Les interactions avec les pollinisateurs font partie de la niche écologique des orchidées et ont joué un rôle dans leur diversification taxonomique et florale. Au cours de cette thèse, j’ai d’abord analysé l’architecture du réseau orchidées-pollinisateurs en région Euro-Méditerranéenne et montré que la similarité de niches de pollinisation entre orchidées était fonction de leur distribution spatio-temporelle, suggérant un certain opportunisme dans les interactions orchidées-pollinisateurs. Je me suis ensuite intéressée au rôle des pollinisateurs dans l'évolution des traits floraux dans deux groupes d’orchidées. J’ai d’abord montré une différentiation dans les traits floraux des trois taxa du groupe Anacamptis coriophora, probablement causée et maintenue par un processus de sélection divergente. En cartographiant les interactions avec les pollinisateurs et les odeurs florales sur la phylogénie de la section Pseudophrys, j’ai ensuite montré que l'évolution de l'odeur florale était conditionnée par une sélection exercée par les pollinisateurs et par des contraintes phylogénétiques. Enfin, j’ai mis au point une démarche de taxonomie intégrative basée sur des données moléculaires, morphométriques et chimiques dans le genre Ophrys. Avec cette démarche, j’ai confirmé le rang taxonomique des trois espèces du groupe O. insectifera et proposé de fusionner deux paires d’espèces parmi les Pseudophrys. Une meilleure compréhension des facteurs qui façonnent la niche de pollinisation et du rôle des pollinisateurs dans l'évolution des traits floraux et la spéciation chez les orchidées Euro-Méditerranéennes devrait nous permettre d’améliorer la conservation de ces espèces emblématiques. / Interactions with pollinators are part of orchids’ ecological niches and have played a role in their taxonomic and floral diversification. During this thesis, I have analysed the architecture of the orchid-pollinator network in the Euro-Mediterranean region and shown that similarity in pollination niches between orchids primarily depends on their spatio-temporal distribution, suggesting that orchid-pollinator interactions are more opportunistic than previously thought. Then, I have been interested in the role of pollinators in floral trait evolution in two orchid groups. I have shown a differentiation in floral traits of the three taxa of the Anacamptis coriophora group, probably caused and maintained by a process of divergent selection. Then, by mapping interactions with pollinators and floral odours on the phylogeny of the section Pseudophrys, I have shown that floral odour evolution is conditioned by pollinator-mediated selection and by phylogenetic constraints. Finally, I have developed an integrative taxonomic approach based on molecular, morphometric and chemical data in the genus Ophrys. With this approach, I have confirmed the taxonomic rank of the three species of the O. insectifera group and proposed to merge two species pairs among Pseudophrys. A better understanding of the factors that have shaped pollination niches and of the role of pollinators in floral trait evolution and speciation in Euro-Mediterranean orchids should allow us to improve the conservation of these emblematic species.

No description available.

<p dir="ltr">In this era of changing global climate and globalization, the intricate relationships between non-native organisms and their impacts on forest health are of paramount concern. Bark and ambrosia beetles are diverse groups of insects that are among the most intercepted insects at international ports of entry. Once established, these insects can vector pathogens and disrupt functional forest dynamics. Bark and ambrosia beetles are known to attack various tree species, including black walnut (<i>Juglans nigra</i>), a valuable timer and nut-producing tree native to Eastern North America. Non-native woodboring beetles provide unique opportunities for ecological studies and pest management. This research investigates the chemical ecology and microbial dynamics in black walnut ecosystems to fill critical knowledge gaps and address the pressing issues surrounding forest health and sustainable management.</p><p dir="ltr">In Chapter 1, I review the current literature describing the use of semiochemicals in bark and ambrosia beetle management, non-native scolytines as vectors of phytopathogens, and the use of nematodes as natural antagonists of fungal pathogens in trees.</p><p dir="ltr">In Chapter 2, I aim to identify attractant and repellent semiochemicals for the ambrosia beetle <i>Anisandrus maiche</i>, which is a first step in developing effective management strategies for this species. I found that conophthorin and verbenone are strong repellents and that this beetle is attracted to ethanol in a dose-dependent manner.</p><p dir="ltr">In Chapter 3, I tested the hypothesis that <i>Anisandrus maiche </i>will be influenced by volatiles of its nutritional fungal symbiont, <i>Ambrosiella cleistominuta,</i> and that these compounds may synergize with ethanol. I identified seven unique compounds from the fungus and two fungal alcohols in the field. I found isobutyl alcohol to repel <i>A. maiche </i>while isoamyl alcohol has seasonal effects on <i>A. maiche </i>capture when paired with ethanol.</p><p dir="ltr">In Chapter 4, I aimed to characterize the assemblage of microorganisms residing on two non-native ambrosia beetles across diverse forest types. I tested the hypothesis that forest stand diversity and management regimes would affect the assemblage of microorganisms of ambrosia beetles. I found forest type influences the abundance of fungi and bacteria on <i>A. maiche </i>and <i>Xylosandrus crassiusculus</i> and that both beetle species transport genera of pathogenic fungi.</p><p dir="ltr">In Chapter 5, I test the hypothesis that inoculation with <i>Geosmithia morbida </i>alters the volatile profile of black walnut. I found one isolate of <i>G. morbida </i>induced changes in the volatile profile of black walnut bark and identified the compounds that changed relative to the control trees.</p><p dir="ltr">In Chapter 6, I tested the hypothesis that free-living fungivorous nematodes can modulate Thousand Cankers Disease severity. I found two genera of nematodes <i>Panagrolaimus </i>and <i>Aphelenchoides </i>to orient towards agents of the TCD system in Y-tube bioassays. <i>Aphelenchoides </i>sp. that were exposed to <i>G. morbida </i>grown on agar media augmented with black walnut bark extract significantly reduced <i>G. morbida </i>cankers in black walnut seedlings. This research has important implications for the management of TCD.</p><p dir="ltr">In Chapter 7, I summarize results from each of research chapter and discuss future research needs and directions to continue development of the knowledge surrounding chemical ecology and microbial dynamics of non-native scolytine beetles.</p>

Säbelzahnfrösche (Anura: Odontobatrachidae) sind eine Gruppe von fünf, in Westafrika endemische Wildbachspezialisten, die einzigartige Merkmale wie große Fangzähne und eine Drüse im Unterkiefer zeigen. Die Drüse enthält flüchtige Kohlenwasserstoffe, die Insektenpheromonen ähneln. Ziel dieser Dissertation war es, die Drüse formal zu beschreiben und ihre Funktion zu ermitteln. Das erste Kapitel untersuchte die Biologie der Frösche und enthüllte Standorttreue und Revierverhalten, insbesondere bei Männchen. Verletzungen deuteten auf aggressive Interaktionen hin, insbesondere in der Nähe von Brutplätzen. Die Frösche nutzen wassergefüllte Spalten zur Eiablage, was auf komplexe Paarungs- und Lebensrauminteraktionen hindeutet. In Bezug auf die Funktion der Drüse ergaben sich zwei Hypothesen: intraspezifische Kommunikation zur Koordinierung der Eiablage oder interspezifische Kommunikation zum Anlocken von Beutetieren. Im zweiten Kapitel wurde die Ernährung untersucht, und belegte ein generalistisches Fressverhalten, was die Hypothese der intraspezifischen Kommunikation widerlegte. Das dritte Kapitel konzentrierte sich auf das akustische Repertoire und zeigte einen artspezifischen Werberuf bei den Männchen und unerwartete Quäken bei den Weibchen. Entgegen den Annahmen war die akustische Kommunikation bei Säbelzahnfröschen ausgeprägt und nicht eingeschränkt. Im vierten Kapitel wurden die Anatomie und die chemische Zusammensetzung der Drüse untersucht. Die Drüse, ist bereist bei Jungtieren vorhanden und bei variiert bei erwachsenen Tieren. Chemisch weist sie eine artspezifische Zusammensetzung auf, die je nach Geschlecht und Fortpflanzungszustand variiert. Zusammenfassend ist Wahrscheinlich, dass Säbelzahnfrösche multimodal kommunizieren und akustische und chemische Signale kombinieren, um Paarung und Eiablage zu koordinieren. Diese einzigartige Drüse und ihr Sekret deuten darauf hin, dass chemische Kommunikation bei Fröschen weiter verbreitet ist als bisher angenommen. / Saber-toothed Frogs (Anura: Odontobatrachidae) are a group of five torrent specialists endemic to West Africa. Recent descriptions revealed unique features such as large fangs and a gland in the lower jaw containing volatile hydrocarbons resembling insect pheromones. This dissertation aimed to formalize the description of the gland and ascertain its function. The first chapter delved into to frogs’ biology, unveiling site loyalty, and territorial behaviors, especially in males. Injuries suggested aggressive interactions, particularly around breeding habitats. The frogs use water-filled crevices for egg deposition, hinting at complex mating and habitat interactions. Two main hypotheses emerged regarding gland function: intraspecific communication for coordination during oviposition and fertilization, or interspecific communication to attract prey. The second chapter explored the diet to support the latter hypothesis. Findings showed a generalist diet and significant amounts of leaflets from a specific tree, indicating an unprecedented plant uptake. This refuted the idea of attracting specific prey and supported intraspecific communication. The third chapter focused on the acoustic repertoire, revealing a species-specific advertisement call in males and unexpected squeaking calls in females. Contrary to assumptions, acoustic communication in Saber-toothed frogs was pronounced and not restricted. The fourth chapter examined the gland's anatomy and chemical composition. The gland, present in juveniles and varying in adults, exhibited species-specific compositions varying with sex and reproductive state. In conclusion, Saber-toothed Frogs most likely employ multimodal communication, combining acoustic and chemical signals to coordinate mating and oviposition. The unique gland and its secretion hint at a more widespread use of chemical communication in frogs than previously recognized.

The aim of this thesis was to isolate the compounds responsible for the antibacterial activity of cell extracts of the marine diatom, Phaeodactylum tricornutum. Marine microalgae are not only important primary producers but, due to their phylogenetic diversity, they are also a potential source of novel bioactive compounds. The marine diatom, P. tricornutum, was selected for study because its cell extracts are known to be antibacterial but the compounds responsible have not been isolated. In this thesis, the compounds responsible for the antibacterial activity are isolated from aqueous methanol P. tricornutum cell extracts by column chromatography and reverse phase high-performance liquid chromatography using a bioassay-guided approach. The compounds in three active fractions were identified by mass spectrometry and nuclear magnetic resonance spectroscopy as the unsaturated fatty acids (5Z, 8Z, 11Z, 14Z, 17Z)-eicosapentaenoic acid, (9Z)-hexadecenoic acid and (6Z, 9Z, 12Z)-hexadecatrienoic acid. The fatty acids were found to be antibacterial against Staphylococcus aureus at micromolar concentrations. P. tricornutum exists in different cell morphs and, interestingly, extracts prepared from cultures in the fusiform morph were found to have greater antibacterial activity than extracts from oval cultures. This is explained by greater levels of the three antibacterial fatty acids in the fusiform cell extracts. The antibacterial fatty acids are proposed to be released by enzyme action when the diatom cells lose their integrity. The release of free fatty acids by diatoms is suggested to be a simple, very low cost population-level activated defence mechanism against potential pathogenic bacteria triggered when the cell loses its integrity. Further, this pathway may act against multiple threats to the microalga, including grazers, as fatty acids exhibit activity in diverse biological assays. Finally, whilst two of the fatty acids, (9Z)-hexadecenoic acid and (5Z, 8Z, 11Z, 14Z, 17Z)-eicosapentaenoic acid, inhibited the growth of MRSA their usefulness as therapeutic compounds may be limited due to their instability and their broad biological activity.

Neste trabalho objetivou-se estudar o comportamento de acasalamento de Cyrtomon luridus Boheman (Coleoptera: Curculionidae), bem como a presença de semioquímicos mediando o acasalamento e a interação com a planta hospedeira Duboisia sp. (Solanaceae). Machos e fêmeas adultos recém-emergidos foram coletados no campo e levados para o laboratório. Incialmente foi determinado o melhor parâmetro morfológico para diferenciação de machos e fêmeas. Verificou-se que machos deste curculionídeo possuem a abertura genital oclusa pelo último tergito. O comportamento de acasalamento foi observado em casais virgens durante nove dias. Verificou-se que machos e fêmeas de C. luridus atingiram a maturidade sexual dois dias após a emergência. Machos e fêmeas realizaram acasalamentos repetidos com o mesmo parceiro em qualquer horário do dia. O comportamento de acasalamento deste curculionídeo foi dividido nas fases pré-copulatória, copulatória e pós-copulatória. Além disso, estudos de olfatometria revelaram que machos e fêmeas de C. luridus foram fortemente atraídos por voláteis de machos se alimentando sobre a planta hospedeira. A coleta e análise destes voláteis revelaram a presença dos compostos (Z)-3-hexenal, hexanal, (E)-2-hexenal, (E)-2-hexen-1-ol, fenilacetaldeido, linalol e geraniol, como eletrofisiologicamente ativos. O presente trabalho traz importantes informações sobre o comportamento de acasalamento e ecologia química de Entiminae e servirão de base para estudos com outras espécies desta importante subfamília de Curculionidae. / This work aimed to study the mating behavior of Cyrtomon luridus Boheman (Coleoptera: Curculionidae), as well as the presence of semiochemicals mediating the mating and the interaction of the insects with the host plant, Duboisia sp. (Solanaceae). Newly emerged males and females adults were collected in the field and taken to the laboratory. Initially it determined the best morphological parameter to differentiate males and females. It was found that males possess the genital opening occluded by the last tergite. The mating behavior was observed in virgin couples for nine days. It was found that males and females C. luridus reached sexual maturity two days after emergence. Males and females made repeated matings with the same partner at any time of day. The mating behavior was clearly divided into the pre-copulatory, copulatory, and post-copulatory phases. In addition, olfatometrics studies revealed that males and females C. luridus were strongly attracted to volatile males feeding on the host plant. The collection and analysis of these volatiles revealed the compounds (Z)-3-hexenal, hexanal, (E)-2-hexenal, (E)-2-hexen-1-ol, phenylacetaldehyde, linalool and geraniol as being eletrophysiologically. The present work brings important information about the mating behavior and chemical ecology of Entiminae, which will serve as support for studies with other species of this important subfamily of Curculionidae.

A capacidade de discriminação entre indivíduos geneticamente relacionados é de fundamental importância na teoria de Hamilton da Seleção Parental. Insetos sociais utilizam-se do olfato no reconhecimento, sendo os compostos presentes na cutícula dos indivíduos os responsáveis por esta mediação. Nesses insetos as pistas utilizadas no sistema de reconhecimento podem provir de diversas fontes distintas, tanto endógenas quanto exógenas. As pistas exógenas podem ser absorvidas a partir de materiais de construção do ninho, alimentos ou da rainha. Apesar de existir uma grande literatura a respeito dessa aquisição em formigas, cupins, abelhas melíferas e abelhas solitárias, pouco se sabe a respeito de abelhas sem ferrão. Dessa forma, o presente estudo teve como principais objetivos a análise da composição química cuticular da abelha sem ferrão Frieseomelitta varia (Lepeletier, 1836) e a verificação da influência da alimentação e dos materiais de construção do ninho na formação dos sinais utilizados nos sistemas de reconhecimento e defesa. Foram identificados um total de 48 compostos presentes na cutícula de F. varia. Dentre esses compostos os mais comuns foram hidrocarbonetos, divididos em alcanos, alcenos e alcadienos. Os hidrocarbonetos variaram de 21 a 31 átomos de carbono e os encontrados em maiores concentrações foram o heptacosano e o nonacosano. Os compostos variaram de acordo com a casta, o gênero e a idade dos indivíduos. Os testes comportamentais, juntamente com as análises químicas indicaram que os indivíduos absorvem compostos químicos a partir dos materiais do ninho. No entanto, foi mostrado que a convergência alimentar não resulta em uma maior aceitação dos indivíduos nem em uma convergência de compostos cuticulares. / The ability to discriminate among genetic related individuals has a main importance in the Kin selection Hamiltons theory. Social insects use odor cues in recognition systems, and the main used cues are compounds present in their cuticle. These cues may originate from endogenous and exogenous sources. The exogenous cues may be absorbed from nest materials, food or even from the queen. There are numerous reports concerning the origin of these cues in ants, termites, honeybees and solitary bees, although, little is known about stingless bees. Therefore, the present work had as main objectives the study of the chemical composition of Frieseomelitta varias cuticle and the verification of food and nest materials influence in the constitution of the cues used in recognition systems. A total of 48 compounds were identified in the cuticle of F. varia. The main compounds were hydrocarbons, divided into alkanes, alkenes and alkadienes. The hydrocarbons varied from 21 to 31 carbon atoms and those found in highest concentrations were heptacosane and nonacosane. The compounds varied between castes, gender and age. The behavioral tests, in agreement with the chemical analyses, showed that the individuals absorb chemical compounds from nest material. However, the results showed that food convergence imply neither in a higher acceptance of the individuals nor in a chemical convergence.

As respostas comportamentais do bicudo-do-algodoeiro aos compostos orgânicos voláteis de plantas em fase vegetativa, plantas com botão floral, botão floral, flor e maçã e plantas em floração do algodoeiro, e a presença dos semioquímicos que responsáveis pela interação inseto-planta foram investigadas neste trabalho. Todos os experimentos foram realizados em condições de laboratório usando insetos criados em dieta artificial e planta cultivadas em casa de vegetação. Bioensaios usando olfatômetro em ípsilon demonstraram que macho são atraídos pelos voláteis das plantas em fase vegetativa e flores, e as fêmeas pelos voláteis das flores e plantas em floração. Ambos os sexos do bicudo-do-algodoeiro não foram traídos pelos voláteis de planta com botão floral, botão flora e maçã. Compostos voláteis destes tratamentos foram coletados por oito horas e analisados por GC-MS, revelando 13 compostos liberados pelas plantas em floração e 11 nas flores e plantas em fase vegetativa. As plantas em sus respectivas fases de desenvolvimento liberam maiores quantidades de compostos que as flores. As antenas de machos e fêmeas foram eletrofisiologicamente responsivas aos extratos voláteis destes tratamentos, confirmando o mesmo padrão de resposta observado nos bioensaios de olfatometria. Os compostos sintéticos &beta;-caryophyllene e cis-3-hexenyl-acetate presentes em maiores quantidades em plantas em floração não foram atrativos para as fêmeas na concentração utilizada nos bioensaios de olfatometria. Os resultados encontrados neste trabalho demonstram que machos e fêmeas exploram os compostos orgânicos voláteis liberados pelas diferentes fases desenvolvimento da planta e pelas flores, aportando assim, com novas evidencias sobre a interação entre A. grandis e seu principal hospedeiro, G. hirsutum, abrindo a possibilidade de realizar novos estudos visando a aplicabilidade de estes semioquímicos no monitoramento e controle deste importante inseto-praga. / The behavioral responses of the cotton boll weevil to the volatile organic compounds of plants in the vegetative stage, plants with square, squares, flower, boll and flowering plants of cotton, and the presence of semiochemicals responsible for the insect-plant interaction were investigated in this work. All experiments were carried out in laboratory conditions using insects raised in artificial diet and plant grown under greenhouse conditions. Y-tube olfactometer bioassays showed that male were attracted by volatiles of plants in vegetative phase and flowers, and the females by flowers and flowering plants volatiles. Both sexes of the cotton boll weevil were not attracted by plant with squares, squares and boll volatiles. Volatile compounds of these treatments were collected for eight hours and analyzed by GC-MS, revealing 13 compounds released by flowering plants and 11 by flowers and plants in the vegetative stage. Plants in their respective stages of development release larger amounts of compounds than flowers. Male and female antennae were electrophysiologically responsive to the volatile extracts of these treatments, confirming the same response pattern observed in the olfactory bioassays. The synthetic compounds &beta;-caryophyllene and cis-3-hexenyl-acetate present in larger quantities at flowering plants were not attractive for females at the concentration used in Y-tube olfactometer bioassays. The results obtained in this work demonstrate that males and females exploit the volatile organic compounds released by cotton plant at different development stages and by the flowers, thus contributing with new evidence about the interaction between A. grandis and their major host plant, G. hirsutum, which will serve as support for studies aiming at the applicability of these semiochemicals in the monitoring and control of the cotton boll weevil.

Opogona sacchari (Bojer, 1856) (Lepidoptera: Tineidae) é uma praga cosmopolita conhecida popularmente como traça-da-banana. Este trabalho visou conhecer as principais etapas do comportamento sexual de O. sacchari, e isolar quimicamente os compostos de seu feromônio sexual. Para caracterizar as atividades do comportamento sexual, 80 casais recém-emergidos foram observados e dados sobre o horário de início e fim, duração, idade do primeiro acasalamento e número de cópulas foram registrados. O extrato natural do feromônio sexual foi obtido por (i) aeração das fêmeas virgens, e (ii) extração das glândulas das fêmeas virgens. Os extratos naturais foram analisados por GC/EAG utilizando as antenas dos machos para avaliar as atividades eletrofisiológicas; os extratos foram também analisados em GC/MS. As cópulas ocorreram a partir da sexta hora da escotofase, com duração de aproximadamente 2 horas. Os adultos acasalaram com até 72 h de idade, com o pico das atividades com 24 horas após a emergência. As antenas dos machos apresentaram três respostas eletroantenográficas (picos) ao extrato do feromônio natural de fêmeas virgens. O composto \"C1\" foi selecionado como candidato ao feromônio sexual de O. sacchari. Quatro isômeros do composto candidato ao feromônio sexual promoveram respostas eletrofisiológicas nas antenas dos machos, idênticas ao extrato natural das fêmeas. Novas etapas envolvendo testes de campo deverão ser realizadas a fim de definir os compostos ativos deste feromônio e em quais proporções serão mais eficientes na atração dos machos. / Opogona sacchari (Bojer, 1856) (Lepidoptera: Tineidae) is a cosmopolitan crop pest, commonly known as banana moth. The goals of this study were to investigate the stages of sexual behavior for O. sacchari and to isolate their sex pheromone. In order to characterize the sexual behavior, 80 newly emerged sexual pairs were observed and data on their age, duration and frequency of mating\'s were recorded. The natural sex pheromone was extracted by (i) headspace collection of virgin females, and (ii) gland extraction of virgin females. Extracts were analyzed by GC/EAD using male antennae to monitor electrophysiological activity; extracts were also analyzed by GC/MS. Copulation occurs from the sixth hour of the scotophase and lasts approximately 2 hours. Adults mate for up to 72 hours, with the peak of sexual activity at 24 hours after emergence. Male antennae showed three electroantennogram responses (peaks) to extracts of virgin females. The putative sex pheromone was identified as \"C1\". Four isomers of this pheromone candidate promoted electrophysiological response as the same natural female extract. New steps involving field tests will be carried out to define the active component of this pheromone and proportions most effective for male attraction.

Delisea pulchra is a red macroalga that produces furanones, a class of secondary metabolites that inhibit the growth and colonization of a range of micro- and macroorganisms. In bacteria, furanones specifically inhibit acyl homoserine lactone (AHL)- driven quorum sensing, which is known to regulate a variety of colonization and virulence traits. This thesis aims to unveil multiple aspects of the chemically mediated interactions between an alga and its bacterial flora. It was demonstrated that the quorum sensing genetic machinery of bacteria is laterally transferred, making traditional 16S rRNA gene based-diversity techniques poorly suited to identify quorum sensing species. Previous studies had shown that AHL-producing bacteria belonging to the roseobacter clade can be readily isolated from D. pulchra. Because of this, it was decided to use a roseobacter epiphytic isolate from this alga, Ruegeria strain R11, to conduct a series of colonization experiments on furanone free and furanone producing D. pulchra. Furanones were shown to inhibit Ruegeria strain R11's colonization and infection of D. pulchra. In addition, it was demonstrated that Ruegeria strain R11 has temperature-regulated virulence, similar to what is seen for the coral pathogen Vibrio shiloi. Rising ocean temperatures may explain bleached D. pulchra specimens recently observed at Bare Island, Australia. To assess whether quorum sensing is common within the roseobacter clade, cultured isolates from the Roseobacter, Ruegeria and Roseovarius genera were screened for AHL production. Half of the bacteria screened produced the quorum sensing signal molecules, AHLs. These AHLs were identified using an overlay of an AHL reporter strain in conjunction with thin layer chromatography (TLC). The prevalence of quorum sensing within the roseobacter clade, suggests that these species may occupy marine niches where cellular density is high (such as surface associated communities on substratum and marine eukaryotes). Diversity studies in marine microbial communities require appropriate molecular markers. The 16S rRNA gene is the most commonly used marker for molecular microbial ecology studies. However, it has several limitations and shortcomings, to which attention has been drawn here. The rpoB gene is an alternate ???housekeeping??? gene used in molecular microbial ecology. Therefore, the phylogenetic properties of these two genes were compared. At most taxonomic levels the 16S rRNA and rpoB genes offer similar phylogenetic resolution. However, the 16S rRNA gene is unable to resolve relationships between strains at the subspecies level. This lack of resolving power is shown here to be a consequence of intragenomic heterogeneity.