Table Of ContentINBREEDING DEPRESSION INAUSTRALIAN BUTTERFLIES
SOME IMPLICATIONS FORCONSERVATION
A.G, ORR
Orx,AG. 19940630: InbreedingdepressioninAustralianbutterflies: sameimplications for
conservation, MemoirsofM»* QueenslandMuseum 36( 1>; i79-184. Brisbane. ISSN 0079
8835.
Inbreeding depression inbutterflies is manifested in many ways, including egg inviability,
retarded larval development and premature mortality, failure to complete pupation and
increased mortality during the pupal stage and at eclosion, and reduction in size ofadults
withanassociatedlossofvigourandreducedfecundity.Ofthespeciesexamined,inbreeding
depression was most severe in Papilionidae. especially the troidines Cressida cressida
(Fabricius) and OrnUhoptera richmondia (Gray), and in the papilionine Papitio aegeus
(Donovan). InCcressida, hatchingratesfrommalingsbetween full siblingsaveragedabout
40% and very few larvae survived to adulthood, whereas hatching rates from presumed
outbredmalingswerenearly 100%.HatchingratesfromfullsiblingrnatingsinO.richmondia
and P. aegetts were about 70% and declined sharply as the coefficient of inbreeding was
increased Inotherspeciestested,papWiontfaChftastiafiacfusCMS. Macieaytund Gmphium
macU.axiinum (Le&ch), the piend Delias nigrtna (Fabnuus) and the nymphulids Danous
ajfinis (Fabricius) and Tellemo zoilus (Febrkius). inbreeding depression was cither run
detected or was not apparent until the inbreeding coefficient exceeded 0.5. Inbreeding
depression may be more severe in wide ranging species with an open population structure,
anditisevidentthatgiventhe severityofinbreedingdepressionrecorded introidinespecies
such as Qrnifhoptera rtchmondia. it is necessary to conserve adequate habitai to maintain
viablepopulations.Evidenceispresentedol inbreedinginwildO. richmondia.{^Butterflies,
rpatiOHt capt'n-e breeding, inbreedingdepression, Papihomdae.
AG Orrf DepartmentofHtola\i\K UntversiuBruneiDarussalam, Gadong3IH6. Brunei 12
July 199.1
Deleterious effects ofinbreeding in organisms mentsandfrequently subjecttocatastrophicmor-
as diverse as white mice, Drosophilia and cul- talityduetoadverseweather(Ehrlichet aj„ 1972,
tivated maize are well known (Falconer, 1981; 19X0).
Wright, 1977).Typically,reproductiveprocv In general, inbreeding depression would most
andearlydevelopmentare mostaffected(Frankcl likely be severe in wide ranging species which
& Soule, 1981). In holometabolousinsects, ways habitually nutbreed, either because their open
m which inbreeding depression can be expressed populationstructurehasallowedaccumulationof
include reduction in size of adult progeny and deleterious alleles or because they have been
reduced fecundity, retarded larval development selected for a mating system which maximises
andfailuretopupateoreclosesuccessfully.More
outbreeding becauseoftheeffects ofinbreeding
severecases maysufferprematuredeathinlarval
In eithercase, in the short time allowed to adjust
stages or in the egg, sometimes very early in
embryogenesis Clayton et aL 1957; Wallace & to human alteration ofthe environment, species
Madden. 1965;Wtright, 1977). subject tosevere inbreedingdepression will need
on average larger minimum viable populations
Despite extensive breeding programmes for That means largerareas ofsuitable habitat. They
scientific and commercial purposes, inbreeding
will also generally be more sensitive to habitnr
depression hus seldom been reported in but-
fragmentation. Although the degree to which
terflies. In a survey of case histories of extinc-
tions, Ehrlkrh (1983) concluded that stochastic they are affected will depend on their ability to
demographic factors caused extinction long disperse, especially across tracts o\ unfavourable
before inbreeding would have had a chance to habitat. Inbreeding depression may also tend to
take effect. Ehrlich's sample may have been un- be a more significant tactor in extinctions of
representative since he considered mostly tropical species, many of which habitually exist
localised species from relatively closed popula- at low population levels and may often pass
5 (Ehrltch. 1965; Gilbert ft Singer, 1973) through prolonged bottlenecks (Owen, 1971;
inhabiting temperate, highly seasonal environ Wolda, 1978) butarc probably notnormallysub-
1X0 MEMOIRS OFTHEQUEENSLAND MUSEUM
ject to catastrophic density independent mor- they died or pupated and developmental times
tality. wererecorded.Successfullyeclosingadults(with
I here investigate the effects of inbreeding in inbreedingcoefficientF=0.25)fromsizoftheten
laboratory crosses in eight species of tropical original lines were mated: 1, with their sibs; and
butterflies. Species chosen are common and 2, with the inbred progeny from other lines.
widespread but knowledge of their inbreeding Hatchingratesofsamplesof 100eggsperfemale
susceptibilities may suggest possible risks in re- were recorded andall larvaewereraised as faras
lated vulnerable species. possible. From resultingprogeny (F=0.44),three
unrelated pairs ofsiblings were mated witheach
MATERIALS AND METHODS otherandhatchingratesrecorded.Twopairsfrom
different lines were crossed and hatching rates
recorded. Similardata wereobtainedforO. rich-
Speciesstudiedwere Orniihopterarichmondia tnondia, based on an initial stock of five wild
(Gray), Cressida cressida (Fabricius), Papilio females, five inbred pairs per generation, and
aegeus Donovan, Chilasa anactus (W.S.
samplesof50 eggs.
Macleay), Graphium macleayanum (Leach) (all For Tellervu zoilus, the offspring of four
Papilionidae), Delias ntgtltia (Fabricius)
females were inbred for tout generations, select-
(Picridae),Danausaffmis(Fabricius)and Teller-
ing one pair from each line each generation.
vo zoilus (Fabricius) (Nymphalidac). and were
selecled because wild material was readily avail- Hatching rates, larval survival and developmen-
able forcaptivebreeding and, in mostcases,data tal rates, and adult sizes were recorded as above
Also, the lifetime fecundity of subsamplcs of
were available on population structure based on
females was recorded
mark-release-recapture (MRR)dala.
For all species, 5-10 mated females were col- RESULTS
lected from the wild and allowed lo oviposit on
their host plants in a 2.5 x 3 x 4m flight »
These females had presumably mated with an I, Cressida cressidu: Hatching rates of eggs
unrelated male. Eggs were collected from each laid by wild females were all high, ranging from
female as they were laid and 10-20 larvae were 97-100% (n=100), as was larval survivorship
reared to adulthood on appropriate hoslplanl (89%, n=100) (Fig. I). Hatching rates of eggs
From these progeny, at least one brother-sister with an inbreeding coefficient (Fofftprmg) of 0.25
mnling wasarranged amongthe progeny ofeach ranged from zero to 79% with a mean of 437o.
original female. Mating* were allowed to take larvae which hatched frequently showed
placeintheflightcage.Thaiavoidedhandpairing retarded growth (Fig. 2), particularly in early
which might have interfered with normal instars, and survivorship to adult stage was low,
reproductive processes. The first 50 or 100 eggs averaging7.3%ofeggshatching. Developmental
produced by each comttingumeously mated times ranged from 21-47 days (mean, 33 days),
female were collected as they were laid, and the considerably longer than the normal develop-
hatchingratewasmonitored. Anyeggs whichdid
nothatchorshowotherexternalsignsoldevelop-
ment (like darkening aftersclerotization ofhead
capsule) were dissected and examined micros-
EGGS HATCHING
copically to check for an embryo, indicating the
egg was fertile. A subsamplc of hatching eggs
(usually 50-100) including roughly equal num-
bers from each of the inbred matings was reared
to adulthood and survival recorded Forcwing
lengths of surviving adults were measured and
compared with the midparcnt value.
More extensive dara were obtained for Cres-
sidacressidaandO. riihtnomlia. ForCcressida, 025 05 075
COEFFICIENT OF INBREEDING
initial stock was provided by 10 wild caught
females(presumedoutbred). Fromtheirprogeny FIG. I. Effecis of increasing levels of inbreeding on
four inbred sib-sib matings each were arranged, hatching rate of eggs (solid line), and survival of
and 100eggscollectedfrom each female, in total hatching larvae (dashed line) in Cressida cresskhi,
400 eggs. All hatching larvae were raised until Verticalbars indicatestandarddeviations.
INBREEDINGDEPRESSIONIN BUTTERFLIES 181
TABLE 1. Hatching rates and larval survivorship from inbred matings in five butterfly species. In all cases
coefficientofinbreedingequals0.25.
Species Papiliaaegeus Chitasaanactus mGarcalpehatusrannum Deliasnigrina Danausaffinis i
Totalnumberofinbredmatings to :. 6 * 5
Meanhatchingrate& total ln| 69%|500] 97%[250] 96%f30O] 99%[500] 98*12501
Meanlarval survivorship|n] 32*|501 87%|60t 02'ljSOl 82%[I20] 85%[45]
larval survivorship was 5.9% of hatching eggs
(13 adults from 600eggs). When these F2 adults
were mated (2 pairs,Forfspnng=0.58 with siblings
the hatching rate of eggs was zero. When the
inbred Fl adults were crossed out, the hatching
rate of eggs was nearly normal (95%, n=500, 5
pairs). The survival oflarvae was not monitored
forthese matings.
2. Ornithopterarichmondia: Slightlylessspec-
tacularbutneverthelesssevereinbreedingeffects
were recorded in O. richmondia (Fig. 4) Hatch-
ing rates of presumed outbred eggs from wild
females were 97% (n=500) and larval survival
was 82% (n=100). Hatching rates of eggs from
HrwGih.gihct2)h.hAhaandtcdihenevbderleoodnpcetodhhenosrotrammoaeflldCayryew.shsTiihldeeaiflcsoruterhstrsheiedianssitlbaalrrivn(gaaset tsoib8li4n%g c(rmoesasens=(F7of4f%sp)r.ineLa=rv0a.l25s)urrvainvgaeldwfarsomlo6w2.
were still in Ihe secondinstar. with only 11% of hatching eggs reaching adul-
thood. In total, 20 adults were reared from 250
OU1BRED eggs. Larval development was retarded, par-
ticularly in the later instars. and developmental
<1/5 100 time ranged from 25 to 52 days (mean 36 days),
compared with a normal time of 27 days for
g
2 i II III IV V outbred larvae. When the progeny ofthese cros-
ses were mated (F ffSpring =-0.25), hatching rates
fc of eggs ranged from 42 to 59% (mean =51%).
>< Larvae hatching all contracted a probable viral
> 100 infection in the fourth instaranddiedbutthismay
F=0.25 not have been a direct effect ofinbreeding.
3. Otherspecies: In otherpapiiionids, inbreed-
ifl
z ing depression as expressed by hatching rates of
UJ eggs from Fl sib-sib matings (Foffsprmg = 0.25)
1 II III IV V wasmostsevereinPapilioaegeus(Hatchingrate
&UJ 70%). Survivorship of hatching larvae was low
(32%). Neitherhatching rates nor larval survival
10 20 30 40 rates in Graphium macleayanum and Chilasa
DEVELOPMENTAL TIME (DAYS) anactuswercsignificantlydifferentfromoutbred
matings.Similarly,by thesamecriteria,therewas
FIG. 3. Larval survival and rate of development by no evidence of inbreeding depression in either
siindsata.rin inbred (F=0.25) and oulbred Cressidacres- Deliasnigrina orDanausaffinis(Table 1). In no
cases were there any significant differences in
mentaltime of21 days in outbred larvae (Fig. 3). size between parents and inbredoffspring.
Intotal,of125adultsbred from4000eggs, seven 4. Tellervozoilus(Fig. 6): There was nodetec-
wereobviouslystuntedbuttheremainderwereof table reduction in hatching rates ofeggs regard-
normal size, robust and healthy. When these Fl less of the degree of inbreeding (n=672). and
adultswerematedwiththeirsiblings(ounrelated larvae experienced high survivorship (n=134).
pairs, Fottspnng = 0.44), hatching rates were very However, adults with an inbreeding coefficient
low,rangingfromzeroto38%(mean=22%),and 0.5 and above characteristically were 10-20%
182 MEMOIRSOFTHEQUEENSLANDMUSEUM
100 • *- •HATCHING RATE
ioo A
- " ''•--. "• _ARVAL SURVIVAL
\ "V
-
EGGS HATCHING a ^ ''•AOl.ILT B|2{
UUJ 50 X
-
fit
-.• fECUNOI1V
LARVAE SURVIVING
25 5 075 10 0.25 0.5 0.75 1.0
COEFFICIENT OF INBREEDING
COEFFICIENT OF INBREEDING
FIG. 4. Effects of increasing levels of inbreeding on FIG. 6. Effects of increasing levels ofinbreeding on
hatching rales of eggs (solid line), and survival of hatching raie of eggs, larval survivorship, size and
hatching larvae 1dashed line) in Ormfhopera rich- fecundity in Teiiervo zoiius. Figures expressed as a
mond'ta.Vertical barsindicate standarddeviations. percentageofoulbred values.
OUTBRED
64-76%. Hatching rates ofeggs laid by the other
100 eight individuals were normal (96-100%) and it
seems most likely that low egg viability was a
I
I II III IV V result ofinbreeding as the individualsconcerned
i wererelatively young with fatbody in good con-
dition,aswasdeterminedbydissectingthemafter
ihcy had laid 50eggs.
>
100 -
DISCUSSION
n F =0 25
Although inbreeding depression has been
UJ
w I II III IV V rLeeppoirdtoepdteirnaca(pNtoirvreis,pop1u9l3a6t;ioWnasldofbavuaerriou&s
EL Sternberg, 1978), effects as severe as those
O 10 20 30 40 reported here have never previously been
DEVELOPMENTAL TIME (DAYS) recorded in butterflies even though extensive
breeding experiments have been conducted on
several papilionid species (Clarke, 1972; Leder-
FIiGns.ta5r.iLnarivnbarledsu(rvFi=v0a.l25a)ndanrdatoeutobfreddevOerlnoiprmheonpttebrya housc & Schriber, 1984). Whether inbreeding
richmondia, depression was low in those species or not
revealed by the breeding programme or was
smaller (based on forewing length) than the simply overlooked or ignored is not clear. In ihe
original wild stock, (Ombrcd = 24, Onuibrcd = 40 only study of an endangered species which has
t=3.8,p<0.001).Correspondingwith this, fecun- addressed the possibility of inbreeding depres-
dity of females also dropped. There are no data sion, Dempster& Hall (1980) found noevidence
onthe normalrelationshipbetweenfecundityand of reduced egg viability in the wild even though
winglength but the fall in fecundity was of an theywerestudyingasmallanddwindlingpopula-
tion.
orderwhich suggested that no additional effects
By contrast, this study indicates that in three
beyond the reduction in size were in operation. species examined, inbreeding depression is
5.Inbreedinginnature: Forallspeciesshowing potentially severe. Notably, these three are all
severe inbreeding depression in the ovum. large papilionids, probably with very open population
numbers of eggs were collected from wild structures, as determined by MRR programmes
females. In almostall cases, the natural hatching (Orr. 1988). Inbreeding depression was not
rate was close to 100% However, in February detected in Graphium macleayanum or Danaus
1987,threeoutofelevenwildfemale (). richmon- qffinis, in which dispersal is more limited. How-
dia laid eggs with hatching rates ranging from vcr,lhere is no clear pattern or susceptibility.
INBREEDiNG DEPRESSION IN BUTTRRFI IBS 183
since in neither was there evidence of strong LITERATURECITED
inbreeding depression in Chilasa anacias or
DeliasrUgrlfflt bothofwhichprobablyhavefair- CLARKE,CA. & SHEPPARD, P.M. 1962.Oils,
ly open population structures. However, as the from double malings in swallowtail butterflies.
continued inbreeding of Tellervo zoilus shows, Entomologist (London)95; 199-203.
ii. t species will sufferdeleteriouseffects ifthe CLAYTON, G.A„ KNIGHT, G.R., MORRIS, J.A. &
inbreedingcoefficient is sufficientlyhigh. ROBERTSON, A. 1957. An experimental check
Although these results cannot validly be ex- on quantitative genetic theory: III. Correlated
responses.Journal ofGenetics55: 171-80.
trapolatedto other species, theysuggestthatcer- COLLINS, M.N. & MORRIS. M.G. 1985. Threatened
tain papilionid groups, especially Troidini, may Swallowtail ButterfliesoftheWorld •The IUCN
be highly susceptible to inbreeding. The IUCN Red Data [took, (IUCN; Gland, Switzerland and
Red DataBookon Papilionidae(Collins& Mor- Cambridge. UK).
ris, 1985)lists4speciesasendangered.23 Specitts DEMPSTER,J.P. & HALL, M.L. 1980. An attempt at
re-establishing the swallowtail butterfly at Wit-k-
av vulnerable and 59 species as indeterminate, en Fen. Ecological Entomology V 327-334
rare or requiring further monitoring. These in- EHRLICH. PR. 1965. The population biology ol Ibe
clude some of the most spectacularand distinc- buUerfl) Ejpftyrfry** tdith&. II.Itiestniciureoftbc
tive species. With 24% of the world fauna Jaspci Ridge colony. Evolution 19; 327-336.
(including O. richmandia) on the list, irnidincs 1983. Genetics and the Extinction of Butter!I\
are particularly well represented. If levels ofin- PopulaSt.ioMns.MIancBSrchyodneewB.a!&d-CTohxoTmCaMs.W,.C(headsm).
tercedingdepressionrecordedin C. cresstdaurO. 'Ucnctics .and Conservation; A reference foi
richmondia were in any way typical ofthe tribe managing wild animal and plant population*.'
then the actual risk to these listed species is <Benjarnin/Cummings: MenloPark,California)
probably even greater than assessed. In par- EHRLICH, P.R., BREEDLOVE, D.E. BRUSSARD,
ticular, captive breeding programmes (see New. P.F. & SHARP, M.A. 1972. Weather and (he
lation "I subalpine populations. Ecology 53.
1991), frequently suggested us part ofa spc 243-247
conservation strategy,may be doomed (see Mar- EHRLICH. PR., MURPHY, D.D.. SINGER, \U
tin. 1975; May, 1980). SHERW C< in. C B„ WHITE, R.R & BROWN.
.
Any conservation programme must ultimately J.L. L9S0. Extinction,tcducuou. stability, and m-
crcase: ihe responses ol checlcerspal butterfly
aim at preserving a self-sustaining gene pool,
which in turn must leadtotheprotection ofmin- p46o;pul1a0t1i-o1n0s5.to the California drought, i ta i
imum areas of habitat. As part of the general FALCONER. D.S. 1981. 'Introduction toQuanii!
programme to conserve papilionid butterflies jfl GcBCtiCS' -r'^ Bd. (Longman; London & New
particular,and probablyallbutterflies,thedegree York).
ofsusceptibilitytoinbreedingofallspecies under FRANKEL.O.H.&SOULE.M.E 1981. Consen
consideration must be assessed. Species which and Evolution*. (Cambridge University Piesa
haveformerlybeenwidelydistributedandwhose Cambridge).
habitathas been reduced and fragmented may be GILBERT, I fl &SINGER,M.C 1973. Dispersal wtf
at risk. Particularly ifthey arc unwilling to gene-flow in a butterfly species. Amcri
flyacI rossunfavourablehabitat,butall species are Naturalist 107; 58-72,
potentially at risk if their population levels GREENWOOD.P.J.&HARVBY,PJi. L97II LnJ M
diminish to low levels for manv venerations inganddispersalintheereallit. Nature27: 52
Orankc) & Sould 1981). LEDERHOUSE. R.C. & SCHRIBER. J.M I'^i
Ecological significanceofapostmatingdecline in
egg viability in the tiger swallowtail. Journal of
ACKNOWLEDGEMENTS Lcpidoptcrist's Society 4 K3-v3.
1 ;
MARTIN. R D (edj. 1975. "Breeding Endangered
SpeciesinCaptivity*.(Academic Press: London)
MAY. R.M. 1980. Inbreeding among ZOOanimals. Na-
1 would like to express my appreciation to my lua- 2X3: 430-431.
paioils, MrandMrsG.H.Orr,forthru assistance NEW, T.R. IWI. 'Butterfly conservation'. (Oxford
in maintainingthe uisecliaryandforhelp in feed- University Press: Melbourne).
ing hundredsofcaterpillars. This work was su|> NORR1S, M.J. 1936. Inbreeding in Ephcstitt kuhnieik
ported partly by a Griffith University research Z. (Leptdopiera: PhyciridacX Journal nfGervtk*
grantand bya UBD conference grant. 32, 179-181.
184 MEMOIRS OFTHEQUEENSLANDMUSEUM
ORR,A.G. 1988.Mateconflictandtheevolutionofthe WALLACE, B. & MADDEN, C. 1965. Studies on
srphrag°is in butterflies. (PhD Thesis, Griffith A™mheTnecdanstNxraftiunrsali,osft9£9:™4E95f-250£9. ^lanogaster.
University: Brisbane.) WOLDA,H. 1978. Fluctuationsinabundanceoftropi-
WALDBAUER,G.P. & STERNBERG,J.G. 1978. In- cal insects. American Naturalist 112: 1017-1045.
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for its avoidance in H„yal.oph,ora cecropia.. tthioenGaenndetdiecpsreosfsiPoonp.ulPapt.io4n4s-^9,6.VoIln.'3E.vo(lUuntiivoenrsaintdy
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