Genetic divergence predicts reproductive isolation in damselflies

Area of Science:

• Evolutionary Biology
• Genetics
• Zoology

Background:

• Reproductive isolation defines biological species.
• A predicted positive correlation between reproductive isolation and genetic divergence is often untested.
• Odonates (dragonflies and damselflies) exhibit strong sexual selection.

Purpose of the Study:

• To test the correlation between reproductive isolation and genetic divergence in damselflies.
• To estimate genetic thresholds for hybrid formation and test them in wild populations.

Main Methods:

• Measured reproductive isolation and genetic divergence in 30 damselfly species pairs across eight genera.
• Estimated genetic thresholds using mitochondrial (cytochrome oxidase II) and nuclear (18S-28S) genes.
• Empirically tested thresholds using wild Ischnura damselfly populations.

Main Results:

• A strong positive correlation was found between reproductive isolation and genetic distance (COII: r=0.781; 18S-28S: r=0.658).
• Hybridization thresholds were estimated for COII (-0.43 to 1.78%) and 18S-28S (-0.052 to 0.71%).
• F1 hybrids and backcrosses were detected in wild Ischnura species with overlapping genetic thresholds.

Conclusions:

• Positive isolation-divergence relationships are widespread across taxa.
• Genetic thresholds can identify species susceptible to hybridization.
• Findings support the link between genetic divergence and speciation in damselflies.