Although a considerable amount of work has been done on the fauna of the soil of temperate forests and pastures, very little is known about that of tropical and sub-tropical soils. Most of the work on tropical soils concerns the fauna of tropical forests ... . The present investigation represents an attempt to discover the effect of an imported perennial tropical and sub-tropical plant, the Pineapple, on the soil fauna of a semi-arid region (rainfall 15-25 inches). Intro., p. 1-2

Certains symbiotes intracellulaires résident dans le cytoplasme des cellules et manipulent le système reproductif de leurs hôtes. Du fait de leur transmission maternelle, ces parasites sont sélectionnés pour optimiser la survie et la reproduction de leurs hôtes femelles. Chez les arthropodes, la bactérie Wolbachia infecte au moins 66% des espèces d’insectes mais peuvent aussi infecter des nématodes. Cette large distribution dans les populations hôtes confère à Wolbachia un potentiel important en tant que moteur d’évolution. En particulier, elle pourrait être utilisée comme vecteur transgène dans les espèces nuisibles. Mais la dynamique évolutive des infections à l’échelle des communautés est mal connue, en particulier la fréquence des transferts de parasites entre hôtes de différentes espèces et la stabilité évolutive des associations. Mon travail de thèse a porté sur la détection et dynamique des infections de Wolbachia à une échelle micro-évolutive, c’est-à-dire, dans des communautés d’arthropodes avec moins de 5 My. L’objectif de ce travail était à la fois la caractérisation des communautés géographiques d’arthropodes et celle des infections par Wolbachia de ces communautés. Nous avons également examiné l’existence de transferts horizontaux récents de ces symbiotes entre des taxa distantes ainsi que les routes écologiques potentielles pour ces transmissions / Sexual parasites are intracellular symbionts capable of manipulating the reproduction of their hosts. They are widespread in Arthropods where they display a wide range of reproductive manipulations; these can be potentially involved in the evolution of mating systems, speciation, gene acquisition and sex determination. In particular, Wolbachia is thought to infect more than 66% of insect species and is also found in nematodes. However, little is known about the dynamics of Wolbachia infections at the community level. Although at the intra-population level, invasion dynamics have been extensively studied, the same is not true at the community level where the turnover of infections remains largely uncharacterised. The question of how often are new infections acquired through horizontal transfers between distantly related hosts remains also open. Moreover, as Wolbachia is seen as a good candidate for a transgenic vector against pests, understanding its dynamic at the community level is crucial. We proposed to address them by performing an exhaustive characterisation of sexual parasites in simplified systems, using the opportunity offered by small arthropod communities in isolated islands

No description available.

In the Central Coast of California, USA, wine grape growers are making efforts to identify weed control practices that promote biodiversity in their vineyards while maintaining yields. A field study was conducted in Paso Robles, CA in 2006 and 2007 evaluating the effect on Zinfandel grape-vine growth and production, groundcover plant, and ground dwelling arthropod communities of five weed control practices: 1) flumioxazin, 2) simazine, 3) cultivation, 4) cover crop, and 5) untreated control. The herbicide treatments had the lowest weed biomass followed by the cultivation, being approximately 10 and 2 times lower than the weed biomass of either the cover crop or untreated control treatments respectively. However, the differences in grape yield were not as evident. In 2006, a rainy year, the herbicides and cultivation treatments did not differ in grape yield, but the cover crop and untreated control had a reduction of approximately 20% compared with the other treatments. In 2007, a dry year, in comparison to the herbicide treatments, the grape yield reductions of cultivation were around 22%, and of the cover crop and untreated control around 48%. Although the cover crop reduced grape yield, it suppressed weed species considered important such as horseweed, panicle willowherb, scarlet pimpernel, and sowthistle. The cover crop, cultivation and untreated control had 4 to 50 times higher plant density and more than 15 times higher plant diversity compared to the herbicide treatments. The arthropod abundance differed among treatments only in 2007 being higher in the cover crop and untreated control. Also, there was a positive relationship between plant and arthropod diversity (r2 = 0.42, P = 0.02 in 2006; r2 = 0.64, P < 0.001 in 2007). Laboratory seed predation tests of the two most frequently captured carabid beetles, Calathus ruficollis and Tanystoma maculicolle, indicated their preferences for Brassica nigra and Capsella bursa-pastoris, which are considered common weed species in the region. Under field conditions, treatments with higher plant diversity and biomass favoured arthropod seed predation of these weeds, which was 20-40% in the cover crop and untreated control, doubling the predation observed in the herbicide treatments. The cultivation treatment balanced the benefits of promoting diversity while minimizing yield reductions due to weed competition. Our data indicated that the critical period of weed competition for Zinfandel grape vines occurred during budbreak-bloom period. Also, it was concluded that vines can tolerate a certain amount of weed competition, and that properly timing one pass post-emergence control tactics (e.g. cultivation or POST herbicides) could provide the necessary level of control to obtain the desired yields. However, under limited soil moisture conditions, the use of PRE herbicides could prove important to maintain vine yield and vigor. The results also illustrate how weed management practices that promote higher plant diversity and density have the potential to yield ecological services within vineyards by favoring the diversity and activity of other organisms.

No description available.

Thesis (PhD (Conservation Ecology and Entomology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Invasive alien trees (IATs) and agriculture are rapidly altering the capacity of ecosystems to provide a variety of essential services, with decreasing habitat quality having an adverse effect on arthropod biodiversity. Although both agricultural intensification and IATs have an impact on ecosystems, it is unclear which of these two is currently the most severe. Here I compare the influences of vineyards and IATs on arthropod diversity in the Cape Floristic Region (CFR) from two perspectives. Firstly, insect diversity from four different vegetation types (native fynbos, IATs, cleared invasive alien trees (CIATs) and vineyards), and their ecotones were assessed. Secondly, soil compaction in the different vegetation types was assessed and compared to determine how soil compaction relates to arthropod species richness and abundance. Surface-active arthropods were used for these evaluations, as they were considered to be the most abundant, yet sensitive groups for these comparative assessments. Pitfall trapping, which has been widely used for such comparative studies, was the method of choice. Additionally, as a result of incidental wildfires at some of the study sites (IATs and fynbos vegetation), it was decided opportunistically to assess recovery of arthropod diversity following the impact of fire. The results categorically indicate that IATs had by far the most significant impact, in comparison with vineyards, in reducing arthropod diversity and changing assemblage composition. Both IATs and vineyards, not surprisingly, supported lower arthropod diversity compared to fynbos, while CIATs supported arthropod species richness comparable to that of fynbos. However, different invertebrate species responded differently to IAT invasion, with some species even adapted to conditions in IAT patches. Environmental factors such as leaf litter and soil compaction were strongly correlated with arthropod species richness. However, other factors, such as soil moisture content, were not correlated with species richness, despite varying significantly between different vegetation types. IATs were found to reduce soil compaction, while vineyards increased soil compaction. The ecotone between adjacent land-use types was important for sustaining high arthropod species richness, particularly for the CIATs/fynbos ecotone, followed by the interface between CIATs/vineyard and vineyard/fynbos. Some species even preferred ecotones. Surface-active invertebrate species richness declined substantially immediately after fire in both IATs and fynbos. Nevertheless, recovery was rapid, with some species recolonizing or re-establishing within three months. Indeed, both species richness and abundance were high following fire. Fire had no significant impact on arthropod assemblage within IATs, despite having a serious impact in the fynbos where a different arthropod assemblage was observed after fire. The recovery of the historic assemblages may be dependent on both the pre-fire composition of the habitat and its adjacent vegetation. Effective co-operation among conservation biologists, farmers, and landowners to actively plan the future of CFR landscape biodiversity is required. / AFRIKAANSE OPSOMMING: Indringer uitheemse bome (IUB) en landbou bedrywighede is vinnig besig om die kapasiteit van ekosisteme vir die voorsiening van „n verskeidenheid van noodsaaklike dienste, met „n afname in habitatkwaliteit en „n nadelige uitwerking op artropood biodiversiteit, te verander. Alhoewel beide, landbou intensifikasie en IUB‟s, ‟n impak op ekosisteme uitoefen, is dit onduidelik watter van hierdie twee huidig die mees ernstige een is. In hierdie studie vergelyk ek die invloed van wingerde en IUB‟s op artropood diversiteit in die Kaapse Floristiese Streek (KFS) vanuit twee perspektiewe. Eerstens, insekdiversiteit van vier verskillende vegetasietipes (natuurlike fynbos, IUB‟s, verwyderde indringer uitheemse bome (VIUB‟s) en wingerde) en hulle ekotone is bepaal. Tweedens, is grondverdigting in en van die verskillende vegetasietipes ondersoek en vergelyk om te bepaal hoe grondverdigting verband hou met artropood spesies rykheid en volopheid. Oppervlak-aktiewe artropode is vir hierdie bepalings gebruik aangesien hulle beskou word as die mees volopste, maar ook mees sensitiewe groepe vir hierdie vergelykende bepalings. Pitvalvangste, wat alom gebruik word vir sulke vergelykende studies, was die verkose werkswyse. Bykomend, as gevolg van onbeplande veldbrande in sommige studie gebiede (IUB‟s en fynbos plantegroei), is oppertunisties van die geleentheid gebruik gemaak om die herstel van artropood diversiteit na die impak van brand te bepaal. Die resultate toon duidelik aan dat IUB‟s, in vergelyking met wingerde, by verre die mees beduidende impak gehad het deur ‟n verlaging van artropood diversiteit en veranderende groeperingssamestellings. Beide, IUB‟s en wingerde, het, nie onverwags nie, in vergelyking met fynbos, laer artropood diversiteit ondersteun, terwyl VIUB‟s artropood spesies verskeidenheid, vergelykbaar met dié van fynbos, ondersteun het. Verskillende invertebrate spesies het egter verskillend gereageer op IUB indringing, en sommige spesies het selfs by toestande in IUB kolle aangepas. Omgewingsfaktore soos blaarafval en grondverdigting was sterk gekorrelleer met artropood spesies rykheid. Ander faktore, soos grondvoginhoud, was egter nie in ooreenstemming met spesies rykheid nie, ten spyte van ‟n beduidende wisseling tussen verskillende vegetasietipes. IUB‟s het grondverdigting verminder, terwyl by wingerde grondverdigting toegeneem het. Die ekotone tussen aanliggende grondgebruike was belangrik om hoë artropood spesies rykheid, veral by die VIUB‟s/fynbos ekotoon, gevolg deur die kontaksones tussen VIUB‟s/wingerd en wingerd/fynbos, te onderhou. Sommige spesies het selfs ekotone verkies. Oppervlak-aktiewe invertebraat spesies rykheid het onmiddelik na brand in beide, IUB‟s en fynbos, wesenlik afgeneem. Tog was herstel vinnig, met sekere spesies wat binne drie maande teruggekeer of hulle hervestig het. Inderdaad was beide, spesies rykheid en volopheid, hoog na ‟n brand. Brand het geen noemenswaardige invloed op artropood groeperings binne IUB‟s gehad nie, ten spyte van ‟n ernstige impak in fynbos waar ‟n verskillende artropood groepering na ‟n brand waargeneem is. Die herstel van die historiese groeperings van beide, die voor-brand samestelling van die habitat en sy aangrensende plantegroei, mag afhanklik wees. Effektiewe en aktiewe samewerking tussen bewaringsbioloë, boere, en grondeienaars om die toekoms van KFS landskap biodiversiteit te beplan, word benodig.

Thesis (PhD (Botany and Zology))--University of Stellenbosch, 2006. / The well-known, and often phytopathogenic, ophiostomatoid fungi are represented in South Africa by the two phylogenetically distantly related genera Ophiostoma (Ophiostomatales) and Gondwanamyces (Microascales). They are commonly associated with the fruiting structures (infructescences) of serotinous members of the African endemic plant genus Protea. The species O. splendens, O. africanum, O. protearum, G. proteae and G. capensis have been collected from various Protea spp. in South Africa where, like other ophiostomatoid fungi, they are thought to be transported by arthropod vectors. The present study set out to identify the vector organisms of Protea-associated members of mainly Ophiostoma species, using both molecular and direct isolation methods. A polymerase chain reaction (PCR) and taxon specific primers for the two Protea-associated ophiostomatoid genera were developed. Implementation of these newly developed methods revealed the presence of Ophiostoma and Gondwanamyces DNA on three insect species. They included a beetle (Genuchus hottentottus), a bug (Oxycarenus maculates) and a psocopteran species. It was, however, curious that the frequency of these insects that tested positive for ophiostomatoid DNA was very low, despite the fact that ophiostomatoid fungi are known to colonise more than 50% of Protea infructescences. Subsequent direct isolation methods revealed the presence of reproductive propagules of Ophiostoma spp. on four Protea-associated mite species (Oodinychus sp., two Tarsonemus spp. and Proctolaelaps vandenbergi). These mites are numerous within Protea infructescences and Ophiostoma spp. were isolated from a high frequency of these individuals. The Oodinychus sp. mite was found to vector most of the Protea-associated Ophiostoma species. It was thus postulated that the mites (in particular the Oodinychus sp.) act as primary vectors of the Protea-associated Ophiostoma species. The association between Oodinychus mites collected from P. repens and O. splendens proved to be mutualistic. Mites feeding on this fungus showed significantly higher population growth than mites feeding on any of the other fungal species tested. The short- and long-distance dispersal methods of these mites were also investigated. Firstly the ability of mites to move from drying infructescences to moist and sheltered areas such as provided by intact infructescences on the same plant was investigated experimentally. Significantly more mites were found to actively disperse from drying infructescences to artificially manufactured infructescences containing moistened filter paper shreds than to artificially manufactured infructescences containing dry filter paper shreds. The frequent fires associated with the habitat of these mites would, however, require movement over larger areas than what would be possible through self-dispersal. Dispersal of mites via air currents was thus investigated using sticky traps, but no Ophiostoma-vectoring mites were captured in this way. Self-dispersal aided by air currents could thus be ruled out, and our investigations shifted to vectored dispersal. Numerous insects emerging from Ophiostoma-containing P. repens and P. neriifolia infructescences were collected using specially designed emergence cages. Scanning electron microscopy and stereo-microscopy revealed that all three Ophiostoma-vectoring mite genera were phoretic on the beetle G. hottentottus. Tarsonemus spp. and P. vandenbergi were also phoretic on the beetles Trichostetha fascicularis and T. capensis associated with P. repens and P. neriifolia flowers. Mites collected from the surface of these beetles were found to vector reproductive propagules of various Ophiostoma spp. This thus seems to be the only method of long-distance dispersal of these mites and subsequently also the Protea-associated Ophiostoma species. Molecular phylogenetic reconstruction based on large subunit, ITS and beta-tubulin DNA sequence data suggests a polyphyletic origin for the Protea-associated members of Ophiostoma, which proposes multiple invasions of this unusual niche by these fungi. These studies also revealed the presence of four new species of Ophiostoma associated with Protea spp. The new species O. palmiculminatum, O. phasma, O. gemellus and Sporothrix variecibatus were thus described. Ophiostoma palmiculminatum is associated with P. repens infructescences and the Oodinychus mites collected from them. Ophiostoma phasma was collected from various Protea and mite species. Ophiostoma gemellus and Sporothrix variecibatus were initially only isolated from mites, but have subsequently also been isolated from Protea spp. The present study clarifies many aspects pertaining to the phylogeny and ecology of the interesting members of Ophiostoma associated with Protea hosts. As such this study will form the platform for further studies on the co-evolution of these insect / mite / fungi / plant associations.

Introduction This thesis concerns the mosquito-borne arbovirus Ross River (RR) virus. The main objectives were to determine the vector associations, the incidence, costs and natural history of disease, and behavioural and environmental risks for infection in tropical Queensland. 1. Literature review On the basis of the literature review there is strong evidence that Aedes vigilax, Ae. camptorhynchus and Culex annulirostris are important vectors in Australia. Aedes camptorhychus does not occur in Queensland. There is evidence that two peri-domestic container-breeding mosquitoes, Ae. notoscriptus and Ae. aegypti, may be vectors of the virus. The virus has been isolated from many other species but the role of most of these is unclear. It is unclear which vertebrate species are the major reservoirs for human infection. Studies are inconsistent with regard to the prevalence, duration and severity of symptoms and debility during RR virus disease. Nearly all epidemiological studies of RR virus have been descriptive. Therefore one can only surmise what the risks for human infection might be. Epidemiological studies to determine the associations between exposures and risk for disease do not exist. 2. Virus isolation from mosquitoes During 1996-1998 61,619 mosquitoes were processed for virus isolation. Thirty-three isolates of RR virus were made. The largest number (14) were from Ae. carmenti. The minimum infection rate (MIR) per 1,000 was 2.4. Isolates were also made from Ae. imprimens (1 isolate, MIR 10.3), Ae. kochi (2, 0.2), Ae. lineatus (1, 0.2), Ae. notoscriptus (1, 1.6), Ae. vigilax (1, 0.3), Cx. annulirostris (9, 0.3), Cx. vicinus (1, 4.0) and Mansonia septempunctata (3, 5.8). Ross River virus has been isolated from Cx. annulirostris, Ae. vigilax, Ae. notoscriputus and Ae. kochi but not from the other species. Ross River virus was not isolated from Ae. aegypti. Twenty-six isolates came from in or near a colony of 15,000 spectacled flying-fox, Pteropus conspicillatus. The proportion of RR virus positive pools from within 1 km. of this colony was significantly greater than elsewhere for all species combined and for Cx. annulirostris but not for Ae. carmenti. 3. The incidence and costs of Ross River virus disease Unpublished data on National, State and Territory notifications was collected. Crude incidence rates using census figures for denominator data were calculated. The same was done for the areas in which the other studies described in the thesis were carried out. An estimate of the cost of Ross River virus disease in Australia was made. During the period 1991-1998 of the States and Territories the Northern Territory (NT) had the highest and the Australian Capital Territory (ACT) the lowest notification incidences. These were 62-281 and 0-3 per 100,000 per annum, respectively. During this period the notification incidence for Queensland ranged from 70 to 149 per 100,000 per annum. For the local government areas of Cairns and Mareeba, where the majority of cases of RR virus disease for the studies described in this thesis were recruited, the notification incidences were between 74 and 267, and 28 and 200, respectively. On the basis of an average of 4,800 cases per annum in Australia the cost of serological testing and medical consultations were estimated at $443,520 and $105,600. Lost earnings were estimated at $1,798,560. The total cost for medical consultations, serological testing and lost earnings will therefore be over $2 million in an average year. 4. The natural history of Ross River virus disease In 1998 incident cases of RR virus disease were ascertained. Fifty-seven eligible cases were recruited but only 47 could be reviewed on 3 occasions and data on these were analysed. Cases were followed for up to 197 days. Review included history, examination and the administration of the Clinical Health Assessment Questionnaire (CLINHAQ) and Short Form-36 (SF-36) . On initial review the 3 most common symptoms were arthralgia, joint stiffness and myalgia affecting 97.9, 89.4 and 59.6% of cases, respectively. The joint types most commonly affected by pain at the initial review were the ankles, wrists, interphalangeal joints of the fingers, knees and metacarpophalangeal joints. Objective signs of joint inflammation were rare. The prevalence of signs of inflammation decreased and the prevalence of normal joints on examination increased through the reviews. The prevalence of use of NSAIDs decreased through the reviews. On the basis of CLINHAQ items regarding work performance functioning at work improved through the course of the reviews. Linear regression with days since symptom onset as the independent variable was performed for some variables. The 8 dimensions of the SF-36 were standardized to the Queensland population and analyzed longitudinally . Analyses of the CLINHAQ functional disability index (FDI) and the visual analogue scales (VASs) for pain, global severity, fatigue, gastrointestinal complaints and sleep, and the depression and anxiety scales were also performed. The slopes of all fitted regressions except the SF-36 general health dimension were significantly different from zero. All measures of disease severity returned to normal by 8 months from onset, many in a shorter period. 5. Behavioural and environmental risks for infection Fifty-five incident cases of RR virus disease were recruited and formed the basis of a case-control study of behavioural and environmental risks. They were matched to 85 controls. In the year prior to symptom onset the only leisure exposure that significantly altered risk was camping [Odds ratio (OR) = 2.15; 95% confidence interval (CI) = 1.07-4.35]. No peri-domestic activities in the year prior to onset significantly altered disease risk. Leisure exposures were also assessed in a 3-week exposure period ending 4 days prior to symptom onset. None significantly altered risk. No peri-domestic activity in this period significantly altered risk and nor did exposure to vertebrates or mosquitoes. Containers and vegetation around the subject's dwelling did not significantly increase risk. The presence of ice cream containers and buckets was significantly protective when assessed by questionnaire, however this was also assessed by inspection and was found to increase risk though not significantly so. It was concluded that the former finding was due to differential misclassification of exposure status. The premise condition index (PCI) was measured. A low PCI for the subject's house was associated with a significantly increased risk (3-4 relative to 7-9 as reference category: OR = 3.15, 95% CI = 1.07-9.25). Window screening did not alter disease risk and air-conditioning in the house or the bedroom decreased risk but not significantly so. Use of protective measures, except bed nets, in the year prior to onset was found to decrease disease risk. Personal repellents, mosquito coils and citronella candles significantly decreased risk. A dose response was shown for the number of protective measures from personal repellents, aerosol and surface sprays, mosquito coils, citronella candles and mosquito "zappers" used in the year prior to symptom onset. Pet ownership and proximity of dwelling to horses did not significantly alter risk. A preference for light coloured clothing was significantly protective (0.37, 0.15-0.89). Stratification by gender, date of symptom onset and geographical area was performed. Stratification by geographical area included a coastal and tablelands stratum. There were differences between the stratum-specific odds ratios for camping in the year prior to symptom onset, the presence of bromeliads in the subject's garden and a preference for light coloured clothing. Multivariate analysis demonstrated confounding by use of personal repellents, mosquito coils and citronella candles. When modeled together these were found to cause confounding among themselves. They also caused significant confounding of camping, outdoor work and the presence of banana trees in the subject's yard. Multivariate analysis of the association between PCI and disease risk failed to demonstrate confounding by use of protective measures or time between symptom onset and review. 6. Synthesis and conclusions The three research Chapters form a coherent body of public health research on the epidemiology (Chapters 5 and 6) and ecology (Chapters 4 and 7) of RR virus, and the natural history of RR virus disease (Chapter 6) in tropical Queensland. Conclusions are drawn from the research in the thesis. A set of priorities for future public health research on RR virus is suggested, and a pilot control program for Ross River virus disease in tropical Queensland is recommended.

Made available in DSpace on 2015-03-26T13:30:51Z (GMT). No. of bitstreams: 1 texto completo.pdf: 408527 bytes, checksum: 3f5ff39d24998982838ce196768d85c4 (MD5) Previous issue date: 2011-02-18 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Predators capture, kíll and consume theír prey. Thís ís the only ap- proach consídered ín rnost studíes Of predator-prey ínteractíons. However, sorne recent studíes have been concerned Wíth the índírect effects Of pre- datíorL When threatened, prey can change theír behavíor, thus reducing theír chances Of death. Frorn thís perspectíve, experíments performed wíth rnosquítoes specíes ín aquatíc envíronments shows that, ín several ínstances, preys are able to ídentífy the presence Of predators. Thís perceptíon leads to behavíoral alteratíons such as fernale ovíposítíon repellency and reduced foragíng 1arvae. However, the type Of sígnal perceíved by the prey, the írn- portance Of índuced responses to the survíval Of índívíduals, and the reasons for these evolve ín sorne species and not others, remain under díscussíon. The objectíve Was to deterrníne Whether chemícal cues of predator larva Toxorhyn- chites theobaldi (Díptera: Culícídae) are capable Of ínñuencíng the behavíor Of fernales and ímmatures ín three prey species Of the sarne farníly, although wíth Very dístínct behavíor (Culea: molli8, Limatus durhamii and Aedes al- bopictu5). We found that, the ínfusíon Where T. theobaldi larvae Was shel- tered, probably releasíng chernícal sígnals, had a lower proportíon of larvae (5.4 %) of C. molli5, cornpared Wíth control (95.6 %), índícatíng ovíposítíon repellency. Meanwhíle, the other two specíes ovíposíted índíscrímínately on ínfusíon treated and controL We also observed that the presence of traces of the sarne predator, C. mollis larvae spend rnost of theír tíme ín rest (82.7 compared Wíth no sígns of T. theobaldi (49.3 %). However. L. durhamii and A. albopictus larvae do not show behavíoral changes ín the presence of the sarne sígnals. Yet, C. mollis larvae ís preyed upon ín a smaller proportíon than the others, suggestíng that these changes ínñuence ín species Vulnera- bílíty. Frorn these results, ít ís argued that the líkelíhood of the development of defensive responses índuced by predatíon rísk ís related to several factors such as hístoríc of contact Wíth the predator, the ovíposítíon strategy of the females and the ñxed and ñexíble behavíor standard and posítíoníng of 1ar- Vae. Also ís díscussed the ímportance of natíve predators to curb the ínvasíon of exotíc species and díseases spread by these Vectors. / Predadores capturam, abatem e consomem suas presas. Esta é a única abordagem considerada na maior parte dos estudos da ínteração predador- presa. Entretanto, alguns trabalhos recentes têrn se preocupado com os efeitos indiretos da predação. Quando ameaçadas, presas podem alterar seu comportamento, reduzindo suas chances de morte. Sob essa perspectiva, experimentos realizados com espécies de mosquitos em ambientes aquáticos demonstram que, em diversas situações, presas são capazes de identificar a presença de predadores. Tal percepção induz alterações comportamentais como a repelência de ovíposição das fêmeas e redução no forrageamento das 1arvas. Entretanto, o tipo de sinal percebído pelas presas, a importância das respostas induzidas para a sobrevivência dos indivíduos, e as razões destas evoluírem ern algumas espécies, e não em outras, permanecem em discussão. O objectivo do trabalho foi verificar se pistas químicas da presença larva predadora Toxorhynchites theobaldi (Díptera: Culícídae) influenciam o comportamento tanto de fêmeas ovípositantes quanto de imaturos de três espécies de presas da mesma famílía, entretanto com comportamentos bastante distintos, sendo elas Culex molli5, Limatus durhamii e Aedes albopictus (Díptera: Culícídae). Verificamos que, na infusão onde larvas de T. theobaldi permaneceram abrigadas previamente, liberando possíveis sinais químicos, foi encontrada uma menor proporção de larvas (5,4%) de C. molli5, quando comparado com o controle (95,6%) , indicando repelência na ovíposição Enquanto isso, as outras duas espécies ovíposítaram indiscriminadamente na infusão tratada e na controle. Observamos tarnbérn que, na presença de indícios desse mesmo predador, imaturos de C. mollis passaram maior parte do tempo ern repouso (82,7%), quando compadrado com a ausência de sinais de T. theobaldi (49,3%). Entretanto, ímaturos de L. durhamii e A. albopic- tus não apresentam alterações comportamentais na presença dos mesmos sinais. Ainda, C. mollis é predado em uma menor proporção que as demais, sugerindo que essas alterações influenciam na Vulnerabilidade das espécies. A partir desses resultados, é discutido que a probabilidade da evolução de respostas defensivas induzidas pelo risco de predação está relacionada a diversos fatores como o histórico de contato com o predador, a estratégia de ovíposição das fêmeas e o padrão fixo e flexicível de comportamento e posícionarnento das 1arvas. É abordada também a importância dos predadores nativos em conter a invasão de espécies exóticas e a disseminação de doenças por elas Veiculadas.

A major goal of evolutionary developmental biology is to explore mechanisms and events underlying evolution of the myriad body plan morphologies expressed both genetically and phenotypically within the animal kingdom. Arthropods exhibit an astounding array of morphological diversity both within and between representative sub-phyla, thus providing an ideal phylum through which to address questions of body plan innovation and diversification. Major arthropod groups are recognised and defined by the distinct form and number of articulated appendages present along the antero-posterior axis of their segmented bodies. A great deal is known about the developmental genetics of limb development in the model insect Drosophila melanogaster, added to which, much comparative gene expression data and a growing body of functional genetic data is emerging for other arthropod species. Arthropod limb primordia are consistently marked by expression of the homeobox gene Distal-less (Dll), and the focus of this thesis is to compare signalling mediated by early Dll regulatory genes activity along antero-posterior and dorso-ventral embryonic axes during limb specification in Drosophila, with the activity of their orthologs in the widely disparate chelicerate, the spider mite Tetranychus urticae - interpreting new data with that available for other arthropods. Having made a detailed study of spider mite embryonic (and post-embryonic) development, to provide a basis for understanding mRNA transcription and protein activity patterns, I confirmed typical expression of Tetranychus Dll in prosomal limb primordia. I obtained limited results for the candidate antero-posterior positioning genes wingless and engrailed, although one of the two engrailed paralogs I identified is reportedly expressed in posterior segmental compartments, consistent with possible conservation of Engrailed-Wingless interactions in metameric patterning and positive regulation of Dll in arthropod limb specification. In Drosophila, wingless-dependent Dll transcription is restricted along the dorso-ventral axis by dorsal Dpp-mediated and ventral EGFR-mediated signalling gradients. Based on data from Tetranychus and other arthropods, neither dorsal nor ventral signalling regimes appear conserved outside the Drosophila system. Dll suppression in fly abdominal segments occurs due to powerful Hox (Ubx/AbdA) repression of the early Dll cis-regulatory element; this is discussed in relation to the independently evolved limbless chelicerate opisthosoma, informed by hypothetical scenarios of cis (regulatory DNA) and trans (coding sequence) evolution. Given practical difficulties and limitations encountered while working with spider mites, I offer a final assessment of the place of Tetranychus urticae as a non-model, and yet still valuable chelicerate species to consider carrying into the exciting future of evolutionary developmental biology.