[Phylogenetic relationships of seabuckthorn based on ITS sequences]

Area of Science:

• Plant taxonomy
• Molecular systematics
• Phylogenetics

Background:

• Seabuckthorn (Hippophae) species are vital in arid and semi-arid regions.
• Accurate species identification and classification are crucial for conservation and utilization.
• Previous classifications relied heavily on morphology, which can be ambiguous.

Purpose of the Study:

• To investigate the phylogenetic relationships among three Hippophae species using internal transcribed spacer (ITS) DNA sequences.
• To compare molecular data with existing morphological classifications.
• To clarify the taxonomic status of various Hippophae taxa.

Main Methods:

• DNA extraction and sequencing of the internal transcribed spacer (ITS) region from 15 Hippophae samples.
• Phylogenetic analysis using ITS sequences, with Elaeagnus angustifolia as an outgroup.
• Cluster analysis to determine genetic relationships and divergences.

Main Results:

• ITS sequences varied from 600 to 605 bp, with distinct lengths for ITS-1, 5.8S, and ITS-2 regions.
• Remarkably high sequence divergence was observed among the studied seabuckthorn species.
• Phylogenetic analysis suggested reclassification of H. gonicocarpa subsp. litangensis and H. gonicocarpa subsp. goniocarpa into distinct species (H. gonicocarpa and H. litangensis).
• H. gyantsensis showed a close genetic relationship with H. salicifolia and a distant one with H. rhamnoides subsp. sinensis.
• Molecular data contradicted traditional morphological classifications for nine subspecies of H. rhamnoides.

Conclusions:

• ITS sequence analysis provides a robust method for resolving seabuckthorn taxonomy.
• Molecular data supports distinct species status for taxa previously grouped under H. gonicocarpa.
• Phylogenetic relationships derived from ITS sequences differ significantly from morphological classifications, necessitating taxonomic revisions.