F1000Resea ch
Open Pee Re iew
, Uni ed S a es Depa men Pa ick Tobin
o Ag icul u e USA
, Uni e si y o o B i ishJudi h Mye s
Columbia Canada
Discuss his a icle
(0)Commen s
2
1
RESEARCH ARTICLE
Gene ic and en i onmen al de e minan s o insec he bi o e
communi y s uc u e in a popula ionBe ula pendula [ e sion 1;
e e ees: 2 app o ed]
Ta ja Sil e , Ma i Rousi , Elina Oksanen , Heikki Roininen1
Facul y o Science and Fo es y, Depa men o Biology, Uni e si y o Eas e n Finland, FIN-80101 Joensuu, Finland
Van aa Resea ch Uni , Finnish Fo es Resea ch Ins i u e, FIN-01301 Van aa, Finland
Abs ac
A numbe o ecen s udies ha e shown ha in aspeci ic gene ic a ia ion o
plan s may ha e a p o ound e ec on he he bi o ous communi ies which
depend on hem. Howe e less is known abou he ela i e impo ance o
in aspeci ic a ia ion compa ed o o he ecological ac o s, o example
en i onmen al a ia ion o he e ec s o he bi o e damage. We andomly
selec ed 22 geno ypes om a local popula ion (< 0.9 ha),Be ula pendula
cloned hem and plan ed cloned seedlings on wo s udy si es sepa a ed a a
egional scale (dis ance be ween si es abou 30 km) o examine an insec
communi y o 23-27 species on hese geno ypes. geno ypes did no B. pendula
di e in hei species ichness, bu he o al mean abundance and he s uc u e
o he insec he bi o e communi y was signi ican ly a ec ed by he geno ype,
which could accoun o up o 27% o he o al a ia ion in communi y s uc u e.
geno ype accoun ed o wo o ou imes mo e a ia ion in heB. pendula
a h opod communi y s uc u e han did en i onmen al (block) a ia ion on a
local scale, while on a egional scale, geno ypic and en i onmen al (si e)
a ia ion accoun ed o 4-14% o he a h opod communi y s uc u e. The
gene ic e ec s we e modi ied by en i onmen al a ia ion on bo h a local and
egional scale o e one s udy yea , and locally, he la ges pa o he a ia ion
(38%) could be explained by he geno ype × en i onmen (block) in e ac ions.
Supp ession o insec he bi o es du ing one g owing season led o changed
a h opod communi y s uc u e in he ollowing g owing season, bu his e ec
was minimal and could explain only 4% o he o al a ia ion in insec
communi y s uc u e. Ou esul s sugges ha bo h gene ic and en i onmen al
ac o s a e impo an de e minan s o he communi y s uc u e o he bi o ous
insec s. Toge he hese mechanisms appea o main ain he high di e si y o
insec s in o es ecosys ems.B. pendula
1 2 1 1
1
2
Re e ee S a us:
In i ed Re e ees
e sion 1
published
31 Jan 2014
1 2
epo epo
31 Jan 2014, :34 (doi: )Fi s published: 3 10.12688/ 1000 esea ch.3-34. 1
31 Jan 2014, :34 (doi: )La es published: 3 10.12688/ 1000 esea ch.3-34. 1
1
Page 1 o 15
F1000Resea ch 2014, 3:34 Las upda ed: 09 SEP 2015
F1000Resea ch
Ta ja Sil e ( )Co esponding au ho : [email p o ec ed]
Sil e T, Rousi M, Oksanen E and Roininen H. How o ci e his a icle: Gene ic and en i onmen al de e minan s o insec he bi o e
2014, :34 (doi: communi y s uc u e in a popula ion [ e sion 1; e e ees: 2 app o ed]Be ula pendula F1000Resea ch 3
)10.12688/ 1000 esea ch.3-34. 1
© 2014 Sil e T . This is an open access a icle dis ibu ed unde he e ms o he , whichCopy igh : e al C ea i e Commons A ibu ion Licence
pe mi s un es ic ed use, dis ibu ion, and ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed. The au ho (s) is/a e employees
o he US Go e nmen and he e o e domes ic copy igh p o ec ion in USA does no apply o his wo k. The wo k may be p o ec ed unde he
copy igh laws o o he ju isdic ions when used in hose ju isdic ions. Da a associa ed wi h he a icle a e a ailable unde he e ms o he C ea i e
(CC0 1.0 Public domain dedica ion).Commons Ze o "No igh s ese ed" da a wai e
This s udy was unded by he Academy o Finland (p ojec 78743, g an ed o EO), and unding g an ed o TS by he G adua eG an in o ma ion:
School in Fo es Sciences, Finnish Conco dia Fund and Kone Founda ion (g an 2-712) is also acknowledged.
The unde s had no ole in s udy design, da a collec ion and analysis, decision o publish, o p epa a ion o he manusc ip .
Compe ing in e es s: No compe ing in e es s we e disclosed.
31 Jan 2014, :34 (doi: ) Fi s published: 3 10.12688/ 1000 esea ch.3-34. 1
Page 2 o 15
F1000Resea ch 2014, 3:34 Las upda ed: 09 SEP 2015
In oduc ion
Gene ic a ia ion wi hin one species can a ec he s uc u e and
dynamics o associa ed communi ies and en i e ecosys ems1,2. This
may be conside able, especially o keys one species, such as o es
ees, which se e as ood and habi a o nume ous p ima y con-
sume s. A as numbe o s udies ha e al eady shown ha a h o-
pod communi ies espond o gene ic di e ences among indi idual
plan s wi hin in e speci ic hyb idizing complexes (e.g. Eucalyp us3,
Salix4, Populus5, Que cus6) o speci ic geno ypes wi hin species
(e.g. Oeno he a biennis7, Eucalyp us globulus8, Solidago al issima9,
Populus angus i olia10). Howe e , i has ecen ly been a gued ha
he ole o plan gene ic a ia ion in s uc u ing a h opod com-
muni ies has been conside ably in la ed due o he common me h-
odological law ha geno ypes a e collec ed om di e se and o en
dis an en i onmen s, which maximizes gene ic a ia ion, whils
expe imen s a e pe o med in a single common ga den whe e en i-
onmen al a ia ion is minimized11,12. Indeed, when his misma ch
in scale was a oided in he expe imen al design, spa ial p ocesses
elega ed hos plan geno ype o a seconda y ole in s uc u ing
insec communi ies o Que cus obu L.13. Whe he his applies o
all sys ems is, howe e , no ye known.
Genes encoun e a ange o en i onmen s in na u e and i has long
been ecognized ha gene ic de e mina ion o plan suscep ibili y o
a he bi o ous insec depends on en i onmen al con ex 14. Howe e ,
mos s udies ha ha e examined he ole o geno ype × en i on-
men in e ac ions in he abundance and dis ibu ion o he bi o ous
species, ha e used only one o a ew closely ela ed he bi o e spe-
cies (e.g.15–18), and much ewe s udies ha e examined geno ype ×
en i onmen in e ac ions in a communi y con ex 7,13,19,20. I is well
ecognized ha we know oo li le o he ela i e impo ance o
in aspeci ic gene ic a ia ion compa ed o o he ecological ac o s
ha also in luence mul i- ophic communi ies and ecosys em
p ocesses11. Thus, he examina ion o geno ype × en i onmen in e -
ac ions in a communi y con ex may be essen ial o imp o ing ou
knowledge in he de eloping ield o communi y gene ics.
Sil e bi ch (Be ula pendula Ro h) is an ideal ee species in which
o examine he mechanisms o plan -he bi o e in e ac ions and he
communi y-le el consequences o ai a ia ion, because he species
shows ema kable gene ic a ia ion in i s esis ance o he bi o es21–24.
In addi ion, he gene ic a ia ion o seconda y me aboli es26, nu i-
en concen a ions27, and phenological ai s28,29 o B. pendula a e
known o be subs an ial, and all hese ai s a e known o a ec
he bi o es and highe ophic le el in e ac ions2,30,31. Mos o he
s udies ha ha e been conduc ed using B. pendula ha e used
geno ypes ha we e o iginally andomly selec ed om a local
B. pendula popula ion, i.e. om a na u ally egene a ed o es s and
< 0.9 ha. None o hese ea lie s udies ha e, howe e , in es iga ed
he wi hin-popula ion geno ypic a ia ion in B. pendula insec he -
bi o e species ichness and communi y composi ion. We cloned
22 B. pendula geno ypes, plan ed hem in wo common ga dens sep-
a a ed a a egional scale (dis ance be ween si es abou 30 km), and
s udied he ela i e impo ance o gene ic a ia ion in communi y
pa e ns, compa ing bo h local and egional en i onmen al a ia-
ion. In addi ion, we examined how s ongly he bi o es hemsel es
can modi y a h opod communi ies associa ed wi h B. pendula by
supp essing he bi o es om hal o he saplings o e one g owing
season in one common ga den and su eying hei a h opod com-
muni ies he ollowing season.
Ma e ials and me hods
Plan ma e ial and s udy si es
The 22 di e en geno ypes o B. pendula we e cloned du ing sp ing
1998 om andomly selec ed B. pendula ees aken om a na u-
ally egene a ed B. pendula - B. pubescens Eh o es in Punkaha ju,
sou heas e n Finland (61°48′ N, 29°18′ E), o s udy gene ic a ia-
ion in phenology, g ow h, ep oduc ion and esis ance- ela ed ai s
among indi idual bi ch ees25. Sampling was s a i ied andom
sampling: six spo s whe e o es li could be ans e ed we e i s
selec ed a ound he o es , and 2–5 ees wi hin he each o o es
li in each spo we e hen andomly (by h owing a coin) selec ed
o ou s udy pu poses. B. pendula is p edominan ly a sexual spe-
cies, bu geno ypes can be cloned o s udy pu poses o o plan a-
ions using s anda d issue-cul u e me hods32. Cloned B. pendula
saplings we e plan ed a he g owing si es (i.e. common ga dens,
each app oxima ely 0.25 ha) in June 1999 o ind ou he deg ee
o which he geno ype and en i onmen a ec bi ch ai s and o
es how geno ypes di e in hei esponse o he en i onmen 26.
The Kuikannii y s udy si e (61°47′ N, 29°21′ E) is an abandoned
cul i a ed ield and he Pa ikkala s udy si e (61°36′ N, 29°36′ E) is
My illus ype o es 33. Soil ype was de ined as ine sandy ill o
bo h si es26. The dis ance be ween hese si es was a ound 30 km and
hey we e si ua ed a app oxima ely he same al i ude (Kuikannii y
79 m and Pa ikkala 93 m abo e sea le el). Thus, he mean sum-
me (June–Augus ) empe a u es we e e y simila a hese si es:
in 2002 mean empe a u es we e 17.6°C and 17.9°C and in 2003
hey we e 15.9°C and 15.6°C in Kuikannii y and Pa ikkala, espec-
i ely. Bo h s udy si es we e di ided in o six blocks, each o which
included ou saplings om each geno ype. To p e en edge e ec s,
he expe imen al saplings we e su ounded by one ow o ex a sap-
lings. F om each block, one o he ou saplings o a o al o 22
geno ypes was andomly selec ed o he p esen s udy in o de o
ha e six eplica es pe geno ype.
In addi ion, we collec ed addi ional da a om Kuikannii y in 2003
o in es iga e he e ec o p e ious insec he bi o y on insec com-
muni y s uc u e and abundance, and su eyed one ex a sapling
om each block and geno ype. These ex a saplings we e p o ec ed
om insec he bi o y in he p e ious g owing season by egula
sp ayings wi h syn he ic py e h in23, which has no di ec o side
e ec s on he g ow h o chemis y o bi ch seedlings34.
Measu ing insec abundance and species ichness
The insec he bi o e communi y o each sapling was assessed
by su eying he abundance o 23 (in Pa ikkala 2002) o 27 (in
Kuikannii y 2002–2003, and Pa ikkala 2003) insec axa om di e se
o de s (Lepidop e a, Hymenop e a, Coleop e a, Dip e a, Hemip e a;
Table 1). These axa we e gene ally he mos abundan axa in bo h
si es. Howe e , species ha we e a e in bo h si es we e included
in he su eys as well. Species iden i ica ions we e unde aken ol-
lowing Saalas35 species iden i ica ion guide, using se e al web pages
(h p://www. une . i/pub/sci/bio/li e/insec a/index.h ml; h p://www.
lea mines.co.uk/index.h m; h p://www.bladminee de s.nl/; h p://
www.n m.se/) wi h he assis ance o specialis s. Euce aphis be ulae
eggs we e coun ed om he side o wel e (2002) o eigh (2003)
Page 3 o 15
F1000Resea ch 2014, 3:34 Las upda ed: 09 SEP 2015
Table 1. Desc ip ion o he 27 axa su eyed o hei abundance among 22 geno ypes in Kuikannii y and Pa ikkala ield
expe imen s 2002 and 2003.
2002 2003
Kuikannii y Pa ikkala Kuikannii y Pa ikkala
Taxa Iden i ica ion To al numbe o insec s/damage coun ed
Lepidop e an mine s/ olle s
G acilla idae 1 (mine ) Phyllono yc e ca ella 282 123 53 34
G acilla idae 2 (mine ) Phyllono yc e sp. 1 61 26 12 4
G acilla idae 3 (mine ) Phyllono yc e sp. 2 19 7 3 3
G acilla idae 4 (mine ) Pa o nix be ulae 114 42 40 10
G acilla idae 5 (mine ) Pa o nix sp. 30 11 20 0
E ioc anidae (mine ) E ioc ania sp. 536 2007 746 2374
Py alidae ( olle o ie ) en a i ely Euzopho a uliginosella 67 77 135 142
To icidae (galle ) Epino ia e aque anaa159 136 159 136
Nep iculidae (mine ) S igmella sp. 1 40 53 7 1
Incu anidae (mine ) Phyllopo ia bis igella 125 6 30 8
Geome idae ( olle o ie ) Rheumap e a has a a 11 6 4 0
Gelechiidae ( olle o ie ) en a i ely Teleiodes sp. 87 - 211 37
Mi colepidop e a 1 ( olle o ie ) 64 65 188 60
Lepidop e a 1 ( olle o ie ) 8 2 3 0
Lepidop e a 2 (mine ) 12 - 7 3
Lepidop e a 3 ( olle o ie ) 0 1 13 1
Lepidop e a 4 (mine ) 142 7 152 82
Coleop e ans
A elabidae ( olle ) Depo aus be ulae 62 14 157 133
Cu culionidae (mine ) O ches es usci 54 127 23 12
Hymenop e ans
Ten h edinidae 1 (mine ) en a i ely Fenusa pumila 149 109 66 59
Ten h edinidae 2 (lea eede ) Hemich oa aus alis 167 - 52 18
Ten h edinidae 3 (lea eede ) C oesus sep en ionalis 108 7 34 0
Cimbicidae (lea eede ) T ichiosoma sp. 6 2 2 0
Dip e ans
Ag omyzidae (mine ) 1 Ag omyza alnibe ulae 24 11 33 6
Cecidomyiidae (mine ) 1 0 0 1 19
Hemip e an
Aphidoidea (sap sucke ) Euce aphis be ulae 996 2640 40 114
He e op e an
He e op e an 1 (sap sucke ) 92 - 284 466
a E. e aque ana coun s ep esen he damage du ing he whole li e ime o he saplings (see Ma e ials and me hods). No e also ha yea s a e no di ec ly
compa able because o he changed sampling p o ocol be ween yea s.
Page 4 o 15
F1000Resea ch 2014, 3:34 Las upda ed: 09 SEP 2015
opmos buds in Ap il be o e budbu s . Howe e , in 2002 E. be ulae
eggs we e coun ed om wo saplings pe geno ype pe block (sum
o he eggs on he sides o 24 buds was used in he analysis),
because egula sp ayings wi h syn he ic py e h in on he o he sap-
ling was s a ed only a e egg coun s in bo h si es. T ichiosoma sp.
pupae we e coun ed in Ap il/May when he iming o budbu s o
he same saplings was obse ed (Possen, submi ed manusc ip ).
The abundance o E ioc ania sp. was de e mined a he end o June,
Depo aus be ulae a he beginning o July and He e op e an 1 (sap
sucke ) in Augus . C oesus sep en ionalis la al colonies and he
numbe o la ae in each colony we e eco ded along wi h E ioc ania
and D. be ulae measu emen s in bo h yea s. The abundance o all
o he insec s we e de e mined indi ec ly by coun ing damaged
lea es a he beginning o Sep embe in bo h yea s, since he dam-
age caused by mos o he su eyed axa emained iden i iable o a
long ime a e he ini ial damage.
In gene al, he insec abundance in 2002 was de e mined by su -
eying he whole sapling. The mean heigh o hese saplings a he
end o 2002 was 253 ± 4.3 cm (mean ± SE) in Kuikannii y and
227 ± 3.8 cm in Pa ikkala. Because B. pendula geno ypes di e in
hei heigh and diame e g ow h23 and la ge saplings may ha bo
mo e insec s han smalle saplings, we de e mined he whole sap-
ling “su ace a ea” and used i as a co a ia e he ea e called “size
index” in s a is ical analysis. Su ace a ea was de e mined by pho-
og aphing each sapling sideways om hei sou he n side agains
a whi e backg ound, con e ing he pic u e o a black and whi e sil-
houe e pic u e in Adobe Pho oshop 7.0 and de e mining he num-
be o black pixels (i.e. lea and b anch a ea) wi hin he pic u e. The
numbe o pixels was con e ed o m2 using he numbe o pixels
o a known a ea as a e e ence. The amoun o pixels signi ican ly
(p < 0.001) explained o e 73% o he sapling olume [Y = (3.14
* {base diame e /2}2 * heigh )/3] in bo h si es. The abundance o
Phyllono yc e ca ella, Phyllono yc e sp. 1, Pa o nix be ulae and
Pa o nix sp. was no examined on he whole sapling, bu was
de e mined as he damage (i.e. numbe o mines pe each species)
ound wi hin a pe iod o 30 seconds. The pe iod o ime (30 sec)
was chosen so ha e en he smalles saplings had lea es uncoun ed
when he ime was up.
Since he me hod o assessing he bi o e abundance/ esis ance by
ime coun s has been success ully used in he pas 35,36 we decided
o use ime coun s o de e mine he abundance o almos all axa
(excep E. be ulae, T ichiosoma sp. and C. sep en ionalis) in 2003.
The same pe son unde ook all su eys. The abundance o easily
isible damage (la ge mines and olls) o E ioc ania sp., D. be ulae
and He e op e an 1 we e de e mined as he numbe o damaged
a eas ound wi hin a pe iod o 30 seconds. Epino ia e aque ana
“knobs” in he b anches o he saplings we e coun ed wi hin a
pe iod o 20 seconds in 2003 s a ing a he op o he ee. Since
he “knobs” in he b anches emain isible o yea s and we did
no sepa a e di e en yea ’s g ow h while su eying, he alues
ep esen he accumula ion o E. e aque ana damage du ing he
las ew yea s. The e o e he same alues we e used in bo h yea s’
insec communi y analyses. The abundance o all o he 20 axa in
2003 was de e mined wi hin a single ime coun o each sapling a
he beginning o Sep embe . To examine a simila p opo ion o each
sapling, hey we e di ided in o h ee size ca ego ies acco ding o hei
heigh and numbe o lea es. Small saplings (a e age heigh 2.8 and
3.2 m in Pa ikkala and Kuikannii y, espec i ely) we e su eyed
o 30 seconds, a e age sized saplings (3.5 and 3.9 m in Pa ikkala
and Kuikannii y, espec i ely) o 60 seconds and la ge saplings
(4.5 m in Kuikannii y, la ge saplings we e no ound in Pa ikkala)
o 120 seconds. Su eying ime was used as a co a ia e called size
index in s a is ical analysis.
Da a analyses
All mul i a ia e analyses we e pe o med wi h P ime 6 (P ime -E
L d, Uni ed Kingdom). The ull da a ma ix consis s o he abun-
dance o 23–27 (23 in Pa ikkala 2002) insec species in 264 saplings
(22 geno ypes, 6 blocks, 2 si es) ha we e su eyed in wo consecu-
i e yea s. All su eyed insec species we e included in he s a is i-
cal analysis when si es we e es ed sepa a ely, bu hose ou species
ha we e no su eyed in Pa ikkala 2002 we e excluded also om
Kuikannii y 2002 da a when si es we e compa ed. A h opod com-
muni y composi ion da a was analyzed using non-pa ame ic mul-
i a ia e analysis o a iance (PERMANOVA), which is well sui ed
o non-no mal ecological da a such as ou s38,39. Yea s we e analyzed
sepa a ely in all s a is ical es s, because o he changed sampling
p o ocol be ween yea s (su eying he whole ee in 2002, using
ime coun s in 2003). All da a was ou h oo ans o med p io
o analysis o educe di e ences be ween common and a e spe-
cies. The semime ic Bay-Cu is dis ance, which gene ally seems
o p o ide he mos meaning ul measu e o dissimila i y in ecologi-
cal communi y s uc u e39, was used o calcula e dis ances be ween
each pai o obse a ions. The esul ing dis ance ma ix was used
o ob ain p- alues using a andom subse o 4999 pe mu a ions in
PERMANOVA. The pe mu a ion me hod was pe mu a ion o esidu-
als unde a educed model. The s a is ical model was designed o
es he e ec o geno ype, si e, block (nes ed wi hin si e) and he
in e ac ion o geno ype × si e using sapling size index (sapling
su ace a ea in 2002 and su eying ime in 2003, see abo e) as a
co a ia e. Si e was ea ed as a ixed ac o and block and geno-
ype as andom ac o s in he model. In addi ion o hese analy-
ses, we sepa a ely es ed he e ec o geno ype and block on insec
assemblages in each si e and yea o calcula e he p opo ion o
a iance explained by B. pendula geno ype and local en i onmen
(i.e. eplica ed block). Addi ional da a collec ed om hose saplings
ha we e p o ec ed om insec he bi o y in he p e ious g owing
season in Kuikannii y 2003, we e combined wi h he Kuikannii y
2003 non- ea ed sapling da a p io o analyzing he e ec s o insec
emo al, block and geno ype, and hei wo-way in e ac ions wi h
he insec assemblages wi h PERMANOVA. Sapling size index was
used as a co a ia e.
To isualize he mul i a ia e pa e ns among obse a ions, non-
me ic mul idimensional scaling (nMDS) was pe o med on he
Bay-Cu is dis ances. The dis ance among cen oids o g oups o
samples was de e mined p io o nMDS o inc ease cla i y, e.g. when
he whole da a was isualized we had 88 geno ype-si e-yea poin s
(22 geno ypes in 2 si es o e 2 yea s) ins ead o 528 geno ype-
block-si e-yea poin s. To isualize he e ec o geno ype in indi-
idual si e and yea , we sepa a ely de e mined he dis ance among
geno ype cen oids in each si e and yea and p oduced one nMDS
plo om each o hese “en i onmen s”. Addi ional Kuikannii y
2003 da a combined wi h Kuikannii y 2003 aw da a was used o
Page 5 o 15
F1000Resea ch 2014, 3:34 Las upda ed: 09 SEP 2015

isualize he e ec o insec emo al on insec assemblages using
nMDS on he geno ype cen oids o hose saplings ha we e ei he
p o ec ed om he bi o y o g own unde na u al he bi o y.
Species ichness (numbe o species/sapling) and o al mean abun-
dance (numbe o he bi o es/sapling) was s a is ically es ed by anal-
ysis o co a iance using SPSS 20.0.0.1 (IBM SPSS S a is ics) Gene al
Linea Models (GLM) p ocedu e. Those ou species ha we e no
su eyed in Pa ikkala 2002 we e excluded also om Kuikannii y
species ichness and o al mean abundance calcula ions o be e
enable si e compa isons. Geno ype and block (nes ed wi hin si e)
we e ea ed as andom ac o s and si e as a ixed ac o in he s a-
is ical model while sapling size index was used as a co a ia e.
Addi ional Kuikannii y 2003 da a combined wi h Kuikannii y 2003
basic da a was used o analyze he e ec s o insec emo al, block
and geno ype, and hei in e ac ions wi h he species ichness and
o al mean abundance. Geno ype and block we e ea ed as an-
dom ac o s and insec emo al as a ixed ac o while sapling size
index was used as a co a ia e. To al mean abundance was log(x+1)-
ans o med o equalize he e o a iances ac oss g oups in bo h
analyses.
Resul s
S udy yea s and si es we e dis inc ly g ouped apa in o wo-
dimensional o dina ion space, when he geno ype cen oids o di e en
yea s and si es we e analyzed using nMDS (Figu e 1). The MANOVA
Table in u n, shows ha si es had s a is ically signi ican ly di e en
insec species communi y composi ion in bo h yea s (Table 2). Si es
we e also clea ly di e en in hei o al mean abundance (Table 3)
and species ichness (p < 0.008 o he si e e ec in species ich-
ness): he o es si e o Pa ikkala had a 49–78% highe o al mean
abundance, bu 18–25% lowe species ichness han he abandoned
ield si e o Kuikannii y in 2002–2003, espec i ely. These indings
indica e ha each yea and si e had signi ican ly di e en he bi o-
ous insec assemblages, hus c ea ing di e en bio ic en i onmen s.
Geno ypic a ia ion and geno ype × en i onmen in e ac ions
B. pendula geno ypes we e signi ican ly di e en in hei insec
species communi y composi ion in bo h s udy yea s (Table 2). In
2002, egional scale en i onmen al (si e) a ia ion explained mo e
o he o al a ia ion in species composi ion han he geno ype (13.9
and 8.0%, espec i ely), while in 2003 he geno ype explained mo e
o he o al a ia ion han he si e (12.1 and 3.8%, espec i ely).
Signi ican geno ype × si e in e ac ion, which explained 8.2% o
he o al a ia ion, was ound only in 2003. When he si es we e
es ed sepa a ely in bo h yea s we ound ha he e ec o geno-
ype was signi ican in Kuikannii y 2002 and bo h s udy si es in
2003 (Table 4, Figu e 2). B. pendula geno ype could accoun o
15.8–27.0% o he o al a ia ion in communi y s uc u e, while
local scale en i onmen al (block) a ia ion explained 5.9–7.6% o
he o al a ia ion in communi y s uc u e (Table 4, Figu e 2).
B. pendula geno ypes also signi ican ly di e ed in hei o al mean
abundance o he bi o es (mean numbe o he bi o es/sapling): he
o al mean abundance o he mos suscep ible geno ype was 5.4-
and 3.2- old compa ed o he o al mean abundance o he mos
esis an geno ype in Kuikannii y and Pa ikkala 2002, espec i ely
(Table 3, Figu e 3). In 2003, only he geno ype × si e in e ac ion
was s a is ically signi ican , which indica es ha he geno ype
e ec s ongly depended on he s udy si e. Indeed, when we es ed
he s udy si es sepa a ely, geno ype e ec was signi ican only in
Pa ikkala (ANCOVA: Pa ikkala F21,104=2.29, p=0.003; Kuikannii y
F21,103=1.48, p=0.103). The species ichness (numbe o insec spe-
cies/sapling) was no signi ican ly a ec ed by he B. pendula geno-
ype o geno ype × si e in e ac ions in ei he yea (p>0.134).
Local scale geno ype × en i onmen in e ac ion (i.e. he in e ac ion
o geno ype × eplica ed block) was s udied in Kuikannii y 2003.
Insec species communi y composi ion was signi ican ly a ec ed by
bo h geno ype and geno ype × block in e ac ion (Table 5). Geno ype
a ia ion explained 10.6% and geno ype × block a ia ion 38.0%
o he o al a ia ion in insec communi y composi ion, indica ing
ha geno ype e ec is also s ongly a ec ed by local scale en i on-
men al a ia ion. To al mean abundance o species ichness was no
a ec ed by geno ype o geno ype × block in e ac ion (p>0.097).
E ec s o he p e ious yea ’s he bi o y on insec communi ies
P e ious yea he bi o y changed he insec communi y composi-
ion o B. pendula saplings (Table 5). The geno ype cen oids o
hose saplings ha we e ei he subjec ed o na u al he bi o y o
p o ec ed om i we e loca ed on he opposi e sides o he wo-
dimensional nMDS o dina ion plo , al hough o e lapping is e i-
den (Figu e 4). P e ious yea he bi o y did, howe e , explain
only 4.4% o he o al a ia ion in insec communi y composi ion.
To al mean abundance was a ec ed by he p e ious yea ’s he bi o-
y as well, bu species ichness was no (ANCOVA: e ec s o insec
emo al on o al mean abundance F1,5.28=34.6, p=0.002 and species
ichness p>0.829).
Figu e 1. Non-me ic MDS plo o insec assemblages o 23
species colonizing 22 B. pendula geno ypes in Kuikannii y and
Pa ikkala 2002 and 2003. S ess is 0.14, which indica es a good
ep esen a ion o he da a in wo-dimensional o dina ion plo . Each
poin is a cen oid o six eplica es. Numbe s in he cen e o he
ma ke s a e geno ype iden i ica ion numbe s.
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Table 2. Non-pa ame ic MANOVA able o he e ec s o geno ype and si e on insec
he bi o e communi y s uc u e on B. pendula saplings in 2002–2003. Sapling size
index, which is a measu e o heigh and numbe o lea es (see ma e ial and me hods), was
used as a co a ia e.
Insec he bi o e communi y 2002 Insec he bi o e communi y 2003
d SS F P d SS F P
Geno ype 21 27700 1.26 0.04 21 33294 2.04 < 0.001
Si e 1 47798 16.99 < 0.001 1 10319 7.62 < 0.001
Block (Si e) 10 17826 1.70 0.002 10 18013 2.31 < 0.001
G × S 21 22242 1.01 0.466 21 22472 1.37 0.006
Size index 1 4890 4.65 < 0.001 1 8084 10.38 < 0.001
Residual 208 218510 208 162000
To al 262 344260 262 274880
Table 3. The ANCOVA able o he e ec s o geno ype, block and si e on
o al mean abundance o he bi o es (log[x+1] ans o med) o B. pendula
saplings in 2002–2003. Sapling size index, which is a measu e o heigh and
numbe o lea es (see ma e ial and me hods), was used as a co a ia e.
Mean abundance 2002 Mean abundance 2003
d SS F p d SS F p
Geno ype 21 1.10 2.82 0.011 21 0.26 1.08 0.435
E o 21 0.39 21 0.24
Si e 1 1.13 14.6 0.004 1 0.59 46.7 < 0.001
E o 9.6 0.75 26.7 0.34
G × S 21 0.39 1.00 0.470 21 0.24 1.81 0.019
E o 208 3.88 208 1.30
Block (Si e) 10 0.77 4.11 < 0.001 10 0.16 2.55 0.006
E o 208 3.88 208 1.30
Size index 1 0.30 16.3 < 0.001 1 0.23 36.4 < 0.001
E o 208 3.88 208 1.30
Table 4. Non-pa ame ic MANOVA able o he e ec s o geno ype and block on insec he bi o e
communi y s uc u e on B. pendula saplings in Kuikannii y and Pa ikkala 2002–2003. Sapling
size index, which is a measu e o heigh and numbe o lea es (see ma e ial and me hods), was
used as a co a ia e.
Insec he bi o e communi y 2002 Insec he bi o e communi y 2003
d SS F P d SS F P
Kuikannii y
Geno ype 21 33778 1.29 0.018 21 25678 1.33 0.013
Block 5 10803 1.73 0.006 5 10305 2.25 < 0.001
Size index 1 4468 3.58 0.001 1 5948 6.48 < 0.001
Residual 103 128690 103 94495
To al 130 181760 130 138930
Pa ikkala
Geno ype 21 16771 1.08 0.297 21 29083 2.16 < 0.001
Block 5 8067 2.17 < 0.001 5 7754 2.41 < 0.001
Size index 1 1735 2.34 0.033 1 2811 4.38 0.001
Residual 104 77278 104 66834
To al 131 105910 131 107680
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F1000Resea ch 2014, 3:34 Las upda ed: 09 SEP 2015
popula ion s and (< 0.9 ha) in eas e n Finland, whe e his Eu asian
deciduous ee species is pa icula ly abundan 42. By con as , we
migh ha e exagge a ed he ole o egional en i onmen al a ia-
ion and geno ype × en i onmen (si e) in e ac ions by plan ing ou
geno ypes on wo a he di e en a eas (open o es and abandoned
ield, a eas ha a e ypically apidly colonized by B. pendula) a a
much la ge scale (70,000 ha). The e o e, i is no su p ising ha he
impo ance o he gene ic a ia ion in s uc u ing insec he bi o e
communi ies o B. pendula dec eased om 15.8–27.0% (o a ia ion
explained) o 8.0–12.1% wi h inc easing spa ial scale in ou s udy.
O he s udies ha e also ound ha while he e ec o a geno ype can
be clea on local scales (wi hin common ga dens), i may be pa ially
swamped by en i onmen al a ia ion on la ge scales7,43.
I has been a gued ha , because hos plan geno ypes ha e o en been
collec ed om la ge geog aphic a eas and s udied wi hin he con-
ines o a single common ga den, he ole o he hos plan geno ype
in a h opod communi y pa e ns has been la gely o e es ima ed12.
Indeed, Tack e al.13 showed ha spa ial p ocesses domina ed
gene ic e ec s when geno ypes o Q. obu we e collec ed a he
same local (500 ha) o egional (1 million ha) scale as ha whe e
expe imen s we e conduc ed, and hus, in eal landscapes, spa ial
impac s migh elega e hos plan geno ype o a mino ole. Ou
esul s, howe e , sugges o he wise, because geno ype explained
abou h ee imes mo e o he o al a ia ion in insec he bi o e
communi y s uc u e han local en i onmen (block) in bo h si es
(Table 4), and he scale o ou common ga den(s) was app oxi-
ma ely he same as he scale o ha whe e geno ypes we e collec ed
(< 0.9 ha). In addi ion, on a egional scale, gene ic and en i on-
men al e ec s explained simila p opo ions o he o al a ia ion in
a h opod communi y s uc u e (Table 2), e en hough we migh
ha e in la ed he ole o he en i onmen in ou s udy. This dis-
c epancy in ou esul s migh pe haps be a ibu ed o he di e -
ence in he dis ibu ion o hese wind-pollina ed ee species: he
popula ions o Q. obu a e s ongly agmen ed and g ow a he
no he n ma gin o he species’ Eu opean dis ibu ion in sou he n
Finland (whe e Tack e al.13 conduc ed hei expe imen s), while
Figu e 2. Non-me ic MDS plo o insec assemblages o 23
(Pa ikkala 2002) o 27 species colonizing B. pendula geno ypes in
a) Kuikannii y 2002, b) Pa ikkala 2002, c) Kuikannii y 2003 and d)
Pa ikkala 2003. Each poin is a cen oid o six eplica es. Numbe s
in he cen e o he ma ke s a e geno ype iden i ica ion numbe s.
Whi e ci cles deno e geno ypes in Kuikannii y, black ci cles deno e
geno ypes in Pa ikkala. S ess alues >0.2 indica e ha his da a
may be be e isualized wi h mo e dimensions (s ess o h ee-
dimensional solu ions a ied be ween 0.14 o 0.16).
Co ela ions be ween species
The associa ions be ween insec species ac oss geno ypes in di -
e en si es and yea s seemed o be based on andom associa ions,
since we ound only one co ela ion ha was signi ican a e
sequen ial Bon e oni co ec ion40. An uniden i ied galle y mine
(Lepidop e a 4) and E. uliginosella we e co ela ed ac oss geno-
ypes in Kuikannii y 2002 (Pea son’s co ela ion; in 2002, = 0.88,
n = 22, p < 0.0001; in 2003, = 0.545, n = 22, p = 0.009), bu no in
Pa ikkala (p>0.199).
Communi y s uc u e o insec he bi o es on di e en geno ypes
o sil e bi ch (Be ula pendula)
3 Da a Files
h p://dx.doi.o g/10.6084/m9. igsha e.915332
Discussion
Ou esul s p o ide e idence ha gene ic a ia ion wi hin a na u al
B. pendula popula ion can modi y he s uc u e o he a h opod com-
muni y e en hough all geno ypes suppo ed simila insec species
ichness. Gene ic a ia ion in pheno ypic plas ici y, howe e , seemed
o be he majo ac o a ec ing he abundance and s uc u e o he
insec he bi o es associa ed wi h his ee species, because geno-
ype e ec was o en dependen on he en i onmen al a ia ion a
bo h egional (Table 2 and Table 3) and local scales (Table 5). Those
B. pendula geno ypes ha we e used in ou s udy should gi e unbi-
ased es ima es o he ue a iance ha is p esen in B. pendula popu-
la ions, since we chose hem andomly om one na u ally egene a ed
Figu e 3. Mean abundance o insec he bi o es (±SE) among
B. pendula geno ypes in Kuikannii y and Pa ikkala s udy si es
in 2002–2003. Whi e ba s: Kuikannii y, black ba s: Pa ikkala.
Page 8 o 15
F1000Resea ch 2014, 3:34 Las upda ed: 09 SEP 2015
B. pendula has a wide and mo e con inuous dis ibu ion o e he
whole o Finland, apa om Lapland. Q. obu popula ions exhibi
highe geog aphic di e en ia ion es ima es, Fs 0.032 o B. pendula
and 0.066 o Q. obu 44,45, which means ha he gene low among
B. pendula popula ions is wo imes highe han among Q. obu
popula ions, and hus local B. pendula popula ions migh exp ess
a la ge amoun o gene ic a ia ion han popula ions o Q. obu .
We ound ha insec he bi o e communi ies can be a ec ed by
bo h local and egional geno ype × en i onmen in e ac ions, a
leas in some yea s. Bu why do B. pendula geno ypes suppo di -
e en insec communi ies in di e en en i onmen s? I is possible
ha esis ance ai s o he geno ypes a e changed due o di e -
ences in abio ic en i onmen and insec communi ies espond o
hese changes. This is suppo ed by he ac ha ea lie s udies
ha e ound egional geno ype × en i onmen in e ac ions in he
seconda y me aboli es o he same s udy saplings26. Ye , we do no
know whe he geno ype × en i onmen in e ac ions in B. pendula
esis ance ai s exis a a local scale and ecen s udies sugges ha
seconda y me aboli es a e no he mos impo an an i-he bi o e
de ence o plan s31. On he o he hand, spa ial p ocesses migh
a ec local insec communi ies and c ea e geno ype × en i onmen
in e ac ions. Fo example, in ou expe imen whe e geno ypes o
each block a e a anged andomly, he e ec s o a pa icula geno-
ype could be pa ially masked by he e ec s o hei conspeci ics
in some blocks i nea by geno ypes a e e y dissimila , i.e. he e is
associa ional esis ance (see a e iew by Ag awal e al.46) a he
le el o a geno ype. Bo h o hese p ocesses may be a ec ing di -
e en insec species di e en ly. We ound only one species pai
ha was co ela ed ac oss geno ypes in one o ou s udy si es,
which, oge he wi h ea lie indings47,48, indica es ha gene alized
de enses agains mul iple insec species a e no likely in B. pendula
(see Leimu and Ko iche a49). Addi ionally, i may also be ha local
insec communi ies di e in hei esponse ega dless o spa ial p o-
cesses and wi hou any change in he ai s o B. pendula.
The size o B. pendula ees is posi i ely associa ed wi h hei i ness,
i.e. seed p oduc ion29. I has been shown ha he bi o es can educe
he g ow h o B. pendula by up o 46% (Mikola e al. unpublished
esul s, see also P i inen e al.22, Sil e e al.23) and inc ease
seedling mo ali y conside ably50. Thus, by imposing selec ion in
a ious gene ically a iable esis ance ai s o B. pendula25,26,51,
he bi o es may ha e high po en ial o d i e he communi y e olu-
ion in B. pendula. Indeed, we ound ha only one season o p o-
ec ion om he bi o y changed a h opod communi y a iables
(mean abundance and communi y composi ion) in i e-yea old
ield-g own B. pendula saplings. To al mean abundance, o exam-
ple, was lowe in saplings ha we e p o ec ed om he bi o y in he
p e ious g owing season, which indica es ha hey may ha e had
mo e esou ces o de end hemsel es agains insec s when he bi-
o es we e p esen again. Ye , he magni ude o hese e ec s was
smalle han he e ec s o local en i onmen al (block) a ia ion,
and could explain only abou 4% o he o al a ia ion in a h o-
pod communi y s uc u e. I is impo an o no e, howe e , ha in
na u e B. pendula seedlings ypically es ablish in open pa ches, whe e
high numbe s o indi iduals compe e hea ily be o e sel - hinning
elimina es some o he seedlings. Su i ing o hese i s yea s and
consequen ly eaching ma u i y is c ucial o an indi idual’s i ness
in his long-li ed ee species. Ea lie s udies ha ha e used open-
pollina ed p ogeny o he same geno ypes, ha e shown ha in such
dense s ands, e en mode a e le els o insec he bi o y can change
he gene ic s uc u e o B. pendula popula ions in he i s yea o
es ablishmen 52. This is eminiscen o ecen s udies, which ha e
demons a ed ha na u al selec ion can a ou di e en geno ypes in
he absence o he bi o es a he han in hei p esence, and di e en
geno ypes in esponse o di e en he bi o e species wi hin only ew
gene a ions o annual o biannual plan s53,54 (see also Ha e55).
Table 5. Non-pa ame ic MANOVA able o he e ec s o
geno ype, block and p e ious yea insec emo al on insec
he bi o e communi y s uc u e among B. pendula saplings
in Kuikannii y 2003. Sapling size index, which is a measu e o
heigh and numbe o lea es (see ma e ial and me hods), was
used as a co a ia e.
d SS F P
Geno ype 21 30358 1.39 0.004
Insec emo al 1 12525 7.11 < 0.001
Block 5 10930 2.13 < 0.001
G × IR 21 15557 0.90 0.743
G × B 104 109030 1.27 0.002
IR × B 5 6031 1.46 0.069
Size index 1 2078 2.52 0.023
Residual 103 84964
To al 261 286640
Figu e 4. Non-me ic MDS plo s o insec assemblages o 27
species colonizing 22 B. pendula geno ypes ha we e ei he
subjec ed o na u al he bi o y o p o ec ed om he bi o y in
he p e ious g owing season in Kuikannii y 2003. Each poin is
a cen oid o six eplica es. Numbe s in he cen e o he ma ke s a e
geno ype iden i ica ion numbe s.
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