To what extent do geographic and associated environmental variables correlate with kelp morphology across temperate Australia?

Abstract

Intraspecific variation in morphology is common among marine algae and may allow plants to exist across a wide geography and range of environmental conditions. Morphological variation of Ecklonia radiata has been described over thousands of kilometres of the temperate Australian coastline; however, the degree to which this morphological variability is related to geographic and environmental variation is unknown. We tested the hypotheses that: (1) variation in the morphology of Ecklonia radiata, growing in both monospecific and mixed stands, is related to variation in latitude, longitude, wave exposure, temperature, depth and plant density (collectively referred to as ‘physical variables’); and (2) measures of morphological dissimilarity in E. radiata are greatest among locations that are separated by the largest geographic distances. The combined effect of the physical variables accounted for 74% of the variation in both monospecific and mixed stands. The majority of this variation was related to longitude and the remainder to wave exposure, water temperature and plant density. In monospecific stands, measures of morphological dissimilarity were consistently large between locations that were separated by the greatest geographical distances (>2500 km). The existence of such relationships may not indicate causality, but do contribute to a broad based understanding of major ecological patterns across temperate Australia’s coastline.

Reproductive Output, Synchrony across Depth and Influence of Source Depth in the Development of Early Life stages of Kelp

“…Individuals of E. radiata from 40 m sites were found to have less laterals than those from 7 m and less spinuosity than the ones from 25 m. We expected marked morphological differences across depth due to the exponential light attenuation with increasing depth (Kirk 1977) and the large depth range of our study (~30 m), though our results match other studies where marginal morphological variation as associated with depth (maximum study depths were ~17 m; Fowler‐Walker et al. 2005). The increased lateral width and stipe length that we observed in deep individuals is congruent with reported morphological responses of E. radiata in regions reduced light in New Zealand (Miller et al.…”

GENETIC AND MORPHOLOGICAL ANALYSES OF THE SOUTHERN BULL KELP DURVILLAEA ANTARCTICA (PHAEOPHYCEAE: DURVILLAEALES) IN NEW ZEALAND REVEAL CRYPTIC SPECIES1

“…Many macroalgae exhibit morphological variation along gradients of wave exposure, with a general trend toward larger stipes in more exposed locations ( D. antarctica : South and Hay 1979; Agarum and Costaria : Duggins et al. 2003; Ecklonia radiata : Fowler‐Walker et al. 2005; Turbinaria : Stewart 2006).…”

Morphology and photosynthetic response of the kelp Ecklonia radiata across a turbidity gradient

“…In the current study, there was a strong nonlinear relationship between SL and light; however, individuals at the two lowest light sites had short stipes, while individuals at the mid‐ to high‐light sites had longer stipes (between ca 75 and 120 cm in length). Stipe and thallus length can be associated with canopy density in kelp (e.g., Fowler‐Walker et al ). Of the sites examined in this study, the two lowest light sites also had the lowest density of kelp.…”