Integrating different tools to disentangle species complexes: A case study in Epidendrum (Orchidaceae)

Abstract

Species delimitation remains a central problem in systematic, taxonomic and evolutionary studies. However, the precise delimitation of species depends on the criteria used to identify lineages and the specific species concept that is applied. Recently, multidisciplinary studies using different data sources have significantly improved the delimitation of species within complex taxonomic groups, leading to an integrative taxonomy. To investigate the species delimitation within the Atlantic clade of Epidendrum (subg. Amphyglottium), four different species criteria were examined (phenetic differentiation, mono–phyly, diagnosability, absence of genetic intermediates). Morphometrics, plastid DNA sequences and nuclear microsatellite markers were used to explore the agreement between patterns recovered and species criteria tested. The conflicts among species criteria are discussed in light of pollination ecology, patterns of gene flow, reproductive isolation mechanisms and selective pressures currently acting in deceptive orchid species. Four currently recognized species from the Atlantic clade could be delimitated, including one newly described species, Epidendrum flammeus. Three out of five species satisfied the monophyly criterion, and few diagnostic flower characters were found among species. In contrast, nuclear microsatellite data correctly assigned individuals to their respective species, even in the presence of weak reproductive isolation and extensive hybridization events reported in the literature. One important implication of this finding is that phylogenetic studies in Epidendrum spp. should make use of single– or low–copy nuclear loci instead of plastid markers, which may be true for other plant groups. The results also indicate that the generalized pollination syndrome found among species of the Atlantic clade, the different levels of gene flow observed between nuclear and plastid markers, and hybridization events are commonly observed as the main evolutionary forces within this orchid group. Finally, we discuss evolutionary processes and taxonomic limits among these species, and we highlight the need to increase the inter–disciplinary approach to investigate species limits in complex plant groups.

Rock outcrop orchids reveal the genetic connectivity and diversity of inselbergs of northeastern Brazil

“…Epidendrum cinnabarinum and E. secundum are perennial, terrestrial species commonly found on inselbergs whose locations include sea-level to mountain elevations. Both species belong to subgenus Amphyglottium [60,61], a group of food-deceptive orchids whose flowers are visited by several butterfly species despite the lack of nectar reward (reviewed by [38]). Although the species are self-compatible, pollinators are necessary for seed set (Pinheiro unpub.…”

Taxonomy and evolutionary history of Alyssum montanum (Brassicaceae) and related taxa in southwestern Europe and Morocco: Diversification driven by polyploidy, geographic and ecological isolation

“…Highly variable intergenic spacers of maternally inherited, non-recombinant cpDNA have also been useful to determine relationships and evolution of closely related species (e.g., Borsch & Quandt, 2009;Consaul & al., 2010;. Multivariate morphometrics allows for in-depth examination of morphological variation which, in comparison with genetic data, is essential to define and delimit taxa (Pessoa & al., 2012). More specifically, our aims were to (1) determine how many and which taxa can be recognised in the study area, (2) clarify their circumscription and geographic distribution, (3) unravel their relationships and evolutionary history, and (4) identify the main evolutionary processes that have driven speciation in this species complex.…”

“…The taxonomically most significant traits include the morphology of stellate trichomes on leaves (number and length of trichome rays), trichome density and coverage, and size and shape of floral parts and leaves, although floral size is reduced towards the end of the flowering stage, and leaf size may also be highly variable. In species complexes with such intricate variation pattern in morphology, multiple lines of evidence including several unlinked genetic markers are desirable to arrive at a sound taxonomic treatment (Padial & al., 2010;Pessoa & al., 2012). An AFLP-based structure was used here as a starting point to delimit genetic entities (potential taxa) and their taxonomic status was examined by detailed morphometric analyses.…”

Epidendrum(Orchidaceae) as a model system for ecological and evolutionary studies in the Neotropics

“…The limited extent of genetic differentiation found among species (genetic distance = 0.01642-0.0004; Pinheiro & al., 2009b;Pessoa & al., 2012), phenotype-environment correlations (Hágsater & Soto-Arenas, 2005;Pinheiro & al., 2010) and fitness advantages of trait values in particular environments (Pinheiro & al., 2010) suggest a rapid adaptive radiation for this group. Multidisciplinary approaches are needed to test the hypothesis that Epidendrum represents an exemplar adaptive radiation (sensu Schluter, 2000).…”