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From: Eric Gouda <E.J.Gouda at BIO.UU.NL>
Subject: article abstract
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A survey of the function of the lethal kettle traps of Arisaema (Araceae)=,=
with records of pollinating fungus gnats from Nepal
pp. 61-100 (doi:10.1006/bojl.1999.0317)


1Institut f=FCr Botanik der Universit=E4t Wien, Rennweg 14, Vienna, A=-1030,=
2Institut f=FCr Zoologie der Universit=E4t Mainz, M=FCllerweg 6, Ma=inz,=
Germany &Category=all&Journal=all"IDEAL Related Articles
(Received March 1999; accepted November 1999; published electronically Ma=y=
18, 2000)

Evidence from recent research combined with an evaluation of the literatu=re=
indicates that Arisaema is adapted to pollination by fungus gnats. It=2=0
apparently shares this peculiarity among aroids only with the distantly= 
related genus Arisarum. In addition to previous records from Japan and= 
North America, systematic collections from nine Arisaema species during= 
several expeditions in the Himalayas in Nepal showed that, although other= 
less efficient insect groups may participate, the nematoceran families= 
Mycetophilidae and Sciaridae are the principal pollen vectors; they best= 
fit the pollination apparatus of the mainly (para)dioecious kettle trap= 
blossoms. A total of 16 fungus gnat genera (both Mycetophilidae and 
Sciaridae) comprising 47 identified species (among them one genus and 22= 
species new to science) were observed. Usually members of more than one= 
taxon are attracted per Arisaema species, and both sexes of gnats are=2=0
involved. Visitor sets differed to some degree, depending on host species=,=
area, and altitude; they do not, however, represent the complete fungus= 
gnat fauna of a region. Relevant traits of growth habit and inflorescence= 
structure are surveyed, and a detailed description of the pollination=2=0
process is given, based on observations made on specimens cultivated in= 
Europe, where vicariant fungus gnats are the pollinators. Attraction is= 
deceptive by mimicking olfactory, visual and tactile cues characteristic =of=
fungi where the gnat sexes normally meet and females oviposit. Odours=2=0
produced by osmophores (the spadix appendage or spathe tip) play the most= 
important part. The identified volatile compounds are mainly short-chaine=d=
aliphatic aldehydes and alcohols. Flagelliform osmophores of some species=,=
up to several dm long, reach the substrate and serve as conducting paths.= 
Gnats become imprisoned when they inadvertently slide down the inner wall= 
of the spathe tube. Its surface including the spadix is covered with 
ablative wax particles that inactivate the insects=BB tarsal pulvilli. =This=
gliding device, in some species reinforced by zones of imbricate papillae=,=
is irreversible, and no movements of floral parts allowing escape via the= 
spathe mouth occur. Anthesis lasts several weeks. In the male spathes,= 
victims are forced to wade through the pollen masses that have accumulate=d=
at the spathe's bottom; there they find an exit hole formed by local gapi=ng=
of the spathe rims. The female spathes lack such an aperture. After 
potentially depositing pollen on the stigmas during their efforts to 
escape, gnats are detained until death. Except for an autogamous subspeci=es=
of A. flavum Schott, the few monoecious taxa of Arisaema are protogynous= 
and possibly self-sterile. In monoecious A. tortuosum (Wall.)Schott, exit= 
forming is delayed until pollen release. Three Arisarum species that are= 
suspected to deviate in their floral syndrome are discussed along with= 
araceous genera possessing similar one-way pitfall mechanisms. Copyright= 
2000 The Linnean Society of London Key Words: floral deception - 
Mycetophilidae - osmophores - sapromyiophily - Sciaridae.

Corresponding author. E-mail: vogel at

____               ____   E.J.Gouda at
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<font size=4>A survey of the function of the lethal kettle traps of
<b><i>Arisaema</i></b> (Araceae), with records of pollinating fungus
gnats from Nepal</font> <br>
pp. 61-100 (doi:10.1006/bojl.1999.0317) <br><br>
<b>STEFAN VOGEL<font size=1><sup>1</sup></font>, JOCHEN
MARTENS<font size=1><sup>2 <br><br>
</b><i>1</sup></i></font><b>Institut f=FCr Botanik der Universit=E4t =Wien,
Rennweg 14, Vienna, A-1030, Austria <br>
<font size=1><sup>2</sup></font>Institut f=FCr Zoologie der Univers=it=E4t
Mainz, M=FCllerweg 6, Mainz, D-55099, Germany
<font color="#0000FF"><u>&amp;Category=all&amp;Journal=all&qu=ot;IDEAL
Related Articles<br>
</u></font><font size=2>(Received March 1999; accepted November 1999;
published electronically May 18, 2000)<br><br>
</font><font color="#FFFFFF">Abstract<br>
</b></font>Evidence<font size=1><sub> </sub></font>from recent resear=ch
combined with an evaluation of the<font size=1><sub>
</sub></font>literature indicates that <i>Arisaema</i><font size=1><s=up>
</sup></font>is<font size=1><sub> </sub></font>adapted to pollination=by
fungus gnats.<font size=1><sub> </sub></font>It<font size=1><sup>
</sup></font>apparently shares this peculiarity among aroids
only<font size=1><sub> </sub></font>with the<font size=1><sup>
</sup></font>distantly related genus <i>Arisarum</i>.<font size=1><su=b>
</sub></font>In addition to<font size=1><sup> </sup></font>previous
records from<font size=1><sub> </sub></font>Japan and North
America,<font size=1><sup> </sup></font>systematic<font size=1><s=ub>
</sub></font>collections from nine <i>Arisaema</i>
species<font size=1><sub> </sub></font>during<font size=1><sup>
</sup></font>several expeditions in the Himalayas in Nepal
showed<font size=1><sub> </sub></font>that,<font size=1><sup>
</sup></font>although other less efficient<font size=1><sub>
</sub></font>insect groups may<font size=1><sup>
</sup></font>participate, the<font size=1><sub> </sub></font>nematoce=ran
families Mycetophilidae and<font size=1><sup>
</sup></font>Sciaridae<font size=1><sub> </sub></font>are the princip=al
pollen vectors; they<font size=1><sub>
</sub></font>best<font size=1><sup> </sup></font>fit the pollination
apparatus of the<font size=1><sub> </sub></font>mainly<font size==1><sup>
</sup></font>(para)dioecious kettle trap blossoms. A
total<font size=1><sub> </sub></font>of 16 fungus<font size=1><su=p>
</sup></font>gnat genera (both<font size=1><sub>
</sub></font>Mycetophilidae and Sciaridae)<font size=1><sup>
</sup></font>comprising 47<font size=1><sub> </sub></font>identified
species (among them one genus and<font size=1><sub>
</sub></font>22<font size=1><sup> </sup></font>species new to science=)
were observed.<font size=1><sub> </sub></font>Usually<font size=1=><sup>
</sup></font>members of more than one taxon are<font size=1><sub>
</sub></font>attracted per <i>Arisaema</i><font size=1><sup>
</sup></font>species, and both<font size=1><sub> </sub></font>sexes o=f
gnats are involved. Visitor<font size=1><sup> </sup></font>sets
differed<font size=1><sub> </sub></font>to some degree, depending on
host<font size=1><sup> </sup></font>species,<font size=1><sub>
</sub></font>area, and altitude; they do not, however,<font size=1><s=up>
</sup></font>represent<font size=1><sub> </sub></font>the complete fu=ngus
gnat fauna of a<font size=1><sub> </sub></font>region.<font size==1><sup>
</sup></font>Relevant traits of growth habit and<font size=1><sub>
</sub></font>inflorescence<font size=1><sup> </sup></font>structure a=re
surveyed, and a detailed<font size=1><sub> </sub></font>description o=f
the<font size=1><sup> </sup></font>pollination process<font size==1><sub>
</sub></font>is given, based on observations made<font size=1><sup>
</sup></font>on specimens<font size=1><sub> </sub></font>cultivated i=n
Europe, where vicariant<font size=1><sup>
</sup></font>fungus<font size=1><sub> </sub></font>gnats are the
pollinators. Attraction is<font size=1><sup>
</sup></font>deceptive<font size=1><sub> </sub></font>by mimicking
olfactory, visual and tactile<font size=1><sub>
</sub></font>cues<font size=1><sup> </sup></font>characteristic of fu=ngi
where the gnat sexes<font size=1><sub>
</sub></font>normally<font size=1><sup> </sup></font>meet and females
oviposit.<font size=1><sub> </sub></font>Odours produced
by<font size=1><sup> </sup></font>osmophores (the
spadix<font size=1><sub> </sub></font>appendage or spathe tip) play
the<font size=1><sup> </sup></font>most important<font size=1><su=b>
</sub></font>part. The identified volatile<font size=1><sub>
</sub></font>compounds<font size=1><sup> </sup></font>are mainly
short-chained aliphatic aldehydes<font size=1><sub>
</sub></font>and<font size=1><sup> </sup></font>alcohols. Flagellifor=m
osmophores of some<font size=1><sub> </sub></font>species, up
to<font size=1><sup> </sup></font>several dm long,
reach<font size=1><sub> </sub></font>the substrate and serve
as<font size=1><sup> </sup></font>conducting<font size=1><sub>
</sub></font>paths. Gnats become imprisoned when<font size=1><sub>
</sub></font>they<font size=1><sup> </sup></font>inadvertently slide =down
the inner wall of the<font size=1><sub>
</sub></font>spathe<font size=1><sup> </sup></font>tube. Its surface
including the spadix<font size=1><sub> </sub></font>is covered
with<font size=1><sup> </sup></font>ablative wax
particles<font size=1><sub> </sub></font>that inactivate the
insects=BB<font size=1><sup> </sup></font>tarsal<font size=1><s=ub>
</sub></font>pulvilli. This gliding device, in some<font size=1><sub>
</sub></font>species<font size=1><sup> </sup></font>reinforced by zon=es
of imbricate papillae,<font size=1><sub>
</sub></font>is<font size=1><sup> </sup></font>irreversible, and no
movements of floral<font size=1><sub> </sub></font>parts allowing
escape<font size=1><sup> </sup></font>via the spathe<font size=1>=<sub>
</sub></font>mouth occur. Anthesis lasts several<font size=1><sup>
</sup></font>weeks. In the<font size=1><sub> </sub></font>male spathe=s,
victims are forced to<font size=1><sub>
</sub></font>wade<font size=1><sup> </sup></font>through the pollen
masses that have accumulated<font size=1><sub>
</sub></font>at<font size=1><sup> </sup></font>the spathe's bottom; t=here
they find an<font size=1><sub> </sub></font>exit hole<font size=1=><sup>
</sup></font>formed by local gaping of<font size=1><sub> </sub></font=>the
spathe rims. The female<font size=1><sup> </sup></font>spathes
lack<font size=1><sub> </sub></font>such an aperture. After
potentially<font size=1><sup> </sup></font>depositing<font size=1=><sub>
</sub></font>pollen on the stigmas during their efforts<font size=1><=sub>
</sub></font>to<font size=1><sup> </sup></font>escape, gnats are deta=ined
until death. Except<font size=1><sub> </sub></font>for
an<font size=1><sup> </sup></font>autogamous subspecies of
<i>A.<font size=1><sub> </sub></font>flavum</i> Schott, the
few<font size=1><sup> </sup></font>monoecious taxa of
<i>Arisaema</i><font size=1><sub> </sub></font>are protogynous and
possibly<font size=1><sup> </sup></font>self-sterile.
In<font size=1><sub> </sub></font>monoecious <i>A. tortuosum</i>
(Wall.)Schott,<font size=1><sup> </sup></font>exit
forming<font size=1><sub> </sub></font>is delayed until pollen releas=e.
Three <i>Arisarum</i><font size=1><sup>
</sup></font>species<font size=1><sub> </sub></font>that are suspecte=d to
deviate in their<font size=1><sub> </sub></font>floral<font size==1><sup>
</sup></font>syndrome are discussed along with araceous<font size=1><=sub>
</sub></font>genera<font size=1><sup> </sup></font>possessing similar
one-way pitfall<font size=1><sub> </sub></font>mechanisms.
<i>Copyright<font size=1><sup> </sup></font>2000 The
Linnean<font size=1><sub> </sub></font>Society of
London</i><font size=1><sup> </sup></font><i>Key Words: </i>floral
deception - Mycetophilidae - osmophores - sapromyiophily - Sciaridae.
Corresponding author. E-mail: vogel at<br><br>

<font face="Arial Narrow Special G1, Helvetica" size=2>+++<br>
<font face="Courier New, Courier" size=2 color="#FF0000">E.J.=Gouda</fo=
<a href=""=
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