Dispersal potential of Scaevola crassifolia (Goodeniaceae) is influenced by intraspecific variation in fruit morphology along a latitudinal environmental gradient

Abstract

Abstract. Dispersal of plant propagules by ocean currents can result in long-distance dispersal and is important for the persistence of coastal species. However, the ability of such species to disperse via the ocean is often unknown because there is relatively little evidence that demonstrates that seeds or fruits can float and survive for extended periods in seawater. Furthermore, the seed or fruit traits, and intraspecific variation in these traits, that facilitate buoyancy remain largely unidentified. The genus Scaevola (L.) contains several widespread coastal species that may be capable of oceanic dispersal, such as S. crassifolia (Labill). We collected fruits of S. crassifolia along 700 km of a latitudinal environmental gradient. These fruits were used to determine the influence of fruit morphology and anatomy on fruit buoyancy. Morphological and anatomical variation in S. crassifolia was associated with dispersal potential. Our empirical data demonstrated that fruits with larger aeriferous mesocarp layers have greater buoyancy and, therefore, enhanced capacity for long range oceanic dispersal. Of three characters hypothesised to affect buoyancy (aeriferous mesocarp, air pockets in empty locules, and number of vascular cavities), only the properties of the mesocarp were significant. Intraspecific variation can significantly affect dispersal potential, and should not be overlooked in dispersal ecology.

A research agenda for seed‐trait functional ecology

“…Unfortunately, few studies have considered reaction norms in seed traits and their responses to selection gradients (Cheptou et al ., ; Nicotra et al ., ). We therefore need studies investigating the impact of intraspecific seed‐trait variability on functions beyond the known cases of variability in dispersal potential (Guja et al ., ; Albert, ), or dormancy‐breaking and germination requirements (Huang et al ., ), especially in situations where dispersers or establishment seasons vary. For example, defence and seedling traits also might exhibit variation that relates to the spatiotemporal variability of predators, pathogens and light conditions.…”

Intrinsic and extrinsic drivers of intraspecific variation in seed dispersal are diverse and pervasive

“…However, limited evidence exists that seeds of epizoochorous species also vary intraspecifically in number, size and shape of appendages and in attachment potential (Gorb and Gorb 2002). We are aware of only one relevant study on hydrochory, where intraspecific variation in the size of the aeriferous mesocarp layers in Scaevola crassifolia fruits affected buoyancy (Guja et al 2014).…”

Conservation choice on the rare endangered plants Glehnia littoralis

“…The WGL fruits maintain high buoyancy presumably because of continual seawater selection (Nilsson et al , 2010; Yang et al , 2012, 2017). Repeated seawater surge along coastlines is a selective factor to eliminate the fruits that are not adept at keeping afloat during inundation or immersion, thus, enforces the WGL fruits to develop the buoyancy trait (Yang et al , 2012; Guja et al , 2014; Vazačová and Münzbergová, 2014). In contrast, the CGL growing inland were always cultivated by the locals, and, with the cultivation, their fruits were no longer selected by seawater inundation.…”