Apomixis and reticulate evolution in the Asplenium monanthes fern complex

Area of Science:

• Plant evolutionary biology
• Fern reproductive strategies
• Genetics and genomics

Background:

• Asexual reproduction (apomixis) is common in ferns, with up to 10% of species potentially reproducing this way.
• Previous research identified two triploid, apomictic species within the Asplenium monanthes complex.
• Understanding the evolution of apomixis is crucial for plant lineage diversification.

Purpose of the Study:

• To investigate the phylogenetic relationships within the Asplenium monanthes species complex.
• To determine the occurrence and evolutionary pathways of apomixis in this group.
• To identify progenitor species involved in the evolution of apomixis.

Main Methods:

• Phylogenetic analyses using DNA sequences from plastid and nuclear markers.
• Assessment of reproductive modes through gametophytic and sporophyte development.
• Inference of polyploidy levels using spore size measurements.

Main Results:

• Apomixis confirmed in Asplenium monanthes and A. resiliens, and identified in A. palmeri, A. hallbergii, and A. heterochroum relatives.
• Apomixis is restricted to two main clades associated with A. monanthes and A. resiliens.
• Reticulate evolution is linked to the occurrence of apomixis, with two apomictic lineages and two sexual progenitors identified in the A. monanthes clade.

Conclusions:

• Apomixis has originated multiple times within the Asplenium monanthes and A. resiliens clades.
• Both alloploid and autoploid forms of apomixis have evolved in these fern lineages.
• The study clarifies the complex evolutionary history of apomixis in Asplenium ferns.