Los antocerotes tuberosos de Chile Central y sus simbiontes cianobacteriales
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Date
2024
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Abstract
Las interacciones mutualistas con microorganismos han sido fundamentales en la historia evolutiva de las plantas terrestres, las que han promovido la diversificación de los grandes linajes de plantas. Estas interacciones han resultado en una diversidad de patrones de especialización. Los briófitos son un grupo de plantas terrestres altamente derivadas, que incluye a los antocerotes, una división que interactúa ubicuamente con simbiontes cianobacteriales (cianobiontes) del género Nostoc, capaces de fijar nitrógeno. Los estudios previos sobre especialización de estas interacciones han abarcado una baja diversidad de antocerotes, ninguno de los cuales transmite verticalmente los cianobiontes. En este trabajo nos centramos en los antocerotes tuberosos de Chile central. Phaeoceros carolinianus y Phaeoceros microsporus forman tubérculos de manera facultativa y se distribuyen ampliamente, mientras que la tercera especie, Paraphymatoceros diadematus, forma tubérculos constitutivamente, aloja cianobiontes al interior de los tubérculos y es endémica de Chile central ¿Existe algún grado de especialización entre P. diadematus y sus cianobiontes? ¿Influye la retención de cianobiontes al interior de los tubérculos en los patrones de diversidad de los cianobiontes? Proponemos que, dado que la especie P. diadematus retiene en los tubérculos cianobiontes con mayor frecuencia que las otras especies de antocerotes tuberosos, la transmisión vertical generará patrones de especialización. Hallamos bajos niveles de especialización por especificidad hacia el subclado 3 de Nostoc, cuya abundancia como cianobionte parece reflejar su abundancia en el suelo. Finalmente exploramos la función ecosistémica de estos antocerotes, la que constituyó una novedosa fuente de fertilidad no considerada previamente en Chile central.
Mutualistic interactions with microorganisms have been central in the evolutionary history of terrestrial plants, promoting the diversification of major plant lineages. These interactions have led to a variety of specialization patterns. Bryophytes constitute a highly derived group of terrestrial plants, including hornworts, a division that ubiquitously interacts with Nostoc cyanobacterial symbionts (cyanobionts), capable of nitrogen fixation. Previous studies on the specialization of these interactions have focused on a limited diversity of hornworts, none of which vertically transmit cyanobionts. This study specifically targets the tuberous hornworts of central Chile, comprising three species. Two of these species, Phaeoceros carolinianus and Phaeoceros microsporus, facultatively form tubers and are widely distributed, while the third species, Paraphymatoceros diadematus, consistently forms tubers, harbours cyanobionts within them, and is endemic to central Chile. We address the following questions in this study: Is there any degree of specialization between P. diadematus and its cyanobionts? Does the retention of cyanobionts within tubers influence cyanobiont diversity patterns? We propose the hypothesis that, given that P. diadematus retains cyanobionts in tubers more frequently than other tuberous hornwort species, vertical transmission will generate specialization patterns. We found low levels of specialization toward the sub-clade 3 of Nostoc, and its abundance as a cyanobiont appears to reflect its abundance in the soil. In the final part of the study, we explore the ecosystem function of tuberous hornworts in the biological soil crust dominated by ephemeral bryophytes in Mediterranean ecosystems of Central Chile, representing a novel nitrogen fertility source for ecosystems not previously considered in the past.
Mutualistic interactions with microorganisms have been central in the evolutionary history of terrestrial plants, promoting the diversification of major plant lineages. These interactions have led to a variety of specialization patterns. Bryophytes constitute a highly derived group of terrestrial plants, including hornworts, a division that ubiquitously interacts with Nostoc cyanobacterial symbionts (cyanobionts), capable of nitrogen fixation. Previous studies on the specialization of these interactions have focused on a limited diversity of hornworts, none of which vertically transmit cyanobionts. This study specifically targets the tuberous hornworts of central Chile, comprising three species. Two of these species, Phaeoceros carolinianus and Phaeoceros microsporus, facultatively form tubers and are widely distributed, while the third species, Paraphymatoceros diadematus, consistently forms tubers, harbours cyanobionts within them, and is endemic to central Chile. We address the following questions in this study: Is there any degree of specialization between P. diadematus and its cyanobionts? Does the retention of cyanobionts within tubers influence cyanobiont diversity patterns? We propose the hypothesis that, given that P. diadematus retains cyanobionts in tubers more frequently than other tuberous hornwort species, vertical transmission will generate specialization patterns. We found low levels of specialization toward the sub-clade 3 of Nostoc, and its abundance as a cyanobiont appears to reflect its abundance in the soil. In the final part of the study, we explore the ecosystem function of tuberous hornworts in the biological soil crust dominated by ephemeral bryophytes in Mediterranean ecosystems of Central Chile, representing a novel nitrogen fertility source for ecosystems not previously considered in the past.
Description
Tesis (Doctor en Ciencias con mención en Ecología)--Pontificia Universidad Católica de Chile, 2024
Keywords
Interacciones mutualistas, Especialización, Antocerotes, Cianobacterias, Tubérculos, Mutualistic interactions, Specialization, Hornworts, Cyanobacteria, Tubers