Hippodamia convergens Guerin-Meneville was selected for
rapid development through five generations at four constant
temperatures (18, 22, 26, and 30��C). Two levels of selection
were used: intense and moderate. Differences in developmental
rate, survivorship, live adult weight, aphid consumption,
adult longevity, and fecundity were measured for both groups
and an unselected line.
The two selected lines exhibited significant differences
in developmental rate after the first generation of selection.
The differences increased by the fifth generation of
selection. Average differences between selected lines at 18,
22, 26, and 30��C in development from egg to adult were 4.9,
3.0, 1.0, and 1.5 days, respectively. Individuals from the
intense selected line had a lower developmental threshold
(11.3��C) than the moderate selected line (12.0��C). Also,
degree-day requirements from egg to adult were lower in the
intense (266 DD��) than moderate (277 DD��) line. Wild type
beetles accumulated 231 degree-days above a threshold of
13.6��C.
Survivorship at cold temperatures significantly increased
with selection for fast development. In addition, no
significant differences occurred in either live adult weight,
total larval consumption of prey, fecundity, or adult
longevity. Larvae selected for fast growth consumed higher
numbers of aphids per day and were more efficient
metabolically in converting prey mass into body mass than slow
growing larvae.
Because of a lower developmental threshold and lower
degree-day requirements, for complete development, beetles
from the intense selected line may accumulate more degree-days
throughout a year compared to a moderate selected line.
Predictions of population growth, based on an equation for
intrinsic growth rate, showed that beetles from the intense
selected line would produce 1.6 and 1.4 times more individuals
in a 60-day period than beetles from the moderate selected and
unselected lines, respectively. The results suggest that
intense selected beetles would develop faster earlier in the
season and would produce higher population numbers under
optimum conditions. Thus, selection of H. convergens produced
superior beetles for future introductions in biological
control. / Graduation date: 1995
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35295 |
| Date | 09 June 1994 |
| Creators | Rodriguez-Saona, Cesar Ramiro |
| Contributors | Miller, Jeffrey C. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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