Faunal survey. I. The distribution of aquatic gastropods of the New England Tablelands

2004·2.2 MB·English

by  Maree Koch

FAUNALSURVEY. THE DISTRIBUTION OF AQUATIC GASTROPODS OF THE
1.
NEWENGLAND TABLELANDS
MAREE KOCH
Koch, M. 2004 06 30. Faunal survey. 1. Thedistributionofaquatic gastropodsoftheNew
¥.ng\Q.ndTdi}cAQ\2ind^.MemoirsoftheQueenslandMuseum49(1)\ 653-658. Brisbane. ISSN
0079-8835.
This survey ofthe distribution and abundance ofaquatic gastropods ofthe New England
Tablelands updates the informationpublished by Simpson& Stanisic (1986) forthe same
region.Allspeciesshowedmarkedreduction inbothdistributional rangesandabundances
with no specimens ofForsancylus enigma found. Some seasonal loss ofaquatic habitats
withintheTablelandsoccursannually,howevertheseverityofthedrought(January2002to
present) has caused more extensive habitat loss and consequent loss of individual
populationsofaquaticsnails. Itishypothesisedthatacombinationofhigherslocknumbers
andincreasedclearingofvegetationmaybecontributingtothereductionofaquaticsnailsas
waterlevelsareloweredandvertebratefaecespollutehabitats. Aquaticgastropods, New
England Tablelands, distribution, survey,pollution, habitatdegradation.
Maree Koch, School ofBiological, Biomedical & MolecularSciences, University ofNew
England, Armidale2351, Australia (e-mail:[email protected]); 1 March 2003.
This survey ofaquatic gastropods oftheNew area, with each cell representing a ‘quarter-celT
England Tablelands, New South Wales, was intheABIGSsystem,eachofthesecellscovering
conductedbetweenFebruary2000 andFebruary 76km^. Shadingofthatcell indicatespresenceof
2003andparallelsacomponentoftheSimpson& a species in any part of a quarter-cell. Many
Stanisic(1986)surveyofthesameregion(Fig.1). quarter-cellswerevisitedatleasttwicewithinthe
The regionpossesses adiversity ofhabitats that research period, withafinal surveyofthe region
reflect the variations in both topography and completedbetweenNovember2002andFebruary
climate experienced there. Temperatewoodland 2003. Multiple visits to many sites at different
partially cleared foragricultural use is abundant seasons within the study period ensured that the
alongthecentralhighlands,mergingwithundisturbed possibility of seasonal occurrences of some
temperaterainforests andwetsclerophyll forests species ofgastropods was covered adequately.
alongtheeasternescarpment.Thewesternslopes Collections were made under logs and stones
blend out into the alluvial plains westofInverell and amongstvegetationwithin dams, creeks and
and Barraba. Habitats are vulnerable and their rivers, swamps, and backwaters using a dip net.
existence is governed by climatic fluctuations Close examination of substrates and the stalks
within four distinct annual seasons correlated and leaves of aquatic vegetation was done by
with the large altitudinal range of 1000-1500 hand.Gridreferencesfromtheoriginalcollection
metres across theregion (Walker, 1977). records (supplied by R. Simpson, 2000) were
The aims ofthe survey were to establish the used to ensure that all sites visited during the
current distributional ranges of the aquatic original survey(Simpson& Stanisic, 1986)were
gastropods in accordance withthe initial survey again checked during this survey period.
ofthe New England Tablelands as described by Collections were also made at locations other
Simpson & Stanisic (1986) and Heatwole & than those noted by Simpson Sc Stanisic (1986).
Simpson (1986); and to identify the trematode Identification ofall specieswas confirmedusing
2sp0e0c3iae,s2i0n0f3ecbt)i.ngTetrhreessetraiaqluagtaisctmroolploudsscwse(rKeocnho,t pthoedskeoyfttohethNeetwerrEensgtrliaalndanrdegifornesihnwaStiemrpgsaosntro&-
includedinthe currentsurvey. bStyaniSsmiict(h19&86),Kearnsdhtahwen(o1n9-7m9a)r.inAenmyollduousbctkfeuyl
METHODS specimenswereexaminedbyProfessorR.Simpson.
The Australian Biogeographical Integrated RESULTS
Grid System (ABIGS) was used to map all
species, in accordance with Brook (1977) and The basic features ofshell formation and size
Simpson&Stanisic(1986).Agridof5’longitude ofeachgastropodspeciessurveyedareillustrated
by5’latitudewassuperimposedacrossthesurvey in Fig. 2. Without exception, all species
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654 MEMOIRS OF THE QUEENSLAND MUSEUM
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1 FIG. 2. Aquatic snail species ofthe survey area. A,
FIG. I. ABIGS system grid superimposed over the Gabbia vertiginosa; B, Plotiopsis halonnensis\ C,
NewEnglandregionwiththesurveyedareaenclosed Austmpeplealessom\D,Austropepleatomentose;E,
by the solid dots. (AS, Ashford; A, Armidale; B, Glyptophysa sp.; F, Isidorella sp.; G, Gyraulus
Barraba; E, Ebor; G, Glen Innes; I, Invcrell; N, metaunis; H, Pygmanisuspelorius\ I, Physa sp.; J,
Nundle; TA, Tamworth; T, Tenterfield; W, Walcha) Forsancylusenigma. Scalebars: A-D=5mm;E-F=
(AfterSimpson& Stanisic, 1986). 4mm; G-J=2mm. (Source: M. Koch).
demonstrated reduced distribution, with no to dry out from June 2002 onwards. Creeks and
specimens of Forsancylus enigma being riversthatstillcontainedwaterbyFebruary2003
collected (Figs 3-12). AtDangars Lagoon 10km were reduced in both size and volume offlow.
SE ofUralla, large numbers ofdeadPhysa were Figure 13portraysthereductionofrainfallacross
collected on 2 occasions during 2000. No live theentireregioninpastyearsascomparedtothe
snailswere found atthis locationthroughoutthe mean annual rainfall calculated for the area
surveyperiod. betweentheyears 1857to 1997bytheBureauof
Every species also demonstrated reduced Meteorology Australia. For the 36 months Jan-
abundance compared with the descriptions of uary2000 to December2002, the surveyregion
populations by Simpson & Stanisic (1986). An registered a departure from and below the Long
exception lo this was one population ofGabbia Term Average (LTA) annual rainfall value of
veriiginosaatSaumarezRoadswamp(5kmSSW 500mm forthe western and central sections and
of Armidale) where many hundreds were 1000mm for the eastern escarpments (BMA,
observedateverycollection up to March 2002. 2003). The LTA is calculated based on the
currentinternational standardthirtyyearaverage
TheBureauofMeteorologyAustralia(BMA), annual rainfall for the area from 1961 to 1990
on8thOctober2002,formallydeclaredtheentire (BMA, 2003). The average annual evaporation
NewEnglandTablelandstobeinthetenthmonth ratefortheTablelandsbetweenJanuary2000and
ofthe most profound droughtto be experienced December 2002, at 1232mm, was 15mm higher
inrecordedhistory.Atthetimeofpublication,the than the LTA (BMA, 2003). Weather patterns
drought was still continuing across the region, indicate a continuance ofdry conditions to the
with some rainfall between February and April springof2003.
2003 providing surface water. As a direct
consequence of loss of surface water and DISCUSSION
increaseddrawingonsubterranean-fedboresand
springs, swamp backwaters, roadside culverts Seasonal loss ofaquatic habitats is a normal
andmostdrainsandshallowwatercoursesbegan occurrenceonthe Tablelands as theheavy frosts
AQUATIC GASTROPODS OF THENEW ENGLAND 655
and lower rainfall of winter co-
incide causing either reduction or
completeremovalofmanyshallow
and vulnerable environments.
Collections at sites during all
seasons throughout the survey
period ensured that such environ-
mentalfactorshadminimalimpact
on distributional patterns. The
combined effects oflowerrainfall
andhigherevaporationratesacross
the region leading into the current
droughthavecausedfurtherlossof
habitats. Such harsh conditions can
explainreducedspeciesdistribution
fromFebruary2000 tothepresent
time. What factors could be re- FIG. 3. Distribution ofGabbia vertiginosa. A, 1986 survey; B, current
sponsibleforsuchmarkedreductions distribution.
in ranges between the first survey
in 1986 and 2000? The aspect of
humanerrormustbeconsideredto
some extent as even the most
experienced and diligent collector
canmissaspecimen. Ibelievethis
tohave hadaminorimpact onthe
surveyresults.
The majority of wetlands are
either surrounded by, or situated
on,pastoral andagricultural leases,
asaremostofthecreeks,damsand
swamps within the survey region.
Theuse ofsuperphosphates on im-
provedpasturesandinsecticideson
cropsinpaddocksborderingaquatic
habitats impact on the aquatic
faunabybringingaboutchangesin FIG. 4. Distribution of Plotiopsis balotinensis. A, 1986 survey; B,
water quality as these chemicals currentdistribution.
leachintothewatersystems(Ridge,
1995 in Ponder, 1997; Michaelis,
1984),Highlevelsoflandclearing
and disturbance of country im-
mediately surrounding aquatic
habitatscanalsoleadtosiltationof
microhabitats through topsoil
erosion(Ponder, 1997).
Increasedstocklevelswithinthe
New England in response to the
good seasons of the 1990’s have
impacted on the banks and sub-
strates ofdams and water courses
which are largely unfenced
(McKeon et al, 2000; pers. obs.).
Higher stock numbers cause an
increased draw on water supplies FIG 5. DistributionofAustropeplealessoni. A, 1986survey;B,current
and significant organic matter distribution.
being introduced via vertebrate
MEMOIRS OF THE QUEENSLAND MUSEUM
656
faeces, which inturnaffects water
quality by raising ammonium
levels (Campbell & Doeg, 1989;
Ponder, 1997). Once ammonium
concentrationsincreaseto5mg/I or
higherin standingorslow-flowing
water, habitat conditions become
toxic to invertebrate life (Roman-
owski, 1994). The tendency of
regional pastoralists to retain high
stock numbers during drought or
dry seasons leads to further
degradation of habitats that are
already struggling for survival
(McKeon etal,2000).
basEsetsaobluinsdhirnegspthoensdeastatoonthwehiacbohvteo FIG. 6. Distribution ofAustropeplea tomentosa. A, 1986 survey; B,
cuiTentdistribution.
hypotheses isbeyond the scope of
the present study and requires a
statistically designed sur\'ey over
time to detennine ifthere is areal
decrease in species populations
anddistributionalranges.Compar-
ing the results ofthe two surveys
leaves no validity for conclusions
onpopulationincreaseordecrease
to be correctly drawn. It is a
situation deserving considerable
concern, howover. Due to their
limited abilities to disperse, many
of our aquatic snails have very
narrow distribution ranges and
some ofthe laxa present in New'
South Wales are endemic to this
state(Ponder, 1997).Ifspeciesdis- FIG. 7. Distribution of Glyptophysa. A, 1986 survey B, current
tributional ranges and abundances
distribution.
havereducedtotheextentindicated
by the current survey in two
decades, what effects wdll the
current drought and agricultural
practices have upon already
vulnerablepopulations?Dowerisk
losing some aquatic gastropods
fromtheNewEnglandTablelands
permanently? Have some, such as
F. enigma, alreadybeen lost?
ACKNOWLEDGEMENTS
IamgratefultoMaryNotestine,
andKlausRohdeforreviewofthe
manuscript and to Rod Simpson
for review, his original survey FIG.8.Distributionoilsidorella.A, 1986survey;B,currentdistribution.
recordsandconsultationsonspecies
identifications.
AQUATIC GASTROPODS OF THENEW ENGLAND 657
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658 MEMOIRS OF THE QUEENSLAND MUSEUM
FIG. 12. Distribution ofForsancylus enigma sp. A, ^ Western BYeCaerntsral HEastern
1986 survey. This species was not found in the
currentsurvey.
FIG.13. Annual rainfall in millimetres for the three
geographical divisions within the survey region
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annualrainfallfortheregionrecordedbetween 1857
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