Species–area relationship and small‐island effect of vascular plant diversity in a young volcanic archipelago

Abstract

Aims Aeolian islands form an active volcanic archipelago. By using updated vascular plant checklists for islands and islets, we tested four hypotheses: (i) Island species–area relationship (ISAR) of alien species has lower c‐ and higher z‐values than native species, (ii) islands with active volcanoes have lower species richness than expected for native and alien species, (iii) ISAR of native species shows lower c‐ and higher z‐values than ISARs of Mediterranean land bridge archipelagos and (iv) species richness of smaller islets is independent of area. Location Aeolian Archipelago, Mediterranean Basin. Taxon Vascular plants, identified and named according to the Flora of Italy (Pignatti et al., 2017–2019). Methods Checklists of native and alien plant species were obtained for eight islands and 24 islets. ISARs were fitted by the Arrhenius power function (S=c·Az) and used to test the first two hypotheses. The third hypothesis was tested by comparing ISAR of Aeolian Archipelago to those from other central and eastern Mediterranean archipelagos. The fourth hypothesis was tested by fitting models defining the presence and limit of the small‐island effect. Results The checklists included 894 species—749 native and 145 alien. ISARs fitted well for native and alien species and resulted in typical values of c and z parameters. The first and second hypotheses were supported by model fitting. The third hypothesis was not confirmed by the comparison of the ISAR of the Aeolian Archipelago with other archipelagos. The small‐island effect predicted by the fourth hypothesis was supported using S versus LogA for both native and alien species, while for native species it was supported also using the log transformation of the Arrhenius model. Main conclusions We reported a first comprehensive analysis of plant species richness in the unique Aeolian Archipelago, verifying typical ISARs, no peculiarity with respect to land bridge archipelagos and a somewhat unclear signal for the small‐island effect.

Remote sensing reveals fire-driven facilitation of a C4 rhizomatous alien grass on a small Mediterranean volcanic island

“…Small islands are particularly vulnerable to biological invasions (Bellard et al, 2016), due to the combined effect of the reduced species pool and the competitive traits of invasive species. This process has been reported for Mediterranean islands (Celesti-Grapow et al, 2016;Fois et al, 2020), particularly in the case of volcanic islands with ongoing or recent volcanic activity (Karadimou et al, 2015;Pasta et al, 2017;Chiarucci et al, 2021).…”

“…The island of Stromboli is the youngest and most active volcano in the Aeolian Archipelago (NE-Sicily); its subaerial activity began around 85 ka BP (Francalanci et al, 2013). Stromboli has the lowest number of species, as expected by the within archipelago species-area relationship among the seven largest islands of the Aeolian Archipelago, both for native and alien species (Chiarucci et al, 2021). By far the most common alien plant in Stromboli is a tall, vigorously growing rhizomatous grass, Saccharum biflorum Forssk., which was introduced in the 19th century as a windbreak.…”

The integration of the small‐island effect and nestedness pattern

“…To date, although a large number of studies have investigated the SIE or nestedness separately (e.g. Chen et al, 2021, 2022; Chiarucci et al, 2021; Matthews et al, 2014, 2015; Menegotto et al, 2020; Ulrich & Gotelli, 2007; Wang et al, 2013; Wang, Chen, et al, 2018; Wang, Wang, et al, 2018; Wang, Wang, et al, 2012; Wang, Zhang, et al, 2012; Wright et al, 1998; Xu et al, 2017; Zhang et al, 2023), no study has tried to integrate these two biogeographical patterns.…”

There is room for everyone: Invasion credit cannot be inferred from the species–area relationship in fragmented forests

“…This is possible by using the species–area relationship (hereafter SAR), that is, the relationship between the number of species and the sampled area. A similar approach might be suitable to predict the “invasion credit” (i.e., considering colonization by native and alien species) but, so far, studies about the application of SAR in the invasion context are few and mainly focused on testing island biogeography theory and the consistency between alien and native species patterns (Hulme, 2008; Blackburn et al, 2016; Chiarucci et al, 2021). On the other hand, SAR is considered a fundamental pattern in ecology (Schoener, 1976; Scheiner, 2003; Scheiner et al, 2011) and it has been used in several studies to understand how biodiversity changes when habitat is lost or fragmented into smaller island‐like habitats (Diamond, 1975; Hanski et al, 2013; Fahrig, 2017).…”