Spatial structure of seagrass suggests that size-dependent plant traits have a strong influence on the distribution and maintenance of tropical multispecies meadows.
BACKGROUND
Seagrass species in the tropics occur in multispecies meadows. How these meadows are maintained through species co-existence and what their ecological drivers may be has been an overarching question in seagrass biogeography. In this study, we quantify the spatial structure of four co-existing species and infer potential ecological processes from these structures.


RESULTS
Species presence/absence data were collected using underwater towed and dropped video cameras in Pulau Tinggi, Malaysia. The geostatistical method, utilizing semivariograms, was used to describe the spatial structure of Halophila spp, Halodule uninervis, Syringodium isoetifolium and Cymodocea serrulata. Species had spatial patterns that were oriented in the along-shore and across-shore directions, nested with larger species in meadow interiors, and consisted of multiple structures that indicate the influence of 2-3 underlying processes. The Linear Model of Coregionalization (LMC) was used to estimate the amount of variance contributing to the presence of a species at specific spatial scales. These distances were <2.5 m (micro-scale), 2.5-50 m (fine-scale) and >50 m (broad-scale) in the along-shore; and <2.5 m (micro-scale), 2.5-140 m (fine-scale) and >140 m (broad-scale) in the across-shore. The LMC suggests that smaller species (Halophila spp and H. uninervis) were most influenced by broad-scale processes such as hydrodynamics and water depth whereas large, localised species (S. isoetifolium and C. serrulata) were more influenced by finer-scale processes such as sediment burial, seagrass colonization and growth, and physical disturbance.


CONCLUSIONS
In this study, we provide evidence that spatial structure is distinct even when species occur in well-mixed multispecies meadows, and we suggest that size-dependent plant traits have a strong influence on the distribution and maintenance of tropical marine plant communities. This study offers a contrast from previous spatial models of seagrasses which have largely focused on monospecific temperate meadows.
School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Perth, Western Australia, Australia ; School of Earth and Environment, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Perth, Western Australia, Australia ; The UWA Oceans Institute, The University of Western Australia, Perth, Western Australia, Australia ; Department of Geography, Faculty of Arts and Social Sciences, Universiti Malaya, Kuala Lumpur, Malaysia.
Jillian L S
JL
Ooi
School of Earth and Environment, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Perth, Western Australia, Australia ; The UWA Oceans Institute, The University of Western Australia, Perth, Western Australia, Australia.
Kimberly P
KP
Van Niel
School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Perth, Western Australia, Australia ; The UWA Oceans Institute, The University of Western Australia, Perth, Western Australia, Australia.
Gary A
GA
Kendrick
School of Earth and Environment, Faculty of Natural and Agricultural Sciences, The University of Western Australia, Perth, Western Australia, Australia ; Centre for Ecohydrology, School of Environmental Engineering, The University of Western Australia, Perth, Western Australia, Australia.
Karen W
KW
Holmes
D000465:Algorithms; D035961:Alismatales / Q000145:classification / Q000254:growth & development*; D017753:Ecosystem; D005843:Geography; D008296:Malaysia; D008386:Marine Biology / Q000379:methods*; D008962:Models, Theoretical; D011157:Population Dynamics; D013045:Species Specificity; D014329:Tropical Climate; D014741:Video Recording