β Diversity is an ecological concept used to
describe the turnover of species across a wide range of
spatial and temporal scales, but such knowledge is lacking
for macroalgal assemblages of the Red Sea. β Diversity patterns
for Red Sea macroalgae were evaluated from different
sites (Hurghada, Safaga, and Al-Quseir) and seasons
across different environmental disturbances. β Diversity
was studied by partitioning the total number of species (γ
diversity) into additive components. Geographical heterogeneity
was more important than seasonal heterogeneity
in structuring macroalgae both at species and functional
group levels. Species replacement as a component of β
diversity produced dissimilarity in species composition
and taxonomic structure. Replacement of species between
sites was responsible for the presence of new functional
groups of macroalgae. High β diversity and taxonomic
similarity values were characteristic of the macroalgae of
the Red Sea. The occurrence of small macroalgal thalli that
have short life cycles induced high species replacement
and subsequently high β diversity, with spatial heterogeneity
and environmental gradient as drivers of β diversity.
Anthropogenic disturbance at the Safaga site was suggested
to induce variation of macroalgal assemblages and
functional groups. Excluding rare species from the data
set did not change the high values of b diversity.