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Host-Associated Differentiation in an Insect CommunityDickey, Aaron 2010 December 1900 (has links)
Host-Associated Differentiation (HAD) is the formation of genetically divergent hostassociated
lineages maintained by ecological isolation. HAD is potentially an important
route to ecological speciation in parasites including many insects. While HAD case
studies are accumulating, there is a dearth of negative results in the literature making it
difficult to know how common the phenomenon really is or whether there are specific
traits of parasites which promote HAD. To address these two problems, studies are
needed which both publish negative results (i.e., parasites not showing HAD) and test
for HAD in multiple parasite species on the same pair of host species (i.e., control for
host plant effects).
In this study, HAD was tested in three species of herbivorous insects and one parasitoid
species on the same two host tree species: pecan and water hickory. The insects were
selected based on the presence or absence of two traits, parthenogenesis and endophagy.
A test for HAD was considered “positive” when population substructure was explained
by host-association. To test for the presence of HAD, insects were sampled sympatrically to eliminate geographical isolation as a confounding factor, sampling was
replicated spatially to assure that HAD persisted, and multiple loci were sampled from
each individual. Genetic data was analyzed using cluster analyses. HAD was found in
both pecan leaf phylloxera and yellow pecan aphid but not in pecan bud moth or in the
parasitoid of the yellow pecan aphid, Aphelinus perpallidus. Interestingly, both taxa
showing HAD are parthenogenetic and both taxa not showing HAD reproduce sexually.
Species showing HAD were tested for the presence of a pre-mating reproductive
isolating mechanism (RIM) which could be maintaining HAD despite the potential for
gene flow. Selection against migrants to the alternative host was tested in yellow pecan
aphid using a no-choice fitness experiment. The overall contribution of this RIM to total
isolation was positive and ranged from 0.614 to 0.850. The RIM of “habitat preference”
was tested in pecan leaf phylloxera using a dual-choice preference experiment. In this
species, preference was only detected for phylloxera originating from water hickory
suggesting that host discrimination ability may be a less important factor promoting
differentiation in phylloxera.
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Efeito da heteroplasmia na densidade celular e desenvolvimento embrionário in vitro de embriões bovinos clonados por transferência nuclear de célula somática / Effect of heteroplasmy on cell density and in vitro development of bovine embryos cloned by somatic cell nuclear transferMezzalira, Joana Claudia 25 September 2009 (has links)
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Previous issue date: 2009-09-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In somatic cell nuclear transfer (SCNT), the type of the recipient cytoplast plays a key role on
nuclear reprogramming. Distinct cytoplasts and karyoplasts and different activation
protocols were used for bovine embryo cloning aiming to evaluate the effect of the type of
cytoplast (oocyte and/or zygote) and the activation protocol (chemical, AQ, or spermatic, AE)
on development of cloned blastocysts produced by handmade cloning (HMC). After 17 h of in
vitro maturation (MIV), 2,946 oocytes were enucleated by manual bisection resulting in either
MII cytoplasts (enucleated) or MII karyoplasts (non-enucleated). An additional group of
2,368 oocytes, in vitro-fertilized (FIV) for 6 h, were manually bisected and segregated in
either FIV cytoplasts (enucleated) or FIV karyoplasts (non-enucleated). Cells from a primary
culture previously established from a skin biopsy from an adult female bovine were used as
nuclei donors (karyoplast CS). Structures were allocated to (a) control groups: FIV;
parthenogenesis using zona-intact (PG c/) or zona-free oocytes (PG s/); and clones by SCNT;
or (b) experimental groups: G1, FIV cytoplast + MII cytoplast + CS karyoplast; G2, MII
cytoplast + FIV karyoplast; G3, FIV cytoplast + FIV karyoplast; G4, FIV cytoplast + FIV
cytoplast + CS karyoplast; and G5, MII cytoplast + MII karyoplast. Following electrofusion,
experimental groups G1 to G5 were allocated to sub-groups of either sperm-mediated (AE) or
additional chemical (AQ) activation. The in vitro culture was carried out in the WOW (wellof-
the-well) system. After 20 replications, cleavage (D2) and blastocyst (D7) rates were
compared by the χ2 test, with values for total cell number and cell allocation in the blastocyst,
determined by differential staining, being evaluated by ANOVA, with pairwise comparisons
by the Tukey test, for P<0.05 (P<0.05). The only experimental group that yielded a blastocyst
development similar to the FIV (27.0%) and SCNT (31.4%) control groups was the subgroup
G1 AE (28.2%). This fact may be attributed to a more proper synchrony between the
karyoplast and cytoplasts and/or to a more suitable activation process. Embryo development
in subgroups G1 AQ (13.7%), G4 AQ (6.4%) and G4 AE (8.7%) was lower than in G1 AE,
possibly due to a higher degree of asynchrony in the activation process or cell cycle. The lack
of development in groups G2 and G3, irrespective of the activation protocol, was possibly due
to the manipulation process during a highly sensible biological period. Likewise, the low
cleavage (57.0%) and the lack of development in group G5 (spontaneous activation) in fact
showed that the manipulation induced weak spontaneous oocyte activation. In general, total
cell number and cell allocation were similar between groups with development to the
blastocyst stage. In conclusion, the activation process appeared to be as important to embryo
development as the type of cytoplast or karyoplast used for embryo reconstruction. The
production of cloned bovine embryos using a more physiological activation process (AE) was
proven as a viable procedure, with efficiency rates observed in subgroup G1 AE being similar
to groups FIV or TNCS / Na clonagem por transferência nuclear com célula somática (TNCS), o tipo de citoplasto
receptor desempenha papel chave na reprogramação nuclear. Distintos citoplastos e
carioplastos e condições de ativação foram utilizadas na reconstrução de embriões bovinos
com o objetivo de avaliar o efeito do tipo de citoplasto (oócito e/ou zigoto) e do método de
ativação (química, AQ, ou espermática, AE) no desenvolvimento de blastocistos clonados
produzidos pela técnica de clonagem manual (Handmade Cloning, HMC). Após 17 h de
maturação in vitro (MIV), 2.946 oócitos foram enucleados por bissecção manual, resultando
em hemi-oócitos enucleados (citoplastos MII) e não enucleados (carioplastos MII). Outros
2.368 oócitos submetidos a 6 h de fecundação in vitro (FIV) foram bisseccionados
manualmente e segregados em hemi-zigotos enucleados (citoplastos FIV) e não enucleados
(carioplastos FIV). Células de um cultivo celular estabelecido a partir da biópsia auricular de
uma fêmea bovina adulta foram utilizadas como núcleos doadores (carioplasto CS). As
estruturas foram dispostas em (a) grupos controle: FIV; partenogênese com oócitos com (PG
c/) ou sem zona pelúcida (PG s/); e clone por TNCS; ou (b) grupos experimentais: G1,
citoplasto FIV + citoplasto MII + carioplasto CS; G2, citoplasto MII + carioplasto FIV; G3,
citoplasto FIV + carioplasto FIV; G4, citoplasto FIV + citoplasto FIV + carioplasto CS; e G5,
citoplasto MII + carioplasto MII. Após a eletrofusão das estruturas, os grupos experimentais
G1 a G45 foram divididos em subgrupos de AQ ou AE. O cultivo in vitro foi realizado pelo
sistema WOW (well-of-the-well). Após 20 repetições, as taxas de clivagem (D2) e blastocisto
(D7) foram comparadas pelos testes de χ2 e os valores para o número total de células e a
alocação das linhagens celulares nos blastocistos, determinados por coloração diferencial,
foram avaliados por análise de variância, com pareamento comparativo pelo teste de Tukey,
para P<0,05. O único grupo experimental que apresentou desenvolvimento embrionário no
D7 semelhante aos controles FIV (27,0%) e TNCS (31,4%) foi o subgrupo G1 AE (28,2%).
Isso pode ser atribuído a uma melhor sincronia do ciclo celular entre citoplastos e/ou
carioplasto e um mais adequado processo de ativação. O desenvolvimento embrionário nos
grupos G1 AQ (13,7%), G4 AQ (6,4%) e G4 AE (8,7%) foi menor do que o G1 AE,
possivelmente devido à assincronia do processo de ativação ou ciclo celular. O
desenvolvimento embrionário nulo dos grupos G2 e G3, independente da ativação,
possivelmente foi decorrente da manipulação das estruturas em um momento biologicamente
sensível. Da mesma forma, a baixa clivagem (57,0%) e o desenvolvimento nulo no grupo G5
de ativação espontânea demonstraram de fato que a manipulação estimulou o processo de
ativação embrionária de forma sub-limiar. Em geral, não houve diferença no número de
células e alocação celular nos grupos onde houve desenvolvimento até o estádio de
blastocisto. Conclui-se que o processo de ativação foi tão significativo para o
desenvolvimento embrionário que o tipo de citoplasto e carioplasto usados na reconstrução
embrionária. A produção de embriões clones com um método mais fisiológico de ativaçao
(AE) mostrou-se como um procedimento viável, obtendo-se no grupo G1 AE a mesma
eficiência observada na FIV ou na TNCS
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A Plio-Pleistocene Record of Lacustrine Ostracodes from Butte Valley, California: Faunal Responses to Tectonic and Climatic ChangeMathias, Frank Furlong, Jr. 29 July 2014 (has links)
No description available.
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Effets de la reproduction partiellement asexuée sur la dynamique des fréquences génotypiques en populations majoritairement diploïdes / Effects of partial asexuality on the dynamics of genotype frequencies in dominantly diploid populationsReichel, Katja 10 December 2015 (has links)
Les systèmes reproducteurs déterminent comment le matériel génétique est transmis d’une génération à la suivante […]. Les espèces qui combinent de la reproduction sexuée et asexuée/clonale sont très répandues [… mais] l’effet de leur système reproducteur sur leur évolution reste énigmatique et discuté.L’objectif de cette thèse est de modéliser la dynamique des fréquences génotypiques d’une population avec une combinaison de reproduction sexuée et/ou clonale dans des cycles de vie principalement diploïdes [. … Un] modèle du type chaine de Markov avec temps et états discrets sert de base mathématique pour décrire [leurs] changements […] au cours du temps.Les résultats montrent que la reproduction partiellement asexuée peut en effet modifier la dynamique de la diversité génomique par rapport à une reproduction strictement sexuée ou strictement asexuée. […] L’histoire démographique a un rôle important pour les organismes partiellement clonaux et doit être prise en compte dans toute analyse […].Cette thèse fait des recommandations pour la collecte des données et une hypothèse de base pour l’interprétation des données de génétique/génomique […]. Ces résultats ont des retombées dans plusieurs domaines, allant de la recherche fondamentale […] à des applications en agriculture […], pêche […] et protection de la nature […]. / Reproductive systems determine how genetic material is passed from one generation to the next, making them an important factor for evolution. Organisms that combine sexual and asexual/clonal reproduction are very widespread [… yet] the effects of their reproductive system on their evolution are still controversial and poorly understood.The aim of this thesis was to model the dynamics of genotype frequencies under combined sexual/clonal reproduction in dominantly diploid life cycles [. … A] state and time discrete Markov chain model served as the mathematical basis to describe [their] changes […] through time.The results demonstrate that partial clonality may indeed change the dynamics of genomic diversity compared to either exclusively sexual or exclusively clonal populations. […] Time has a crucial role in partially clonal populations and needs to be taken into account in any analysis of their genomic diversity.This thesis provides recommendations for data collection and a null hypothesis for the interpretation of population genetic/genomic data […]. Moreover, it includes new methods for the analysis of genotype-based population genetic Markov chain models. These results have a high potential relevance in several areas, ranging from basic research […] to applications in agriculture […], fisheries […] and nature conservation […].
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Phylum TardigradaNelson, Diane R., Guidetti, Roberto, Rebecchi, Lorena 01 January 2015 (has links)
A sister group of the Arthropoda, the Tardigrada are micrometazoans that occupy a diversity of niches in freshwater, marine, and terrestrial habitats. Commonly called water bears because of their slow, lumbering gait, these molting lobopods have four pairs of legs, usually terminating in claws. Most are less than 1 mm in length, with a complete digestive tract, a dorsal gonad with one or two gonoducts, and a dorsal lobed brain with a ventral nerve cord and four bilobed ganglia, one per leg-bearing metamere. The body cavity (hemocoel) functions in respiration and circulation. Over 1200 species have been described based primarily on the morphology of the claws and buccal-pharyngeal apparatus. Individuals may be either gonochoric, unisexual, or hermaphroditic, with fertilized or unfertilized eggs deposited either freely or within the shed exuvium. Parthenogenesis occurs frequently in limnic and terrestrial tardigrades, allowing them to colonize new territories by passive dispersal of a single individual. Cryptobiosis (anhydrobiosis, anoxybiosis, cryobiosis, and osmobiosis) and diapause (encystment and resting eggs) occur during the life history. Active adults (surrounded by water) and cryptobiotic adults and eggs are primarily dispersed passively, but some active dispersal can also occur. Due to the characteristic patchy distributions of tardigrade populations, little is known about their population dynamics and trophic relationships. Improved methods for collection, microscopy, culturing, and molecular analyses have been have contributed much to our knowledge of tardigrades.
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Clonal diversity and population genetic structure of the grain aphid Sitobion avenae(F.) in central Europe / Klonale Diversität und populationsgenetische Struktur der Großen Getreidelaus Sitobion avenae (F.) in ZentraleuropaReimer, Lars 16 July 2004 (has links)
No description available.
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