No description available.

The pre-metamorphic behaviors and settlement preferences of larvae can have significant effects on the success of adult invertebrates. This study describes various aspects of pre-metamorphic and post-metamorphic life stages of the bryozoan

Along the shores of the Northern hemisphere Fucus (Phaeophyceae) species are a prominent presence, providing substrate, shelter, and food for many species. Fucus evanescens, a non-indigenous species (NIS) in Sweden, and F. radicans, a recently described species that so far has only been found inside the species poor Baltic Sea, are the focus of this thesis. Interactions with enemies (e.g. predators, herbivores, parasites) have been shown to play a role in the success of NIS. The low consumption of Fucus evanescens by the generalist gastropod Littorina littorea in Sweden was found to depend on high levels of chemical defense in the introduced population, not the failure of the herbivore to recognize F. evanescens as suitable food. A survey of the relative abundance of F. radicans and F. vesiculosus and the most common associated fauna along the Swedish Bothnian Sea coast showed that F. radicans and F. vesiculosus are equally abundant throughout the range of F. radicans. The most common associated fauna were found to be more abundant on F. radicans compared to F. vesiculosus.  In Sweden, where F. radicans had lower levels of defense chemicals than F. vesiculosus, F. radicans was grazed more than F. vesiculosus in bioassays. This could, together with other factors, influence the range of F. radicans. Fucus radicans and F. vesiculosus are closely related, recently separated, and growing sympatrically, therefore, possible reproductive barriers between F. radicans and F. vesiculosus were studied. In Estonia F. radicans and F. vesiculosus reproduces at different times of the year. No such clear reproductive barrier was found between the two species in Sweden where they reproduce at the same time and fertilization success and germling survival were the same for hybrids as for F. vesiculosus. Since the high clonality of F. radicans means that the gentic diversity in F. radicans populations is low I investigated how genetic diversity translates to phenotypic diversity in nine traits. Phlorotannin levels, recovery after desiccation, and recovery after freezing showed inherited variation, while the other six traits showed no variation related to genetic diversity. Phenotypic variation in populations of F. radicans will be higher in populations with higher genetic diversity and this might be beneficial to the community. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Accepted.</p>

Concern for the severe loss of biodiversity of grassland species is often voiced. Plantation forestry is known to cause extensive and long lasting disturbance of the natural environment in particular in areas such as the mountain grassland of the Drakensberg escarpment. The survey was conducted in the Graskop area on sites within pine plantations along the Treur River bordering the Blyde River Nature Reserve. The results showed that restoration of plant species biodiversity through natural succession, on cleared plantation sites, required periods longer than seven years and that the regeneration of a great many of the indigenous forb species remained uncertain. Two survey areas were selected and within each survey area, sampling sites were selected to represent three categories of vegetation namely, undisturbed grassland and sites where pine trees had been removed three and seven years previously. Samples of plants were collected from each of these sampling sites. Analysis by means of a classification technique determined the species composition of the disturbed sites in relation to that of the intact grassland. Wheel point surveys were also carried out on these sites to provided information on the vegetation cover, as well as the degree of species regeneration on each site. The variation in vegetation composition of the various plots was ana lysed by means of Detrended Correspondence Analysis (DCA) and Two-Way Indicator Species Analysis (TWINSPAN). The results showed three distinct species assemblages which corresponded with the three categories of sampling sites. Also that the indigenous forbs species comprised 68% of all the sampled species most of which had failed to regenerate in either the three or seven year cleared plots. The most successful grass species in establishing and persisting in all sites were, Eragrostis curvula and Loudetia simplex. The fern, Pteridium aquilinum had a high prevalence on the disturbed grassland plots and the threat of its invasion of these habitats is compounded by the physical disturbance which eradication methods cause. Planning for grassland restoration involves cognizance of the complexity of grassland ecology, the influence of a multiplicity of environmental factors and the proximity of donor sites to the disturbed areas. Applying international restoration techniques used in grasslands of different origins to those of South African landscapes could result in disappointing and costly efforts. At best any attempt at managing grassland diversity should be preceded by an holistic investigation into the environmental conditions particular to the specific terrain and thereafter maintaining a conservative approach of allowing natural succession. The threat of invasive exotic species should be integral to conserving the integrity of the remaining intact natural grasslands in South Africa. It is acknowledged that in this study regeneration of grassland species on plantation sites cleared of pine trees three and seven years previously does not include a long time span such as needed for succession to take place but is useful in showing a trend in species re-colonization to resemble the vegetation of intact grassland, as well as highlighting the absence of a great number of indigenous forb species. Copyright / Dissertation (MInstAgrar)--University of Pretoria, 2012. / Geography, Geoinformatics and Meteorology / Unrestricted

Thesis (PhD (Botany and Zoology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Although the impacts of biological invasions are widely appreciated, a bias exists in research effort to post‐dispersal processes because of the difficulties of measuring propagule pressure and the detecting of newly established species. Here the Antarctic is used as a model system in which to quantify the initial dispersal of alien species and investigate the factors that contribute to the establishment and range dynamics of alien species once they have arrived in the region. Human movements are known to transport alien species into the Antarctic, some of which have successfully established and had wide ranging consequences in recipient ecosystems. Considering terrestrial flora, this research found that over 700 seeds from 99 taxa, including some species known to be invasive, are transported into the Antarctic each year in association with South African National Antarctic Programme (SANAP) passenger luggage and cargo. The first ever assessment of propagule drop‐off indicated that 30‐50% of these propagules will enter the recipient environment. Further results suggested that the construction of the British Antarctic Survey Halley VI station will facilitate the transport of over 5000 seeds from 34 taxa into the region, making this a significant pathway for introductions. Propagule pressure due to SANAP logistics is also considerable for marine species. Fouling assemblages on the external hull surfaces of the SANAP resupply vessel, the SA Agulhas, form only once the vessel’s anti‐fouling paint has been damaged by travel through sea ice and are characterised by low diversity. Ice scour prevents fouling assemblages from being transported to the Antarctic continent, but assemblages remain largely intact when travelling to sub‐Antarctic Islands. In the sea‐chests of the vessel populations of a known invasive, Mytilus galloprovincialis, were found with some individuals having survived transportation to the Antarctic region on multiple occasions. Once species have overcome initial dispersal barriers, they face further ecological and physiological challenges in order to establish in the recipient region. The parasitoid wasp Aphidius matricariae was first recorded on Marion Island in 2001. Surveys around the island show that adult abundance and the frequency of aphid parasitism are highest adjacent to a common anchor point of the SA Agulhas and decline away from this region. Genetic diversity was low, suggesting that the population was established from a single introduction. This highlights that high propagule pressure is not necessary for successful establishment of introduced invertebrates. Another species that has overcome the dispersal barrier is the terrestrial slug Deroceras panormitanum, which was introduced to Marion Island in the 1970’s and has since spread throughout much of the coastal habitat of the island. For this species range limits are set by intolerance of low temperature and salinity, and abundance structure is characterized by patches and gaps which are associated with this species inability to tolerate dry conditions. To prevent further alien introductions in the region, targeted management of high risk pathways is required. In addition, increased vigilance is needed to detect and manage newly established aliens before their ranges expand. / AFRIKAANSE OPSOMMING: Alhoewel die impak van biologiese indringings in die breë waardeer word, bestaan daar vooroordeel in navorsingspogings ten opsigte van na‐verspreidingsprosesse, weens die moeilikhede om verspreidingseenheid druk te meet en in die opsporing van nuut gevestigde spesies. Hier word die Antarktiese streek as ‘n model sisteem gebruik waarin die aanvanklike verspreiding van uitheemse spesies gekwantifiseer kan word en om die faktore wat bydrae tot die vestiging en grens dinamika van uitheemse spesies te ondersoek, wanneer hulle in ’n streek aangekom het. Menslike bewegings is bekend daarvoor om uitheemse spesies na die Antarktiek te vervoer, sommige waarvan suksesvol gevestig het en omvattende gevolge in die ontvanger ekosisteme gehad het. Aangaande terrestriële flora het hierdie navorsing gevind dat oor die 700 sade van 99 taxa, insluitende sommige spesies wat bekend is om indringend te wees, jaarliks na die Antarktiek vervoer word in assosiasie met die Suid Afrikaanse Nasionale Antarktiese Program (SANAP) se bagasie en vrag. Die eerste waardebepaling van verspreidingseenheid afgooi het aangedui dat 30‐50% van hierdie verspreidingseenhede die ontvanger omgewing sal binnedring. Verdere resultate het voorgestel dat die konstruksie van die Britse Antarktiese Opname Halley VI stasie die vervoer van 5000 sade van 34 taxa sal fasiliteer die streek in, wat dit ’n betekenisvolle weg maak vir indringings. Verspreidingseenheid druk is ook, as gevolg van die SANAP logistiek, aanmerklik vir mariene spesies. Vuilgoed versamelings op die eksterne omhullende oppervlaktes van die SANAP her‐voorsieningsvaartuig, die SA Agulhas, vorm wanneer die vaartuig se anti‐vuilgoed verf beskadig is met reis deur see‐ys en word gekenmerk deur lae diversiteit. Ys skuring voorkom dat vuilgoed versamelings vervoer word na die Antarktiese kontinent, maar versamelings bly grootliks vasgeheg wanneer na sub‐Antarktiese eilande gereis word. Populasies van ’n welbekende indringer, Mytilus galloprovincialis, is gevind in die see‐storingsarea van die vaartuig, met sommige individue wat die vervoering na die Antarktiese streek oorleef het op verskeie geleenthede. Wanneer spesies die aanvanklike verspreidingshindernisse oorkom het, staar hulle verdere ekologies en fisiologiese uitdagings in die gesig ten einde in die ontvanger streek te vestig. Die parasitiese wespe Aphidius matricariae is vir die eerste keer op Marion aangeteken in 2001. Opnames om die eiland toon dat volwasse oorvloed en die frekwensie van plantluis parasitisme die hoogste is aangrensend die algemene ankerpunt van die SA Agulhas en afneem weg van die omgewing af. Genetiese diversiteit was laag, wat voorstel dat die populasie gevestig het van ’n enkele bekendstelling. Dit lig uit dat hoë verspreidingseenheid druk nie nodig is vir die suksesvolle vestiging van bekendgestelde invertebrata nie. ‘n Ander spesie wat die verspreidingshindernisse oorkom het is die landslak Deroceras panormitanum wat in die 1970’s op Marion Eiland bekendgestel is en wat sedertdien versprei het oor meeste van die kushabitat van die eiland. Vir hierdie spesie word grens limiete vasgestel deur onverdraagsaamheid vir lae temperature en saliniteit en die oorvloedstruktuur word gekenmerk deur laslappe en gapings wat geassosieer word met die spesie se onvermoë om droë kondisies te hanteer. Om verdere uitheemse bekendstellings in die streek te voorkom, word geteikende bestuur van hoë risiko weë vereis. Toenemende waaksamheid is bykomend nodig vir die opsporing en bestuur van nuutgevestigde uitheemse spesies voordat hulle grense verbreed.

<p>Along the coast of temperate oceans brown algae of the genus <em>Fucus</em> form dense stands on rocky shores and are keystone species of the coastal ecosystem. These large seaweeds are perennial and function as substrate for many sessile marine organisms, provide shelter for fauna and juvenile fish, and are food source. A number of abiotic (e.g. wave-exposure, salinity and substrate) and biotic (e.g. herbivory and competition) factors structures these communities and determines the abundance and composition of fucoids at each specific site. Earlier studies have shown that herbivores may reduce growth of fucoids, thus affecting their distribution, and at high densities eliminate the species from previously occupied sites. In my thesis I focused on investigating herbivore-seaweed interactions and whether such interactions could influence the geographical range limits of <em>Fucus </em>species. A set of laboratory bioassays and a field survey were conducted (1) to investigate the resistance to grazing by a generalist gastropod<em> </em>between introduced (to Sweden) and native (Iceland) <em>Fucus evanescens </em>(Paper I),  (2) to study the distribution pattern of <em>F. radicans</em> and <em>F. vesiculosus</em> along the Swedish coast and specifically the southern limit of <em>F. radicans</em>, (3) to examine the abundance of herbivores in these two species, and (4) to test the hypothesis that <em>Idotea</em> <em>baltica</em> may contribute to restrict <em>F. radicans</em> to the Bothnian Sea (objective 2-4; Paper II). <em>Fucus evanescens</em>, a species that was introduced to the Swedish coast about 100 years ago, was found to be more resistant to grazing by <em>L. littorea</em> compared to <em>F. evanescens</em> from the native Icelandic populations.  It was also shown to contain a higher amount of phlorotannins; a putative chemical defence to herbivory. This indicates that development of resistance to herbivory could be important for a successful introduction and survival in a new range. No gradual change in the proportion, measured as % cover of either <em>F. radicans</em> or <em>F. vesiculosus </em>was found<em> </em>inside the range of <em>F. radicans </em>and its southernmost limit was abrupt without any corresponding abrupt change in any abiotic factor, e.g. salinity. Herbivores, i.e. <em>Idotea </em>spp<em>.</em>, <em>Gammarus </em>spp. and <em>Theodoxus fluviatils</em> were found to be more abundant in <em>F. radicans</em> than in <em>F. vesiculosus </em>thalli indicating a habitat preference for <em>F. radicans</em>.  Further, <em>Idotea baltica</em>, whose range only overlaps with that of <em>F. radicans</em> in the south, was shown to prefer <em>F. radicans </em>over<em> F. vesiculosus, </em>possibly due to its lower content of phlorotannins<em>. </em>Based on these findings I propose that <em>Idotea</em> species may contribute in restricting the southern range of <em>F. radicans</em>, although further experiments, especially regarding competition with the larger <em>F. vesiculosus</em> need to be performed. In conclusion, biotic interactions e.g. the ability of to resist herbivore grazing by e.g. high phlorotannin content or having a structure less attractive as habitat to herbivores may be of importance in determining the geographic range of fucoids.</p> / <p>Längs kusterna i de tempererade haven bildar brunalger av släktet <em>Fucus</em> täta bestånd på klippiga stränder och är ofta nyckelarter i kustekosystemen. Dessa tångarter är fleråriga och utgör substrat för många fastsittande organismer, ger skydd åt små rörliga djur och fiskyngel, samt utgör föda för betare så som gastropoder, amphipoder och isopoder. Faktorer som vågexponering, bottentyp, salthalt, näringshalter, bete och konkurrens strukturerar tångsamhällen och avgör hur vanlig varje tångart är på en viss lokal. I min avhandling har jag fokuserat på interaktionen mellan betare och tång, samt hur viktig denna interaktion är för att avgöra den geografiska utbredningen av tångarter. Tidigare studier har visat att betare kan minska tillväxten hos tång och på så sätt påverka dess utbredning. I höga densiteter kan de beta ner hela bestånd av tång så att den försvinner från lokaler där de tidigare vuxit. Resistens mot bete hos <em>Fucus evanescens</em>, ishavstång, som är introducerad till Skagerrak, Kattegat och sydvästra Östersjön och inhemsk i norra Atlanten och norra Stilla Havet undersöktes i betesförsök (Artikel I). En betare, generalisten <em>Littorina littorea</em>, strandsnäcka, som är inhemsk i Sverige, dit <em>F. evanescens</em> har introducerats, föredrog att äta <em>F. evanescens</em> från Island där den är inhemsk, framför <em>F. evanescens</em> från Sverige. Det här skulle kunna tyda på att ett välutvecklat försvar är viktigt för att alger som blir introducerade till nya områden ska kunna etablera sig i det nya området. Jag undersökte även utbredningen av den nyligen beskrivna tångarten <em>Fucus radicans</em>, smaltång (Artikel II). Resistensen mot betare hos <em>F. radicans</em> jämfördes med resistensen mot bete hos <em>F. vesiculosus</em>, blåstång, som växer tillsammans med <em>F. radicans</em>, genom att undersöka preferensen mellan de två arterna hos <em>Idotea baltica</em>, tånggråsugga (Artikel II). Det fanns ingen gradient i förekomsten av <em>F. radicans</em> eller <em>F. vesiculosus</em> inom <em>F. radicans</em> utbredningsområde. Istället observerades en ganska abrupt gräns för utbredningen av <em>F. radicans</em> i söder. Eftersom <em>I. baltica</em>, vars utbredning överlappar <em>F. radicans</em> utbredning i söder, föredrog att äta <em>F. radicans</em> framför <em>F. vesiculosus,</em> skulle <em>F. radicans</em> utbredning kunna påverkas av <em>I. baltica</em>. Både <em>I. baltica</em> och två andra betare, <em>Gammarus </em>spp. och <em>Theodoxus fluviatilis</em>, var vanligare i <em>F. radicans</em> än i <em>F. vesiculosus </em>i plantor insamlade i fält. Det innebär att de vanligaste betarna, även i fält, föredrar att uppehålla sig i <em>F. radicans</em> och antagligen konsumerar mer av <em>F. radicans</em>. Slutsatsen från de båda studierna är att betare och tångens försvar mot bete har potentialen att påverka utbredning av olika tångarter.</p>

Along the coast of temperate oceans brown algae of the genus Fucus form dense stands on rocky shores and are keystone species of the coastal ecosystem. These large seaweeds are perennial and function as substrate for many sessile marine organisms, provide shelter for fauna and juvenile fish, and are food source. A number of abiotic (e.g. wave-exposure, salinity and substrate) and biotic (e.g. herbivory and competition) factors structures these communities and determines the abundance and composition of fucoids at each specific site. Earlier studies have shown that herbivores may reduce growth of fucoids, thus affecting their distribution, and at high densities eliminate the species from previously occupied sites. In my thesis I focused on investigating herbivore-seaweed interactions and whether such interactions could influence the geographical range limits of Fucus species. A set of laboratory bioassays and a field survey were conducted (1) to investigate the resistance to grazing by a generalist gastropod between introduced (to Sweden) and native (Iceland) Fucus evanescens (Paper I),  (2) to study the distribution pattern of F. radicans and F. vesiculosus along the Swedish coast and specifically the southern limit of F. radicans, (3) to examine the abundance of herbivores in these two species, and (4) to test the hypothesis that Idotea baltica may contribute to restrict F. radicans to the Bothnian Sea (objective 2-4; Paper II). Fucus evanescens, a species that was introduced to the Swedish coast about 100 years ago, was found to be more resistant to grazing by L. littorea compared to F. evanescens from the native Icelandic populations.  It was also shown to contain a higher amount of phlorotannins; a putative chemical defence to herbivory. This indicates that development of resistance to herbivory could be important for a successful introduction and survival in a new range. No gradual change in the proportion, measured as % cover of either F. radicans or F. vesiculosus was found inside the range of F. radicans and its southernmost limit was abrupt without any corresponding abrupt change in any abiotic factor, e.g. salinity. Herbivores, i.e. Idotea spp., Gammarus spp. and Theodoxus fluviatils were found to be more abundant in F. radicans than in F. vesiculosus thalli indicating a habitat preference for F. radicans.  Further, Idotea baltica, whose range only overlaps with that of F. radicans in the south, was shown to prefer F. radicans over F. vesiculosus, possibly due to its lower content of phlorotannins. Based on these findings I propose that Idotea species may contribute in restricting the southern range of F. radicans, although further experiments, especially regarding competition with the larger F. vesiculosus need to be performed. In conclusion, biotic interactions e.g. the ability of to resist herbivore grazing by e.g. high phlorotannin content or having a structure less attractive as habitat to herbivores may be of importance in determining the geographic range of fucoids. / Längs kusterna i de tempererade haven bildar brunalger av släktet Fucus täta bestånd på klippiga stränder och är ofta nyckelarter i kustekosystemen. Dessa tångarter är fleråriga och utgör substrat för många fastsittande organismer, ger skydd åt små rörliga djur och fiskyngel, samt utgör föda för betare så som gastropoder, amphipoder och isopoder. Faktorer som vågexponering, bottentyp, salthalt, näringshalter, bete och konkurrens strukturerar tångsamhällen och avgör hur vanlig varje tångart är på en viss lokal. I min avhandling har jag fokuserat på interaktionen mellan betare och tång, samt hur viktig denna interaktion är för att avgöra den geografiska utbredningen av tångarter. Tidigare studier har visat att betare kan minska tillväxten hos tång och på så sätt påverka dess utbredning. I höga densiteter kan de beta ner hela bestånd av tång så att den försvinner från lokaler där de tidigare vuxit. Resistens mot bete hos Fucus evanescens, ishavstång, som är introducerad till Skagerrak, Kattegat och sydvästra Östersjön och inhemsk i norra Atlanten och norra Stilla Havet undersöktes i betesförsök (Artikel I). En betare, generalisten Littorina littorea, strandsnäcka, som är inhemsk i Sverige, dit F. evanescens har introducerats, föredrog att äta F. evanescens från Island där den är inhemsk, framför F. evanescens från Sverige. Det här skulle kunna tyda på att ett välutvecklat försvar är viktigt för att alger som blir introducerade till nya områden ska kunna etablera sig i det nya området. Jag undersökte även utbredningen av den nyligen beskrivna tångarten Fucus radicans, smaltång (Artikel II). Resistensen mot betare hos F. radicans jämfördes med resistensen mot bete hos F. vesiculosus, blåstång, som växer tillsammans med F. radicans, genom att undersöka preferensen mellan de två arterna hos Idotea baltica, tånggråsugga (Artikel II). Det fanns ingen gradient i förekomsten av F. radicans eller F. vesiculosus inom F. radicans utbredningsområde. Istället observerades en ganska abrupt gräns för utbredningen av F. radicans i söder. Eftersom I. baltica, vars utbredning överlappar F. radicans utbredning i söder, föredrog att äta F. radicans framför F. vesiculosus, skulle F. radicans utbredning kunna påverkas av I. baltica. Både I. baltica och två andra betare, Gammarus spp. och Theodoxus fluviatilis, var vanligare i F. radicans än i F. vesiculosus i plantor insamlade i fält. Det innebär att de vanligaste betarna, även i fält, föredrar att uppehålla sig i F. radicans och antagligen konsumerar mer av F. radicans. Slutsatsen från de båda studierna är att betare och tångens försvar mot bete har potentialen att påverka utbredning av olika tångarter.

The main theme of this thesis is the interactions of animals with the environment and each other. The thesis was written within the framework of a biomanipulation project “Pikeperch in Himmerfjärden”. With the aim to investigate possible trophic pit-falls, give the manipulation the best possible start, and find ways to monitor the progression of the manipulation. In Paper I the diet of the invader cladoceran Cercopagis pengoi is analysed with stable isotopes; conducted prior to stocking. C.pengoi has a preference for large copepods, indicating possible competition with fish. Paper II investigates the behavioural differences between pikeperch fingerlings reared in different environments (pond vs. tank). Results suggest that fish reared in semi-natural ponds are more likely to survive directly after stocking. In Paper III and IV, the diel vertical migrations (DVM) of copepods are in focus. In Paper III the migrations of two copepod species: Acartia spp. and Eurytemora affinis are studied over season and life stage. The amplitude of migration was found to increase with ontogeny for both species, indicating evasion of visual predators. Paper IV examines the varying migratory patterns of adult female E. affinis finding that these animals migrate more actively when feeding conditions deteriorate and growth decreases. The overall conclusions of the thesis are that behavioural, not only direct trophic interactions are key when studying ecosystems. / <p>At the time of the doctoraldefense, the following papers were unpublished and had a status asfollows: Paper2: In press. Paper 4: Manuscript.</p>

No

Research in the multidisciplinary science of ecotoxicology is crucial to assess injuries to ecosystem resources from chemical spills or other stressors used to support environmental decision-making. Established guidelines recommend the use of non-standard native species in toxicity investigations. This work focused on the use of native species for aquatic toxicity assessment to make more relevant conclusions on the potential for adverse biological effects to occur as a result to single chemical exposures or exposures to a complex mixture like oil. We apply these studies to investigate petroleum product impacts from the Deepwater Horizon incident and concerns for metal toxicity in estuarine environments using a new model organism. Data generated from comprehensive toxicity testing programs were used in the first probabilistic risk assessment of Deepwater Horizon oil toxicity highlighting a lack of appropriate data and representative phyla. Novel toxicity study methods and a stress-response index were developed and demonstrated sensitivity and success in using the starlet anemone in ecotoxicology studies. Swim performance was used as new method to investigate sublethal indicators of stress resulting in varied responses from sheepshead minnows and Florida pompano. These studies further our ability for better laboratory-to-field extrapolation and for decision-making. The use of native species and complex mixtures like oil presented novel challenges in conducting aquatic toxicity studies. Special emphasis is placed on the necessity to understand the appropriate laboratory conditions for native species not typically held in the laboratory and maintaining study parameters to obtain quality data for more accurate interpretation and replication.