Phenotypic plasticity in macroalgal distribution: A case study on Gelidium corneum (Florideophyceae, Rhodophyta)

Area of Science:

• Marine biology
• Ecology
• Phycology

Background:

• Geographically isolated populations adapt to local environmental pressures, driving unique phenotypic traits for enhanced adaptability.
• Ocean warming intensifies selective pressures on marine species.
• The red alga Gelidium corneum, dominant in northern Iberian marine forests, shows declining biomass, particularly in its eastern range, making it a model for studying adaptive processes.

Purpose of the Study:

• To investigate adaptive processes in Gelidium corneum populations along a temperature gradient.
• To assess phenotypic differences and growth capacity in response to varying thermal conditions.

Main Methods:

• Selected three G. corneum populations along the northern Spanish coastline, representing a west-east summer temperature gradient.
• Monitored the vegetative propagation process from fragment reattachment to new individual development.
• Assessed phenotypic differences and growth capacity in natural habitats and under translocation.

Main Results:

• Phenotypic differences were observed in G. corneum development stages.
• Populations adapted to warmer conditions demonstrated superior growth capacity in both native and colder environments.
• Shoot elongation varied across populations, with the eastern (colder) site showing greater elongation (0.47 ± 0.01 cm) compared to western (0.24 ± 0.01 cm) and central (0.51 ± 0.02 cm) sites.

Conclusions:

• Local adaptation influences G. corneum's thermal tolerance and resilience.
• Evidence of phenotypic plasticity in vegetative propagation was found across G. corneum populations.
• The warm-adapted population presents a promising strategy for the persistence of G. corneum in changing marine environments.