BIOLOGICAL
CONSERVATION
Biological Conservation 123 (2005) 271–278
www.elsevier.com/locate/biocon
Grouping and prioritization of vascular plant species
for conservation: combining natural rarity and management need
Meelis Pärtel *, Rein Kalamees, Ülle Reier, Eva-Liis Tuvi, Elle Roosaluste,
Ain Vellak, Martin Zobel
Institute of Botany and Ecology, University of Tartu, Lai 40, Tartu 51005, Estonia
Received 1 April 2004
Abstract
National and International Red Lists and Legal Acts specify species with conservation needs, mainly on the basis of personal
experiences. For effective conservation we need scientifically justified prioritization and grouping of these species. We propose a
new combined approach where species are grouped according to the similar activities needed for their conservation. We used the
national list of vascular plant species with conservation need for Estonia (301 species), and linked these species to eight qualitative
conservation characteristics, four reflecting natural causes of rarity (restricted global distribution; restricted local distribution within
a country; always small populations; very rare habitat type), and four connected with nature management (species needing the management of semi-natural grasslands; species needing local disturbances like forest fires; species needing traditional extensive agriculture; species which may be threatened by collecting). Only one positive association occurred among the characteristics – between
restricted local distribution and small size of populations. Thus, natural causes of rarity and management aspects are not overlapping, and both should be used in conservation activities. Species grouping by different conservation characteristics allows one to
focus on species groups with similar conservation needs instead of individual species. Prioritization of species with conservation
needs can be based on the number of conservation characteristics that are associated with a particular species. Our prioritization
did not correlate with the categories of the national Red Data Book, but a positive association was found with legal protection categories. The legislation, however, covers only the natural causes of rarity. We propose a new combined approach for plant speciesÕ
conservation planning that starts by considering human induced rarity and progresses through to natural rarity causes.
2004 Elsevier Ltd. All rights reserved.
Keywords: Conservation; Human influence; Protected species; Rarity; Red Data Book; Threatened species
1. Introduction
There is now a growing worldwide concern about the
status of biodiversity. The IUCN Red List is being
developed as one of the tools that helps to organize biodiversity conservation (Lamoreux et al., 2003). In recent
years, Red Lists have enjoyed an increasingly prominent
role in guiding national conservation activities (Gärdenfors, 2001). In Europe, there are also lists of species
*
Corresponding author. Tel.: +372 737 6234; fax: +372 737 6222.
E-mail address: [email protected] (M. Pärtel).
0006-3207/$ - see front matter 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.biocon.2004.11.014
that deserve attention across all the European countries
and are listed in the annexes of the European Commission Habitats Directive (1992; 92/43).
Species listed in Red Data Books, lists of species protected by national laws, and species in EC Directives are
all accorded certain Ôconservation statusÕ, i.e. they are
considered to be endangered by some kind of factor
on a certain scale, and active or passive means have to
be taken to stabilize or improve their status. Red Lists
describe how threatened a species is (low number of
localities found or low number of individuals), and what
the major reasons of its decline may be (Hilton-Taylor,
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M. Pärtel et al. / Biological Conservation 123 (2005) 271–278
2000). Habitat loss, direct exploitation, indirect human
influence through changing local ecological interactions,
natural disasters, pollution and intrinsic factors (unfavorable species traits) have been listed among the main
threats. Such information is frequently based only on
the personal experience of a few conservation biologists;
knowledge is often limited. Conservation legislation,
however, also includes other types of arguments such
as commercial importance and aesthetics. The conservation assessment of different taxonomic groups is unequal. For example, conservation priorities for
European birds have already been assessed scientifically
10 years ago (Tucker et al., 1994). Works on insects,
plants and fungi are still very preliminary, probably
due to larger numbers of species and smaller numbers
of people working with them.
Biodiversity conservation needs careful planning (e.g.
Younge and Fowkes, 2003). An example is a scientifically reasoned action plan for a particular species (Palmer, 1996). The number of species with conservation
needs has, however, increased to a level where we no
longer have the time and resources to elaborate action
plans for each individual taxon. When focusing on some
subjectively selected ÔhotÕ species, the status of overall
diversity may worsen. Instead, one might collect a kind
of general information about the possible factors and
mechanisms behind the real or potential decrease of the
local or global abundance and distribution area of these
species. On the basis of such information, one could prioritize species conservation needs and establish groups of
species that could be subjected to similar action plans.
Besides being important for practical nature conservation, the study of the causes of plant species rarity
has been of fundamental importance for understanding
the distribution and dynamics of plant species (Kunin
and Gaston, 1997; Rosenzweig, 1997). There have been
two predominating approaches to the study of possible
causes of plant rarity. The first Ôinductive approachÕ
has focused on the comparative study of the traits of
rare and common plant species. Despite high expectations, the results of such studies have not always made
much conceptual advance, since no clear differences between the traits of rare and common plant species have
emerged (Bevill and Louda, 1999; Murray et al., 2002)
and connections between traits and rarity are evidently
context-dependent (e.g. Pilgrim et al., 2004). Until the
ecological mechanisms behind plant rarity are unveiled,
one cannot expect too much for practical species conservation from the study of species traits.
The second Ôdeductive approachÕ is based on classifying plant species into so-called rarity categories according to the nature of their distribution and habitat
requirements. Rabinowitz (1981) offered a general
scheme where species were classified into categories
according to their geographic range, habitat specificity
and local population size. These categories offer a gen-
eral hypothetical explanation as to why a species is rare.
Species with narrow geographic range may be rare for
historical reasons. In the case of habitat specificity, the
basic reasons of rarity are of evolutionary origin, but
habitat destruction may play a role as well. If local populations are small, local factors such as biotic interactions and human impact are probable causes of rarity.
There are rather few studies that have attempted to
use RabinowitzÕs scheme in regard to the flora of certain
regions, e.g. British Isles (Rabinowitz et al., 1986),
France (Médail and Verlaque, 1997), Spain (Blanca
et al., 1998) and Amazonia (Pitman et al., 1999). Until
now, such an approach has been mostly theoretical
and the link to practical conservation has been weak.
In particular, one must note that human impact is not
specifically considered in RabinowitzÕs system.
There is, however, also a third Ôsynthetic approachÕ,
which tries to combine the two previous ones and study
plant traits in a wider geographic context or to screen
longer lists of plant species (Lahti et al., 1991; Saetersdal, 1994; Gustafsson, 1994; Kull et al., 2002; Rogers
and Walker, 2002). Though most of these trials have evidently not yet reached the stage where results could be
useful for practical conservation, this approach clearly
has higher application potential than the two previous
ones, since it indicates the main threats for species and
the main habitats for rare species. Successful examples,
where the link to practical conservation already exists,
include priority analysis for Central European plants,
where threat status was combined with information
about world-wide distribution (Schnittler and Günther,
1999), and a statistical study on rarity and threat factor
relations in Iberian flora (Lozano et al., 2003).
Our intention is to develop the synthetic approach to
the stage where it can both help to understand possible
causes of plant rarity in a particular region, as well as to
meet the needs of practical nature conservation, like the
elaboration of conservation priorities within the list of
species of conservation interest and the grouping of
plant species according to the similar activities needed
for their conservation. Many earlier decisions about
conservation status and possible threats rely on tradition, not on analysis of scientific information. In the
ideal case, determination of the status of a management
plan for species has to rely on scientific information
about the distribution and ecology of the target species.
Because of that, there is an evident need to screen the
lists of species with conservation need in relation to factors responsible for rarity.
In particular, we aimed to analyze the national list of
vascular plant species with conservation need in order to
understand the main possible causes of plant rarity, to
suggest new priority categorization within the list and
to group plant species according to different conservational aspects. Grouping could make it possible to compile management plans, not for single species, but for the
M. Pärtel et al. / Biological Conservation 123 (2005) 271–278
whole set of species. In this way, the national plant
diversity would be protected more efficiently. We used
the full list of species with conservation status in Estonia
– a small country with a well-known vascular plant flora
and a long tradition of nature conservation – as a model
for the survey (Sepp et al., 1999). We tested whether our
conservation characteristics are related to each other,
and how our conservation characteristics are related to
the present conservation legislation and national Red
Data Book criteria. Finally we propose a new synthetic
approach for plant species conservation that starts by
considering human induced rarity and progresses
through to natural rarity causes.
2. Methods
The national list of the vascular plant species with
conservation need was compiled on the basis of the lists
of legally protected vascular plant species of Estonia
(Kukk, 1999), plant species in the Red Data Book of
Estonia (Lilleleht, 1998), as well as the species from Annexes of the EC Habitats Directive (1992; 92/43) that are
found in Estonia.
The vascular plant flora of Estonia contains 1441 species and 185 of them are legally protected in three priority categories (Kukk, 1999). The Red Data Book of
Estonia lists 309 vascular plant species and infraspecies
taxa. These are divided into five ordinal categories
(Endangered, Vulnerable, Rare, Care Demanding, and
Indeterminate). Annexes of the Habitats Directive list
21 vascular plant species that occur also in Estonia. In
order to make the lists comparable, we excluded all
infraspecific taxa and microspecies with no clear taxonomic status from the genera Alchemilla, Crataegus,
Euphrasia, Hieracium, Pilosella, Rosa and Taraxacum,
as also suggested by Schnittler and Günther (1999).
The lists largely overlapped, and the final summarized
national list of plant species with conservation need
was found to consist of 301 species.
In order to analyze the list of plant species of conservation status in Estonia, each species was assessed on
the basis of the following eight qualitative conservation
characteristics. We used both literature and our own
personal experiences.
1. Restricted global distribution. We used the distribution maps by Hultén and Fries (1986) and categorized
a species as having narrow geographic range when it
was found only in Europe. In all other cases, it was
classified as having a wide geographic range.
2. Restricted local distribution within Estonia. We used
the maps by Kull et al. (2002) and classified a species
as having a small number of local populations when it
was represented in less than 5% of 6 0 · 10 0 (ca. 100
km2) grid cells from the total of 494.
273
3. Small population size. Species were classified into two
categories according to whether their local populations are always small (approximately less than 300
mature individuals) or not. We used the information
from Lilleleht (1998), Kukk (1999), and our own
unpublished data.
4. Very rare habitat. A species was considered to be a habitat specialist if it occurred only in a very rare habitat
type, like limestone escarpment, spring fens, rocky outcrops, open sand, oligotrophic lakes (Paal, 1998).
5. Dependence on grassland management. All species
whose main habitats are seminatural grasslands
(Kukk and Kull, 1997; Kukk, 1999) were classified
as dependent on grassland management.
6. Dependence on local natural and human-induced disturbances. There are a number of species whose
regeneration takes place mostly either in small gaps
or in disturbed areas (e.g. burned forests). Due to forest management, smaller fires are extremely rare
events. Published information about particular species in Estonia is extremely scarce (e.g. Pilt and Kukk,
2002), so we based our assessment mostly on Kukk
(1999) and on our own work (Reier et al., 2005).
7. Dependence on traditional extensive agriculture. These
species are mainly weeds, which were once common
in agricultural landscapes but that have declined tremendously or have even become extinct due to the
application of new technologies. Particular species
were identified according to Kukk (1999).
8. Possible threat due to collecting. Species potentially
threatened by collection because they are either
medicinal or decorative plants were specified according to personal information.
The two first characteristics are both related to distribution, but at two very different scales. There are examples where the species rarity measurement differs
dramatically between scales (Hartley and Kunin,
2003). The last four characteristics represent different
kinds of human influence relevant to the country. We
did not consider those threats that are unlikely to occur
in Estonia, such as natural disasters.
When each species has been screened according the
qualitative features described above, one may generalize
the results in two ways. First, one may classify species
into groups threatened by the same major factors.
Thereafter these groups of species may be targeted for
the elaboration of conservation management plans. Second, species may be ranked according to their conservation status by giving a higher rank to species that are
associated with a higher number of conservation
characteristics.
We analyzed the co-occurrences of different conservation characteristics by principal component analysis
(PCA) with eight characteristics as factors and 301
species as cases. A similar approach has been used
274
M. Pärtel et al. / Biological Conservation 123 (2005) 271–278
successfully before in other regions (Given and Norton,
1993; Lozano et al., 2003). In addition, the Fisher Exact
test was used to discover associations between factor
pairs. The interrelation of different conservation characteristics with the species categorization according to legislation and according to the Red Data Book was
studied with the help of Spearman rank correlation.
Existing species categorization was coded so that a
higher number was given to the most threatened or rare
species.
3. Results
The distribution of the conservation characteristics
among the species of conservation need varied a lot. Restricted global distribution was the most common conservation characteristic, and it was associated with 38% of
species of conservation need. Other common conservation characteristics included restricted local distribution
(28%), dependence on grassland management (32%),
threat due to collecting (31%), and always having small
populations (21%). The least common conservation characteristic was very rare habitat, which was associated
with 7% of the species. Other less frequent conservation
characteristics were: dependence on natural or humaninduced disturbance and dependence on traditional extensive agriculture, both associated with 10% of the species.
7
1
1
6
2
PCA on conservation characteristics revealed that the
first axis described 17.2 and the second axis 16.9 percent
of the total variation (Fig. 1). On the ordination diagram, all conservation characteristics show very little
overlap. There was just one significant positive association between conservation characteristics: restricted local distribution and small size of populations (Fisher
exact test, two-tail, P = 0.026). Significant negative associations were more common: restricted global distribution and threat due to collecting (P = 0.020), restricted
local distribution and threat due to collecting
(P = 0.007), restricted local distribution and dependence
on grassland management (P = 0.037), threat due to collecting and dependence on traditional agriculture
(P < 0.001). Consequently, our conservation characteristics evidently describe very different causal mechanisms
behind rarity.
Most species were associated with one or two characteristics (31% and 37%, respectively), 15% were associated with three, 5% with four, and 1% with five
characteristics. For 11% of the species, none of the eight
conservation characteristics were considered to be
important.
The relation of different conservation characteristics
to conservation categories according to Estonian legislation and the national Red Data Book is presented in
Table 1. Categories in the present laws for species protection were related to restricted local distribution, small
2
Principal Component 2 (16.9%)
5
4
3
8
Global distribution
3
4
Small population
6
5
Grassland
Rare habitat
7
Disturbance
Local distribution
8
Agriculture
Collecting
Principal Component 1 (17.2%)
Fig. 1. Principal component analysis of eight conservation characteristics for 301 vascular plant species with conservation need in Estonia. Projection
of the conservation characteristics (top left) and species for each characteristic (filled circles) on the factor-plane. Conservation characteristics include:
(1) restricted global distribution; (2) restricted local distribution within Estonia; (3) always small populations; (4) very rare habitat type; (5) species
needing management of semi-natural grasslands; (6) species needing small-scale disturbances (e.g. forest fires); (7) species needing traditional
extensive agriculture; (8) species which may be threatened by collecting.
M. Pärtel et al. / Biological Conservation 123 (2005) 271–278
275
Table 1
Relations of our conservation characteristics to existing conservation legislation (n = 179) and the Red Data Book categorization (n = 270) according
to Spearman rank correlation
Restricted global distribution
Restricted local distribution
Small population size
Very rare habitat
Dependence on grassland management
Dependence on local disturbances
Dependence on traditional agriculture
Possible threat due to collecting
Protection categories according to legislation
National Red Data Book categories
r = +0.07,
r = +0.46,
r = +0.29,
r = +0.18,
r = –0.05,
r = +0.04,
r = –0.02,
r = –0.21,
r = 0.11, P = 0.071
r = +0.15, P = 0.014
r = +0.11, P = 0.066
r = +0.06, P = 0.291
r = –0.06, P = 0.363
r = +0.06, P = 0.298
r = –0.13, P = 0.038
r = +0.11, P = 0.077
P = 0.355
P < 0.001
P < 0.001
P = 0.014
P = 0.476
P = 0.622
P = 0.770
P = 0.005
population size, and very rare habitat. There was a negative correlation between threat due to collecting and the
legislation. In the case of the Red Data Book, there was
only a single significant positive correlation: species with
restricted local distribution had mostly been placed in a
high category. Species with traditional agricultural management need were mostly in a low category. The sum of
conservation characteristics was correlated with the protection categories according to legislation (n = 179,
r = 0.28, P < 0.001), but not with the categories of the
Red Data Book (n = 270, r = 0.08, P = 0.191).
4. Discussion
The possible causes of rarity may be classified into two
broad categories: Ônatural rarityÕ and rarity due to unsuitable human activity. We showed that these categories are
not overlapping and should be used in combination. The
existing conservation system, however, is mainly considering just the first one. Each particular cause of rarity can
describe a group of species that need similar conservation
measures. Thus, same strategies can be used for several
species, not just for individual species.
Quite a large number of rare species show a small distribution area on a global scale, i.e. their rarity may have
Ôbiogeographic reasonsÕ. In addition, similarly to the situation in Finland (Lahti et al., 1991), the great majority
of rare plant species in Estonia are at the northern margin of their distribution area, i.e. their distribution and
local abundance are restricted by climatic constraints
(Kukk, 1999). Comparative studies of the ecology of
rare and common species have shown that Ôbiogeographic reasonsÕ may have an important role in determining the local abundance of species (Witkowski and
Lamont, 1997; Walck et al., 2001), though particular
processes and mechanisms are not easy to identify. In
such cases, ÔactiveÕ conservation is hardly possible and
nature conservation usually means simply the preservation of particular ecosystems in which the particular species already occurs.
In addition, there are species whose rarity is directly
or indirectly dependent on human activity. Cessation
of management in seminatural grasslands is an important reason for the decrease of the distribution area
and local abundance of many plant species (Linusson
et al., 1998; Austrheim et al., 1999; Cousins and Eriksson, 2001). Contemporary forestry, which prevents wildfires and results in uniform dense stands without natural
gaps, may suppress the regeneration of species whose
regeneration is favored by the suppression of competition due to local disturbances (Uotila, 1996; Pilt and
Kukk, 2002; Korpilahti and Kuuluvainen, 2003; Reier
et al., 2005). Species with low dispersal ability suffer
from fragmentation of habitats – this has been studied,
for example, for many ecosystems in Europe (Graae
and Sunde, 2000; Butaye et al., 2002; Graae et al.,
2004; Bossuyt et al., 2004). In the case of such species,
ÔactiveÕ conservation measures are possible and reasonable. They may include the restoration of former management or disturbance regimes in specially protected
areas, but also the restoration of local populations by
introducing diaspores or transplanting plant individuals
into habitats from which the species has vanished.
In the case of vascular plants, conservation priority
categorization frequently relies on the experience and
intuition of conservation biologists (Sutherland et al.,
2004). The current approach may give a more objective
basis for prioritization, since one may assume that the
more conservation characteristics a species has been assigned, the higher is the overall risk that the species will
become extinct in the particular region under consideration. According to that, one can assign different status
to species in the conservation lists. Analysis of conservation characteristics over the whole list of species with
conservation need would furnish conservationists with
a powerful objective tool, confirming or challenging subjective decisions. For example we can put the following
species in the order of conservation priority in Estonia:
(1) Hypericum montanum: found just in Europe, low
number of localities in Estonia, always small populations, needs grassland management and forest disturbances; (2) Dianthus arenarius subsp. arenarius: low
number of localities in Estonia, threat due to collecting,
needs grassland management and forest disturbances;
(3) Filago minima: found just in Europe, low number
M. Pärtel et al. / Biological Conservation 123 (2005) 271–278
of localities in Estonia, needs traditional agriculture; (4)
Asplenium ruta-muraria: very rare habitat type, threat
due to collecting; (5) Viola elatior: needs grassland
management.
The analysis of categories in the Red List of Estonia
(Lilleleht, 1998) revealed no correspondence between the
categories and the number of associated conservation
characteristics. The Estonian Red Data Book is solely
describing restricted distribution in Estonia. Weeds connected to traditional agriculture have been given a low
priority, probably due to psychological reasons. Such
a mismatch indicates that additional analysis of the categories in the Red Data Book of Estonia is needed. The
match was much better when species categories in Estonian legislation were considered. The legislation covers
all aspects of rarity according to Rabinowitz (1981). A
negative association with species threatened by collecting is evidently due to a tradition of including rather
common but esthetical species (e.g., several Orchidaceae
species) in the lowest category. It is remarkable, however, that direct human influence (grassland management, forest disturbances and agriculture) is not
considered at all in the present conservation legislation.
Traditionally, the starting point in plant conservation
has been the identification of rare species (low number
of localities). After that, the possible threats have been
identified. In reality, the rarity of most species is the outcome of multiple and frequently either unknown (or
overlooked) processes. The traditional approach is certainly justified in most cases, but it can be complemented
by the additional approach proposed below. We suggest
that the planning of conservation measures should start
with cases where active conservation is possible, i.e. in
All species with
conservation need
49%
18%
4%
9%
9%
cases when human influence is the most probable force
behind rarity, then we are considering the rest of species
with the order of most probable cause of rarity (Fig. 2).
Almost half (49%) of species with conservation need
can be improved by the proper management. Conservation actions mean support for conservation management, such as traditional grassland management and
agriculture, and prescribed forest disturbances. Public
education is an important aspect as well.
Additional 18% of species are threatened by collecting, and better legal regulation and public education
can help here. Since the cause–effect relationship is relatively evident in management and threat due to collecting, one may expect that either supported management
or restrictive regulation will result in a relatively rapid
positive effect on local biodiversity.
A smaller share of species with conservation need
(4%) depends on the presence of particular rare habitat
types. Some of these types may be rare in a particular region for natural reasons, like rocky habitats, oligotrophic lakes or floodplain and escarpment-associated
forests in Estonia, (cf. Paal, 1998). Other habitat types
may be rather common, but their late successional stages
may be rare due to overwhelming management activities. Old-growth forests and undrained mires serve as
examples for Estonia (Paal et al., 1999; Viilma et al.,
2001). In both cases, the persistence of specific natural
habitat types is mostly dependent on restrictive regulations. Consequently, these habitat types should be
strongly protected in situ.
The subsequent 9% of species with conservation need
have very small populations, evidently for evolutionary
and historical reasons. For instance, a species may be
Conservation measures
in the order of significance:
Management needing species:
support for grasslands, forestry
and agriculture, public education
Threatened by collecting:
better legislation, conservational
control, public education
Rare habitat type:
habitat type conservation
Small populations: population
management, ex situ populations
Low number national localities:
restoration of lost populations
If the main conservation measure
is insufficient, consider secondary ones
276
Small distribution area in the World : protection together with other countries,
rational national protection very difficult, protection of sites is recommended
Fig. 2. Suggested order of vascular plant species conservation planning for Estonia, starting with human induced causes and progressing through to
natural causes of rarity. The situation of most of species can be improved with modified human influence and better legislation.
M. Pärtel et al. / Biological Conservation 123 (2005) 271–278
outside its optimal geographical distribution, it may be a
climatic relict, etc. In such cases, there are expensive
conservation mechanisms available, such as artificial
regeneration of local populations (sowing of seeds,
planting individuals) or ex situ conservation, based on
population viability analyses (Menges, 2000). In order
to avoid extinction due to chance events, the average
population size should be much larger than needed for
a viable population in general.
There are 9% of species with conservation need that
have healthy populations but very limited distribution.
Such species may be rare due to dispersal inadequacy.
For these species, the same measures as mentioned
above may be applicable. In particular, restoration of
historical locations may be justified (Heywood and Iriondo, 2003).
There are 11% of species with conservation need that
are considered to be threatened mainly due to a small
global distribution area, but national dispersal and population sizes are large. These have to be protected internationally, though continuous monitoring of these
species is requested. Schnittler and Günther (1999) used
the term Ôconservation responsibilityÕ for species that can
successfully be protected by the authorities of one region, since the species is present mainly just there.
In addition, if the leading conservation measure is
insufficient, the next measures should also be considered
in proper sequence (see the arrows right of the Fig. 2). It
is not wise to apply population management or population restoration for species that actually need grassland
management or are suffering due to collecting. Similarly,
restoration of abiotic conditions of a plant community
should be followed by the introduction of diaspores
and proper future management of this site (van Diggelen
and Marrs, 2003).
One possibility to include scientific knowledge into
conservation strategies is to collect more evidence-based
information (Sutherland et al., 2004). We have shown
that another important possibility is a synthetic approach, combining different conservation characteristics
and measures in regard to lists of species with conservation need. It allows one to work with species groups with
similar conservation needs instead of individual species,
and to set priorities by assuming that a high number of
different conservation characteristics associated with a
species indicates its vulnerability. Such an approach
has a potential to improve strategies for national plant
diversity conservation.
Acknowledgements
We thank M. Toom, E. Rosén, B, Carlsson, B. Svensson, L. Wallin, M. Moora, J. Liira I. Part and three
anonymous reviewers for valuable discussions and comments. This work was supported by the Estonian Envi-
277
ronmental Investment Centre (grant for Rein
Kalamees), EU 6FP project ALARM (GOCECT2003-506675), Estonian Science Foundation (Grant
numbers 4726, 5815, 5503 and 6229), and Swedish
Institute.
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