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An explanation of tiie problem CHAPTER 1 INTRODUCTION The decisions that insects make about where their offspring will develop are especially important for species with larval stages that are restricted to a particular environment or host (Thompson 1983, Smith and Lessells 1985, Bemays and Chapman 1994, Mayhew 1997). Because insect larvae that develop within discrete hosts (e.g. flower buds, seeds, small ftoiit, stems, or other insects) may not be able to acquire more resources if their natal hosts become depleted, larval development can be affected very strongly by level of competition for food resources. Researchers have often proposed that in such insects, females should be under strong selection to choose hosts that are optimal for larval development (Jaenike 1978, Thompson 1988, Mayhew 1997). These optimal egg laying decisions may not only involve choosing optimal hosts based on their intrinsic qualities but also by avoiding hosts previously occupied by conspecific brood. It is particularly important that females avoid previously exploited hosts because brood competition can reduce offspring fitness by increasing the time required for offspring to reach maturity, as well as by reducing brood survival, size and reproductive potential (rev. Peters and Barbosa 1977, Fox et al. 1996, Blanckenhom 1998, Sweeney and Quiring 1998, Allen 2001). This ability for insects to discriminate between previously exploited and unexploited hosts is often mediated by the presence of a 9
Marking Pheromone (MP), which is placed on the host surface following oviposition by previous females (Roitberg and Prokopy 1987, Nufio and Papaj 2001). Frugivorous fruit flies in the family Tephritidae deposit clutches into developing fruit, where larvae are constrained to feed and develop. These fruit flies are also thought to possess visual and chemical mechanisms for assessing the quality of available hosts and for discriminating between previously infested and uninfested hosts (Prokopy et al. 1976, Prokopy and Roitberg 1984, Henneman and Papaj 1999). In the genus Rhagoletis, for example, females often assess and reject infested fruit on the basis of a MP (Landolt and Averill 1999). MPs in these systems have been shown to minimize larval competition by causing females to distribute their clutches more uniformly within host patches then expected by chance alone (Prokopy 1981, Bauer 1986, Averill and Prokopy 1989). Walnut flies in the Rhagoletis suavis group reuse their hosts, a behavior that is uncommon among other flies in the genus. While reuse of hosts that already bear conspecific brood is conunonly associated with the lack of available hosts (Roitberg and Mangel 1983, Papaj et al. 1989), walnut flies actually prefer to oviposit into infested hosts early in the season when uninfested hosts are still available (Lalonde and Mangel 1994, per. obs.). After deposition of a clutch, females drag their ovipositors on the firuit surface in a manner known to involve deposition of a MP in congeners. Yet despite displaying this genus-typical marking behavior, female walnut flies re-infest and often reuse the actual oviposition sites established by conspecifics (Papaj 1993, 1994). This dissertation examines the dynamics of host fruit utilization by the walnut fly R. juglandis. In particular, the following studies examine the context in which host 10
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 10 and 11: ABSTRACT Choosing where offspring w
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
Page 62 and 63:
Alternatively, a weak correlation b
Page 64 and 65:
previously attacked hosts early in
Page 66 and 67:
walnut fly oviposition punctures. T
Page 68 and 69:
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
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DISCUSSION While the femaie-prefere
Page 80 and 81:
discriminate between hosts that hav
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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
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Table 2. The influence of various f
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Table 4. Analysis of variance compa
Page 104 and 105:
nCURE CAPTIONS - Continued Figure 5
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Figure 1. Fruit Cohorts (Number of
Page 108 and 109:
Figure 3. A. B. A > on •m e « 50
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Figure 5. B. es & 1 1 0.8 • 0.6 -
Page 112 and 113:
Figure 7. B. > 09 "S s e s o •Ml
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Figure 9. 400 9t W s 1 t 300 « Of)
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Aggregative behavior is not explain
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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
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Spatial distribution of clutches In
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If reuse of larval hosts negatively
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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
Page 170 and 171:
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
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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
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field cage assays. What remains to
Page 186 and 187:
Page 188 and 189:
Bauer G, 1986. Life-history strateg
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Landolt PJ, Averill AL, 1999. Fruit
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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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