Diversification of Portulaca Oleracea L. Complex in the Italian Peninsula and Adjacent Islands†
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BOTANY LETTERS, 2016 http://dx.doi.org/10.1080/23818107.2016.1200482 Diversification of Portulaca oleracea L. complex in the Italian peninsula and adjacent islands† Avinoam Danina, Fabrizio Buldrinib,g, Marta Bandini Mazzantib, Giovanna Bosib, Maria Carmela Cariac, David Dandriad, Edwin Lanfrancoe, Stephen Mifsudf and Simonetta Bagellac aDepartment of Ecology, Evolution, and Behavior, The Alexander Silberman Institute, The Hebrew University of Jerusalem, Jerusalem, Israel; bOrto Botanico – Dipartimento di Scienze della Vita, Università degli Studi di Modena e Reggio Emilia, Modena, Italy; cDipartimento di Scienze della Natura e del Territorio, Università degli Studi di Sassari, Sassari, Italy; dDepartment of Biology, University of Malta, Msida, Malta; eDepartment of Biology & Institute of Earth Systems, University of Malta, Msida, Malta; fEcoGozo, Ministry for Gozo, Victoria, Gozo (Malta); gDipartimento di Scienze Biologiche, Geologiche e Ambientali, Università degli Studi di Bologna, Bologna, Italy ABSTRACT ARTICLE HISTORY There is an increasing interest in the taxonomy and distribution of the forms of the Portulaca Received 11 December 2015 oleracea complex. The information accruing from specimens collected in the Italian peninsula and Accepted 2 June 2016 surrounding islands (Sicily, Sardinia, Corsica and Malta) is here described. Eleven morphotypes KEYWORDS were recorded: ‘P. cypria’, ‘ P. granulatostellulata’, ‘ P. nitida’, ‘ P. oleracea’, ‘ P. papillatostellulata’, Corsica; Maltese Islands; ‘P. rausii’, ‘ P. sardoa’, ‘ P. sativa’, ‘ P. sicula’, ‘ P. trituberculata’, ‘ P. zaffranii’ and a still unclear form purslane; Sardinia; seed Portulaca oleracea f. Three occur in almost all the Italian peninsula and adjacent islands; three tegument; Sicily; Portulaca are scattered in the Italian peninsula and in the adjacent islands; the remnant have a distribution restricted to the islands such as Sicily and Sardinia. The morphotypes can be divided into two main categories: seeds smooth, without ornamentations; seeds with ornamentations. The morphotypes with ornamentations are more widespread than smooth ones, probably because seed ornamentations play an important role in seed dispersal, which is perhaps mainly anthropochorous given that P. oleracea is a synanthropic species that can tolerate mechanical disturbance. There are cases of multiple occurrence, as evidenced by the presence of different morphotypes in some of the sites. Such populations can count up to five morphotypes growing together. Seven morphotypes were here recorded from Malta; they are all hexaploid, even those which in other areas are tetraploid. Introduction include prostrate, ascending or fully erect individuals Portulaca oleracea L. (Portulacaceae), a herbaceous (Danin et al. 2014) and the morphological variability annual succulent plant, is a vigorous colonizer of is notable also among the populations, depending disturbed and waste habitats (it can also be a weed in on trophic and ecological conditions (Bel Hadj Salah cultivated fields, see Tutin et al. 1993) in all continents and Chemli 2004). Seed tegument is characterized by from temperate to tropical zones. Such a wide microsculptures (papillae, tubercles) and testa cells Downloaded by [Mr Stephen Mifsud] at 10:45 02 August 2016 distribution is due to its great adaptability (Zimmerman with different shape and ornamentation (stellulate, 1976; Matthews, Ketron, and Zane 1993) and to the isodiametric or elongated, rich in microsculptures or high rate of seed production (Zimmerman 1976). flat). The chromosome number is also highly variable. Its geographical origin is uncertain (Ocampo and Three main ploidy levels have been detected, with Columbus 2012): many hypotheses indicate different base chromosome number n = 9 (Matthews, Ketron, areas of the Old World, but it was also found in America and Zane 1994), e.g. diploids are 2n = 18, tetraploids in pre-Columbian times (Chapman, Stewart and 2n = 36 and hexaploids 2n = 54 (Danin et al. 2012). Yarnell 1973; Byrne and McAndrews 1975). It is also Additional reports of pentaploid forms (2n = 45) are cultivated as a vegetable in many parts of the world known from India (Sharma and Bhattacharyya 1956), (Bel Hadj Salah and Chemli 2004). The species, which and a case of chromosome number 2n = 52 was found is mainly autogamous (Kim and Carr 1990; Danin, in Japan (Sugiura 1936) and 2n = 48 was reported for Domina, and Raimondo 2008; Tison and de Foucault P. sardoa (Danin et al. 2012). These genomic differences 2014), is highly polymorphic, both in its habitus obviously represent a reproductive barrier among the and in seed tegument ornamentation. Populations different caryotypes (Danin and Reyes-Betancort 2006). CONTACT Fabrizio Buldrini [email protected] The supplementary material for this paper is available online at http://dx.doi.org/10.1080/23818107.2016.1200482. †This work is dedicated to the memory of Professor Avinoam Danin, world famous botanist, who did not live to see this article published. © 2016 Société botanique de France 2 A. DANIN et al. The chromosome number, together with seed tegument Danin (2011) and Danin and Raus (2012). For many ornamentations, was considered by several authors to Italian regions and the Maltese archipelago this is the be of taxonomic value, so that P. oleracea was regarded first in-depth investigation of the infraspecific diversity as an aggregate of 19 microspecies (Danin, Baker, and of P. oleracea s.l.; the study by Ricceri and Arrigoni Baker 1978; Danin and Reyes-Betancort 2006; Danin, (2000) is only partially comparable to ours, due to their Domina, and Raimondo 2008; Danin 2011; Danin different opinions about the infraspecific taxonomy of and Raus 2012; Danin et al. 2012). “Microspecies” is this species and to the significantly lower number of a term used to designate clonal individuals, genotypes samples examined. or ecotypes that evolve separately from others because This paper is a synthesis of all the available infor- of their apomictic reproduction (Dickinson 1998; mation concerning the presence and the distribution of Pihu et al. 2009). However, for P. oleracea, an eventual the various morphotypes of P. oleracea s.l. in the Italian apomixis has not been reported; indeed, the term peninsula and in surrounding islands. It is important “microspecies” was probably used in an inappropriate to consider as many sources of information as possible, way for this species. Recent phylogenetic studies also because of the peculiar geographical position and (Ocampo and Columbus 2012) show that P. oleracea is a geomorphological conformation of the Italian peninsula polyphyletic species, with evidence that it is a polyploid and the surrounding islands, which is probably one of complex (Soltis and Soltis 1999; Soltis, Soltis, and Tate the reasons for the great variety of environments of the 2003; Soltis et al. 2004). Hence, even though some Italian territory. authors have recently published important contributions The aims of the present research were: (El-Bakatoushi et al. 2013; Walter, Vekslyarska, and • to define the pattern of the distribution, in the Dobeš 2015), the taxonomy of P. oleracea is still open to Italian peninsula and adjacent islands, of the mor- debate. The various combinations of seed tegument, cell photypes of P. oleracea, to provide a contribution shape and cell ornamentations allow the recognition of for the assessment of their general distribution; different morphotypes, which are intended as informal • to extend caryological systematic studies on infraspecific taxonomic categories based on precise P. oleracea complex to the Maltese Islands, which morphological features (Maiti and Maiti 2011), without were not considered in previous researches (as connexion with genome asset or reproductive strategies. shown by Walter, Vekslyarska, and Dobeš, 2015, Such morphotypes are constant within the individuals, the chromosome number can vary also in the same so that the individuals themselves can be readily morphotype, so investigating an unexplored zone separated within the same population. To contribute could reveal novelties). to the debate in progress we focused our investigation on an area for which information on the infraspecific Materials and methods diversity of this species is fragmentary and irregular: the Italian peninsula and adjacent islands. We included in Seed samples analysis and distribution assessment our study Corsica, the Maltese Islands and some small The definition of fine-scale patterns was based on infor- valleys of Switzerland in the Canton of Grisons, very mation gathered from herbarium specimens, field col- close (2–3 km at most) to the Italian border, because lections and published data. all these areas are normally considered in the Italian Downloaded by [Mr Stephen Mifsud] at 10:45 02 August 2016 Classification was based on the analysis of seeds; floristic check lists (e.g. Zàngheri 1976; Pignatti 1982). for each morphotype we maintained the names for- In Italy, the first taxonomic study of P. oleracea merly attributed to the microspecies, only posing them (in this case treated as an aggregate of microspecies) between inverted commas to avoid confusion with the was performed by Ricceri and Arrigoni (2000). They microspecies mentioned in previous papers. The seed followed Danin, Baker, and Baker’s (1978) system and analysis was performed using a Reichert Austria No. reported the presence in Italy of five microspecies sensu 306 284 dissecting microscope at 40 × magnification. Danin