Senecio Species Research Articles

DNA barcoding of endophagous immature stages elucidates the host-plant affinities of insects associated with the invasive Senecio madagascariensis in its native range in South Africa

Senecio madagascariensis Poiret (Asteraceae), an invasive herb from southern Africa that inflicts high economic losses in several countries worldwide, is currently a target for biological control in Australia and Hawaii. Several candidate insect agents were identified from the weed’s native range in South Africa. Confirmation of narrow host ranges, prior to agent importations into quarantine, is important for Australia given its rich native Senecio flora. In particular, surveys for candidate agents on closely related non-target plants in the native range can differentiate between host specific and unsuitable agents at an early stage. This study focused on endophagous insects from families that were deployed in biocontrol programmes against other weedy Asteraceae. The host-plant affinities of stem-boring Coleoptera and stem-boring and capitulum-feeding Lepidoptera and Diptera were assessed across 18 native herbaceous Senecio species in KwaZulu-Natal, South Africa. Since larval morphology is typically unable to confirm insect identity, DNA barcoding was used to differentiate between insect species associated with different Senecio species to determine their host-plant affinities. COI phylogenies revealed that stem-boring Curculionidae and Tortricidae and capitulum-feeding Pterophoridae and Tephritidae that are associated with S. madagascariensis were restricted to plants in the S. madagascariensis species complex. In contrast, none of the stem-boring Agromyzidae were restricted to S.madagascariensis or its species complex. This study has supported the selection of several potentially host-specific agents for S. madagascariensis that could be imported for quarantine testing in Australia and Hawaii.

Strong divergent selection at multiple loci in two closely related species of ragworts adapted to high and low elevations on Mount Etna.

Recently diverged species present particularly informative systems for studying speciation and maintenance of genetic divergence in the face of gene flow. We investigated speciation in two closely related Senecio species, S.aethnensis and S.chrysanthemifolius, which grow at high and low elevations, respectively, on Mount Etna, Sicily and form a hybrid zone at intermediate elevations. We used a newly generated genome-wide single nucleotide polymorphism (SNP) dataset from 192 individuals collected over 18 localities along an elevational gradient to reconstruct the likely history of speciation, identify highly differentiated SNPs, and estimate the strength of divergent selection. We found that speciation in this system involved heterogeneous and bidirectional gene flow along the genome, and species experienced marked population size changes in the past. Furthermore, we identified highly-differentiated SNPs between the species, some of which are located in genes potentially involved in ecological differences between species (such as photosynthesis and UV response). We analysed the shape of these SNPs' allele frequency clines along the elevational gradient. These clines show significantly variable coincidence and concordance, indicative of the presence of multifarious selective forces. Selection against hybrids is estimated to be very strong (0.16-0.78) and one of the highest reported in literature. The combination of strong cumulative selection across the genome and previously identified intrinsic incompatibilities probably work together to maintain the genetic and phenotypic differentiation between these species - pointing to the importance of considering both intrinsic and extrinsic factors when studying divergence and speciation.

Insect herbivores associated with the invasive herb Senecio madagascariensis (Asteraceae) in its native range in KwaZulu-Natal, South Africa and their potential as biological control agents in invaded countries

ABSTRACTNative to southern Africa, Senecio madagascariensis Poir. (fireweed, Asteraceae) has invaded agricultural lands and disturbed areas in several countries worldwide and is currently a target for biological control in Australia and the USA (Hawaii). Quantitative surveys of the plant in KwaZulu-Natal, South Africa, considered the origin of the Australian and Hawaiian populations, revealed several insect herbivore taxa that are frequently associated with the plant’s foliar, floral and structural tissues. These largely comprised ectophagous sap suckers (34%), chewers (29%) and root feeders (1%), but also endophagous stem borers (21%), capitulum feeders (13%) and leaf miners (2%). Many of these taxa were encountered only occasionally or rarely during sampling, with some displaying low to very low abundance. Based on these surveys and earlier precedents in biocontrol programmes against other invasive Asteraceae, 15 taxa were shortlisted as candidate agents. Of these, four were prioritised for host-range assessments which are currently in progress. These include the capitulum-feeding Homoeosoma stenotea Hampson (Lepidoptera: Pyralidae), the stem-boring Gasteroclisus tricostalis (Thunberg) (Coleoptera: Curculionidae) and Metamesia elegans (Walsingham) (Lepidoptera: Tortricidae) and the root-feeding Longitarsus basutoensis Bechyné (Coleoptera: Chrysomelidae: Alticinae). Although the diversity of native Senecio species in Australia may present challenges during routine host-specificity testing, prospects for the biocontrol of S. madagascariensis in Hawaii appear very promising, since the native flora does not include any species in the tribe Senecioneae.

Three new species and some nomenclatural changes in Senecio (Compositae/Asteraceae: Senecioneae) in the Flora Zambesiaca area

SummaryThree new Senecio species are described, S. fanshawei from Zambia, S. ngandae from Malawi and S. nyangani from Zimbabwe. A new combination is made under S. brachypodus and a taxon is added to the synonymy of this species; single taxa are added for the first time to the synonymy of S. coronatus and S. purpureus, and two taxa each are added for the first time to the synonymy of S. hochstetteri and S. triactinus.

Senecio spp. transboundary introduction and expansion affecting cattle in Uruguay: Clinico-pathological, epidemiological and genetic survey, and experimental intoxication with Senecio oxyphyllus

The genus Senecio is distributed worldwide, being responsible of poisoning in livestock and humans. Many species of Senecio have high invasion and expansion capacity, highly competitive with agricultural and native plant species, causing ecological damage. Particularly in Uruguay, poisoning by Senecio have grown exponentially to reach epidemic proportions. Herein we describe Seneciosis as a re-emerging and expanding epidemic disease affecting cattle, by describing clinico-pathological, epidemiological and genetic variation of species involved, as well as an experimental intoxication with Senecio oxyphyllus. For this, a study was carried out on 28 cattle farms in Eastern Uruguay, with history of seneciosis from 2010 to 2016. Plants of fifty populations of Senecio were sampled, in 2015 and 2016, for identification, analysis of alkaloids and study of genetic variation. In turn, post-mortem examination was performed in cattle of natural and an experimental case to confirm the intoxication, showing microscopic characteristic lesions (hepatomegalocytosis, diffuse fibrosis and ductal reaction). Four species of Senecio were identified: S. oxyphyllus, S. madagascariensis, S. selloi and S. brasiliensis. In the genetic study, 489 molecular markers of amplified sequence-related polymorphisms (SRAP), associated with species and pasture, were used for genetic variation analysis. There was no statistically significant association between genetic variation determined by molecular markers and population (specimens of same species collected from the same farm), botanically determined species, or geographical origin. The increase of seneciosis in cattle in the last years, the presence of species not identified to the moment with implication in the poisoning outbreaks and expansion of these plants shows that the disease is in an epidemic growing active stage. In turn, the experimental poisoning with S. oxyphyllus confirms its chronic hepatotoxic effect, being an emergent species for the region, of high distribution and toxic risk. This latter turned out the main Senecio species involved. This case of expansion of harmful plant for animal production and desirable plant species, can be useful as a model of ecopathological characterization, which is likely to occur with other toxic plants in different geographical ranges globally.

Contributions to the Andean <em>Senecioneae (Compositae)</em>, part III: A new species of <em>Senecio</em> from northern Chile

A new species of Senecio L. from northern Chile is described on the basis of morphological evidence. It is a caespitose species characterized by displaying vertical hypogeous stems, fleshy spatulate leaves, subentire or distantly and shallowly dentate, discoid capitula with yellowish disc florets, anthers, and style branches, and long-pilose achenes. It is compared with the morphologically related species S. algens Wedd., S. altoandinus Cabrera, and S. cremnicola Cabrera. Detailed pictures of living plants are provided.

New combinations and synonyms in discoid caespitose Andean Senecio (Senecioneae, Compositae).

The names Werneriamelanandra and W.pygmophylla are transferred to the genus Senecio. They belong to the group of the discoid caespitose Andean Senecio, specifically to the subgroup with blackish anthers and style branches and whitish corollas. The recognition of S.digitatus as a distinct species is also discussed. Within the framework of the mentioned group, the names S.casapaltensis and S.macrorrhizus are lectotypified, S.humillimusvar.melanolepis is neotypified, an epitype is designated for the name W.melanandra, and nine new synonyms are proposed. An updated comprehensive dichotomous key including all discoid caespitose Senecio species from Bolivia and Peru is provided.

Simulated herbivory counteracts the effects of grass competition on the invasive fireweed (Senecio madagascariensis)

AbstractCompetition, herbivory and their interaction play a significant role in determining the competitive ability and survival of individual plant species. Understanding these processes and interactions can improve the efficacy of biocontrol programs against invasive weeds. Senecio madagascariensis (fireweed) is an invasive weed of South African origin that reduces pastoral productivity and poisons livestock in several countries, notably Australia. Although competitive pastures can suppress the weed’s growth in Australia, its competitive nature is poorly understood in relation to its invasion success. This greenhouse study assessed the growth and reproductive yield of fireweed growing in competition with six native and introduced grasses present in both South Africa and Australia. Since fireweed is a target for biocontrol in Australia, we examined whether its response to grass competition changed with herbivory (simulated by 40% leaf removal). The effect of grass competition and herbivory on the weed’s biomass and floral productivity was examined during a 12‐week pot trial in South Africa. Floral numbers were unaffected by both grass competition and herbivory. Biomass was used to calculate Relative Interaction Indices (RII) to quantify the weed’s competitive or facilitative response. This index compares a specific measurable trait, such as biomass, of fireweed growing alone, to fireweed growing with grass to determine the level of competitive suppression or facilitation resulting from the interaction. Despite the lack of species‐specific effects of grass competition, the presence of grass suppressed fireweed’s foliar, root and whole plant biomass the most when herbivory was absent. With herbivory, fireweed did not suffer from any measurable competitive suppression. This lack of competitive suppression may be due to an induced allelopathic response, given the levels of pyrrolizidine alkaloids common in many Senecio species. Since this result may weaken the case for biocontrol, the weed’s competitive responses should be verified in relation to actual insect herbivory.

<em>Senecio carhuanishoensis</em> H.Beltrán & J.Calvo sp. nov. (<em>Asteraceae, Senecioneae</em>), a new species from central Peru

A new species of Senecio L. from the central Andes of Peru, S. carhuanishoensis H.Beltrán & J.Calvo sp. nov., only known from the Laraos District (Yauyos, Lima), is described and illustrated. It is a suffrutescent, rupicolous plant with the stems rather appressed to the rocks. It is characterized by its greyish-lanate indumentum covering the stem, leaves, and involucre, by having leaves oblanceolate to oblong, short-pedunculate, terminal, solitary, discoid capitula, and by displaying short glandular trichomes between the throat and the tube of the florets. It strictly grows in limestone rock crevices. Its morphology is compared with those of S. evacoides Sch.Bip. and S. ishcaivilcanus Cuatrec.

Análisis micromorfológico de Senecio subserie Polyphylli (Senecioneae, Asteraceae)

A micromorphological study of the species of Senecio subseries Polyphylli is presented. Vegetative (leaf trichomes) and reproductive characters (phyllary and achene trichomes; middle vein of the tubulose corolla teeth; anther collars, anther bases, and connectival appendages; pollen; style branches; achenes) are analyzed. A key based on microcharacters for the identification of the species is presented

Three new caespitose species of Senecio (Senecioneae, Compositae) from Central Andes

Three new species of Senecio belonging to the group of discoid caespitose species are described from the high Andes of Bolivia. One of them is also recorded from southern Peru. Special emphasis is placed on the color of the anthers, style-branches, and corollas, which are useful characters that were undervalued in previous taxonomic treatments dealing with this species assemblage. The three species are illustrated and pictures of living plants are included when available.

Experimental poisoning in broiler chickens by Senecio vernonioides, Senecio conyzaefolius and Senecio paulensis

ABSTRACT: Plants of the genus Senecio sp. are known to produce hepatic lesions in different animal species, including man. To evaluate the toxicity of three species of Senecio found in regions where cattle are bred in the state of Santa Catarina, experiments were conducted on broiler chickens (Gallus domesticus). Green leaves of S. conyzaefolius, S. vernonioides and S. paulensis were collected and dried in the shade. After drying, the leaves were ground, mixed into the feed and fed to the chickens divided into 3 groups. Group 1 and Group 2 received single doses of 5g/kg and 20g/kg, respectively. Group 3 was given daily doses of 1g/kg for 20 days (values corresponding to green plant) and Group 4 (control) received free feed of the plant. For each group, five chickens were submitted to necropsy at 30 days and five to 60 days after planting, and five chickens that consumed S. vernonioides and S. conyzaefolius at the dose of 1g/kg for 20 days were necropsied at 90 days after the beginning of the experiment. Macroscopic lesions were observed in chickens that consumed S. vernonioides at a dose of 1 g/kg for 20 days in birds necropsied at 30, 60 and 90 days and were characterized mainly by liver of firm consistency, diminished in size with yellowish coloration and evident lobular pattern, ascites and hydropericardium. In microscopy the main lesions observed were megalocytosis, hepatocyte swelling, fibrosis and biliary hyperplasia and were more intense at the dosage of 1 g/kg for 20 days for S. vernonioides and less severe in the chickens that ingested S. conyzaefolius. The chickens that received S. paulensis showed no macroscopic and microscopic lesions.

Poisoning of cattle by Senecio spp. in Brazil: a review

ABSTRACT: Poisoning of cattle by plants of the Senecio genus represents an important cause of death in cattle and has important economic repercussions in southern Brazil. This review is intended to provide a detailed review of Senecio spp. intoxication in cattle and addresses issues regarding the toxic principle and pathogenesis of the disease caused by these plants and the epidemiology, clinical signs, diagnosis, control and prophylaxis of the disease. Senecio brasiliensis is the main species associated with natural intoxication of livestock in Brazil, and the number of cases associated with the ingestion of S. madagascariensis is increasing. The toxic principle of Senecio spp. comprises the hepatotoxic alkaloids of the pyrrolizidine group (pyrrolizidine alkaloids, PAs). The resulting liver lesions are chronic and irreversible and result from the inhibition of hepatocellular mitosis. Deaths of adult cattle may occur both sporadically and in larger outbreaks over an extended period of time. In cattle raising, Senecio spp. are consumed mainly during the winter, when there is a dearth of forage; at this time the poisonous Senecio species are budding and contain high concentrations of PAs. Spontaneous Senecio spp. intoxication in cattle is a chronic condition that frequently involves acute clinical manifestations. Affected cattle may present ascites, emaciation, intermittent dark diarrhea, tenesmus, rectal prolapse, and neurological signs resulting from hepatic encephalopathy. Hepatogenous photosensitization may be observed but is uncommon. Necropsy findings include dependent subcutaneous edema, ascites, and edema of the mesentery, abomasal folds, and gallbladder. The liver is firm, normal or reduced in size with a white, thick capsule. Microscopically, the hallmarks of Senecio-associated disease are varying degrees of hepatocellular megalocytosis, bile duct hyperplasia and fibrosis. Sheep are significantly more resistant to Senecio intoxication than are cattle and avidly ingest Senecio plants; therefore, the use of sheep for grazing infested pasture is recommended for preventing the associated disease in cattle.

Hybridisation and detection of a hybrid zone between mesic and desert ragworts (Senecio) across an aridity gradient in the eastern Mediterranean

ABSTRACTBackground: Hybrid zones provide excellent opportunities for studying plant adaptation and speciation.Aims: We tested whether two herbaceous species of Senecio, S. vernalis and S. glaucus, hybridise in the eastern Mediterranean region and form a hybrid zone across an aridity gradient in the Jordan Rift Valley.Methods: Allozyme variation surveyed across both species was analysed by the programme STRUCTURE to assign individuals to genetic groups and determine levels of admixture. Populations in the Jordan Rift Valley were subsequently subjected to a cline analysis.Results: STRUCTURE showed that interspecific hybrids were produced at low frequency along the Israeli coastal plain where S. glaucus is represented by ssp. glaucus. In contrast, hybrids were more commonly produced in central populations of the Jordan Rift Valley. Here, the two species form a hybrid zone with S. vernalis occurring in mesic sites to the north and S. glaucus (ssp. coronopifolius) in arid sites to the south. Cline analysis showed that the hybrid zone is centred towards the northern end of the Dead Sea, but the analysis failed to distinguish how it is maintained.Conclusions: Future detailed genetic and ecological analysis of the Senecio hybrid zone should improve our understanding of plant adaptation and speciation across aridity gradients.

Three new species of Senecio (Compositae: Senecioneae) from the Alto Marañón, Huánuco region, Central Peru

Three new species of Senecio (Compositae: Senecioneae) from Central Peru are described and illustrated. Morphological characters are used in order to distinguish them from the closest species. Senecio crassiandinus Montesinos & Pino has succulent leaves with cuticle composed of translucid white glands, bright yellow disc florets with blotches of pale reddish-brown in the corolla throat and linear-oblong achenes covered with trichomes, which distinguish it from the other South American species of the genus. Senecio inghamii Montesinos has oblanceolate-ovate to rhombic-quadrate leaves, short-sized, with serrate-quadrate dentation, upper surface lustrous and glossy, lower surface densely covered with whitish lanuginose pubescence, capitules bear trilobulated ray florets, achenes copiously covered by fimbriate hairs which differentiates it from its closest relative, S. pensilis Greenm. Senecio roseoandinus Montesinos & R. Zárate is a unique pubescent species characterized for being a perennial rhizomatous herb, with lanuginose and arachnoid trichomes, leaves elliptic-lanceolate, thick, densely arachnoid to glabrous (lustrous, glossy, dark green), margin entire to crenate, synflorescence in racemes, capitules discoid, corolla pale yellow but turning fuchsia-pink at maturity, achenes oblong, striate, and glabrous. All three new species are distributed in the Alto Marañon river mountain slopes, at altitudes ranging from 2000 up to 4200 m a.s.l. The species are, so far, only known from their type localities in the Huánuco region.

Molecular and morphological study of the genus Senecio L. (Asteraceae: Senecioneae) in Iran

The genus Senecio (Asteraceae, Senecioneae) with about 1250 species is one of the largest genera in the family. Due to historical and present time inter-specific hybridization and reticulate evolution in the genus, the morphological and molecular phylogenetic evolution are disjunct. The genus contains 17 species belonging to four sections, sect. Crociseris, sect. Quadridentati, sect. Jacobaea and sect. Senecio, in Iran out of which, six are endemic. Therefore, the present study was performed with the aim to provide data on the above issues. In general, ISSR molecular markers could delimit the studied Senecio species and revealed the species relationships, but did not support any of the sections. The ITS and cp-DNA sequencing of six species of S. iranicus, S. vulcanicus, S. kotschyanus, S. paulsenii subsp. khorasanicus and S. joharchii were obtained for the first time. S-DIVA suggests three possible ancestral ranges, of Kordestan (A), Mazandaran (G), and West-Azarbayejan (D), for Sececio species in Iran. These areas are located in the western parts of Iran. Mazandaran province played important role in the speciation process that led to the formation of endemic Sececio species in the country, while, Kordestan and West-Azarbayejan are the main road for the entrance of Sececio species from Europe via neighboring countries. The morphological characters used could also delimit the four sections of the genus Senecio. However, ISSR, cp-DNA and nuclear genes sequences-based phylogenetic trees portrayed the species relationship much different from that of morphological dendrogram.

Stem and leaf anatomy and achene structure in some species of Senecio (Asteraceae)

The genus Senecio L. belongs to the tribe Senecioneae Cass. of the family Asteraceae which is the richest plant family of Turkey in terms of endemic species. The study was conducted on a total of 8 taxa belonging to Senecio. 4 taxa were collected from West and 4 were collected from East Anatolia. Stem and leaf anatomy of the taxa were studied by light microscopy; achene structure was examined by light microscopy and transmission electron microscopy in order to identify morphological, anatomical and histological modifications and resolve taxonomic problems of the genus.

Morphology and Anatomy Support a Reclassification of the African Succulent Taxa of Senecio S.L. (Asteraceae: Senecioneae)

Morphological and anatomical plant traits provide important characters for plant identification, and provide vital information to support classification systems based on molecular phylogenetic studies. The tribe Senecioneae (Asteraceae: Asteroideae) has recently been reclassified as a result of molecular phylogenetic investigations, and species with succulent leaves have been identified in several different clades of the tribe. We study the leaf morphology and anatomy of 20 selected species of Senecio s.l., embracing representatives of all distinct groups of leaf succulents in Senecioneae, and contrast the results with a molecular phylogeny derived from ITS sequence data. The leaves of the studied species vary as to their gross appearance (flat to terete, horizontally or seemingly vertically oriented, with or without ‘window’ areas) as well as with respect to their macro-anatomy (tissue succulence vs. all-cell succulence). The morphological and anatomical characterizations of identified groups correlate well with the clades found in the ITS-based molecular phylogenetic studies, and the reclassification of succulent-leaved species of Senecio s.l. into the segregate genera Caputia, Kleinia and Curio is strongly supported. Leaf characters provide easy-to-observe diagnostic characters to recognize the three genera.

Eremophilanes and Pyrrolizidine Alkaloids of Senecioneae Species

The chemical study of two species of the tribe Senecioneae afforded two eremophilanes and two pyrrolizidine alkaloids from Senecio subauriculatus and four modified eremophilanes from Roldana oaxacana. The chemistry of these species is in accord with that reported for species of Senecio and Roldana studied so far, and therefore, with the already described for the tribe Senecioneae.

Pyrrolizidine alkaloid variation in Senecio vulgaris populations from native and invasive ranges.

Biological invasion is regarded as one of the greatest environmental problems facilitated by globalization. Some hypotheses about the invasive mechanisms of alien invasive plants consider the plant–herbivore interaction and the role of plant defense in this interaction. For example, the “Shift Defense Hypothesis” (SDH) argues that introduced plants evolve higher levels of qualitative defense chemicals and decreased levels of quantitative defense, as they are released of the selective pressures from specialist herbivores but still face attack from generalists. Common groundsel (Senecio vulgaris), originating from Europe, is a cosmopolitan invasive plant in temperate regions. As in other Senecio species, S. vulgaris contains pyrrolizidine alkaloids (PAs) as characteristic qualitative defense compounds. In this study, S. vulgaris plants originating from native and invasive ranges (Europe and China, respectively) were grown under identical conditions and harvested upon flowering. PA composition and concentration in shoot and root samples were determined using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS). We investigated the differences between native and invasive S. vulgaris populations with regard to quantitative and qualitative variation of PAs. We identified 20 PAs, among which senecionine, senecionine N-oxide, integerrimine N-oxide and seneciphylline N-oxide were dominant in the roots. In the shoots, in addition to the 4 PAs dominant in roots, retrorsine N-oxide, spartioidine N-oxide and 2 non-identified PAs were also prevalent. The roots possessed a lower PA diversity but a higher total PA concentration than the shoots. Most individual PAs as well as the total PA concentration were strongly positively correlated between the roots and shoots. Both native and invasive S. vulgaris populations shared the pattern described above. However, there was a slight trend indicating lower PA diversity and lower total PA concentration in invasive S. vulgaris populations than native populations, which is not consistent with the prediction of SDH.