Developmental Changes in Time and Space Promote Evolutionary Diversification of Flowers: A Case Study in Dipsacoideae

Area of Science:

• Evolutionary developmental biology
• Plant morphology
• Floral evolution

Background:

• Flower shape and function diversify due to high plasticity in flower meristems.
• Small changes in timing and space profoundly impact adult structure formation.
• Dipsacoideae offers a robust model for studying floral development due to its phylogenetic framework and perianth diversity.

Purpose of the Study:

• Investigate floral organ initiation sequences in Dipsacoideae.
• Quantify interactions between flower meristem expansion and petal primordium size.
• Understand the role of temporal and spatial changes in floral evolution.

Main Methods:

• Comparative analysis of floral organ initiation across eight Dipsacoideae species.
• Quantitative assessment of meristem size and petal primordium size.
• Phylogenetic framework utilization for evolutionary interpretation.

Main Results:

• Flower meristem plasticity regulates pentamery via petal size or meristem expansion.
• Temporal shifts in organ initiation correlate with perianth morphological diversity.
• Sepal reduction is linked to delayed sepal initiation; sepal multiplication correlates with extended initiation time.

Conclusions:

• Timing and spatial interactions are crucial for evolutionary flower diversification.
• Heterochronies in early development can be modulated by later growth rate changes.
• Temporal shifts in organ initiation are a key driver of morphological diversity in floral perianths.