Trait covariance in fragments
SS-MH covariance had nearly all positive values, indicating that at all
sites larger seeds were associated with taller stature. In contiguous
forest, wetter (Climate axis 1) and warmer sites (Climate axis 2) had
lower SS-MH covariance, indicating more flexible combinations of stature
and seed size. The smaller range of SS-MH phenotypes at cooler sites
perhaps reflects the stress of lower temperatures at higher elevations
in contiguous forest. In fragments by contrast, warmer sites had strong
positive covariance of SS-MH, i.e., taller stature for a given seed
size. Keeping in mind that larger-seeded species declined at warmer
sites in fragments (Table 1), covariance patterns suggest smaller-seeded
but taller species do well in warmer sites. This phenotype is consistent
with long-lived pioneers (RĂ¼ger et al., 2018) and may reflect the fact
that despite increased light availability in fragments, loss of canopy
cover did not favor obligate heliophiles.
Notably, functional diversity explained variation in trait covariance
better than climate variables, even though the different aspects of
functional diversity did not vary between habitat types or along climate
gradients. Changes in covariances of SLA-WD and WD-MH with trait
variances showed that a larger trait space, especially of wood density,
supported very different phenotypic combinations within fragments
compared to contiguous forest. The causes, however, cannot be discerned
from this study. Biotic interactions, e.g., inter- and intraspecific
neighborhood interactions through natural enemies, can mediate
site-to-site variation in functional diversity (Lasky et al., 2014;
Muscarella et al., 2018, 2016). Whether neighborhood interactions differ
between fragments and contiguous forests remains poorly explored
(Krishnadas et al., 2018a). Local microclimate, unmeasured here, also
affect functional diversity directly or indirectly (Butterfield and
Suding, 2013; Krishnadas et al., 2018b; Muscarella et al., 2016). The
drivers of relationships between phenotypic constraints and functional
diversity merit deeper exploration in human-modified ecosystems.