Multi-annual cycles in population of Ischnura e. elegans induced by crowding and mediated by sexual aggression (Odonata: Coenagrionidae)


Hinnekint, B.O.N.; Dumont, H.J.

Entomologia Generalis 14(3-4): 161-166

1989


A re-analysis of published female mating frequencies in mature and immature Ischnura e. elegans (Vander Linden 1820) shows that male sexual aggression varies with crowding, young mature .male..male. driving away immature and old .male..male., and .female..female. from the edges of ponds. This effect is more pronounced in .female..female., heteromorphs and immatures, and generates a male-biased sexually active population near the water, where newly matured .male..male. form the dominant fraction. - It is hypothesised that density dependant male aggression is one of the driving forces beyond the existing hyperfine effect causing a pluriannual population cycle. Below a certain population density threshold, there is a constant minimum "basic" sexual aggression. Above the threshold, the sexual harassment that causes the fall of overall mating frequency causes a steep increase of the frequency of matings involving immature .female..female.. At peak population density general aggression disappears, and sexual aggression drops back to its base level.

Entomol.
Gener.
14
(3/4):
161-166
Stuttgart
1989-07
ISSN:
0171-8177
EGT-Nr
613
I
Multi-Annual
Cycles
in
Populations
of
Ischnura
e.
elegans
Induced
by
Crowding
and
Mediated
by
Sexual
Aggression
(Odonata:
Coenagrionidae)*
Benno
0.
N.
Hinnekint
&
Henri
J.
Dumont
Received:
1988-02-16/1988-12-13
Accepted:
1988-12-16
Hinnekint,
B.
O.N.
[Merestraat
32,
B-9430
Aalst],
&
Dumont,
H.
J.
[Lab.
Ecol.,
Univ.,
B-9000
Gent]:
Multi-Annual
Cycles
in
Populations
of
Ischnura
e.
elegans
Induced
by
Crowding
and
Mediated
by
Sexual
Aggression
(Odonata:
Coenagrionidae).
Entomol.
Gener.
14
(3/4):
161-166;
Stuttgart
1989.
[Article].
A
re-analysis
of
published
female
mating
frequencies
in
mature
and
immature
Ischnura
e.
elegans
(Vander
Linden
1820)
shows
that
male
sexual
aggression
varies
with
crowding,
young
mature
cfcf
driving
away
immature
and
old
cfcf,
and
99
from
the
edges
of
ponds.
This
effect
is
more
pronounced
in
99,
heteromorphs
and
immatures,
and
generates
a
male-biased
sexually
active
population
near
the
water,
where
newly
matured
cfcf
form
the
dominant
fraction.
It
is
hypothesised
that
density
dependant
male
aggression
is
one
of
the
driving
forces
beyond
the
existing
hyperfine
effect
causing
a
pluriannual
popula-
tion
cycle.
Below
a
certain
population
density
threshold,
there
is
a
constant
minimum
"basic"
sexual
aggression.
Above
the
threshold,
the
sexual
harassment
that
causes
the
fall
of
overall
mating
frequency
causes
a
steep
increase
of
the
frequency
of
matings
involving
immature
99.
At
peak
population
density
general
aggression
disappears,
and
sexual
aggression
drops
back
to
its
base
level.
Key
word
s:
Distribution
pattern
Odonata
sexual
aggressivity
population
density
multiannual
population
cycle.
1
Introduction
Hinnekint
[1987]
discussed
the
occurrence
of
uneven
distributions
of
the
two
sexes,
of
different
age
groups,
and
even
of
different
female
morphs
in
populations
of
adult
Ischnura
e.
elegans
(Vander
Linden
1820).
Each
age
group
in
this
damselfly
species
can
be
readily
identified
in
the
field
by
its
particular
body
colour
pattern,
which
is
superimposed
on
a
sex-linked
polychromism.
Hinnekint
showed
that
the
sexual-
ly
active
part
of
a
population
resides
at
mating
and
ovipositing
sites
near
the
water,
and
that
its
largest
fraction
is
composed
of
newly
matured
cfcf,
while
all
other
age
groups
of
both
sexes
tend
to
get
excluded
from
near-water
areas,
and
disperse
in
a
"hinterland",
away
from
their
native
ponds.
Importantly,
it
was
found
that
the
fraction
of
immature
and
old
specimens
residing
at
the
water
varies
over
a
6-year
cycle
of
population
density,
such
that
their
relative
numbers
decrease
with
rising
population
densities
and
crowding.
It
was
further
shown
that
overall
female
attendance
at
the
water
is
more
strongly
affected
by
crowding
than
is
male
attendance,
resulting
in
a
male-biased
sex
ratio
at
the
water,
even
at
modest
levels
of
crowding.
Apparent
sex
ratio
at
the
water
(expressed
as
male
population
fraction)
was
linearly
related
to
population
density
and
could
reach
values
as
high
as
0.75
(Tab
1).
*
A
new
hypothesis
explaining
population
regulation.
11
0171-8177/89/0014-0161
$
1.50
©
1989
E.
Schweizerbart'sche
Verlagsbuchhandlung,
D-7000
Stuttgart
1
162
B.
O.
N.
Hinnekint
&
H.
J.
Dumont
Hinnekint
[1987]
hypothesised
that
the
progressive
drop
in
number
of
99
at
the
mating
sites
ultimately
reduces
successful
reproduction
to
a
level
where
a
temporary
collapse
of
the
population
occurs,
thus
terminating
the
population
cycle.
One
of
the
obvious
proximate
fac-
tors
responsible
for
expelling
99
from
a
mating
site,
is
the
aggressive
behaviour
of
the
CfCf
towards
any
other
specimen
of
their
own
species
encountered.
Such
aggressiveness
is,
however,
at
least
in
part,
sexual
in
origin.
In
Odonata,
this
has
been
stressed
in
qualitative
terms
by
numerous
authors
[Corbet
1957,
Kormondy
1959,
Moore
1952, 1962,
Pajunen
1962
a,
1962
b,
1963,
1964,
Ris
1910].
In
L
aurora
(Brauer
1865),
a
tropical
relative
of
L
elegans,
sexual,
non-selective
aggression
against
99,
cfcf
,
and
even
specimens
of
other
species
was
reported
in
detail
by
Rowe
[1978].
It
is
here
hypothesised
that
sexual
aggression
is
indeed
an
important
regulator
of
the
6-year
cycle
mentioned
above
and
a
major
distributive
parameter
of
the
population.
However,
in
order
to
devise
a
reasonable
first-order
test
for
it,
a
quantitative
measure
of
sexual
aggression
is
needed.
It
can
be
defined
as
the
number
of
matings,
observed
in
field
populations,
that
in-
volve
immature
99.
Such
matings
were
known
to
exist
from
studies
of
Lord
[1961],
Parr
&
Palmer
[1971],
Buchholtz
[1951],
and
Zahner
[1960].
As
immature
99
are
considered
those
who
have
not
yet
developed
sexual
behaviour
(easy
recognisable
by
their
colour
form
[Hin-
nekint
1987],
and
all
cfcf
attempting
to
mate
with
such
99
by
engaging
them
in
a
tandem
formation
are
considered
to
display
non-selective
sexual
aggressiveness.
2
Methods
and
Data
The
reasonings
are
based
on
a
re-interpretation
of
published
information.
Usable
published
data
of
the
kind
needed
for
this
purpose
are
not
abundant,
and
in
fact
only
just
sufficient
for
the
testing
of
our
hypothesis.
Statistical
tests
are
not
possible
due
to
lack
of
replication,
yet
the
concept
itself
is
believed
to
have
much
intrinsic
value
and
may
stimulate
further
research.
All
published
material
relates
to
a
number
of
British
populations,
studied
by
Parr
&
Palmer
[1971],
Parr
[1973]
(the
Dunham
Ponds
I,
II
and
III),
and
Lord
[1961]
(the
Anglesey
population).
From
this
raw
material,
a
number
of
relevant
data
were
selected
or
recalculated
by
Hinnekint
[1987]
and
shown
in
Tab
1.
All
this
information
is
based
on
capture-recapture
data.
By
sex
ratio
is
meant
the
apparent
(=
observable)
sex
ratio
seen
at
the
water,
based
on
the
number
of
captures
and
recaptures.
It
is
expressed
as
the
male
fraction
of
the
population
found
at
the
mating
sites.
The
number
of
99
in
column
2
is
also
derived
from
capture
data
but
includes
only
mature
99
(other
comparable
figures
were
not
available).
The
mating
fre-
quency
(column
4)
is
calculated
as
the
total
number
of
mating
pairs
observed
versus
the
total
number
of
mature
99
captured,
and
expressed
as
a
%.
In
Hinnekint
[1987]
the
Anglesey
mating
frequency
was
defined
as
the
number
of
matings
per
number
of
female
individuals,
resulting
in
a
rather
high
figure
when
compared
to
the
mating
frequencies
based
on
captures
(including
recaptures).
To
optimise
comparability,
matings
observed
by
Lord
[1961]
are
now
considered
per
total
female
captures
minus
the
number
of
immature
female
individuals.
The
number
of
immature
99
engaged
in
copula
or
tandem
linkage
(column
5)
is
obtained
by
direct
observations
and
expressed
as
a
%
(column
6)
of
the
total
number
of
matings
observed,
and
not
versus
the
total
number
of
99
to
avoid
all
topographical
influences
of
the
different
biotopes.
It
is
believed
that
any
effect
of
the
closed
or
open
nature
of
the
biotopes
on
the
free
exchange
between
the
sexually
active
population
and
the
"hinterland"
biases
overall
matings
and
matings
involving
immature
99
in
the
same
way.
Therefore
the
%
of
immature
matings
versus
overall
matings
is
thought
to
be
independent
of
biotope
characteristics.
Multiannual
Cycles
in
Ischnura
Populations
163
3
Results
The
%
of
immature
matings
(ordinate)
is
plotted
against
sex
ratio
(abscissa)
as
an
indicator
of
population
density,
in
Fig
1.
Although
different
populations
are
considered,
data
are
represented
in
one
single
Fig
and
Tab
to
detect
if
these
data
could
possibly
match
the
multian-
nual
cycle
found
by
Hinnekint
[1987].
The
position
within
the
hypothesised
6-year
cycle
of
each
population
and
year
is
also
indicated.
%
Immature
mating'
25
20
15
10
.4
0
0.5
OE
07
ds
1.0
s.
II
I
III
Ponds
Ratio
1959
1956
1955
1970
1965
1970
Years
2
4
5
6
Phases
of
population
cycle
Fig
1:
%
of
matings
involving
immature
99
of
Ischnura
degans
(Vander
Linden
1820)
versus
sex
ratio
(expressed
as
male
fraction).
(Curve
fitted
by
eye,
basic
level
computed.)
The
population
cycle
phases
are
based
on
Hinnekint
[1987].
Note
that
there
is
a
phase
difference
between
the
population
cycles
of
adjacent
populations,
illustrating
that
the
cycle
is
not
due
to
a
T
effect.
At
low
population
densities,
i
e
at
a
sex
ratio
of
0.50-0.62,
there
is
an
interval
where
imma-
ture
matings
are
at
a
low
but
constant
level
of
slightly
over
5
%,
henceforth
called
the
base
level.
At
densities
above
0.62,
the
number
of
matings
involving
immature
99
sharply
increases.
It
reaches
a
maximum
at
a
sex
ratio
of
0.70,
but
abruptly
falls
back
to
the
base
level
as
sex
ratio
increases
even
further
(Fig
1).
4
Discussion
It
might
be
pointed
out
that
Fig
1
is
based
on
6
data
points
only.
Despite
this,
each
dot
is
based
on
all
observed
matings
during
a
complete
flight
season
in
the
case
of
the
Dunham
Ponds
in
1965
and
1966,
and
during
a
month
in
all
other
cases.
They
may
therefore
be
con-
sidered
sufficiently
reliable
to
be
used
in
an
analysis
like
the
present
one.
Observable
copula-
164
B.
0.
N.
Hinnekint
&
H.
J.
Dumont
tions
in
I.
elegans
are
not
numerous
[Parr
&
Palmer
1971].
As
there
are
relatively
fewer
im-
mature
99
at
the
mating
spot,
matings
involving
immature
99
are
even
scarcer.
This
explains
the
low
number
of
matings
entered
in
Tab
1.
Tab
1:
Ischnura
elegans
(Vander
Linden
1820)
99,
observed matings
and
mating
frequencies
of
99
based
on
data
of
Parr
&
Palmer
[1971]
for
the
Dunham
ponds
and
of
Lord
[1961]
for
the
Aglesey
biotope,
and
recalculated
by
Hinnekint
[1987].
Apparent
sex
Total
Total
Female
Number
of
%
immature
Standard
Populations
ratio
(male
number
number
of
mating
immature
matings
error
on
fraction)
at
of
mature
matings
frequency
gg
versus
total
%
the
water
n
observed
in
%
mating
matings
0.545
627
52
8.3
3
6
3
Anglesey
1959
0.583
228
19
8.3
1
5
5
Dunham
III
1966
0.623
366
47
12.8
2
4
3
Dunham
II
1965
0.676
284
50
17.6
7
14
5
Dunham
I
1970
0.699
170
21
12.4
6
29
10
Dunham
I
1965
0.748
70
14
*
20.0
*
1
*
7 7
Dunham
III
1970
122
7
6
2
Mean
base
level
*
Abberantly
high
figures
caused
by
the
closed
nature
of
the
biotope
as
explained
by
Hinnekint
[1987].
"*
Based
on
the
following
populations:
Anglesey
1959,
Dunham
III
1966
and
1970,
and
Dunham
II
1965.
Where
one
might
expect
that
a
theoretical
sex
ratio
of
0.5,
in
complete
absence
of
crowding,
there
would
be
no
mating
with
immature
99,
it
turns
out
that
in
fact
a
small
number
(ca
5
%)
of
immatures
always takes
part
in
mating.
This
basic
immature
mating
frequency
was
record-
ed
in
the
Anglesey
population
in
1959,
and
at
the
Dunham
Ponds
II
and
III
in
1965
and
1966
respectively.
At
the
theoretical
upper
level
of
crowding,
represented
by
a
sex
ratio
of
1,
there
can
of
course
be
no
mating
with
immature
or
even
mature
99,
because
none
are
left
in
the
active
popula-
tion.
This
limit
is,
however,
academic
in
nature,
since
no
population
was
ever
observed
reaching
such
huge
densities.
The
populations'
autoregulation,
as
described
in
this
paper,
will
limit
the
density
before
this
upper
sex
ratio
is
reached.
At
the
highest
observed
population
density
(at
a
sex
ratio
of
0.75),
immature
mating
frequency,
conversely,
only
drops
back
to
its
base
level
(Fig
1)
as
observed
at
the
Dunham
Pond
III
in
1970.In
Tab
1
and
Fig
1,
the
data
are
classified
by
increasing
population
density,
such
as
to
fit
the
six
year
population
cycle
iden-
tified
by
Hinnekint
[1987].
This
cycle
is
again
shown
to
exist
at
the
2
Dunham
ponds,
for
which
data
of
2
non-consecutive
years
are
available.
Counting
the
years
between
the
available
data
for
one
single
population
shows,
in
both
cases,
a
cycle
with
the
same
length,
but
with
a
phase
lag.
It
is
noteworthy
that
the
maximum
%
of
matings
involving
immature
99
is
observed
one
year
of
ter
the
maximum
in
overall
mating
frequencies
(Tab
1),
and
one
year
before
the
peak
population
density
is
reached,
and
that
matings
involving
female
im-
matures
vary
only
over
a
narrow
range
of
population
densities.
The
sexual
harassment
by
solitary
cfcr
,
rendering
the
act
of
mating
increasingly
difficult,
causes
the
crash
of
overall
mating
frequency
at
high
population
density
and
causes
simultaneously
the
increase
of
matings
involving
immature
99.
At
extreme
crowding
level
Multiannual
Cycles
in
Ischnura
Populations
165
general
aggression
ceases
[Pajunen
1962
a,
Buchholtz
1951,
Zahner
1960,
Crumpton
1975,
Klotzli
1971]
and
thus
non-selective
sexual
aggression
disappears,
and
therefore
the
matings
involving
immature
99
fall
back
to
the
base
level.
It
follows
that
the
crash
in
overall
mating
frequency
has
to
be
ascribed
to
mature
specimens
(of
both
sexes).
These
effects
could
be
stronger
in
I.
elegans
than
in
other
Odonata,
due
to
its
extreme
long
copulation
time
[Krieger
&
Krieger-Loibl
1958].
Female
mating
frequency
is
more
influenced
by
crowding
than
male
mating
frequency.
The
%
of
matings
involving
immature
99
is
even
more
influenced
as
this
population
fraction
is
composed
of
specimens
not
yet
showing
sexual
behaviour.
They
react
to
sexual
aggression
and
the
mating
attempts
by
mature
cid
by
emigrating
from
the
mating
sites.
The
non-selectivity
of
sexual
behaviour,
especially
the
intraspecific
mating
attempts
with
other
cfc
f
,
and
99
of
all
age
groups,
is
probably
caused
by
a
relatively
faulty
mate
recognition
ability
in
Odonata,
first
suggested
by
Corbet
[1962].
A
certain
degree
of
incorrect
mate
recognition
in
I.
elegans
could
perhaps
provide
an
explanation
for
the
maintenance
of
female
polymorphism,
which
has
been
shown
to
be
an
adaptation
to
different
levels
of
population
density
itself
[Hinnekint
1987].
For
example,
andromorphic
99
are
favoured
in
dense
popula-
tions,
escaping
the
attention
of
cid
in
such
a
way that
they
can
maintain
themselves
in
the
sexually
active
population
near
the
water,
but
are
disadvantaged
in
sparse
ones
as
they
are
less
attractive
to
cfc
f
.
This
illustrates
that
diversity
in
morphs
can
be
a
factor
of
population
stability,
as
diversity
in
species
is
[McNaughton
1988].
The
described
intraspecific
interaction
can
be
classified
as
a
h
y
p
e
r
f
in
e
effect,
which
can
provoke autoregulation
within
a
population,
as
suggested
by
Hinnekint
[1987],
as
long
as
strong
disturbances,
such
as
drought
or
extreme
temperatures,
do
not
override
it.
Cyclic
phenomena
in
populations
have
been
shown
to
be
due
to
social
behaviour
in
mammals
[Cockburn
1988].
This
conclusion
can
now
be
extended
to
insect
populations.
5
Acknowledgements
The
manuscript
was
read
by
Dr
K.
Martens
and
Mr
K.
Roche.
Mrs
D.
Hinnekint-De
Kuyper
drew
the
figure.
6
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Authors'
addresses
Anschriften
der
Verfassers:
Dr
Benno
O.N.
Hinnekint
(To
whom
requests
for
reprints
should
be
sent),
Merestraat
32,
B-9430
Aalst
(Nieuwerkerken);
Belgie.
--
Professor
Dr
Henri
J.
Dumont,
Laboratorium
voor
Ecologie
der
Dieren,
Zoogeografie
en
Natuurbehoud,
Rijksuniversiteit
Gent,
K.
L.
Ledeganckstraat
35,
B-9000
Gent;
Belgie
Belgium.
Taylor,
R.
J.:
Predation.
In:
Usher,
M.B.,
&
Rosenzweig,
M.L.
(Editors):
Population
and
Community
Biology.
[VIII
+
166
pages,
numerous
figures
and
tables,
size
153
x
232
mm,
soft
cover].
Publisher:
Chapman
&
Hall,
London-New
York;
ISBN:
0-412-26120-0.
---
[EGR-Nr
1172].
This
volume
describes
essential
features
of
predation
and
its
consequences
for
population
dynamics.
It
integrates
mathematical
predation
theory,
results
of
laboratory
experiments
with
model
systems
and
field
studies
on
predator-prey
systems.
Topics
discussed
by
the
author
include
the
self-limitation
of
prey
and
predator
populations,
the
role
of
age
and
size
structure
in
predator
and
prey
populations,
prey
refugia,
various
aspects
of
the
functional
response
of
predators,
and
the
influence
of
spatial
structure
in
prey
populations.
The
concluding
chapters
deal
with
the
impact
of
predation
on
population
cycles
and
the
evolution
of
predator
prey
systems.
The
majority
of
examples
refer
to
systems
with
vertebrate
predators
such
as
the
famous
lynx-hare
cycle
in
Canada.
Data
obtained
by
biological
control
operations
and
laboratory
studies
with
host-parasitoid
models
are
used
to
examine
predictions
derived
from
mathematical
treatments
of
predation
theory.
The
book
provides
the
reader
with
a
well
balanced
extract
of
information
carefully
selected
from
an
ample,
diverse
and
sometimes
inaccessible
literature.
It
can
be
recommended
for
students
and
researchers
who
are
interested
in
basic
and
applied
ecology.
Helmut
Zwolfer
(Bayreuth)