Table Of Content138 Journalofthe Lepidopterists’ Society
JournaloftheLepidopterists'Societi/
62(3),2008,138-142
NECTAR FLOWER USE AND ELECTIVITY BY BUTTERFLIES IN SUB-ALPINE MEADOWS
Maya Ezzeddine and Stephen F. Matter
DepartmentofBiologicalSciencesandCenterforEnvironmentalStudies, UniversityofCincinnati,CincinnatiOH45221-0006;
email:[email protected]
ABSTRACT. Nectarflowers are an important resource formostadultbutterflies. Nectarflowereleetivitywas evaluatedforthe
pieridbutterfliesPontiaoccidentalis (Reak.), Colias nastes Bdv., ColiasChristina Edw., Coliasmeadii Edw., ColiasphilodiceGodt.,
andPieris rapae (L.), andthenymphalid'Nymphalismilberti (Godt.). Butterflieswereobserved in aseriesofsub-alpine meadows
in Kananaskis Country, Alberta, Canada. Atotalof214observations ofnectarfeedingwere madeoverfouryears. The butterflies
werefoundtonectaronarangeofspeciesoffloweringplants. Despitethevarietyofflowerspeciesused,therewas relativeconsis-
tencyinuseamongbutterflyspecies.Tuftedfleabane(ErigeroncaespitosusNutt.)andfalsedandelion(Agoserisglauca(Pursh) Raf.)
werethe flowers mostfrequentlyelectedbythesebutterflies.
Additional keywords: Alpine, habitatquality,preference, Pieridae, Nymphalidae, hostplants, KananaskisCountry,Alberta
Introduction resource is particularly valuable having appropriate
For most species of butterflies, nectar is the main viscosity, sugar content, amino acids or other nutrients.
source of food energy in the adult stage. Access to Alternatively, an elected resource may simply be
nectar resources can affect manyaspects ofthe ecology enticing without offering any substantial or consistent
ofbutterflies. Forexample, flowers have been shown to benefit. Here, we examine nectar flower use and
affect the movement of butterflies. Butterflies often eleetivity by several species of butterflies within sub-
dispersetoareasorpatcheswith an abundanceofnectar alpine meadows in the Rocky Mountains of Alberta,
flowers (Peterson 1997; Brommer& Fred 1999; Matter Canada.
& Roland 2002). Similarly, butterflies may emigrate Materials and Methods
from areas low in nectar resources (Kuussaari et al.
1996), although emigration and immigration need not Study site. Nectar feeding observations and flower
respond in kind, even to the same resource (Matter & surveyswere conductedduringthe summers of2003 to
Roland2002). Thesechangesin movementpatternscan 2006 in 17 meadows along Jumpingpound Ridge,
in turn affect local abundance and potentially Alberta, Canada (51°57’N, 114°54’W). The meadows
populationgrowth. areattree-line (-2500 m) andare comprisedofgrasses,
Nectar resources may also directly influence sedges, mountain avens, and many other species of
population growth. For species that continue oogenesis wildflowers. The lower slopes of the meadows are
during the adult stage (Boggs 1997), lifetime fecundity bordered by forest consisting ofPinus contorta Dough,
can increase with the amount and quality of nectar Abies lasiocarpa (Hook.) Nutt., and Picea engelmannii
(Murphy et al. 1983; Fischer & Fiedler 2001; Mevi- Parry ex Engelm., which may be a barrier to the
Schiitz & Erhardt 2005). For species that do not dispersal ofsome species (Ross etal. 2004).
continue to mature eggs as adults, nectar may have a Study species. The butterflies examined in this
positive effect on fecundity by increasing lifespan and study all inhabit sub-alpine meadows and use the
decreasingeggresorption (Boggs & Ross 1993). flowers occurringthere as nectar sources. Each species
Despite the importance of nectar for butterfly depends on the meadows to avaryingdegree. Forsome
ecology, nectar flower use byindividual species is often species, both host plants and nectar flowers are only
present within the meadows. Other species have host
poorly known, particularlyin specific localities. Nectar
flower use can vary by region and can depend on the plants andnectarflowers occurringin the meadows and
availability of flowers and on relative nectar quality elsewhere. Some species only use these meadows for
(Scott 1986). Nectar species use and, in particular nectar flowers andhilltoppingas their larval hostplants
eleetivity, is an important aspect ofhabitat quality. Use occurin otherhabitats.
of a flower species only indicates that a butterfly may Nymphalis milberti - Eggs are normally laid on
acquire resources from thatspecies. On the otherhand, nettles (Urtica sp.) Nettles are not found in the
meadows we studied. There are dubious reports of
eleetivity indicates that a species chooses or “elects” to
feed on particular species in greater frequencythan its larvae on Helianthus, Ulmus, and Salix (Bird et al.
availability. Thus, eleetivity may indicate that a nectar 1995). A variety of flowers as well as rotting fruit and
tree sap have been reported as adult energy sources in
Volume 62, Number 3 139
other areas (Austin & Austin 1980; Iftner et al. 1992; and adult resources. At our site, oviposition on
Reed 1997). This species uses the meadows primarily Astragalus miser has been recorded (B. Christian
for nectaring; Salix glauca L. is found in the meadows Schmidt, personal observation).
and is apossible, butunlikely, host plant. Colias nastes - Astraglus alpinus L., Oxytropis
Colitis christina - Fabaceae in the genera campestris (L.) Dc., and O. splendens Dougl. ex Hook,
Hedjsamm Lupinus, andThermopsis are reportedhost are reported as larval host plants (Bird et al. 1995;
,
plants for this butterfly (Bird et al. 1995; Guppy & Guppy & Shepard 2001). Other Fabaceae are used in
Shepard 2001). Hedysamrn sulphurescens Rydb. is Europe and elsewhere (Scott 1986; Guppy & Shepard
common in these meadows andis alikelyhostplant. To 2001). A. alpinus and O. splendens can be found in the
our knowledge, nectar flowers for this species have not meadows we studied. Wyatt (1957) describes nectaring
been reported. on Arnica alpina (L.) Olin near Aklavik in the
Coliasphilodice -Larvae useavarietyofherbaceous Northwest Territories and Roland (1982) indicates that
Fabaceae, particularly Trifoliam spp. and Medicago Erigeron aureus and Tonestus (=Haplopappus) lijallii
sativa L. as host plants (Scott 1986; Bird et al. 1995; are preferred nectar flowers near our study site. This
Guppy & Shepard 2001). A range of flowers, mainly species is a meadow resident using plants within some
legumes andasters, has beenreportedas nectarsources meadows for both larval and adult resources.
(Shields 1972; Iftneret al. 1992). This species uses the Pieris rapae - Larvae of this species feed on many
meadows for nectaring and legumes occurring in the Brassicaceae, as well as on Raphanus raphanistrum L.
meadows likelyare used as hostplants. and Tropaeolum majus L. (Scott 1986; Birdet al. 1995;
Colias meadii elis - Larvae ofColiasmeadiielis feed Guppy & Shepard 2001). P. rapae prefer agricultural
on Fabaceaefoundin lowalpine meadows andvalleys in areas, especially those rich in Brassicaceae crops,
the Rocky Mountains ofAlberta and British Columbia. particularlycabbage (Birdetal. 1995; Guppy& Shepard
Roland (1982) reports Erigeron aureus Greene and 2001), but can be found in manyopen habitats. A wide
Tonestus (=Haplopappus) lijallii (A. Gray) A. Nelson as range of nectar flowers have been reported for this
preferred nectar flowers at a near-by location. In species (Iltneretal. 1992). It is likelythat the meadows
Colorado, Watt et al. (1974) detail nectaring of C. contain both local butterflies using mustards found
meadii on severalspecies in theAsteraeeae. This species within the meadows as well as immigrants from outside
is a meadow resident using local plants for both larval habitats usingthe abundantnectar llowers.
Table1. Butterflyspeciesandthenumberoftimestheywereobservednectarfeedingondifferentspeciesofflowers.Allobservationswere
madeinmeadowsalongJumpingpoundRidgeduringthesummersof2003-2006.
Nymphalis Colias Pontia
milberti christina C. meadii C. nastes C. philodice Pierisrapae occidentalis
Flower
Achilliamillifolium 2 2 20
Agoserisglauca 1 5 6 2 18
Arnicaangustifolia 1
Campanulauniflora 1 1 2
Castillejaoccidentalis 1
Delphiniumbicolor i 1
Epilobiumangustifolium 1 i 4
Erigeroncaespitosus 2 5 2 4 7 61
Erigeronperegrinus 1 5 3
Gaillardiaaristata 3
Gentianellaamarella 1
Hedysarumsulpurescens 1
Potentillafniticosa i 1 3 10
Potentillagracilis i 2
Rhinanthusminor 2
Sedumlanceolatum i i 1 2 2
Seneciocanus 1 i
Seneciolugens i
Solidagomultiradiata 1 2 2 i 1 3 9
140 Journalofthe Lepidopterists’ Society
Pontia occidentalis - Brassicaceae are the primary Theabundanceof flowerswas estimated 1-2times in
larval host plants (Bird et al. 1995; Guppy & Shepard each meadow, each year. We counted the number of
2001). Chrysothamnus nauseous (Pallas) Britt, is flowers ofall species within avarying number of2 x 10
reported as a nectar source (Opler 1995). At our site P. m, randomlyplaced transects. The numberoftransects
occidentalis is an eruptive species. In most years they per meadow varied to provide approximately
are common but not abundant. In 2003 they were proportional coverage. In 2003 and 2004 all flowers in
extremely numerous. These butterflies use the bloom were quantified, while in other years we only
meadows for nectar flowers and hilltopping when quantifiedflowers usedbyParnassiussmintheus andthe
abundant, but there is also likely an endemic fraction otherbutterflies.
using mustards found in the meadows as larval host Analyses. To examine nectar flower use we simply
plants. tallied the number of times that butterflies of each
Nectar feeding and floral abundance. species were observed feeding on different species of
Observations ofbutterflieswereconductedaspartofan flowers. To examine electivity in nectar flower use, we
on-going mark-recapture study. This study primarily comparedthe observed numberoffeedingevents to an
focuses on the spatial population dynamics and effects expected number, based on the relative abundance of
ofrising tree-line for Parnassius smintheus Doubleday, each flowerspecies. Theexpectednumberassumedthat
but we also observe and conduct mark-capture for the nectar flowers should be used in proportion to their
butterflies listed above and a fewother species. Results abundance if there is no electivity. Over-use in
and effects of nectar flowers for P. smintheus will be comparison to the expected indicates electivity while
presented in detail elsewhere. Meadowswere censused under-use would indicate repulsion. Statistical tests of
for butterflies 3-5 times each year from 2003-2006. observed versus expected nectaring events were based
Censusing took place between July 15 and August 25 on ax2distribution (Zar 1999). Alltestswereconducted
eachyear. As apartofnormalobservations,werecorded within meadows and only when flower counts and
the species of flowers on which butterflies were feeding observations were made within seven days. We
observed. In most instances these are cases of nectar also limited analysis to cases where there were five or
feeding, but occasionally butterflies may simply be more independent observations of nectar feeding for
alighting on flowers. Each captured butterfly was each butterfly species and used a significance level ofa
identifiedusingauniquethree-lettercodeon both hind = 0.01, as cases where N2/k < 10 may show bias. To
wings with apermanent felt pen. This method ensured examine finer-seale electivity, we restricted analyses to
thatwewereusingmultiple individuals in ourestimates onlythosespeciesofflowers onwhichfeedinghadbeen
of flower electivity. If the same butterflywas observed observed during the study. For an occasion where
feeding within a short period of time, only the first nectar feedingwas observed on a species offlower that
observationwas considered. was not present in any flower survey, we added one
Table2.Electivityamongfloweringspecies.Avaryingnumberofnectarfeedingevents(N)wereobservedfordifferentspeciesindifferent
meadowsondifferentdates.Thefirsttest(%~anddfontheleft)wasforelectivityamongallspeciesinflower.Thesecondtestandthepreferred
species was forelectivityonlyamongflowers used (Table 1). Notethat degrees offreedom canvaryamong meadowswithin dates due to
differencesinspeciesuse(see Methods). Significantvalues(P< 0.01)areshowninbold.
Species Meadow Date N x2 df X2 df Preferredspecies
Coliasmeadii S 1 Aug. 2003 7 77.8 14 10.9 2 Erigeroncaespitosus
C. nastes Z 4Aug.2003 6 54.9 11 22.7 5 Agoserisglauca
C. philodice L 6Aug.2003 6 32.0 5 11.5 2 Agoserisglauca
Pierisrapae S 1 Aug.2003 5 91.0 14 51.7 7 Delphiniumbicolor°
Pierisrapae L 6Aug.2003 8 35.0 9 11.7 6
Pontiaoccidentalis S 1 Aug.2003 60 195.0 19 66.7 12 Erigeroncaespitosus
Pontiaoccidentalis z 4Aug.2003 10 45.8 11 7.6 5
Pontiaoccidentalis Y 3Aug.2003 5 98.3 10 58.3 6 Agoserisglauca
Pontiaoccidentalis M 7Aug.2003 18 3117.9 16 669.1 10 Erigeroncaespitosus
Pontiaoccidentalis L 7Aug.2003 7 35.1 7 24.1 5 Agoserisglauca
°Delphiniumbicolorwasnotobservedintheflowersurveysinwhichnectarfeedingwasobserved.
)°
Volume 62, Number 3 141
occurrence of this species to the ilower abundance subalpine meadows. Strong eleetivity in combination
countswhencalculatingexpectedvalues. with the wide range of “usable” flowers suggests that
nectarresources are notparticularlylimitingat this site,
Results
thus allowing butterflies to be discriminating in their
Over the four years we observed 214 independent selection ofnectar flowers. The result alsoindicates that
nectar feeding events on nineteen species of flowers thereare differencesamongnectarflowers incharacters
(Table 1). Erigeron caespitosus had largest number of that are potentiallyimportanttothe butterflies.
nectaring events, while Solidago multiradiata Ait. was There are many reasons why certain nectar sources
used bythe greatest numberofbutterflyspecies (Table may be preferred, ranging from the accessibility and
3). Onlytwo feedingevents forNymphalis milberti and reliabilityofthe sourcetothe qualityandquantityofthe
five for Colias christina were observed. Although there nectar (Heinrich and Raven 1972, Watt et at. 1974).
were small differences, overall nectar flower use bythe That the butterflies investigated here showed similar
five most frequently observed butterfly species did not eleetivity suggests that theyare respondingto the same
differsignificantlyamongthe nineteen species ofplants characters of these flowers. It is interesting that
(G = 82.1, df= 72, P = 0.20). butterflies restricted to these meadows and more
Only in 2003 were there sufficient observations to generalist species selected similar flowers. Watt et al.
meet our criteria for analysis of eleetivity. Among all (1974) found that flowers used by Colias alexandra and
species flowering within meadows, all butterflies C. meadii inalpine meadows inColoradosharedsimilar
showed eleetivity for nectar flowers (Table 2). When ultraviolet reflectance patterns andgenerallyhad dilute
restrictedtoonlythosespeciesof flowers onwhicheach nectar containing simple sugars. A comparison of the
specieshadbeen observedfeeding, therewas still ahigh UVpatterns and nectar chemistry ofthe flowers in the
degree ofeleetivity. current system will be profitable.
It would be tempting to equate the presence and
Discussion
abundance of E. caespitosus and A. glauca with high
Thebutterflies investigatedherenectaron adiversity quality meadowhabitat for these butterflies. While it is
offlowers, but as a group they showed similar patterns true that butterflies prefer these flowers and their
in their use and preference of nectar flowers. Tufted presence would increase habitat quality, they are not
fleabane (Erigeron caespitosus) and False dandelion ubiquitous or highly abundant at our site (Table 3).
(Agoseris glauca were preferred species in these Thus, theyare acomponent of habitat qualityforadults
Table 3. Nectarflower preferences by each butterfly species as determined by the numberot feedingobservations on each flower in
proportiontothenumberofflowersofeachspecies. Preferredflowersareinbold. Datashownwerecollectedin2003.Themeandensityfor
eachflowerspeciesisoverall meadowsandsurveysduring2003.
ButterflySpecies
Density Colias Colias Colias Pieris Pontia
FlowerSpecies (mean#/20nr) meadii nastes philodice rapae occidentals
Erigeroncaespitosus 11.2 9 2 4 7 61
Agoserisglauca 6.2 1 5 6 2 18
Solidagomultiradiata 163.3 2 1 1 3 9
Potentillafruticosa 20.1 1 1 3 10
Erigeronperegrinus 10.1 1 5 3
Sedwnlanceolatum 15.3 1 1 2 2
Potentillagracilis 114.3 1 2
Seneciolugens 0.5 i
Seneciocanus 0.1 i
Arnicaangustifolia 27.6 1
Delphiniumbicolor 55.7 i
°Delphiniumbicolorwasnotobservedinthemeadowsurveysinwhichnectarfeedingwasobserved.
)
142 Journalofthe Lepidopterists’ Society
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