Character displacement and coexistence in mud snails (Hydrobiidae)

Area of Science:

• Ecology
• Evolutionary Biology
• Malacology

Background:

• Hydrobiid snail species (Hydrobia ulvae, H. neglecta, H. ventrosa, and Potamopyrgus jenkinsi) were studied in 90 localities.
• Coexistence dynamics and allopatric distributions of these species were examined.

Purpose of the Study:

• To investigate character displacement in hydrobiid snails, focusing on body size differences.
• To understand the role of food particle size selectivity in species coexistence.
• To explore the influence of genetic isolation on the degree of character displacement.
• To estimate the timescale of microevolutionary changes in response to environmental shifts.

Main Methods:

• Field surveys across 90 localities in three distinct areas.
• Comparative analysis of body size in coexisting and allopatric snail populations.
• Assessment of reproductive periods in different population structures.
• Evaluation of food particle size selection and competitive interactions.

Main Results:

• Character displacement observed in coexisting Hydrobia ventrosa and H. ulvae, with size ratios (1.3-1.5) facilitating coexistence via food selectivity.
• Variation in character displacement correlates with genetic isolation levels.
• Coexisting H. ventrosa and H. ulvae exhibit shorter, more defined reproductive periods.
• Potamopyrgus jenkinsi shows distinct food selection, suggesting weak competition with Hydrobia spp. and no character displacement.

Conclusions:

• Food particle size selectivity is a key factor enabling stable coexistence through character displacement in hydrobiid snails.
• Genetic isolation influences the extent of microevolutionary adaptations.
• Environmental changes, such as the recent marine history of the Limfjord, provide insights into the tempo of evolutionary change.