Genic rather than genome-wide differences between sexually deceptive Ophrys orchids with different pollinators

Area of Science:

• Evolutionary Biology
• Genomics
• Plant Science

Background:

• Sexually deceptive orchids are ideal models for studying ecological speciation due to pollinator specificity and genetic influences on attraction.
• Changes in floral scent are hypothesized to play a key role in the speciation process within these orchids.

Purpose of the Study:

• To investigate reproductive barriers and floral phenotype differences in four closely related, coflowering Ophrys species.
• To utilize genotyping-by-sequencing (GBS) to assess genomic differentiation among these Ophrys species.

Main Methods:

• Surveyed reproductive barriers including pollinator (floral) and flowering time (temporal) isolation.
• Employed genotyping-by-sequencing (GBS) to analyze genome-wide differentiation.
• Conducted genome scans for FST outliers to identify highly differentiated genetic markers.

Main Results:

• Ophrys species exhibit strong floral isolation due to distinct pollinators and moderate temporal isolation, with minimal postpollination barriers.
• GBS revealed extensive shared polymorphism and low population structure across the Ophrys genome.
• Genome scans identified few highly differentiated markers, particularly in genes related to floral scent production, suggesting a genic basis for divergence.

Conclusions:

• Ecological speciation in these orchids is primarily driven by genetic changes affecting floral scent, rather than broad genomic divergence.
• These findings indicate that Ophrys species are in the early stages of genomic divergence within the speciation continuum.
• The study highlights the role of specific genes in pollinator attraction and reproductive isolation, shaping early speciation events.