphological and phenological traits of flowers [160], nectar secretion [161] and pollen production [162] as well as the release of volatile aromatic substances [163,164] are key traits to investigate for pollinator attraction enhancement. The ultimate goal is usually to exploit heterosis and create a hybrid resulting in increased yield of a mainly self-pollinated or a partially allogamous crop. ...
Full-text available
Cowpea (Vigna unguiculata (L.) Walp.) is a legume with a constant rate of cultivation in Southern European countries. Consumer demand for cowpea worldwide is rising due to its nutritional content, while Europe is constantly attempting to reduce the deficit in the production of pulses and invest in new, healthy food market products. Although the climatic conditions that prevail in Europe are not so harsh in terms of heat and drought as in the tropical climates where cowpea is mainly cultivated, cowpea confronts with a plethora of abiotic and biotic stresses and yield-limiting factors in Southern European countries. In this paper, we summarize the main constraints for cowpea cultivation in Europe and the breeding methods that have been or can be used. A special mention is made of the availability plant genetic resources (PGRs) and their potential for breeding purposes, aiming to promote more sustainable cropping systems as climatic shifts become more frequent and fiercer, and environmental degradation expands worldwide.
... On the contrary the larvae have a wide range of feeding strategies being from aquatic species to phytophagous, fungivores, and saproxylic species or others predacious on a wide range of preys (Rotheray & Gilbert 2011). Unfortunately, hoverflies are declining at an accelerating rate (Biesmeijer et al. 2006;van Eck 2016;Hallmann et al. 2017;Gatter et al. 2020;Hallmann et al. 2021; Morris & Ball 2021; Barendregt et al. 2022). Based on the European Red List of hoverflies which was recently published the 134 species of saproxylic hoverflies represent 15% of the entire European hoverfly fauna of 892 species (Vujić et al. 2022). ...
Full-text available
This paper introduces the importance of veteran trees, tree related microhabitats (TreMs) and their associated hoverfly (Diptera, Syrphidae) fauna. A broader perspective of creating larval habitat is discussed, based on published and novel insights. It focuses on hoverflies that specialise on veteran trees and reflects upon protection and management regimes to conserve veteran trees, TreMs and associated woody habitats. The lack of veteran trees breeding sites can be resolved by tree veteranisation or by using artificial breeding boxes. Whilst protection of veteran trees is essential, enhancement of open areas with flower resources is also vitally important for the survival of saproxylic hoverflies. The larval and adult ecology of only three out of the 134 known European saproxylic species are properly understood. Thus several suggestions are offered for future research aimed at a thorough understanding of the natural history of this unknown and ecologically relevant group of species. The list includes faunistic surveys and investigations into population dynamics, dispersal capacity and habitat preferences. Alongside this research there is a need to investigate the creation of breeding sites including veteranisation techniques and the use of breeding boxes.
... In plant systems, the potential that climate or land use changes may disrupt plant-pollinator interactions is of particular concern. This is because many insect pollinators have faced significant global declines (Hallmann et al., 2017;Potts et al., 2010;Soroye et al., 2020;Thomann et al., 2013;Winfree et al., 2011), and these declines have been accompanied by concomitant reductions in insect-pollinated plants (Biesmeijer et al., 2006). ...
Full-text available
Contemporary anthropogenic changes in climate and landscape form a complex set of selective pressures acting on natural systems, yet, in many systems, we lack information about both whether and how organisms may adapt to these changes. In plants, research has focused on climate-induced changes in phenology and the resultant potential for disruption of plant-pollinator interactions, however, there remains a paucity of knowledge regarding how other pollinator-mediated traits may be involved in the adaptive response. Here, we use resurrection experiments to investigate the phenotypic basis of adaptation in a mixed-mating system plant, the common morning glory (Ipomoea purpurea). Specifically, we measure temporal and spatial changes in traits grouped into three categories relevant to plant-pollinator interactions - floral morphology, floral rewards, and floral phenology. We show a significant temporal increase in corolla size and shift to earlier flowering times, as well as a potential for increased investment in floral rewards, all of which are driven primarily by populations at more northern latitudes. Additionally, we find evidence for directional selection on floral morphology and phenology and evidence of balancing selection acting on anther-stigma distance. Overall, these results show an adaptive response in line with greater investment in pollinator attraction rather than self-pollination and fine-scale spatial differences in adaptive potential.
Urbanization, among the most widespread and multifaceted anthropogenic change drivers, exerts strong influences on a diversity of ecological communities worldwide. We have begun to understand how urbanization affects species diversity, yet we still have limited knowledge about the ways that species interactions are altered by urbanization. We have an especially poor understanding of how urbanization influences stress-buffering mutualisms, despite the high levels of multivariate stress that urban organisms must overcome and the importance of these interactions to the fitness of many organisms. In this study, we investigated the effects of urbanization on a mutualism between tree cholla cacti (Cylindropuntia imbricata) and visiting ants. We first examined how plant size, ant species composition, and ant activity varied on C. imbricata across an urbanization gradient (urban, suburban, wild) in and around Albuquerque, NM. Ant species composition and activity varied significantly across the urbanization gradient, with ant communities from wildlands having the highest activity and the most dissimilar species composition compared to both suburban and urban sites. In contrast, plant size remained constant regardless of site type. We then experimentally assessed how nectar levels influenced ant aggressive encounters with proxy prey (Drosophila melanogaster larvae) on C. imbricata across urban and wild sites. Ants were more likely to discover, attack, and remove proxy prey in wild sites compared to urban sites; they also performed these behaviors more quickly in wild sites. Nectar supplementation had weaker effects on ant aggression than urbanization, but consistently increased the speed at which aggressive behaviors occurred. Future studies that examine nectar quality and herbivorous arthropod abundance may help explain why this strong difference in ant composition and aggression was not associated with lower plant fitness proxies (i.e. size traits). Nevertheless, this study provides unique insight into the growing body of work demonstrating that mutualisms vary significantly across urbanization gradients.
Technical Report
Resumo O efeito da queima controlada foi avaliado na fitofisionomia do cerrado stricto sensu da Floresta Nacional de Silvânia, Goiás, estimando a riqueza e abundância das espécies em duas áreas: uma sob efeito do fogo e uma área controle, para testar a hipótese que a presencia do fogo sobre a vegetação do cerrado, modifica a disponibilidade dos recursos utilizados pelas abelhas, pelo que a área queimada pode apresentar uma diferença na diversidade de abelhas em relação com a área controle. Para a coleta dos espécimenes foram aplicados três métodos de coleta, usando estímulos físico-químicos e rede entomológica. Foram coletados 783 indivíduos pertencentes a 30 espécies em duas famílias (Apidae e Halictidae), no perfil de diversidade encontraram-se diferencias significativas na riqueza estimada da área controle (94%) e na queimada (72%), a completitude amostral permitiu inferir um valor de cobertura num 97.9% e a ensamblagem de abelhas não detectadas foi de 2.08 na área controle e 10.07 na queimada, faltando as espécies raras ou críticas para a completitude amostral. Se apresentaram diferenças significativas na comparação dos métodos de coleta (K= 59.380; P-valor de 0.001 com uma α 0.05) e sobre os estímulos físico-químicos se encontrou um efeito significativo da essência 5 (Eucaliptol) sobre abundância das espécies e um efeito da cor laranja sobre a riqueza nas duas áreas. Nossos resultados sugerem que a queima controlada tem um efeito negativo na diversidade de abelhas, pelo qual é preciso fazer amostragem em diferentes épocas do ano e com maior esforço de amostragem.
Bees are important pollinators that have been negatively impacted by anthropogenic environmental changes, such as urbanization. In addition, urban development can reduce and degrade the natural habitat of bees by increasing the proportion of impervious surfaces, decreasing green areas and increasing the number of exotic ornamental plants. However, cities can provide refuge for bees because they provide an environment with a wide variety of nesting and foraging resources. The objective of our study was to evaluate the richness and abundance of bees, their respective functional groups, and community composition along with an urbanization gradient in 21 locations distributed among six medium‐sized Brazilian cities (with populations between 80 000 and 170 000 inhabitants). We also evaluated the effect of richness, number of plants and proportion of native plants. We collected a total of 132 species of bees. Total bee richness decreased with increasing impervious cover and increased with landscape heterogeneity, which also had a positive effect on the richness of above‐ground nesting bees and generalist bees. Regarding abundance data, solitary bees and belowground‐nesting bees were positively influenced by the increase in grass cover. The total number of native and exotic plants collected positively influenced the total abundance of bees, as well as the abundances of eusocial bees, which nest above‐ and belowground, and generalists. The proportion of native plants positively influenced the total richness and abundance of specialist bees. Our results indicate that medium‐sized urban areas may be home to a wide diversity of bee species, but species that nest in the soil and specialist species may be more sensitive to urbanization and the decrease in the supply of floral resources.
Full-text available
Fenitrothion, an organophosphorus insecticide, has been used as a larvicidal spray against spruce budworm (Choristoneura fumiferana (Clem.) Lepidoptera: Tortricidae) over wide areas of forest in New Brunswick, Canada, since 1969. The important pollinators of lowbush blueberries in the region are native wild bees. Populations of these insects appear to have been severely reduced on fields within areas adjacent to where Fenitrothion has been used and residues have been found in carcasses of both honey bees and native bees. From that evidence, together with high toxicity of Fenitrothion to bees, and the area covered by their foraging ranges, it is concluded that blueberry fields and their immediate surrounds received doses of the pesticide. Because blueberries require outcrossing by bees, it is believed that crop failures have, in part, been caused by drifts or indiscriminate applications, or both, of the pesticide.
Full-text available
The number of interactions with flower visitor species differs considerably among insect pollinated plants. Knowing the causes for this variation is central to the conservation of single species as well as whole plant–flower visitor communities. Species specific constraints on flower visitor numbers are seldom investigated at the community level. In this study we tested whether flower size parameters set constraints on the morphology of the potential nectar feeding visitors and thus determine the number of visitor species. We studied three possible constraints: the depth and width of tubular structures hiding the nectar (nectar holder depth and width) and the size of flower parts that visitors can land on (size of the alighting place). In addition we assess the role of flower abundance on this relationship. We hypothesized that the stronger size constraints and the smaller flower abundance, the smaller the number of visitor species will be. Our study of a Mediterranean plant–flower visitor community revealed that nectar holder depth, nectar holder width and number of flowers explained 71% of the variation in the number of visitor species. The size of the alighting place did not restrict the body length of the visitors and was not related to visitor species number. In a second step of the analyses we calculated for each plant species the potential number of visitors by determining for each insect species of the local visitor pool whether it passed the morphological limits set by the plant. These potential numbers were highly correlated with the observed numbers (r2=0.5, p<0.001). For each plant species we tested whether the observed visitors were a random selection out of these potential visitors by comparing the mean of the observed and expected proboscis length distributions. For most plant species the observed mean was not significantly different from the random means. Our findings shed light on the way plant–flower visitor networks are structured. Knowing the constraints on interaction patterns will be an important prerequisite to formulate realistic null models and understand patterns of resource partitioning as well as coevolutionary processes.
Full-text available
Changes in the abundance of species—especially those that influence water and nutrient dynamics, trophic interactions, or disturbance regime—affect the structure and functioning of ecosystems. Diversity is also functionally important, both because it increases the probability of including species that have strong ecosystem effects and because it can increase the efficiency of resource use. Differences in environmental sensitivity among functionally similar species give stability to ecosystem processes, whereas differences in sensitivity among functionally different species make ecosystems more vulnerable to change. Current global environmental changes that affect species composition and diversity are therefore profoundly altering the functioning of the biosphere.
Full-text available
Habitat degradation and climate change are thought to be altering the distributions and abundances of animals and plants throughout the world, but their combined impacts have not been assessed for any species assemblage. Here we evaluated changes in the distribution sizes and abundances of 46 species of butterflies that approach their northern climatic range margins in Britain-where changes in climate and habitat are opposing forces. These insects might be expected to have responded positively to climate warming over the past 30 years, yet three-quarters of them declined: negative responses to habitat loss have outweighed positive responses to climate warming. Half of the species that were mobile and habitat generalists increased their distribution sites over this period (consistent with a climate explanation), whereas the other generalists and 89% of the habitat specialists declined in distribution size (consistent with habitat limitation). Changes in population abundances closely matched changes in distributions. The dual forces of habitat modification and climate change are likely to cause specialists to decline, leaving biological communities with reduced numbers of species and dominated by mobile and widespread habitat generalists.
Full-text available
Causal attribution of recent biological trends to climate change is complicated because non-climatic influences dominate local, short-term biological changes. Any underlying signal from climate change is likely to be revealed by analyses that seek systematic trends across diverse species and geographic regions; however, debates within the Intergovernmental Panel on Climate Change (IPCC) reveal several definitions of a 'systematic trend'. Here, we explore these differences, apply diverse analyses to more than 1,700 species, and show that recent biological trends match climate change predictions. Global meta-analyses documented significant range shifts averaging 6.1 km per decade towards the poles (or metres per decade upward), and significant mean advancement of spring events by 2.3 days per decade. We define a diagnostic fingerprint of temporal and spatial 'sign-switching' responses uniquely predicted by twentieth century climate trends. Among appropriate long-term/large-scale/multi-species data sets, this diagnostic fingerprint was found for 279 species. This suite of analyses generates 'very high confidence' (as laid down by the IPCC) that climate change is already affecting living systems.
A general binomial mixture model is proposed for the species accumulation function based on presence-absence (incidence) of species in a sample of quadrats or other sampling units. The model covers interpolation between zero and the observed number of samples, as well as extrapolation beyond the observed sample set. For interpolation (sample-based rarefaction), easily calculated, closed-form expressions for both expected richness and its confidence limits are developed (using the method of moments) that completely eliminate the need for resampling methods and permit direct statistical comparison of richness between sample sets. An incidence-based form of the Coleman (random-placement) model is developed and compared with the moment-based interpolation method. For extrapolation beyond the empirical sample set (and simultaneously, as an alternative method of interpolation), a likelihood-based estimator with a bootstrap confidence interval is described that relies on a sequential, AIC-guided algorithm to fit the mixture model parameters. Both the moment-based and likelihood-based estimators are illustrated with data sets for temperate birds and tropical seeds, ants, and trees. The moment-based estimator is confidently recommended for interpolation (sample-based rarefaction). For extrapolation, the likelihood-based estimator performs well for doubling or tripling the number of empirical samples, but it is not reliable for estimating the richness asymptote. The sensitivity of individual-based and sample-based rarefaction to spatial (or temporal) patchiness is discussed.
The EU-funded research project ALARM will develop and test methods and protocols for the assessment of large-scale environmental risks in order to minimise negative human impacts. Research focuses on the assessment and forecast of changes in biodiversity and in the structure, function, and dynamics of ecosystems. This includes the relationships between society, the economy and biodiversity.