Semipermeable species boundaries create opportunities for gene flow and adaptive potential

Area of Science:

• Evolutionary Biology
• Ecology
• Genetics

Background:

• Hybridization and gene flow have complex effects on natural populations.
• Understanding natural hybridization in non-model organisms is crucial for assessing adaptive and deleterious outcomes in changing environments.
• The extent of hybridization and genomic differentiation in sympatric wood ant species (Formica rufa group) in Finland was previously unknown.

Purpose of the Study:

• To characterize the structure and extent of natural hybrid zones in five keystone mound-building wood ant species in Finland.
• To investigate the genomic differentiation and hybridization patterns within the Formica rufa group.
• To explore the ecological implications of hybridization, particularly in relation to microhabitat preferences and climate change.

Main Methods:

• Genome-wide data analysis to assess genetic variation and hybridization.
• Morphological data collection to complement genomic findings.
• Field observations to determine microhabitat preferences of different populations.

Main Results:

• More extensive hybridization than previously detected among all five Formica rufa group species in Finland.
• Identification of a mosaic hybrid zone between Formica aquilonia, F. rufa, and F. polyctena, including later-generation hybrids.
• Distinct gene pools were found for F. rufa, F. aquilonia, F. lugubris, and F. pratensis.
• Hybrids were observed in warmer microhabitats compared to cold-adapted F. aquilonia populations.

Conclusions:

• Extensive hybridization can generate adaptive potential, potentially enhancing wood ant resilience to climate change.
• Mosaic hybrid zones have significant ecological and evolutionary consequences, with unique hybrid populations facing distinct selection pressures.
• Climate change, particularly warmer winters and springs, may favor hybrids over cold-adapted species like F. aquilonia.