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Long-term climate variability at the Prince Edward Islands in the Southern OceanShangheta, Anna Liisa Penelao Tulimevava 16 March 2022 (has links)
A warming Southern Ocean (SO), due to climate change and global warming, has many implications on the sub-Antarctic Islands in the SO. Due to the distance away from continental land these islands experience an oceanic climate, making them the perfect sentinels to climate change in this sector of the Southern Ocean. Studies have proposed that climate changes reported at the Prince Edward Islands (PEIs) correspond in time to a southward shift of the Antarctic Circumpolar Current (ACC) particularly the Subantarctic Front (SAF). While other studies have shown distinctive trends in ocean and atmospheric parameters such as sea surface temperature (SST), air temperature, sunshine, rainfall, air sea level pressure and wind speed and direction from the 1950s to the early 2000s, the aim of this study is to update those studies to a more recent time with updated time series. Among the changes recorded is an increase in SST and air temperature, which is a strong indication of the changing local and global climate. Using linear regression, this study showed that the rates of increase from 1949 to 2018 of the SST (0.022°C/year), minimum (0.0072°C/year) and maximum air temperatures (0.016°C/year) are smaller than estimated in previous studies. The increasing trend in SST and air temperature reported by previous papers has actually stopped since the 2000s, which reduces the formerly reported trend (0.028°C/year). Although the in-situ measured SST data had gaps, a good correlation with in-situ SST and large scale satellite derived Reynolds SST help to corroborate the covariation between SST, in-situ SST and air temperature giving weight to the hypothesis of a reversal of the positive temperature trends reported by others. The change in decadal variability a decrease in air pressure of 4 hPa since the late 1990s to late 2000s, which coincided with a decrease in minimum and maximum air temperatures of 1°C over the same period; decrease in westerly wind and an increase in the northerly component of the wind, which would explain the decrease of inshore sea surface temperature a while thereafter. This study further corroborates previous findings of a continued decrease in rainfall, while the sunshine has largely remained the same. The seasonal cycle of the air pressure is significantly associated with that of rainfall, showing that the bimodal high air pressure signature resulting from the Semi-annual Oscillation (SAO) is associated with a decrease in rainfall. The Southern Annual Mode (SAM) was significantly yet weakly correlated with the SST (0.24), rainfall (-0.25) and air pressure (0.16), indicating that it does have an impact at the PEIs but not as strong as previously speculated. The El Niño Southern Oscillation (ENSO) has very weak and insignificant relationships with the parameters examined except for a weak relationship with in-situ SST, sunshine and air pressure. These new insights, especially at the decadal timescale, could further our insight on how subAntarctic islands have responded to climatic changes.
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Acclimation effects on thermal tolerance in ameronothrid mites at sub-Antarctic Marion IslandDeere, Jacques Andries 12 1900 (has links)
Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Evidence for widespread ecological impacts due to rapid climate change is on the
increase, with further warming predicted over the next century. This increase in warming
has lead to organisms adjusting their distribution range and where this is not possible
organisms must cope with the stressful environments in a different way. One potential way
to handle environmental stress is via a mechanism known as phenotypic plasticity, which
allows an organism to express different phenotypes depending on the biotic or abiotic
environment in a way that may alter that organism's fitness. Acclimation temperatures can
potentially cause plastic (reversible and irreversible) changes in the response of individuals
to stressful experimental conditions that could increase their survival. The issue of whether
this acclimation will be beneficial to the organism or not remains contentious, with support
offered both for and against the idea of beneficial acclimation. The aims of the
investigation were to determine the thermal limits of five ameronothrid mite species
(Halozetes marinus, H marionensis, H belgicae, H. fulvus and Podacarus auberti) from
varying terrestrial habitats and to test whether there is beneficial acclimation on the thermal
traits. Along with the beneficial acclimation hypothesis several alternative hypotheses were
also tested. In addition, locomotor performance was determined as it has been suggested
that locomotion performance is a reliable and practical measure of potential fitness of
animals. The same hypotheses testing the effects of acclimation temperature on the thermal
limits were tested on three performance traits; performance breadth, optimum speed and
optimum temperature. Support for beneficial acclimation was found in the performance
breadth and optimum speed traits for all species except for Halozetes marinus. For the
optimum temperature trait the prediction for the compensation hypothesis was met and that
of the beneficial acclimation hypothesis rejected, with the only exception again being that
of H marinus. In the case of the locomotor performance traits the prediction for the beneficial acclimation hypothesis in the performance breadth and optimum speed traits are
the same for that of the compensation hypothesis, therefore the overall response of the
more terrestrial mite species is one of compensation. However, support for beneficial
acclimation was not found in the thermal limit traits of all five species, with the higher
acclimation temperatures (specifically 150 C) resulting in negative responses in LLT in H.
marinus and H. belgicae, and in ULT in H. fulvus. Phenotypic flexibility varied between
marine and terrestrial species. The less variable marine environment showed lower
flexibility than that of terrestrial species in the performance breadth trait and optimum
temperature trait, but there was a lack of variation between the marine and terrestrial
species in the temperature tolerance traits. These results show that the effects of
acclimation on various traits, especially fitness related traits, are complex and require more
attention if the consequences are to be fully explained. This study therefore provides
insight into the effects of acclimation on performance traits and thermal limit traits and has
implications for the evolution of plastic responses in terrestrial arthropods. / AFRIKAANSE OPSOMMING: Bewys vir wye ekologiese impakte as gevolg van vinnige klimaatsverandering is aan
die toeneem, met verdere verwarming wat voorspel word gedurende die volgende eeu. Dié
toename in verwarming het alreeds veroorsaak dat organismes hulle verspreidings
verander, of waar dit nie moontlik is nie, moet hulle stresvolle omgewingstoestande op 'n
ander wyse hanteer. Een moontlike manier om omgewingsstres te hanteer is deur gebruik te
maak van 'n meganisme wat bekend staan as fenotipiese plastisiteit, wat dit vir 'n
organisme moontlik maak om ander fenotipes te toon afhangende van die biotiese of
abiotiese omgewing in 'n wyse wat die organisme se fiksheid beinvloed. Temperatuur
akklimasie kan moontlik plastisiteit (omkeerbaar of onomkeerbaar) veranderinge in die
reaksie van individue tot stresvolle eksperimentele toestande tot gevolg hé, wat gevolglik
hulle oorlewing kan verhoog. Die kwessie of hierdie akklimasie wel voordelig vir die
organisme is of nie is steeds betwisbaar, met beide steun vir en teen die idee van voordelige
akklimasie. Die doel van hierdie ondersoek was om vas te stel wat die termiese limiete van
vyf ameronothrid myt spesies (Halozetes marinus, H marionensis, H belgicae, H fulvus
en Podacarus auberti) van verskeie terrestriële habitatte is, en om te toets of daar
voordelige akklimasie in die termiese eienskappe voorkom. Tesame met die voordelige
akklimasie hipotese is daar verskeie alternatiewe hipoteses ook getoets. Verder, is
bewegings prestasie vasgestelomdat dit al voorgestel is dat bewegings prestasie 'n
betroubare en praktiese mate van die potensiële fiksheid van 'n dier aantoon. Dieselfde
hipotese wat die effek van akklimasie temperatuur op die termiese limiete toets, is op drie
prestasie eienskappe getoets; prestasie wydte, optimale spoed en optimale temperatuur.
Bewyse vir voordelige akklimasie is gevind in die prestasie wydte en optimale spoed
eienskappe vir alle spesies behalwe Halozetes marinus. Vir die optimale temperatuur
eienskap was die voorspelling vir die kompensasie hipotese korrek maar dié van die voordelige akklimasie verkeerd, met H. marin us die enigste uitsondering. In die geval van
die bewegings prestasie eienskappe is die voorspelling vir die voordelige akklimasie
hipotese in die prestasie wydte en optimale spoed eienskappe die selfde as vir die
kompensasie hipotese. Daarom is die algemene reaksie vir die meer terrestriële spesies een
van kompensasie. Bewyse vir voordelige akklimasie is egter nie gevind in die termiese
limiet eienskappe van die vyf spesies nie, met die hoér akklimasie temperature (spesifiek
15° C) wat 'n negatiewe reaksie in LLT in H. marin us en H. belgicae, en in UL T in H.
fulvus veroorsaak het. Fenotipiese buigsaamheid het verskil tussen mariene en terrestriële
spesies. Die minder variërende mariene omgewing het 'n laer buigsaamheid in die prestasie
wydte en optimale temperatuur eienskappe getoon as die van terrestriële spesies, maar daar
was geen variasie tussen mariene en terrestriële spesies in die temperatuur toleransie
eienskappe nie. Die resultate wat hier voorgelê word wys dat die gevolge van akklimasie
op verskeie eienskappe, veral fiksheids verwante eienskappe, ingewikkeld is en vereis meer
aandag om die gevolge volledig te verduidelik. Hierdie studie verskaf dus insig in die
gevolge van akklimasie vir prestasie eienskappe en termiese limiet eienskappe en het
gevolge vir die evolusie van plastiese reaksies in terrestriële arthropoda.
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The interaction between a keystone plant species and its dominant epiphyte on Marion Island : climate change implicationsBuwa, Ziphokazi Siyasanga 12 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Climate has shown some remarkable changes over the past century, especially at the
polar and sub-polar regions. Southern Ocean Islands provide good models for studies
related to climate change effects, since effects may be evident in the short term and may
also be clearer. Marion Island is an example of such a system with a harsh abiotic
environment, and low species richness often vulnerable to change. Climate change is
predicted, and also reported, to have biological consequences on plant communities,
affecting the phenology, morphology, and the interaction between individuals and
species. This study examines the association between the keystone plant species, Azorella
selago Hook. (Apiaceace), and its dominant epiphyte Agrostis magellanica Lam.
(Poaceae). Two complimentary approaches were used, one observational and the other
experimental. The main objective for the observational study was to quantify bioticallyrelevant
microclimate temperature, as well as the morphology, epiphyte load and
phenology of A. selago at three different altitude sites on Marion Island. This provided
information on baseline variation for understanding specific variability in plant response
to the experimental part of this study, against which future patterns arising from
biological monitoring can be compared. Studying plants at different altitudes provides a
possible analogue for temperature-related climate change consequences for the ecology
of A. selago, and its interaction with A. magellanica. The microclimate temperature
associated with A. selago differed between the three sites examined. This difference was
related to local topographic conditions and altitude differences. Cushion size differed
distinctively between the three altitude sites, with this difference related to environmental
heterogeneity such as differences in age and substrate structure. Azorella selago annual
growth rate was estimated through stem length and the number of leaves on both exposed
and shaded stems. Within-site variability, as well as epiphyte cover were found to be the
contributing factors on A. selago annual growth rate. This highlights the importance of
site-specificity when estimating growth rate within and between different altitude sites.
Leaf characteristics differed between the sites, with this attributed to local habitat
conditions, such as topography, as well as epiphyte cover. As expected, the difference in
leaf size between exposed and shaded leaves demonstrated a larger specific leaf area on leaves shaded by A. magellanica. Agrostis magellanica abundance and density were
altitudinally related, with A. selago demonstrating facilitation effects on A. magellanica.
The trend shown in this study suggests that in spite of general facilitative effect of A.
selago on A. magellanica towards higher altitudes, the abiotic environmental threshold
for A. magellanica occurs at lower altitudes than it does for A. selago. Phenological
differences were also apparent between the three sites. The objectives of the experimental
part of this study were to quantify the effect of the dominant epiphyte, A. magellanica on
biotically-relevant microclimatic temperatures, as well as on the phenology and physical
condition of A. selago. Different treatments were applied to cushions at the three altitude
sites to examine the shading effect of epiphytic A. magellanica on cushion plants, as well
as the effect of treatment-related disturbance. Azorella selago microclimate temperature
showed no significant difference between treatments, suggesting that on average
epiphytic A. magellanica cover has no effect on cushion microclimate temperature. The
percentage of flower budding and flowering of A. selago was negatively related to
epiphyte cover. Cushion vitality was also responsive to epiphyte cover, with higher
vitality scores on low grass covered cushions than on high grass cushions. This shows
that A. magellanica competes with A. selago, while A. selago facilitates A. magellanica.
Heavy epiphyte numbers impose negative effects on A. selago vegetative and
reproductive performance, as well as cushion vitality. Therefore, the results of this
research show that the vegetative and reproductive performance of A. selago and cushion
vitality are likely to be negatively affected under ongoing climate change on Marion
Island if this brings about heavier epiphyte loads on this keystone cushion plant species. / AFRIKAANSE OPSOMMING: In die afgelope eeu het die klimaat in die Antarktiese en sub-Antarktiese gebiede
merkwaardige verandering getoon. Die Suidelike See Eilande dien as goeie modelle vir
studies verwant aan die gevolge van klimaatsverandering, aangesien die kort termyn
effekte in die gebiede duideliker mag wees in die toekoms. Marion Eiland is ‘n voorbeeld
van so ‘n sisteem, met ‘n ruwe abiotiese omgewing en lae spesies rykheid, wat vatbaar is
vir verandering. Daar word voorspel, en is reeds bevind dat klimaatsverandering
biologiese gevolge op plant gemeenskappe het, in terme van morfologie, fenologie en die
interaksie tussen individue en spesies. Hierdie studie ondersoek die assosiasie tussen die
hoeksteen plant spesie, Azorella selago (Apiaceace), en sy dominante epifietiese gras,
Agrostis magellanica Lam. (Poaceae). Die studie is op twee komplimentêre maniere
benader, naamlik deur waarneming en eksperiment. Die hoof doel van die studie was om
die biotiese belang van mikroklimaat temperatuur te kwantifiseer, en die hoeveelheid
epifiete, die morfologie en die fenologie van A. selago te bepaal by drie verskillende
hoogtes op Marion Eiland. Laasgenoemde het inligting verskaf oor die variasie in die
reaksie van plante tot die eksperimentele aspek van die studie, waarteen patrone vanaf
toekomstige biologiese beheer vergelyk kon word. Deur plante te bestudeer by
verskillende hoogtes bo seespieël word ‘n moontlike analoog vir die gevolge van
temperatuur-verwante klimaatverandering in terme van die ekologie van A. selago, en
laasgenoemde se interaksie met A. magellanica verskaf. Die mikroklimaat temperatuur
geassosieer met A. selago verskil tussen dié drie liggings. Die versil was verwant aan die
plaaslike topografiese toestande en die verskillende hoogtes bo seespieël. Die grootte van
die kussingplante het duidelik versil tussen die drie liggings, met die verskille verwant
aan die omgewing se heterogeneïteit, byvoorbeeld die verskille in ouderdom en substraat
struktuur. Azorella selago se jaarlikse groeitempo was bepaal deur die stingel lengte en
die aantal blare, op beide die wat oorskadu is deur die gras, en die was nie oorskadu is
nie. Daar is gevind dat die faktore wat bygedra het tot die jaarlikse groeitempo van A.
selago, varieër binne die verskillende liggings, en bedekking deur epifiete. Dit
beklemtoon die belang van spesifisiteit van ligging wanneer groeitempo in en tussen die
liggings van verskillende hoogtes bepaal word. Die blaar eienskappe het verskil tussen verskillende liggings, as gevolg van plaaslike habitat toestande, soos topografie en
bedekking deur epifiete. Soos verwag, het die blare wat oorskadu was deur A.
magellanica ‘n groter spesifieke blaar area getoon as blare wat blootgestel was. Die
hoeveelheid en digtheid van Agrosits magellanica was verwant aan hoogte bo seespieël,
met A. selago wat fasiliterende effekte toon op A. magellanica. Die tendens waargeneem
in hierdie studie is dat ten spyte van die algemene fasiliterende effek van A. selago op A.
magellanica, die abiotiese omgewingsdrempel op ‘n laer hoogte is vir A. magellanica as
vir A. selago. Fenologiese verskille was ook duidelik tussen die drie liggings. Die doel
van die eksperimentele deel van die studie was om die effek van die dominante epifiet, A.
magellanica, te bepaal op bioties relevante mikroklimaat temperature, asook op die
fenologie en fiesiese toestand van A. selago. Verskeie behandelings is aangewend op die
kussingplante by die drie liggings om die effek van skaduwee van die epifietiese A.
magellanica op die plante te bepaal, asook die effek van versteurings versoorsaak deur
die behandelings. Azorella selago se mikroklimaat temperatuur het geen betekenisvolle
verskille tussen behandelings getoon nie, wat voorstel dat epifitiese A. magellanica oor
die algemeen geen effek op die kussingplante se mikroklimaat temperatuur het nie. Daar
was ‘n negatiewe verwantskap tussen die hoeveelheid epifiete op A. selago en die
persentasie blomme en blomknoppe op die kussingplante. Die plante se vitaliteit was ook
afhanklik van epifiet bedekking, met ‘n hoër vitaliteit telling vir kussingplante bedek met
lae gras as die bedek met hoë gras. Dit toon dat A. magellanica met A. selago wedywer,
terwyl A. selago vir A. magellanica fasiliteer. Hoë epifiet getalle het negatiewe effekte op
A. selago se vegetatiewe en reproproduktiewe nakoming, asook die kussingplante se
vitaliteit. Die resultate van hierdie studie toon dus dat die vegetatiewe en reproduktiewe
nakoming van A. selago en kussingplant vitaliteit heel moontlik negatief geaffekteer sal
word indien klimaatsverandering op Marion Eiland hoër epifiet getalle op die sleutel
kussingplant spesie tot gevolg sal hê.
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Patterns of variability in Azorella selago Hook. (Apiaceae) on sub-Antarctic Marion Island : climate change implicationsNyakatya, Mawethu Justice 12 1900 (has links)
Thesis (MSc)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Understanding the responses of species to climate change is a scientific
problem that requires urgent attention, especially under current conditions of
global climate change. The large and rapid rates of climate change reported
for sub-Antarctic Marion Island makes the island highly suitable for studying
the biotic consequences of climate change. Furthermore, the extreme
environments on the island result in a close coupling of the biotic (e.g.
population dynamics) and abiotic (e.g. climate) factors. Therefore, examining
the response of the dominant and keystone plant species on the island,
Azorella selago Hook. (Apiaceae), to climate-associated environmental
change (e.g. temperature) may provide insight into how A. selago and the
associated species communities will be affected by climate change. This
study described the variability in microclimate temperatures associated with A.
selago across altitudinal gradient and between the eastern and western sides
of Marion Island. Microclimate temperatures were also compared to the
island’s Meteorological data to determine variation between temperatures
experienced by A. selago cushion-plants in the field and those recorded at the
island’s Meteorological Station. Temperature variation inside and outside A.
selago cushions was also examined. Azorella selago cushions were found to
have a buffering effect on temperature, such that species occurring
epiphytically on A. selago experience more moderate temperatures than the
surrounding environment. However, A. selago were found to experience more
extreme temperatures than temperatures recorded at the Meteorological
Station. Therefore, A. selago may possibly experience greater environmental
warming than recorded by the Meteorological Station. While temperatures
decline with altitude, temperature conditions on the western side of the island
were more temperate than the eastern side. This presents the first record of
temperature conditions on the western side of the island. This study also
quantified fine-scale (e.g. within-site) and broad-scale (e.g. island-wide)
variability patterns of A. selago (morphology, phenology, and epiphyte load)
across Marion Island. Altitudinal gradient and climatic exposure at different
sides of the island were used to understand the likely effects of climate
associated environmental change on this dominant component of the fellfield habitat. Site-specific processes were found to determine the spatial structure
of A. selago characteristics at fine-scales. However, broad-scale observations
established strong responses of A. selago characteristics to altitudinal
gradients and different sides of the island. Azorella selago morphological
features (e.g. plant size and leaf size) were found to be more responsive to
differences between the eastern and western sides of the island than to
altitudinal gradient. Azorella selago micro-morphological features (e.g. leaf
trichomes and stomatal densities) were also found to be more responsive to
climatic exposure at different sides of the island than to altitudinal gradient.
However, differences in A. selago epiphyte density (e.g. Agrostis magellanica)
and phenology resembled microclimate temperatures in that they were more
responsive to altitudinal gradient than to side of the island differences. From
these results it can therefore be predicted that the A. selago of Marion Island
is likely to be morphologically fairly resilient to moderate climatic shifts,
although at lower altitudes and on the eastern side of the island, it may be
outcompeted by the epiphytic grass, Agrostis magellanica. The results also
suggest that the warming climate of Marion Island may result in an early
occurrence of phenological processes particularly at lower altitudes and the
eastern side. Azorella selago at lower altitudes and on the eastern side of
Marion Island are therefore expected to largely show more symptoms of
climate change (e.g. warming) on this species. Azorella selago is also
predicted to move up altitudinal gradients in response to warming. / AFRIKAANSE OPSOMMING: ’n Begrip van hoe spesies reageer op klimaatsverandering is ’n wetenskaplike
vraag wat onmiddellike aandag benodig, veral onder huidige globale
klimaatsverandering. Die groot en snelle tempo waarteen klimaatsverandering
waargeneem word op sub-Antarktiese Marion Eiland, maak die eiland hoogs
geskik om die biotiese gevolge van klimaatsverandering te bestudeer. Verder
veroorsaak die uiterste omgewing van die eiland tot ’n nabye koppeling
tussen die biotiese (bv. populasie dinamika) en abiotiese (bv. klimaat) faktore.
Dus, deur die reaksies van ’n dominante- en sleutel-spesie op die eiland,
Azorella selago Hook. (Apiaceae), op klimaat-geassosieerde omgewings
verandering (bv. temperatuur) te bestudeer, mag insig verskaf hoe A. selago
en geassosieerde spesie gemeenskappe geaffekteer sal word deur
klimaatsverandering. Hierdie studie beskryf die wispelturigheid in mikroklimaat
temperature geassosieer met A. selago oor ’n hoogte gradiënt asook tussen
die oostelike en westelik dele van Marion Eiland. Mikroklimaat temperature
was ook vergelyk met die eiland se Meteorologiese data met die doel om die
mate van variasie tussen temperature verduur deur A. selago kussing-plante
in die natuurlike omgewing met die van die eiland se Meteorologiese stasie te
vergelyk. Temperatuur variasie binne en buite A. selago kussing-plante is ook
vasgestel. Dit was gevind dat Azorella selago kussing-plante die temperatuur
buffer, met die gevolg dat spesies wat epifities op A. selago voorkom, meer
gematigde temperature ondervind as die onmiddellike omgewing om die
plant. Daar is egter gevind dat A. selago meer uiterste temperature ondervind
as temperature gemeet by die Meteorologiese stasie. Dus mag A. selago
groter omgewings verwarming ervaar as wat temperature gemeet by die
Meteorologiese stasie dui. Terwyl temperatuur afneem met ’n toename in
hoogte, was temperatuur aan die westekant van die eiland mere gematig as
die oostekant. Dit verskaf die eerste rekord van temperatuur toestande aan
die westekant van die eiland. Hierdie studie bepaal ook die fyn-skaal (e.g.
binne-terrein) en groot-skaal (e.g. oor die eiland) variasie patrone van A.
selago (morfologie, fenologie, en epifiet lading) oor Marion Eiland. Die hoogte
gradiënt en klimaat blootstelling aan verskillende kante van die eiland is
gebruik om die waarskynlike effekte van klimaats-geassosieerde omgewings verandering op die dominante deel van die felfield habitat te verstaan. Daar is
gevind dat terrein spesifieke prosesse die ruimtelike struktuur van A. selago
se klein-skaal eienskappe bepaal. Groot-skaalse waarnemings dui egter ’n
sterk antwoord van A. selago eienskappe op die hoogte gradiënt en aan
verskillende kante van die eiland. Azorella selago morfologiese eienskappe
(e.g. plant- en blaar grootte) is gevind om meer te reageer op verskille tussen
oostelike en westelike kante van die eiland as op die hoogte gradiënt.
Azorella selago mikromorfologiese eienskappe (e.g. blaar trigome en stomata
digtheid) is ook gevind om meer te reageer op omgewings blootstelling tussen
verskillende kante van die eiland as op die hoogte gradiënt. Verskille in A.
selago epifiet digtheid (e.g. Agrostis magellanica) en fenologie het egter
mikroklimaat temperature gevolg, in dat beide meer gereageer het op die
hoogte gradiënt as eiland-kant verskille. Hierdie resultate voorspel dus dat dit
waarskynlik is dat A. selago van Marion Eiland morfologies redelik
terugspringend sal wees ten opsigte van matige klimaatsverandering, al mag
dit uitgekompeteer word deur die epifitiese gras, Agrostis magellanica by lae
hoogtes en aan die oostekant van die eiland. Hierdie resultate dui ook dat
verwarming van Marion Eiland se klimaat ’n vervroeging van fenologiese
prosesse mag hê, veral by lae hoogtes en aan die oostekant van die eiland.
Dus word dit verwag dat Azorella selago by lae hoogtes en aan die oostekant
van Marion Eiland om meer simptome van klimaatsverandering (e.g.
verwarming) te dui. Dit word ook voorspel dat Azorella selago opwaarts teen
die hoogte gradiënt sal beweeg in reaksie tot verwarming.
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Growth, feeding and sex change in the sequential protandric shrimp Nauticaris marionis Bate 1888 at the Prince Edward Islands (Southern Ocean)Vumazonke, Lukhanyiso Unam January 2005 (has links)
Demographic parameters and the general biology of the subantarctic shrimp Nauticaris marionis from the Prince Edward Islands were investigated. The carapace length is the most accurate indicator of body size and it was confirmed that N. marionis is a partially protandric hermaphrodite. Gravid females of N. marionis observed mainly in March with negligible hatching persisting until April/May. The majority of juveniles develop into males. Juveniles are characterised by an appendage on the endopodite of the first pleopod called the appendix interna or a.i.1. Juveniles that develop into males do so by growing a further appendage on the endopodite of the second pleopod. This appendage characterises males and is called the appendix masculina (or a.m.). Juveniles may develop directly into primary females through the development of an ovary and the loss of the a.i.1. The sequence differs among individuals, with some developing the ovary before losing the a.i.1 and others losing the a.i.1 first. Loss of the a.i.1 appears to be by shedding during a single moult, rather than by atrophy. Females can also develop by an alternative route as secondary females. Such animals first become males with an a.m. and then develop an ovary, thus forming an intermediate form called a tertium quid, or “third thing”. Again, there are two forms of tertium quid. Tertia quae a have the a.m. as well as the a.i.1. Tertia quae b have the a.m. in combination with an ovary but no a.i.1. Either form of tertium quid can develop into a secondary female through loss of the a.m., and in the case of the tertium quid a, loss of the a.i.1. It is unclear whether sexual differentiation occurs in the plankton or just after N. marionis settles on the benthos. The results of gut content analysis suggest that N. marionis is an opportunistic feeder, preying on a variety of prey with a preference for detritus, benthic amphipods and gastropods. Cannibalism of conspecific pleopods by large individuals of N. marionis occurred mostly in females, particularly in incubation containers. Cannibalism also occurs in males, and its occurrence depends on individual size, not gender. No diel patterns were observed in the feeding activity of N. marionis. In situ daily rations of males (carapace length <7mm) and females (>7mm) were equivalent to ≈10% and ≈5% of body dry weight, respectively. The von Bertalanffy growth curve parameters were empirically identified, by cohort analysis of data collected during 4 years, as K = 0.22239/year, L[subscript]∞ = 14.05789mm, t₀ = -0.05174, L₀ = 0.16083mm. N. marionis can survive up to seven years under natural conditions.
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Phylogeny of Ameronothroidea in the south polar region and the phylogeography of selcted species on sub-antarctic Marion IslandMortimer, Elizabeth 03 1900 (has links)
Thesis (DPhil)--University of Stellenbosch, 2008. / ENGLISH ABSTRACT: Sub-Antarctic islands represent the only mid to high latitude terrestrial biomes in the Southern Hemisphere. These
islands have various geological origins and histories, well-preserved terrestrial ecosystems and high levels of
species endemism. In an attempt to understand the evolution and biogeography of terrestrial taxa in the South
Polar Region, the first broad-scale molecular phylogeny was constructed for the unique terrestrial group, the
ameronothroid mites (genus Halozetes (Oribatida)), collected from sub-Antarctic and Maritime Antarctic localities.
Phylogenetic analyses based on a combined mitochondrial (cytochrome oxidase subunit I (COI)) and nuclear
(histone-3 (H3)) sequence dataset indicated that the evolution of these mites were habitat specific (i.e. intertidal,
supralittoral and terrestrial). Notwithstanding criticisms levelled against a molecular clock, the mites were
evolutionary young (<10myo), contrary to their status as an ancient group predating Gondwana fragmentation.
Biogeographic analyses indicated a complex pattern mainly sculpted by multiple independent dispersal events
across the Antarctic Polar Frontal Zone similar to previous findings for other marine and terrestrial taxa. Also, the
molecular phylogeny displayed considerable discourse with contemporary taxonomy suggesting the need for
taxonomic revisions and reassessment of morphological characters. Sub-Antarctic Marion Island, the larger of the
two islands comprising the Prince Edward Island archipelago (PEI), has experienced extensive glaciation and
volcanism. To assess the impact of historical events (volcanism (including recent eruptions) and glaciation) and
contemporary mechanisms (gene flow) on the genetic spatial distribution of species from Marion Island, two mite
species namely Eupodes minutus (Prostigmata) and Halozetes fulvus (Oribatida) as well as a single plant species,
Azorella selago (Apiaceae), were selected as model organisms. For independent phylogeographic analyses,
mitochondrial sequence data (COI) were obtained for both mite species, while chloroplast sequence (trnH-psbA)
and amplified fragment length polymorphism (AFLP) data were generated for the cushion plant, A. selago. Since
A. selago is typified by two growth forms namely discrete cushions and continuous mats, it was essential to
examine the growth dynamics prior to phylogeographic analyses. The sequence and fragment data indicated that
both mite and plant species were significantly substructured across Marion Island. Manual comparisons indicated
unique populations on the western (Kaalkoppie for H. fulvus, La Grange Kop for E. minutus and Mixed Pickle for
A. selago), eastern (Bullard Beach for H. fulvus and Kildalkey Bay for E. minutus), northern (Middelman and Long
Ridge for H. fulvus) and southern side (Grey Headed for H. fulvus and Watertunnel for A. selago) of the island.
Importantly, the western side had unique localities for all species. Interestingly, based on the H. fulvus data, the
western populations were relatively young, characterized by high migration rates, small effective (female)
population sizes with no isolation-by-distance. The opposite scenario was found for the eastern populations. This
spatial genetic structure described for species on Marion Island can be ascribed to both historical events and
environmental conditions. These areas with their unique genetic composition are of special conservational
concern; consequently this research will contribute to an active management plan for PEI, South Africa’s only
Special Nature Reserve. / AFRIKAANSE OPSOMMING: Sub-Antarktiese eilande verteenwoordig die enigste terrestriële bioom in die middel tot hoër breedtegrades van
die Suidelike Halfrond. Hierdie eilande besit ‘n verskeidenheid van geologiese oorspronge en geskiedenisse,
goed-bewaarde terrestriële ekosisteme en hoë vlakke van endemisme. In ‘n poging om die evolusie en
biogeografie van terrestriële taksa in die Suid Pool Area te verstaan, is die eerste grootskaalse molekulêre
filogenie saamgestel vir ‘n unieke terrestriële groep, die ameronothoïed miete (genus Halozetes (Oribatida:
Ameronothroidea)), vanaf menigte sub-Antarktiese en Maritime Antarktiese lokaliteite. Filogenetiese analises
gebaseer op die saamgestelde mitochondriale (sitokroom oksidase subeenheid I (COI)) en nukluêre (histoon-3
(H3)) basispaarvolgordes het aangedui dat die evolusie van hierdie miete habitat spesifiek is (m.a.w inter-gety,
supralitoraal en terrestrieël). Ongeag die kritiek teenoor ‘n molekulêre klok, is hierdie miete evolusionêr jonk
(<10mjo), wat teenstrydig is met hulle status as ‘n antieke groep wat terugdateer voor Gondwana fragmentasie.
Biogeografiese analises het ‘n komplekse patroon aangedui wat grotendeels gekarakteriseer word deur menigte
onafhanklike verspreidingsgebeurtenisse bo-oor die Antarktiese Polêre Frontale Zone, wat ooreenstemmend is
met vorige bevindinge vir ander mariene en terrestriële taksa. Die molekulêre filogenie het ook aansienlik verskil
van die tradisionele taksonomie, dus is taksonomiese aanpassings en herklassifisering van morfologiese
karakters noodsaaklik. Sub-Antarktiese Marion Eiland, die groter eiland van die Prins Edward eilandgroep (PEI),
het uitermate glasiasie en vulkanisme ondervind. Om die impak van historiese gebeurtenisse (vulkanisme
(insluitend onlangse uitbarstings) en glasiasie) en kontemporêre meganismes (geenvloei) op die genetiesgespasieërde
verspreiding van spesies vanaf Marion Eiland te bepaal, was twee mietspesies naamlik Eupodes
minutus (Prostigmata) en Halozetes fulvus (Oribatida) asook ‘n enkele plantspesie, Azorella selago (Apiaceae),
gekies as model organismes. Vir onafhanklike filogeografiese analises, was die mitochondriale basispaarvolgorde
(COI) vir beide mietspesies bepaal, terwyl chloroplast basispaarvolgorde (trnH-psbA) asook geamplifiseerde
fragmentlengte polimorfisme (AFLP) data gegenereer was vir die kussingplant, A. selago. Aangesien A. selago
gekenmerk word deur twee groeivorme, naamlik diskrete kussings en aaneenlopende matte, was dit noodsaaklik
om eers die groeidinamika van die plant te ondersoek alvorens ‘n filogeografiese studie kon geskied. Die
basispaarvolgordebepalings en fragmentdata het aangedui dat beide mietspesies sowel as die plantspesie
betekenisvolle substruktuur vertoon regoor Marion Eiland. Informele vergelykings het unieke populasies aangedui
op die westelike (Kaalkoppie vir H. fulvus, La Grange Kop vir E. minutus en Mixed Pickle vir A. selago), oostelike
(Bullardstrand vir H. fulvus en Kildalkeybaai vir E. minutus), noordelike (Middelman en Long Ridge vir H. fulvus) en
suidelike kant (Grey Headed vir H. fulvus en Watertunnel vir A. selago) van die eiland. Die westelike kant besit
dus unieke lokaliteite vir al die spesies. Interressantheidhalwe het die H. fulvus data getoon dat die westelike
populasies relatief jonk is en gekarakteriseer word deur hoë migrasiesyfers en klein effektiewe (vroulike)
populasiegroottes met geen isolasie-oor-afstand nie. Die resultate vir die populasies aan die oostelike kant van die
Marion Eiland was presies teenoorgesteld. Dié beskryfde substruktuur vir die spesies op Marion Eiland is
afkomstig van beide historiese gebeurtenisse asook omgewingstoestande. Hierdie areas met hul unieke genetiese samestelling, is belangrik vir natuurbewaring. Hierdie navorsing sal bydra tot die bestuursriglyne van PEI, Suid
Afrika se enigste Spesiale Natuurreservaat.
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Out in the cold : science and environment in the history of South Africa’s involvement in the sub-Antarctic and Antarctic in the twentieth centuryVan der Watt, Susanna Maria Elizabeth (Lize-Marie) 03 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This study addresses a little-known but important part of South Africa’s history: its involvement with the sub-Antarctic and Antarctic in the twentieth century. It has a three-fold approach. Firstly, it provides insight into the motives driving South Africa’s investment in the region, from the first call for a South African Antarctic expedition in 1919 to the post-apartheid recommitment to the South African Antarctic Programme. Interrogating of the reasons behind South Africa’s activities in this region – including those that failed –throws into relief broader issues about how and where South Africa saw itself in the geopolitical order. As such, this dissertation is situated within a body of Antarctic scholarship that seeks to subvert the prevailing homogenising narrative of the continent as simply the preserve of scientists and heroes. In particular, it investigates how tropes of imperialism and nationalism functioned in these remote corners of the world. Secondly, this dissertation investigates how changing perceptions of the extreme environment of Antarctica, and specifically the Prince Edward Islands, can add to our understanding of environmental history. It also shows how the values projected onto and invested in the environment as ‘nature’ changed over time. Thirdly, it takes into account the humans that were South Africa’s presence in the region and how the underlying patterns in the fabric of South African society, including race and gender, crystalized on the Antarctic continent. / AFRIKAANSE OPSOMMING: Hierdie studie is gerig op ʼn minder bekende, maar belangrike aspek van Suid-Afrika se geskiedenis: die land se betrokkenheid by die sub-Antarktiese gebied en Antarktika in die twintigste eeu. Die studie volg van ʼn drie-ledige benadering. Eerstens, verskaf dit insig in die dryfvere agter Suid-Afrika se investering in die streek – vanaf die eerste beroep op ʼn Suid-Afrikaanse Antarktiese ekspedisie in 1919, tot die post-apartheid regering se herverbintenis tot die Suid-Afrikaanse Antarktiese program. Die ondersoek na die redes vir Suid-Afrika se aktiwiteite in die streek – insluitend dié wat misluk het – bring breër kwessies oor Suid-Afrika se selfbeskouing in die wêreld se geopolitieke orde, na vore. Hierdie studie word binne ʼn kritiese raamwerk van navorsing oor Antarktika geplaas. Dié raamwerk streef daarna om die oorheersende homogene beeld van die kontinent as die eksklusiewe grondgebied van wetenskaplikes en helde, onder die soeklig te stel. In die besonder stel dit ondersoek in na hoe imperialisme en nasionalisme in hierdie verafgeleë uithoeke van die aarde versinnebeeld is. Tweedens, ondersoek hierdie studie hoe veranderende persepsies van Antarktika - en veral die Prins Edward eilande - se uiterste omgewing tot ons begrip van omgewingsgeskiedenis kan bydra. Dit dui ook aan die mate waartoe bestaande waardes wat op die omgewing as ‘natuur’ geprojekteer en gevestig is, mettertyd verander het. Die derde benadering neem die mense wat Suid-Afrika se teenwoordigheid verpersoonlik het in aanmerking - en hoe die onderliggende patrone in die Suid-Afrikaanse samelewing, insluitend ras en geslag, op die Antarktiese kontinent uitgekristalliseer het.
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A demographic comparison of two elephant seal populationsMcMahon, Clive Reginald 30 June 2005 (has links)
The demography of two elephant seal populations was examined and compared. This was done to investigate the reasons for the observed decreases in populations at Marion and Macquarie islands. While a well-established demographic programme had been in place at Marion Island since the 1980's (see Pistorius et al. (l999a) for a review) one had to be established at Macquarie Island. A long-term demographic programme was initiated at Macquarie Island in 1993 and hot brands were used to mark seals. Hot-iron branding was a rapid and reliable method of permanently identifying elephant seals that did not prejudice survival and did not appear to cause undue stress (in the short-term). Neither branding nor handling showed any long-term effects as measured by survival after one year. From the inter-island comparison of survivorship, age at first breeding and wean mass I concluded that the observed decreases in elephant seal numbers between the I 950s and 1990s in the Pacific and Indian Ocean sectors were driven by resource limitation in the Southern Ocean. A conglomerate of factors including local predation by killer whales and intra-specific resource competition was postulated as a cause for the inter-island (regional) differences in population trends. Presently it appears that per capita more resources are available to the Marion Island population than are available to the Macquarie Island population. The vital rates that had the greatest impact (elasticity) on fitness (population growth) for all populations i.e. Marion Island, Macquarie Island and South Georgia, were, in order of importance: (I) juvenile survival, (2) adult survival, (3) adult fecundity and (4) juvenile fecundity. At Marion Island juvenile and adult survival contributed equally to the fitness of the population while at Macquarie Island and at South Georgia Island juvenile survival was more important than adult survival in determining population fitness. The global population of elephant seals in 200 I was estimated at approximately 738 772 which represents an increase of I I % from the last world estimate (664 000). It seems clear from the evidence presented and reviewed here that the present changes in seal populations, unlike the period of direct exploitation in the 19th and 20th centuries, are neither a consequence of direct human interactions nor present-day commercial activities. While the significance of inter-specific competition between elephant seals and other Antarctic predators remain largely unknown or quantified, it would seem prudent that these relationships be studied. This is because resource competitors (toothed whales) have been increasing in number since the cessation of commercial whaling. Even though elephant seals are considered the most studied of all pinnipeds (Ling&Bryden, 1992) much remains to be learnt. Foremost are to gain a clear understanding of the in situ, diet of elephant seals and to assess the role pathogens play in the regulation of seal populations. In addition to these studies it is also important that the current long-term monitoring programmes at Marion and Macquarie islands continue, as they provide valuable base line information on the fate of elephant seal populations. / Thesis (PhD (Zoology))--University of Pretoria, 2005. / Zoology and Entomology / unrestricted
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Untagged southern elephant seals at Marion Island : origin and demographic consequencesOosthuizen, Wessel Christiaan 15 July 2010 (has links)
Please read the abstract in the section 00front of this document. / Dissertation (MSc)--University of Pretoria, 2010. / Zoology and Entomology / unrestricted
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