Growth-dependent phenotypic variation of molluscan shells: implications for allometric data interpretation

Area of Science:

• Ecology
• Evolutionary Biology
• Developmental Biology

Background:

• Developmental plasticity is increasingly recognized as a key factor in organismal adaptation.
• Studies suggest a link between shell shape and growth rates in intertidal gastropods.
• Understanding these relationships is crucial for predicting species responses to environmental changes.

Purpose of the Study:

• To investigate how hypothetical growth processes contribute to developmental plasticity in molluscs.
• To model the relationship between shell growth rates and allometric curves in gastropods.
• To explore the influence of environmental factors and population origins on shell morphology.

Main Methods:

• Development of a growth vector model to simulate shell growth processes.
• Parameterization of the model using data from transplant experiments of three gastropod ecomorphs.
• Analysis of static and ontogenetic allometry to compare allometric slopes.

Main Results:

• Variation in instantaneous shell growth rate can induce variability in allometric curves, making morphological variation time-dependent.
• The model successfully reproduced key variations in size, shape, and growth rates observed in transplanted gastropod populations.
• A flatter growth profile was shown to correlate with rapid growth conditions, aligning with empirical findings.
• Model analysis revealed that "main effects" on morphology could be attributed to either the source population or the environment, depending on the dataset used.

Conclusions:

• The dynamics of development at the phenotypic level are essential for understanding phenotypic variation.
• Shell shape in gastropods is demonstrably dependent on growth rates, though comprehensive studies on allometry are scarce.
• The growth vector model provides a valuable framework for studying developmental plasticity and its impact on gastropod shell morphology.