Functional Reproductive and Developmental Traits Differences Between Two Macrocystis Ecomorphs: Importance of Neutral...

Area of Science:

• Marine Biology
• Ecology
• Genetics

Background:

• The kelp genus Macrocystis has populations with distinct morphological traits, leading to taxonomic discussions.
• Genetic evidence confirms Macrocystis integrifolia and Macrocystis pyrifera as distinct ecomorphs with separate distributions in the Southern Hemisphere.
• Despite interfertility in labs, over 20 years of study reveal differences in reproductive strategies and early development.

Purpose of the Study:

• To evaluate neutral lipid content in Macrocystis zoospores as an indicator of energy for swimming and settlement.
• To correlate lipid content with zoospore motility and germination capacity.
• To further investigate differential reproductive traits between Macrocystis ecomorphs.

Main Methods:

• Analysis of neutral lipid content in zoospores of Macrocystis integrifolia and Macrocystis pyrifera.
• Assessment of zoospore motility and germination rates.
• Comparison of zoospore production, reproductive success, and juvenile sporophyte development.

Main Results:

• Macrocystis integrifolia zoospores have significantly lower neutral lipid levels than southern Macrocystis pyrifera zoospores.
• Lower lipid content in Macrocystis integrifolia correlates with reduced cell motility and germination capacity.
• Macrocystis pyrifera demonstrates higher zoospore production, germination rates, reproductive success, and juvenile sporophyte growth and survival.

Conclusions:

• Macrocystis integrifolia and Macrocystis pyrifera exhibit consistent differences in reproductive functional traits, alongside genetic and morphological distinctions.
• These differential traits support the hypothesis of ongoing speciation between the two Macrocystis ecomorphs.
• The findings highlight the importance of ecophysiological traits in understanding kelp evolution and diversification.