The various taxa and hosts of the North American Celastrina (Lepidoptera: Lycaenidae)

13 Pages·1994·4.2 MB·

by  G F Pratt

;
PROC. ENTOMOL. SOC. WASH.
96(3), 1994, pp. 566-578
THE VARIOUS TAXA AND HOSTS OF THE NORTH AMERICAN
CELASTRINA (LEPIDOPTERA: LYCAENIDAE)
Gordon F. Pratt, David M. Wright, and Harry Pavulaan
(GFP)DepartmentofEntomology, UniversityofCalifornia, Riverside, California 9252
1
(DMW) Department ofPathology and Laboratory Medicine, University ofPennsylvania,
100 MedicalCampusDr., Lansdale, Pennsylvania 19446; (HP)494 FillmoreSt., Hemdon,
Virginia 22070.
Abstract.—T\\e genus Celastrina (Lepidoptera: Lycaenidae) includes Holarctic small
blue butterflies whose larvae feed on the flowers, fruits, leaves, and galls of a diverse
variety ofplants. In North America the Celastrina ladon species complex presently con-
tains three recognized species (ladon. neglectamajor, and nigra). The versatile Celastrina
ladon consists ofeight subspecies and several seasonal forms. Many ofthese forms are
biologically distinct allochronic races. The hosts and distributions ofthe species, subspe-
C
cies, and races ofthe ladon complex in North America are presented. In the West, the
Celastrina have segregated into seven subspecies, while in the East they have reached
greater evolutionary diversity and formed several species and several seasonal races. It
appears that host shifts, associated with changes in adult season or habitat preference,
may have played a major role in the historical evolution ofthe species and races ofthe
C
ladon complex.
Key Words: Host races, Lycaenopsis, distribution, asynchronous, evolution, phytoph-
agous, Polyommatini, sympatric speciation
Host plant adaptation is believed to have American species are currently recognized:
had a major role in the evolution of phy- Celastrina ladon (Cramer, Celastrina ne-
tophagousinsects(Walsh 864, Jermy 984, glectamajorOpler& Krizek, and Celastrina
1 1
Strong et al. 1984). Some insect host races nigra (Forbes) (= ebenina Clench) (see Cra-
feature differences in rates of adult matu- mer 1780, Forbes 1960, Clench 1972, Opler
ration, which resultinasynchronous mating and Krizek 1984, ScottandWright, inpress).
periods and genetic isolation (Wood and These taxa are considered bonafide species,
Guttman 1983, Bush 1969, PhiHips and since they exhibit discrete morphological
Barnes 1975, Knerer and Atwood 1973, andhostdifferencesin sympatry. Celastrina
Smith 1988). Such allochronic examples nigra larvae likewise feed exclusively on
may be incipient species. Seasonal isolation Aruncus dioicus (Wagner and Mellichamp
therefore may play as important a role as 1978); C. neglectamajor larvae feed exclu-
host differences in the evolution ofspecies sively on Cimicifuga racemosa (Edwards
in sympatry (Smith 1988, Wood and Keese 1878, 1883b); however C. ladon larvae feed
1990, Wood etal. 1990). on a wide variety of plants (56 species, 19
Celastrinaaresmallbluebutterflieswhose families) (Scott 1986).
C
larvae feed mainly on the flowering parts of Eight North American subspecies of
a broad variety of plants. Three North ladon are currently recognized: argentata
VOLUME 96. NUMBER 3 567
(Fletcher), cinerea (Edwards), echo (Ed- vae were collected by finding them in ant
wards),gozora (Boisduval), ladon(Cramer). attendance orbybeating specific plant parts
lucia (Kirby), nigrescens (Fletcher), and si- into a heavy cloth net. Discrimination of
dara (Clench) (Miller and Brown 1981). adult taxa was accomplished by a table of
Presently, only subspecies ladon and lucia morphological and biological characters
are recognized in eastern North America. (Table 1). The adult color patterns ofmany
These eastern subspecies have traditionally races are stable and consistent; their ranges
been separated into the following seasonal were delineated from data accumulated by
forms: "lucia" (Kirby) with a dark discal the examination of thousands of museum
patch on ventral hindwing (VHW), "mar- specimens and material contributed by col-
VHW
ginata" (Edwards) with a dark outer lectors. Distributions ofmonophagous spe-
margin, "lucimargina" (Scott) with a dark cies and races were further substantiated by
VHW
discal patch and margin, "violacea" comparison with their host's distributions.
(Edwards) with dusky gray ventral surface Hostdata aresummarized in theAppendix.
and prominent maculations (without dark-
ened disc or margin on VHW), and "neg- Results
lecta" (Edwards)with white ventral surface,
North American species
reduced maculations, and white insuffusion
into dorsal blue ground color. The spring The adult morphological characters and
forms ("lucia," "lucimargina." "margina- seasonal occurrences used to distinguish
ta," and "violacea") can be found together species of North American Celastrina are
which suggests that C. ladon is genetically listed in Table 1. Of the three Celastrina
variable. Some types of "violacea" and species recognized in North America, two
"neglecta" fly later in late springorsummer of these, C nigra and C neglectaniajor.
after the flights of the earlier spring forms share similar ranges with density centers in
have been completed. Since there is little the Ozarks in the Midwest and the central
seasonal overlap between the spring and and southern Appalachians in the East (Figs.
summer groups and in aggregate they are 1, 2). Celastrina neglectatuajorextends fur-
polyphagous, they have been considered ther north in the Appalachians and covers
seasonal forms of the same species (Ed- 34% more area than C. nigra. Both C. nigra
wards 1883b. Millerand Brown 1981.Opler and C. neglectaniajoraremonophagousand
and Krizek 1984, Scott 1986). their larval food plants are Aruncus dioicus
The distributions and hosts of North (Rosaceae) and Ciinicifiiga raceiiiosa (Ran-
American Celastrina (includingeastern rac- unculaceae) respectively. The distributions
es) are poorly known. Proper data are nec- ofthe food plants for C. neglectaniajorand
essarytounderstand Celastrinakinshipsand C. nigra are outlined around the ranges of
evolutionary histories. The purpose ofthis the corresponding butterflies (Figs. 1, 2).
paper is to present the hosts and distribu- Both butterflies occupy about 50% oftheir
tions of the species, subspecies, and races host's range.
of the C. ladon complex, to identify areas Celastrina nigra and C. neglectaniajor,
ofoverlap or sympatry between races, and unlike C. ladon. exhibit little geographic
to present diagnostic characters which dis- variability in wing pattern. Celastrina nigra
tinguish them. malesaredistinguishedfrom otherCelastri-
na by three morphological characters: pres-
Materials and Methods
ence of long overlapping scales (replacing
Hosts were identified by observations of androconia) on the dorsal wing surface, a
ovipositing females in the field and/or by dark dorsal brown to black coloration, and
rearing field collected larvae to adults. Lar- absence ofblue iridescent scales (Table 1).
\
568 PROCEEDINGS OFTHE ENTOMOLOGICALSOCIETY OF WASHINGTON
Table 1. Morphologicalcharacters which distinguish thedifferent Celastrina species, subspecies, and races.
VOLUME 96. NUMBER 3 569
FIG. 2
neglectamajor
host (Cimicifuga)
Fig. 1. Mapofeastern United States showingthegeographic rangeofCe/astnna nigra. Therangeofitshost
plantAnincusdioicus is lightly shaded around the range ofthe butterfly.
Fig. 2. Map ofeastern United States showing the geographic range ofCelaslnna negkxlamajor. The range
ofIts host plant Cimicifuga racemosa is lightly shaded around the range ofthe butterfly.
570 PROCEEDINGS OFTHE ENTOMOLOGICAL SOCIETY OF WASHINGTON
FIG. 3
Fig. 3. Map ofwestern North Amenca showing the geographic ranges ofthe different western subspecies
and ofthe midcontinent range ofeastern ssp. C. I. ladon. Fig. 3a (inset) Map ofMexico and Central America
showing range ofsubspeciesgozora.
speciesechooccursthroughout most ofCal- actersofpopulationsrangefromtypical echo
ifornia (and Baja California), Oregon, to typical nigrescens. Individuals of sub-
Washington, southern British Columbia, species nigrescensarequite variableand ex-
Idaho, and extends to western Montana, hibit the forms "lucia," "marginata" and
western Wyoming, northern Utah, and "violacea." Subspecies sidara occurs from
northern Nevada. Celastnna echo and C northern New Mexico through the western
I.
/. nigrescem exhibit a broad blend zone in two-thirds of Colorado, west to extreme
southern British Columbia, eastern Wash- northeastern Utah, and north through cen-
ington, northeastern Oregon, Idaho, west- tralandeasternWyomingtosouthern Mon-
em Montana, northern Utah, and western tana, the Black Hills ofSouth Dakota, and
Wyoming. In this blend zone, wing char- the Badlands in southwestern North Da-
VOLUME 96. NUMBER 3 571
Fig. 4. Map ofeastern North America showingthe geographic ranges oiCetaslnna I. lucia (including liicia
And. belowdottedline)andraces"violacea" I and"neglecta."4a(inset). MapofNorthAmericashowingentire
range ofC /. lucia. 4b (inset). Map ofeastern North Amenea separately showing range ofC /. ladon.
kota. Celasthna I. argentata is restricted to "bakeri" is the basal greenish tint on the
the plains in southern Manitoba and Sas- ventral wing surfaces. This character is also
katchewan. weakly expressed in even some southern
The only western taxon that is not allo- populations ofecho.
patric to the other subspecies is "bakeri" Subspecies lucia (Fig. 4a) occurs widely
(formallya subspecies). All known "bakeri" throughout the subarctic from Alaska to
records occur within the blend zone ofsub- Labrador then south to Alberta, Saskatch-
species echo and nigrescens. We consider ewan, Manitoba, southern Ontario, and
"bakeri" tobea formofechoand nigrescens Quebec. Traditional ssp. hicia Kirby is a
and follow Miller and Brown (1981) in this verysmallsingle-broodedbutterflywithvery
regard. Thedistinguishingcharacterofform lightbluedorsalcolortendingtowardgreen-
572 PROCEEDINGS OFTHE ENTOMOLOGICAL SOCIETY OF WASHINGTON
.^=^
lucia
lucIa Auct.
gall-feedergroup
"neglecta"
FIG. 5
Fig. 5. Mapofeastern NorthAmerica showinggeographic rangesofCelasirinaI. luciaand C. I. ladon races
"violacea" II, "violacea" III. and "neglecta."
ish-blue. Heavily marked forms "lucia," range (includingcentral Appalachian Mts.).
"marginata," and "violacea" are common- Previous authors have recognized the dif-
place. Further south in southern Ontario. ferencesbetween luciaKirbyandthesecond
Quebec, northcentral and northeastern group in northeastern United States and re-
United States (below dotted line in Fig. 4), ferred to the latter as ""lucia" of authors
lucia Kirby is replaced by larger, highly (Klots 1951, Forbes 1960). Confusion has
variable specimens ofa single early spring existed regarding their assignment to ssp.
brood. The dorsal colors ofthe lattergroup lucia or to ssp. ladon. Through morpholog-
are quite polymorphic. Forms "lucia," ical and biological characters we include
"marginata," and "violacea": occur, but them with ssp. lucia under the designation
"marginata" and "violacea" become more lucia Auctorum.
frequent near the southern extent of the The known host plants of the different
VOLUME 96, NUMBER 3 573
Celastrina are listed in the Appendix. Lar- vae have been field collected and allowed
vaeofthewestern subspeciesfeedonabroad to pupate, the pupae ofall three races enter
variety ofplant families: primarily Astera- obligate diapause (as do lucia, nigra, and
ceae, Ericaceae, Fabaceae, Polygonaceae, neglectamajor). In contrast, mature larvae
Rhamnaceae, Rosaceae, and Saxifragaceae. ofthesympatric"neglecta" populationsfol-
The hosts ofargentata. gozora, and nigres- lowing pupation eclose as adults in 8-12
cens are not known. Celastrina I. liicia is days.
recorded on Vaccinium and Ledum species In southeastern Pennsylvania and north-
(Ericaceae) in the West, but in the East it em Delaware, and areas northward, "vio-
used thosegenera and also Vibunnini (Cap- lacea" I larvae feed on flowers of both P.
rifoliaceae) and Pruniis (Rosaceae). serotinaand Viburnumacerifolium. Inthese
northern areas, Cornus florida (the major
host of"violacea" I further south) is scarce
Forms and races of and declining (Sargent 1905). Larvae of
Celastraina ladon ladon "violacea" II populationsarealsoknown to
Subspecies Celastrina I. ladon readily di- feed locally on Viburnum and Aralia flow-
vides into several independent races, which ers, but in areas largely north of"violacea"
have been classically viewed as variable I where coincidentally cherrygallsare rarer.
forms ofthe same subspecies. Historically, "Violacea" I and II can be distinguished
the main forms of ssp. ladon in the East easily by adult wing scale morphology (Ta-
were known as "violacea" and "neglecta." ble 1). Where the two are sympatric, they
Fordescriptions see. Edwards (1866) ("vio- aregenerallyasynchronousandadultsofthe
lacea") and Edwards (1862) ("neglecta"). flower-feeding populations ("violacea" I)
IneasternNorth Americathereareat least peak seasonally before the gall-feeding pop-
three "violacea" races, which here are des- ulations ("violacea" II).
ignated "violacea" types I, II. and III. "Vio- The present ranges of the three races of
lacea" I conforms to the definition ofa host "violacea" appear to be primarily parapa-
race by Jaenike (1981), since it is sympatric tric: "violacea" I is in the Appalachiansand
C
with II and III (as well as race "neglecta") Ozarks (where it overlaps the range of
and exhibits a different dorsal scale mor- nigra)\ "violacea" II overlaps I in the south-
phology in regions of sympatry (Table 1). em part of its range; and "violacea" III
Thischaracter(transparent longscalesover- overlaps I on the inner coastal plain (Fig.
lappingdorsal bluescalesofthe malewings) 4). The range of"violacea" II may prove to
C
is shared only with nigra. The ranges of be more extensive than that given in Fig. 5
types II and III (which both overlap that of and extend further west and south into the
race "neglecta") are not presently known to ranges of"violacea" I and III.
overlap. They may, however, eventually The immature stages of "violacea" III
prove to marginally overlap in Delaware, have been recorded on fourIle.x(holly) spe-
Maryland, eastern Virginia, or New Jersey cies (Appendix). Male and female flowers
(Fig. 5). occur on different plants in Ilex (dioecious)
The "violacea" races differ in larval food and in order to determine whether "viola-
plants: type I ("violacea" Edwards) feedson cea" III uses one or both sexes, the flowers
Cornusflorida flowersand fruitsthroughout of more than 20 plants of each sex of /.
most ofits range; type II feeds on leafgalls glabra were beaten into a heavy cloth net
ofPrimusserotina. inducedbytheeriophyid at Warren Grove, NewJersey, in mid-June,
mite Phytoptus cerasicrumena Walsh; and 1991. Interestingly, larvae(n > 20thirdand
typeIII feedson male flowersofIlexspecies fourth instars)wereobtained onlyfrom male
(Appendix). Inmostcaseswherematurelar- plants; female plants contained no larvae.
574 PROCEEDINGS OFTHE ENTOMOLOGICAL SOCIETY OFWASHINGTON
C
Race "neglecta" occurs throughout most isolated from I. lucia. since their adults
ofthe East and its range correlates precisely generally occur later in the season.
with Fig. 4b. It occurs with the other three
Discussion
"violacea" races, but generally later in the
season. It's distinguished from "violacea" Ancestral celastrina is believed to have
racesbywhitescaleinsuffusionintothedor- enteredNorthAmericafrom Eurasiaduring
sal blue scales ofthe male wings (Table 1). a period when the Beringland bridgejoined
C
"Neglecta" differs from neglectamajor North America and Siberia (Ehot 1973).
only in the maximal size ofthe adults and Most of the diversity of the Lycaenopsis
several minor features (Table 1). There are section of the Polyommatini (blues), in-
also populations of"neglecta" which share cluding Celastrina Tutt, occurs in the Ori-
the same larval host (Cimicifiiga racemosa) ental region (Eliot 1973, Eliot and Kawazoe
with C. neglectamajor. adding to the diffi- 1983). In the Orient there are 14 Celastrina
culty in their identification. However, they species, while in North America there are
dodifferin first instarcharacterswhich sup- onlythree specieswhich upto recentlywere
C
ports their separate species status. Celastri- all considered conspecific with Eurasian
na neglectamajor first instars are yellow, argiolus (Scott 1986, Eliot and Kawazoe
whileall C. ladon(includingrace "neglecta" 1983).
on Cimicifuga racemosa)aregreen. The pri- Within the Eurasian Celastrina. C. argi-
mary dorsal setae on meso/metathorax are olusseemsmostcloselyrelatedtotheNorth
also shorter in neglectamajor first instars. American Celastrina because of its distri-
Celastrina neglectamajor larvae can suc- bution in northern latitudes and morpho-
cessfullydevelopon host Cimicifugaleaves, logical similarities with many North Amer-
while these leaves appear to be toxic to icantaxa. ItfollowsthattheNorthAmerican
"neglecta" larvae. Lastly, the two Celastri- taxon most closely resemblingargiolus may
na on Cimicifuga racemosa also differ in therefore be a direct descendent ofthe an-
their seasonal occurrence; larvae ofC. neg- cestor which crossed the Bering land bridge
lectamajorgenerally occurearlierthan those (Beringia). The range ofsubspecies luciaex-
ofrace "neglecta" on Cimicifuga racemosa. tends closest to present-day Beringia. but
since theiradults fly earlier. In the northern luciahasadistinctivewingmorphologywith
part of its range, race "neglecta" does not nocharacters sharedwith any Eurasian Cel-
appearuntil late spring or summerafterthe astrina. and thus appears to be an unlikely
flights of the spring taxa are over. In the ancestor (Eliot & Kawazoe 1983). On the
southern part ofthe range, however, "neg- other hand, the western subspecies echo is
C
lecta" ismultibrooded (including springand considerably more similar to argiolus in
summer broods). wingmorphologyandcoloration. Withinthe
Celastrina I. ladon is the only subspecies rangeofechotherearepopulations in which
C
knowntoextensivelyoverlapother ladon the form "bakeri" (recognized by greenish
subspecies in North America. As race "ne- tinton basal ventralwingsurfaces)arecom-
glecta", C I. ladon overlaps C I. sidara in mon. The "bakeri" character is also partic-
north central Colorado (Fig. 3), and as sev- ularlystronginthenominateEuropean sub-
C C
eral other races, it also overlaps I. liicia species a. argiolus (Higgins and Riley
in the northeastern portionofitsrange(Figs. 1975). In both Eurasia and western North
4, 5). The ranges of"violacea" II and "ne- America, we suspect the "bakeri" character
glecta" broadly overlap liicia in the North- is a retained plesiomorphy shared with the
east, and"violacea" III (anotherladonrace) original North American ancestor.
occurs with lucia in southern New Jersey. It is interesting that the greatest species
These races of C. I. ladon are seasonally diversity in North American Celastrina (3
VOLUME 96. NUMBER 3 575
species) occurs in the East, and in contrast lowed in order by "violacea" I and nigra.
only one is recognized in the West. If the "violacea" II and III, neglectamajor. and
primitive North American Celastrina taxa finally "neglecta."
are currently distributed in western North Only two Celastrina are broadly sympat-
America, why didn't additional species ric and synchronic in the East (C. nigra and
evolve in the West? Similar biogeographic "violacea" I). These two, however, are ge-
patterns have been made in the distribu- netically isolated through their association
tions of other North American butterflies with different hosts and habitats. Individ-
(Howe 1975). Such stereotypical patterns ualsofbothtaxaintermingleawayfrom their
suggest that the Celastrina ancestor that correspondinghabitatsat mud puddles, but
crossed the Bering land bridge into North theyarealmostalwaysmales; female Celas-
America moved into the West before en- trina and females of most other blues are
tering the East. If this is true, a paradox rarely encountered at mud puddles (Scott
exists in that western Celastrina despite a 1986). The females ofnigra and "violacea"
longer chronology in North America have I prefer habitats which correspond to their
asmallerspeciesdiversitythantheireastern host'shabitat. Celastrina nigrafemalespre-
counterparts. It is yet possible that some or fer low vegetation along north-facing slopes
allofthewesternsubspeciesaredistinctspe- and shady creek bottoms where Aruncus
cies. Allozyme studies are in progress to in- dioicusgrows, whereas "violacea" I females
vestigate this possibility. preferflyingamongthe subcanopy tree tops
Thedifferentdegreeofhostspecialization of woodland Cornus florida. Male mate-
betweeneastern andwestern Celastrina may searchingbehaviorsofthese Celastrinaseem
help explain the greater species diversity in tocoincidewiththeirconspecific femalebe-
the East. Larvae ofall western taxa. as far havior, so that opposite sexes of the two
as currently known, utilize the flower buds taxa rarely ifever encounter each other.
ofmultipleplant families in a single locality Therelationshipbetween springluciaand
(polyphagy). Eastern taxaingeneralarehost "violacea" I is unclear. They differ in mean
specificat anygiven locality. Onlyone east- eclosion times under laboratory conditions
em race ("neglecta") uses more than one (diapause intensity) (Pratt and Wright, in
host in a single locality, and yet it is asyn- prep.). They should be asynchronous when
chronous to all other sympatric races. Cel- in sympatry. They are generally allopatric,
astrina I. htcia uses more than one host in but come into contact in southern New En-
the East, but these hosts generally bloom at gland and southern Michigan where inter-
the same season and only one host is used mediate populations are present. At Kings-
inasinglelocality(usuallyeither I'acciniuni ton. RhodeIsland, "violacea" I populations
or Viburnum). (det. by scale morphology) utilize Vaccin-
The entire group of eastern Celastrina iuni corymbosum (a lucia host) and exhibit
VHW
species and races are adapted to host plants the unique markings oflucia. These
with seasonally limited resources (flower may be hybrid populations.
buds or young shoots). This host special- Race "neglecta" occurs through most of
ization may have selected for asynchrony the East, from central Florida to southern
between the species and races. An asyn- Canada (Fig. 4b) and west to eastern Col-
chronous mechanism inducing genetic iso- orado and North Dakota (Fig. 3). From the
lation appears likely for lucia, "violacea" I, southcentral Appalachianstosouthern New
II, and III, "neglecta," and negtectaniajor England, it is often abundant in locations
since they occur asynchronously to one an- where "violacea" I, II, III, and lucia were
other in nature in many localities in the presentduringearliermonths. Sinceitsflight
East. In general, lucia adults occur first fol- periodfollowstheothers,itwouldseem rea-