MOLECULAR EVOLUTIONARY DIVERGENCE AMONG NORTH AMERICAN CAVE CRICKETS. I. ALLOZYME VARIATION

Area of Science:

• Evolutionary Biology
• Population Genetics
• Speciation

Background:

• Cave crickets (genera Euhadenoecus and Hadenoecus) present unique evolutionary case studies due to their specialized habitats.
• Understanding genetic variation is crucial for deciphering speciation processes and population dynamics in isolated environments.

Purpose of the Study:

• To investigate genetic variation and gene flow among nine North American cave cricket species.
• To compare genetic differentiation between cave-dwelling and epigean (noncave) species.
• To correlate genetic patterns with ecological factors like habitat structure and geographic isolation.

Main Methods:

• Electrophoretic analysis of genetic variation at 41 loci across 49 populations.
• Estimation of gene flow (Nm) and genetic differentiation (FST, Nei's D).
• Phylogenetic analyses using UPGMA, Wagner algorithms, and correspondence analysis.

Main Results:

• Cave species show significantly lower gene exchange and higher genetic differentiation than epigean species.
• Genetic differentiation in cave crickets correlates with limestone distribution and habitat fragmentation.
• Phylogenetic analyses yielded broadly concordant but not identical branching patterns across different methods.

Conclusions:

• Habitat structure, particularly limestone continuity, plays a significant role in shaping genetic differentiation in cave cricket populations.
• Epigean dispersal is negligible for cave-dwelling species, with historical gene flow patterns dominating current genetic structure.
• Genetic data offer insights into evolutionary relationships, though they show some discordance with morphological phylogenies.