Indeed, the B. rufescens from Los Tuxtlas are the only population of the species with maxillary teeth [ 29], a morphological character often used to delimit species of tropical salamanders [ 16, 43].
However, the identification of tropical marine fishes using morphological characters is often difficult and usually requires expert consultation.
Moreover, the identification of coccoid green microalgae through sampling and fixation can be misleading, because morphological characters are often not sufficient for a correct taxonomic determination.
The high level of cryptic species also shows that morphological characters are often unreliable for distinguishing species (16, 17, Figure 2).
Then, as morphological characters are often misleading, we applied the method developed by Pons et al. [ 28] that determines, with no prior expectations, the locations of ancestral nodes to define putative species.
As morphological characters alone are often insufficient for recognizing natural units, the analysis of nucleic acid sequences has significantly accelerated the progress towards achieving this challenging systematic goal.
The taxonomy of the group has long been problematic, as many of the morphological characters are continuous, often with multiple phenotypes present in a single population; many M. polymorpha individuals exhibit combinations of morphological traits that characterize two or three varieties, and individual plants may be intermediate between recognized taxa.
Balanophoraceae appear related to Santalales (sandalwood order), a position previously suggested from morphological characters that are often assumed to be convergent.
However, morphological characters influencing yield are often highly inter-correlated, leading to multi-collinearity when the inter-correlated variables are regressed against seed yield in a multiple-regression equation.
ACCTRAN is typically used with morphological characters, while DELTRAN is often used with geographic annotations (e.g. Wallace et al., 2007).
