SPECIES RICHNESSAND ENDEMISM OF BAEINEWASPS (HYMENOPTERA: SCELIONIDAE) IN AUSTRALIA
M. IqbalandA. D. Austin
DepartmentofCrop Protection,Wake Campus, TheUniversity ofAdelaide. P.O. GlenOsmond, SA 5064, Australia
Abstract
Iqbal,M. andAustin,A.D., 1997. Species richnessandendemismofbaeine wasps(Hyme- noptera:Scelionidae) inAustralia. MemoirsoftheMuseumofVictoria 56(2):455-459.
Thespeciesrichnessandlevelofendemicityof baeine scelionid wasps,whichareendo- parasiticonspidereggs,were determinedforfoursitesofurban bushlandinthePerth area andamongfourmore distantlocalitiesacrossthe Australian continent. AmongthePerth sitesthenumberofbaeinespecies variedfrom 14to20,with atotalnumberof 27forthesites
combined. The proportion of speciesshared amongsites was high, 55-71%, but 22% of specieswere only recordedatonesite.Thefour distant locationswhichhaddifferent veg- etation types,viz.Western Australia(Perth),SouthAustralia (MtBarker),and north and south-eastQueensland(SplitRock andMtGlorious), variedinnumberof speciesfrom 20to 31(totalof97species)butwithvirtuallynospeciesincommonamongthem. Theseresults arediscussedinrelationto differencesinhabitatpreference,collectingtechniques, thesize ofthe Australianbaeinefauna,anda possible trophiclevelrelationshipbetweenspiderand baeinespecies richness(i.e.host andparasitoid).
Introduction
Inrecent yearscomprehensivesurveys ofinvert- ebratesusingmultiple trapping techniqueshave shownthat the insectorderHymenopteratobe oneof, ifnotthemost,speciesrichordinal taxa of animals (LaSalle and Gauld, 1992, 1993).
This is particularly obvious from surveys in tropical forests (Askew, 1990;Naumann et al.,
1991; Noyes, 1989a, 1989b) but generally it
applies acrossmost terrestrial habitats (LaSalle andGauld, 1993). Like the other huge orders of insects,theHymenopteracomprisealargenum- ber offunctional groups, including herbivores (exposedleaf-feeders, leafminers, gallformers, seedfeeders,pollenandnectarfeeders,andxylo- phagous species), predators, parasitoids (both ecto- and endoparasitoids), and hyperparasi- toids(seeGauld andBolton, 1988). However,it is onefunctional group, the parasitoids, that is
responsible for the species richnessofthe order.
Parasitoids exploitarthropodsas a food source for theirdeveloping larvaeand they have radi- ated into this almost unlimited resource, pro- ducing a phenomenal numberofspecies, prob-
ably severalhundred thousandworld-wide. It is thisbiology, associatedwiththeirhighdegree of host specificity, that has lent them to being utilisedas biological control agents ofinsects.
Onegroupof small scelionid parasitoids, the Baeini (< 2 mm in length), endoparasitically attack the eggs ofspiders (Austin, 1985), and
they are postulated to be important regulating agents of spider populations (Austin, 1984a).
Giventhatspiders arebecoming oneofthe pre- ferredgroups asecological indicators, to assess suchaspects as general species richness,habitat disturbance, faunal community structure and biogeographic relationships (see Churchill, 1997; Harvey et al., 1997; Main, 1997; York, 1997), a comparable knowledge of the distri-
bution patterns, richness and levels ofendem- ism of baeine wasps mayallow suchecological questions to be examined and compared betweentrophiclevels,i.e.between spidersand
their parasitoids. In this respect, the current studydocumentsdistribution patternsandcom-
position among baeine wasps for a number of
sites within the Perth urban area, and among
four distantlocalitiesacross the Australiancon- tinent which vary substantially in habitat type.
Methods
Four sites around the Perth urban area were selected to assess baeine species richness, and they represented areas ofremnant native veg- etation which were used in a more extensive study by Harvey et al. (1997). These were located at Bold Park, Perth Airport, Tuart Hill
andtheTalbotRoadReserve,andthey generally comprise open Eucalyptus-Banksia woodland.
Thecollectingmethodatthesesiteswasthreeor
455
https://doi.org/10.24199/j.mmv.1997.56.38
456 M. IQBALAND A.D.AUSTIN
fourgrids, each of102-1 plastic ice-creamcon- tainers charged with concentrated (95%) ethy- lene glycol and run for 12 months. It was not possible to use other collecting techniques aroundPerth, suchas Malaisetraps,because of the high risk of vandalism (see Harvey et al.,
1997 for more detailed description ofthe sites
and collecting method). Specimens were removedfromtrapsabout everysixweeks; they were then washed, transferred to 70% ethanol and sorted under a stereomicroscope, point-
mountedand labelled.
Taxonomically, baeine scelionids are well-
knownat the generic level (Gallowayand Aus-
tin, 1984). Further, sufficient information is
availableatthe speciesleveltoaccurately separ- ate morphospecies (e.g. Austin, 1981, 1984b, 1986, 1995), even though the majority are undescribed. Charactersfoundtobeparticularly importantinseparating species include therela- tive size and shape ofbody segments and ter- gites, surface sculpturing, length and shape of antennal segments, presenceandsizeofameta- somal horn, development of wings, length of veins, wing pilosity, and colour pattern.
To assess regional (continent wide) levels of baeine richness and endemism, the data from the four Perth sites was pooled and compared withthat fromthreeadditionallocalities.These datawerecollectedinan aposteriorifashion,i.e.
they were accessed from existing material in
museum collections (primarily the Australian National Insect Collection, Canberra and Department of Primary Industries, Brisbane).
Thesesiteswereselectedbecausetheyhavebeen extensivelycollected,they areverydistantfrom each other, and they represent very different habitat types. They are Mt Barker summit, 30km ESE of Adelaide, SA, comprising dis- turbed open mallee woodland; Mt Glorious summit, a well-known rainforest site in SE Queensland;andSplitRock, north Queensland, comprising tropical savannah. The collecting methods andduration of trappingvariedamong
thefourlocations as indicated inTable2. How-
ever, the techniques employed were chosen to optimisethewaspcatchateachlocation.AMal-
aise trap was used at Mt Barker, Mt Glorious and SplitRock,a flight-intercepttrap(FIT)was deployed at the latter two locations, while sweep-nettingwasonlyundertakenatMtGlori- ous (N.B.thelattertechniquedid notyieldany additionalspecies). Further, the sixmonth dur- ationof trappingatMtBarkerisprobably equiv- alent to the 12 months at the other locations, given that previous experience has shown that
baeinewaspsarehardlyevercollected theredur- ing the winter months and, when specimens havebeentaken,theyhaverepresentedcommon
summer-activespecies.Asfor thepitfalltrapsat Perth,theFITatSplitRockused ethyleneglycol asa preservative, while the Malaisetraps used
70%ethanol.
Results and discussion
Thegeneraandnumberof baeinespecies forthe foursitesaroundPertharegiveninTable I.The numberof genera varied little, from fiveto six,
but the composition was different among sites,
withnositehavingallsevengenera.Thenumber ofspecies variedfrom 14 atTuart Hill to 20at Bold Park, with a total of27 species recorded across all sites. Ofthese, 14 species (52%) are either wingless or micropterous, including all
females ofBaeus Haliday, Mirobaeoides Dodd and MirobaeusDodd,andthreespeciesofIdris Foerster (datanotshown), whilethemajorityof Idris and Ceratobaeus Ashmead, and all
Odontacolus Kieffer and Hickmanella Austin arefullywinged. Theoverlapinspeciescompo-
sitionamongsitesisshowninFigure 1. Itvaried from 55%(Bold ParkversusTuartHill) to71%
(Tuart Hill versus Talbot Road and Perth Air- port),althoughsixspecies(22%) wererestricted to just one site. However, more extensive col- lecting at the foursites islikely to increasethe numberof shared species.
TuartHill
14
TalbotRoad
10 Reserve
16
i
1 i
11
r
A
V k 'it12BoldPnrlf -« », Perth Airnort
2
12
11
Figure 1. Numberof baeinescelionid speciesshared between the foursites ofremnant vegetation in the Perth area.
Table 1: Number ofspecies ofbaeine scelionid waspsat four sites in the Perth urban area.
Sites
Genus Tuart Hill Talbot Rd Reserve Bold Park Perth Airport
Baeus 2 2 2 2
Ceratobaeus — 2 3 3
Hickmanella 1 1 1 —
Idris 4 5 7 4
Mirobaeoides 6 6 6 5
Mirobaeus 1 — — 1
Odontacolus — — 1 2
Total 14 16 20 17
Table 2: Numberofspecies of baeinescelionid waspsat fourlocalities in Australia
Locality Perth, WA
Pitfall
Mt Barker, SA Mt Glorious, SEQld Split Rock, N Qld
Traptype Maliase Maliase, FIT,
Sweeping
Maliase, FIT
Duration 12 months 6 months Sporadic, long term 12 months
Baeus Ceratobaeus Hickmanella
Idris
Mirobaeoides Mirobaeus Odontacolus
2 4 2 8 8
1
2
1
11
8
2 15
12
1
1
10
11
1
1
Total 27 20 31 23
Dataforthe fourPerthsiteswaspooledandis
presented along withthe three distantlocalities,
MtBarker,MtGloriousandSplitRockinTable
2. Because of differences in collecting tech- niques, number oftraps, and duration ofsam- pling the data are only generally comparable.
However, they are most similar for the three eastern localities, all ofwhich approximate 12 monthscollectingand used similartraps.
The number of genera varied more signifi- cantly than among the four Perth sites, from
sevenatPerth(combined)to threeatMtBarker,
while the numberofspecies varied from 20 at
MtBarkerto 31 atMtGlorious (Table2),witha total of 97 species. Further, the speciescompo-
sitionvariedsubstantiallyamong Perthandthe other three localities in the number of apte-
rous/micropterous forms, from 4-5% (one species) at Mt Barker and Split Rock to 26%
(eightspecies)atMt Gloriousand52%at Perth (see above). These differences are primarily reflected in the numbersof Mirobaeoides spp., allofwhichhave apterousfemales.Whereasthe four sites at Perth had eight species, the other three locationshad oneornone.Therichnessof this genusaround Perth is particularlysurpris- ing,giventhata recent revisionof Mirobaeoides forthewhole continent(Austin 1986) recorded only 12 species, most ofwhich are apparently restricted to the eastern seaboard. Like Perth, the other three localities were dominated by CeratobaeusandIdrisspp.but evenmoreso,i.e.
87%ormoreofthetotal species.Thereasonsfor the above differences among locations are not
458 M. IQBALAND A.D.AUSTIN
clear.Theycould bearifactualandthe resultof
different collecting techniques, or they could
reflect real differences in habitat preferences and levels of endemicity among genera and
species. Quite probably, both factors are involved.Asmight beexpected, thelocalitywith the highestproportion of apterous/micropterous species (Perth) was the one where only pitfall trapswereused, atechniquethatislikelytoopti-
mise the catch of ground-inhabiting, reduced- winged forms. However, flight interception traps also catch ground-living species (Austin pers.observ.)and inthetwolocations, MtGlo- rious and Split Rock, where these traps were employed, the proportion of apterous/
micropterous forms was surprisingly much
lower.
Where the number ofspecies shared among
the Perth sites exceeded 50%, that among the four distant locations was very low. Only two species were shared between Perth and Mt
Barker,andafurthertwo betweenPerthandMt
Glorious(i.e. 7%),whileno specieswere shared
among Mt Barker, Mt Glorious and Split Rock.
Although the species recorded at the four localities undoubtedly occur more widely, the fact that thereisverylittleoverlap in thefauna
among localities indicates that many baeines have restricted distributions, e.g. no species in
commonbetweenthe easternsites(MtGlorious andSplitRock).Thesedataraisethequestion—
what is the true size ofthe Australian baeine fauna? Recent surveysbyus,based on examin- ationofAustralianandoverseascollections,and extensivefieldworkoverthelast 15yearsby one ofus(ADA) showthat the numberof described species conservatively represents only about one-sixth ofthe estimated total number(Table
3). Already, about 150specieseach ofWraand Ceratobaeus have been recognised. This esti-
mate is based on the number ofspecies ident- ified in collections, increased by a factor of approximately 20-25% to account for as yet unrecorded new species. Indeed, new species have been collected within the last 12 months from relatively well-collected habitats close to major Australian cities. Further, the level of endemism indicated in this study among geo- graphically close and distant localities strongly suggest that areasofthecontinentthathavenot been collected or only poorly surveyed (for
which there aremany)arelikely to yield many newspecies. Therefore, our estimated increase of20-25%overand abovethe currentlyknown
species,may be fartoo conservative.
Table 3. Recorded and estimated numberof Australian baeine species
Genus Described Estimated
species species
Baeus 3 20
Ceratobaeus 31 200
Hickmanella 4 10
Idris 27 200
Mirobaeoides 15 35
Mirobaeus 2 15
Odontacolus 3 20
Total 85 500
Whether or not the species richness of baeine waspsisrelatedto thatoftheirhost spidersisyet to be determined. However, the present study providesthe background and means forthis to be undertaken, at least at the foururban bush- landsitesaroundPerth(seeHarveyetal., 1996).
Ifbaeinerichnessissorelated,then thesesmall waspsmayprove an important adjunctto stud- iesonthe diversity ofspiders,andtoexamining species richness between trophically linked groups, viz. invertebrate hosts and their insect parasitoids. Oneaspectofthe biologyof baeine waspsthat isyet tobeinvestigatedand whichis likelytoimpinge onboth ofthesequestions(the sizeofthe continent'sfaunaand whetherbaeine andhost species richness are linked)istheirlevel ofhost specificity. Preliminary studies on four speciesof baeinesindicate thattheyarespecific to at least a single spider genus, and possibly
more narrowly to a species-group (Austin, 1984a).Ifthisisthecase,thenthetotalnumber of baeine species will be dictated, to a large degree, bythenumberof genera/species-groups they have evolved to exploit. Clearly, not all
spiders are attacked by baeine wasps. For instance, they are not recorded from mygalo- morpheggs,whereastheyareknownfrommany araneomorph species (Austin, 1985). However,
for the great majority of araneomorphs such information isjustnot available.
Acknowledgements
WewishtothankJulianncWaldockfor sorting wasps from the Perth traps, Ian Naumannand Jo Cardale for loan of material from the AustralianNationalInsect Collection,andMark Harvey and Sally Collinsfor commentson the manuscript.
References
Askew, R.R., 1990. Species diversities ofHymenop-
tera taxa in Sulawesi. Pp. 255-260 in: Knight, W.J. and Holloway, J.D. (eds). Insects and the rainforests of south-east Asia (Wallacea). The Royal Entomological Society: London. 343 pp.
Austin,A.D., 1981.Hickmanetta,anewgenus ofSce- lionidae from Australia (Hymenoptera: Procto- trupoidea).Journal ofthe AustralianEntomologi- calSociety20: 303-308.
Austin,A.D., 1984a.Thefecundity,developmentand host relationshipof Ceratobaeusspp.(Hymenop-
tera: Scelionidae), parasites of spider eggs.
EcologicalEntomology9: 125-138.
Austin,A.D., 1984b.SpeciesofCeratobaeusAshmtad (Hymenoptera: Scelionidae) from south-eastern Australia. Transactions ofthe Royal Society of SouthAustralia 108: 21-34.
Austin,A.D., 1985.Thefunctionofspider egg sacsin relation toparasitoidsandpredators,withspecial reference to the Australian fauna. Journal of Natural History 19: 359-376.
Austin,A.D., 1986.Ataxonomicrevisionofthegenus MirobaeoidesDodd(Hymenoptera:Scelionidae).
AustralianJournalofZoology34: 315-337.
Austin, A.D., 1995. New species ofscelionid wasps (Hymenoptera: Scelionidae: Baeini) from West- ern Australia,parasiticonspidereggs.Records of the WesternAustralian Museum Supplement 52:
253-263.
Churchill, T.B., 1997. Spiders as indicator taxa: an overviewforAustralia.MemoirsoftheMuseumof Victoria 56: 331-337.
Galloway,I.D.andAustin, A.D., 1984.Revision ofthe Scelioninae(Hymenoptera: Scelionidae) in Aus-
tralia.AustralianJournal of Zoology Supplemen- tarySeriesNo. 99: 1-138.
Gauld, I. and Bolton, B., 1988. The Hymenoptera.
British Museum (Natural History), Londonand Oxford University Press: Oxford,332 pp.
Harvey,M.S.,Waldock,J.M.,How,R.A.Dell,J.,and Kostas, E. 1997. Biodiversity and biogeographic relationshipsofselected invertebratesfrom urban bushland remnants, Perth, Western Australia-
Memoirs ofthe Museum of Victoria 56: 275- 280.
LaSalle,J.andGauld,I.D., 1992.ParasiticHymenop-
tera and the biodiversity crisis. (4th European WorkshoponInsect Parasitoids). Redia64:315- 334.
LaSalle,J. andGauld,I.D., (eds) 1993.Hymenoptera andbiodiversity.CABInternational: Wallingford.
348pp.
Main, B.Y., 1997. Tropical rainforest spidersin the Australiandesert:the ironyof an adaptivelegacy.
Memoirs ofthe Museum of Victoria 56: 339- 347.
Naumann,I.D.,Weir, T.A.and Edwards,E.D., 1991.
InsectsofKimbley rainforests. Pp. 299-332 in:
McKenzie, N.L., Johnston, R.B. and Kendrich, P.G.(eds),Kimbleyrainforests.Surrey Bettyand Sons:Chipping Norton. 490pp.
Noyes,J.S., 1989a.,ThediversityofHymenopterain the tropics withspecial reference to Parasiticain Sulawesi.EcologicalEntomology 14: 197-207.
Noyes, J.S., 1989b. A study of five methods of sampling Hymenoptera (Insecta) in a tropical rainforest,withspecialreferencetotheParasitica.
Journal of NaturalHistory23: 285-298.
York,A., 1996.Assessing ecologicalsustainabilityand biodiversity conservation—theuseofperform- anceindicatorsinforestmanagement. Memoirsof theMuseumofVictoria 56(2).
