GRAPHODERUS BILINEATUS
(: )
Jan Cuppen, Bram Koese & Henk Sierdsema
The dytiscid beetle Graphoderus bilineatus is heavily protected by national and international law. In and more information was gathered on the exact distribution and habitat in the Netherlands. A century ago the species was present in large
parts of the country, but nowadays it proves to be restricted to peat bog areas in the
provinces of Friesland, Overijssel, Utrecht, and Zuid- and Noord-Holland. The main
habitat is ditches and canals with a width between . and m, a depth between
and cm, with clear water and a sparse vegetation. A distribution model predicts
the presence of G. bilineatus with a probability of % or more in kilometre
squares in peat bog areas.
The water beetle Graphoderus bilineatus (Degeer,
) (fig. ) is one of the five Dutch beetle
species protected by the European Habitats
Directive and Dutch Flora- and Faunalaw .
Notwithstanding the national and international
protection status the distribution of G. bilineatus
in the Netherlands was poorly known. The publication of Huijbregts () can be considered
the first step towards a better knowledge. The
discovery by the second author of a new population of G. bilineatus in the Nieuwkoopse Plassen
in was reason for the province of ZuidHolland to request -Nederland to start a study
on the status of the species in this province. This
project was carried out in (Cuppen ).
On request of the Ministry of Agriculture, Nature
and Food Quality, the status of G. bilineatus in
other parts of the Netherlands was investigated
in and (Cuppen & Koese ). In
this paper we provide general information on the
species with detailed notes on distribution and
habitat.
posterior to the middle. The main colour of the
dorsal side are pale yellow and black, the ventral
side is pale yellow. The main differences with
Graphoderus cinereus (Linnaeus, ) (fig. ) and
G. zonatus (Hoppe, ) (fig. ), the two other
Dutch Graphoderus species, are:
The pale yellow transverse band on the middle
of the pronotum is distinctly broader than
the black bands at the posterior and anterior
margins; in the other species the black bands
are broader.
The epipleura of the elytra show a distinct
constriction at the level of the hind margin of
the first sternite, which is absent in both other
species; here the epipleura taper gradually from
base to apex.
The light parts of the dorsal and ventral side are
pale yellow, in both other species these parts are
more yellowish with traces of orange, especially
at the underside of the abdomen.
Graphoderus bilineatus can be easily identified
with the commonly used keys such as Schaeflein
(), Van Nieukerken () or Nilsson &
Holmen ().
Graphoderus bilineatus (fig. ) is a middle-sized
dytiscid beetle with a length of - mm. The
body is broadly oval with its maximum width
The development of the egg, three larval instars
and pupa takes about -. month (Galewski
- GRAPHODERUS BILINEATUS
& Holmen , Hendrich & Balke ), but
we did not find concrete records of this phenomenon.
Figure . Graphoderus bilineatus. Foto Theodoor
Heijerman.
Figuur . Graphoderus bilineatus. Photo Theodoor
Heijerman.
), from mid May to the beginning of
October (Foster ). The presence of third
instar larvae in the first decade of June even
suggests an earlier start of reproduction than mid
May in the Netherlands. Also, two couples of
G. bilineatus, collected on April and
May respectively, did not mate nor did lay
eggs in captivity. However, it seems unlikely that
these activities had already taken place. The larvae
pupate on land, in a shallow pupation room
under mosses, stones, wood, or plant debris, not
far from the water’s edge. The lifecycle is probably
univoltine, the adults dying after the reproduction period. Not much is known about hibernation, possibly on land (Hendrich & Balke
under reference to Foster ) as well as under
water (Nilsson & Holmen ). Foster ()
suggests hibernation between dense, submerged
moss carpets, but actual observations are lacking.
The species is reported to be able to fly (Nilsson
Adults and larvae are carnivorous, feeding on
small invertebrates. The larval morphology
suggests that the larvae feed on cladocerans in
open water (Galewski ), like the younger
instars of Graphoderus zonatus (Denton ).
When this resource is limited the young larvae
spend more time near the bottom in search of
other prey items, as do the older instars, which
are also frequently hunting in dense submerged
vegetation. Food preferences of the adult beetle
are not known for certain as crop contents never
have been investigated. The crops of Graphoderus
cinereus contained, apart from tissue of higher
plants, Chlorophycaeae and Bacillariophycaeae,
remains of Crustacea, Ephemeroptera and
Chironomidae (Deding ). However, only
four larvae were investigated and possibly the
vegetable matter is not consumed by the beetle
itself but by its prey (e.g. ephemeropterans or
chironomids).
The range of Graphoderus bilineatus reaches
from Central-Europe via East-Europe to
western Siberia and from northern Italy, Austria,
Hungary and Romania to southern Scandinavia
(fig. ; based on Foster ). Nilsson & Holmen
() also give Spain, but the species is not
mentioned in the Spanish list (Ribera ). In
the surrounding countries of the Netherlands
G. bilineatus is very rare. It is present only in
some regions in Germany (Hendrich & Balke
), France (Bameul , Foster , Queney
) and Belgium (Bosmans & Van Stalle ,
Dopagne ). In England the species has not
been recorded for nearly a century and can be
considered extinct (Foster ). In Norway it is
recently recorded for the first time (Olsvik ).
Graphoderus bilineatus is rare in Denmark,
but widespread in Sweden and Finland (Holmen
, Nilsson & Holmen ). Large
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2
3
4
Figure -. Habitus of three Graphoderus species, . G. bilineatus, . G. cinereus, . G. zonatus. Collection Naturalis
Leiden (). Photos Roy Kleukers.
Figuur -. Habitus van drie Graphoderus-soorten, . G. bilineatus, . G. cinereus, . G. zonatus. Collectie Naturalis
Leiden (). Foto’s Roy Kleukers.
• Determination of the potential distribution area
in the Netherlands
• Finding reliable characters to separate the larvae
of Graphoderus species
populations are known from the south of
Scandinavia, Russia, Belarus and Ukraine
(Hendrich & Balke ). In West- and CentralEurope the species seems to have declined in
the second half of the th century (Nilsson &
Holmen , Foster , Hendrich & Balke
, Huijbregts ). Despite this decline,
new populations have recently been discovered
in this area, e.g. in the surroundings of Bordeaux
(Bameul ), Bremen (Haesloop ) and
in several nature reserves in the Netherlands
(Huijbregts , Cuppen , Cuppen & Koese
).
In this paper we will focus on the first goal, distribution and habitat. The results with respect to
the different sampling techniques are presented
in a second paper (Koese & Cuppen ), the
development of the distribution model in a third
(Sierdsema & Cuppen ). The study of the
larvae is still in progress and will be published
later.
The main goals of the project were:
• Description of the current distribution and
habitat of Graphoderus bilineatus
• Determination of the best sampling procedure
(macrofauna net versus bottle traps)
Period and investigated areas
The survey on Graphoderus bilineatus took place
in the years and . In total samples
were taken (distributed over localities, x
kilometre squares and x kilometre squares).
- GRAPHODERUS BILINEATUS
Aanwezig
Zuid-Holland
Rest van Nederland
Afwezig
Table . Number of kilometre squares investigated in
(province of Zuid-Holland) and - (rest
of the Netherlands) with presence/absence data for
Graphoderus bilineatus.
Tabel . Aantal onderzochte kilometerhokken met aanafwezigheid van Graphoderus bilineatus in (ZuidHolland) en - (rest van Nederland).
In both years sampling was concentrated between
the end of April to the beginning of June and
mid-August to the end of September. Within
these periods the probability of catching adult
beetles was highest, based on the available Dutch
data.
The aim was to re-investigate the localities where
the species was found between and ,
supplemented with any new findings in and
. As a starting point localities with records
of adults and/or presumed larvae since were
selected from the dataset (compiled by
J. Huijbregts). The exact localities could most
often be traced by the topographical descriptions on the labels, sometimes with assistance
of the collector. The database contained x
kilometre squares (sometimes containing more
than one locality) with reliable records of adult
G. bilineatus since . All records of larvae were
considered unreliable (Huijbregts ). In the
survey localities were investigated in the
province of Zuid-Holland with the Nieuwkoopse
Plassen as the most important area (Cuppen
). A relatively large number of sampling
localities in this survey were controls of localities with doubtful records of larvae or lost adult
material. The study also included a number of
localities which were obviously not suitable for
G. bilineatus. The localities were divided in three
groups according to the results of our survey:
localities were G. bilineatus was found, localities
were the species was not found but probably is
present (potential), and, finally, localities were the
species was not collected and also is not expected.
Sampling procedure
Sampling was performed with a standard macrofauna net (width cm, mesh size . mm),
which was pushed over the bottom and through
the vegetation, or scraped against the banks. The
content of the net was emptied in a white tray
and checked for Graphoderus. The locality was
sampled up to a maximum period of . hours.
Morphometrical measurements included depth
and width or surface of a water body, and thickness of detritus/peat layers. The transparency and
colour of the water and the amount of shade (by
shrubs or trees) were visually assessed. A water
sample was collected in a plastic bottle and the
water was analysed for a number of parameters:
pH, electrical conductivity, chlorinity, alkalinity
and total hardness. The structure of the vegetation was assessed for all major layers (percentage
cover): emergent, floating leaved, submerged,
mosses and algae (flab). Special attention was paid
to floating leaved and submerged plants, which
were also assessed at the species level.
More detailed information on sampling procedures can be found in Cuppen () and
Cuppen & Koese ().
Distribution
The distribution of G. bilineatus in the
Netherlands is given in figure . The map is
based on the database, to which the results
of the present investigation are added. It shows
that prior to the distribution area covered
large parts of the Netherlands with the exception of the Delta region in the southwest, the
northern coastal (often brackish) areas and large
parts of the provinces of Drenthe and Overijssel.
The actual distribution comprises only a minor
part of the country with nearly all records
confined to peat bog areas at the border of the
provinces Utrecht, Zuid- and Noord-Holland in
the centre of the Netherlands, and peat bogs in
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®
°
l
<
-
>
Figure . European distribution map of Graphoderus
bilineatus (based on Foster ).
Figuur . Verspreidingskaart van Graphoderus bilineatus
gebaseerd op Foster ().
Figure . Records of Graphoderus bilineatus in the
Netherlands (database -).
Figuur . Vindplaatsen van Graphoderus bilineatus in
Nederland (bestand -).
Noordwest-Overijssel and adjacent Friesland. The
populations in heath land ponds on sandy soils
in the southern, eastern and central parts of the
Netherlands have severely declined during the last
century. Only one, probably small, population
remains in one of the Oisterwijkse Vennen.
Table gives a survey of the presence and
absence of G. bilineatus in the kilometre squares
investigated during the two projects. The species
was found in about half the examined grid
squares. The differences in recoveries between the
two projects are mainly due to the different starting points. More details can be found in Cuppen
() and Cuppen & Koese ().
is permanent. Most often these waters are
interconnected with each other within a certain
area. Most water bodies in the Netherlands fulfil
these requirements and it is obvious that the
rarity of the species is not caused by rarity of
these conditions. However, most other environmental variables investigated during this project
vary considerably. For a correct interpretation of
the results presented below it should be emphasized that, due to the goals of this project, the
localities were not picked at random. Localities
with records of G. bilineatus were strongly
preferred. It is needless to say that measurements
from hundreds of sampling localities without
G. bilineatus could have been added to the dataset.
In other countries Graphoderus bilineatus is
frequently reported from isolated waters such as
large ponds and lakes of various types (Nilsson
& Holmen , Foster , Hendrich &
Habitat
Our study shows that in the Netherlands localities with Graphoderus bilineatus have in common
that the water is (nearly) stagnant and the water
- GRAPHODERUS BILINEATUS
Figure . Ditch in the
Westbroekse Zodden, a typical
locality for Graphoderus bilineatus
in the Netherlands. Photo
B. Koese.
Figuur . Sloot in de Westbroekse
Zodden, een karakteristieke vindplaats van Graphoderus bilineatus
in Nederland. Foto B. Koese.
Balke ). Only two of our records stem
from more or less isolated waters: the Voorste
Goorven near Oisterwijk and the Wijde Blik in
the Naardermeer nature reserve. Both waters are
very large in comparison with waters entering or
leaving these lakes. The majority of Dutch records
of G. bilineatus originate from ditches (fig. ) and
canals. These waters show a considerable variation
in width (fig. ). No obvious preference for any
of the six classes can be detected. About % of
the records is from ditches with a width less than
metres, quite a contrast with literature. The
narrowest ditch had a width of only . meter.
The distribution of the records over the different
classes of water depth is given in figure . It
shows that G. bilineatus is more frequently
observed in waters with a depth of more than
cm. This observation is in agreement with
literature (Nilsson & Holmen , Foster ,
Hendrich & Balke ). The shallowest water
depth measured was only cm in a ditch at the
Westbroekse Zodden in the summer period; in
the winter the water level had risen to cm.
The soil at sampling localities with G. bilineatus
consisted of either sand or peat with most often
peaty, steep banks. The soil was covered by soft,
muddy peat of a variable thickness, frequently
more than cm. Despite this peat, soils were
never anaerobic, and the water itself was very
clear or only slightly brown coloured by humic
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-
-
-
-
>
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
the width of the water body.
Figuur . Procentuele verdeling van monsterpunten met
en zonder Graphoderus bilineatus met betrekking tot de
breedte van de watergang.
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
the depth of the water body.
Figuur . Procentuele verdeling van monsterpunten met
en zonder Graphoderus bilineatus met betrekking tot de
diepte van de watergang.
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
pH.
Figuur . Procentuele verdeling van monsterpunten
met en zonder Graphoderus bilineatus met betrekking
tot de pH.
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
electrical conductivity.
Figuur . Procentuele verdeling van monsterpunten
met en zonder Graphoderus bilineatus met betrekking
tot electrisch geleidingsvermogen.
- GRAPHODERUS BILINEATUS
According to Holmen () and Hendrich &
Balke () the species tolerates weakly acid
water, circumstances which are encountered in
the Netherlands only in the Voorste Goorven
with a pH between . and . at different
stations and times.
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
hardness.
Figuur . Procentuele verdeling van monsterpunten
met en zonder Graphoderus bilineatus met betrekking
tot hardheid.
compounds. Most localities were situated in the
large seepage areas of the Netherlands, but this
was hardly visible in the field (no milky or rusty
water, no bacterial films at the water surface,
indicative plants species e.g. Hottonia palustris
were not common).
Graphoderus bilineatus is an inhabitant of
unshaded waters, which means that usually no
trees or shrubs are growing on the banks. At some
localities mowing activities were hindered by trees
(most often at dead-ends of ditches), resulting
in accumulation of trembling bog or a richer
emergent vegetation, resulting in a better hidingplace for the beetles. Close to the banks the
shading can increase considerably in the course
of the season, due to the growth of helophytes
on the banks. This of course also depends on the
slope and exposition of the bank.
Graphoderus bilineatus is most often observed
in waters with a pH between and . (fig. ),
which seems to be the normal range abroad.
Electrical conductivity and chlorinity are strongly
correlated in our dataset and therefore only the
results for conductivity are presented (fig. ).
Graphoderus bilineatus is observed in all classes
except the highest (> mS/m). A ‘preference’ for the lower three classes (< mS/m)
is obvious, above this value the presence of
G. bilineatus rapidly declines.
The hardness (ºD), a measure for the total
amount of calcium and magnesium, shows that
G. bilineatus is observed more in the lower three
classes (< ºD)(fig. ) than in the higher three.
The structure, and to a lesser degree the composition, of the vegetation on the sampling localities
is quite variable over the sample sites and also the
season. In springtime (April-May) the water
vegetation is usually sparsely developed and
will be better developed in summer (AugustSeptember), when not cut. The emergent
vegetation (only as far as it stands in the water)
is sparsely developed with a cover of less than %
by Phragmites australis, Carex paniculata, C. acuta,
C. acutiformis and Thelypterus palustris as frequent
and sometimes dominant species. Also the floating leaved vegetation (rooted as well as unrooted)
is most often scarce, but occasionally Nuphar
lutea, Nymphaea alba or Hydrocharis morsus-ranae
are dominating. Potamogeton species are rare.
Surface floating lemnids, though very frequent, are
never dominant on localities with G. bilineatus.
The submerged vegetation is well developed
and often rather rich in species. Dominant and
frequent is Utricularia vulgaris, less often Elodea
canadensis, E. nuttallii, Ceratophyllum demersum,
Potamogeton species, Stratiotes aloides, Hottonia
palustris and Lemna trisulca. Mosses (mostly
Sphagnum) and a floating layer of algae (flab)
are sporadically present.
‒
Figure . Predictive distribution model for Graphoderus bilineatus. In kilometre squares in peat bog areas (red),
the probability of its occurrence is more than % based on electrical conductivity and associative plant species, in
green squares the prediction is based only on electrical conductivity.
Figuur . Voorspellend verspreidingsmodel voor Graphoderus bilineatus. In de rode kilometerhokken in de laagveengebieden is de kans op aantreffen van deze soort meer dan % gebaseerd op electrisch geleidingsvermogen en
geässocieerde plantensoorten, in de groene hokken is deze voorspelling alleen gebaseerd op electrisch geleidingsvermogen.
- GRAPHODERUS BILINEATUS
Potential distribution model
The development of the potential distributional model is reported in Sierdsema & Cuppen
(). The final result is a map (fig. ) that can
be used for future investigations. The map shows,
for peat bog areas only, the kilometre squares (in
red) in which G. bilineatus can be expected with
a probability of more than %. This expectation
is based on electrical conductivity of the water
and the presence of associative plant species. In
the green kilometre squares a probability of more
than % for G. bilineatus is computed on the
basis of electrical conductivity only. For these
squares no floristical data were available. Green
squares are mainly found in the northern part
of the country.
In the first half of the th century G. bilineatus
occurred in large parts of the Netherlands, lacking
only in brackish areas. In the second half of the
th century the species declined severely in all
regions of our country except for peat bogs. The
reasons for this decline surely include acidification of moorland pools by wet and dry acidic
deposition, eutrophication by intensification of
agriculture (use of artificial fertilizers), intensified
use of herbicides and pesticides, re-allotment
and intake of nearly brackish and hard river
water (Rhine). Survival of G. bilineatus in peat
bog areas is probably due to seepage, resulting in a good water quality (poor in nutrients,
relatively low conductivity and total hardness).
Also the relatively low economic value of these
areas for agriculture reduced some of the above
mentioned human influences. The peat bog areas,
functioning as nature reserves, recreation areas
or sources of natural products (fish, reeds) have
changed relatively little during the last century.
The improvement of water management in some
of the areas (stopping, reducing and/or dephosphatizing of river water taken in) probably has
resulted in (re)colonization of the Naardermeer,
Weerribben, Wieden and Nieuwkoopse Plassen
by G. bilineatus in the last decade of the th
century. Most of these areas were not very well
investigated for invertebrates in the past but at
least for the Naardermeer the restoration is well
documented. Eight sites were sampled more or
less regularly for invertebrates from onwards.
Dephosphatizing of intake water from the
IJmeer took place from onwards but, after
problems in the initial stage, was effective from
onwards (Boosten ). Graphoderus
bilineatus was first recorded in at one site,
followed by a second and third site in
(pers. com. G. van Ee). Prior to the discovery of
Graphoderus, the water turbidity strongly declined
resulting in clear water that enabled the development of a closed submerged vegetation including
stoneworts (Characeae) and Najas marina.
The distribution model predicts for the peat bog
regions in the Netherlands the occurrence of
G. bilineatus in x kilometre squares with a
probability of more than % (fig. ). A research
project directed on especially these grid squares
can improve the known distribution of the species
in the Netherlands most succesfully. The predictive model can be validated by use of consistent
sampling techniques and fixed time schedules.
For the validation the assessment of the model
parameters (electrical conductivity, number of
associative aquatic plant species) is necessary.
Many grid squares in the northern peat bog areas
are deficit in floristical data. It is advised to gather
these floristical data first and to add them to the
model. Hereafter, examination of the grid squares
with the highest potentials for G. bilineatus can
be conducted.
The predictive distribution model is based on
measurements, maps and expert judgement. A
major restriction of the model is its limitation
to peat bog soils. To find new localities with
G. bilineatus outside this area one can rely only
on expert judgement. It is recommended to
include in a new research project at least some
heath land ponds in areas inhabited by the species
in former days. Heath land ponds with an unaltered water table, not acidified nor eutrophicated,
seem to be the best ones to look for.
‒
We like to thank everyone (Natuurmonumenten,
State Forestry Service, Water Authority Boards)
who made it possible to investigate the status
of Graphoderus bilineatus in the Netherlands by
giving us permits for collecting and access, boats,
petrol, and information on localities. Gert van Ee
provided information on several localities in the
province of Noord-Holland. We thank Theodoor
Heijerman for the nice photo. Menno Reemer
and Vincent Kalkman (-Nederland) were
very helpful with providing us with permits, and
editing, arrangement and adding of text and illustrations to parts of manuscripts.
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- GRAPHODERUS BILINEATUS
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Verspreiding en biotopen van Graphoderus bilineatus (Coleoptera: Dytiscidae)
De verspreiding en biotopen van de gestreepte waterroofkever Graphoderus bilineatus zijn in
en onderzocht in opdracht van de provincie Zuid-Holland en het Ministerie van . Deze
waterroofkever is wettelijk beschermd middels de Flora- en Faunawet en de Habitatrichtlijn.
Graphoderus bilineatus kwam vroeger in grote delen van Nederland voor, maar is tegenwoordig
vrijwel beperkt tot de grote laagveengebieden in de provincies Friesland, Overijssel, Utrecht en
Noord- en Zuid-Holland. De belangrijkste biotopen in Nederland zijn sloten en kanalen met een
breedte tussen , en meter, een diepte tussen en centimeter met helder water, en meestal
een vrij spaarzame vegetatie van drijvende en submerse waterplanten. Uit het buitenland is
G. bilineatus vooral bekend uit grotere wateren. Op basis van een verspreidingsmodel wordt voor
de laagveengebieden van ons land het potentiële voorkomen van G. bilineatus voorspeld. In
kilometerhokken voorspelt het model de aanwezigheid van deze soort met een waarschijnlijkheid
van meer dan %.
J.G.M. Cuppen
Aquatic Ecology and Water Quality Management Group
Wageningen University and Research Centre
Ritzema Bosweg a
Wageningen
jan.cuppen@wur.nl
B. Koese
-Nederland
Postbus
Leiden
eis@naturalis.nl
H. Sierdsema
Dutch Centre for Field Ornithology /
-University of Amsterdam /
Alterra-Wageningen University and Research Centre
Rijksstraatweg
Beek-Ubbergen
henk.sierdsema@sovon.nl
‒
GRAPHODERUS BILINEATUS
(: )
Jan Cuppen, Bram Koese & Henk Sierdsema
The dytiscid beetle Graphoderus bilineatus is heavily protected by national and international law. In and more information was gathered on the exact distribution and habitat in the Netherlands. A century ago the species was present in large
parts of the country, but nowadays it proves to be restricted to peat bog areas in the
provinces of Friesland, Overijssel, Utrecht, and Zuid- and Noord-Holland. The main
habitat is ditches and canals with a width between . and m, a depth between
and cm, with clear water and a sparse vegetation. A distribution model predicts
the presence of G. bilineatus with a probability of % or more in kilometre
squares in peat bog areas.
The water beetle Graphoderus bilineatus (Degeer,
) (fig. ) is one of the five Dutch beetle
species protected by the European Habitats
Directive and Dutch Flora- and Faunalaw .
Notwithstanding the national and international
protection status the distribution of G. bilineatus
in the Netherlands was poorly known. The publication of Huijbregts () can be considered
the first step towards a better knowledge. The
discovery by the second author of a new population of G. bilineatus in the Nieuwkoopse Plassen
in was reason for the province of ZuidHolland to request -Nederland to start a study
on the status of the species in this province. This
project was carried out in (Cuppen ).
On request of the Ministry of Agriculture, Nature
and Food Quality, the status of G. bilineatus in
other parts of the Netherlands was investigated
in and (Cuppen & Koese ). In
this paper we provide general information on the
species with detailed notes on distribution and
habitat.
posterior to the middle. The main colour of the
dorsal side are pale yellow and black, the ventral
side is pale yellow. The main differences with
Graphoderus cinereus (Linnaeus, ) (fig. ) and
G. zonatus (Hoppe, ) (fig. ), the two other
Dutch Graphoderus species, are:
The pale yellow transverse band on the middle
of the pronotum is distinctly broader than
the black bands at the posterior and anterior
margins; in the other species the black bands
are broader.
The epipleura of the elytra show a distinct
constriction at the level of the hind margin of
the first sternite, which is absent in both other
species; here the epipleura taper gradually from
base to apex.
The light parts of the dorsal and ventral side are
pale yellow, in both other species these parts are
more yellowish with traces of orange, especially
at the underside of the abdomen.
Graphoderus bilineatus can be easily identified
with the commonly used keys such as Schaeflein
(), Van Nieukerken () or Nilsson &
Holmen ().
Graphoderus bilineatus (fig. ) is a middle-sized
dytiscid beetle with a length of - mm. The
body is broadly oval with its maximum width
The development of the egg, three larval instars
and pupa takes about -. month (Galewski
- GRAPHODERUS BILINEATUS
& Holmen , Hendrich & Balke ), but
we did not find concrete records of this phenomenon.
Figure . Graphoderus bilineatus. Foto Theodoor
Heijerman.
Figuur . Graphoderus bilineatus. Photo Theodoor
Heijerman.
), from mid May to the beginning of
October (Foster ). The presence of third
instar larvae in the first decade of June even
suggests an earlier start of reproduction than mid
May in the Netherlands. Also, two couples of
G. bilineatus, collected on April and
May respectively, did not mate nor did lay
eggs in captivity. However, it seems unlikely that
these activities had already taken place. The larvae
pupate on land, in a shallow pupation room
under mosses, stones, wood, or plant debris, not
far from the water’s edge. The lifecycle is probably
univoltine, the adults dying after the reproduction period. Not much is known about hibernation, possibly on land (Hendrich & Balke
under reference to Foster ) as well as under
water (Nilsson & Holmen ). Foster ()
suggests hibernation between dense, submerged
moss carpets, but actual observations are lacking.
The species is reported to be able to fly (Nilsson
Adults and larvae are carnivorous, feeding on
small invertebrates. The larval morphology
suggests that the larvae feed on cladocerans in
open water (Galewski ), like the younger
instars of Graphoderus zonatus (Denton ).
When this resource is limited the young larvae
spend more time near the bottom in search of
other prey items, as do the older instars, which
are also frequently hunting in dense submerged
vegetation. Food preferences of the adult beetle
are not known for certain as crop contents never
have been investigated. The crops of Graphoderus
cinereus contained, apart from tissue of higher
plants, Chlorophycaeae and Bacillariophycaeae,
remains of Crustacea, Ephemeroptera and
Chironomidae (Deding ). However, only
four larvae were investigated and possibly the
vegetable matter is not consumed by the beetle
itself but by its prey (e.g. ephemeropterans or
chironomids).
The range of Graphoderus bilineatus reaches
from Central-Europe via East-Europe to
western Siberia and from northern Italy, Austria,
Hungary and Romania to southern Scandinavia
(fig. ; based on Foster ). Nilsson & Holmen
() also give Spain, but the species is not
mentioned in the Spanish list (Ribera ). In
the surrounding countries of the Netherlands
G. bilineatus is very rare. It is present only in
some regions in Germany (Hendrich & Balke
), France (Bameul , Foster , Queney
) and Belgium (Bosmans & Van Stalle ,
Dopagne ). In England the species has not
been recorded for nearly a century and can be
considered extinct (Foster ). In Norway it is
recently recorded for the first time (Olsvik ).
Graphoderus bilineatus is rare in Denmark,
but widespread in Sweden and Finland (Holmen
, Nilsson & Holmen ). Large
‒
2
3
4
Figure -. Habitus of three Graphoderus species, . G. bilineatus, . G. cinereus, . G. zonatus. Collection Naturalis
Leiden (). Photos Roy Kleukers.
Figuur -. Habitus van drie Graphoderus-soorten, . G. bilineatus, . G. cinereus, . G. zonatus. Collectie Naturalis
Leiden (). Foto’s Roy Kleukers.
• Determination of the potential distribution area
in the Netherlands
• Finding reliable characters to separate the larvae
of Graphoderus species
populations are known from the south of
Scandinavia, Russia, Belarus and Ukraine
(Hendrich & Balke ). In West- and CentralEurope the species seems to have declined in
the second half of the th century (Nilsson &
Holmen , Foster , Hendrich & Balke
, Huijbregts ). Despite this decline,
new populations have recently been discovered
in this area, e.g. in the surroundings of Bordeaux
(Bameul ), Bremen (Haesloop ) and
in several nature reserves in the Netherlands
(Huijbregts , Cuppen , Cuppen & Koese
).
In this paper we will focus on the first goal, distribution and habitat. The results with respect to
the different sampling techniques are presented
in a second paper (Koese & Cuppen ), the
development of the distribution model in a third
(Sierdsema & Cuppen ). The study of the
larvae is still in progress and will be published
later.
The main goals of the project were:
• Description of the current distribution and
habitat of Graphoderus bilineatus
• Determination of the best sampling procedure
(macrofauna net versus bottle traps)
Period and investigated areas
The survey on Graphoderus bilineatus took place
in the years and . In total samples
were taken (distributed over localities, x
kilometre squares and x kilometre squares).
- GRAPHODERUS BILINEATUS
Aanwezig
Zuid-Holland
Rest van Nederland
Afwezig
Table . Number of kilometre squares investigated in
(province of Zuid-Holland) and - (rest
of the Netherlands) with presence/absence data for
Graphoderus bilineatus.
Tabel . Aantal onderzochte kilometerhokken met aanafwezigheid van Graphoderus bilineatus in (ZuidHolland) en - (rest van Nederland).
In both years sampling was concentrated between
the end of April to the beginning of June and
mid-August to the end of September. Within
these periods the probability of catching adult
beetles was highest, based on the available Dutch
data.
The aim was to re-investigate the localities where
the species was found between and ,
supplemented with any new findings in and
. As a starting point localities with records
of adults and/or presumed larvae since were
selected from the dataset (compiled by
J. Huijbregts). The exact localities could most
often be traced by the topographical descriptions on the labels, sometimes with assistance
of the collector. The database contained x
kilometre squares (sometimes containing more
than one locality) with reliable records of adult
G. bilineatus since . All records of larvae were
considered unreliable (Huijbregts ). In the
survey localities were investigated in the
province of Zuid-Holland with the Nieuwkoopse
Plassen as the most important area (Cuppen
). A relatively large number of sampling
localities in this survey were controls of localities with doubtful records of larvae or lost adult
material. The study also included a number of
localities which were obviously not suitable for
G. bilineatus. The localities were divided in three
groups according to the results of our survey:
localities were G. bilineatus was found, localities
were the species was not found but probably is
present (potential), and, finally, localities were the
species was not collected and also is not expected.
Sampling procedure
Sampling was performed with a standard macrofauna net (width cm, mesh size . mm),
which was pushed over the bottom and through
the vegetation, or scraped against the banks. The
content of the net was emptied in a white tray
and checked for Graphoderus. The locality was
sampled up to a maximum period of . hours.
Morphometrical measurements included depth
and width or surface of a water body, and thickness of detritus/peat layers. The transparency and
colour of the water and the amount of shade (by
shrubs or trees) were visually assessed. A water
sample was collected in a plastic bottle and the
water was analysed for a number of parameters:
pH, electrical conductivity, chlorinity, alkalinity
and total hardness. The structure of the vegetation was assessed for all major layers (percentage
cover): emergent, floating leaved, submerged,
mosses and algae (flab). Special attention was paid
to floating leaved and submerged plants, which
were also assessed at the species level.
More detailed information on sampling procedures can be found in Cuppen () and
Cuppen & Koese ().
Distribution
The distribution of G. bilineatus in the
Netherlands is given in figure . The map is
based on the database, to which the results
of the present investigation are added. It shows
that prior to the distribution area covered
large parts of the Netherlands with the exception of the Delta region in the southwest, the
northern coastal (often brackish) areas and large
parts of the provinces of Drenthe and Overijssel.
The actual distribution comprises only a minor
part of the country with nearly all records
confined to peat bog areas at the border of the
provinces Utrecht, Zuid- and Noord-Holland in
the centre of the Netherlands, and peat bogs in
‒
®
°
l
<
-
>
Figure . European distribution map of Graphoderus
bilineatus (based on Foster ).
Figuur . Verspreidingskaart van Graphoderus bilineatus
gebaseerd op Foster ().
Figure . Records of Graphoderus bilineatus in the
Netherlands (database -).
Figuur . Vindplaatsen van Graphoderus bilineatus in
Nederland (bestand -).
Noordwest-Overijssel and adjacent Friesland. The
populations in heath land ponds on sandy soils
in the southern, eastern and central parts of the
Netherlands have severely declined during the last
century. Only one, probably small, population
remains in one of the Oisterwijkse Vennen.
Table gives a survey of the presence and
absence of G. bilineatus in the kilometre squares
investigated during the two projects. The species
was found in about half the examined grid
squares. The differences in recoveries between the
two projects are mainly due to the different starting points. More details can be found in Cuppen
() and Cuppen & Koese ().
is permanent. Most often these waters are
interconnected with each other within a certain
area. Most water bodies in the Netherlands fulfil
these requirements and it is obvious that the
rarity of the species is not caused by rarity of
these conditions. However, most other environmental variables investigated during this project
vary considerably. For a correct interpretation of
the results presented below it should be emphasized that, due to the goals of this project, the
localities were not picked at random. Localities
with records of G. bilineatus were strongly
preferred. It is needless to say that measurements
from hundreds of sampling localities without
G. bilineatus could have been added to the dataset.
In other countries Graphoderus bilineatus is
frequently reported from isolated waters such as
large ponds and lakes of various types (Nilsson
& Holmen , Foster , Hendrich &
Habitat
Our study shows that in the Netherlands localities with Graphoderus bilineatus have in common
that the water is (nearly) stagnant and the water
- GRAPHODERUS BILINEATUS
Figure . Ditch in the
Westbroekse Zodden, a typical
locality for Graphoderus bilineatus
in the Netherlands. Photo
B. Koese.
Figuur . Sloot in de Westbroekse
Zodden, een karakteristieke vindplaats van Graphoderus bilineatus
in Nederland. Foto B. Koese.
Balke ). Only two of our records stem
from more or less isolated waters: the Voorste
Goorven near Oisterwijk and the Wijde Blik in
the Naardermeer nature reserve. Both waters are
very large in comparison with waters entering or
leaving these lakes. The majority of Dutch records
of G. bilineatus originate from ditches (fig. ) and
canals. These waters show a considerable variation
in width (fig. ). No obvious preference for any
of the six classes can be detected. About % of
the records is from ditches with a width less than
metres, quite a contrast with literature. The
narrowest ditch had a width of only . meter.
The distribution of the records over the different
classes of water depth is given in figure . It
shows that G. bilineatus is more frequently
observed in waters with a depth of more than
cm. This observation is in agreement with
literature (Nilsson & Holmen , Foster ,
Hendrich & Balke ). The shallowest water
depth measured was only cm in a ditch at the
Westbroekse Zodden in the summer period; in
the winter the water level had risen to cm.
The soil at sampling localities with G. bilineatus
consisted of either sand or peat with most often
peaty, steep banks. The soil was covered by soft,
muddy peat of a variable thickness, frequently
more than cm. Despite this peat, soils were
never anaerobic, and the water itself was very
clear or only slightly brown coloured by humic
‒
-
-
-
-
-
>
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
the width of the water body.
Figuur . Procentuele verdeling van monsterpunten met
en zonder Graphoderus bilineatus met betrekking tot de
breedte van de watergang.
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
the depth of the water body.
Figuur . Procentuele verdeling van monsterpunten met
en zonder Graphoderus bilineatus met betrekking tot de
diepte van de watergang.
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
pH.
Figuur . Procentuele verdeling van monsterpunten
met en zonder Graphoderus bilineatus met betrekking
tot de pH.
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
electrical conductivity.
Figuur . Procentuele verdeling van monsterpunten
met en zonder Graphoderus bilineatus met betrekking
tot electrisch geleidingsvermogen.
- GRAPHODERUS BILINEATUS
According to Holmen () and Hendrich &
Balke () the species tolerates weakly acid
water, circumstances which are encountered in
the Netherlands only in the Voorste Goorven
with a pH between . and . at different
stations and times.
Figure . Percentual distribution of sampling localities
with or without Graphoderus bilineatus in relation to
hardness.
Figuur . Procentuele verdeling van monsterpunten
met en zonder Graphoderus bilineatus met betrekking
tot hardheid.
compounds. Most localities were situated in the
large seepage areas of the Netherlands, but this
was hardly visible in the field (no milky or rusty
water, no bacterial films at the water surface,
indicative plants species e.g. Hottonia palustris
were not common).
Graphoderus bilineatus is an inhabitant of
unshaded waters, which means that usually no
trees or shrubs are growing on the banks. At some
localities mowing activities were hindered by trees
(most often at dead-ends of ditches), resulting
in accumulation of trembling bog or a richer
emergent vegetation, resulting in a better hidingplace for the beetles. Close to the banks the
shading can increase considerably in the course
of the season, due to the growth of helophytes
on the banks. This of course also depends on the
slope and exposition of the bank.
Graphoderus bilineatus is most often observed
in waters with a pH between and . (fig. ),
which seems to be the normal range abroad.
Electrical conductivity and chlorinity are strongly
correlated in our dataset and therefore only the
results for conductivity are presented (fig. ).
Graphoderus bilineatus is observed in all classes
except the highest (> mS/m). A ‘preference’ for the lower three classes (< mS/m)
is obvious, above this value the presence of
G. bilineatus rapidly declines.
The hardness (ºD), a measure for the total
amount of calcium and magnesium, shows that
G. bilineatus is observed more in the lower three
classes (< ºD)(fig. ) than in the higher three.
The structure, and to a lesser degree the composition, of the vegetation on the sampling localities
is quite variable over the sample sites and also the
season. In springtime (April-May) the water
vegetation is usually sparsely developed and
will be better developed in summer (AugustSeptember), when not cut. The emergent
vegetation (only as far as it stands in the water)
is sparsely developed with a cover of less than %
by Phragmites australis, Carex paniculata, C. acuta,
C. acutiformis and Thelypterus palustris as frequent
and sometimes dominant species. Also the floating leaved vegetation (rooted as well as unrooted)
is most often scarce, but occasionally Nuphar
lutea, Nymphaea alba or Hydrocharis morsus-ranae
are dominating. Potamogeton species are rare.
Surface floating lemnids, though very frequent, are
never dominant on localities with G. bilineatus.
The submerged vegetation is well developed
and often rather rich in species. Dominant and
frequent is Utricularia vulgaris, less often Elodea
canadensis, E. nuttallii, Ceratophyllum demersum,
Potamogeton species, Stratiotes aloides, Hottonia
palustris and Lemna trisulca. Mosses (mostly
Sphagnum) and a floating layer of algae (flab)
are sporadically present.
‒
Figure . Predictive distribution model for Graphoderus bilineatus. In kilometre squares in peat bog areas (red),
the probability of its occurrence is more than % based on electrical conductivity and associative plant species, in
green squares the prediction is based only on electrical conductivity.
Figuur . Voorspellend verspreidingsmodel voor Graphoderus bilineatus. In de rode kilometerhokken in de laagveengebieden is de kans op aantreffen van deze soort meer dan % gebaseerd op electrisch geleidingsvermogen en
geässocieerde plantensoorten, in de groene hokken is deze voorspelling alleen gebaseerd op electrisch geleidingsvermogen.
- GRAPHODERUS BILINEATUS
Potential distribution model
The development of the potential distributional model is reported in Sierdsema & Cuppen
(). The final result is a map (fig. ) that can
be used for future investigations. The map shows,
for peat bog areas only, the kilometre squares (in
red) in which G. bilineatus can be expected with
a probability of more than %. This expectation
is based on electrical conductivity of the water
and the presence of associative plant species. In
the green kilometre squares a probability of more
than % for G. bilineatus is computed on the
basis of electrical conductivity only. For these
squares no floristical data were available. Green
squares are mainly found in the northern part
of the country.
In the first half of the th century G. bilineatus
occurred in large parts of the Netherlands, lacking
only in brackish areas. In the second half of the
th century the species declined severely in all
regions of our country except for peat bogs. The
reasons for this decline surely include acidification of moorland pools by wet and dry acidic
deposition, eutrophication by intensification of
agriculture (use of artificial fertilizers), intensified
use of herbicides and pesticides, re-allotment
and intake of nearly brackish and hard river
water (Rhine). Survival of G. bilineatus in peat
bog areas is probably due to seepage, resulting in a good water quality (poor in nutrients,
relatively low conductivity and total hardness).
Also the relatively low economic value of these
areas for agriculture reduced some of the above
mentioned human influences. The peat bog areas,
functioning as nature reserves, recreation areas
or sources of natural products (fish, reeds) have
changed relatively little during the last century.
The improvement of water management in some
of the areas (stopping, reducing and/or dephosphatizing of river water taken in) probably has
resulted in (re)colonization of the Naardermeer,
Weerribben, Wieden and Nieuwkoopse Plassen
by G. bilineatus in the last decade of the th
century. Most of these areas were not very well
investigated for invertebrates in the past but at
least for the Naardermeer the restoration is well
documented. Eight sites were sampled more or
less regularly for invertebrates from onwards.
Dephosphatizing of intake water from the
IJmeer took place from onwards but, after
problems in the initial stage, was effective from
onwards (Boosten ). Graphoderus
bilineatus was first recorded in at one site,
followed by a second and third site in
(pers. com. G. van Ee). Prior to the discovery of
Graphoderus, the water turbidity strongly declined
resulting in clear water that enabled the development of a closed submerged vegetation including
stoneworts (Characeae) and Najas marina.
The distribution model predicts for the peat bog
regions in the Netherlands the occurrence of
G. bilineatus in x kilometre squares with a
probability of more than % (fig. ). A research
project directed on especially these grid squares
can improve the known distribution of the species
in the Netherlands most succesfully. The predictive model can be validated by use of consistent
sampling techniques and fixed time schedules.
For the validation the assessment of the model
parameters (electrical conductivity, number of
associative aquatic plant species) is necessary.
Many grid squares in the northern peat bog areas
are deficit in floristical data. It is advised to gather
these floristical data first and to add them to the
model. Hereafter, examination of the grid squares
with the highest potentials for G. bilineatus can
be conducted.
The predictive distribution model is based on
measurements, maps and expert judgement. A
major restriction of the model is its limitation
to peat bog soils. To find new localities with
G. bilineatus outside this area one can rely only
on expert judgement. It is recommended to
include in a new research project at least some
heath land ponds in areas inhabited by the species
in former days. Heath land ponds with an unaltered water table, not acidified nor eutrophicated,
seem to be the best ones to look for.
‒
We like to thank everyone (Natuurmonumenten,
State Forestry Service, Water Authority Boards)
who made it possible to investigate the status
of Graphoderus bilineatus in the Netherlands by
giving us permits for collecting and access, boats,
petrol, and information on localities. Gert van Ee
provided information on several localities in the
province of Noord-Holland. We thank Theodoor
Heijerman for the nice photo. Menno Reemer
and Vincent Kalkman (-Nederland) were
very helpful with providing us with permits, and
editing, arrangement and adding of text and illustrations to parts of manuscripts.
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(Coleoptera). – Nederlandse Faunistische
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Koese, B. & J.G.M. Cuppen . Sampling methods
for Graphoderus bilineatus (Coleoptera: Dytiscidae).
– Nederlandse Faunistische Mededelingen : -.
Nieukerken, E.J. van . Dytiscidae (waterroofkevers). – In M.B.P. Drost, H.P.J.J. Cuppen,
E.J. van Nieukerken & M. Schreijer (red.), De
waterkevers van Nederland (Coleoptera).
Uitgeverij, Utrecht: -.
Nilsson, A.N. & M. Holmen . The aquatic
Adephaga (Coleoptera) of Fennoscandia and
Denmark. . Dytiscidae. – Fauna Entomologica
Scandinavica : -.
- GRAPHODERUS BILINEATUS
Olsvik, H. . Graphoderus bilineatus (DeGeer,
) (Col., Dytiscidae), new to Norway. – Fauna
Norvegica, Series B : .
Queney, P. . Liste taxonomique des Coléoptères
‘aquatique’ de la faune de France. – Le
Coléoptériste () supplément: -.
Ribera, I, . Fauna Ibérica, el reino animal en la
península Ibérica y las islas Baleares.
– www.fauna-iberica.mncn.csic.es [bekeken op
.iv.]
Schaeflein, H. . Familie: Dytiscidae, echte
Schwimmkäfer. – Die Käfer Mitteleuropas : -.
Sierdsema, H. & J.G.M. Cuppen . A predictive distribution model for Graphoderus bilineatus
in the Netherlands (Coleoptera: Dytiscidae). –
Nederlandse Faunistische Mededelingen : -.
Verspreiding en biotopen van Graphoderus bilineatus (Coleoptera: Dytiscidae)
De verspreiding en biotopen van de gestreepte waterroofkever Graphoderus bilineatus zijn in
en onderzocht in opdracht van de provincie Zuid-Holland en het Ministerie van . Deze
waterroofkever is wettelijk beschermd middels de Flora- en Faunawet en de Habitatrichtlijn.
Graphoderus bilineatus kwam vroeger in grote delen van Nederland voor, maar is tegenwoordig
vrijwel beperkt tot de grote laagveengebieden in de provincies Friesland, Overijssel, Utrecht en
Noord- en Zuid-Holland. De belangrijkste biotopen in Nederland zijn sloten en kanalen met een
breedte tussen , en meter, een diepte tussen en centimeter met helder water, en meestal
een vrij spaarzame vegetatie van drijvende en submerse waterplanten. Uit het buitenland is
G. bilineatus vooral bekend uit grotere wateren. Op basis van een verspreidingsmodel wordt voor
de laagveengebieden van ons land het potentiële voorkomen van G. bilineatus voorspeld. In
kilometerhokken voorspelt het model de aanwezigheid van deze soort met een waarschijnlijkheid
van meer dan %.
J.G.M. Cuppen
Aquatic Ecology and Water Quality Management Group
Wageningen University and Research Centre
Ritzema Bosweg a
Wageningen
jan.cuppen@wur.nl
B. Koese
-Nederland
Postbus
Leiden
eis@naturalis.nl
H. Sierdsema
Dutch Centre for Field Ornithology /
-University of Amsterdam /
Alterra-Wageningen University and Research Centre
Rijksstraatweg
Beek-Ubbergen
henk.sierdsema@sovon.nl
‒
Henk Sierdsema