Standardized response signatures of functional traits pinpoint limiting ecological filters during the migration of forest plant species into wooded corridors

We propose a trait-based metric package to elaborate ecological filters. Objective analysis should use multiple indicator traits and multiple metrics.

Dispersal limitation is unclear, low habitat quality for vectors is indicated.  Establishment filters include light competition and microsite availability.

The suggested set of metrics provided a clear ranking of traits and showed interpretational limitations of widely used short list of traits (e.g. seed weight, plant height and SLA). Results also demonstrate that there is no consistency between indicator metrics based on the shift in trait mean and those based on the reduction of variability, instead they provide complementary information.

We implement a trait comparison to the potential optimum level suggested by two ecological reference groups of species to interpret these responses as filter driven convergence or divergence. Unexpectedly, many characteristic traits of forest-specialist plants do not exhibit the expected responses. 

We show that biased conclusions about the functional efficiency of habitats and limiting ecological filters can be avoided when indicator analytics include (1) multiple response metrics and analytical methods, (2) multiple seemingly redundant traits, and (3) several reference groups for interpretation. The proposed analytical approach adjusts for (1) the indictor choice subjectivity, and (2) the scaling bias implemented in several ecological indicator trait systems, which over-emphasise qualitative preferences of species rather than reflect their real niches.