Lactucinae

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Distribution

Africa: Algeria (Algerianative); Angola (Angolanative); Azores (Açôresnative); Benin (Beninnative); Botswana (Botswanaintroduced); Burkina (Burkinanative); Burundi (Burundinative); Cameroon (Cameroonnative); Canary Is. (Canary Is.native); Cape Provinces (Eastern Cape Provincenative, Northern Cape Provincenative, Western Cape Provincenative); Central African Republic (Central African Republicnative); Chad (Chadnative); Comoros (Comorosnative); Congo (Congonative); Djibouti (Djiboutinative); Egypt (Egyptnative); Equatorial Guinea (Equatorial Guineanative); Eritrea (Eritreanative); Ethiopia (Ethiopianative); Free State (Free Statenative); Ghana (Ghananative); Guinea (Guineanative); Gulf of Guinea Is. (Biokonative); Ivory Coast (Ivory Coastnative); Kenya (Kenyanative); KwaZulu-Natal (KwaZulu-Natalnative); Lesotho (Lesothonative); Liberia (Liberianative); Libya (Libyanative); Madagascar (Madagascarnative); Madeira (Madeiranative); Malawi (Malawinative); Mali (Malinative); Mauritius (Mauritiusnative); Morocconative; Mozambique (Mozambiquenative); Namibia (Namibianative); Niger (Nigernative); Nigeria (Nigerianative); Northern Provinces (Gautengnative, Mpumalanganative, North-West Provincenative, Northern Provincenative); Rodrigues (Rodriguesnative); Rwanda (Rwandanative); Réunion (Réunionnative); Seychelles (Seychellesintroduced); Sierra Leone (Sierra Leonenative); Somalia (Somalianative); Sudan (Sudannative); Swaziland (Swazilandnative); Tanzania (Tanzanianative); Tunisia (Tunisianative); Uganda (Ugandanative); Zaire (Zairenative); Zambia (Zambianative); Zimbabwe (Zimbabwenative) Asia-Temperate: Afghanistan (Afghanistannative); Altay (Altaynative); Amur (Amurnative); Buryatiya (Buryatiyanative); China North-Central (Gansunative, Hebeinative, Shaanxinative, Shandongnative, Shanxinative); China South-Central (Chongqingnative, Guizhounative, Hubeinative, Sichuannative, Yunnannative); China Southeast (Anhuinative, Fujiannative, Guangdongnative, Guangxinative, Henannative, Hunannative, Jiangsunative, Jiangxinative, Zhejiangnative); Chita (Chitanative); Cyprus (Cyprusnative); East Aegean Is. (East Aegean Is.native); Gulf States (United Arab Emiratesnative); Hainan (Hainannative); Inner Mongolia (Nei Mongolnative, Ningxianative); Iran (Irannative); Iraq (Iraqnative); Irkutsk (Irkutsknative); Japannative (Hokkaidonative, Honshunative, Kyushunative, Shikokunative); Kamchatka (Kamchatkanative); Kazakhstan (Kazakhstannative); Khabarovsk (Khabarovsknative); Kirgizistan (Kirgizistannative); Korea (North Koreanative, South Koreanative); Krasnoyarsk (Krasnoyarsknative); Kuril Is. (Kuril Is.native); Lebanon-Syria (Lebanonnative, Syrianative); Magadan (Magadannative); Manchuria (Heilongjiangnative, Jilinnative, Liaoningnative); Mongolia (Mongolianative); Nansei-shoto (Nansei-shotonative); North Caucasusnative (Chechnyanative, Dagestannative, Kabardino-Balkariyanative, Karacheyevo-Cherkessiyanative, Krasnodarnative, Severo-Osetiyanative, Stavropolnative); Ogasawara-shoto (Ogasawara-shotonative: doubtfully native); Oman (Omannative); Palestine (Israelnative, Jordannative); Primorye (Primoryenative); Qinghai (Qinghainative); Sakhalinnative (Sakhalinnative); Saudi Arabia (Saudi Arabianative); Sinai (Sinainative); Tadzhikistan (Tadzhikistannative); Taiwan (Taiwannative); Tibet (Tibetnative); Transcaucasus (Abkhaziyanative, Adzhariyanative, Armenianative, Azerbaijannative, Georgianative, Nakhichevannative); Turkey (Turkeynative); Turkmenistan (Turkmenistannative); Tuva (Tuvanative); Uzbekistan (Uzbekistannative); West Siberia (West Siberianative); Xinjiang (Xinjiangnative); Yakutskiya (Yakutskiyanative); Yemen (North Yemennative, South Yemennative) Asia-Tropical: Assam (Assamnative, Manipurnative, Meghalayanative, Mizoramnative, Nagalandnative); East Himalaya (Arunachal Pradeshnative, Bhutannative, Darjilingnative, Sikkimnative); India (Delhinative, Haryananative, Keralanative, Madhya Pradeshnative, Punjabnative, Rajasthannative, Tamil Nadunative, Uttar Pradeshnative, West Bengalnative); Jawa (Jawanative); Laosnative; Malaya (Peninsular Malaysianative: doubtfully native); Myanmar (Myanmarnative); Nepal (Nepalnative); New Guinea (Irian Jayanative, Papua New Guineanative); Pakistan (Pakistannative); Philippines (Philippinesnative); Sumatera (Sumateranative: doubtfully native); Thailand (Thailandnative); Vietnam (Vietnamnative); West Himalaya (Himachal Pradeshnative, Jammu-Kashmirnative, Uttaranchalnative) Australasia: New South Wales (Australian Capital Territoryintroduced: naturalized, New South Walesintroduced: naturalized); New Zealand North (New Zealand Northintroduced); New Zealand South (New Zealand Southintroduced); Northern Territory (Northern Territoryintroduced); Queensland (Queenslandintroduced); South Australia (South Australiaintroduced); Tasmania (Tasmaniaintroduced: naturalized); Victoria (Victoriaintroduced: naturalized); Western Australia (Ashmore-Cartier Is.introduced, Western Australiaintroduced) Europe: Albania (Albanianative); Austrianative (Austrianative, Liechtensteinnative); Baleares (Balearesnative); Baltic States (Estonianative, Kaliningradnative, Latvianative, Lithuanianative); Belarus (Belarusnative); Belgiumnative (Belgiumnative, Luxembourgnative); Bulgaria (Bulgarianative); Central European Russia (Central European Russianative); Corse (Corsenative); Czechoslovakia (Czech Republicnative, Slovakianative); Denmark (Denmarknative); East European Russia (East European Russianative); Finland (Finlandnative); Francenative; Germany (Germanynative); Great Britain (Great Britainnative); Greece (Greecenative); Hungary (Hungarynative); Irelandintroduced (Irelandintroduced: naturalized, Northern Irelandintroduced: naturalized); Italynative; Kriti (Kritinative); Krym (Krymnative); Netherlands (Netherlandsnative); North European Russia (North European Russianative); Northwest European Russia (Northwest European Russianative); Norway (Norwaynative); Poland (Polandnative); Portugal (Portugalnative); Romania (Romanianative); Sardegna (Sardegnanative); Sicilynative (Maltanative, Sicilynative); South European Russia (South European Russianative); Spainnative (Andorranative, Gibraltarnative, Spainnative); Sweden (Swedennative); Switzerland (Switzerlandnative); Turkey-in-Europe (Turkey-in-Europenative); Ukraine (Moldovanative, Ukrainenative); Yugoslavia (Bosnia-Herzegovinanative, Croatianative, Macedonianative, Montenegronative, Serbianative, Slovenianative) Northern America: Alabama (Alabamanative); Alaska (Alaskanative); Alberta (Albertanative); Arizona (Arizonanative); Arkansas (Arkansasnative); British Columbia (British Columbianative); California (Californianative); Colorado (Coloradonative); Connecticut (Connecticutnative); Delaware (Delawarenative); District of Columbia (District of Columbianative); Florida (Floridanative); Georgia, U.S.A. (Georgia, U.S.A.native); Idaho (Idahonative); Illinois (Illinoisnative); Indiana (Indiananative); Iowa (Iowanative); Kansas (Kansasnative); Kentucky (Kentuckynative); Labrador (Labradornative); Louisiana (Louisiananative); Maine (Mainenative); Manitoba (Manitobanative); Maryland (Marylandnative); Massachusetts (Massachusettsnative); Mexico Central (Mexico Distrito Federalintroduced, México Stateintroduced, Pueblanative); Mexico Gulf (Veracruznative); Mexico Northeast (Chihuahuanative, Coahuilanative, Guanajuatointroduced, Hidalgonative, Nuevo Leónnative, Querétarointroduced, San Luis Potosínative, Tamaulipasnative); Mexico Northwest (Baja Californiaintroduced, Sonoraintroduced); Mexico Southeast (Chiapasnative); Mexico Southwest (Michoacánnative, Oaxacanative); Michigan (Michigannative); Minnesota (Minnesotanative); Mississippi (Mississippinative); Missouri (Missourinative); Montana (Montananative); Nebraska (Nebraskanative); Nevada (Nevadanative); New Brunswick (New Brunswicknative); New Hampshire (New Hampshirenative); New Jersey (New Jerseynative); New Mexico (New Mexiconative); New York (New Yorknative); Newfoundland (Newfoundlandnative, St.Pierre-Miquelonnative); North Carolina (North Carolinanative); North Dakota (North Dakotanative); Northwest Territories (Northwest Territoriesnative); Nova Scotia (Nova Scotianative); Ohio (Ohionative); Oklahoma (Oklahomanative); Ontario (Ontarionative); Oregon (Oregonnative); Pennsylvania (Pennsylvanianative); Prince Edward I. (Prince Edward I.native); Québec (Québecnative); Rhode I. (Rhode I.native); Saskatchewan (Saskatchewannative); South Carolina (South Carolinanative); South Dakota (South Dakotanative); Tennessee (Tennesseenative); Texas (Texasnative); Utah (Utahnative); Vermont (Vermontnative); Virginia (Virginianative); Washington (Washingtonnative); West Virginia (West Virginianative); Wisconsin (Wisconsinnative); Wyoming (Wyomingnative); Yukon (Yukonintroduced) Southern America: Argentina Northeast (Argentina Distrito Federalintroduced, Buenos Airesintroduced, Chacointroduced, Corrientesintroduced, Córdobaintroduced, Entre Ríosintroduced, La Pampaintroduced); Argentina Northwest (Catamarcaintroduced, Jujuyintroduced, La Riojaintroduced, Mendozaintroduced, San Juanintroduced, San Luisintroduced); Argentina South (Chubutintroduced, Neuquénintroduced, Rio Negrointroduced, Santa Féintroduced); Bahamas (Bahamasnative); Brazil South (Rio Grande do Sulintroduced, Santa Catarinaintroduced); Chile Central (Biobíointroduced, Coquimbointroduced, La Araucaniaintroduced, Mauleintroduced, O'Higginsintroduced, Santiagointroduced, Valparaísointroduced); Chile North (Antofagastaintroduced, Tarapacaintroduced); Cuba (Cubaintroduced); Dominican Republic (Dominican Republicnative); Ecuador (Ecuadorintroduced); Galápagos (Galápagosnative); Guatemala (Guatemalanative); Haiti (Haitinative); Hondurasintroduced; Jamaica (Jamaicanative); Leeward Is. (British Virgin Is.native); Paraguay (Paraguayintroduced); Puerto Rico (Puerto Riconative); Uruguay (Uruguayintroduced)

Systematics

The Lactucinae comprise about 200 species, distributed in Europe, Africa, Asia and North America (Kilian & al. 2017) and have a preference of montane habitats. The subtribe has two centres of diversity, one in the Mediterranean-SW Asian region, the second in the Sino-Himalayan region. Many species are mesic tall forbs, others are perennial herbs of other kinds, among them being the only scandent herbs found in the tribe, or rosette herbs and acaulescent herbs; more rarely they are xeric subshrubs and annual herbs (Wang & al. 2013). The subtribe constitutes a lineage within the larger of the two core groups of the tribe (Kilian & al. 2009; Tremetsberger & al. 2012; Kilian & al. 2017a).

During the 19th and 20th centrury, the Lactucinae were not usually recognised as a separate subtribe but its members were placed in a large subtribe Crepidinae or a corresponding group (Hoffmann 1899–94; Stebbins 1953; Jeffrey 1966). This changed only towards the end of the 20th century, when a morphological phylogenetic analysis by Bremer (1994) revealed the Crepidinae s.l. to be polyphyletic and the Lactucinae, Crepidinae s.str. and Sonchinae to constitute separate lineages. These were corroborated by phylogenies based on chloroplast DNA restriction site variation (Whitton & al. 1995), nrITS (Kilian & al. 2009; Tremetsberger & al. 2012; Kilian & al. 2017a) and non-coding plastid DNA loci (Kilian & al. 2017a).

Compared to the circumscription of the Lactucinae by Bremer (1994), which was largely maintained by Lack (2006), Kilian & al. (2009) excluded from subtribe Lactucinae four genera inferred from their nrITS phylogeny: (1) Nabalus s.l., which is clearly separated from Prenanthes s.str. and nested in the Crepidinae with an affinity to Soroseris; (2) Syncalathium, which in the sense of the type of its name S. kawaguchii is a member of the Crepidinae also with an affinity to Soroseris, a result supported by karyological (Zhang & al. 2007, 2009), palynological (Blackmore & Persson 1996) and further molecular (Zhang & al. 2011a, b) analyses; (3) Prenanthes, in the sense of the type of its name P. purpurea and thus as a monospecific genus, which was surprisingly found allied in nrITS phylogenies with subtribe Hypochaeridinae; (4) Faberia, but based on morphological data only.

Extensive molecular phylogenetic studies of the Lactucinae based on nrITS and five non-coding plastid DNA loci by Wang & al. (2013), focussing on the Sino-Himalayan centre of diversity, and by Kilian & al. (2017a), covering all species groups on a global scale, provided new insights into the circumscription of the subtribe. Accordingly, the redelimited monophyletic core of the Lactucinae is composed of seven lineages that also include Prenanthes, which is confirmed to have a single species, P. purpurea:

(1) Prenanthes lineage: Kilian & al. (2017a) confirmed the exclusion of the last potential congeners from Prenanthes (the Caucasian P. abietina, the North American species placed into Prenanthes or Nabalus, the scandent Prenanthes species of Sumatra and Java, the scandent tropical African P. subpeltata) and hence the assumption by Kilian & Gemeinholzer (2007), Kilian & al. (2009) and Wang & al. (2013) that P. purpurea forms an isolated lineage of the Lactucinae of its own. P. purpurea is resolved by Kilian & al. (2017a) as sister to the other six lineages of the Lactucinae in both the nrITS and plastid DNA phylogenies. Earlier findings of an affinity of Prenanthes with the Hypochaeridinae in ITS phylogenies seem to be due to long branch attraction in scarce samplings.

(2) Cicerbita lineage: The lineage consists of two sister clades: one includes the widespread European C. alpina, providing the type of the generic name Cicerbita, the Balkan endemic C. pancicii and the Caucasian-Turkish C. petiolata. The other has two subclades, one represented by Mycelis muralis, the second by a few closely related and partly doubtfully distinct, chiefly SW Asian species of Cephalorrhynchus in the sense of its type, among them the SE European–SW Asian C. hispidus.

(3)-(4) Notoseris and Paraprenanthes lineages: These include the respective near-endemic Chinese genera in the revised circumscription by Wang & al. (2013). In contrast to the nrITS phylogeny, the two lineages are resolved as a single clade in the plastid DNA phylogeny by Wang & al. (2012) and Kilian & al. (2017a).

(5) Kovalevskiella lineage: First recognised and provisionally referred to as “Cicerbita II lineage” by Wang & al. (2013), this chiefly Central Asian lineage includes, among others, three of the six species of the genus Kovalevskiella, including K. zeravschanica, which provides the type of that generic name. The other three species of the genus are nested in the Melanoseris lineage.

(6) Melanoseris lineage: Recognised by Wang & al. (2013) as the genus Melanoseris (as revived by Shih & Kilian in Shih & al. 2011), this lineage unites the Sino-Himalayan genera Chaetoseris and Stenoseris with a number of species of the same region formerly asigned to genera such as Prenanthes, Mulgedium, Cephalorrhynchus, Cicerbita and Lactuca. The monospecific near-endemic Chinese genus Parasyncalathium is also deeply nested in the Melanoseris lineage. Kilian & al. (2017a) show that besides the Sino-Himalayan clade of Melanoseris, which is formed by these taxa and extends to SE Asia, Sumatra and Java, this sizable lineage moreover includes a SW Asian clade (with e.g. Steptorhamphus, typified by S. crambifolius) and a tropical African clade (for the latter see also Wei & al. 2015).

(7) Lactuca lineage: It includes the genus Lactuca and the former segregates Lactucella (typified by L. undulata ≡ Lactuca undulata), Lagedium (typified by L. sibiricum ≡ Lactuca sibirica), Mulgedium (typified by M. runcinatum = Lactuca tatarica), Pterocypsela (typified by P. indica ≡ Lactuca indica), Scariola (typified by S. viminea ≡ Lactuca viminea).

Two further lineages shift between Lactucinae and Crepidinae in the nuclear and plastid DNA phylogenies:

(8) Faberia lineage: This lineage is allied to the Lactucinae in the nuclear phylogeny but nested in the subtribe Crepidinae in the pastid DNA phylogeny. This corresponds to the karyological evidence that the genus is alloploid with a chromosome number of 2n = 34 (Liu & al. 2012; Liu & Ren 2013), and thus most likely result of reticulate evolution involving a maternal ancestor from the Crepidinae and a paternal ancestor from the Lactucinae. Whether the nuclear or plastid DNA phylogeny provide the better estimate for the taxon phylogeny is an open question, because morphology appears little decisive in this case. Wang & al. (2013) preferred to follow the nuclear phylogeny and maintained Faberia as a member of the Lactucinae, a decision which is followed here.

(9) Astartoseris lineage: Like Faberia this monospecifc lineage endemic to Cyprus and Lebanon is nested in the Lactucinae in the nuclear phylogeny but in the Crepidinae in the pastid DNA phylogeny (Kilian & al. 2017a, b). In contrast to Faberia the taxon is diploid with a chromosome number of 2n = 18. Morphologically it is somehow intermediate between the Lactucinae and Crepidinae: showing Lactucinae feature in particular in capitula morphology and flower colour, the achene ribbing pattern is of a type characteristic of the Crepidinae (Kilian & al. 2017b). It is an early diverging orphan lineage of the Lactucinae in the nuclear phylogeny and has been classified as a genus of its own by Kilian & al. (2017b).

Kilian & al. (2017a), summarising the findings from their phylogenetic analyses, molecular clock dating and ancestral area estimations, hypothesise an origin of the Lactucinae in the SW Asian-European region between Tethys Sea and Paratethys (the sub-Paratethys region) during the second half of the Early Miocene (c. 18–19 mya). The start of its diversification is estimated to have taken place with the beginning of the Middle Miocene (c. 16–17 mya) and diversification of the core Lactucinae to have started then at least around 12–13 mya following the Middle Miocene decline in temperature, coupled with an eastward migration through Asia. One sublineage of the Melanoseris lineage took the route into tropical E Africa after the final closure of the Tethys in the east and after Late Miocene orogeny had created a suitable corridor. Still other lineages expanded westward.

The crucial problem with the lineages of the subtribe revealed in the molecular phylogenetic reconstruction, is, however, that the apparent morphological differences between the lineages are very vage, while at the same time often species of one lineage show more similarity with species of other lineages than with some of the same lineage. No morphological synapomorphies for the molecular lineages are evident currently. Sennikov (in Lazkov & al. 2014) correctly stated that this "may be explained by the rapid diversification of this group in its evolutionary history, similarly to what had been concluded for the subdivision of the Cichorieae at the level of subtribe (Tremetsberger et al. 2013)". Sennikov (in Lazkov & al. 2014) therefore proposed a very wide circumscription of Lactuca, lumbing all genera of the core Lactucinae under Lactuca. Kilian & al (2017a) state that the translation of the phylogenetic reconstruction of the Lactucinae into a natural but nevertheless practicable classification is still work in progress. This generic classification shall recognise monophyletic as well as diagnosable entities and be based on the knowledge about character evolution in the group.

For the time being, taxonomy of the subtribe inevitablely remains provisional, not the least since also the molecular phylogenies show considerable incongruences. The classification here consequently is work in progress and in principal guided by the nrITS phylogeny. In several cases thus lineages resolved are shown rather than taxonomic entities.

References


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Zhang J.-W., Nie Z. N., Wen J. & Sun H. 2011: Molecular phylogeny and biogeography of three closely related genera, Soroseris, Stebbinsia, and Syncalathium (Asteraceae, Cichorieae), endemic to the Tibetan Plateau, SW China. – Taxon 60: 15–26. // ➪ //

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