Causes of rarity in Abutilon oxycarpum and Hibiscus brachysiphonius (Malvaceae) on the River Murray floodplain, south-eastern Australia

4 Pages·2000·1.2 MB·English

by  R F Parsons

Transactions ofthe RoyalSociety vf$. Aust. (2000). I24(1 1,41-44.
BRIEF COMMUNICATION
CAUSES OF RARITY IN ABUTILON OXYCARPUM ANDHIBISCUSBRACHYSIPHONWS
(MALVACEAE) ON THE RIVER MURRAY FLOODPLAIN, SOUTH-EASTERN AUSTRALIA
A central problem in deciding conservation priorities tor least annually in summer-autumn between 1983 and 1095
plant species in arid and semi-arid areas is thai some and again between 1997 and 1999 (Table 1). Areas ofthe
species appear briefly toI owing particular environmental same habitat in nearby Kings Billabong Wildlife Reserve.
triggersandthendisappearforyearsuntil thetriggerrecurs. Lambert Islandandelsewhereweresearchedintensively for
Such transient species' arc often listed as rare but are not the two taxa without success. Voucher specimens arc-
necessarilythreatenedaslungasthenaturalcyclecontinues lodged at MEL.
Without interference. So far, work on such species in semi- TheplantdatarecordedinTable I refct toAhutiloti plants
aridAustralia hasbeenconcentratedon post-firepioneers' : less than one year old and to resprouts from perennial
.
However, many transient species are triggered by rootstocks ofHibiscus, Rainfall data are from Red Cliffs.
infrequent rainfall events . Because their ecology and lessthan 10 km away.
conservation are poorly understood, here we use long-term The first stands of both taxa seen (at site I) were in an
data from 19S3 till 1999 to explore the issues involved, area where trees had been felled and soil disturbed by
includingcausesof rarityandthe amount ofrainfall needed
to biggergermination ami growth.
Abutilon oxycarpum (F. Muell.) K Muell. ex Benlh. var.
inalvacjuHiini Benth. (Malvaceae) (Fig. 1) is a herb which
mayreachKcmandwhich behavesasanannual inVictoria,
Data are also presented lor Hibiscus brachysiphonius K
Muell. (Malvaceae), a subshruh to 15 cm high which
resprouls from a perennial rootstock. Both species have
their main growth period following rain in the warmer J
*v&&
months ofthe year, in ourarea principally from November
7
until April. Both taxa occur in all mainland states and al
leastas farnorth as 2(1° S'.
AbutHon oxycarpum und //, brachysiphonius were
unknown in Victoria until 1.983 when they were recorded in
close proximity at Bottle Bend near Red Cliffs, Vie.
(foBlrloowwnieng1392Kbm;mFigo.f2r)a.inT.hFiosrbwoatsfiintatxhae,ftihrestViwceteokrioafnMstaarncdhs
are widely disjunct from those elsewhere in Australia and
represent theirsouthern limit''. Neithertaxon is threatened
in Auslraba and frequencies greater than 50% have been
recorded for them in some central Queensland coninv
V
unilies'. However, in Victoria, A. oxycarpum is rated 3
vulnerable and H- hrachvsiphonius endangered". They will
be referred to as Abulilou and Hibiscus throughout this Fig. I. Abutilon oxycarpum 5 cm across at Bottle Bend
paper. Reserve, showing flowerand fruit.
TheknownVictorian rangeofAbutilonandHibiscus is in
an atea less than three km across on grey crackingclays of
the RiverMurray floodplainwithin0.6 kmofthe rivernear
Bottle Bend (big. 2). Abutilon and Hibiscus occur together
al sites 1 and 2 and Abutilon occurs at sites 3 and4. Site 4
is a depression dominated by scattered shrubs of
Mttchlcnbcckia florulcuttt Meisn. (Tangled Lignum); all
othersites containEucalyptuslari>iflorens K Muell. (Black
Box) woodland with a sparse undcrstorey of occasional
chenopods and Zy^opliyllum spp,
The climate is semi-arid, with a mean annual rainfall of
290 mm at Red Cliffs, the wettest months being from May
to October. The rainfall is highly variable, especially in
summer when rain usually occurs as heavy downpours
during thunderstorms. Summers are hot and winters mild,
with frostsoccurring. Fig. 2. Location of Bottle Bend Reserve, showing the only
Site 2 was inspected inJanuary 1991 (12 plants) and site four sites where Abutilon oxycarpum has been seen in
3 in January 19&4 (4 plants). No further inspections were Victoria. Sites I and 2 also carry stands of Hibiscus
made due to track closures. Other sites were inspected at brachysiphonius.
T\hi i F Mmliiiy mttifull totals tmitt}, \tt>tiijhnut rainfall vfifsttthw andmimhcrs<>\'Abullion ami Hibiscus*// fit*
MtHhtrrx I uitil4. Brittle BendResent*farNovembertoApril fS$2-J999i
Rainfall (mm) Plant number-,
Ycai Dec Lin Ivh Mir Ape Majori.mil.ill Ahutilon Almtilttn llthiuus Noleson
episodes Site I Site 1 Nile I Site 4
|$S2r83 I 4X 32mm,2-7 Mai so 311 X
I9S3-&4 14 28 mm, 1-3 Jan 100 47 13
l984-«5 .1 None ft
I985-K6 35 26 mm,6 Nov; (1 \ 5
24mm. Dec
I98&-H7 43 L4 21 mm. S Dei- (] I)
1%7-KS 12 No fallsabove In mm o
!
until Apr(23 mmi
1988-89 27 74 37 mm. 14 Mur present present 10
1989-90 is H 26 rum.4-6 Nov: n
26 mm.21-23Apr
l9l>n-o| 32 mm. 7 Jan: present 2011+ Plead,then
39 mm, 24Jan dense Eleinlutris
3 26 mm. 26 Nov Dense F.lr<>tlmris
roo2 ,j* 94 Falls ofmore than t) present Flood, then
30 mm in Nov. dense Etetjckarix
Dee & Jan
1993-94 95 2&9 mm, 22 Dec: ft* () present Dense
mm. I ! Feb: Eltochttrin
27mm. 14 Feb
1994-95 IS II 54 20 IK 19 mm.6Jan: (1 present Dense
Himm. lbJan: EktM'htiris
16 mm, 30Jan
%
1995 Nodata
1.996-$? Nodata
I997-9N 31 9 37 26 47 No fallsabove 17 mm t) present
1998 09 1.9 3 17 38 17 5 29 mm. 12 Feb present present present
The Ahtttihmpar! ofSite I Hooded briefly in November I99Z resulting in adense Ctilarisstand in 1993-94.
tractor to lay n telephone cable, suggesting pioneer-type Ahutiitoi had (lowersand fruit in s weeks and mature seed
behaviour as in some oilier Malvaceae'. However, all in 75weeksdespite littleextrarain- Plantsonly4cm high
aib^cqueiu stands found have been in intact vegetation canproduceseed. Most fllhixms plants were partly grazed
lacking soil disturbance. off, but flowerbuds were produced by 2 weeks.
When observations started, the area was lightly grazed Oftheoriginaleight re-sproutingIhhhitisplantsseen in
by Wesicrn Grey Kangaroos and cattle: these animals 19X3.all were still alive in I9K9andfourwerestillalivein
readilyealbathAhutittwand tfthisiiisand markedgraving 1999. giving a minimum lifespan of 16 years. In die study
effects were observed. area, cattle grazing was discontinued in 1988 and
The falls of rain tabulated usually resulted from single following 32 mm ofrain on 7 January 1991. a further 200
warm-season storms, but sometimes significant rains over resprouting ftibisttis plants were found in an area
iVtaorthreeconsecutivedaysaregiven(Table 1) Overthe adjoining the original stand and which bad been searched
15 years studied. Ahufifon appeared in 5 years at anyone previously for this species. We believe that this occurred
sit.;and itfhi\i7K in 10years(tabic 1 ).At least oneepisode through a combination of the rainfall and the absence <>{
ofrain ofmore than about 26 mm between Novemberand cattle gra/.ing. with the gra/.ed-off plants being
MflTCh seems to be needed for plants of both species to undetectable in the presence ofcattle. This more recent,
appearinthestudyarea. Inseasonslike 1994-95and 1997- larger population continues to appear, given appropriate
98. a series of Mnaller falls than this scattered through a rainfall. Since I9XX. it isclearttuit some kangaroograzing
mouth iUs enough lot ftihi.uusmbmut nul Ahtftihw |o grow ofboth lava occurs, especially nl'Ahnti/i'tim site4.
liable Single falls of 26 (e.g. £991-92} or |e*S In the second half of 1990 the lowe.si Rite, .site 4, wift
usually do not produce either species (Table I I. Hooded by high river levels. It was still Hooded and
Following germinalton in \hntihm, development is dominated by a dense stand of the sedge l\h'mlh/ris ui\i\ti
rapid. After the significant rainfall of 2 7 March 1983. K. Br. in November 1990.This almost certainlvcaused the
C
absence til Alnmh.'n m l'MO-1)! ikspiU- suitable rainfall species ol Ahiill/oti .md StJu aiv ol the summer-yimviny
(lahlr I), ivpe ". Theta\aol \h>(tfl>>nandHibiscussltultedherek\\\\
November {$$2 1)m\ the hiiihesl riverlevels since IMSI ', t»ccurin areas with less Mian 1(H)mm mean annual rainfall.
/H/o/o/»d/iwnuga fselifltcllbl-IIHaMeaMiiiI-aHncdtHtWhetWlft\4lhlttfiCti/lTift>V»iiaAnnd/TApacroiriflrlinutchde emxupclhainlowwehryth.ImlletVhedsotudnyotareeax1te.nPdurtthuecrtbwcoirksoiustnh,eedleodwetro
lodominatexitc^ miiIiI at leasl flS. acicowunlin^ lorthe incidence ol sununei ram. iowei lemperalurc icpimes
rthwfiec nJ1 \hunh>ii hi (In- throe- jjeaj* a»5, despite tinclnilin^ fo»s| eHeclsiorbolli may be invoked. A tuitbei
suitable riltll- No small pkiniv occurwithin the densesloin iltiportanl tactol in Ahutidm mid Hihi\,u\ orcurrcncc '*•
am* ihi/.omc systems of /-/rof//oru, presumably because gni^ingr with callte remosal havinj: beneficial elleets at
dies »re outcompelcd. least pn the HlbixtHSpppulalion.
At ilie sue I Ahiitiliui si tnd, fuelierthan site4. the flood Mmfilt'n is j liausienl species which can he absent IfOlTl
diauictl awav v|iiicklvv. A dense Maud oi fho gvHJiR t Afar/i a siie lot at tea.sl six years before re appealing, n,,-,
IfUfHufa a'stillcd aecounlinv! lor (he ahsence of Mntiilou behaviour almost cerminly relies on hard-coiiled seeds
following pood rams in (he two years IW.i.os (thhfe I) lonTitn^ a pcistslenl -.od -i:ci\ bank a«- ii l|oe,s ill Ahm'tlnti
By Ilie lime nf Itic I'W-W records d| Ahiiltiutt and 1hl't)fflmW\'\ Parsons A: Hiowik uivc examples ol lonyer
fY/&)'.Vl Mi (Table I |. QlfohS itlltl /./cot//<//fV had iiiiet\ak before re-afipearancc-
disappeared front Ihe Mlos Many Iransienl species regenerate piotusel> during
We ioikhide ilmt the major abiotic oVlcrmmattk ol* lavourablccuvumstiUices . Vheir absentvoveryearsduring
\hu/ii<>n mature plain occurrence in Hie aica are warm dr\ seasons does not meanthai iheyait thieatenedas tony,
<OtlSOn rainfall and llockltu^. Ilie former necessity lor as. seeds are produced often enouLdi in ensure ihfll
iceruiluieul and (he killertemporally excluding Mmtittw LH.nninaitoii occurs durini', favoutablc seasons. Many such
fry promoting dense siamls rif compelini! species. species are not listed as eilhei rare or thieateiicd '.
Assuming thai an episode ol rain of more than 2b mm Nevertheless, more leeent work points out lhat if the
beiwcen Novcmhci and March is iieeilt'd foryermihrtiioiv habthil i^ not continuously \\{ lor occupalion because ol
in seven ofdie I-S yearssite I e\|Viieiieed lamfall Miimhle transient climatic condition*, this pfl»i inoeuse eMmcbon
loi Ahulihuioccurrence, bit) loi IwooftheseAhitlilt'it was risk and so this lacior is biuh into the new Kilts for
e\eliidcd by po-a-l]oodmii competition lor for tltiee ol chrisilyiue Mich risk1
llicilt in die case or the lower-lvuij; *4lH -il ttihts»'U\ While Abtttlffh ovytdtfhitu k not Itirealeticd \uslra|ia
grf&lh wa-. .itmulatcd under drier conditions than was yvute. there is concern uhoui the Victorian siamk,
Muttlh'h OVrluinalioil po^ahlv bccjiisc ol iK pen* a' especially because ihey are widely disjunei from Ihe
plroooIlndsuslcooecmkeLvdiemsueirt:)shpoenc"ie_:.,Whkiillleso2folaminmaswlttofw la3sw1m0innuinmcuamn s-sIpeenwcoetureses*tfheeroneiacvtediasraegjat»taamU.nlsndig;asriwcohciaktleiibnp-arsIt'os.'uXto-Ilh.eMriinhecIiIftemln\lwcle.\-,aIlhlaerocfmo*Hisoittc
i.mil.ill recorded here which produced seullme emei\>cine katiuaioo-ptool aiul kauearoo jiia/tue prevented seed set
ol Ahuitl"it, the actual c|Jiit»ltr> ol rain needed will be by most Ahlilihi/i. planls ill 1^90 uuil some picvioii.^. year-
yieaily influenced hy (be f|pj|i clay conlenl o|' (he -md> Jhe tatt llial die (iiaximum nundici UT Ahutiloit planls
aiea. whichlias an unfavourable influence on waitersupply avoidedwas well below 250matureindividuals inanyone
in this climale due to die inverse icMiuc effect1 . season means that the specie:- L|uahlic^. a-- taidaneercd in
I'lnti species o| arid 11M scmisirid urea* aie olien Victoria usmy the basic JUCN Re<! last rules lor risk
grouped into 'summer flora"!, "wmtei llora or Ihosc diu assessment The mosi important manaL-cmcnl ivcom
.
tan ^ernuiiali' and establish in bolh seast^ns' . Tin- ^pcties ineudalioii loMovvni.e loan om w<ark is provision of
studied lieic are clear examples ol summei llora In our kangaroo proof feliciue.
MUtly aiva, Sula tfU'tutf^atfu iMalvaceae) behaves very We thank M. I. Bunhw toi [jrcpurtng l*ig 2 and *
uiiich likeHthisat.v In(tonliweskrn Victoria, prohabk .at AJl.n and I. W Morgan loi commcnis on the manuscript
Lanu, I*. ,). A Ki-iieheobm-lil, 1). N. | IWO) pp. 170 |K5 < uiium^ham. ti. \!., \lulh;on, VV. K., Miltbnipi. |» I
In Noble. J. r.V Joss. \\ I \ J.aus fi. K. -H.k. 'Ihe & Utgh, J. II. Uftt-Ii. "Plai.l^ oi Western New South
MMeallblieuenihL.'a)nds. \ Conservation |vrspective" -('SIKU, WJaclseMsi"p,(JN.SIW* &Govleorenlmkeenn,t MP.rinKl.in(yk('UMlfioo1,IShyxduikVoli.South
Tarsons. K. I. I |VMI}) pp. Jfi 2Hf» Noble, l_ (*„Joss. P .1 AU'.lialia" (South Ausllarialt Government IVinlni'-
A' JoilCs. ti K. (I'dsl 'Vhe Vddlee I ands, A (oiiseivalioti DiytsitTQ; Adelaidei.
t'cispeilive" (CSIKO, MelnounicI. I'enshuin, ft.J. I tV*W) kacuela.Kl .1, 21. k: |tt^
I'HiMins, K, |,tV (trowlit'..J.M.l I4'*:I fiiol.C"i>tivei\ U. (lullun, V, K„riiciiK I).( . tV; Wtilsli. N.ti. \ IQMTH Kaie
is.vio:. or llneaicned ktant:, in Victoria" (DeparttULni ol
"WIlluo'ifaliTol.J.HiKe.KtiWu2i*be|rfl{env lU\e\e0i2olu\"hi(WWehscieclrencAJ,uskt.ra|lkida.n) Cvhoih.rske,rvalI'.io&n ,^\\ihi\rksnu\nsi.n»uKm.eiKiillM(>e'l-Mbioukrrnoee. k Soc. Vu .
IIcrbaimm. IVrlh) ior> i^m us.
44
Baskin, C. C. & Baskin, J. M. (1998) 'Seeds" ,4Browne,J. H. (1986). Ibid, 103, 150-157.
(Academic Press, San Diego). 1 Brandle, R. (1998) "A Biological Survey of the Stony
"Parsons, R.F. (1994) pp. 291-319In Groves,R. H. (Ed.) Deserts, South Australia" (Department for Environment,
"Australian Vegetation" 2nd Edn (Cambridge University HeritageandAboriginal Affairs,Adelaide).
Pl2rNeosbsl,eC,amI.brRi.dg&e)C.risp, M. D. (1979/80) Israel J. Bot. 28, A"uBsrtirgaglsi,anJ.PDl.an&ts"Le(iCgShI,ROJ.,HM.el(b1o9u9r6n)e")R.are orThreatened
195-210.
Browne, J. H. (1984)Vict. Nat. 101, 228-233. l7Keith, D.A. (1998) Conserv. Biol. 12, 1076-1090.
R. E PARSONS, DepartmentofBotany, LaTrobe University BundooraVic. 3083 andJ. H. BROWNE,52A
FitzroyAve Red Cliffs Vic. 3496.