Cryptic diversity in southern African kelp.

Area of Science:

• Marine Biology
• Genetics
• Ecology

Background:

• The southern African coast is a unique region with predicted future cooling.
• It hosts two closely related kelp species, Ecklonia maxima and Ecklonia radiata, with distinct thermal niches.
• E. maxima has recently expanded its range, leading to potential species overlap.

Purpose of the Study:

• To investigate the genetic structure of Ecklonia kelp species along the southern African coast.
• To identify potential hybridization events between E. maxima and E. radiata.
• To explore cryptic diversity within the Ecklonia genus in this region.

Main Methods:

• Utilized nuclear microsatellite markers to analyze genetic structure.
• Employed mitochondrial markers to trace evolutionary history.
• Compared genetic data with historical distribution and morphological records.

Main Results:

• Identified geographically distinct genetic clusters for both E. maxima and E. radiata.
• Discovered unique genetic diversity in depth-isolated populations, including a third Ecklonia lineage.
• Observed mito-nuclear discordance and high genetic divergence in contact zones, indicating hybridization.

Conclusions:

• Hybridization is occurring between Ecklonia species in response to changing environmental conditions.
• Cryptic diversity exists within Ecklonia, with potential implications for conservation.
• Abiotic factors may drive convergent phenotypes, complicating species identification.