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Australian Journal of Botany Australian Journal of Botany Society
Southern hemisphere botanical ecosystems
RESEARCH ARTICLE

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

Lydia K. Guja A B D , David J. Merritt B C , Kingsley W. Dixon B C and Grant Wardell-Johnson A
+ Author Affiliations
- Author Affiliations

A Curtin Institute for Biodiversity and Climate, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.

B Kings Park and Botanic Garden, West Perth, WA 6005, Australia.

C School of Plant Biology, Faculty of Science, The University of Western Australia, Crawley, WA 6009, Australia.

D Corresponding author. Present address: Centre for Australian National Biodiversity Research, CSIRO Plant Industry, Acton, ACT 2601, Australia. Email: Lydia.Guja@environment.gov.au

Australian Journal of Botany 62(1) 56-64 https://doi.org/10.1071/BT13290
Submitted: 3 December 2013  Accepted: 24 March 2014   Published: 28 April 2014

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.

Additional keywords: coast, hydrochory, oceanic dispersal, seed buoyancy.


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