Vol. 10 No. 1-2 2003 (2005) SCRIBER and MARGRAF: Florida Persea and Papilio palamedes 49 HOLARCTIC LEPIDOPTERA, 10(1-2): 49-51 (2005) SillTABILITY OF FLORIDA RED BAY AND SILK BAY FOR PAPILID PALAMEDES BUTTERFLY LARVAE (LEPIDOPTERA: PAPILIONIDAE) J. MARK SCRIBER AND NICOLAS MARGRAFl Dept.ofEntomology, Michigan State University, East Lansing, Michigan 48824, USA ABSTRACT.-TheLauraceae·specialistswallowtail butterfly,PapiliopalamedesDrury,has neverbeenreported usingaprominenttreespecies likesilk bay(Persea borboniavar.humilis,Lauraceae)incentralFlorida.Thistreegrowsinthecentralwhite,arid,sandyhabitatsanditsdensehairy/pubescentleavesdistinguishit from theglabroushammock-dwellingredbay(Perseaborboniavar.borbonia)andthewetland/swamp-dwellingswampbay(Perseapaluslris).Weexaminedthesuitability of these two plant species for larval survival and growth using split-brood bioassays. No significant differences in survival, pupal weight, overall duration of development orgrowth rates wereobserved. Whatever preventssilkbayfrom beingusedas anatural hostfortheP. palamedes butterfly is notknown. KEYWORDS: arid sand habitats, defenses, ecological monophagy, habitats, hostplants, Lauraceae, Magnoliaceae, Nearctic, North America, USA, wetlands. In southern Florida, the Lauraceae-feeding swallowtail butter plants are common in the scrubs of the Ocala National Forest, in flies, Papilio palamedes Drury and Papilio troilus Linnaeus north-central Florida. Silk bay, now treated as a variety of bay (P. (Papilionidae) are basically confined to red bay (Persea borbonia borbonia) (Wunderlin, 1998), has been viewed previously as a (L.) Spreng. var. borbonia) in the hammocks and swamp bay separate species (P. humilis) (see Nelson, 1994). We decided to (Persea palustris (Ref.) Sarg.) in swamps and wetland habitats examine the leavesofsilk bay (P. borbonia var. humilis) relative to where they occur (Scriber et aI., 1998; M. Minno, pers. comm.). red bay (P. borbonia var. borbonia) to see if the distinctive Further northward in the eastern United States, sassafras (Sassafras morphological differencesofsilkbay leaves(densely pubescentand albidiwn(Nutt.)Nees) and spicebush(Linclera benzoin(L.) Blume) silky on underside; Nelson, 1994)made them differentially suitable (both Lauraceae) can serve as host plants for P. troilus and P. forswallowtailbutterflysurvivalandgrowth.Suchthickpubescence palamedes, although the ability to usethese northern hosts is poorer might be a significant defensive adaptation against potential forthe allopatric P. palamedes thanthesympatric P. troilus (Leder herbivores such as P. palamedes or primarilyjust an adaptation for houseetaI., ]992).Thesetwo swallowtail species are notknown to leaf water conservation in their hot, arid habitats compared to the utilize sassafras or spicebush in Florida (M. Minno, pers. comm.). coolerand wetbayheadsand hammockswherePerseaborboniaand Even within a single species, it was observed that survival and P. palustris (and Magnolia virginiana) exist. Our test was a growth of Florida P. troilus populations on red bay were signifi bioassay ofneonate larval survival and growth on the two varieties cantly greater than Michigan and Ohio populations on this plant ofred bay. (NitaoetaI., 1991).Papilio troilusalso frequently utilizetheexotic but naturalized camphor tree (Camphora sp.). METHODS Numerousliteraturerecordsincorrectlylistsweetbay(Magnolia virginianaL.) (Magnoliaceae), orjust "bay" (which common name Adult females of P. palamedes from Highlands and Levy can refer to a variety of plants), as putative hosts for P. palamedes Counties, Florida, were collected in late March to early April 1999 and P. troilus (Scriber, 1984). Howeverlarval survivalin no-choice and set up in revolving multi-choice oviposition arenas in front of bioassaysisnon-existentandovipositionmistakesontotheMagnoli incandescentlightbulbs (on and offat 2hr intervals) to obtaineggs aceae plantspeciesare minimal (Scriber, 1986;Scriberetal., 1991; (Scriber, 1993;ScriberetaI., 2001). Neonate larvaeoftwo families Scriber et aI., 2001). (F37 and F44) were divided equally between two hostspecies to be It has been shown thatneoliginins from the leaves ofMagnolia bioassayed. Groups of 3-8 larvae were carefully placed into petri virginiana (sweet bay) are toxic to the Magnoliaceae-unadapted P. dishes (2.5cm x l5cm) with leaves on a sprig ofeither red bay or troilus andP. palamedes(NitaoetaI., 1992), whilechemicalsinred silkbayinsertedinfloral aquapics tomaintain leafwaterandturgor. bayaretoxicto the generalistPapilioglaucus larvae(Scriber, 1986) All dishes were maintained at room temperature in the air condi and deterrent to the P. glaucus ovipositing females (Frankfater and tioned, invertebrate laboratory of the Archbold Biological Station Scriber, 1999a; Frankfater and Scriber, 2003). In contrast, phyto near Lake Placid, Florida. The final few days of the feeding were chemicals in red bay are attractive for both P. troilus and P. in ourlabatMichiganStateUniversity using Persea leaves brought palamedes. backon icein zip-lock bags. Each larva was transferred to its own The existence of a different shrubby lauraceous "bay" species individual dish when it reached the pupal stage. Survival on each (silk bay, Persea borbonia var. humilis (Nash) L. E. Kopp) in the host was assessed at one to two day intervals as host leaves were desert-like white sand scrub of central Florida (Wunderlin, 1998) changed and dishes cleaned. Total durations to pupation were raisedthequestionofsuitabilityfortheLauraceae-adaptedP. troilus recorded for survivors. Pupal weights were recorded using a and P. palamedes. No host records for either Papilio species exist Semi-Macro analytical balance. A follow-up study was conducted for silk bay, and these two swallowtail species are rarely even seen at the Archbold Biological Station (28 Mar-2 Apr 2000) with P. in such white sand scrub habitat (such as found at the Archbold palamedesandP. troilus females collected from LevyCounty, west Biological Station in Highlands County, Florida). However, these ofAlachua Co., Florida. Data are presented as a mean ± se. Significant differences are 'Current address: Institute of Zoology, University of Neuchatel, CH-2007 indicated (p = 0.05). Plant voucher specimens of both Lauraceae Neuchatel, Switzerland. 50 SCRIBER and MARGRAF: Florida Persea and Papilio palamedes HOLARCTIC LEPIDOPTERA Table 1.Larvalgrowth performanceoftwo Floridafamilies ofPapiliopa/amedeson two redbay (Persea borbonia) varieties (Lauraceae). Data presented as a mean (±s.e.) (Highlands Co., FL). number Pupal mass TotalDuration Overal1Growth Rate Host plant ofpupae (g) (d) (g/d) var. humilis 10 1.37 29.5 .047 (silkbay) ±.04 ± 0.5 ±.OOI var. borbonia 12 1.46 30.1 .049 (redbay) ±.06 ±l.l ±.001 T-test* (n.s.) (n.s.) (n.s.) p=.226 P=.664 P=.389 * No significant differences between means on different plants (n.s.; p= 0.23, 0.66, 0.39 respectively t-tests on pupal mass, total durations and growth rate. species have been deposited in the herbarium research collectionof leaves of Lauraceae host species (Scriber, 1996a). Preliminary JMS at Michigan State University. results from 2000 suggest that this may at least partically explain the lack ofany field host records ofeggs or larvae on silk bay. RESULTS The chemical suitability of tree leaves for larval survival and growth is a function of leaf water, nitrogen, allelochemicals, Contrary to our predictions, the overall survival of neonate minerals, and their interactions (Scriber, 1977, 1984; Mattson and larvae to pre-pupae in 1999 was basically the same for larvae of Scriber, 1987). The physical texture, toughness, hairiness, spines, Papi/io pa/amedes on red bay, Persea borbonia var. borbonia andtrichomes arealso offundamental importanceforthe hostplant (70.6%) as on the silk bay, Persea borbonia var. humi/is (61.1%) suitability (Scriber and Slansky, 1981; Finke and Scriber, 1988). (Fig. 1). Furthermore, the final pupal weights, total durations and Despite the fundamental chemicalconstraints upon theevolutionof overall growth rates (neonate to pupa) were also virtually identical hostplantpreferencesandusage patterns(Feeny, 1995), otherbiotic between split broods (on different Persea species) of two families factors such as natural enemies (Bernays and Graham, 1988; of P. pa/amedes larvae (Table 1). However, in 2000, females of Scriber, 1998; Redman and Scriber, 2000) and abiotic factors such both P. pa/amedes and P. troUus showed strong oviposition as seasonal thermal unit (growing degree day) constraints (Scriber preference for red bay versus silk bay. All P. pa/amedes (n = 4) and Lederhouse, 1992; Scriber, 1996b; Nylin and Janz, 1999) can preferred red bay (163 total eggs) versus silk bay (15 total eggs). affect local host specificity. While we don't know why silk bay is Furthermore, neonate larvae grew poorly on silk bay (only one of apparently not used as a host for either P. troi/us or P. pa/amedes 28 survived the 1st instar) and grew well on red bay (35 of 37 butterflies, wedo know that for thelatteritis notdueto physiologi survived the 1st instar). cal unsuitability for larvae. DISCUSSION ACKNOWLEDGMENTS The extensive and dense hairiness on leaves of the silk bay This research was supported in part by the Michigan State University (Persea borboniavarhumi/is)andtheirdesert-likewhitesandshrub Agricultural ExperimentStation (ProjectMAES#1644). Weareextremely thankful for the permission to use the Archbold Biological Station and habitats of central contrast rather dramatically with the smooth, HighlandsHammockStateParkfacilitiesduringourstudies.Special thanks more glabrous leaves of upland red bay (Persea borbonia var. are extended to Mark Deyrup and Jennifer Donovan for their assistance. borbonia)and swamp bay(Perseapalustris) whicharefound in the Mark Minna, Gainesville, Florida, provided a very helpful review and wettestswamps,forests, andhammocksthroughoutFlorida(Preston, insightintothetaxonomicconfusionregardingthethreebayspecies(Persea 1976; Nelson, 1994). The Lauraceae-specialized swallowtail sp.) in Florida. butterflies, Papilio pa/amedes and P. troi/us, have been reported repeatedly on red bay and swamp bay but, to ourknowledge, never REFERENCES onsilkbay. Ourbioassay results from larvalfeedingstudies withP. pa/amedes, suggest that habitat preferences or oviposition prefer Bernays, E.,and 1\1. 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