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Molecular phylogeny of Asian Ardisia (Myrsinoideae, Primulaceae) and their leaf-nodulated endosymbionts, Burkholderia s.l. (Burkholderiaceae).

ABSTRACT: The genus Ardisia (Myrsinoideae, Primulaceae) has 16 subgenera and over 700 accepted names, mainly distributed in tropical Asia and America. The circumscription of Ardisia is not well-defined and sometimes confounded with the separation of some small genera. A taxonomic revision focusing on Ardisia and allies is necessary. In the Ardisia subgenus Crispardisia, symbiotic association with leaf-nodule bacteria is a unique character within the genus. The endosymbionts are vertically transmitted, highly specific and highly dependent on the hosts, suggesting strict cospeciation may have occurred in the evolutionary history. In the present study, we aimed to establish a phylogenetic framework for further taxonomic revision. We also aimed to test the cospeciation hypothesis of the leaf-nodulate Ardisia and their endosymbiotic bacteria. Nuclear ITS and two chloroplast intergenic spaces were used to reconstruct the phylogeny of Asian Ardisia and relatives in Myrsinoideae, Primulaceae. The 16S-23S rRNA were used to reconstruct the bacterial symbionts' phylogeny. To understand the evolutionary association of the Ardisia and symbionts, topology tests and cophylogenetic analyses were conducted. The molecular phylogeny suggested Ardisia is not monophyletic, unless Sardiria, Hymenandra, Badula and Oncostemum are included. The results suggest the generic limit within Myrsinoideae (Primulaceae) needs to be further revised. The subgenera Crispardisia, Pimelandra, and Stylardisia were supported as monophyly, while the subgenus Bladhia was separated into two distant clades. We proposed to divide the subgenus Bladhia into subgenus Bladhia s.str. and subgenus Odontophylla. Both of the cophylogenetic analyses and topology tests rejected strict cospeciation hypothesis between Ardisia hosts and symbiotic Burkholderia. Cophylogenetic analyses showed general phylogenetic concordance of Ardisia and Burkholderia, and cospeciation events, host-switching events and loss events were all inferred.

SUBMITTER: Yang CJ

PROVIDER: S-EPMC8769342 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe taxonomy and systematics of Salix subgenus Salix s.l. is difficult. The reliability and evolutionary implications of two important morphological characters (number of stamens, and morphology of bud scales) used in subgeneric classification within Salix remain untested, and a disjunct Old-New World distribution pattern of a main clade of subgenus Salix s.l., revealed by a previous study, lacks a reasonable explanation. To study these questions, we conducted phylogenetic analyses based on 4,688 bp of sequence data from four plastid (rbcL, trnD-T, matK, and atpB-rbcL) and two nuclear markers (ETS and ITS) covering all subgenera of Salix, and all sections of subgenus Salix s.l.ResultsSubgenus Salix came out as para- or polyphyletic in both nrDNA and plastid trees. The plastid phylogeny successfully resolved relationships among the major clades of Salix, but resolution within subgenus Salix s.l. remained low. Nevertheless, three monophyletic groups were identifiable in subgenus Salix s.l.: the 'main clade' of subgenus Salix s.l., with New and Old World species being reciprocally monophyletic; the section Triandroides clade; and the subgenus Pleuradenia clade. While nrDNA regions showed higher resolution within subgenus Salix s.l., they failed to resolve subgeneric relationships. Extensive, statistically significant gene-tree incongruence was detected across nrDNA-plastid as well as nrDNA ETS-ITS phylogenies, suggesting reticulate evolution or hybridization within the group. The results were supported by network analyses. Ancestral-state reconstructions indicated that multiple stamens and free bud scales represent the plesiomorphic states within Salix, and that several significant shifts in stamen number and bud scale morphology have occurred.ConclusionsSubgenus Salix s.l. is not monophyletic, and the evolutionary history of the subgenus has involved multiple reticulation events that may mainly be due to hybridization. The delimitation of subgenus Salix s.l. should be redefined by excluding section Triandrae and subgenus Pleuradenia from it. The evolutionary lability of bud-scale morphology and stamen number means that these characters are unreliable bases for classification. The disjunct Old-New World distribution of subgenus Salix s.l. appears to be linked to the profound climatic cooling during the Tertiary, which cut off gene exchange between New and Old World lineages.

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Dataset Information

Molecular phylogeny of Asian Ardisia (Myrsinoideae, Primulaceae) and their leaf-nodulated endosymbionts, Burkholderia s.l. (Burkholderiaceae).

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