Temperature-mediated transitions between isometry and allometry in a colonial, modular invertebrate

Area of Science:

• * Evolutionary biology
• * Marine biology
• * Coral reef ecology

Background:

• * Animal body plans are constrained by allometry, impacting evolutionary success.
• * Colonial modular (CM) designs may offer a way to overcome these constraints through modular iteration.
• * CM designs are hypothesized to support isometry and indeterminate colony size.

Purpose of the Study:

• * To test the hypothesis that CM designs support isometry and indeterminate colony size.
• * To investigate the growth rates and scaling exponents of juvenile scleractinian corals with a CM design.
• * To determine if environmental factors, specifically temperature, influence growth scaling in CM taxa.

Main Methods:

• * Annual measurements of colony diameters for juvenile scleractinians (less than 40mm) over a decade.
• * Calculation of scaling exponents (b) for growth using double logarithmic plots of final versus initial diameters.
• * Statistical analysis correlating growth scaling exponents with annual seawater temperature variations.

Main Results:

• * Growth scaling exponents (b) varied significantly among study years, with isometry observed in 4 years and positive allometry in 5 years.
• * Seawater temperature was significantly associated with growth scaling, with isometry occurring in warm years and positive allometry in cool years.
• * Coral growth was not size-constrained, with both isometry and positive allometry contributing to this outcome.

Conclusions:

• * Colonial modular taxa exhibit variable growth scaling, with temperature mediating the switch between isometric and allometric growth.
• * Positive allometry under cooler conditions provides a size-dependent growth advantage.
• * CM designs can facilitate growth that is not limited by size, adapting to environmental fluctuations.