Orientador: Tânia Marcia Costa / Resumo: Organismos do entremarés são frequentemente expostos a temperaturas extremas e as alterações climáticas podem trazer consequências negativas para estes organismos. Neste trabalho, avaliamos os efeitos do aumento da temperatura e redução do pH nas respostas fisiológicas e comportamentais de caranguejos chama-maré. Leptuca uruguayensis e Leptuca leptodactyla ocorrem tipicamente em habitat vegetado e não-vegetado de regiões estuarinas, apesar de coabitarem diversas áreas dos ecossistemas do entremarés. Realizamos experimentos para obtenção das respostas fisiológicas e comportamentais de ambas espécies ao aumento da temperatura. Minuca mordax foi exposta ao aquecimento e redução do pH da água para avaliação das respostas fisiológicas. Também estimamos a futura distribuição de M. mordax em cenários de mudanças climáticas. As duas espécies de Leptuca apresentaram diferenças nas adaptações fisiológicas (em relação ao consumo de oxigênio) e nos mecanismos de termorregulação, em consonância com a seleção de habitat e distribuição geográfica de cada espécie. Leptuca uruguayensis selecionou micro-habitat com temperatura inferior enquanto L. leptodactyla estava em um substrato com maior temperatura, mas apresentou características conhecidas por promoverem a dissipação de calor e reduzirem a taxa de desidratação, como tamanho e quelípodo maiores e coloração clara. As atividades comportamentais na superfície também foram afetadas pela elevação da temperatura, aumentando o tempo dentro da t... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Intertidal organisms are often exposed to extremes temperatures and may be harmed by climate change. The present study aimed to evaluate the effects of warming and pH decrease on physiology and behavior of fiddler crabs. Leptuca uruguayensis and Leptuca leptodactyla inhabit vegetated and unvegetated habitats from estuarine regions, respectively, despite cohabit some areas in intertidal ecosystems. Both species were exposed to warm to analyze the physiological and behavioral effects. Minuca mordax was exposed to warm and lower pH water. Also, we estimated the future distribution of M. mordax in climate change scenarios. Both species showed different adaptation (regarding oxygen consumption) and thermoregulatory mechanism, which reflect their habitat selection and range distribution. Leptuca uruguayensis selected less heated micro-habitat while L. leptodactyla was in a warmer substrate beside possessed larger size and major claw and whiten display that enhanced dissipation of heat and lowered desiccation rate. Higher temperature constraint surface activities, increasing refuge use and decreasing feeding, which might have impacted some physiological response (ammonia excretion and hepatosomatic index). Waving display was not affected by temperature, suggesting influence by other factors such as female and competitor presence. Warming and reduced pH altered physiological response (oxygen consumption, ammonia excretion, hepatosomatic index, and osmoregulation) of M. mordax, effect... (Complete abstract click electronic access below) / Doutor

A cause d’une anthropisation toujours plus forte des écosystèmes, de plus en plus de menaces pèsent sur la biodiversité. Parmi celles-ci, l’exposition aux contaminants est particulièrement problématique pour les organismes vivants. Emis et utilisés dans les pays industrialisés, ces contaminants hautement persistants dans l’environnement vont gagner les régions polaires puis se bio-accumuler dans les organismes vivants au cours du temps et se bio-amplifier le long du réseau trophique. Ainsi, les oiseaux marins, longévifs et situés dans les maillons supérieurs de la chaine alimentaire, sont particulièrement exposés et vulnérables à une exposition chronique à ces contaminants. A travers une perturbation endocrinienne, ces contaminants vont pouvoir impacter certains mécanismes physiologiques et traits comportementaux, entrainant in fine des conséquences à long-terme sur la fitness des individus et populations. Ma thèse s’articule autour de trois grandes familles de contaminants : i) les composés perfluoroalkylés (PFASs), encore largement utilisés dans plusieurs secteurs industriels et agricoles et en augmentation dans l’environnement ; (ii) les composés organochlorés dits « d’héritage » (OCs), interdits depuis des années mais entrainants toujours des effets délétères sur la biodiversité et (iii) le mercure (Hg), métal lourd non-essentiel ayant une origine à la fois anthropique et naturelle. Basé sur une approche corrélative in natura, je me suis intéressé aux conséquences physiologiques et comportementales d’une exposition chronique à ces trois grandes familles de contaminants présents chez la mouette tridactyle (Rissa tridactyla) de l’Arctique Norvégien (Svalbard) au cours de son cycle reproducteur (depuis l’accouplement jusqu’à l’élevage des poussins). Spécifiquement, j’ai étudié les relations entre ces contaminants et la fertilité (morphologie et motilité des spermatozoïdes), l’expression des signaux sexuels (visuel : coloration des téguments, olfactif : signature chimique), les comportements de soins parentaux (température d’incubation et rotation de l’œuf), le vieillissement cellulaire (longueur des télomères) et la dépense énergétique (métabolisme de base). Je me suis également penché sur de potentiels mécanismes sous-jacents permettant d’expliquer ces relations. Puisque ces mécanismes physiologiques et comportementaux sont fortement impliqués dans la valeur sélective des individus, les possibles conséquences à long terme de cette exposition sur la reproduction et survie des individus sont discutées. Ce travail permet de souligner la forte toxicité de certains composés organochlorés « historiques » (en particulier les chlordanes) et d’apporter de toutes nouvelles connaissances sur la toxicité très mal connue des PFASs chez la faune sauvage. Fait important, ce travail de thèse révèle que les PFASs et les OCs pourraient agir de manière contrastée sur plusieurs mécanismes physiologiques et traits comportementaux. Spécifiquement, une forte exposition à l’oxychlordane, un métabolite du chlordane, pesticide interdit depuis des décennies, est associée à des télomères plus courts, une réduction du métabolisme de base et à une moindre capacité à incuber les œufs. A l’inverse, on observe une élongation des télomères, une augmentation du métabolisme de base et une rotation des œufs accrue chez les individus les plus exposés aux PFASs. Le Hg, au moins en ce qui concerne les paramètres étudiés, ne semble pas jouer un rôle majeur. Cette étude souligne l'importance de tenir compte de plusieurs groupes de contaminants lorsqu'on étudie les conséquences de l'exposition aux contaminants environnementaux chez la faune sauvage. / Due to increasing human activities, a growing number of threats are challenging the fate of biodiversity. Among them, environmental contamination is particularly concerning for living organisms. Used and released in industrialized countries, these highly persistent contaminants can reach remote areas such as the Arctic ecosystem and will biomagnify though food webs and bioaccumulate in organisms. Long-lived seabirds are located in the upper levels of the food chains and thus particularly exposed and sensitive to a chronic contaminants exposure. Through endocrine disruption, these contaminants can impact physiological mechanisms and behavioural traits, inducing in fine, long-term fitness consequences on individuals and populations. My thesis focuses on three groups of contaminants: (i) poly- and perfluoroalkyl substances (PFASs), still broadly used in a vast array of industrial processes and increasing in the Arctic; (ii) “legacy” organochlorine contaminants (OCs, pesticides and industrial compounds), banned from use but still well present in the Arctic and (iii) mercury (Hg), a non-essential metal coming of both natural and anthropic origins. Based on a correlative approach conducted in natura, I investigated the physiological and behavioural consequences of exposure to these contaminants during the whole breeding cycle (from pre-laying to chick-rearing period) in an Arctic seabird, the black-legged kittiwake (Rissa tridactyla) from Svalbard, Norwegian Arctic. Specifically, I examined the relationships between several PFASs, OCs, Hg and fertility (sperm morphology and motility), sexual signaling (visual: integument coloration and olfactory: chemical signature), parental care behaviors (incubation temperature and egg-turning), ageing (telomere length) and energy expenditure (basal metabolic rate). In addition, some potential underlying mechanisms were also studied to better understand the way through which contaminants can be detrimental for kittiwakes. Furthermore, since physiological mechanisms and behavioral traits investigated here are tightly involved in self maintenance and reproduction, possible effects on fitness are then discussed. This PhD work underlines the major role of certain legacy chlorinated organic compounds (e.g. chlordanes) and significantly contributes at documenting the poorly known toxicological consequences of PFASs exposure in wildlife. Importantly, this PhD shows that PFASs and OCs could impact ageing, energy expenditure and some parental care behaviors in a contrasted manner. Specifically, oxychlordane, a metabolite of a banned organochlorine pesticide was associated with decreased telomere length, lowered metabolic rate and reduced ability to incubate the eggs. Conversely, elongated telomere, increased BMR and enhanced egg rotation were observed in birds bearing the highest concentrations of PFASs. Finally, at least for the considered endpoints, Hg appears as a coming minor threat for kittiwakes. This study highlights the importance of considering several groups of contaminants when investigating the consequences of environmental contaminants exposure in wildlife.

Decisões tomadas no planejamento da implantação florestal, como a densidade do plantio e o material genético, alteram a disponibilidade de recursos naturais tais como nutrientes, água e luz e consequentemente afetam a assimilação do carbono, que está diretamente relacionada ao crescimento da planta. Ainda são escassas as informações de como e quanto a densidade de plantio e o material genético afetam a fixação de carbono pelas ávores. O objetivo desse trabalho foi avaliar os padrões de fixação e alocação de carbono em plantações clonais de Eucalyptus sp. em duas densidades de plantio (3x2 m e 3x4 m), em um Latossolo Vermelho Distrófico T ípico A moderado. O estudo foi desenvolvido na Estação Experimental de Ciências Florestais de Itatinga-SP - ESALQ/USP, com três materiais clonais de Eucalyptus urophylla: AEC 0144, AEC 224 e COP 1404. O delineamento experimental utilizado foi em blocos casualizados, com esquema fatorial 3 x 2, sendo composto por três clones de eucalipto em dois espaçamentos, com 6 repetições para cada tratamento. Durante o intervalo de um ano (dos 40 aos 52 meses de idade) foram determinados a Produtividade Primária Líquida da Parte Aérea (ANPP: incremento da biomassa aérea somada ao folhedo), a Respiração Autotrófica da Parte Aérea (Rp: respiração das folhas e do tronco com base com base na ANPP, assumindo um valor constante de eficiência de uso do carbono (CUE) de 0,53 (GIARDINA et al., 2003)), o Fluxo de Carbono Abaixo do Solo (TBCF: produção e respiração das raízes grossas e finas, exsudatos das raízes e produção de substratos usados por micorrizas) e a Produtividade Primária Bruta (GPP: somatório dos fluxos de carbono) para os seis tratamentos avaliados. A maior produtividade encontrada para o clone AEC 0144 no espaçamento 3x2 m foi resultado de uma maior GPP (5997,45 g C m-2 ano-1), maior partição de carbono para incremento de tronco (30%) e menor partição da GPP para TBCF (34%). A ANPP variou de 1453,99 g C m-2 ano-1 (Clone COP 1404 no espaçamento 3x2 m) a 2288,78 g C m-2 ano-1 (Clone AEC 0144 no espaçamento 3x2 m), sendo os maiores fluxos encontrados para os clones AEC 0144 em ambos espaçamentos e para o clone COP 1404 no espaçamento 3x4 m. A variação encontrada nos valores de respiração da parte aérea seguiram o mesmo padrão dos resultados da ANPP. O TBCF foi significadamente superior para os clones AEC 0144 e AEC 224 no espaçamento 3x2 m com 2056,36 g C m-2 ano-1 e 1903,83 g C m-2 ano-1, respectivamente; e para o clone COP 1404 no espaçamento 3x4 m (1927,43 g C m-2 ano-1). Houve correlação positiva do TBCF com a GPP, mas não com a ANPP. / Decisions not planned for forest deployment, such as planting density and genetic material, alter the availability of natural resources such as nutrients, water and light and consequently affect the assimilation of carbon, which is directed to plant growth. They are still scarce as information on how and how much planting density and genetic material for a fixation of carbon by trees. The objective of this work was to evaluate the carbon allocation patterns in clonal plantations of Eucalyptus sp. in two planting densities (3x2 m and 3x4 m), in a typical Typic A moderate Dystrophic Red Latosol. The study was developed at the Experimental Station of Forest Sciences of Itatinga-SP - ESALQ / USP, with three clonal materials of Eucalyptus urophylla: AEC 0144, AEC 224 and COP 1404. The experimental design was a randomized complete block design with a factorial scheme 3 x 2, being composed of three clones of eucalyptus in two spacings, with 6 replicates for each treatment. During the one-year interval (from 40 to 52 months of age) was determined Aboveground Net Primary Productivity (ANPP: increase of the aerial biomass added to the litterfall), Aboveground Autotrophic Respiration (Rp: leaf respiration and (CUE) of 0.53 (GIARDINA et al., 2003)), Total Belowground Carbon Flux (TBCF: production and respiration of the roots) and Gross Primary Productivity (GPP: sum of the carbon fluxes) for the six treatments evaluated. The higher productivity found for the clone AEC 0144 in the 3x2 m spacing resulted from a higher GPP (5997.45 g C m-2 year-1), larger carbon partition for trunk increment (30%) and smaller partition from GPP for TBCF (34%). The ANPP ranged from 1453.99 g C m-2 year-1 (Clone COP 1404 in spacing 3x2 m) to 2288.78 g C m-2 year-1 (Clone AEC 0144 in 3x2 m spacing) Found for clones AEC 0144 in both spacings and COP 1404 in 3x4 m spacing. The variation found in aboveground autotrophic respiration values followed the same pattern of ANPP results. The TBCF was significantly higher for clones AEC 0144 and AEC 224 at 3x2 m spacing with 2056.36 m-2 year-1 and 1903.83 m-2 year-1, respectively; and for clone COP 1404 in 3x4 m spacing (1927.43 m-2 year-1). There was a positive correlation between TBCF and GPP, but not with ANPP.

The tropical rainforests of the Peruvian Andes are some of the most biodiverse and most vulnerable to climate warming in the world. The Andes are predicted to experience substantial increases in warming of between +2 °C to +5 °C by the end of the century, in addition to an increases in the frequency of high temperature extremes, drought and flood events. The response of these forests to climate change over the next century has global relevance, due to the high levels of endemic species present and the potential role these areas will play as refugia for lowland species. Despite this, the response of tropical montane forests (TMCFs) to climate change remains under-studied. Our current understanding of how Andean species will respond to climate change is based on studies of past compositional changes. Upslope shifts in plant communities of approximately 1.2 - 2.0 m·y-1 have been observed along elevational gradients within Central and South America over the last decade. Based on these migration rates, it has been estimated that the majority of communities will lag behind increases in temperature by 5.5 °C by the end of the century. The implications of this for populations at the trailing range edge is unclear, due to a lack of mechanistic data concerning the acclimatory limits of rainforest species. When faced with rapid warming plant species will need to rapidly adapt, acclimate or migrate in order to survive. In the case of Andean species, migration rates may not be sufficient for a species to remain within its optimal thermal niche and adaptive responses will likely be too slow to be effective, hence individuals will have to acclimate in situ to prevent a decline in performance. The acclimatory ability of species can be quantified by measuring changes in performance, leaf physiology and anatomy in response to experimental manipulations of climate, however such studies are rare within the tropics. Here we carried out a seedling transplant experiment, utilising an extensive 400-3500 m asl elevational gradient in the Peruvian Andes, to simulate climate warming and upslope migration of tree seedlings under real-world conditions. To provide context for the transplant study, natural variation in leaf anatomical traits and physiological stress were explored for twelve species belonging to lowland (LF), mid-elevation (LMF) and tropical montane cloud forest communities. Adults and seedlings from the centre and furthest-most extent of each species' elevational range were studied and compared. Seedlings of each elevational forest community were transplanted downslope and upslope of their local elevational range by the equivalent of ±2 °C and ±4 °C in mean annual temperature. The experiment followed the transplanted seedlings of eleven species over a one year period, monitoring survival, growth and physiological stress (Fv/Fm) of individuals. The acclimatory ability of a subset of these species was quantified by measuring changes in photosynthetic capacity (Vcmax and Jmax), respiratory capacity (Rd) and anatomical traits (Na, Pa, LMA, LDMC) in response to transplantation. The results showed that within the natural population there was little evidence of leaf trait acclimation to elevational shifts in climate, but also little evidence of physiological stress at the trailing range edge. There were however differences in the leaf trait strategies employed by each elevational community, increasing in abiotic stress-tolerance with elevation. Physiological stress was greatest in the seedling population and, unlike the adult population, increased slightly at the trailing edge. This indicated that seedlings were more vulnerable to warming than their adult counterparts and at mid-elevations TMCF seedlings were more vulnerable than LMF seedlings. Seedling survival and growth declined in response to transplantation away from the home elevation for the majority of species, with upslope declines as a result of abiotic limitations, and downslope declines due to biotic limitations. All seedlings were found to be able to acclimate their respiratory capacity in response to transplantation, however this was not the case for photosynthetic capacity. LMF species performed significantly better than TMCF seedlings with transplantation, demonstrating a greater acclimatory capacity for photosynthesis. LMF species were able to adjust Jmax in order to maintain rates at ambient temperatures, but were not able to upregulate Vcmax upslope, whereas TMCF species were not able to respond in either transplant direction. Overall, these findings suggest that under moderate warming scenarios LMF species will have a competitive advantage over TMCF species at mid-elevations, gradually expanding their range into TMCF species' habitat over the next century. As a result of this and due to the slow pace of upslope migration, we predict that TMCF species will undergo range retractions and possible extinctions. The speed of this response will be determined by the trajectory of future warming and the frequency of extreme climatic events.

Made available in DSpace on 2014-06-11T19:30:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-26Bitstream added on 2014-06-13T20:01:15Z : No. of bitstreams: 1 portes_mt_dr_rcla.pdf: 2079689 bytes, checksum: 765fd4860ab97b37290c8d8d62e1005f (MD5) / As restrições impostas pelo ambiente obrigam as plantas a transitarem entre estados fisiologicamente distintos, podendo tal transição ser representada pelo processo de aclimatação. O aparato fotossintético apresenta alta sensibilidade ao ambiente, mas possui alta capacidade de aclimatação, a qual é necessária dada a sua função essencial no metabolismo vegetal e o seu elevado nível de integração com outras vias metabólicas. A investigação do papel da aclimatação fotossintética na resposta a diversas condições ambientais, em diferentes espécies arbóreas, foi o principal tema de estudo da presente tese. Foram realizados experimentos com espécies arbóreas nativas e cultivadas sob diferentes níveis de controle ambiental, ou seja, no campo, em casa de vegetação e em câmaras de crescimento. Os experimentos com espécies arbóreas nativas envolveram a avaliação da capacidade de aclimatação das espécies de diferentes grupos sucessionais, as quais supostamente apresentam demandas luminosas distintas e diferem em sua habilidade de ajuste e acoplamento ao ambiente. O experimento com a espécie cultivada foi realizado com Eucalyptus globulus, e avaliou o efeito da deficiência hídrica em plantas sob diferentes regimes térmicos. A conjunção dos resultados obtidos nos quatro experimentos realizados permitiu verificar que a aclimatação do aparato fotossintético foi influenciada pelo ambiente de crescimento das plantas e pela estratégia ecológica das espécies, mais conservativa ou mais flexível. Além disso, foi verificado que a estratégia ecológica das espécies não está, necessariamente, relacionada ao seu grupo sucessional, conforme freqüentemente descrito na literatura. Os diversos ajustes no aparato fotossintético, descritos no presente trabalho em diferentes espécies e condições ambientais, demonstraram... / The constraints imposed by the environment compel plants to transit between distinct physiological states, represented by the acclimation process. The photosynthetic apparatus is highly sensitive to the environment, however it presents a high acclimation capacity which is necessary given its essential role in plant metabolism and high level of integration with other pathways. The investigation of the role of photosynthetic acclimation in response of different tree species to diverse environmental conditions was the main subject of the present study. Experiments with tropical tree species and cultivated species were performed under different levels of control of environmental conditions, i.e. in the field, in the greenhouse, and in growth chambers. The experiments with tropical tree species involved the evaluation of the acclimation capacity of species belonging to different ecological groups, supposedly presenting distinct light demands and ability to adjust and couple to the environment. The experiment with cultivated species was carried out with Eucalyptus globulus and photosynthetic acclimation was evaluated under water deficit, in plants under different thermal regimes. The conjunction of the results obtained in the four experiments performed suggests that the acclimation of the photosynthetic apparatus was influenced by the growth environment jointly with the ecological strategy of the species, more conservative or more flexible. Moreover, it was verified that the ecological strategy of the species is not necessarily related with its ecological group as often stated in the literature. The diverse changes in the photosynthetic apparatus described in the present study in different species and environmental conditions, demonstrated the importance and the contribution of the photosynthetic acclimation in the physiological adjustment of a plant to its current environmental condition... (Complete abstract click electronic access below)

[Truncated abstract] In south-western Australia a rare plant community occurs on shallow soils overlaying massive ironstone rock. These 'ironstone communities' are open shrublands, which are subject to extremes in drought and solar radiation and support many rare and endemic species. The restricted distribution of many of these species may be related to their high degree of specialisation to this harsh habitat and their inability to respond plastically to different environmental conditions. Indeed, earlier work has shown that ironstone Hakea species (Proteaceae) have a specialist root-system morphology investing mainly in deep roots, thereby increasing their chance of accessing cracks in the rock surface and obtaining water before the onset of summer drought. In this thesis I further examine aspects of specialisation and its possible consequences for species rarity using two ironstone Hakea species and comparing them with two of their widely distributed congeners. In the first experiment (Chapter 2) I explore inherent drought tolerance, independent of root-system morphology, as a further specialisation to the ironstone environment. All species were grown in sand in pots in a glasshouse for 7 months and then droughted for 5 weeks. There was no evidence that the ironstone species had a greater inherent drought tolerance than their common congeners. During drought all species maintained leaf water content of mature leaves by reducing stomatal conductance and osmotically adjusting, though ironstone species tended to OA (osmotic adjustment) more than common species. ... This suboptimal investment of resources may result in a lower competitive ability in shadier environments, and thus could partially explain their restricted distribution. In Chapter 4, I investigated the plasticity of root traits in response to levels of phosphorus supply. South-western Australian soils are phosphorus impoverished and phosphorus is well known to elicit plastic responses in root allocation and architecture. Ironstone species showed less plasticity in total root length, producing similar root length across P treatments, while common species showed an increase in root length with increasing [P]. Other root characteristics were similarly plastic in response to P treatment between species. However, when supplied with increasing [P], ironstone species invested an increasing proportion of roots in the bottom of pots while common species invested more in the top. This differential response in root allocation in response to P may reflect a fundamental trade-off between nutrient and water acquisition, with the ironstone species mainly foraging for water and investing in deeper roots, while the common species invest more in superficial roots to obtain nutrients. In conclusion, the rarity and restricted distribution of the ironstone Hakea species may be related to their specialist root-system morphology as well as a lowered phenotypic plasticity of functional traits. A reduction in plasticity may reduce their competitive ability outside their ironstone habitats, and thus contribute to the restricted distribution of these species. This may also be the case for other rock-outcrop endemics and more generally, for other rare plant species restricted to particular habitats where a lowered phenotypic plasticity in traits relevant to their particular habitat may contribute to their restricted distribution.

This dissertation investigates the relationship between Madagascar’s environment and the stress physiology of the red-bellied lemur, Eulemur rubriventer. Unique lemurid traits are proposed to have evolved in response to selection pressures unlike those in other primate habitats, and appear to be particularly suited to helping animals cope with harsh and unpredictable environments. Several hypotheses as to why lemurs evolved characteristics such as small group sizes, low basal metabolic rates, and cathemerality rest upon the untested assumption that these species are ecologically and/or reproductively stressed. This study simultaneously analyzes seasonal changes in climate, ecology, and the behavior and stress hormones (cortisol) of Eulemur rubriventer, as well as differences in these parameters across habitats with different ecological matrices. The goals of this dissertation are to: (1) evaluate the influences of seasonally varying food availability and climate upon lemur behavior and physiology, to determine whether such changes are sufficient to exert strong selective pressure; and (2) assess the additional influences of habitat composition and quality to evaluate the effects of unpredictability and habitat disturbance. Eulemur rubriventer are sensitive to seasonal environmental changes, as indicated by their time budgets, diets, and fecal cortisol levels. Overall they adopt a time minimizing strategy whereby energy is conserved by resting a majority of the time. Ripe fruit scarcity periods elicit the launch of an energy maximizing strategy whereby fecal cortisol levels and time feeding increase, and time resting decreases. Sensitivity to these influences varies across habitats. The behavioral and stress responses of groups in the undisturbed habitat (UND) were more seasonal and pronounced than those from their disturbed habitat (DIST) counterparts. Lower cortisol levels in DIST may result from a less seasonally predictable environment requiring frequent short-term responses (with possible energy deficits during critical reproductive stages yielding 3 deaths out of 5 births and out-of-season reproduction). Alternatively, the attenuated behavioral and hormonal response to environmental change in DIST may indicate a severely stressed population with insufficient energy to launch an appropriate coping response. The hypothesis that animals in DIST have adapted to frequent unpredictability due to disturbance is rejected because all animals behaviorally and hormonally respond to fruit declines, indicating that this species undergoes ecological stress. / text

Effect of soil moisture potential (?), temperature (T), genotype, seeding depth (SD) and rate (SR) on seedling emergence (SE), emergence velocity (EV), root yield and grades of cut and peel carrots were studied. SE was reduced at –120 kPa and totally inhibited at -156 kPa. EV was the lowest at – 5 kPa and – 90 kPa. SE was delayed by 33 d at 5°C, reduced at 30°C and totally inhibited at 35 and 40 °C. Heat units 99.75 and 159.60°Cd were the lowest to initiate and complete SE respectively while the optimum was 300 – 350 °Cd. There was no interaction effect between ? and T on SE. Honey snax at 85 seeds/ 30 cm showed the best SE whereas, Triton recorded the highest total yield at 2.54 cm SD and Fancy yield at 85 seeds/ 30 cm implying certain crop ecological and management factors can influence SE, root yield and quality.

Leaf shape is remarkably variable among plants, and hence likely has major consequence for ecological function and fitness. My thesis addresses the ecological significance of clinal variation for a leaf shape polymorphism in Ipomoea hederacea (lobed leaves dominate the north, entire-shaped leaves restricted to the south), and investigates the role of adaptation and demography in shaping its evolutionary history in its eastern North American range. To evaluate the adaptive value of the cline, I surveyed leaf shape genotypes from 77 populations , and found a steep latitudinal leaf shape cline that was not reflected in 173 neutral genetic markers. Furthermore, the leaf shape locus was a genomic outlier, implicating divergent selection in generating or maintaining the cline. I investigated the thermoregulatory and freezing tolerance properties of the leaf shape genotypes, and discovered that lobed leaves remain marginally warmer at night, and a 1°C decrease separated mildly damaged and severely frost damaged tissue, potentially suggesting that a critical ambient temperature could drive differential leaf shape damage. I further explored three additional hypothesized selective agents (insect herbivores, flowering phenology and growth), and showed that these putative agents impose selection on I. hederacea, but do not differentiate between leaf shapes. These studies highlighted the challenge of identifying selective agents, even for a polymorphic trait with hypothesized selective mechanisms. To understand the contribution of adaptation and demography in shaping I. hederacea’s evolutionary history, I sequenced 7 nuclear loci from 192 individuals sampled from 24 populations and characterized patterns of nucleotide diversity. I demonstrated that I. hederacea is genetically structured in patches consistent with long-distance dispersal, genetically depauperate, and undergoing range expansion, suggesting a recent founder event or metapopulation dynamics. My thesis represents a comprehensive evaluation of the key processes affecting a polymorphism that influences plant morphology, geographical distribution, and population history.

Leaf shape is remarkably variable among plants, and hence likely has major consequence for ecological function and fitness. My thesis addresses the ecological significance of clinal variation for a leaf shape polymorphism in Ipomoea hederacea (lobed leaves dominate the north, entire-shaped leaves restricted to the south), and investigates the role of adaptation and demography in shaping its evolutionary history in its eastern North American range. To evaluate the adaptive value of the cline, I surveyed leaf shape genotypes from 77 populations , and found a steep latitudinal leaf shape cline that was not reflected in 173 neutral genetic markers. Furthermore, the leaf shape locus was a genomic outlier, implicating divergent selection in generating or maintaining the cline. I investigated the thermoregulatory and freezing tolerance properties of the leaf shape genotypes, and discovered that lobed leaves remain marginally warmer at night, and a 1°C decrease separated mildly damaged and severely frost damaged tissue, potentially suggesting that a critical ambient temperature could drive differential leaf shape damage. I further explored three additional hypothesized selective agents (insect herbivores, flowering phenology and growth), and showed that these putative agents impose selection on I. hederacea, but do not differentiate between leaf shapes. These studies highlighted the challenge of identifying selective agents, even for a polymorphic trait with hypothesized selective mechanisms. To understand the contribution of adaptation and demography in shaping I. hederacea’s evolutionary history, I sequenced 7 nuclear loci from 192 individuals sampled from 24 populations and characterized patterns of nucleotide diversity. I demonstrated that I. hederacea is genetically structured in patches consistent with long-distance dispersal, genetically depauperate, and undergoing range expansion, suggesting a recent founder event or metapopulation dynamics. My thesis represents a comprehensive evaluation of the key processes affecting a polymorphism that influences plant morphology, geographical distribution, and population history.