Grana ISSN: 0017-3134 (Print) 1651-2049 (Online) Journal homepage: http://www.tandfonline.com/loi/sgra20 The metareticulate pollen morphology of Alternanthera Forssk. (Gomphrenoideae, Amaranthaceae) and its taxonomic implications Ivonne Sánchez-del Pino, Sara Fuentes-Soriano, Karen Z. Solis-Fernández, Rolando Pool & Rita Alfaro To cite this article: Ivonne Sánchez-del Pino, Sara Fuentes-Soriano, Karen Z. Solis-Fernández, Rolando Pool & Rita Alfaro (2016) The metareticulate pollen morphology of Alternanthera Forssk. (Gomphrenoideae, Amaranthaceae) and its taxonomic implications, Grana, 55:4, 253-277, DOI: 10.1080/00173134.2015.1120774 To link to this article: http://dx.doi.org/10.1080/00173134.2015.1120774 Published online: 30 Mar 2016. Submit your article to this journal Article views: 74 View related articles View Crossmark data Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=sgra20 Download by: [Centro de Investigacion Cientifica de Yucatan] Date: 24 April 2017, At: 08:24 Grana, 2016 Vol. 55, No. 4, 253–277, http://dx.doi.org/10.1080/00173134.2015.1120774 The metareticulate pollen morphology of Alternanthera Forssk. (Gomphrenoideae, Amaranthaceae) and its taxonomic implications IVONNE SÁNCHEZ-DEL PINO1, SARA FUENTES-SORIANO2, KAREN Z. SOLIS-FERNÁNDEZ1, ROLANDO POOL1 & RITA ALFARO3 1Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán, Mérida, Yucatán, México, 2Department of Biology, Indiana University, Bloomington, IN, USA, 3Bio Mieles del Sureste, Mérida, Yucatán, México Abstract Alternanthera (Amaranthaceae) is a diverse genus largely restricted to the American Tropics that belongs to the alternanther- oid clade containing C4 and C3–C4 intermediate species. This research focuses on the study of pollen characters by studying 13 species, representatives of the two major clades and subclades of Alternanthera. General palynological comparisons were conducted with light microscopy (LM), scanning electron microscopy (SEM) and with confocal laser scanning microscopy (CLSM) for exine ultrastructure. Twenty-five characters were measured and described for Alternanthera and among these, 14 pollen characters were used to discriminate pollen groups using cluster analysis and canonical analysis of principal coordinates (CAP). Pollen form and ornamentation, pores number, spines length, number of ektexinous bodies and nanospines on the ektexinous bodies on pore membranes, arrangement of nanopores and spines on structural elements, and metareticula form were taxonomically important and therefore used to construct the first palynological key to the alternantheroid clade species. Our study indicates that the seemingly subtle morphological variation of pollen is useful for recognising three main pollen types within Alternanthera. The much needed palynological terminology for describing the mesoporium in the metareticulate pollen of Amaranthaceae is provided. Keywords: althernantheroids, mesoporia, pollen morphology, scanning electron microscopy, confocal laser scanning microscopy Alternanthera includes 80–200 species (Mears 1977; (Robertson 1981; Eliasson 1987; Iamonico & Sán- Robertson 1981; Eliasson 1987, 1990; Townsend chez-del Pino 2012). 1993; Siqueira 2004; Sánchez-del Pino et al. 2012) Most Alternanthera species are annual or perennial and is the third or fourth most diverse genus in the herbs, rarely shrubs or trees (Robertson 1981). The family Amaranthaceae. The genus is Neotropical genus is characterised by its short spike inflores- (Townsend 1993) with the greatest centres of diver- cences; flowers with stamens united into a cup; glo- sity in South America (Mears 1977), India, Pakistan bose or subglobose stigmas (Townsend 1993); and and China (Chin & Lim 2011) in order of relevance. triangular, ligulate and laciniate pseudostaminodia Thirteen indigenous species (nine endemics) are dis- (Eliasson 1988). Species of the monophyletic Alter- tributed in the Galápagos Islands (Eliasson 1988, nanthera are easily recognised by their globose or 2004) and 14 species (seven natives) in Australia subglobose stigmas (Sánchez-del Pino et al. 2012). (APNI 2010+). Recently, c. four new species and Important contributions to the description and six infraspecific taxa from Argentina and Paraguay classification of the morphologically conserved (i.e. have been reported (Pedersen 1997, 2000). Alter- stenopalynous) pollen types within Amaranthaceae s. nathera includes ornamentals (Robertson 1981; str. have been published in the last 65 years (Now- Eliasson 1987), and some species are considered icke 1975; Skvarla & Nowicke 1976; Nowicke & invasive weeds in different parts of the world Skvarla 1977, 1979; Erdtman 1986; Eliasson 1988; Correspondence: Ivonne Sánchez-del Pino, Centro de Investigación Científica de Yucatán, A. C. Calle 43 No 130 Col. Chuburná de Hidalgo, CP. 97200, Mérida, Yucatán, México. E-mail: [email protected] (Received 16 March 2015; accepted 22 September 2015) © 2016 Collegium Palynologicum Scandinavicum 254 I. Sánchez-del Pino et al. Borsch 1998; Borsch & Barthlott 1998; Müller & ularly arranged in a line, pores of type I’ (Borsch Borsch 2005b). Erdtman (1986), following Schinz’s 1998, pp. 130, 134). (1934) pollen classification, recognised two basic Chin and Lim (2011), most recently summarised pollen types within the Amaranthaceae: the Amar- in a table the 20 species of Alternanthera from the anthus-type, characterising the Amaranthoideae, and New World, India, Pakistan and China with respec- the Gomphrena-type, typical of the Gomphrenoideae. tive references published for palynological data This last pollen type is distinguished by the presence since 1962. These authors also studied the palyno- of a reticulum that is not present in the Amaranthus- logical variation of three widespread species present type. The Gomphrena-type pollen is, according to in Peninsular Malaysia. Their findings supported Erdtman (1986, p. 41), differentiated by ‘muroid that pollen of Alternanthera is similar to Pfaffia pol- ridges separated by luminoid, aperturiferous (or len as suggested by Borsch (1998) and indicated aperturoidiferous) depressions’ and differentiated that number and shape of apertures (pores) and from the Amaranthus-type pollen in having pores at distribution of microspines on the sexine were the bottom of these depressions (Zandonella & important pollen characters for differentiating Pfaf- Lecocq 1977). fia from Alternanthera. The exine ultrastructure in Vishnu-Mittre (1963) distinguished nine pollen Alternanthera is organised as in all Centrospermae types based on the size and distribution of supra- and consists of four layers, the tectum, columellae, tectal processes or sculpture on the tectum for the foot layer and a single continuous layer below the Indian Amaranthaceae species. Later, Zandonella foot layer or endexine (Skvarla & Nowicke 1976; and Lecocq (1977),basedonpollenform,pore Eliasson 1988). number and tectum sculpture, further subdivided Pollen morphology in Amaranthaceae has been Erdtman’s(1952) Amaranthaceae pollen type informative at different taxonomic levels (Borsch classes into five subtypes. More recent palynologi- 1998). Its variation has supported the potential res- cal contributions for the Amaranthaceae by Elias- urrection of genera (e.g. Hebanthe: Borsch & Peder- son (1988), Borsch and Barthlott (1998)and sen 1997), recognition of clades (e.g. subfamily Borsch (1998)haveshowntheusefulnessofpollen Gomprenoideae: Sánchez-del Pino et al. 2009) and characters in the taxonomy of the family. In a species and infraspecific categories (e.g. Tidestromia: proposal for a revised and updated terminology to Sánchez-del Pino 2001; Sánchez-del Pino et al. describe the pollen types in Amaranthaceae, 2002; Sánchez-del Pino & Flores Olvera 2006). Borsch and Barthlott (1998) introduced the con- Recent palynological sources focused on Neotro- cepts of metareticulate pollen, mesoporia, conjunc- pical Alternanthera consists of only microphoto- tion points and structural elements to describe the graphs as those from endemic species in the ornamentation of the amaranthoid pollen and Galápagos Islands (Jaramillo et al. 2014) or palyno- changed the whole understanding of pollen mor- logical descriptions for few species in Mexican paly- phology in the family. nofloras like that of Martínez and Matuda (1979), The metareticulum (singular of metareticula) is a Quiroz-García et al. (1994, Alternanthera cf. Alter- type of reticulum-like ornamentation composed by nanthera pycnantha Standl.) and Palacios-Chávez vaulted mesoporia, a structure homologous to the et al. (1991, A. ramosissima [Mart.] Chodat et meshes of the ‘reticulate pollen’ (Borsch & Barthlott Hassl.). Although these works have been relevant to 1998, p. 68). The mesoporia refers to the tectated define basic pollen characters in the genus (Erdtman areas surrounding two sunken pores. This type of 1986; Eliasson 1988; Borsch 1998), studies about pollen sculpture and aperture organisation is syna- patterns of pollen evolution within Alternanthera in pomorphic for the core gomphrenoid (Kadereit et al. a phylogenetic context are yet to be developed (Sán- 2003; Müller & Borsch 2005a, 2005b) and the gom- chez-del Pino & Fuentes-Soriano, own observation, phrenoids+alternantheroids clade (Sánchez-del Pino March 2015). et al. 2009). In this work, we assess the morphological variation Borsch (1998) used pollen shape, mesoporia form of pollen within Alternanthera with the main objec- (flat or vaulted), tectum