Publication: Estudio taxonómico integrativo del complejo Trichostomum brachydontium Bruch (Pottiaceae, Bryophyta) en Sudamérica: implicaciones en la sistemática y diversidad del género Trichostomum Bruch
Authors
Rodríguez Alcalá, Omar
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Escuelas::Escuela Internacional de Doctorado
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Cano Bernabé, María Jesús ; Gallego Morales, María Teresa
Publisher
Universidad de Murcia
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DOI
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info:eu-repo/semantics/doctoralThesis
Description
Abstract
La taxonomía integrativa se ha establecido como una herramienta fundamental para la delimitación de especies en grupos taxonómicos complejos. Un ejemplo es la familia Pottiaceae, conocida por su alta diversidad y riqueza específica. Esto es especialmente evidente en las regiones tropicales de Sudamérica, las cuales permanecen aún poco exploradas desde una perspectiva taxonómica. Dentro del grupo, la subfamilia Trichostomoideae incluye géneros de morfología compleja y poco estudiados, como Trichostomum. En Sudamérica, T. brachydontium es la especie más citada, aunque estudios preliminares evidencian una notable variabilidad fenotípica que sugiere la presencia de diversidad críptica o pseudocríptica. El objetivo principal de esta investigación fue clarificar la diversidad real del género Trichostomum en Sudamérica, con énfasis en el complejo T. brachydontium, y establecer su posición filogenética dentro de Trichostomoideae. Para ello, se analizaron morfológicamente más de 300 ejemplares de herbario y se seleccionaron 111 para estudios filogenéticos, utilizando marcadores del genoma cloroplástico (atpB-rbcL, rps4, trnG, trnL-F) y nuclear (ITS1-5.8S-ITS2). Esto fue complementado con análisis estadísticos multivariantes (análisis de componentes principales, análisis discriminante lineal y análisis de conglomerados jerárquico).
Los análisis filogenéticos revelaron que los géneros incluidos en la tribu Trichostomeae se agrupan en dos clados bien apoyados, aunque no se identificaron sinapomorfías. La posición filogenética de Trichostomum platyphyllum resultó ambigua, ya que se agrupa con Trichostomum en los árboles de genes nucleares y fuera de Trichostomum en los cloroplásticos, lo que impide confirmar la monofilia del género. Del mismo modo, la posición de Hydrogonium mostró incongruencias entre los árboles de genes cloroplásticos y nucleares. Además, se observó una clara diferenciación entre los especímenes europeos y macaronésicos de T. brachydontium y los sudamericanos. Estos últimos distribuidos en once clados bien definidos, algunos con señales de reticulación, lo que evidencia la complejidad evolutiva de este grupo.
El estudio integrativo permitió excluir de Sudamérica a T. brachydontium y a Tainoa subcucullata. Además, se delimitaron nueve especies del complejo T. brachydontium en Sudamérica: T. basilatinervium, T. churchillianum, T. edentulum, T. goyazense, T. hondurense, T. lambii, T. mittenianum, T. novogranatense y T. urceolare, siendo las dos primeras nuevas para la ciencia, y describiéndose por primera vez el esporófito de T. hondurense. Dos de los clados no pudieron ser delimitados taxonómicamente: uno debido a su alta variabilidad morfológica y otro por la falta de estudios adicionales. En este estudio también se presentan dos nuevos caracteres morfológicos de utilidad taxonómica que hasta ahora no habían sido considerados dentro del género Trichostomum: el porcentaje de ocupación de la zona hialina basal y el de la zona de transición. Adicionalmente, se proponen tres nuevas combinaciones (T. loxorhynchum, T. goyazense y Neotrichostomum jamaicense), siete nuevos sinónimos (Gymnostomum jamesonii para T. loxorhynchum; T. apophysatulum y T. pomangium para T. edentulum; Weissia termitarum para T. goyazense; Didymodon planifolius para T. hondurense e Hymenostomum anomalum y T. antillarum para T. urceolare), y seis nuevos lectótipos. Por otro lado, se actualiza el hábitat y la distribución de cada una de las especies reconocidas, con un aumento considerable de su rango de distribución, ya que la mayoría solo se conocían del material original de la localidad tipo.
Los resultados obtenidos confirman la eficacia de la taxonomía integrativa para comprender la biodiversidad en grupos complejos como los briófitos. En el caso de T. brachydontium en Sudamérica, la combinación de análisis morfológicos y moleculares permitió delimitar y caracterizar una parte importante de las especies. Futuros estudios que incluyan una mayor representación de los grupos no resueltos determinarán la diversidad real en este complejo de especies.
Integrative taxonomy has been established as a fundamental tool for species delimitation in taxonomically complex groups. One example is the Pottiaceae family, known for its high diversity and species richness. This is especially evident in the tropical regions of South America, which remain largely unexplored from a taxonomic perspective. Within this group, the subfamily Trichostomoideae, includes genera with complex and poorly studied morphologies, such as Trichostomum. In South America, T. brachydontium is the most frequently cited species, however, preliminary studies have revealed notable phenotypic variability, suggesting the presence of cryptic or pseudocryptic diversity. The main objective of this research was to clarify the real diversity of the genus Trichostomum in South America, particularly within the T. brachydontium complex, and establish its phylogenetic position within Trichostomoideae. To this end, over 300 herbarium specimens were analyzed morphologically, and 111 were selected for phylogenetic studies, using plastid genome markers (atpB-rbcL, rps4, trnG, and trnL-F) and nuclear markers (ITS1-5.8S-ITS2). These were complemented by multivariate statistical analyses (principal components analysis, linear discriminant analysis and hierarchical cluster analysis) Phylogenetic analyses revealed that the genera included in the tribe Trichostomeae are grouped into two well-supported clades, although no synapomorphies were identified. The phylogenetic position of Trichostomum platyphyllum was ambiguous, as it clustered with Trichostomum in nuclear gene trees, but outside of Trichostomum in chloroplast trees, preventing confirmation of the monophyly of the genus. Similarly, the position of Hydrogonium showed incongruences between the plastid and nuclear gene trees. Furthermore, a clear differentiation was observed between European and Macaronesian specimens of T. brachydontium and those from South America. The latter were distributed across eleven well-defined clades, some with signs of reticulation, which demonstrates the evolutionary complexity of this group. The integrative approach enabled T. brachydontium and Tainoa subcucullata to be excluded from South America. Additionally, nine species belonging to the T. brachydontium complex were identified in South America: T. basilatinervium, T. churchillianum, T. edentulum, T. goyazense, T. hondurense, T. lambii, T. mittenianum, T. novogranatense and T. urceolare. The first two species are new to science and the sporophyte of T. hondurense is described for the first time. Two of the clades could not be taxonomically delimited: one due to high morphological variability, and the other due to a lack of further studies. Furthermore, this study proposes two new morphological characters of taxonomic value that had not previously been considered within the genus Trichostomum: the percentage of occupancy of the basal hyaline zone and of the transition zone. Additionally, three new combinations (T. loxorhynchum, T. goyazense and Neotrichostomum jamaicense), seven new synonyms (Gymnostomum jamesonii for T. loxorhynchum; T. apophysatulum and T. pomangium for T. edentulum; Weissia termitarum for T. goyazense; Didymodon planifolius for T. hondurense and Hymenostomum anomalum and T. antillarum for T. urceolare), and six new lectotypes are proposed. In addition, the habitat and distribution of each of the recognized species is updated, with a considerable increase in their distribution range, since most were only known from the original material from the type locality. The results obtained confirm the effectiveness of integrative taxonomy for understanding biodiversity in complex groups such as bryophytes. In the case of T. brachydontium in South America, the combination of morphological and molecular analyses made it possible to delimit and characterize a significant portion of the species. Future studies that include greater representation of unresolved groups will determine the real diversity in this species complex.
Integrative taxonomy has been established as a fundamental tool for species delimitation in taxonomically complex groups. One example is the Pottiaceae family, known for its high diversity and species richness. This is especially evident in the tropical regions of South America, which remain largely unexplored from a taxonomic perspective. Within this group, the subfamily Trichostomoideae, includes genera with complex and poorly studied morphologies, such as Trichostomum. In South America, T. brachydontium is the most frequently cited species, however, preliminary studies have revealed notable phenotypic variability, suggesting the presence of cryptic or pseudocryptic diversity. The main objective of this research was to clarify the real diversity of the genus Trichostomum in South America, particularly within the T. brachydontium complex, and establish its phylogenetic position within Trichostomoideae. To this end, over 300 herbarium specimens were analyzed morphologically, and 111 were selected for phylogenetic studies, using plastid genome markers (atpB-rbcL, rps4, trnG, and trnL-F) and nuclear markers (ITS1-5.8S-ITS2). These were complemented by multivariate statistical analyses (principal components analysis, linear discriminant analysis and hierarchical cluster analysis) Phylogenetic analyses revealed that the genera included in the tribe Trichostomeae are grouped into two well-supported clades, although no synapomorphies were identified. The phylogenetic position of Trichostomum platyphyllum was ambiguous, as it clustered with Trichostomum in nuclear gene trees, but outside of Trichostomum in chloroplast trees, preventing confirmation of the monophyly of the genus. Similarly, the position of Hydrogonium showed incongruences between the plastid and nuclear gene trees. Furthermore, a clear differentiation was observed between European and Macaronesian specimens of T. brachydontium and those from South America. The latter were distributed across eleven well-defined clades, some with signs of reticulation, which demonstrates the evolutionary complexity of this group. The integrative approach enabled T. brachydontium and Tainoa subcucullata to be excluded from South America. Additionally, nine species belonging to the T. brachydontium complex were identified in South America: T. basilatinervium, T. churchillianum, T. edentulum, T. goyazense, T. hondurense, T. lambii, T. mittenianum, T. novogranatense and T. urceolare. The first two species are new to science and the sporophyte of T. hondurense is described for the first time. Two of the clades could not be taxonomically delimited: one due to high morphological variability, and the other due to a lack of further studies. Furthermore, this study proposes two new morphological characters of taxonomic value that had not previously been considered within the genus Trichostomum: the percentage of occupancy of the basal hyaline zone and of the transition zone. Additionally, three new combinations (T. loxorhynchum, T. goyazense and Neotrichostomum jamaicense), seven new synonyms (Gymnostomum jamesonii for T. loxorhynchum; T. apophysatulum and T. pomangium for T. edentulum; Weissia termitarum for T. goyazense; Didymodon planifolius for T. hondurense and Hymenostomum anomalum and T. antillarum for T. urceolare), and six new lectotypes are proposed. In addition, the habitat and distribution of each of the recognized species is updated, with a considerable increase in their distribution range, since most were only known from the original material from the type locality. The results obtained confirm the effectiveness of integrative taxonomy for understanding biodiversity in complex groups such as bryophytes. In the case of T. brachydontium in South America, the combination of morphological and molecular analyses made it possible to delimit and characterize a significant portion of the species. Future studies that include greater representation of unresolved groups will determine the real diversity in this species complex.
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11-oct-2026
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