Dissertation (PhD)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Within arthropods, inter-individual and inter-population variation is generally poorly explored for physiological parameters. Such physiological variability is important, as it can provide insight into the capacity for evolutionary adaptation and how animals may cope with anthropogenic climate change. Insect vectors of human and animal diseases, such as tsetse flies (Diptera, Glossinidae) which carry trypanosomes, are of particular interest. Predictions of tsetse fly (Glossina spp.) range expansion, possibly paralleled by increased disease occurrence, have been made under future climate scenarios. Moreover, since there are generally strong relationships between abiotic variables (e.g. temperature and moisture availability), population dynamics, distribution and abundance, determining the physiological mechanisms influencing such relationships has utility for predictive modelling of spatial and temporal changes in tsetse fly distributions. I investigated physiological variation among individuals and populations, focusing mainly on Glossina spp. but using other arthropods to address certain issues. Specifically, I show the following: i) metabolic rate is repeatable (intra-class correlation coefficient) within individuals, and may be influenced by several factors such as age, gender, body mass and pregnancy; ii) while metabolic rate is repeatable within individuals, it remains unaltered with acclimation to laboratory conditions from field collection; iii) within a population, metabolic rate-temperature relationships are surprisingly invariant among physiological states such as age, gender, feeding status, pregnancy and temperature acclimation; iv) the magnitude of the effect of temperature acclimation differs among traits, in that upper thermal tolerances respond less than lower thermal tolerances, while metabolic rate responds to heat but not to cold. Water loss rate is relatively unresponsive to either treatment; v) plasticity can account for most inter-population variation in physiological traits related to climatic stress resistance (e.g. thermotolerances and desiccation rates) in the natural environment; vi) adult physiological performance responds differently to developmental and adult acclimation, such that marked traitspecific variation occurs, and combinations of both developmental and adult plasticity can result in further alteration of adult performance. These results have implications for the evolution of stress resistance to abiotic factors in these and other arthropods. I conclude by discussing the potential physiological patterns linking population dynamics and abiotic factors, with particular reference to tsetse flies. / AFRIKAANSE OPSOMMING: Binne arthropoda, is tussen-individu en tussen-bevolking variasie in die algemeen sleg bestudeer vir fisiologiese parameters. Hierdie fisiologiese variasie is belangrik want dit kan insig gee in die mate van evolusionêre aanpassing en hoe diere antropogenies klimaatsverandering kan hanteer. Dit is veral belangrik in die geval van insekte wat mens- en diersiektes kan dra, soos tsetse vlieë (Diptera, Glossinidae) wat trypanosome oordra. In die geval van tsetse vlieë (Glossina spp.) is voorspellings vir verhoogde verspreiding, en gevolglik verhoogde siekte voorkoms, gemaak onder toekomstige voorkoms klimaat senario’s. Verder, aangesien daar in die algemeen sterk verwantskappe tussen abiotiese parameters (bv. temperatuur en water beskikbaarheid), bevolkingsdynamika, verspreiding en voorkoms is, is die bepaling van die fisiologiese meganisme, wat ‘n invloed het op hierdie verwantskappe, nuttig vir die voorspelling van tsetse oor spasie en tyd. Hier, met hoofsaaklik die gebruik van Glossina spp., maar ook ander arthropoda wanneer dit nodig is, word navorsing wat fisiologiese variasie tussen individue en bevolkings aanspreel voorgelê. Spesifiek, word dit gewys dat i) metaboliese tempo is herhaalbaar (intra-klas korrelasie koeffisient) binne individue, alhowel metaboliese tempo kan beinvloed word deur faktore soos ouderdom, geslag, liggaamsmassa en swangerskap, ii) terwyl metaboliese tempo binne individue herhaalbaar is, verander dit nie met akklimasie na laboratorium toestande vanaf versameling in die veld, iii) binne ‘n bevolking metaboliese tempo-temperatuur verwantskappe is verbasend eenders tussen fisiologiese toestande soos ouderdom, geslag, voeding staat, swangerskap en temperatuur akklimasie, iv) die grootte van die effek van temperatuur akklimasie verskil tussen eienskappe, en die boonste termiese limiete reageer minder as laer termiese limiete, terwyl metaboliese tempo reageer op hitte maar nie koue nie, en waterverlies tempo is relatief terughoudend tot enige temperatuur toestand, v) buigbaarheid kan die meeste van inter-bevolkingsvariasie in fisiologiese eienskappe van klimaatstres weerstandsvermoë (termiese toleransie en uitdrogingstempo) in die natuurlike omgewing verklaar, vi) volwasse fisiologiese prestasie reageer verskillend op ontwikkelende en volwasse akklimasie, soveel dat eienskap-spesifieke variasie kan voorkom, en ‘n kombinasie van beide ontwikkelende en volwasse buigbaarheid ‘n verskillende volwasse prestasie tot gevolg kan hê. Hierdie resultate het implikasies vir die evolusie van weerstandsvermoë tot abiotiese faktore in hierdie en ander arthropoda. Hierdie tesis word afgesluit met ‘n bespreeking van die moontlikke fisiologiese patrone wat bevolkingsdinamika en abiotiese faktore kan verbind, met ‘n fokus op tsetse vlieë.

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.

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: South Africa is known for its high marine invertebrate diversity but the evolutionary histories of these species are largely unknown. The present study contributes to the growing body of phylogeographic studies of southern African coastal species. The main aim is to better understand the colonization and diversification of South African barnacles. To investigate the phylogeographic pattern in the southern African volcano barnacle, Tetraclita serrata, 410 individuals from 20 sampling localities were analyzed. In addition, to understand the colonization and diversification patterns of South African barnacle species, nine taxa were included in a molecular phylogeny derived from the nuclear gene, 18S rRNA. With only a limited number of 18S sequences available on GenBank, a separate phylogenetic tree, for the mitochondrial gene, was constructed to determine whether the genus Tetraclita is monophyletic. Restricted gene flow in some geographical areas was hypothesized for T. serrata based on oceanic circulation patterns; known biogeographic regions; and features such as the Agulhas Bank, which has shaped the population genetic structure of several other South African marine organisms. The population genetic structure was investigated using the mitochondrial cytochrome oxidase subunit 1 (CO1) and nuclear internal transcribed spacer 1 (ITS1) genes. Phylogenetic and population genetic analyses of the CO1 gene revealed two distinct genetic clades with overlapping distributions. The nuclear ITS1 data performed on a subset of individuals drawn from both mtDNA clades revealed a single lineage. The pattern observed can be ascribed to a historical event that may have been responsible for the formation of allopatric lineages that have since come into secondary contact. On the other hand, the pattern observed may be as result of incomplete sorting of nDNA alleles, in which case, given that the two mtDNA clades are not geographically isolated, could be explained by selective pressures acting on the species due to ecological constraints. No clear phylogeographic structure was found within each of these clades and the direction of gene flow of T. serrata individuals can be linked to the oceanographic features found along the South African coast. In contrast to most other South African marine species studied to date, the haplotype network, mismatch distributions and time since expansion suggest that the effective population size of T. serrata was not severely affected by the Last Glacial Maximum. It is proposed that further investigations into the phylogeography of coastal marine species, particularly obligatory sessile species such as barnacles, are required to determine whether the patterns observed in T. serrata is a rare history, or not. Neighbour-joining, maximum parsimony and Bayesian analyses on the CO1 gene provide evidence for the monophyly of the genus Tetraclita; however, Tetraclita species found in South Africa do not share a common ancestry suggesting multiple colonization events. This study has also accidently led to the discovery of an introduced species, Balanus perforatus, native to Europe, and I discuss the potential of the alien becoming invasive on the east coast of South Africa where it was found. / AFRIKAANSE OPSOMMING: Suid-Afrika is bekend vir sy hoë mariene ongewerwelde diversiteit, maar die evolusionêre geskiedenis van hierdie spesies is grootliks onbekend. Hierdie studie is gedoen om by te dra tot die filografiese studies van suider Afrikaanse kus spesies en om die kolonisasie en diversifikasie van die Suid-Afrikaanse eendmossels beter te verstaan. Om die genetiese struktuur van die bevolkings van die vulkaan eendmossel, Tetraclita serrata, wat langs die Suid-Afrikaanse kuslyn voorkom, te bestudeer, was 410 individue van 20 lokaliteite ontleed. Daarbenewens, om die kolonisasie en diversifikasie van Suid-Afrikaanse eendmossels te verstaan, was nege spesies ingesluit in 'n molekulêre filogenie wat gebaseer is op die kern geen, 18s rRNA. Met slegs 'n beperkte aantal 18s DNS volgordes beskikbaar op GenBank,is 'n aparte filogenetiese boom, vir die mitochondriale geen COI, gekonstrueer om te bepaal of die genus Tetraclita monofileties is. Beperkte geen-vloei in sommige geografiese gebiede was verwag vir T. serrrata gebaseer op oseaniese sirkulasiepatrone; bekende biogeografiese streke, en kenmerke soos die Agulhas Bank, wat die filogeografiese struktuur van verskeie ander Suid- Afrikaanse mariene organismes beïnvloed het. Die genetiese struktuurvan die bevolkings is geondersoek met behulp van die mitochondriale sitochroom oksidase subeenheid 1 (COI) en kern interne getranskripeerde spasieërder 1 (ITS1) gene. Geen duidelike bevolkings genetiese struktuur is gevind nie en die rigting van geenvloei van T. serrata individue kan gekoppel word aan die oseanografiese kenmerke wat langs die Suid-Afrikaanse kus voorkom. Filogenetiese en bevolking genetiese ontleding van die COI geen openbaar twee afsonderlike klades maar met oorvleuelende geografiese verspruidings. Die ITS1 data-analise wat uitgevoer was op 'n subset van individue wys op 'n enkele spesie. Die waargenome patroon dui op 'n belangrike historiese verskil tussen die twee klades. 'n Geskiedkundige gebeurtenis was dalk verantwoordelik vir die vorming van twee evolusionêre lyne wat sederdien sekondêre kontak het. Aan die ander kant, kan die patroon waargeneem word as gevolg van die onvolledige sortering van nDNA allele, in welke geval, gegee dat die twee mtDNA clades nie geografies geïsoleer is nie, dit verduidelik kan word deur selektiewe druk wat op die spesie was as gevolg van fisiologiese of ekologiese beperkings. Die statistiese parsimonie netwerk, ongelyksoortige verspreidings en tyd sedert die bevolkingsuitbreiding dui daarop dat T. serrata die laaste ysagtige maksimum tydperk oortleef het. Tot op hede het geen Suid- Afrikaanse mariene spesies so 'n patroon gewys nie. So, verdere ondersoeke in die filogeografie van die kus mariene spesies, veral verpligte sittende spesies soos eendmossels, word vereis om te bepaal of die patroon waargeneem in T. serrata 'n seldsame geskiedenis het, of nie. Buur-aansluiting, maksimum parsimonie en Bayesian afleiding op die CO1 geen het bewyse verskaf vir die monofiletiese afkoms van die genus Tetraclita, maar Tetraclita spesies wat in Suid Afrika gevind is, deel nie ‘n gemeenskaplike afkoms nie, wat weer bewyse verskaf vir verskeie kolonisasie gebeure. Hierdie studie het gelei tot die ontdekking van 'n eksotiese spesie, Balanus perforatus, inheems aan Europa, en die potensiaal van die indringer om ontwykend te raak aan die ooskus van Suid-Afrika waar dit gevind is word bespreek. / The South African National Research Foundation (NRF) and Stellenbosch University

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In southern Africa, the ticks Amblyomma hebraeum and Hyalomma rufipes are the main vectors of animal Heartwater and human Crimean Congo Haemorragic Fever, respectively. In order to investigate the phylogeographic structure of these ectoparasites, population genetic studies were conducted throughout southern and partly eastern Africa. Knowing the levels of genetic diversities and population connectivities throughout the species’ native ranges, may be useful for implementing control measures (cross country borders for example), evaluate the potential for drug resistance in introduced locations as well as for elucidating its vectorial capacities in the region. Mitochondrial cytochrome oxidase I (COI) and the internal transcriber spacer 2 (ITS-2) sequences were obtained from eleven sampled localities. In general, haplotype networks and molecular diversity values showed significant genetic structure between most of the sampled populations. Fu’s Fs and mismatch distributions suggested recent population expansions following a bottleneck. A Mantel regression analysis also revealed a significant isolation by distance for H. rufipes. Comparing the two species, H. rufipes showed much stronger signals of geographic genetic population structure in relation to A. hebraeum. A single taxonomic unit is suggested for A. hebraeum while H. rufipes is characterized by the existence of at least three distinct genetic assemblages that may point to incipient speciation. The difference between the two species may be explained by gene flow restriction within the region, by the number of hosts required to complete the life cycle (2 and 3 hosts, respectively), type of host species (domestic and wild animals; small and big mammals, birds) and its availability, and host species overlap. Also, a geographic break between possible host species during the Pleistocene, domestication of animals and climatic conditions in the region played a role on the genetic structure of H. rufipes. / AFRIKAANSE OPSOMMING: Die suider Afrikaanse bosluise, Amblyomma hebraeum en Hyalomma rufipes is die hoof vektore van Hartwater in diere en Crimean Kongo Haemorargiese koors in mense. Om die filogeografiese struktuur van hierdie ektoparasiete te ondersoek, is bevolking-genetiese studies uitgevoer in suidelike Afrika asook gedeeltelik in oos Afrika. Deur die vlakke van genetiese diversiteit en bevolkingsverbindings regdeur die spesies se natuurlike verspreiding te weet, sal dit dalk moontlik wees om: beheermaatreëls (byvoorbeeld oorgrens) in te stel, die waarskynlikheid van weerstandbiedendheid in nuut losgelate gebiede te verstaan, en meer insigte in die vektoriale kapasiteit te verkry. Mitochondriale sitochroom oksidae (COI) en die interne transkriberende spasieerder 2 (ITS- 2) basisnukleotiedopeenvolgings van elf bevolkings is versamel. Haplotiepe netwerke en molekulêre diversiteitwaardes het in die algemeen, betekenisvolle genetiese verkille tussen meeste van die versamelde bevolkings aangetoon. Fu’s Fs en gemiste-paringverspreidings het voorgestel dat die bevolkings onlangs uitgebrei het nadat hulle 'n bottelnek ondergaan het. 'n Mantel regressie analise het ook betekenisvolle isolasie met afstand aangetoon vir H. rufipes. As die twee spesies vergelyk word het H. rufipes baie sterker seine van genetiese geografiese bevolkingstruktuur gewys as A. hebraeum. 'n Enkele taksonomiese eenheid word voorgestel vir A. hebraeum terwyl H. rufipes gekarakteriseer word deur ten minste drie taksonomiese eenhede. Die verskil tussen die twee spesies kan moontlik verklaar word deur geen-vloeibeperkings in die gebied, die aantal gasheer spesies wat benodig word om die lewenssiklus te voltooi (2 of 3 gashere onderskeidelik), tipe gasheer (domestikeerd- of wildlewend; klein of groot soogdiere, voëls) en hulle beskikbaarheid, en die gasheerspesies se oorvleueling. Dit is ook moontlik dat 'n geografiese breek tussen moontlike gasheerspesies gedurende die Pleistoseen, domestikering van diere en klimaatstoestande in die streek 'n rol kon speel by die genetiese struktuur van H. rufipes. / The NRF and the University of Stellenbosch for funding and bursary

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: To predict the influence of temperature increases on organisms, and their capacity to respond to climate change, information on the upper thermal tolerance of organisms and its plasticity is required. However, various factors, such as rate of temperature change, may influence basal thermal tolerance and plastic responses, and consequently the vulnerability of organisms to temperature change. Although slower rates of temperature change might be more ecologically relevant, the majority of thermal tolerance studies feature rates of temperature change that are faster than those experienced by organisms in nature. Additionally, studies using slower rates of temperature change have been criticized as factors such as changes in body condition and accumulation of stress over time may confound results. This study determined the influence of fast and slow rates of temperature change and plasticity, induced by acclimation to different temperature conditions for 5 – 15 days, on the upper thermal tolerance of marine amphipod and isopod species from sub-Antarctic Marion Island and South Africa. Using congeners, intra- and inter-specific comparisons of the upper thermal tolerance and plasticity of these organisms were made across geographical regions (South Africa vs. Marion Island), across sites within regions (West coast vs. South coast of South Africa) and between tidal zones. Overall, lower rates of temperature change were found to be associated with lower values of upper thermal tolerance. At fast rates of temperature change, acclimation at high temperatures was associated with an increase in thermal tolerance, whereas at slow rates, acclimation to higher temperatures either had no effect or caused a decrease in thermal tolerance. Furthermore, microclimate recordings suggest that these organisms likely experience rates of temperature increase that are intermediate between the fast and slow rates employed in this study. Thus, in nature these marine invertebrates have upper thermal tolerances that are higher than mean environmental temperature and can likely mount plastic responses during short-term temperature variation. At slow rates of temperature change, however, the upper thermal tolerance of these organisms approximates environmental temperature and plasticity is reduced, likely increasing vulnerability to high temperatures. At the intra-specific level, upper thermal tolerance and plasticity response varied based on mass and sex, however, these effects were species-specific. Isopods inhabiting cooler but more variable microsites on the West coast of South Africa had a higher upper thermal tolerance, but similar magnitude of plasticity, than a population of the same species from the warmer, less variable South coast. Generally, Marion Island species had a lower upper thermal tolerance but higher magnitude of plasticity than South African species. The variability reported here at different hierarchical and geographical scales could be linked to the distinct thermal environments experienced, and the differing physiological and behavioural responses of populations and species to their thermal environments. This variation in thermal tolerance might be critical during environmental change and suggests that species composition may be altered in the future. / AFRIKAANSE OPSOMMING: Om die invloed van temperatuur verhogings op organismes, en hul vermoë om te reageer op hierdie verandering, te voorspel, word inligting oor hoë temperatuur verdraagsaamheid van organismes en die plastisiteit hiervan, benodig. Verskeie faktore, soos die tempo van verandering, kan egter basale termiese verdraagsaamheid en plastiese reaksies beïnvloed. Dus, mag dit die tasbaarheid vir temperatuur verandering beïnvloed. Alhoewel stadiger tempo van verandering meer ekologies relevant kan wees, fokus die meerderheid van warm verdraagsaamheid studies op temperatuur veranderinge wat vinniger gebeur as wat ervaar word deur organismes in die natuur. Boonop word studies wat fokus op stadige veranderinge in temperatuur, gekritiseer omdat faktore soos ‘n verandering in liggaamstoestand en die opeenhoping van stres, potentieël die resultate kan belemmer. Hierdie studie ondersoek die invloed van vinnige en stadige temperatuur veranderinge en die plastisiteit, geïnduseer deur akklimasie, met betrekking tot verskeie temperature vir 5-15 dae. Ons fokus spesifiek op die hoë temperatuur verdraagsaamheid van mariene amphipod- en isopod spesies van sub-Antarktiese Marion Island en Suid Afrika. Deur gebruik te maak van spesies wat aan dieselfde genus behoort, is vergelykings getrek tussen intra- en inter-spesies verbande met betrekking tot hul termiese verdraagsaamheid en plastisiteit. Die studie is oor geografiese streke (Suid Afrika vs. Marion Island), tussen areas binne ‘n geografiese streek (Weskus vs. Suidkus van Suid Afrika) en tussen gety sones voltooi. Oor die algemeen was stadige temperatuur veranderinge geassosieër met ‘n laer termiese verdraagsaamheid vir hoë temperature. Met vinnige veranderinge in klimaat, was akklimasie by hoë temperature geassosieër met ‘n hoër temperatuur limiet, maar by stadige temperatuur veranderinge het akklimasie by hoë temperature geen effek gehad nie, of het ‘n afname in termiese verdraagsaamheid veroorsaak. Verder het mikroklimaat opnames aangedui dat hierdie organismes waarskynlik temperatuur verhogings ondervind in hul natuurlike habitat, wat intermediêre is van die vinnige en stadige veranderinge wat in hierdie studie gebruik is. Dus, in die natuur, het hierdie mariene invertebrate `n boonste termiese toleransies wat hoër is as die gemiddelde omgewingstemperatuur en kan hulle waarskynlik van platiese reaksies gebruik maak tydens kort-termyn temperatuur variasie. Gedurende stadige temperatuur veranderinge toon hulle alhoewel hoë termiese verdraagsaamheid teenoor die omgewingstemperature en plastisiteit is verminder, wat heel waarskynlik toenemende kwesbaarheid vir hoë temperature tot gevolg het. Op die intra-spesifieke vlak was wisseling in hoë termiese verdraagsaamheid gebaseer op liggaams massa en geslag, maar hierdie veskille was spesie-spesifiek. Isopoda wat koeler areas bewoon, met meer variasie in hul mikroklimaat, soos ondervind in die Weskus van Suid Afrika, het `n hoër termiese verdraagsaamheid. Maar, soortgelyke mate van plastisiteit, as 'n populasie van dieselfde spesie van die warmer, minder veranderlike Suidkus. Oor die algemeen het Marion-eiland spesies 'n laer termiese verdraagsaamheid, maar hoër grootte van plastisiteit as Suid-Afrikaanse spesies. Die veranderlikheid wat hier geraporteer is, kan op verskeie hiërargiese en geografiese vlakke gekoppel wees aan die unieke termiese omgewings wat hierdie organismes ervaar en aan die verskillende fisiologiese- en gedrags reaksies van populasies en spesies tot hulle termiese omgewings. Die variasie in termiese verdraagsaamheid kan krities wees tydens omgewingsverandering en dui daarop dat spesie-samestelling kan verander in die toekoms. / The British Antarctic Survey for funding

Thesis (MSc)--Stellenbosch University, 2010. / ENGLISH ABSTRACT: Opisthopatus cinctipes is a velvet worm endemic to South Africa and is widely distributed in isolated Afromontane and coastal forest patches throughout the Eastern Cape, KwaZulu-Natal and Mpumalanga. The species, like most velvet worms is characterized by low vagility, microhabitat specialization and is hypothesized to harbor significant cryptic diversity. We used partial sequence data derived from three partial mitochondrial (mtDNA) gene loci (COI, 12S rRNA and 16S rRNA) and a partial nuclear gene fragment (18S rRNA), as well as gross morphological character analysis and scanning electron microscopy (SEM) to determine evolutionary relationships amongst a total of 120 specimens of O. cinctipes from 33 localities. Phylogenetic relationships were investigated using Bayesian inferences, Maximum Parsimony and Maximum Likelihood analysis. Phylogenetic analysis of mtDNA and nDNA data revealed the presence of multiple cryptic lineages nested within Opisthopatus cinctipes with at least nine distinct well supported clades (> 70% / > 0.95 pP), suggesting that the taxon comprises a “species complex”. Afrotemperate forest specimens were genealogically highly distinct from each other whilst Indian Ocean Coastal Belt forest (at least in KwaZulu-Natal) specimens were more closely related and formed a well supported clade. An analyses of molecular variance indicated that (ΦST) 89.31% of the genetic variation occurred amongst localities. Highly significant FST values were generally observed across sampled localities (FST = 0.89, p < 0.001). Tajima’s D value was 0.83 over all sampled localities, implying a decrease in population size and/or balancing selection. Uncorrected pairwise sequence divergence values between O. cinctipes localities for the COI locus were high and ranged from 3.20% to 19.50%. No haplotypes were shared between localities. There is considerable evidence showing that past geological events may have shaped the deep genetic divergences observed between sampling localities suggesting the absence of gene flow. Genetic divergences within the South African O. cinctipes species complex are shown to have occurred from the onset of the Cenozoic era. The genetic variation observed within clades was not accompanied by morphological differences suggesting that the use of morphological characters has grossly underestimated species diversity within South African Opisthopatus. A robust taxonomic documentation of the species diversity within the O. cinctipes species complex is critical for the implementation of conservation management plans for this species complex. We recommend that highly sedentary taxa with limited dispersal abilities and specific habitat requirements which may be found in sympatry with velvet worms be prioritized for taxonomic revision as they may also harbor cryptic lineages. / AFRIKAANSE OPSOMMING: Geen Afrikaanse opsomming beskikbaar.

Thesis (MSc)-- University of Stellenbosch, 1954 / Published in the Annals of the University of Stellenbosch, Volume 31, Section A, No.1 (1955) / ENGLISH ABSTRACT: The pelvic girdles of the two anuran genera Ascaphus and Leiopelma of the family Ascaphidae are very similar. Attached to them by cartilage (or connective tissue in some Ascaphus specimens) is a cartilaginous, in Leiopelmu somewhat ossified, epibubis. In Ascaphu8, as in Xenopus, the epipubis originates from two Anlages, and its muscles are also paired in the Ascaphidae, while in Xenopus only one is present, although this also appears to originate (rom two muscles. The cloaca extends behind the pelvic girdle in both sexes in Al:lcaphus, and it is supported by two rods consisting of strong connective tissue (Faserknochen?). These rods are attached to the ventral surface of the pelvic girdle, in the female closely, in the male by means of tendons. Between the rods and the epipubis a broad tendinous band extends, which is thick in the male; in the latter the mm. compressores cloacae have their origins posteriorly on the rods, while in the female the rods are completely imbedded in these muscles posteriorly. In the female particularly there are transverse muscle fibres which are not striped although probably derived from the mm. compressorcs cloacae. Behind the pelvic girdle there is cavernous tissue in both layers of the tunica muscularis, and ventrally it covers the mm. eompressores cloacae. The circular and longitudinal muscle layers are poste riorly separated by gliding planes. The cloaca is supplied by branches of the a. mcsenterica posterior and the au. pudendae anteriores, and is drained by the vv. pudendae and a small medial v. eaudalis. The cloaca is innervated dorsally by the plexus ischio·coccygeus and ventrally by a branch of the n.ischiadicus (the n. pudendus). The cloaca of the male serves as a copulatory organ. There is internal fertilization. / No Afrikaans abstract available. / The copy we received from the author were pages individually scanned in as JPEG images.

Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Agricultural environments are usually contaminated with mixtures of antropogenically introduced chemicals as a result of pesticide spraying, which can affect beneficial, nontarget soil invertebrates, such as earthworms negatively. Most studies on mixture toxicity have focused on interactions of chemicals with similar structures and mechanisms. However, chemical mixtures may occur as conglomerates of diverse structures and toxicological mechanisms in the environment. This study was aimed at assessing the effects of pesticides singly, and in a mixture, on earthworms, using lifecycle parameters (growth and reproduction) and biomarkers (neutral red retention (NRR) assay and acetylcholinesterase (AChE) inhibition) as endpoints. Thus, to determine whether any interactions occurred between the pesticides as shown by the measured endpoints. Another aim was to validate the use of the chosen biomarkers for assessing mixture toxicity. The pesticides used were from three groups: organophosphates, heavy metal-containing pesticides and pyrethroids. From these three groups, four of the most commonly used pesticides in the orchards and vineyards of the Western Cape, South Africa, were chosen, namely chlorpyrifos (organophosphate), azinphos-methyl (organophosphate), copper oxychloride (heavy metal-containing fungicide) and cypermethrin (pyrethroid). Earthworms were exposed in the laboratory to a range of concentrations of chlorpyrifos and copper oxychloride singly, and in 1:1 mixtures of these pesticides in artificial soil, for four weeks. After the exposure period, the biomass change was determined as measure of growth, and cocoon production, hatching success and number of hatchlings per cocoon were determined as measures of reproduction. Growth (biomass change) and reproduction (cocoon production) were affected by the highest concentration treatment (20mg/kg) of chlorpyrifos, but copper oxychloride and the mixture of the two pesticides showed no observable effects on lifecycle parameters. Dose related effects on NRR times were however determined for both pesticides and the mixture. Dose related effects on AChE activity were found for chlopyrifos and the mixture of the two pesticides, but not for copper oxychloride. Short-term exposures (48 hours) of earthworms to the following pesticides in artificial groundwater: chlorpyrifos, copper oxychloride, azinphos-methyl, cypermethrin, chlorpyrifos-copper oxychloride, chlorpyrifos -azinphos-methyl and chlorpyrifos-cypermethrin, were done followed by the determination of AChE inhibition. Dose related effects were exhibited on the AChE activity of earthworms exposed to chlorpyrifos, a mixture of chlorpyrifos and copper oxychloride, azinphos-methyl, and a mixture of azinphos-methyl and chlorpyrifos. Copper oxychloride, cypermethrin and the mixture of chlorpyrifos and cypermethrin had no effect on AChE activity. Earthworms died at the highest exposure concentration of the mixture of chlopyrifos and cypermethrin. Results have shown that although the pesticides did not cause observable effects on lifecycle parameters, there were effects at subcellular and biochemical level, as shown by the biomarkers. Mixtures of pesticides, in some instances, affected earthworms differently from their single components, indicating interactions between the pesticides in mixtures, as shown by the measured endpoints. The NRR assay proved to be a good general biomarker of soil contamination, and the AChE activity could also be a valuable tool in assessing the effects of organophosphate mixtures and mixtures of organophosphates and pesticides from other groups. / AFRIKAANSE OPSOMMING: Nie-teiken organismes, soos erdwurms, word negatief beïnvloed deur mengsels van antropogeniese chemikalieë in landbou-omgewings. Die meeste studies wat handel oor die toksisiteit van chemiese mengsels het tot dusver gefokus op chemikalieë van dieselfde aard en met dieselfde meganismes van werking. Mengsels van chemiese stowwe kan egter as konglomerate van 'n verskeidenheid strukturele eienskappe en met verskillende toksiese meganismes in die omgewing aangetref word. Tydens die studie is gepoog om die effekte van enkel pestisiede sowel as mengsels daarvan op erdwurms te bestudeer, deur van lewensloop kenmerke (groei en voortplanting) en biomerkers (neutraalrooi retensietyd - NNR en inhibisie van asetielcholienesterase -AChE) as eindpunte gebruik te maak. 'n Verdere doel van die studie was om vas te stel of daar enige wisselwerkings tussen die verskillende pestisiede plaasvind, soos aangetoon deur die gemete eindpunte, en verder ook om die gebruik van die gekose biomerkers as maatstawwe van mengseltoksisiteit te evalueer. Die pestisiede wat gebruik is, is van drie verskillende groepe afkomstig: organofosfate, swaarmetale en piretroiede. Van hierdie drie groepe is vier van die pestisiede wat vry algemeen in boorde en wingerde in die Weskaap, Suid-Afrika, gebruik word, geïdentifiseer. Hierdie stowwe is chlorpyrifos (organofosfaat), azinphos-metiel (organofosfaat), koperoksichloried (swaarmetaalbevattende fungisied) en sipermetrien (piretroied). Erdwurms is in die laboratorium aan 'n reeks konsentrasies van chlorpyrifos en koperoksichloried as enkel toksikante en as 1:1 mengsels in kunsmatige grond, vir vier weke blootgestel. Voor en na die blootstellingsperiode is die biomassa van die wurms, as maatstaf van groei, bepaal en kokonproduksie, uitbroeisukses en getal nakomelinge per kokon bepaal as maatstawwe van voortplantingsvaardigheid. Groei (biomassaverandering) en voortplanting (kokonproduksie) is beinvloed deur behandeling met die hoogste konsentrasie (20 mg/kg) chlorpyrifos, terwyl geen effek van koperoksichloried of die mengsel van hierdie twee pestisiede gevind is nie. Daar is gevind dat beide die pestisiede, enkel en in die mengsel, die NRR tye beinvloed het. Die AChE aktiwiteit is beinvloed deur chlorpyrifos en die mengsel, maar nie deur die koperoksichloried nie. Korttermyn blootstellings van erdwurms (48 uur), in kunsmatige grondwater, van erdwurms aan chlorpyrifos, koperoksichloried, azinphos-metiel en sipermetrien as enkel toksikante en mengsels van chlorpyrifos-koperoksichloried, chlorpyrifos-azinphos-metiel en chlorpyrifos-sipermetrien, is gedoen en gevolg deur die bepaling van AChE inhibisie. Koperoksichloried, cypermetrien en die chlorpyrifos-sipermetrien mengsel het geen waarneembare effek op die AChE aktiwiteit gehad nie ?????. Die erdwurms wat blootgestel is aan die hoogste konsentrasie in die mengsel van chlorpyrifos-sipermetrien het doodgegaan. Die resultate het getoon dat die pestisiede nie in die korttermyn die lewensloopkenmerke in enige waarneembare mate geaffekteer het nie maar daar was effekte op sellulêre en biochemiese vlakke soos aangetoon deur die biomerkers. Sommige mengsels van die pestisiede het die erdwurms verskillend van die enkelstowwe geaffekteer. Daar het dus wisselwerking tussen sommige van die pestisiede wat in mengsels aangewend is, plaasgevind, soos aangetoon deur die gemete eindpunte. Die NRR toets, as breë-spektrum biomerker was 'n goeie maatstaf van kontaminasie in grond en daar is aanduidings dat die AChE aktiwiteit, as 'n spesifieke biomerker, 'n nuttige maatstaf kan wees om die effekte van organofosfaatmengsels en mengsels van hierdie chemiese groep en die van ander chemikalieë aan te toon.

Thesis (MSc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Landfarming is a widely used method for the disposal of contaminants in the petrochemical industry. It involves ploughing the contaminants into the top soil layer allowing biological breakdown. A historically landfarmed site was identified at a South African petrol refinery. The refinery used to dispose so-called American Petroleum Institute (API) -sludge onto a landfarming site. API-sludge consisted of a mixture of oil and water soluble contaminants originating from a process of separating refinery waste from reusable water and oil. Landfarming on this site was discontinued after excessive quantities of sludge were ploughed into the soil over time and it became obvious that effective biodegradation could not take place. An environmental assessment had to be carried out to assess to what extent the soil has recovered from the contamination and after remediation was done over time. Bioassays together with chemical analyses were executed to determine the level of pollutants in the soil and to assess the integrated effects of their bioavailable fractions. The landfarming site of the refinery was divided into two sections namely, a more contaminated north-site and less contaminated south-site. Soil samples were collected from both sites as well as from an off-site (control site). The soils were analysed physically, chemically and used in the bioassays. Two additional control soils were also used, OECD-soil and LUFA2.2 soil. Chemical analysis of the site soils showed the presence of heavy metals and high levels of diesel range organic hydrocarbons. The north-site had higher levels of contaminants compared to the south-site. Three species of soil organisms were used in standardised tests: Eisenia andrei, Enchytraeus doerjesi and Folsomia candida were exposed to the respective soils to study their survival, growth, reproduction success and avoidance behavior. Exposures to both site-soils were not acutely toxic to any organisms. F. candida had a decrease in juvenile production in both north- and south-site soils (289.42 ± 58.62 and 253.33 ± 122.94 respectively) compared to the control soil (479.89 ± 30.42). E. doerjesi showed an increase in produced juveniles exposed to north- and south-site soil (339.75 ± 76.92 and 414.00 ± 17.78 ) compared to control soil (57 ± 34.39). E. andrei had similar cocoon production when exposed to south-site soil than in off-site soil (19.00 ± 5.3 and 18.5 ± 9.7 respectively) but significantly less in north-site soil (1.25 ± 0.7). Only E. doerjesi showed avoidance of north-site soil. To determine the sensitivity of the organisms to the API-sludge, they were exposed to concentration series of API-sludge-spiked control soils. The effect concentrations were calculated as the concentration of API-sludge that will decrease the studied endpoints by 50% of the control soil (EC50). The EC50s varied for each species exposed in the different control soils showing that the toxicity of the API-sludge is to a certain extent dependent on the physical soil properties of the substrate. The reproduction of F. candida were most sensitive to the API-sludge in off-site soil (EC50 = 90 mg/kg) and the E. doerjesi the least sensitive in LUFA2.2 soil (EC50 = 36000 mg/kg). Five plant species were exposed to API-sludge-spiked potting soil and the germination success, early growth rate and biomass were studied. The plants were not as sensitive to API-sludge as the soil animals. Lettuce and grass were affected the most by API-sludge and beans were the most resilient species. With the addition of low levels API-sludge to the substrate, the growth rate of beans was stimulated. This study showed that the south-site has been successfully remediated and most soil organisms exposed to these soils were not affected by the levels of toxicants present. However, exposures to north-site soil still had negative effects on soil organisms. It is recommended that hydrocarbon contamination should be further remediated in the north-site soil before landfarming should be allowed to continue. / AFRIKAANSE OPSOMMING: Ploegverwerking is ‘n algemene remediëringsmetode vir die verwerking van afvalmateriaal in petrochemiese industrieë. Dit behels die inploeg van toksiese afvalmateriaal in die boonstegrondlaag sodat dit biologies afgebreek kan word. ‘n Voorbeeld van ‘n histories ploegverwerkte grondstuk is geidentifiseer by ‘n Suid-Afrikaanse olieraffinadery. Die raffinadery het in die verlede van die grondstuk gebruik gemaak om sogenaamde Amerikaanse Petroleum Instituut-slik (API-slik) daarin te ploeg. Die API-slik bestaan uit ‘n mengsel van olie- en wateroplosbare kontaminante afkomstig van die proses waardeur die raffinadery se afvalprodukte van hernubare water en olie geskei word. Nadat oormatige konsentrasies slik in die grond ingewerk is en bioremediasie nie meer doeltreffend kon voortgaan nie, is die ploegverwerking gestaak. ‘n Omgewingimpakstudie moes uitgevoer word om te bepaal tot watter mate die grond herstel het nadat remediasie oor tyd uitgevoer is. Toksisiteitstoetse en chemiese analises is uitgevoer om die vlakke van besoedeling sowel as die biobeskikbare fraksie daarvan in die grond te bepaal. Die ploegverwerkte area van die raffinadery is in twee verdeel naamlik, ‘n meer gekontamineerde noordelike area en ‘n minder gekontamineerde suidelike area. Grondmonsters is van die onderskeie areas asook van ‘n ongekontamineerde veld (as kontrole) naby die ploegverwerkte area versamel Die gronde is fisies- en chemies geanaliseer en toksisiteitstoetse is uitgevoer. Twee addisionele kontolegronde is ook tydens die blootstellings gebruik naamlik, OECD- en LUFA2.2-grond. Die chemiese analises van die ploegverwerkte toetsgronde het getoon dat daar steeds swaarmetale en hoë vlakke van dieselgekoppelde organiese koolwaterstowwe in die gronde teenwoordig is. Kontaminante was in hoër konsentrasies teenwoordig in die grond van die noordelike gebied as in dié van die suidelike gebied. Drie spesies van grondorganismes is gebruik tydens standaard toksisitetitstoetse. Eisenia andrei, Enchytraeus doerjesi en Folsomia candida is blootgestel aan die onderskeie toets- en kontrolegronde waarna hul oorlewing, groei, voortplantingsukses en vermydingsreaksies bestudeer is. Blootstellings aan die ploegverwerkte toetsgronde het geen akute toksisiteit vir enige van die spesies getoon nie. F. candida se juveniele produksie was laer in beide noordelike- en suidelike toetsgronde (289.42 ± 58.62 en 253.33 ± 122.94 onderskeidelik) as in die kontolegrond (479.89 ± 30.42). E. doerjesi blootstellings het ‘n toename in juveniele getalle getoon in die noordelike- en suidelike toetsgronde (339.75 ± 76.92 en 414.00 ± 17.78) in vergelyking met die ongekontamineerde kontolegrond (57 ± 34.39). Kokonproduksie by E. andrei was soorgelyk in die suidelike toetsgrond en ongekontamineerde kontrolegronde (19.00 ± 5.3 en 18.5 ± 9.7 onderskeidelik) maar beduidend minder as in noordelike toetsgrond (1.25 ± 0.7). Slegs E. doerjesi het ‘n beduidende vermydingsreaksie vir die noordelike toetsgronde getoon. Om die sensitiwiteit van die organismes aan vars API-slik te bestudeer, is hulle blootgestel aan konsentrasiereekse van API-slik in die onderskeie kontrolegronde. Die effektiewe konsentrasie (EK50) is bereken as die konsentrasie van API-slik wat die bestudeerde eindpunte met 50% sal verminder in vergelyking met die kontrolegrond Die EK50-waardes vir al die spesies het verskil na blootstelling aan die onderskeie kontrolegronde. Dus, die toksisiteit van die API-slik is tot ‘n sekere mate ook afhanklik van die fisiese grondeienskappe van die blootsellingssubstraat. Die voortplanting van F. candida was die gevoeligste eindpunt vir die blootstelling aan API-slik in kontolegrond (EK50 = 90 mg/kg) en E. doerjesi was die minste gevoelig in LUFA2.2 grond (EK50 = 36000 mg/kg). Vyf plantspesies is ook blootgestel aan API-slikgekontamineerde potgrond en die saadontkiemingssukses, vroeë groeikoers en biomassa is bestudeer. Alhoewel plante nie so sensitief was vir die API-slik soos die gronddiere nie, was blaarslaai en gras die meeste geaffekteer tydens die blootstellings. Boontjies was die ongevoeligste en met die toevoeging van lae konsentrasies API-slik (2.5% API-slik), is hul groeikoers selfs gestimuleer. Uit die studie was dit duidelik dat die suidelike deel van die grondstuk meer suksesvol as die noordelike geremidieer is en dat meeste grondorganismes wat daaraan bloot gestel is nie geaffekteer is deur die vlakke van kontaminasie wat steeds teenwoordig is in die grond nie. Die toetsgronde uit die noordelike deel het egter steeds negatiewe effekte op die grondorganismes gehad. Dit word voorgestel dat die koolwaterstof kontaminasie verder geremidieër behoort te word in die noordelike deel van die grondstuk voordat verdere ploegverwerking van die afval daar gedoen word.

Thesis (MSc (Botany and Zoology))--Unkiversity of Stellenbosch, 2009. / Phylogeographic genetic structure has been documented for a number of southern African terrestrial taxa. Information regarding geographic population genetic structuring in multiple taxa, with differing life histories, can provide insights into abiotic processes such as vicariance. A fragment of the cytochrome b mitochondrial DNA gene of a plains-dwelling species, Otomys unisulcatus, was sequenced and analysed. Two closely related geographic assemblages were found. The first assemblage (lowland group) contains populations from both the eastern and western parts of the species range, and the second comprises populations from the Little Karoo (central group). The lowland group was shown to be in a state of population expansion after a relatively recent mitochondrial DNA (mtDNA) coalescence, while the genetic signature of the central assemblage was characterized by more genetic diversity indicative of an older lineage/genetic refuge. Areas of higher elevation (namely mountain ranges) appeared to be the main factor limiting gene flow between these two groups. Aridification cycles due to glacial maximum periods probably resulted in increased dispersal leading to the widespread distribution of common haplotypes throughout the lowland group. Morphological variation in skull shape and size has been shown to follow environmental clines in some rodents. Geometric morphometric analyses on the ventral and dorsal views of the craniums of O. unisulcatus were utilised to test whether the population groupings obtained in the genetic analyses would be recovered by morphometric analyses. In addition, it was also investigated which of the environmental factors investigated influenced skull shape and size. The genetic groupings were not recovered for either the cranial shape or size. Size variation in the females correlated positively with annual rainfall, and so by proxy with habitat productivity, indicating that females which inhabited areas with lower rainfall would be larger. The significant relationship between females’ centroid sizes and rainfall was thought to be as a result of the increased nutrient requirement by this gender in the production of offspring. The males did not show a significant correlation between any of the environmental variables and centroid size. There was a significant difference between the skull shapes of the genders, further verifying the sexual dimorphism in the species. Three major clusters were found (according to cranium shape) using a Two-Block Partial Least Squares Analysis (2B-PLS), which relate to the biome boundaries within the species’ range. Variations in shape were attributed to the varying needs for strong masticatory muscles resulting from differing diets. The skull shapes of specimens occurring along the escarpment were intermediate between the first two clusters. Cranial shape in the male dorsal view dataset was significantly correlated with the environmental variables block, possibly due to the much lower minimum temperature in the Sutherland population (a population which was not included in the female analyses). It was concluded that differing diets of individuals in the respective biomes influenced the shape of the cranium of both genders. The sexual dimorphism in the cranium shapes may be as a result of the females digging tunnels (using their teeth) underneath the stick nests. Otomys unisulcatus show high levels of phenotypic plasticity throughout the range and it thus appears that the species can adapt fast to the different environmental variables.