Ancient ﾑ antsymbiosis: direct evidence from Dominican amber

P りめ E devr 己三 du 此 刀MS

SUMMARY

Although symbioticassociation with ants is pervasive in the butterfly families Lycaenidae and the age of these symbioses has never been estimated explicitly. Here we report the first known fossil ri0.dinidcaterpillar. This fossil can be dated minimally between 15 and 20 Ma old, and confidently placed in the extant Theope.Differing little from modern day Theope, this fossil from Dominican amber provides direct evidence that secretory and acoustical organs used by modern caterpillars to mediate symbioses with ants have been highly developed at least since the Miocene. This fossil therefore becomes the point of reference for future studies using molecular clock methods for dating these symbioses within the riodinid . Modern evidence, and the abundance of dolichoderine ants in Dominican amber (now extinct in the West Indies) imply that specialized symbioticrelationships between Theope cater- pillars and these ants were likely in existence at least 15 Ma ag0. The current distribution of neotropical riodinid butterfly and ant faunas indicates the extinction in the West Indies of at least two unrelated taxa that formed a tightly linked symbiotic association, which persisted to the present elsewhere

1. INTRODUCTION communicationand recruitment (Marki & Holldobler 1978;Baroni-Urbani et a1. 1988; Roces et a1. 1995). It has Among butterflies the ability to form intimate associaﾂ recently been established that the ability to produce tions with ants has evolved only in the lycaenoidsﾑ the families Lycaenidae and Riodinidae (Cottrell 1984; substrate-borne acoustical calls is a widespread trait Pierce 1987; DeVries 1991a,1997; Fiedler 1991).The among lycaenid and riodinid caterpillars that form symbioses with ants (DeVries, 1990, 199k), and that fundamentalnature of these symbiotic associations is these calls bear similarities to ant vibrational signals that caterpillars provide ants with food secretions in exchange for protection against predators (Cottrel1 (DeVrieset a1.1993; DeVries, unpublished data). Thus, 1ycaenidand riodinid caterpillar calls are considered 1984;Pierce 1987; Pierce et a1. 1987; DeVries 1988,1997; to function in concert with secretory organs to achieve DeVries & Baker 1989).Experimental studies on both and maintain ant symbionts (DeVries1990, 199k, 1997; groups have demonstrated that when they are found by predators and parasitoids, caterpillars DeVries et a1. 1993). Although the mechanisms for cater ﾂ pillar call production in all lycaenids and members of without ant symbionts have little chance of surviva1, the riodinid tribe Eurybiini remain unknown, it has whereas caterpillars with ant symbionts are provided been demonstrated that riodinid caterpillars in the

significant protection against these natural enemies tribes Lemoniini and produce calls by (e.g. Pierce & Mead 1981;Pierce et a1. 1987; DeVries using paired organs, termed vibratory papillae 1991&;Cushman et a1. 1994). By virtue of the strong (DeVries1990, 1991c, 1997). influence on caterpillar fitness the maintenance of a Despite the prevalence of riodinid caterpillars in constant guard of ants is at a premium, and this is the tribes Eurybiini, Lemoniini and Nymphidiini to achieved through the use of specialized secretory form intimate associationswith ants (Harvey 1987; organs that not only produce food secretions to ants, DeVries 1997;DeVries et a1. 1994), the age of these but may also produce semiochemicalsthat modify ant behaviours (Cottrell 1984;DeVries 1988, 199k, 1997; symbioticinteractions is unknown. The origin of ri0- Fiedler & Suefert 1996). dinid-ant associations could potentially be estimated indirectly using molecular clock methods with a phy- Vibrational communication is prevalent among ants 1ogenetichypothesis (Kimura 1983;Li & Graur 1991), (Holldobler & Wilson 1990),and studies suggest that 0r directly through the fossil record. However, the these signals are used by some ants as part of colony age never ofmolecular this phenomenon has been estimated by ck 日 山Od S and no P @ en 卜 ev denceexis *Author for correspondence,

Proc. R. Soc. Lond. B (1997) 264, 1137-1140 1137 ｩ 1997 The Royal Society Printed in Great Britain 1138 P.J. DeVries and G. 0. Poinar Ancientbutterfly-ant symbiosis

Dominican amber fossils have been extremely im ﾂ report thereforeprovides the first direct evidence that portant to our understanding of insect evolution and secretory and acoustical organs used by riodinid butter ﾂ biogeography (e.g. Baroni-Urbani 1980; Wilson fly caterpillars to mediate symbioses with ants were 1985a,&;Poinar 1992,1996; Grimaldi 1991,1996a), but highly developed at least 15ﾑ 20 Ma ag0, and serves to fossil inclusions of butterflies in Dominican amber are constrain future studies that approximate the age of exceedingly rare. Three adult butterflies of the same riodinid-ant symbioses using a molecular clock. species are known from Dominican amber, all of which There are currently about 50 species in the genus possess systematic affinities with the mainland neotr0- Theope,with members occurring in lowland forests pical genus Mipaea, but not to the only extant West throughout Mexic0, Central and South America, and Indian riodinid,Dianesia carteri (Harvey 1987; Grima1- on (Seitz 1916-1920;Barcant di 1996a;DeVries 1997).As neither present day Napaea 1970;Harvey 1987; Bridges 1988), but they are absent caterpillars and its relatives, or caterpillars of Dianesia from the West Indies. The contemporary West Indian and its close relatives possess specialized organs to form riodinid fauna consists of a single species, Dianesia car- associationswith ants (see summaries in Harvey 1987; ten, and this taxon is confined entirely to Cuba and the DeVries 1997), riodinid-ant symbioses are unknown Bahamas (Spencer-Smith et a1. 1994). The fossil Theope from the West Indies. Here we report the first fossil rio ﾂ reported here, together with the other Dominican am- dinid caterpillar in Dominican amber that not only ber fossil riodinid species (see Grimaldi 1996fl;DeVries provides the first accurate benchmarkfor dating the 1997), therefore establishes the extinction of at least two antiquity of riodinid ﾑ ant symbioses, but it contributes riodinid taxa from the West Indies. further evidence for the historical extinction of major Two points suggest that the palaeoriodinid fauna of groups of fauna in the Dominican Republic. the West Indies included more than two taxa. First, it is likely that the composition of the Domincan palae0- entomofauna was similar to the composition ofentom0- 2. RESULTS AND DISCUSSION faunas found presentlyin Central and South America The unique amber piece containing the riodinid ca ﾂ (Baroni-Urbani & Saunders 1980; Wilson 1985a,A). terpillar originated from the Lalbca group of mines in Analyses of 11 contemporary Central and South the northern mountain ranges of the Dominican Re ﾂ American riodinid faunas indicate that approximately public located in the El Mamey Formation (Upper 30% of the total species richness at each site is ac ﾂ Eocene), which is composed of shale-sandstone inter ﾂ counted for by taxa that form symbioses with ants spersed with a conglomerateof wel1-roundedpebbles (see DeVries 1997). Based on these estimates the Domin ﾂ (Eberle et a1. 1980). Recent biostratigraphicand pa- ican palae0-riodinid fauna would be predicted to 1aeostratigraphic evidence indicates that all include a minimum of three to four species. Second, Dominican amber was formed in a single sedimentary the palae0-entomofauna in Dominican amber remains basin dated from 15ﾑ 20 Ma old (Iturralde-Vincent & largely unstudied, and future work will undoubtedly MacPhee1996), whereas previous chemical and fossil increase the number of taxa above what is currently evidence has suggested an age of 30-40 million years known(Poinar 1992, unpublished data), including rare old (Schlee 1990). taxa like riodinid butterflies. Therefore both compara- The combined presence of tentacle nectary organs, tive estimates based on present day faunas, and the vibratory papillae, and bal100n setae are found only on quantity of Dominican amber material yet to be exam- riodinid caterpillars in the tribe Nymphidiini, and no ﾂ mned，， uggeSt 、 ， I。ぬ ， P 、 l" 。 0- ， I"dinid 伍una than where else among the (Gottrell 1984; 。， l"M ， 卜 d by b ， 刊 。 Vid 。 nCe Harvey 1987; DeVries 1997).Thus, the possession of all A wide range of fossil evidence indicates that ancient three of these specialized organs by this fossil (figure 1) symbioticassociations have been remarkably persistent place it unquestionably as a riodinid caterpillar that through evolutionary time (reviewedin Boucot 1990; formed symbioses with ants. Possessionof exaggerated Poinar 1992).For example, Wasmann(1932) described bal100n setae along the anterior margin of the first a reduviid bug with its Dolichoderus ant prey from Baltic thoracicsegment is typical of caterpillars in the genus amber, and noted that it differed little from modern Theope,although less exaggerated bal100n setae are day ancestors who remain apparent specialists on these found in the close relative Nymphidwm (Harvey 1987; same ants. Other examples are found in Dominican DeVries 1997).Present day Theope caterpillars possess amber (Poinar 1992), and one of the most spectacular strongly developed ventr0-1ateralflanges on all body is an alate Acropyga. ant queen carrying a symbiotic scale segments, long plumose lateral body setae, and absence insect in her mandibles (Grimaldi 1996&).Excepting of anterior tentacle organs, traits that are not shared by the single record of Theope guillaumei being tended by Nymphidiumcaterpillars (Penz & DeVries,unpublished Solenopsisants (while feeding on the Azteca-mhabhed data). A detailed comparison on contemporary cater ﾂ ant-plant Cecropid), all other observations indicate that pillars of four species of Theope (T. matuta, T. guillaumei, present day Theope caterpillars typically form obligate T. virgilius, T lycaenma),and four Nymphidium species (AC symbioses with dolichoderine ants, especially the gen ﾂ mantus, M. balbinus, .AC nr baeotia,.AC cachrus}, not only era Azteca and Dolichoderus (DeVries et a1. 1994; DeVries showedthat the fossil may be confidently placed in the 1997,unpublished data). In these obligate symbioses the genus Theope (probably in the fourth, and penultimate exaggerated bal100n setae surrounding the head of instar), but that it falls within the overall variation ob ﾂ Theopecaterpillars (figure 1) appear important in med ﾂ served among different species of present day Theope iating associations with dolichoderine ants by providing caterpillars (see illustrations in DeVries (1997)).This semiochemicalstimuli to ant symbionts (DeVries1997).

片DC ・ A ・ 比L ム On止 B 口 997 AnCtgntLばば g竹 ― め而ソ川析oSL P・ J ・ DevrieSand C ・ O・ P 山nar l139

てなサ

tn Ap

L

Vn

Figure 1. Fossil Theopecaterpillar in Dominican amber, (a) Photographof the fossil in dorsal view. (A) Illustration of the entire fossil in dorsal view showing features characteristic ofriodinid caterpillars that form symbioses with ants: conspicuouscorona of bal100n setae on thoracic segment one, the wel1-developed anal plate (Ap) on abdominalsegments nine and ten, and the external orifices of the tentacle nectary organs (tno) on abdominal segment eight, (c) Illustration of head and first thoracic segment detailing the placement of vibratory papillae (Vp) on anterior edge ofthoracic segment one. The vibratory papillae function in the production of substrate borne acoustical signals that enhancemodern riodinid caterpillar-ant symbioses.

Proc. R. Soc. Land. B (1997) 1140 P.J. DcVries and G. 0. Poinar Ancientbutterfly-ant symbiosis

The abundance of A^teca and Dolichoderus ants in Do ﾂ DeVries, P. J., Thomas, J. A., & Cocroft, R. 1993 Comparison minican amber (Wilson ¥985a,b) suggests that a of acoustical signals in Mawlineabutterfly caterpillars and specialized relationship between Theope and these doli- their obligate host Myrmica ants. Bio1.J. Linn. Soc. 49, 229ﾑ 238. choderine ants is likely to have existed at least 15-20 DeVries, P. J., Murray, D. & Chacon, 1. A. 1994 Toward a ag0. as case Ma Moreover, is the for Theope butterflies, better understandingof host plant use and biodiversity in neither Azteca or Dolichoderus are part of the living Do ﾂ riodinid butterflies (Lepidoptera). J. Res. Lep. 31, 103-126. minican Republic ant fauna, but these ant genera form Eberle, W., Hirdes, W., Muff, R. & Pelaez, M. 1980 The principal elements of mainland neotropical foresthabi- geology of the Cordillera Septentriona1. Proc. 9th Caribbean tats (Wilson 1985a;Holldobler & Wilson 1990).Thus, Geolog.Congr. 1980, 619-632. 0ur report not only provides evidence for the extinction Fiedler, K. 1991 Systematic, evolutionary, and ecological implications of myrmecophily within the Lycaenidae of Theope from the Dominican Republic, but points to (Insecta: Lepidoptera: ). Banner ^oologische the possible correlated extinctions of two unrelated spe ﾂ Monographien31, 1-210. cies that acquired, and maintained a tightly linked Fiedler, K., & Suefert, P. 1996 Butterflies and ants: the symbiotic association that has survived to the present communicativedomain. Experientia 52, 14ﾑ 24. in Central and South America. Grimaldi, D. A. 1991 Mycetobiine woodgnats (Diptera Anisopodidae) from the Olig0-Miocene amber of the

DOminiCa" Pub 肚 ， and 口 d 田 d a田 nities At。 Am. M四 WC are grateful to C. M. Penz for illustrating the fossi1, and Jrfovit.3014,1-24. comparingTheope and JVymphidiumcaterpillars. WL also thank Grimaldi, D. A. 1996a Amber: window to the past. New York J. King-Koyne, D. Drift, D. Grimaldi, R. Lande, M. Lynch, Abrams & American Museum of Natural History. C. M. Penz, T. Walla, and two anonymous reviewers for pro ﾂ Grimaldi, D. A. 1996A Captured in amber. Scient. Am. Apri1, viding valuable comments on the manuscript. The Dominican 7077. at amber fossil is in the Poinar amber collection Oregon State HarVey ， D・ J ・ l987 川 8 M妙ガ CM几妙 dFon ダぬク PioF ぬ ぬら University, Corvallis, Oregon. This research was funded in Lepidoptera. Ph.D. thesis. University of Texas, Austin part by aJ. S. GuggenheimFellowship to P. J. DeVries, and is Holldobler, B. & Wilson, E. 0. 1990 The ants. Cambridge dedicated to the acoustical research of the late T.Williams. Harvard University Press.

Iturralde ・ Vinent ， M・ A・ & MatPhee ， k ， D・ E ・ I996Ageand paleogeographic origin of Dominican amber. Science 273, REFERENCES 1850-1852

Barcant, M. 1970 The butterfliesof Trinidad and Tobag0. London: Kimura ， M・ @983 Thわ e n6utyol th80 リダ 川 oJ86uJ&r 川 OJu@ion Collins. Cambridge University Press

Baroni-Urbani, C. 1980 First description of fossil gardening む， ・ & G口 ur ， D・ l9gl Fuぴ n ぬ 川そ ntdJ 才 川加川 Mr 勿 ofufion ants. Stuttgarter Beit. Natukd. B 54, 113. Sunderland,MA: Sinauer Associates. Baroni-Urbani, C. & Saunders, J. B. 1980 The fauna of the Mark!, H. & Holldobler, B. 1978 Recruitment and food Dominican Republic amber: the present status of knowl ﾂ retrieving behavior in Nwomessor (Formicidae, edge. Mem. 9th Caribbean Geo1.Conf. 1980, 213-223. Hymenoptera).I1. Vibrational signals. Behav. Eco1.Sociobio1. Baroni-Urbani, C., Buser, M. V & Schillinger, E. 1988 4,183-216. Substrate vibration during recruitment in ant social organi ﾂ Pierce, N. E. 1987 The evolution and biogeography of associa ﾂ zation. Insect.Soc. 35, 241-250. tions between lycaenid butterflies and ants. Oxf. Surv. Evo1.

田 uCot ， A・ J ， 1990 巧 oM肋 M ソ伸肪 &fofo以ダ &タぬ Uior ば卍 Bio1.4, 89-116. coevoluhon. Amsterdam: Elsevier Science Pierce, N. E. & Mead, P. S. 1981Parasitoids as selective agents

Bridges ， C ・ A・ l988 ぬ 川叫ダ M8ni血 8 a FodinidQ6 in the symbiosis between butterfly larvae and ants. Science (Lepidoptera:Rhopalocera). Champagne-Urbana: printed by 211, 1185-1187. the author. Pierce, N. E., Kitching, R. L., Buckley, R. C.,Taylor, M. F.J. Cottrel1, C. B. 1984 Aphytophagy in butterflies: its relation- & Benbow, K. F. 1987 The costs and benefits of cooperation ship to myrmecophily.J^po1. J. Linn. Soc.79, 1 ﾑ 57. between the Australian lycaenid butterfly, Jalmenus evagoras,

CuShman ， J ， H ・， Rashb ， OOk， V K ・ & Be 祈 k ， A・ J ・ l994 and its attendant ants. Behav. Eco1.Sociobio1. 21, 237-248. Assessing benefits to both participants in a lycaenidant Poinar, G. 0. 1992 Life in amber. Stanford University Press. association. Ecology 75, 1031-1041. Poinar, G. 0. 1996 Fossil velvet worms in Baltic and DeVries, P. J. 1988 The larval organs of Thisbe irenea Domincan amber: Onychophoran evolution and bioge0- (Riodinidae) and their effects upon attending ants. ^po1.J. graphy. Science273, 1370-1371. Linn. Soc. 9, 379-393. Roces, F.,Tautz,J. & Holldobler, B. 1995 Stridulation in leaf- DeVries, P. J. 1990 Enhancement of symbioses between cutting ants. Natuwissenschaften80, 521-524. butterfly caterpillars and ants by vibrational communica ﾂ Schlee, D. 1990 Das Bernstein-Kabinett. Stuttgarter Bntrager tion. Science248, 1104-1106. Mt. Ser. C 28,1-100. DeVries, P. J. 199la Ecological and evolutionary patterns in Seitz, A. E. 1916-20 Erycinidae. In Macrolepidoptera of the riodinid butterflies. In Ant-plant interactions(ed. C. Huxley world, vo1. 5, pp. 617-738. Stuttgart: Alfred Kernan. & D. F. Cutler ), pp. 143-156. Oxford University Press. Spencer-Smith, D., Miller, L. D. & Miller, J. Y. 1994 The DeVries, P. J. 1991A The mutualism between Thisbe ireneaand 加地神仏 Of th6 WgJ6 fndwJ and JOuth FIorido. Oxnord ants, and the role of ant ecology in the evolution of larva- University Press.

1ant associations. BioL J. Linn. Soc. 43,179-195. WaSmann ， E ・ 1932 Eine a口口 Sen 山Ordcnde gastwan2e

DeVries, P. J. 1991c Call production by myrmecophilous ぽ叫MO クタ 川 doJo ぬタ n・ g。 n・ s.) i 血 baltiSChen bernStein ・

riodinid and lycaenid butterfly caterpillars (Lepidoptera): B荊 JfF4ein- 凡畑A ・ 3， l ― 3・

morphologica1, acoustica1, functiona1, and evolutionary WnSon ， E ・ O・ l985a Invasion and extinction in 山ee West patterns. Am. Mus. Novit. 3025,1-23. Indfanantfauna.S6ignce229,265-267.

DeVries, P. J. 1997 The butterfliesof Costa Rica and their natural WnSon ， E ・ O・ l985& Ants of lhe Dominican amber historyII: Riodinidae. Princeton University Press. (Hymenoptera: Formicidae). 1I1. The subfamily DeVries, P.J. & Baker, 1. 1989 Butterfly exploitation of a plan- Dolichoderinae. Psyche 92, 17-37. tant mutualism: adding insult to herbivory. 7. @@' Ent. Soc.

971332 ― 340 ・ Received23M ゆ l91997;勿 r坤比川 J 川口9 収

Proc. R. Soc. Land. B (1997)