Abstract: Background and Objective: Verbesina encelioides (Cav.) Benth. and Hook. belongs to the family Asteraceae, growing in roadsides and waste places, it was previously recorded as a new addition to the flora of Libya at the generic and species level without determining its infraspecies status. The aim of this study was to determine infraspecies status of this species. Materials and Methods: The plant is reported to be widely distributed in Tripoli as roadside, waste places, garden species and in disturbed habitats. Flowering and fruiting specimens of V. encelioides were collected from many places in Tripoli and brought to the herbarium of the Department of Botany, Faculty of Sciences, University of Tripoli and subjected to detailed morphological examination, which confirmed that it is belongs to subsp. encelioides. Results: The finding of this study is adds a new taxon to the flora of Libya. Information about its morphological features, biology, ecology, distribution and invasiveness were provided. Conclusion: In this study, Verbesina encelioides subspecies encelioides is discovered and recorded in the flora of Libya, which is previously identified and recorded at species level without determining the infraspecies identity, therefore this finding is significant to taxonomists and readers because it adds a new taxon to the flora of Libya.
INTRODUCTION
The family Asteraceae in the Libyan flora comprises 97 genera and 237-240 species1,2 However, there were no herbarium or literature data of the genus Verbesina in Libya. This genus is the largest one in the tribe Heliantheae, which contains about 300 worldwide species of herbs, shrubs and trees, ranging from Eastern Canada to central Argentina3. It is reportedly divided into 12 sections, using characters such as corolla color, inflorescence morphology, capitulum size and ray flowers presence4.
V. encelioides is a member of the tribe Heliantheae and section Ximenesia5. It was divided into 2 subspecies (encelioides and exauriculata)6. The native range of Verbesina encelioides is generally North and South America, specifically Mexico and the southwestern United States of Texas, Arizona7-11. However, it should be pointed out that there exist some discrepancies as to the true native range of V. encelioides. Researcher suggests the native range also includes Montana, while the United States Geological Survey lists and describes V. encelioides on its webpage for “Native Wildflowers of the North Dakota Grasslands9. Panero and Jansen3 studies support a North American origin for this genus.
It is a drought tolerant and well adapted invasive species and has successfully naturalized in many warm regions of the world. Its current world distribution includes the 5 continents of America (Argentina, Arizona, Hawaii, Mexico), Africa (Algeria, Egypt, Morocco, Tunisia), Asia (India, Saudi Arabia, Yemen), Europe (Belgium, France, Spain) and Oceania (Australia, Victoria)12.
For Europe, Hansen13 reported its presence as doubtful in Germany, Sweden and Switzerland, while EPPO sources indicate it from Denmark, Spain, UK and Austria14,15.
The way and time of its introduction and arrival to Libya remain unknown. However, Sharashy16 recorded Verbesina encelioides as a new record to the flora of Libya without determining its infraspecies status, therefore, the present paper introduces infraspecies status of our collected specimens as subsp encelioides.
MATERIALS AND METHODS
The plant is widespread in Tripoli as a roadside and waste places plant, it was monitored from March-October, 2019, specimens were collected many times from many places in Tripoli within this period (Fig. 1 and 2).
| Fig. 1: | Verbesina encelioides, habit |
| Fig. 2: | Verbesina encelioides, heads |
The collected specimens were brought to the herbarium and subjected the ordinary herbarium techniques. Plant identification and authentication procedure were carried out at the national herbarium of botany department (ULT), Faculty of Science, University of Tripoli using the data from the following literatures7,8,15,17,18,20-24. The specimens were given a voucher number (76107981-NR) and deposited in the same herbarium.
DESCRIPTION OF SPECIES
Verbesina encilioides (Cav.) Benth. and Hook. subsp. encelioides.
Synonyms: Verbesina encelioides (Cav.) Benth. and Hook. f. ex A. Gray subsp. encelioides Ximenesia encelioides Cav.
| Fig. 3: | Verbesina encelioides, auricles |
| Fig. 4: | Verbesina encelioides, marginal achene |
Common names: Golden crownbeard, American dogweed, butter daisy, cowpen daisy, crown beard, crown-beard, crownbeard, gold weed, golden crown beard, golden crown daisy, golden crown-beard, skunk daisy, South African daisy, wild sunflower, yellow top.
Annual herbs are growing up to 150 cm high. Stems are densely short-hairy. Petioles winged, wings dilated at the base to form a pair of stipule-like auricles. Leaf blades lanceolate to triangular-ovate, up to 10×7 cm, 3-veined, with a coarsely dentate margin, covered with appressed fine hairs especially on the lower surface, bases broadly cuneate to truncate, lower leaves are opposite and triangular, while the upper leaves are alternate and lanceolate.
| Fig. 5: | Verbesina encelioides, central achene |
Peduncle subtended by leaf-like bracts. Heads are 2.5-5 cm in diameter, solitary at ends of long peduncles or in clusters of 2-3, paleaceous and involucres bracts 1-2 series, 7-15 mm long, linear-lanceolate to linear, appressed greyish hairy. Palea is 6-8 mm, linear, abruptly acuminate. Ray flowers 10-15/head, yellow, pistillate, rays elliptic-ovate, 1-2 cm long, 3-toothed at apex, disk flowers numerous, 8 mm long, yellow-orange, tubular, 5 toothed, hermaphrodite, achenes flattened, grayish brown, pubescent, with 2 apical long fine appendages 1-2 mm long, achenes of 2 types, marginal achenes sterile, oblong, not winged, 5-6.5 mm long, central achenes obovate, broadly winged, 7-10 mm long including wings25 (Fig. 1-5), 2n = 34.
Flowering time: From April-October.
RESULTS AND DISCUSSION
Verbesina encelioides (Cav.) Benth. and Hook. subspecies encelioides has been reported as a widespread weed in waste places and roadsides in many parts of Tripoli. It is easily recognized by its distinguishing characteristics include its opposite (below) and alternate (above) lanceolate to deltoid leaves with a grayish undersurface, winged petioles with ear shape auricles, flattened winged achenes, brightly colored yellow disk florets and large yellow ray florets (10-25 mm), which make the plant look like a small sunflower (Helianthus sp.)26,27. It can be differentiated from the garden sunflower (Helianthus annus L.) by its opposite leaves on the lower part of the plant and the substantially smaller heads and winged achenes17,24.
Sharashy16 was recorded this species for the first time in the flora Libya at the species level without determining its infraspecific status and he wasn’t determined whether his specimens belonged to subsp encelioides or exauriculata, while our specimens have been determined as a type subspecies encelioides which distinguished from subspecies exauriculata by ear-shaped auricles, outgrow on each side of the petiole base, semi-ovate and borne on most leaves and achene wing apices acute and phyllaries typically over 12 mm long5,28, while in subspecies exauriculata auricles oblong, not ear-shaped and mainly restricted to the petioles of upper leaves, achene wing apices obtuse and phyllaries average less than 12 mm long5,24.
V. encelioides figures on the European Plant Protection Organization (EPPO) observation list of Invasive Alien Plants29. It is regarded as a noxious weed in several states of the United States of America23. In particular, it is problematic for peanut farmers in southern states of the United States24. In Australia, it occurs as a weed of sandy loams along roadsides, stock routes and field headlands and in some woodland communities30. In North India, it is a prominent weed infesting field crops and abundant along roadsides and railway tracts and on the wastelands, occurring mostly in sandy and sandy-loam soils22. It was recently recorded in Morocco, where it colonizes wastelands, roadside borders and field crops31.
More recently V. encelioides subsp. encelioides was detected in Tunisia in 2011 from agricultural fields and along highway (A1: Tunis-Sfax) at Hencha-Sfax8.
The way of its introduction to Libya remains unknown, while in other countries there are reports regarding the introduction of seeds with wool or as contaminants in pasture hay or cereal grain14.
It is a drought tolerant erect annual plant, germinating by seeds in early spring or autumn with a main flowering peak from July to November. The plant grows better in disturbed and ruderal zones than in agricultural fields. In fact, however, the plant is easily dispersed and it is likely to establish elsewhere in the semi-arid region. Although Verbesina encelioides is a beautiful plant, local people do not use it as ornamental because of its unpleasant smell, in addition, it is a poisonous plant especially for livestock14. It can be considered as naturalized but with a high invasive potential favored by the dry climate and by the high proportion of areas with disturbed habitats which requires the implementation of an appropriate management plan, including quarantine and potential eradication.
Invasive attributes: A number of characteristics aid in the aggressive qualities of this plant including, ability to withstand drought, ability to handle a wide range of growing conditions, rapid growth, allelopathic effects on other plants, high seed production and dispersal ability, high periods of seed dormancy and high germination rates22,32.
CONCLUSION
In this study, Verbesina encelioides subspecies encelioides is discovered and recorded in the flora of Libya, which is previously identified and recorded at species level without determining the infraspecies identity, therefore this finding is significant to taxonomists and readers because it adds a new taxon to the flora of Libya.
SIGNIFICANCE STATEMENT
Our finding is very important due to its novelty and originality regarding the new record added in the flora of Libya and helps taxonomists to monitor the distribution and spread of this subspecies in Libya and its possible impact to the diversity and natural habitats in Libya.
ACKNOWLEDGMENT
The study was fully done by the authors without any assistance.