Abstract
Lineage-based species definitions applying coalescent approaches to
species delimitation have become increasingly popular. Yet, the
application of these methods and the recognition of lineage-only
definitions have recently been questioned. Species delimitation criteria
that explicitly consider both lineages and evidence for ecological
‘role’ shifts provide an opportunity to incorporate ecologically
meaningful data from multiple sources in studies of species boundaries.
Here, such criteria were applied to a problematic group of
mycoheterotrophic orchids, the Corallorhiza striata complex, analyzing
genomic, morphological, phenological, reproductive-mode, niche, and
fungal host data. A recently developed method for generating genomic
polymorphism data–ISSRseq–demonstrates evidence for four distinct
lineages, including a previously unidentified lineage in the Coast
Ranges and Cascades of California and Oregon, USA. There is divergence
in morphology, phenology, reproductive mode, and fungal associates among
the four lineages. Integrative analyses, conducted in population
assignment and redundancy analysis frameworks, provide evidence of
distinct genomic lineages and a similar pattern of divergence in the
‘extended’ data, albeit with weaker signal. However, none of the
‘extended’ datasets fully satisfy the condition of a significant ‘role’
shift, which requires evidence of fixed differences. The four lineages
identified in the current study are recognized at the level of variety,
short of comprising different species. This study represents the most
comprehensive application of ‘lineage+role’ to date and illustrates the
advantages of such an approach.