Thesis (PhD)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Climate sets range limits in many taxa, and as climate changes, the ranges that plants and
animals occupy are altered. The responses of species to climate change involve either
migration or local adaptation. An investigation of the local physiological adaptation
shown by indigenous and alien arthropods to temperature acclimation formed the primary
focus of this study. Increased environmental temperatures favour the establishment of
alien species on Southern Ocean Islands. The first records of Porce/lio scaber Latreille,
1804 (Isopoda, Porcellionidae) and an Aphidius wasp species from Marion Island were
documented here. The alien wasp was discovered in 2003 and had a current known
distribution along the east coast of Marion Island. Both isopods and wasps were
reproducing successfully on Marion Island. The wasp species is an aphid parasitoid and
had been found mummifying the alien aphid Rhopalosiphum padi. These introductions
highlighted the ongoing conflict between use and conservation on the Southern Ocean
Islands.
Despite considerable work on the upper and lower lethal limits of insects, several major
taxa have received little attention. Here this issue was addressed and the lower and upper
thermal tolerances and cold hardiness strategy of Antarciopsocus jeanneli Badonnel
(Psocoptera: Elipsocidae) from sub-Antarctic Marion Island was investigated. A.
jeanneli is freeze intolerant, and more specifically, moderately chill tolerant. Field fresh
A. jeanne li had a mean supercooling point (SCP) of -11.1oC, whereas LTSO was -7.7°C,
indicating pre-freeze mortality. A. jeanneli responded to acclimation: mean SCP
increased from -IS.8°C at a treatment temperature ofO°C, to -7.3°C at ISOC.
Investigations of the responses to acclimation of upper and lower lethal limits and limits
to activity in insects have focussed primarily on Drosophila. Halmaeusa atriceps
(Staphylinidae) was examined for thermal tolerance responses to acclimation, and
seasonal acclimatization. In summer and winter, lower lethal temperatures of adults and
larvae were c. -7.6 ± 0.03 and -11.1 ± 0.06 °C, respectively. Supercooling points (SCPs)
were more variable, with winter SCPs of -S.4 ± 0.4 °C in larvae and -6.3 ± 0.8 °C in adults. The species appeared to be chill susceptible in summer and moderately freeze
tolerant in winter, thus showing seasonal acclimatization. Critical thermal minima varied
between -3.6 ± 0.2 and -0.6 ± 0.2 °C in larvae, and from -4.1 ± 0.1 to -0.8 ± 0.2 °C in
adults. These findings were in keeping with the general pattern found in insects, although
this species differed in several respects from others found on Marion Island.
In this study the differential responses of indigenous and invasive springtails to
temperature were explicitly examined in the context of the beneficial acclimation
hypothesis (BAH) and its alternatives. In particular, the thermal acclimation responses of
desiccation resistance, supercooling ability, lower and upper thermal limits were
compared. Invasive springtails (Pogonognathellus jlavescens, Isotomurus palustris and
Ceratophysella denticulata) did not display greater phenotypic flexibility than indigenous
springtails (Cryptopygus antarcticus and Tullbergia bisetosa), but did perform better
under high temperature conditions. Indigenous species, however, performed better under
low temperature conditions. In most cases the BAH was not supported, or could not be
distinguished from its alternatives. The prediction that invasive species will outperform
indigenous species as climates on Southern Ocean Islands warm was supported.
Because temperature plays such a large role in the distribution, abundance and
physiological tolerances of invertebrates, microhabitat temperatures along an altitudinal
gradient (0 to 800 m above sea level (asi)) were investigated over a two-year period on
Marion Island. Mean microhabitat temperatures were comparable to those from previous
studies for Southern Ocean Islands, and declined with increasing altitude. The 800 m asl
site had the most severe microclimate (highest absolute maximum, lowest absolute
minimum and the highest frequency of freeze-thaw cycles). Year one was substantially
colder than year two, indicating that interannual variation in microclimate conditions
could be responsible for substantial mortality amongst. invertebrate populations. Indeed,
indigenous species were best able to tolerate the high incidence of low temperatures at
high altitudes, whereas alien species appeared to be confined to lower altitudinal sites on
Marion Island, possibly as a consequence of extreme low temperatures at higher altitudes. / AFRIKAANSE OPSOMMING: Klimaat is een van die grootste faktore wat die verpreiding en digthede van dier en
plantspesies bepaal. Soos wat klimaatsverandering plaasvind, kan spesies migreer om
stresvolle klimaatstoestande te vermy, of hulle kan aanpas by plaaslike omstandighede.
Dit is die laasgenoemde opsie wat in hierdie tesis ondersoek was. Die opsporing van
Porcellio scaber Latreille, 1804 (Isopoda Porcellionidae) en 'n Aphidius wesp van
Marion Eiland word hier aangeteken. Die huidige verspreiding van houtluise in die
omgewing van die Navorsingstasie dui daarop dat hulle die eiland waarskynlik vanaf
Kaapstad in bou-materiaal bereik het. Die wesp is gedurende 2003 ontdek en is tans
versprei langs die oostelike kuslyn van Marion Eiland. Beide hierdie spesies plant
suksesvol voort op Marion Eiland. Die wesp spesie parasiteer die uitheemse plantluis
Rhopalosiphum padi. Uitheemse muise en die inheemse kleinskedebek weier tot dusver
om P. scaber te eet. Die ontdekking van twee nuwe uitheemse spesies dui weereens op
die konflik tussen bewaring en benutting van die Suidsee Eilande.
Ten spyte daarvan dat aansienlike aandag gewy is aan die hoë- en lae temperatuur
toleransies van insekte, is daar talle taksa wat selde nagevors word. Dié toleransies is dus
nagevors vir die boekluis Antarctopsocus jeanneli Badennel (Psocoptera: Elipsocidae)
van Marion Eiland. Die spesie is vries vermydend, en meer spesifiek, matig
verkoelingsbestand. Veldvars A. jeanneli het 'n gemiddelde superverkoelingspunt van -
11.1 °C gehad, en letale temperature (LTSO) van -7.7 °C, wat aandui dat individue vrek
voordat hulle vnes, Hierdie spesie reageer op akklimasie: gemiddelde
superverkoelingspunt het toegeneem van -15.8 °C na akklimasie by 0 °C tot -7.3 °C na
akklimasie by 15 oe.
Die effek van akklimasie op temperatuur toleransie in insekte het dusver meestalop
Drosophila gefokus. Hier vors ons die effek van akklimasie op die temperatuur toleransie
van Halmaeusa atriceps (Styphylynidae) na. In die somer en winter was die lae letale
temperature van kewers en larwes onderskeidelik -7.6 ± 0.03 en -11.1 ± 0.06 °C.
Superverkoelingspunte (SVP) het meer gevarieer, met SVP van -5.4 ± 0.4 °C in larwes en -6.3 ± 0.8 oe in kewers. Die spesie IS verkoelingsvatbaar in die somer en matig
vriesbestand in die winter, wat dui op akklimatisasie in hierdie spesie. Kritiese termale
minima het tussen -3.6 ± 0.2 en -0.6 ± 0.2 oe in larwes, en tussen -4.1 ± 0.1 tot -0.8 ± 0.2
oe in kewers gewissel. Hierdie spesie blyk dieselfde fisiologiese tendense wat in insekte
te vinde is uit te beeld, maar verskil in verskeie opsigte van ander insekte op Marion
Eiland.
Hierdie studie het ook die verskillende reaksies van inheemse en uitheemse springsterte
met betrekking tot temperatuur akklimasie bestudeer. Die voordelige-akklimasie hipotese
en sy alternatiewe hipoteses is in terme van akklimasiereaksies tot desikkasie weerstand,
superverkoeling en lae- en hoë temperatuur bestandheid in Marion Eiland springsterte
getoets. Die uitheemse springsterte (Pogonognathellus jlavescens, Isotomurus cf palustris
en Ceratophysella denticulata) het nie beter fenotipiese plastisiteit getoon as die
inheemse spesies (Cryptopygus antarcticus en Tullbergia bisetosa) nie. Die inheemse
spesies het egter beter gevaar onder lae-temperatuur toestande. Die voordeligeakklimasie
hipotese ontvang nie veelondersteuning in die huidige studie nie, maar kon in
sommige gevalle nie van die alternatiewe hipoteses onderskei word nie.
Klimaatsverandering mag uitheemse spesies bevoordeel.
Die rol wat temperatuur in die verspreiding en fisiologiese toleransies van invertebrate
speel word lank reeds waardeer. Daarom vors hierdie studie die mikrohabitat temperature
teen 'n gradient tussen seespieël en 800 m bo seespieël (m bs) oor 'n tydperk van twee
jaar op Marion Eiland na. Gemiddelde temperature is vergelykbaar met die van vorige
studies op Marion Eiland, en neem af soos wat hoogte bo seespieël toeneem. Die 800 m
bs studie-gebied het die mees stresvolle mikrohabitat-toestande ondervind (die hoogste
absolute maksimum, laagste absolute minimum temperature, en die meeste vries-ontdooi
siklusse). Inheemse spesies op Marion Eiland toon hoër.toleransies tot lae temperature as
uiheemse spesies, laasgenoemde kom slegs voor by laer hoogtes bo seespieël, waar
ekstreme ternperatuur-toestande dalk minder volop is. Klimaatsverwarming mag egter tot
'n toename in ekstreme weerstoestande lei op Marion Eiland, wat aansienlike mortaliteit
in invertebraat populasies kan veroorsaak.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/50417 |
| Date | 12 1900 |
| Creators | Slabber, Sarette |
| Contributors | Chown, S. L., Stellenbosch University. Faculty of Science. Dept. of Botany and Zoology. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 224 p. : ill. |
| Rights | Stellenbosch University |
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