Interspecific pairing between two siblingIps species (Coleoptera: Scolytidae).

Area of Science:

• Ecology
• Evolutionary Biology
• Entomology

Background:

• Reproductive isolation mechanisms are crucial for maintaining species boundaries.
• Bark beetles (Ips spp.) infesting different pine hosts provide a model system to study these mechanisms.

Purpose of the Study:

• To investigate host and conspecific discrimination as reproductive isolating barriers between Ips paraconfusus and Ips confusus.
• To determine the extent of potential hybridization and gene flow in sympatric populations.

Main Methods:

• Field and laboratory experiments were conducted using Ips paraconfusus and Ips confusus males and females.
• Pheromone production was induced in host (Pinus coulteri, Pinus monophylla) and nonhost logs.
• Female beetle responses to conspecific and heterospecific males in different host trees were observed.

Main Results:

• Ips paraconfusus females joined both conspecific and heterospecific males in both pine species.
• Ips confusus females joined conspecific males in pinyon pine but failed to join Ips paraconfusus males in Coulter pine.
• Males did not displace heterospecific males from nuptial chambers; females readily accepted heterospecific males and oviposited in nonhost trees.

Conclusions:

• Host and conspecific discrimination offer partial reproductive isolation between these sibling Ips species.
• Limited reproductive isolation suggests potential for hybridization and interspecific gene flow in areas of sympatry.