Comparative morphometry as a diagnostic tool applied to species delimitation in the genus Gastridium P. Beauv. (Poaceae)

Abstract

Based on critical examination of both fresh and dried specimens and a morphometric analysis of herbarium specimens we performed a comparative study of the three closely related Gastridium (Poaceae, Tribe: Poeae, Subtribe: Agrostidinae) species G. ventricosum, G. phleoides and G. scabrum collected in Italy. The study aimed to provide new diagnostic tools to improve the taxonomy of the genus and confirm species delimitation. Variation in floral morphology in the three species was explored using seven quantitative and ten qualitative characters measured on 318 spikelets, both awned and unawned. Statistical methods, including principal components analysis (PCA) and non‐metric multidimensional scaling (NMDS), were used. Numerical analyses showed a general distinctness of spikelets and florets, consistent with the three studied species, and revealed among and within species variation patterns in both spikelet types. Accordingly, the most informative quantitative characters appeared to be the width and length of glumes and the length of awns, useful to distinguish G. phleoides which has the narrowest glumes and longer awns than the other species, while G. scabrum has the widest glumes. The most informative qualitative characters appeared to be the presence/absence of thick hairs or minute tubercles on the upper side of the lemma. The autonomy of the three studied species was confirmed. The taxonomic significance of the results is briefly discussed, and notes on the species distribution are included. Some nomenclatural and taxonomic notes on G. scabrum, of which literature still showed evidence of a general unawareness, are provided.

Genetic diversity and taxonomic issues inGastridiumP.Beauv (Poaceae) inferred from plastid and nuclear DNA sequence analysis

“…Of these, 30 individuals were freshly collected in wild populations, mostly located in peninsular Italy and Spain, and 14 samples were harvested from CLU, COFC, PORUN, UTV herbaria (acronyms according to Thiers 2018) and the U.S. National Plant Germplasm System (NPGS). Species identification was carried out according to Romero García (2019) and Scoppola and Cancellieri (2019). Vouchered herbarium specimens of collected plants were stored at the herbarium of the Tuscia University (UTV).…”

“…It is characterized by dense panicles with heteromorphic unifloral spikelets, each bearing unequal, slightly saccate glumes, laterally compressed and acute at the apex, with subterminal awn or unawned lemmas, and caryopses enclosed between the lemma and palea (Doğan, 1985; Scholz, 1986). Despite an overall morphological distinctness (Kellogg, 2015), resolving the taxonomy of Gastridium has been particularly challenging in the past, and its members have been alternatively included in other genera such as Agrostis L., Milium L., Lachnagrostis Trin., Calamagrostis Adans., and Triplachne Link (Scoppola & Cancellieri, 2019, and references therein). Today, it is placed within subfamily Pooideae Benth., tribe Poeae R.Br., subtribe Agrostidinae Fr.…”

“…One of these entities is the Steno-Mediterranean G. scabrum C. Presl, recorded in Northwest Africa, East Spain, South France, Central and South Italy, Greece and the Aegean, Northwest Turkey, and West Asia (Bolòs & Vigo, 2001; Dimopoulos et al, 2013; Doğan, 1985, Feinbrun-Dothan, 1986; Pignatti, 2017; Pyke, 2008; Tison & De Foucault, 2014). It can be found on Mediterranean dry areas, pastures and abandoned fields, where the turf is broken by patches of crumbling soil (Scoppola & Cancellieri, 2019). A fourth taxon is G. lainzii (Romero García) Romero Zarco, ≡ Gastridium phleoides subsp.…”

“…scabrum (C. Presl) O. Bolòs, G. phleoides subsp. lainzii Romero García], and in doubtful assignations of specimens in field inventories and herbaria (Scoppola & Cancellieri, 2019). The different treatments are also mirrored on the main sources of plant taxonomy information such as The Plant List (http://www.theplantlist.org/), Euro+Med (http://www.emplantbase.org/), and GrassBase (Clayton et al, 2006 onwards), whereas G. lainzii was only recently added to Tropicos (http://www.tropicos.org).…”

“…lainzii; Lambinon & Deschâtres, 1994; López Tirado & Scoppola, 2017; Pyke, 2008; Romero García, 1996; Scholz, 1986) and the large, sometimes overlapping variation of some characters traditionally reported in literature (e.g., panicle shape, ligule length; Scholz, 1986; Jauzein, 2003) are the most likely obstacles to a resolved taxonomy. Recently, an enhanced combination of diagnostic characters has been provided, mostly based on some qualitative characters of florets, neglected in standard floras (Scoppola & Cancellieri, 2019), allowing a consistent circumscription of these taxa.…”