Does Flowering Synchrony Contribute to the Sustainment of Dry Grassland
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Flora 222 (2016) 96–103 Contents lists available at ScienceDirect Flora j ournal homepage: www.elsevier.com/locate/flora Does flowering synchrony contribute to the sustainment of dry grassland biodiversity? a,∗ a a b Edy Fantinato , Silvia Del Vecchio , Antonio Slaviero , Luisa Conti , b a Alicia Teresa Rosario Acosta , Gabriella Buffa a Department of Environmental Sciences, Informatics and Statistics, Ca’ Foscari University of Venice, Via Torino 155, 30172 Venice, Italy b Department of Sciences, Roma Tre University, Viale G. Marconi 446, 00146 Rome, Italy a r t i c l e i n f o a b s t r a c t Article history: Phenological relationships among entomophilous species for pollination may play an important role in Received 20 January 2016 structuring natural plant communities. Received in revised form 1 April 2016 The main aim of this work was to test whether in dry grassland communities there is a non-random Accepted 7 April 2016 flowering pattern and if the pattern influences the species richness, and the richness of subordinate and Edited by Fei-Hai Yu common species. Available online 11 April 2016 Field sampling was carried out in temperate dry grasslands in NE Italy. Species composition and the flowering phenology were monitored in 45 2 m × 2 m plots randomly placed over dry grasslands. Keywords: To quantify the degree to which insect-pollinated species overlap in their flowering time we developed Co-flowering index a “co-flowering index” (CF-index). The significance of the observed flowering pattern was tested using a Generalists and specialists species Pollinator sharing null model. Rare species A positive correlation was found between the synchronic flowering and the number of subordinate Species interactions species. Subordinate species showed shorter flowering length than the common species and a mostly specialized pollination system. Our findings suggest that flowering synchrony might be a key characteristic which may contribute to shape dry grassland composition by favouring the long lasting maintenance of rare species populations within the community. The comprehension of such functional relationships between species of different trophic levels is of great importance for the conservation of dry grasslands and the maintenance of the ecosystem services that pollination provides. © 2016 Elsevier GmbH. All rights reserved. 1. Introduction nators are assumed to exert comparable selection pressures, thus generating correlations among floral traits (e.g., color, long and Biotic interactions have long been investigated as a possible narrow corolla tubes, or particular nectar quantities and concentra- mechanism governing and maintaining species richness within a tions) (Armbruster et al., 1999, 2000; Fenster et al., 2004). Although community (Brooker et al., 2008; Bonanomi et al., 2011; Hallett generalist pollination systems are frequent on a global scale, also et al., 2014). Among the wide variety of biotic interactions, pheno- specialization is common and is assumed to have been integral logical relationships among entomophilous species for pollination to angiosperm diversification (Johnson and Steiner, 2000). Most have been hypothesized as playing an important role in struc- angiosperms produce recognizable suites of convergent floral traits turing natural plant communities (Feldman et al., 2004; Moeller, and reward sources that recur in flowers of different evolution- 2004; Ghazoul, 2006; Callaway, 2007; Brooker et al., 2008). Polli- ary origin but that share similar pollinators (Rodríguez-Gironés and Santamaría, 2004; Thomson and Wilson, 2008; Willmer, 2011; Sonkoly et al., 2016). In this way, plant-plant relationships may have been modified in order to ensure and/or enhance the visitation ∗ Corresponding author. rate, eventually influencing community structure and dynamics. E-mail addresses: [email protected] (E. Fantinato), Especially, the sharing of the same temporal niche (synchronous [email protected] (S. Del Vecchio), [email protected] (A. Slaviero), flowering periods) by different plant species increases the abun- [email protected] (L. Conti), [email protected] dance of floral resources. This in turn could enhance the possibility (A.T.R. Acosta), [email protected] (G. Buffa). http://dx.doi.org/10.1016/j.flora.2016.04.003 0367-2530/© 2016 Elsevier GmbH. All rights reserved. E. Fantinato et al. / Flora 222 (2016) 96–103 97 Fig. 1. Study area. Euganean Hills are enclosed within the black square. of pollinator sharing and ensure the survival of rare and extremely sustain most processes and functions. Accordingly, increased atten- selective entomophilous species (Laverty, 1992; Johnson et al., tion was paid to processes involving relatively dominant species 2003; Ghazoul, 2006). (Schwartz et al., 2000; Lawler et al., 2001; Cardinale et al., 2006). The phenological synchronization of flowering and fruiting is Recently, however, several authors have emphasized the role of supposed to affect inter-specific patterns at several scales, from the whole diversity, comprising less common species, in assuring population to community and landscape (Frankie et al., 1974; ecosystem stability and functioning across time (Allan et al., 2011; Ollerton and Lack, 1992, 1998; Bronstein, 1995; Vilela et al., 2014; Mouillot et al., 2013). Borchert et al., 2005). For example, asynchronous ripening of fruits According to Tilman (2004), the abundance of a species is pro- among certain species in a community was interpreted as a mech- portional to the amount of the habitat that has the environmental anism for avoiding competition for seed dispersers (Wheelwright, conditions that match the species requirements. Thus, less common 1985). Conversely, flowering synchrony of individuals in a given species are those better adapted to less common environmental population has been proved to influence both the quantity and conditions in a habitat and are likely to possess functional traits genetic quality of their offspring, by affecting the number of poten- distinct from those of common species. Indeed, rare or subordinate tial mates and the foraging efficiency of pollinators (Schemske, species have been recognized as increasing both species richness 1977). At a different scale of observation, Dante et al. (2013) (Wellstein et al., 2014) and the functional diversity of communities revealed how relationships among co-flowering entomophilous (Richardson et al., 2012); they are also expected to support ecosys- species drive species assemblage and distribution within an old- tem functioning under future environmental conditions (Mouillot field plant community, highlighting the importance of pollination et al., 2013). At the same time, in the majority of ecological commu- interactions in influencing ecosystem structure and functioning. nities, rare species are expected to be at higher risk of extinction During the last decade, there has been a consensus in ecological than dominant ones (Purvis et al., 2000). Therefore, the identifi- and environmental sciences about the interdependence between cation of patterns related to the maintenance of species diversity species richness and ecosystem functioning (Sachs et al., 2009; and, in particular, of the rare or subordinate species in ecological Hooper et al., 2005), although with contrasting views. Schwartz communities should be mandatory when investigating ecosystem et al. (2000) proposed that this relationship generally follows an functioning (Allan et al., 2011; Mouillot et al., 2013). asymptotic trend, suggesting that only few species are needed to 98 E. Fantinato et al. / Flora 222 (2016) 96–103 European temperate calcareous dry grasslands provide a par- Dorycnium pentaphyllum ssp. herbaceum, Eryngium amethystinum, ticularly suitable example to this specific issue. Their biological Salvia pratensis ssp. bertolonii, Sanguisorba minor, S. triandra, etc.). diversity is high and includes a variety of rare and endangered Given the high percentage of Mediterranean and Illyrian taxa and species from different taxonomic groups (Van Helsdingen et al., the phytogeographical and ecological context, the community can 1996; Ssymank et al., 1998). They are among the most diverse be referred to the alliance Saturejion subspicatae Tomic-Stankovi´ c´ plant communities of the world at small spatial scales, mirroring 1970. intricate coexistence mechanisms (Wellstein et al., 2014; Dengler Originally, sampled grasslands had been managed by low- et al., 2014). A high species richness is also found for butterflies intensive mowing practices. Since the foundation of the Park and and other invertebrates (Bobbink and Willems, 1988; Van Swaay, the SPA/SCI management plan, they have been subject to yearly 2002). In Europe, semi-natural dry grassland make up the major- mowing and grazed every three years. ity of High Nature Value farmland and harbor the majority of EU farmland biodiversity (Collins, 2012; Habel et al., 2013). Given their 2.2. Data collection importance they are listed in Annex I of the EU Habitat Directive (CE 43/92) as priority habitats, i.e. “natural habitat types in danger We selected 15 dry grassland areas extending from 0.27 ha to of disappearance”. 6.95 ha (ranging from 68 m a.s.l. to 284 m a.s.l.). Altogether 45 plots 2 In light of these considerations, this work’s main aim was of 2 m × 2 m (4 m ) were selected using a stratified random sam- to analyze flowering synchrony among entomophilous species in pling design. For each plot, species composition was recorded and temperate dry grassland