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.