1. Introduction

In traditional classification, Scrophulariaceae sensu lato (s.l.) are the largest family in the Lamiales. The members of the family can be distinguished from related families by bilaterally symmetrical and often tubular flowers, ovaries with axile placentation and numerous ovules, and many seeded capsular fruits. However, recent molecular studies have suggested that it is not the presence of a suite of uniquely derived characteristics that allows for the easy recognition of a member of Scrophulariaceae s.l. but, rather, the absence in Scrophulariaceae of the synapomorphies that characterize closely related families [1]. The taxonomic problem of the Scrophulariaceae s.l. is one aspect of the widespread difficulties that reflect the problems of describing natural groups within the order Lamiales. As with most large families, previous classification of the family includes many treatments that differ in their circumscription (for example, see [2]). The most influential classifications for the nineteenth century concept of Scrophulariaceae were those of in [3, 4], from which most contemporary classifications of the family are derived. A large-scale investigation of phylogenetic relationships in the Scrophulariaceae s.l. and related families using DNA sequence data has radically altered the circumscription of many families in Lamiales [1, 2, 5–7].

Before the revolution in molecular systematics, many studies proposed that Scrophulariaceae s.l. were monophyletic and several morphologically similar groups of taxa, which are now assigned to different families, and were placed together (for example, see [8]). For the first time in [2], the study identified two clearly separated clades consisting of members of the family and suggested that the Scrophulariaceae are polyphyletic. Subsequently, a third clade was identified consisting of parasitic members of the Scrophulariaceae and Orobanchaceae [9–11]. Later on five distinct phylogenetic lineages composed mainly of taxa previously assigned to Scrophulariaceae were recognized [5]. However, the emerging classification for the plants which are traditionally assigned to Scrophulariaceae consists of at least seven groups that bear the rank of family [12–14]. Most notable, following changes in the circumscription of families and the disintegration of Scrophulariaceae s.l., were the dramatic changes in the size of some families: the Scrophulariaceae itself was more than halved in size to just over 1800 species, and the Plantaginaceae increased to about 1900 species [15].

The morphological similarities and differences among the groups of taxa and their alignment in various families usually depend on the characters emphasized by different researchers. On the other hand, complications in discriminating between genera or groups of genera are usually the result of the available suite of usable characters, and thus, several comparative studies were carried out. In general, systematics uses morphological characteristics to carve diversity into its taxonomic subunits, and since the beginning of the discipline, plant systematics has frequently used morphological character ranges from roots, leaves, inflorescence, flowers, and fruit to seeds.

Due to its great uniformity, seed morphology has been recognized as an important source of useful phylogenetic information. A number of angiosperm taxa have already been investigated intensively in terms of their seed morphology, in combination with phenetic or phylogenetic analyses at the genus level. In the past, the variation in seed morphology has been used variously in plant systematics ranging from identification [16, 17] and taxonomic circumscription [18, 19] to phylogenetic inference [20, 21] and character-state evolution [22, 23]. Both macro- and micromorphological seed characters have been shown to be of essential systematic importance within and among the genera of traditional Scrophulariaceae, Orobanchaceae, and Plantaginaceae [24–35], in which seed morphological characters have been used widely to differentiate the different taxa or to find affinities between them.

Recent studies on seed morphology of Scrophulariaceae s.l. have focused mainly on common genera like Veronica, Scrophularia, and Pedicularis. Juan et al. [30] observed fruits and seeds of Scrophulariaceae from southwest Spain, and the systematic significance of seed morphology of Veronica and Pedicularis has been examined in some comprehensive studies [32–34]. Despite the aforementioned, no comparative studies on seed anatomy or seed coat characteristics together with surface structure have been conducted on any genera of Scrophulariaceae s.l. It is necessary to make extensive investigation of the seed morphology and anatomy of Scrophulariaceae s.l. to determine whether they can be used as additional support for disintegration of genera in the family. The objectives of this study were to (1) understand the utility of seed morphology and anatomy in Scrophulariaceae s.l. systematics, (2) discuss the proximity of studied genera based on these characters, and (3) highlight the characters that can be used to describe different genera and possible variation in infrageneric classification of Veronica on a similar basis.
