GENETIC DIVERSITY IN OVERWINTERED AND NON-OVERWINTERED IPS-PINI (SAY)(COLEOPTERA, SCOLYTIDAE) IN IDAHO

The pine engraver, Ips pini (Say), has two generations per year in pon derosa pine (Pinus ponderosa Lawson) in Idaho, one that develops in pi ne slash in the spring and one that develops in live trees in the summ er. The summer generation overwinters to produce the spring generation the following year. Non-overwintered and overwintered beetles were sa mpled from two sites. Average heterozygosity was significantly higher in overwintered beetles in both groups. While the proportion of homozy gous individuals did not differ significantly between overwintered and non-overwintered beetles from either site, the proportion of heterozy gous individuals was significantly greater after overwintering in beet les from one of the two sites. The increase in genetic diversity after overwintering is consistent with observations that heterozygosity is favored by severe environmental conditions.