Cardenolide content of Danaus chrysippus butterflies from three areas of East Africa

The African butterfly Danaus chrysippus , like other members of the family Danaidae, feeds as a larva on species of milkweeds (Asclepiadaceae). It has been demonstrated in a sample from a West African population that only a minority of adult D. chrysippus accumulated detectable amounts of poisonous and presumably emetic cardenolides from their larval foodplants. It has also been shown in D. chrysippus and the related monarch butterfly ( D. plexippus ) that the cardenolide content of adults varies with that of their respective milkweed foodplants.
Three population samples of D. chrysippus from sites in East Africa are analysed for cardenolides using the spectrophotometric technique refined by Brower, Edmunds & Moffitt (1975), which allows the assay of individual butterflies. The East African samples all have a palatability spectrum with a considerably higher percentage of cardenolide-containing individuals than the West African one.
This is discussed in terms of its effect on potential bird predators and the 'automimicry' of emetic by palatable individuals. In East Africa D. chrysippus is polymorphic and appears to act as a model in a complex mimicry ring, whereas in West Africa it is monomorphic and may have 'shed' most of its mimics. This latter hypothesis is discussed in the light of our results.     

Pre- and postzygotic isolation and Haldane rule effects in reciprocal crosses of Danaus erippus and Danaus plexippus (Lepidoptera: Danainae), supported by differentiation of cuticular hydrocarbons, establish their status as separate species

Hybridization experiments and cuticular hydrocarbon analyses were performed to determine the extent of the reproductive isolation present to clarify the taxonomic status of Danaus erippus (Cramer, 1775), which has often been classified as a subspecies of Danaus plexippus (Linnaeus, 1758) . The results of crosses between D. erippus and Danaus plexippus nigrippus (Haensch, 1909) showed pre- and postzygotic isolation. Pupal inviability, and Haldane rule effects (male hybrids only, the homogametic sex in butterflies) were observed after the crosses. These results reinforce the hypothesis that D. plexippus and D. erippus are separate, reproductively isolated species. However, we have also investigated the cuticular hydrocarbons in D. erippus and D. p. nigrippus with temperature-programmed gas chromatography. The chromatographic profiles of peaks were similar in both taxa, with retention indices in the range 2100–3797. The profiles were characterized by the presence of 15 peaks whose retention indices were in the range 2501–3772. Although no major qualitative differences between the two species were observed, we did find some quantitative differences. A principal component analysis showed a clear separation between members of D. erippus and D. p. nigrippus , suggesting that semiochemical differences might have become differentiated after isolation, perhaps in response to different physiological pressures.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 445–453.     

Hybrid queen butterflies from the cross Danaus chrysippus (L.) × D. gilippus (Cramer):confirmation of species status for the parents and further support for Haldane's Rule

A cross between queen butterflies of the Palaeotropical species Danaus chrysippus and the Neotropical D. gilippus was achieved with difficulty in both directions. Only one progeny ( N  = 70) was reared comprising sterile males and inviable females in a precisely 1 : 1 ratio. Both prezygotic and postzygotic barriers to gene flow are strong. The result supports Haldane's Rule, to which we propose a minor amendment. The F₁ hybrids were intermediate for background colour between the brown (genotype BB ) of gilippus and orange (genotype bb ) of chrysippus . Most F₁ pattern characters were also intermediate. In polymorphic chrysippus populations, because Bb heterozygotes are brown, or nearly so, we suggest the B allele may have evolved towards dominance in sympatry. Hybrid males show positive heterosis for body size. The close similarity of male genitalia between the allopatric, genetically distant species chrysippus  and gilippus , compared to their divergence between gilippus and its largely sympatric sister species eresimus , suggest that reinforcement of sexual isolation or reproductive character displacement have evolved in sympatry.  © 2002 The Linnean Societyof London, Biological Journal of the Linnean Society , 2002, 76 , 535–544.     

Incomplete sexual isolation in sympatry between subspecies of the butterfly Danaus chrysippus (L.) and the creation of a hybrid zone

Subspecies chrysippus, dorippus and alcippus of the butterfly Danaus chrysippus differ at three biallelic colour gene loci. They have partially vicariant distributions, but their ranges overlap over a substantial part of central and East Africa, where hybridism is commonplace. We now report that the West African subspecies alcippus differs from other subspecies, not only in nuclear genotype but also in mitochondrial haplotype in both allopatry and sympatry. The maintenance of concordant nuclear and cytoplasmic genetic differences in sympatry, and in the face of hybridisation, is prima facie evidence for sexual isolation. Other evidence that suggests alcippus may be isolated from chrysippus and dorippus include differences in sex ratio (SR), heterozygote deficiency at one site and deduced differences in patterns of migration. We suggest that, within the hybrid zone, differential infection of subspecies by a male-killing Spiroplasma bacterium causes SR differences that restrict female choice, triggering rounds of heterotypic mating and consequent heterozygote excess that is largely confined to females. The absence of these phenomena from hybrid populations that test negative for Spiroplasma supports the hypothesis. The incomplete sexual isolation and partial vicariance of alcippus suggests that it is a nascent species.     

Polymorphic Müllerian mimicry in a group of African butterflies: a re-assessment of the relationship between Danaus chrysippus, Acraea encedon and Acraea encedana (Lepidoptera: Nymphalidae)

Müllerian mimicry, in which there is convergence in coloration between unrelated unpalatable species, should lead to uniformity in appearance, not polymorphism, and so the occurrence in tropical Africa of unrelated species of unpalatable butterflies with corresponding polymorphic colour forms suggested a problem of special evolutionary interest. Field work in Uganda and Sierra Leone in 1964 72 demonstrated a statistical association between the occurrence and relative frequencies of polymorphic forms in Danaus chrysippus (Danainae) and Acraea encedon (Acraeinae) which was deemed as confirmation of a Müllerian relationship between them. There were, however, certain anomalies which at the time remained unresolved. Later, in 1976, it was discovered that what had been called A. encedon is in reality two sibling species. A. encedon and a new one, named as A. encedana. The two differ in the structure of both male and female genitalia and in the coloration and the food-plants of the larvae. The recognition of the additional species has enabled a re-assessment of the polymorphie Müllerian association with D. chrysippus. It emerges that, although there is a close qualitative and quantitative reciprocal mimetic relationship between A. encedana and D. chrysippus, the relationship between A. encedon and D. chrysippus is much weaker, and in places non-exitent. The possible origin of the mimetic polymorphism is discussed in terms of hybridization of previously allopatric and monomorphic populations which have met as a consequence of recent expansions of geographical range in all three species resulting from forest clearance and the spread of savanna-like conditions in previously forested areas.     

金斑蝶生物学与规模化饲养的初步研究

记述了金斑蝶Danaus chrysippus chrysippus(Linnaeus)的形态特征、生物学特性与规模化饲养的方法.该蝶在海南尖峰岭地区全年发生、世代重叠,1年发生15代左右,完成1个世代冬季需29～37d,夏季14～18d.成虫抗逆性与生命力强,耐高温,嗜食的寄主植物有马利筋Asclepias curassavica L.和牛角瓜Calotropis gigantean(L).金斑蝶色彩艳丽、飞翔姿态缓慢优美,宜在生态蝴蝶园与喜庆等场合放飞,良好的生态环境是金斑蝶规模化饲养成功的关键,而幼虫饲养是它规模化饲养的重要环节.成虫卵散生,幼虫5龄,初孵幼虫宜室外套网袋饲养,5龄后期用塑料盆室内饲养并使之化蛹于盆盖上,将盆盖挂入羽化室内,通过空调和喷雾装置温度控制在25～28℃,湿度控制在60～80%,使蛹能正常发育和羽化.     

A classification of Danaus butterflies (Lepidoptera: Nymphalidae) based upon data from morphology and DNA

Classification of the cosmopolitan butterfly genus Danaus (Nymphalidae: Danainae) is revised at subgeneric, specific and subspecific levels, combining for the first time mitochondrial and nuclear DNA sequence information with morphological data. Tree topologies based on the nuclear genome (allozymes, pheromone components, the morphology of all life history stages and nuclear DNA sequences), on the one hand, and mitochondrial DNA, on the other, are incongruent and challenge the current taxonomy of the genus. Although earlier classifications, based on adult morphology alone, are, in general, well supported by an analysis of total evidence, the mitochondrial phylogeny shows that the species D. chrysippus and its subgenus Anosia are deeply paraphyletic. Subspecies dorippus of D. chrysippus is the basal clade of the genus and is reinstated as the species D. dorippus. The former species D. plexaure is demoted to a subspecies of D. eresimus. The specific status of D. erippus, as distinct from D. plexippus, is tentatively supported. On the strength of the new data, division of the monophyletic genus Danaus s.l. into three subgenera Danaus s.s., Salatura and Anosia is unsustainable and is abandoned. Of the 15 terminal clades (taxa) of Danaus s.l. included in the study, 11 are species that broadly conform to the biological species concept. (The West Indian species D. cleophile, missing from our analysis, is the twelfth species). The remaining terminal clades are subspecies of D. chrysippus comb. nov. and D. dorippus stat. rev. Two sympatric Neotropical species, D. eresimus and D. gilippus, are morphologically distinct and sexually isolated but have nearly identical mitochondrial genomes. In contrast, two partially sympatric Palaeotropical species, D. chrysippus and D. dorippus, are cryptic species that share structural morphology and hybridize but have highly differentiated mitochondrial genomes. D. dorippus is polymorphic for two anciently diverged haplotypes and its history has possibly involved recombinational speciation and/or hybridism. © 2005 The Linnean Society of London, Zoological Journal of the Linnean Society, 2005, 144 , 191?212.     

The butterfly Danaus chrysippus (L.) in East Africa comprises polyphyletic, sympatric lineages that are, despite behavioural isolation, driven to hybridization by female-biased sex ratios

Mitochondrial and nuclear DNA information was analysed among four subspecies of the African Queen butterfly, Danaus (Anosia) chrysippus sensu lato (s.l.), along with four other Danaus species drawn from all three subgenera (D. (Danaus) plexippus, D. (Salatura) genutia, D. (A.) gilippus, D. (A.) eresimus) and two outgroup species from the same tribe, Tirumala septentrionis and Amauris niavius. A mitochondrial phylogeny derived from the 12S rRNA (347 bp) and COI (537 bp) loci indicates two very distinct haplotypes for subspecies D. (A.) c. dorippus, dorippus‐1 and dorippus‐2. Interestingly, dorippus‐1, on the one hand, and all other D. (A.) chrysippus haplotypes, on the other, are the most distantly related clades within the genus and have different most recent ancestors from different subgenera, though sharing the common ancestor of the monophyletic genus. A phylogeny based on the EF1‐α nuclear locus (400 bp) shows that the two well‐separated mitochondrial lineages of dorippus are identical for this gene and reciprocally monophyletic to the other D. (A.) chrysippus lineages. Thus, nuclear and cytoplasmic phylogenies are not only discordant, but also suggest that both D. (A.) chrysippus s.l. and subspecies dorippus are polyphyletic. Paradoxically, four African subspecies, chrysippus‐orange, chrysippus‐brown, alcippus and dorippus, though substantially vicariant, hybridize extensively in East Africa wherever the ranges of two or more of them overlap. Linkage disequilibrium, and hence sexual isolation, in sympatry between colour (nuclear) genes and unlinked mitochondrial (cytoplasmic) loci is consistent across populations and therefore indicates the operation of positive natural selection. Together with data from previous experimental and field work, our results suggest that extensive hybridization occurs among once allopatric or parapatric lineages, that are now nascent species. We deduce that hybridism among lineages in sympatry is currently enforced, in the face of assortative mate choice, by a bacterial symbiont, Spiroplasma, a male‐killer that forces females in female‐biased populations to pair with heterotypic males. In discussion we emphasize that neither D. (A.) chrysippus s.l. as presently circumscribed, nor its component clades, conform to any established concept of species. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 86 , 117–131.     

Fine structure and development of the silver and golden cuticle in butterfly pupae

Pupae of the butterflies Danaus chrysippus and Helioconius charitonius display characteristic patterns of golden spots, while the pupae of the genera Euploea and Amauris exhibit metallic lustre over most of their surface; E. core and midamus more golden, A. ochlea and niavius more silvery. The absolute reflectance exceeds 80% at wavelengths longer than 550 nm, but drops more or less steeply at shorter wavelengths (shown by microspectrophotometry for E. core and A. ochlea; in all species this effect is caused by constructive interference of the incident light at Multiple Endocuticular Thin Alternating Layers (METAL cuticle). Dense, cuticular D layers alternate with clear, watery C layers and form over 200 double layers. The thickness of the D layers is fairly constant throughout the stack, whereas the C layers systematically increase and decrease in thickness, thus causing the broad bandwidth of the reflector. Connecting filaments, traversing the C layers in zig zag course, probably secure the mechanical stability of the arrangement. After drying, the C layers have vanished and the lustre is lost; the cuticle is now perfectly transparent, except for D. chrysippus, where it is partly transparent and partly yellow. The metallic reflectance develops between 20 and 30 hr after pupal ecdysis, starting with blue colours which change via green to gold or silver. About half a day before emergence of the imago, the reflection fades again via the opposite colour sequence. Coincident with these colour changes, the METAL cuticle is being deposited and decomposed, respectively. The deposition zone immediately above the apical epidermal microvilli consists of about three helicoidal lamellae as in normal, non-reflecting cuticle. The METAL cuticle is formed abruptly at the outer border of the deposition zone, possibly during condensation of the cuticular microfibres. The periodicity it is suggested is controlled either directly by the epidermal cells or indirectly via appropriate self-assembling processes.     

Hologenomic speciation: synergy between a male‐killing bacterium and sex‐linkage creates a ‘magic trait’ in a butterfly hybrid zone

Danaus chrysippus (L.) in Africa comprises four substantially isolated semispecies that are migratory and hybridize on a seasonal basis throughout the eastern and central part of the continent. In the hybrid zone (but not elsewhere), the butterfly is commonly host to a male killing endosymbiotic bacterium, Spiroplasma sp., which principally infects one semispecies, Danaus chrysippus chrysippus in Kenya. A W‐autosome mutation, inherited strictly matrilinearly, links B and C colour gene loci, which have thus gained sex‐linkage in chrysippus. We have monitored variation in sex ratio and genotype at the A and C colour gene loci for two extended periods of 18 months (2004–5) and 12 months (2009–10) in adults reared from wild eggs laid on trap plants in Kasarani, near Nairobi, Kenya. Additionally, in 2009–10, all surviving adult butterflies were screened for Spiroplasma infection. The hybridizing Kasarani population is highly atypical in three respects, and has apparently been so for some 30 years: first, the sex ratio is permanently female‐biased (as expected), although subject to seasonal fluctuation, being lowest (male/female) when D. c. chrysippus (cc) peaks and highest when Danaus chrysippus dorippus (CC) predominates; second, the population is invariably dominated by Cc heterozygotes of both sexes but especially females; and third, cc males are always scarce because they are systematically eliminated by male killing, whereas the CC genotype is male‐biased. It is this imbalance of sex versus genotype that determines the massive departure from Hardy–Weinberg equilibrium in the population, in part because cc females have little choice but to pair with C‐ males. We suggest that: first, Cc hybrids of both sexes fail to disperse in the company of either parental semispecies; second, Spiroplasma positive females carrying the W‐autosome mutation have a selective advantage over females that lack the translocation; third, the endoparasite and the translocation create a ‘magic trait’ linkage group that underlies hologenomic reproductive isolation between two emerging species, D. c. chrysippus and D. c. dorippus; and, fourth, that the predominance of males in dorippus suggests that individuals must be protected by a male‐killing suppressor gene. By contrast to the C locus, Aa heterozygotes are in substantial and permanent deficit, suggesting either assortative mating between AA (chrysippus and dorippus) and aa (Danaus chrysippus alcippus), or heterozygote unfitness, or both. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 92–109.     

Spatial metabolomics reveal divergent cardenolide processing in the monarch (Danaus plexippus) and the common crow butterfly (Euploea core)

Although being famous for sequestering milkweed cardenolides, the mechanism of sequestration and where cardenolides are localized in caterpillars of the monarch butterfly (Danaus plexippus, Lepidoptera: Danaini) is still unknown. While monarchs tolerate cardenolides by a resistant Na⁺/K⁺-ATPase, it is unclear how closely related species such as the nonsequestering common crow butterfly (Euploea core, Lepidoptera: Danaini) cope with these toxins. Using novel atmospheric-pressure scanning microprobe matrix-assisted laser/desorption ionization mass spectrometry imaging, we compared the distribution of cardenolides in caterpillars of D. plexippus and E. core. Specifically, we tested at which physiological scale quantitative differences between both species are mediated and how cardenolides distribute across body tissues. Whereas D. plexippus sequestered most cardenolides from milkweed (Asclepias curassavica), no cardenolides were found in the tissues of E. core. Remarkably, quantitative differences already manifest in the gut lumen: while monarchs retain and accumulate cardenolides above plant concentrations, the toxins are degraded in the gut lumen of crows. We visualized cardenolide transport over the monarch midgut epithelium and identified integument cells as the final site of storage where defences might be perceived by predators. Our study provides molecular insight into cardenolide sequestration and highlights the great potential of mass spectrometry imaging for understanding the kinetics of multiple compounds including endogenous metabolites, plant toxins, or insecticides in insects.     

The evolution of cardenolide-resistant forms of Na⁺,K⁺ -ATPase in Danainae butterflies

Cardenolides are a class of plant secondary compounds that inhibit the proper functioning of the Na⁺, K⁺‐ATPase enzyme in susceptible animals. Nonetheless, many insect species are able to sequester cardenolides for their own defence. These include butterflies in the subfamily Danainae (Family: Nymphalidae) such as the monarch (Danaus plexippus). Previous studies demonstrated that monarchs harbour an asparagine (N) to histidine (H) substitution (N122H) in the α subunit of Na⁺, K⁺‐ATPase (ATPα) that reduces this enzyme’s sensitivity to cardenolides. More recently, it has been suggested that at ATPα position 111, monarchs may also harbour a leucine (L)/glutamine (Q) polymorphism. This later amino acid could also contribute to cardenolide insensitivity. However, here we find that incorrect annotation of the initially reported DNA sequence for ATPα has led to several erroneous conclusions. Using a population genetic and phylogenetic analysis of monarchs and their close relatives, we show that an ancient Q111L substitution occurred prior to the radiation of all Danainae, followed by a second substitution at the same site to valine (V), which arose before the diversification of the Danaus genus. In contrast, N122H appears to be a recent substitution specific to monarchs. Surprisingly, examination of a broader insect phylogeny reveals that the same progression of amino acid substitutions (Q111L → L111V + N122H) has also occurred in Chyrsochus beetles (Family: Chrysomelidae, Subfamily: Eumolpinae) that feed on cardenolide‐containing host plants. The parallel pattern of amino acid substitution in these two distantly related lineages is consistent with an adaptive role for these substitutions in reducing cardenolide sensitivity and suggests that their temporal order may be limited by epistatic interactions.     

Chemoenzymatic synthesis of (E)-3,7-dimethyl-2-octene-1,8-diol isolated from the hairpencils of male Danaus chrysippus (African Monarch)

The synthesis of (E)-3,7-dimethyl-2-octene-1,8-diol (1), which was isolated from the hairpencils of male Danaus chrysippus (African Monarch), was investigated. The key step of the sequence involves asymmetric desymmetrization of the 1,3-propanediol 7 with lipase, in which high enantioselectivity was observed. Total synthesis afforded (S)-1 in 12 steps and 26% overall yield from readily available geraniol.     

Natural selection for rare and mimetic colour pattern combinations in wild populations of the diadem butterfly, Hypolimnas misippus L

Mark recapture and morph frequency data, gathered during a population irruption of Hypolimnas misippus in southern Ghana, provide evidence for apostatic and mimetic selection. During a period of low adult survival, both the recapture rate and the frequency of the commonest morph ( misippus ) were significantly reduced. Selection against this form increased phenotypic diversity and generated significant disequilibrium in the combinations of unlinked fore- and hindwing phenotypes. There was also evidence for selection against those forms (weak alcippoides ) which most closely resemble misippus . Other morphs, including both good mimics of Danaus chrysippus and rare non-mimics, showed no reductions in recapture rate during the period of low survival, but only the good mimics increased significantly in frequency. The results provide a predictive ecological model for density-dependent selection by predators which is consistent with field data from previous studies of H. misippus in Ghana and Tanzania. Their evolutionary implications are discussed, and it is suggested that anomalies in the mimicry of this species may be partly due to lack of predation when it is scarce.     

Systematics and evolutionary relationships of the mountain lizard Liolaemus monticola (Liolaemini): how morphological and molecular evidence contributes to reveal hidden species diversity

The delimitation of species is a major issue in systematic biology and has been a re-emerging discipline in the last decade. A number of studies have shown that the use of multiple data sets is critical for the identification of cryptic species, particularly in groups with complex evolutionary histories. Liolaemus monticola is a montane lizard species distributed in central Chile (32°–42°S), with four described subspecies in a latitudinal gradient from north to south: L. m. monticola , L. m. chillanensis , L. monticola ssp. and L. m. villaricensis . In order to test the systematic status and phylogenetic relationships of the taxa included in the L. monticola group, we analysed morphological (morphometric and meristic) and molecular (allozyme and mitochondrial DNA) data sets. The results of the morphological analyses showed that meristic variables correctly assigned individuals with higher accuracy than did morphometric characters. The results of the analyses of allozyme data revealed eight diagnostic loci that are evidence for significant differences among the four L. monticola subspecies. Phylogenetic analyses with mitochondrial DNA data, including additional species, showed that the L. monticola group is polyphyletic. We postulate that the four current subspecies represent independent evolutionary lineages and must be raised to the specific level as L. monticola , L. chillanensis and L. villaricensis . The taxonomic status of the unnamed L. monticola ssp. remains unresolved, although we provide a preliminary proposal.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 635–650.     

The Deschampsia cespitosa complex (Poaceae: Aveneae) with special reference to Russia

The Deschampsia cespitosa complex in Russia is revised. Related taxa common to Russia and adjacent regions (i.e. northern Europe, Arctic America and Japan) are also considered. Deschampsia cespitosa s.l. is characterized by open to less commonly rather contracted panicles, spikelets (1) 2 (3)-flowered, 4-toothed lemmas with the lateral teeth larger, and awns straight or bent, inserted from the base to the top of the lemmas. Due to extensive overlapping in diagnostic characters, it is not possible to accept the specific status for D. borealis (Traut.) Roshev., D. brevifolia R.Br., D. macrothyrsa Tatew. et Ohwi and D. obensis Roshev; instead, they are treated as subspecies of D. cespitosa (L.) Beauv. Morphological differences are insufficient for a clear differentiation among subspecies, and geographical distributions also need to be considered. A total of 14 subspecies is accepted. Observations on ecology, problems of specific and subspecific delimitation, a distribution map, and considerations of evolution of the complex are provided. One new combination is made, Deschampsia cespitosa ssp. sukatschewii (Popl.) Chiapella & Prob.  © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society , 2003, 142 , 213–228.     

Visual and Olfactory Responses of Seven Butterfly Species During Foraging

Foraging responses of seven butterfly species were determined for flower models that differed in color, size, and depth of artificial corolla. We measured frequency of visits to flowers of various colors (red, orange, yellow, purple, and white) with or without the application of honey water to flower models. We found that the relative strength of butterfly response to visual versus olfactory cues differed among butterfly species. We suggest that the seven butterfly species tested exhibit four different patterns in how visual and olfactory cues were combined as determinants of foraging importance: (1) vision was given priority over olfaction (in Cethosia cyane and Danaus chrysippus); (2) olfaction was given priority over vision (Cethosia biblis, Idea leuconoe, and Tirumala limniace); (3) olfaction and vision were equally important (Catopsilia pomona); and (4) only olfaction was used (e.g., Danaus genutia, which was not sensitive to the five colors tested but very sensitive to the smell of honey in our experiments). In tests with flower models of different sizes, the visitation frequency of C. cyane, I. leuconoe, and D. chrysippus increased with increasing corolla diameter, provided flowers were sprayed with honey water. C. cyane and D. chrysippus showed this trend because of their strong dependence on visual cues. In contrast, I. leuconoe with its large body size preferred larger flowers, it could be that butterflies need more nectar to support its large body size. Catopsilia pomona tended to visit large and middle-sized flowers because it used both vision and odor to detect food, large or middle-sized flowers could have more vision and odor stimulation than small flowers for foraging butterfly. The other three butterfly species did not show that trend because of lack of dependence on visual cues. There was no correlation between visitation frequency and corolla depth within particular butterfly species. In conclusion, the foraging strategies of butterflies are not only mainly determined by the weights given to visual and olfactory cues, but also affected by body size.     

A phenetic analysis and revision of Guineo-Congolean rain forest taxa of Chlorophytum (Anthericaceae)

The taxonomy of rain forest species of the genus Chlorophytum in central and west Africa has to date been difficult to resolve. Plants collected in the Guineo-Congolean plant geographical region deposited in several herbaria formed the basis for a morphometric analysis using Principal Component Analyses and including 16 characters. In total, 166 individuals were included from 461 herbarium collections, from which 57 seeds were scanned to investigate the surface structures. Eight species are recognized, including one with three subspecies and another with three varieties. Four new combinations are proposed ( Chlorophytum comosum (Thunb.) Jacques var. bipindense (Engl. & K. Krause) A.D. Poulsen & Nordal, C. comosum (Thunb.) Jacques var. sparsiflorum (Baker) A.D. Poulsen & Nordal, C. lancifolium Baker ssp. cordatum (Engl.) A.D. Poulsen & Nordal, and C. lancifolium Baker ssp. togoense (Engl.) A.D. Poulsen & Nordal), ten new synonyms are introduced and three lectotypes are designated.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 1–20.     

Monarch butterfly host plant (milkweed Asclepias spp.) abundance varies by habitat type across 98 prairies

The decline in migratory monarch butterflies (Danaus plexippus) over the past 20 years has been attributed to several drivers, including loss of their host plants (milkweeds Asclepias spp.). This has sparked widespread interest in milkweed ecology and restoration. We developed a model on environmental and habitat‐type variables to predict milkweed abundance by sampling 93 prairie plantings (47 conservation plantings and 46 roadsides) and 5 unplowed prairie remnants throughout the state of Iowa, United States. Milkweeds were censused in 10–25 random locations within each site, and data on plant diversity, age of planting, soil characteristics, and management were tested as predictors of abundance. Milkweed densities of all species combined were highest in remnant prairies (8,705 stems/ha), intermediate in roadside plantings (1,274 stems/ha), and lowest in conservation plantings (212 stems/ha). Most milkweeds were common milkweeds Asclepias syriaca, which were more abundant in roadside than conservation plantings. Remnants contained the most milkweed species. Total milkweed and common milkweed abundance were both predicted by higher soil pH, a more linear site shape, and lower soil bulk density across restorations. Our results indicate that common milkweed is maintained by disturbance, and establishes readily in rural roadside habitat. Remnants are important as reservoirs for multiple milkweed species and should be protected.