Genitalic analysis of males and females in the Enchenopa binotata (say) complex (Membracidae: Homoptera)

9 Pages·1993·3.4 MB·

by  G Pratt

PROC. ENTOMOL. SOC. WASH.
95(4), 1993, pp. 574-582
GENITALIC ANALYSIS OF MALES AND FEMALES IN THE
ENCHENOPA BINOTATA (SAY) COMPLEX
(MEMBRACIDAE: HOMOPTERA)
Gordon Pratt and Thomas K. Wood
Department of Entomology and Applied Ecology, University of Delaware, Newark,
Delaware 19717.
Abstract.—Mdi\Q and female genitalia of nine species (8 undescribed, 1 of uncertain
identity) ofthe Enchenopa binotata complex were compared to Campylenchia latipesand
Enchenopaignidorsumtodetectdiagnosticcharactersforidentification. Discretecharacter
differences in male genitalia ofthe E. binotata complex were noted from Campylenchia
latipes and Enchenopa ignidorsum, but not between members of the complex. These
results demonstrate that genitalia are remarkably uniform and provide no practical di-
agnostic information within the E. binotata complex, other than slight size differences
apparently related to overall body size. The lack ofmorphological differentiation ofthe
members ofthe E. binotata complex is discussed in the context ofspeciation models.
Key Words: Host race, sympatric speciation, Campylenchia
The Enchenopa binotata (Say) complex charactersintheCicadellidae(Young 1957,
ofunivoltine North American treehoppers, DelongandFreytag 1967, Delong 1967)and
consists ofan array ofnine biological spe- to some extent in the closely related Mem-
cies (8 undescribed, 1 ofuncertain identity) bracidae (Broomfield 1976). In general,
associated with eight genera and nine spe- morphological differences in male genitalia
ciesofdeciduousplants(Wood 1980, Wood of Membracidae have also been useful in
in press, Wood and Guttman 1981, 1982, delimitinggenera (Caldwell 1949, Koppand
1983, 1985, Pratt and Wood 1992). These Yonke 1979) or complexes ofspecies (Die-
species, in addition to host origin, can be trich and Deitz 1991, McKamey and Deitz
distinguishedbydifferencesinallozymefre- 1991). These suggested genitalic characters
quencies (Guttman et al. 1981, 1989, Gutt- could be useful to either delimit each pre-
man and Weigt 1989, Pratt, Wood, and sumptiveEnchenopabinotataspeciesinthe
Datz in prep.), nymphal characters (Pratt complex or subdivide the complex into an
andWood 1992), andadult femalepronotal array which would facilitate identification
shape and size (Wood and Datz in prep.). and formal description.
Although pronotal shape and size differ
Methods and Materials
among females ofthe various species, these
characters are continuous and not discrete. At least six males and five females from
The apparent lack ofexternal discrete adult each ofthe following host plants ofthe En-
characters makes the species difficult to chenopa binotata complex were examined:
identify and formally describe. Ptelea trifoliata (Linnaeus), Juglans nigra
Differences in male genitalia have been (Linnaeus), Juglans cinerea (Linnaeus),
successful in providing diagnostic species Cercis canadensis (Linnaeus), Celastrus
VOLUME 95, NUMBER 4 575
scandens (Linnaeus), Liriodendron tulipi- Orleans, Maryland (Celastrus) and Nichols
fera (Linnaeus), Robinia pseudoacacia Lin- Arboretum, Ann Arbor, Michigan (Ptelea).
naeus, Caryaovalis(Wang)Sargent, and Vi- To examine intraspecific variation, ae-
burnum lentago Linnaeus. Two individuals deagi were dissected as above from fourad-
ofeach sex also were examined ofEnchen- ditional specimens ofa host associated spe-
opa ignidorsum Walker (Le Selva, Costa cies (host Cercis) (Fig. 5): A) Wilmington.
Rica) and Campylenchia latipes (Say) (Wil- Clinton Co., Ohio (DRD 34); B) Junction
mington, Clinton Co., Ohio and Little Or- ofroutes 46 and 59, Indiana (MRD 10); C)
leans, Maryland). [Campylenchialatipeswas Saint Louis, Missouri; and D) Elletsville,
comparedtothemembersoftheE. binotata Indiana (DRD 37). The specimen from 3B
complex, sinceitbelongstoacloselyrelated was redrawn as Fig. 5E. Voucher specimens
genus and was used as an outgroup in two from this study will be deposited in the En-
phylogenetic analyses ofthe complex (Pratt tomology Museum at the Smithsonian In-
and Wood, 1992).] stitute.
The abdomen from each individual was
removed and cleared in 10% NaOH over- Results
night at room temperature. The genitalia Subtledifferencesintheshapeofthemale
were removed and washed in 70% ethanol, genitalic structuresamongthe speciesofthe
and stored in glycerin. One ofeach species E. binotata complex (Figs. 1-3) were due to
wasdissectedwith sharptweezersbypulling individual variation and not species differ-
the styles and aedeagi away from the mem- ences. Other than slight differences in size
branous connective tissue. The male geni- of genitalic structures, we were unable to
talia and dissected parts were affixed with detect any discrete morphological differ-
petroleum jelly within glycerin to the bot- ences in either sex among any of the nine
tom ofa petri dish and drawn to scale using biological species of the E. binotata com-
acamera lucida mounted on a Leica Wild^ plex. Although the subgenital plate of the
MIO Stereoscopic microscope (Figs. 1-5). species with host Cercis (Fig. 1B) is slightly
Genitalia drawn intact were maintained narrower than the others, this character is
as such for future reference. Their localities not discrete, since it will not distinguish it
byhost(Fig. 1)areasfollows: A)Lycombine from the species with hosts Viburnum (Fig.
Co., Pennsylvania (code MBL-9) {Robinia)\ IE) and Celastrus (Fig. IF). The genitalia
B)Greyson, Kentucky{Cercis)\ C) Wooster, are remarkable in their uniformity.
Ohio (Juglans nigra); D) Wilmington, Clin- Sizedifferences in the subgenital plates of
ton Co., Ohio (Ptelea): E) Winchester, Vir- themaleareprobablyrelatedtooverallbody
ginia (Viburnum): F) 3 miles south ofKen- size. The E. binotata that use the hosts Lir-
net Square, Pennsylvania (Celastrus); G) iodendron and Carya, and Campylenchia
Ithaca, Oswega Co., New York (Juglans ci- latipes are generally the largest, whereas the
nerea): H) Newark, Newcastle Co., Dela- E. binotatathatusethehosts Viburnumand
ware (Liriodendron); and I) Wilmington, Ptelea, and Enchenopa ignidorsum are the
Clinton Co., Ohio (Carya). The localities of smallest of the species compared (Figs. 1,
dissectedspecimens(Figs. 2, 3)arethesame 4).
as above except: A) Harrisburg, Pennsyl- Although the styles of the E. binotata
vania (Robinia); B) Wilmington, Clinton complex do not seem to differ from one
Co., Ohio (2-MC-35) (Cercis); C) Newark, another (Fig. 2), the anterior arms of the
Newcastle Co., Delaware (Juglans nigra); aedeagi do appear to differ (Fig. 3A-I). The
and F) Harrisburg, Pennsylvania (Celas- member ofthe E. binotata complex which
trus). Additional specimens were examined appears to differ most in shape of the ae-
from the above localities and from Little deagus, is the species which uses Cercis as
PROCEEDINGS OFTHE ENTOMOLOGICALSOCIETY OFWASHINGTON
576
Fig. 1. Malegenitalia ofspecies ofthe Enchenopa binotatacomplex, which are designated bytheirhostA)
Robinia, B) Cercis, C)Juglansnigra, D)Ptelea, E) Viburnum, F)Celastrus, G)Juglanscinerea, H)Liriodendron,
and I) Carya (all to same scale; the length ofthe bar is 1 mm). The structures are as follows: sg = subgenital
plate, a = aedeagus, s = style.
VOLUME NUMBER
95, 4
577
B
h
JdeJs^ig'natedlb^y't^h'e'i'r^'h'o^s"t^Af)y>R^o^bionfia".lalBe)gCeenriatsal,iaC)ofJusgplecainessnoifgrat,heDE)ncPtheelneoapaE)biVnoWtuatrancuorm^plhecxehwshincmh ac^r\e
Juglansanerea, H) Liriodendron. and I) Carya(all to same scafe; the length ofthe baris 1 mm)
578 PROCEEDINGS OFTHE ENTOMOLOGICALSOCIETY OFWASHINGTON
B
H
Fig. 3. The dissected aedeagi ofmale genitalia ofspecies ofthe Enchenopa binotata complex, which are
designated by their host A) Rohinia, B) Cercis. C) Juglans nigra, D) Ptelea, E) Viburnum, F) Celastrus, G)
Juglanscinerea, H)Liriodendron, and I) CaryaandJ) Campylenchialatipes, andK)Enchenopaignidorsum(all
to same scale; the length ofthe baris 1 mm).
a host; so five individuals of this species genitalia of Campylenchia latipes and En-
wereexaminedtoidentifyintraspecificvari- chenopaspecieswerenotfoundtodiffer[see
ation (Fig. 5). The anteriorarms ofthis spe- Dennis(1952), Fig. 2 forgeneralized female
ciesseem tovaryasgreatlyasdothespecies genitalia]. These observations between
ofthe E. binotata complex. Campylenchia latipes and the Enchenopa
The male genitalia of Campylenchia la- binotata complex have been noted previ-
tipesandEnchenopaignidorsumdifferfrom ously (Dennis 1952).
the E. binotata complex in subtle but dis-
Discussion
crete characters. These include the shapes
ofthe posterior arm ofthe aedeagi and of Thelackofdiagnosticgenitaliccharacters
the styles (Figs. 2, 3, 4). In Campylenchia provides no basis for identification or sub-
latipes the posterior arm of the style was division of the species complex. Although
bent, whereas all Enchenopa were not. In the members of the E. binotata complex
Enchenopa ignidorsumthe anteriorarms of seem to differ in the shape of the anterior
the styles were reduced compared to the arms ofthe aedeagi, these differences are as
otherspecies. On the otherhand the female great intraspecifically as interspecifically
VOLUME 95. NUMBER 4 579
Fig. 4. MalegenitaliaofA) Campylenchialatlpes. B)EnchenopabinotatahostRohinia(from Figs. 1A, 2A),
and C) Enchenopa ignidorsum (all to same scale; the length ofthe bar is 1 mm).
580 PROCEEDINGSOFTHE ENTOMOLOGICALSOCIETY OFWASHINGTON
B
Fig. 5. Thedissectedaedeagiof5 E. binotata(hostCercis),(alltosamescale; thelengthofthebaris 1 mm).
(Figs. 3, 5). Dennis (1960) has also noted evidence that the members ofthis complex
similar variation in the anterior arm ofan- may have been geographically isolated fol-
othertreehopperspecies. Heexaminedover lowed by secondary contact causing selec-
1000 male genitalia and found the anterior tion for genitalic differences as an interspe-
arm varies greatly, while the posterior arm cific reproductive isolating mechanism
exhibits little variation. (Shapiroand Porter 1989). Eberhard (1992)
Eventhough Campylenchialatipesis tax- suggests that sexual selection may play an
onomically more distant to the E. binotata important role in speciation with some in-
complex than is Enchenopa ignidorsum, it sects. The absence of genitalic differentia-
seems as similar in male genitalia to the E. tion within this species complex suggests
binotata complex as is E. ignidorsum. The that selection on these characters has not
C
only two characters which separate la- been intense. If sexual selection has pro-
tipes from the E. binotata complex are the moted divergence in this complex, it has
bent styles (Fig. 4) and the broad posterior acted on other structures such as the pro-
arm of the aedeagus (Fig. 3). Enchenopa notum.
ignidorsumdiffersfromboth Campylenchia Becausethegenitaliaofthevariousmem-
latipes and the members ofthe E. binotata bers of the E. binotata complex differ in-
complex (Fig. 4) by the shortened anterior terspecificallyonlyinsize(duetobodysize),
arms of the styles, the compressed ninth there are probably no mechanical impedi-
segment, and the long single segmented ments to hybridization among the species
subgenital plates (the others are composed associated with the different hosts—except
oftwo separate segments). perhapsthoseduetosize. Speciationinthese
Negative results in general are not re- treehoppers has been hypothesized to have
ported, but they are of value with the E. occurred through shifts in host plant usage
binotata complex. Clear genitalic differ- (Wood 1980, Wood and Guttman 1981,
ences in this complex could be viewed as 1982, 1983, 1985). In this hypothesis the
VOLUME 95, NUMBER 4 581
primary mode ofreproductive isolation in graphic genetic variation in the Enchenopa bino-
the complex is due to host-induced asyn- tatacomplex(Homoptera:Membracidae).Annals
oftheEntomologicalSocietyofAmerica82: 156-
chronous mating or diurnal mating prefer-
ences (Wood in press, Wood and Keese Guttm16a5n., S. I., T. Wilson, and L. A. Weigt. 1989.
Wood Wood
1990, et al. 1990, et al. in Microgeographic genetic variation in the Enche-
prep.). The lack of genitalic differences in nopa binotata complex (Homoptera: Membraci-
the E. binotata complex does not support dae). Annals of the Entomological Society of
America 82: 225-231.
alternative models.
Guttman, S. I., T. K. Wood, and A. A. Karlin. 1981.
Genetic differentiation along host plant lines in
Acknowledgments
the sympatric Enchenopa binotata Say complex
We appreciate the support of the Com- (Homoptera: Membracidae). Evolution 35: 205-
USDA 217.
petitive Grants Program. This is Kopp, D. D. and T. R. Yonke. 1979. A taxonomic
miscellaneous paper number 1479 of the review ofthe tribe Ceresini (Homoptera: Mem-
Delaware Agricultural Experiment Station, bracidae). Miscellaneous Publications, Entomo-
and contribution number 650 of the De- logical Society ofAmerica 112: 1-97.
partment ofEntomology and Applied Ecol- McKamey, S. H. and L. L. Deitz. 1991. Revision of
ogy, and number 178 of the Life Science the Neotropical treehopper genus Metcalfiella
(Homoptera: Membracidae). North Carolina Ag-
Ecology program at the University ofDel- riculturalResearchServiceTechnical Bulletin 294:
aware, Newark, DE. 1-89.
Pratt,G.andT.K.Wood. 1992. Aphylogeneticanal-
Literature Cited ysis ofthe Enchenopa binotata species complex
(Homoptera: Membracidae) usingnymphal char-
Broomfield,P.S. 1976. Arevisionofthegenus -J/»a5- acters. Systematic Entomology 17: 351-357.
tris (Homoptera: Membracidae). Bulletin of the Shapiro, A. M. and A. H. Porter. 1989. The lock-
British Museum (Nat. Hist.), Entomol. 33: 347- and-key hypothesis: Evolutionary and biosyste-
460. matic interpretation of insect genitalia. Annual
Caldwell, J. S. 1949. A generic revision ofthe tree- Review ofEntomology 34: 231-245.
hoppersofthe tribeCeresini in America north of Wood,T.K. 1980. IntraspecificdivergenceiniT^c/j^-
Mexico, based on a study ofthe male genitalia. nopabinotataSay(Homoptera: Membracidae)ef-
Proceedings of the United States National Mu- fectedbyhostplantadaptation. Evolution34: 147-
seum 98: 491-521.
Delong, D. M. 1967. A monographic study ofthe 160.
NorthAmericanspeciesofthegenusBallana(Ho- . In press. Speciation ofthe Enchenopa bin-
moptera: Cicadellidae). Ohio Journal ofScience otata complex (Insecla: Homoptera: Membraci-
64: 305-370. dae). Symposium ofthe Biological Linnean So-
Delong, D. M. and P. H. Freytag. 1967. Studies of ciety.
the world Gyponinae (Homoptera, Cicadellidae): Wood, T. K. and S. I. Guttman. 1981. The role of
AsynopsisofthegenusPonana. Contributionsto host plants in the speciation of treehoppers: An
the American Entomological Institute 1: 1-86. example from the Enchenopa binotata complex,
Dennis,C.J. 1952. Genitaliaofthe Membracidaeof pp. 39-54. In Denno, R. F. and H. Dingle, eds.,
Wisconsin. Canadian Entomologist 84: 157-173. Life History Patterns: Habitat and Geographic
. 1960. Thegenitaliaofthebuffalotreehopper Variation. Springer-Verlag, New York, Heidel-
Stictocephalahulbalus(Fabricius).AmericanMid- berg, Berlin.
land Naturalist 64: 459-473. . 1982. Ecologicalandbehavioralbasisforre-
Dietrich, C. H. and L. L. Deitz. 1991. Revision of productive isolation in the sympatric Enchenopa
the Neotropical tribe Aconophorini (Homoptera: binotata complex (Homoptera: Membracidae).
Membracidae). North Carolina Agricultural Re- Evolution 26: 233-242.
search Service Technical Bulletin 293: 1-134. . 1983. The Enchenopa binotata complex:
Eberhard,W.G. 1992. Speciesisolation,genital me- Sympatric speciation?Science 220: 310-312.
chanics,andtheevolutionofspecies-specificgen- . 1985. Anewmemberofthe^^c/z^rtopa^mo-
italia in three species of Macrodactylus beetles tata Say complex on tulip tree {Liriodendron tu-
(Coleoptera, Scarabeidae, Melonthinae). Evolu- lipifera).ProceedingsoftheEntomologicalSociety
tion 46: 1774-1783. ofWashington 87: 171-175.
Guttman, S. I. and L. A. Weigt. 1989. Macrogeo- Wood,T.K.andM.Keese. 1990. Hostplantinduced
PROCEEDINGS OFTHE ENTOMOLOGICALSOCIETY OF WASHINGTON
582
assortative mating in Enchenopa treehoppers. Young, D. A. 1957. The leafhopper tribe Alebrini
Evolution 44: 619-628. (Homoptera, Cicadellidae). Proceedings of the
Wood, T. K., K. L. Olmstead, S. I. Guttman. 1990. United States National Museum 107: 127-297.
Insectphenologymediatedbyhost-plantwaterre-
lations. Evolution 44: 629-636.