Community dissimilarity
Within-country community dissimilarity declined significantly from the
historic period to present at both reef zones; the decline was more
striking in the latter (Fig 4). Because the Pleistocene and Holocene
communities at both reef zones were more variable and had notably lower
average dissimilarity values compared to subsequent periods—likely due
to time averaging of the fossil data which comprise these time bins—we
designated the historical time bin (1500-1959) as the baseline for this
community metric. At both the reef crest and midslope zones, pairwise
comparisons of mean within-country dissimilarity values showed
significant declines from the baseline historical period (1500-1959) to
most recent period (2005-2011), with the first significant decline
relative to the baseline occurring in 2000-2004 at the reef crest and in
1985-1989 at the midslope zones (Figure 4).