FINE-GRAINED SPATIAL AND TEMPORAL VARIATION IN SELECTION DOES NOT MAINTAIN GENETIC VARIATION IN ERIGERON ANNUUS

Area of Science:

• Ecology
• Evolutionary Biology
• Plant Science

Background:

• Plant interactions are spatially local, influencing evolutionary dynamics through environmental heterogeneity.
• Limited knowledge exists on spatial fitness variation and the relative impact of spatial versus temporal selection variation.

Purpose of the Study:

• To investigate the spatial patterns of fitness variation in Erigeron annuus.
• To determine the relative magnitudes of spatial and temporal variation in selection.
• To explore the evolutionary consequences of this variation on genetic diversity.

Main Methods:

• 12 genotypes of Erigeron annuus were planted across 288 locations over two years.
• Relative fitness was measured, and spatial variation was analyzed at scales from 0.1 to 30.0 m.
• Genotype-environment interactions and the influence of soil nutrients, vegetation, and microtopography were assessed.

Main Results:

• Most spatial fitness variation (genotype-environment interactions) occurred over distances of 50 cm.
• Yearly effects on fitness were as significant as spatial variation, with a strong three-way interaction at the smallest scale.
• The genetic correlation of fitness across years was near zero, indicating unpredictable relative fitness.
• Soil nutrients explained most spatial variation, but likely served as indicators for unknown factors.
• Simulations showed the spatial scale was too fine to maintain genetic variation; inclusion of temporal variation reduced genotype coexistence.

Conclusions:

• Spatial and temporal variation in selection, particularly at fine scales, do not necessarily maintain genetic diversity.
• The observed pattern favors generalist genotypes over specialists.
• Understanding the scale and nature of selection is crucial for predicting evolutionary trajectories.