Citation: Christodoulou, S.; Chimona, C.; Rhizopoulou, S. Comparison of Pericarp Functional Traits in Capparis spinosa from Coastal and Inland Mediterranean Habitats. Plants 2022, 11, 3085. https:// doi.org/10.3390/plants11223085 Academic Editor: Ain Raal Received: 13 September 2022 Accepted: 8 November 2022 Published: 14 November 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). plants Brief Report Comparison of Pericarp Functional Traits in Capparis spinosa from Coastal and Inland Mediterranean Habitats Savvas Christodoulou , Chrysanthi Chimona and Sophia Rhizopoulou * Section of Botany, Department of Biology, National and Kapodistrian University of Athens, 15784 Athens, Greece * Correspondence: srhizop@biol.uoa.gr; Tel.: +30-210-7274513 Abstract: The caper (Capparis spinosa L.) is a winter deciduous, perennial plant that grows and completes its life cycle entirely during the dry season in the Mediterranean region. Mature caper fruits and their pericarp, collected from the wild shrubs of the Capparis spinosa grown in the inland and coastal sites of Greece during summer, have been studied in order to improve and complete our knowledge of the successful establishment of the C. spinosa in Mediterranean ecosystems. Caper fruits possess substantial nutritional, medicinal and ecological properties that vary according to the developmental stage, agroclimatic and geographical parameters; however, the fruit pericarp and pedicel, unlike the other aboveground plant parts of the caper, have not hitherto been studied. The higher sugar and starch content in the pericarps and fruit pedicels harvested from wild caper plants grown in coastal habitats was investigated in comparison with those from inland habitats, while the higher proline and nitrogen content in pericarps and fruit pedicels harvested from wild caper plants grown in inland habitats was investigated in comparison with those from coastal habitats. The PCA, based on the considered functional traits underlying the constitutional aspects, reveals groupings of fruit pericarp specimens of the C. spinosa collected from coastal and inland habitats that are grounds for adaptive variation. Keywords: caper; carbohydrates; drought; latitude; nitrogen; pericarp; proline; summer 1. Introduction The perennial, branched bush Capparis L. (Species Plantarum 1:503, 1753) is widely distributed in arid and semi-arid landscapes [1–3]; in Dioscoridis’ De Materia Medica (c. 64 AD) it is quoted as a plant distinct enough not to be confused with anything else, being referred to as “κ ´ αππαρις” (kapparis) [4–6]. The life cycle of the winter-deciduous Capparis spinosa L. (caper) lasts for six months, i.e., from May to October in the eastern Mediterranean [7–9]. C. spinosa begins to grow in May by forming new green stems that grow and branch close to the soil surface, as well as in crevices creeping along steep rocky cliffs, stony slopes, ruins and archaeological sites that act as conservative habitats [6,10–15]. The rapidly expanding leaves and numerous flower buds (Figure 1A) are developed on new elongating stems. C. spinosa blossoms entirely during the summer dry period, which is not favorable for flowering in the eastern Mediterranean [16,17]; its flowers (Figure 1B) expand at dusk and lose their turgor soon after the oncoming sunrise [17,18]. Such a rapid growth requires a substantial supply of water via a deep, extensive and conductive root system, which is another striking feature of this species [13,19–21]. Numerous studies in recent years have focused on the function, structure, chemical composition and medicinal uses of the flowers, buds, thorny stems, leaves and fruits of the C. spinosa, as well as this species’ evolution and the dispersal of its numerous seeds from dehiscent mature fruits [18,22–36]. It has been reported that wasps, which are active concomitantly with the ripening of caper fruits, act as “vectors” of its seeds, enhancing their dispersal [37]. Also, the odor [38–40] and other substances of mature caper fruits attract ants and lizards that serve as vehicles, influencing the long-distance dispersal of its small seeds that are adhered to their bodies and transferred to their nests [41,42]. Plants 2022, 11, 3085. https://doi.org/10.3390/plants11223085 https://www.mdpi.com/journal/plants