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ABSTRACT Choosing where offspring will develop is especially important for insects whose larval stages are restricted to a particular host resource. In such insects, maternal egg laying decisions may not only involve choosing optimal hosts based on their intrinsic qualities but also avoiding hosts occupied by conspeciHc brood. The ability to discriminate between previously exploited and unexploited hosts is often mediated by the use of a marking pheromone. Despite engaging in what appears to be host-marking behavior, the walnut fly Rhagoletis juglandis prefers to deposit clutches into previously exploited hosts. In this dissertation, I quantiHed host reuse in R. juglandis and assessed its impacts on offspring fitness. I also explored the role that marking pheromone plays in level of reuse. Host reuse by the walnut fly was conunon in the field, where trees were synchronously infested over a 14 -17 day period. It was not unusual for individual fruit to bear 40 - 80 eggs; given that females laid clutches of ca. 16 eggs, each oviposition puncture probably contained ca. 1.6 clutches. The overall number of eggs deposited into fruit was positively correlated with fruit volume. Field and laboratory experiments showed that increases in larval densities within fruit reduced larval survival and pupal weight, the latter being strongly correlated with the number of eggs a female produced over her lifetime. The temporal staggering of clutches strongly and negatively impacted survival of later clutches. The effect of spatial patterning of clutches on offspring ntness depended on the number of clutches in the &uit: at higher densities, clutches 7
perfonned better when deposited into the same puncture than when distributed uniformly over fruit. The evidence taken together suggests that host reuse by the walnut fly, R. juglandis, reduces per capita offspring fitness. Consistent with this inference was a final set of observations on female host-marking behavior. In field-cage experiments, fruit that were marked by females for longer durations were less acceptable to other females. Moreover, the duration of time that a female marked a fruit was positively correlated with the size of her clutch. These results indicate that, while females commonly reuse fruit, they nevertheless signal the level of larval competition associated with a fhiit and adjust allocation of eggs to fruit accordingly. 8
Page 1: INFORMATION TO USERS This manuscrip
Page 4 and 5: UMI Number: 3053915 Copyright 2002
Page 6 and 7: STATEMENT BY AUTHOR This dissertati
Page 8 and 9: DEDICATION This work is dedicated t
Page 12 and 13: An explanation of tiie problem CHAP
Page 14 and 15: euse occurs in the field, the impac
Page 16 and 17: Appendix D, "Aggregative behavior i
Page 18 and 19: offspring performance. Counter to t
Page 20 and 21: Lalonde RG, Mangel M, 1994. Seasona
Page 22 and 23: APPENDIX A HOST MARKING BEHAVIOR IN
Page 24 and 25: kluwer the language of science Dr.
Page 26 and 27: 174 belter categorized as cues than
Page 28 and 29: fubfe 2. Kinds ot cvicknce used lo
Page 30 and 31: 278 defend themselves and because i
Page 32 and 33: 280 lion of a signal. Costs associa
Page 34 and 35: 282 than were conspccifics with low
Page 36 and 37: 284 thai (he marker was a mutant fo
Page 38 and 39: 286 dropping on ihe MP communicatio
Page 40 and 41: 28S inac>. 3 larval partsiloiil of
Page 42 and 43: 290 Hol'svang. T. 1988. Mechanisms
Page 44 and 45: 29Z Roitbcfg. B- D it R- G- Laionde
Page 46 and 47: APPENDIX B HOST UTILIZATION BY THE
Page 48 and 49: Dispersal by Larvae of the Stem Bor
Page 50 and 51: POPULATION ECOUXTY Host Utilization
Page 52 and 53: October 2000 NUFIO ET AL.; HOST UTI
Page 54 and 55: October 2000 Nufio et au: Hoct Unuz
Page 56 and 57: October 2000 NUFIO ET AL4 HOST UIHI
Page 58 and 59: Reuse of larval hosts by the walnut
Page 60 and 61:
KEYWORDS Life history" marking pher
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Alternatively, a weak correlation b
Page 64 and 65:
previously attacked hosts early in
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walnut fly oviposition punctures. T
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Effects of offspring weight on adul
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she deposited over a lifetime and t
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RESULTS Levels of host reuse in the
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Survival from egg to egg hatch Of t
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significantly correlated with pupal
Page 78 and 79:
DISCUSSION While the femaie-prefere
Page 80 and 81:
discriminate between hosts that hav
Page 82 and 83:
will consume fewer resources and th
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females gain not by simply reusing
Page 86 and 87:
of her offspring but also of the nu
Page 88 and 89:
ACKNOWLEDGEMENTS We thank Henar Alo
Page 90 and 91:
Bjorkman C, Larsson S, Bommarco R,
Page 92 and 93:
Fujiyama N, Katakura H, 2001. Varia
Page 94 and 95:
Mayhew PJ, 1997. Adaptive patterns
Page 96 and 97:
Robertson IC, Roitberg BD, 1998. Du
Page 98 and 99:
Wiklund C, 1981. Generalist vs. spe
Page 100 and 101:
Table 2. The influence of various f
Page 102 and 103:
Table 4. Analysis of variance compa
Page 104 and 105:
nCURE CAPTIONS - Continued Figure 5
Page 106 and 107:
Figure 1. Fruit Cohorts (Number of
Page 108 and 109:
Figure 3. A. B. A > on •m e « 50
Page 110 and 111:
Figure 5. B. es & 1 1 0.8 • 0.6 -
Page 112 and 113:
Figure 7. B. > 09 "S s e s o •Ml
Page 114 and 115:
Figure 9. 400 9t W s 1 t 300 « Of)
Page 116 and 117:
Aggregative behavior is not explain
Page 118 and 119:
that the larval aggregations that f
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2001). The shifting benefits and co
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spatial patterning of clutches depo
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16-fl oz (473-ml) plastic Solo cups
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percentage of hatchlings that emerg
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previously created oviposition punc
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RESULTS Experiment 1. Effect of off
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deposited) again improved the model
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median pupal weight in the lone two
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survival, using two-clutch and thre
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DISCUSSION Absence of an AUee efTec
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simultaneously. It would seem that
Page 142 and 143:
Spatial distribution of clutches In
Page 144 and 145:
If reuse of larval hosts negatively
Page 146 and 147:
Page 148 and 149:
Hausmann SM, Miller JR, 1989. Ovipo
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Papaj DR, Alonso-Pimentel H, 1997.
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
FIGURE CAPTIONS continued Figure 4.
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Figure 2 MD E DC n Om 3 Qi S V DA E
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Figure 4. B. c. -g 60 S a. a 40 - S
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Host marking beiiavior as a quantit
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encountered either control fruit th
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unparasitized and parasitized hosts
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Finally, it is conceivable that the
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Experiment 1. Relationship between
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or 30 minutes). Fruit were then hun
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After two replicates of the four tr
Page 176 and 177:
Experiment 3. Female responses to h
Page 178 and 179:
RESULTS Experiment 1. Effects of cl
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Experiment 3. Female responses to f
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example, the possibility that ovipo
Page 184 and 185:
field cage assays. What remains to
Page 186 and 187:
Page 188 and 189:
Bauer G, 1986. Life-history strateg
Page 190 and 191:
Landolt PJ, Averill AL, 1999. Fruit
Page 192 and 193:
Quiring DT, McNeil JN, 1984. Intras
Page 194 and 195:
FIGURE CAPTIONS Figure 1. The relat
Page 196 and 197:
Figure 2. w OA 8 k 98 s o a. QH s 8
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