The Paradox of Cryptic Species

A cryptic species is quite the paradox. If it is cryptic, how do you identify it as a species?

Well with cryptic species there is usually a hint. A tickle at the back of your brain. Maybe it is a species with wide morphological variation or a complex distribution that makes you wonder whether there are additional species hiding within. 

Many cryptic species are uncovered when molecular data is used to examine the relationships between species. Members of a cryptic species may seemingly look the same, but not be each other's closest relatives. And thus the real adventure begins.

Medina, R; Lara, F; Goffinet, B; Garilleti, R; Mazimpaka, V. 2012. Integrative taxonomy successfully resolves the pseudo-cryptic complex of the disjunct epiphytic moss Orthotrichum consimile s.l. (Orthotrichaceae) Taxon 61:1180-1198.

The star of the show Orthotrichum consimile.  Figure 2B from Medina et al. 2012

In this paper Dr. Rafael Medina and coauthors undertook an exploration of the moss species Orthotrichum consimile and uncovered four cryptic species hiding within. They carried out this research using the process of reciprocal illumination. They first made a detailed morphological examination of many specimens from across the range of O. consimile and detected three different morphotypes (A, B, C). Basically they were able to group the specimens into three piles based on their appearance. These observations set the stage for their molecular analyses. They then extracted DNA from representatives of each morphotype and used portions of their genetic code to build a phylogenetic tree to test the relationships between the samples. They found that the morphotypes were placed into four distinct clades (monophyletic groups). The members of A and B were each in their own clade, whereas the members of C came out in two separate clades (C1, C2). They then re-examined the specimens of group C to see if there were any features that could be used to tell them apart. After closer inspection, they found that there were a few small, but detectable differences between the specimens in C1 and C2. Thus, the morphology and molecular data were reciprocally illuminating.Based on the molecular phylogeny and the morphological differences they describe four Orthotrichum species. A more restricted Orthotrichum consimile, O. columbicum, O. confusum (this is my favorite specific epithet of the bunch!), and O persimile. 

I think that this study is a great example of morphological and molecular research complementing each other to address a question of species relationships. With morphologically austere lineages (Bickford et al. 2007), such as bryophytes, the challenge of teasing apart cryptic species may seem daunting. However, this study of Orthotrichum shows that when a systematic and detailed approach is used, uncovering cryptic species is possible even in the morphologically austere mosses.

If you are interested in reading more about Dr. Medina's research or downloading a pdf of this paper check out his page on Academia.edu. 

Medina, R, Lara, F, Goffinet, B, Garilleti, R, & Mazimpaka, V (2012). Integrative taxonomy successfully resolves the pseudo-cryptic complex of the disjunct epiphytic moss Orthotrichum consimile s.l. (Orthotrichaceae) Taxon, 61 (6), 1180-1198