THE RELATIONSHIP BETWEEN EASTERN AND WESTERN POPULATIONS OF THE HEATH RAT, PSEUDOMYS SHORTRIDGEI (RODENTIA MURIDAE)

4 Pages·2003·1.5 MB·English

by  N K Cooper

.
Records of the Western Australian Museum 21; 367-370 (2003). Short communication
The relationship between eastern and western populations of the Heath
Rat, Pseudomys shortridgei (Rodentia: Muridae)
N.K.Cooper',T.Bertozzi',AlexanderBaynes*andR.J.Teale*
*WesternAustralianMuseum,FrancisStreet,Perth,WesternAustralia6000Australia
'EvolutionaryBiologyUnit,SouthAustralianMuseum,NorthTerrace,Adelaide,SouthAustralia5000,Australia
'BIOTAEnvironmentalSciences,186ScarboroughBeachRoad,MountHawthorn,WesternAustralia6016,Australia
The Heath Rat, Pseudomys shortridgei (Thomas, species is classified as Mammals that are
1907),hasawidebutdisjunctrangeacrosssouthern Vulnerable.
Australia, occurring in heaths and shrublands in In a review of the fauna recorded from the
western Victoria, southern South Australia and Fitzgerald Biosphere Reserve, Chapman et al.
Western Australia (Cockbum 1995). The holotype (unpublished) compiled 77 records of this species
ofP. shortridgei (NaturalHistoryMuseum, London, (excluding the nine specimens in the Western
no. 6.8.1.73)wascollectedby G.C. Shortridge on 27 Australian Museum collection). Vegetation of the
Apr1906fromWoyerling,eastofPingelly,Western sites varied, as did soil type. The predominant
Australia (Tate 1951) (see Figure 1). Shortridge vegetation was shrub mallee over either heath or
(1936) recorded the locality as "Woyaline Wells scrub over sedges. Sedges are thought to be an
(sourceoftheAvonRiver)".InWesternAustraliait important dietarycomponent (A. Sanders personal
is presently known only from Fitzgerald River communication 2003). Some individuals were also
National Park, Lake Magenta Reserve, Dragon trapped in shrublands on granites and low forest
Rocks Reserve, Hyden area and Ravensthorpe principally comprising Eucalyptus gardneri
(specimens in the Western Australian Museum ravensthorpensis Soils included loamy sands or
collection) (Figure 1). Two specimens were also sandy loams with a lateritic scree and clayey soils
accessioned into the Western Australian Museum with a stony component. Pseudomys shortridgei has
collectionin1931 fromtheLakeBiddyarea. been recorded from a range of profiles on the
The distribution of Pseudomys shortridgei was landscape including a seasonally damp site low in
much more extensive in southwestern Australia thelandscapeandontop ofarocky ridge, about40
prior to European colonisation (Figure 1), ranging metreshigh. Mostrecordscamefromlongunbumt
from the west coast of Shark Bay to the Great vegetation (between 30 and 70 years) although
Australian Bight. Although this area encompasses Chapman et al. (unpublished) recorded five
six Interim Biogeographic Regionalisation of individuals from two sites in 2000 that had been
Australia regions (IBRA -Thackway and Creswell previously burnt in November 1980. However, the
[1995]), varied habitat types and differing rainfall apparent preference for long unburnt vegetation,
regimes,P. shortridgeiisnotrecordedfromallIBRA which contrasts to easternpopulations, may reflect
regions or habitat types within its former range a general paucity of trapping in recently burnt
(Figure1). suitablehabitatinWesternAustralia.
The rediscovery of living populations of A survey by the Western Australian Museum
Pseudomys shortridgei in Western Australia was alongthecoastoftheGreatAustralian Bightinlate
describedby Baynesetal. (1987), and the species is summer 1984 failed to record Pseudomys shortridgei
currently listed as Declared Threatened Fauna in at Israelite Bay, Toolinna Cove, Eyre Bird
thatState(WildlifeConservationNotice2001). Observatory or Eucla. Both Elliott and pitfall
In eastern Australia, Pseudomys shortridgei now traplineswereemployedatalloftheselocations(R.
occurs almost exclusively in recently burnt, How personal communication 2003). No P.
species-rich, treeless, dry heathlands in shortridgei were trapped during the Nullarbor
southeastern South Australia and southwestern surveysin1984 (Boscaccietal. 1987). Thesesurveys
Victoria(Cockburn 1995). It isdependentonpost- suggest that the extant eastern and western
fire regrowth (Cockburn et al. 1981) and the populations of P. shortridgei arenow disjunct, with
optimumsituationfor the species appears tobe a adistanceofabout1800kmbetweenthem.
mosaic of habitats of differing maturity, subject The eastern and western populations have
todisturbancebyfire (Cockburn1978). According probably been separated for only a few thousand
to the Commonwealth of Australia (1999), the years. Surface remains from mainly coastal caves
N.K.Cooper,T.Bertozzi,A.Baynes,R.J.Teale
Figure1 Map of southern Australia showing IBRA regions with former (open square), modem Western Australian
Museum (pre 1983 open circles, post 1983 closed circles) locality records of Pseudomys shortridgei. The
holotype, (collected 1906) is represented by a star. IBRA regions: AW, Avon Wheatbelt; ESP, Esperance
Plains; EYB, Eyre Yorke Block; GS, Geraldton Sandplains; MAL, Mallee; SWA, Swan Coastal Plain; WAR,
Warren.
(Baynes 1987) show that Pseudomys shortridgei seasonal. All these points suggest that there was a
occurred along the southern coast of Western continuous population of P. shortridgei along the
Australia to at least the eastern end of the Wylie central southern coast of Australia during much if
Scarp, on the western side of the Great Australian notallofthelastglacial.
Bight, and on the Eyre Peninsula to the east, in Several other mammal taxa which also inhabit
immediately pre-European times (Figure 1). The shrub formations and that are currently judged to
species is also a component of the late Holocene be the same species on both sides of the Bight,
fauna from Venus Bay near Ceduna (McDowell shared this original distribution pattern;
1997) and is even sparsely recorded from the grey Parantechinus apicalis, Isoodon obesulus, Potorous
upper deposit in Allen's Cave, which lies near the platyops, Macropus eugenii, Cercartetus concinnus,
eastern extremity of the malleebeltjust east of the Pseudomys occidentalis and Rattus fuscipes (Baynes
border between Western and South Australia. The 1987; distribution maps in Strahan 1995). tdotomys
greyupperdepositisoflateHolocene age (Roberts mitchellii had a similar though continuous
et al. 1996). During the last Pleistocene glacial distributionin immediatelypre-European times. In
(oxygenisotopestages2and3),sea-levelwaslower contrast, neither Pseudomys albocinereus nor P.
andthepresentGreatAustralianBightwasasandy apodemoides has been recorded from either Eyre
coastal plainup to120 kmwide (e.g. Bowler 1982). Peninsula or Kangaroo Island, even as a fossil.
Fossil faunas (which include P. shortridgei) from These two species were synonymised by Ride
bothDevilsLairin southwesternAustralia (Baynes (1970),andhavebeenassumedtobea'siblingpair'
etal. 1976; Balmeetal. 1978) and Seton rockshelter (butseebelow).
onwhatisnowKemgarooIsland (Hopeetal. 1977), FromrecentsurveyworkinWesternAustralia,in
showthatmammalcommunitiesinsoutherncoastal areas where Pseudomys shortridgei is known to be
areas during the last glacial had greater species- extant, few individuals have been trapped. From
richness than those of the Holocene interglacial, 4460 Elliott trap-nights (medium size Elliott traps)
probably because glacial climates were less and 1494 pitfall trap-nights within the Fitzgerald
EastandwestpopulationsofPseudomysshortridgei 369
Biosphere Reserve between 1993 and 2001, just 77 Table2 Distance matrix of uncorrected genetic
captureevents were recorded from 11 sites. This is distances (percentages) of partial
much less than the 708 capture events of the Bush mitochondrial cytochrome b sequences for
Rat, Rattiisfuscipes across 47 sites during the same Pseudomysshortridgei
studies (Chapman et al. unpublished). In Victoria, 1 2 3 4 5 6 7
Happold (1976) and Braithwaite (1977) found that 1ABTC8079
thedensityofanimalsinfavouredareaswassixper 2ABTC79270 0.000 -
hectareand thatnumbersdidnotvarytemporally. 3WAMM26644 0.026 0.026 -
Before there is further work to study the size, 54WWAAMMMM4491297028 00..002266 00..002266 00..000000 -0.000 -
extent and status of the populations of Pseudomys 6WAMM49273 0.026 0.026 0.007 0.007 0.007 -
shortridgei in Western Australia, it is important to 7WAMM52338 0,026 0.026 0.000 0.000 0.000 0.007 -
knowwhetherthewell-studiedeasternpopulations
belong to the same species as the populations in
WesternAustralia.Iftheyaredifferentspecies,then
information on the biology of the eastern and P. apodemoides is 12% for the same sequence.
populations may not be suitable as a basis for However, mitochondrial DNA analyses (Torrance
managementinWesternAustralia.Therehavebeen and Dormellan unpublished observations) suggest
no previously published morphological or that Pseudomys albocinereus and P. apodemoides are
molecular genetic studies to examine if the two not sister taxa. There is minor divergence (0.7%)
populations are indeed the same species. The first between individuals of P. shortridgei in the Lake
step intheevaluationofthetaxonomicstatusofthe Magenta area in Western Australia and no
western and eastern populations has been the divergencebetweenthetwoeasternstatessamples.
molecular genetic analysis of tissues from eastern Takentogether,thedataonhistoricaldistribution,
andwesternspecimens. ecology and genetic divergence suggest recent
Wenucleotidesequencedapproximately300base separation of eastern and western Pseudomys
pairs of the mitochondrial cytochrome b gene by shortridgei populations and support the present
polymerase chain reaction amplification and direct treatment of those populations as a single species.
sequencing using the primers H15149 and L14841 ThelevelofmoleculardivergencebetweenWestern
(Kocher et al. 1989). Specimens used in this study Australian and South Australian and Victorian
are listed in Table 1. An evolutionary tree of the samples is low compared with differences among
alignedsequencesconstructedwith theNeighbour- sibling species of Pseudomys, and furthermore the
Joining algorithm from Kimura 2-parameter reciprocal monophyly of the eastern and western
distances showed that there is a split between the mitochondrial lineages (ifindeed thisstillholds up
WesternAustralianandeasternstatessamples (two withalargernumberofindividualssampled)could
only of the latter) at about 2.6% sequence havearisenquicklyfollowingarapiddiminutionin
divergence on average (Table 2). This level of rangeandconsequentpopulationdeclinefollowing
divergenceislessthanthatseenbetweenspeciesof the last glacialjusta few thousand years ago. That
Pseudomys, for instance distances between species the western and eastern populations appear to
of pebble-mound mice exceed 5.6% uncorrected occupy different habitats may simply reflect the
sequence divergence and the distancebetween the lack of identical habitats in the two widely
east-west 'sibling' species Pseudomys albocinereus separated regions. Itwouldbedesirabletoconfirm
the status ofthe populations with a morphological
study.
Table1 Collection data for specimens used in
molecular analysis. Prefixes for registration
numbers are WAMM - Western Australian ACKNOWLEDGEMENTS
Museum mammal collection; ABTC - The authors thank BHP Billiton Ravensthorpe
Australian Biological Tissue Collection, South
AustralianMuseum. Nickel Operations Pty Ltd for funding the
molecular analysis. Piers Higgs for producing
WesternAustralia Figure 1,John Dell, Steve Dormellan and Ric How
Fitzgerald River National Park, 33°52'08"S, 119°54'12''E, for constructive comments on the manuscript and
W11A8M°5M82'6006"4E,4;WALMakMe41M9a0g8en,taWARMesMe4r9v2e,723-33°3;5'0L0a"kSe, AngelaSanders andAndy Chapman for providing
MagentaReserve,33°28'01"S,118°55'01"E,WAMM52338 trappinginformation.
SouthAustralia
Lower Glenelg River CP, 38°00'00"S, 140°57'00''E, REFERENCES
ABTC79270
Balme, J.M., Merrilees, D. and Porter, J.K. (1978). Late
V6ikctmorWiaPortland,38°20'00"S,141°32'00"E,ABTC8079 Qyeuaartse,rnfarroymmeaxmcmaavaltiroenmsainisn,Dsepvainl'nsinLgaiarb,ouWte3s0te0r0n0
370 N.K.Cooper,T.Bertozzi,A.Baynes,R.J.Teale
Australia. Journal of the Royal Society of Western Happold, M. (1976). Social behaviour of the conilurine
Australia61:33-65. rodents (Muridae) of Australia. Zeitschrift fiir
Baynes, A. (1987). The original mammal fauna of the Tierpsychologie40: 113-82.
Nullarbor and southern peripheral regions: evidence Hope, J.H., Lampert, R.J., Edmondson, E., Smith, M.J.
from skeletal remair\s insuperficial cave deposits. In and Van Tets, G.F. (1977). Late Pleistocene faunal
McKenzie, N.L. and Robinson, A.C., eds. A biological remains from Seton rock shelter. Kangaroo Island,
survey of the Nullarbor region South and Western SouthAustralia.JournalofBiogeography4:363-385.
Australia in 1984. Adelaide: South Australian Kocher, T., Thomas, W., Meyer, A., Edwards, S., Paabo,
Department of Environment and Planning. Pp. 139- S.,Villablanca,F.and Wilson,A. (1989).Dynamicsof
145;400-401. mitochondrial DNA evolution in animals:
Baynes, A., Chapman, A. and Lynam, A.J. (1987). The amplification and sequencing with conserved
rediscovery, after 56 years, of the Heath Rat primers.ProceedingsoftheNationalAcademyofSciences,
Pseudomys shortridgei (Thomas, 1907) (Rodentia: USA86:6196-6200.
Muridae) inWesternAustralia. Recordsofthe Western McDowell, M.C. (1997). Taphonomy and
AusralianMuseum13:319-322. palaeoenvironmentalinterpretationofalateHolocene
Baynes,A.,Merrilees,D.andPorter,J.K.(1976). Mammal deposit from Black's PointSinkhole, Venus Bay,S.A.
remains from the upper levels of a late Pleistocene Proceedings ofthe Linnean Society ofNew South Wales
deposit in Devil's Lair, Western Australia. Journal of 117: 76-95.
theRoyalSocietyofWesternAustralia58:97-126. Ride, W.D.L. (1970). A guide to the native mammals of
Boscacci, L.]., McKenzie, N.L. and Kemper,C.M. (1987). Australia. Oxford UniversityPress, Melbourne. Pp. i-
Mammals. In McKenzie, N.L. and Robinson, A.C., xiv, 1-249.
eds.AbiologicalsurveyoftheNullarborregionSouthand Roberts, R.G., Spooner, N.A., Jones, R., Cane, S., Olley,
WesternAustralia in 1984. Adelaide: South Australian J.M.,Murray,A.S.and Head,M.J. (1996). Preliminary
Department of Environment and Planning. Pp. 103- luminescence dates for archaeological sediments on
138. the Nullarbor Plain, South Australia. Australian
Bowler, J.M. (1982). Aridity in the late Tertiary and ArchaeologyNo.42:7-16.
Quaternary of Australia. In Barker, W.R. and Shortridge, G.C. (1936). Field notes (hitherto
Greenslade,P.J.M.,eds. Evolutionofthefloraandfauna unpublished)onWesternAustralianmammalssouth
ofarid Australia. Adelaide: Peacock Publications. Pp. of the tropic of Capricorn (exclusive of Marsupialia
35-45. and Monotremata), and records of specimens
Braithwaite,R.W.(1977).Preliminaryobservationsonthe collected during the Balston Expeditions (November
activitypatternofRatiuslutreolusandotherVictorian 1904toJune1907). ProceedingsoftheZoologicalSociety
smallmammals. VictorianNaturalist94:216-219. ofLondon1936:743-749.
Chapman, A., Sanders, A., Harold, G. and Teale, R.J. Strahan, R., ed. (1995). The mammals ofAustralia. Reed
(unpublished). Vertebrate fauna of the Fitzgerald Books,Chatswood,N.S.W.Pp. 1-756.
BiosphereReserve. Tate,G.H.H. (1951).ResultsoftheArchboldExpeditions.
Cockburn, A.R. (1978). The distribution of Pseudomys No. 65. The rodents of Australia and New Guinea.
shortridgei (Muridae: Rodentia) and its relevance to Bulletin oftheAmerican Museum ofNaturalHistory97:
that ofother heathland Pseudomys. Australian Wildlife 183-430.
Research5:213-219. Thackway, R. and Creswell, I.D. (1995). An interim
Cockburn, A.R. (1995). Heath Rat Pseudomys shortridgei biogeographicregionalisatonforAustralia:aframeworkfor
(Thomas, 1907). In Strahan, R., ed. The mammals of setting priorities in the national reserves system
Australia. ReedBooks.Pp.617-618. cooperative program. Reserves System Unit. ANCA.
Cockburn, A.R., Braithwaite, R.W. and Lee, A.K. (1981). Canberra.
The responseofthe Heath Rat, Pseudomys shortridgei Thomas,O. (1907).Listoffurthercollectionsofmammals
topyricsuccession: atemporallydynamiclife-history from Westwern Australia, including a series from
strategy.JournalofAnimalEcology50:649-666. Bernier Island, obtained for Mr. W.E. Balston; with
Commonwealth of Australia (1999). Environment field-notes by the collector, Mr. G.C. Shortridge.
ProtectionandBiodiversityConservationAct1999. Proceedings of the Zoological Society of London 1906:
Government of Western Australia (2001). Wildlife 763-777.
Conservation (Specially Protected Fauna) Notice 2001.
GovernmentGazette.Pp.4238^245.
Manuscriptreceived11March2003;accepted00March2003