Empirical Evidence Supporting Frequent Cryptic Speciation in Epiphyllous Liverworts: A Case Study of the Cololejeunea lanciloba Complex

Ying Yu,Harald Schneider,Rui-Liang Zhu,Jochen Heinrichs,Ting Wang

doi:10.1371/journal.pone.0084124

Abstract

Cryptic species are frequently recovered in plant lineages, and considered an important cause for divergent of morphological disparity and species diversity. The identification of cryptic species has important implications for the assessment of conservation needs of species aggregates. The mechanisms and processes of the origin of cryptic species diversity are still poorly understand based on the lack of studies especially in context of environment factors. Here we explored evidence for cryptic species within the epiphyllous liverworts Cololejeunea lanciloba complex based on two loci, the plastid trnL-F region and the nuclear ribosomal ITS region. Several analytic approaches were employed to delimit species based on DNA sequence variation including phylogenetic reconstruction, statistical parsimony networks analysis and two recently introduced species delimitation criteria: Rosenberg’s reciprocal monophyly and Rodrigo’s randomly distinct. We found evidence for thirteen genetically distinct putative species, each consisting of more than one haplotype, rather than four morphologically-circumscribed species. The results implied that the highly conserved phenotypes are not congruent with the genetic differentiation, contributing to incorrect assessments of the biodiversity of epiphyllous liverworts. We hypothesize that evolution of cryptic species recovered may be caused by selection of traits critical to the survival in epiphyllous habitats combined with limited developmental options designed in the small body.

Highlights

Cryptic species, i.e. biological entities with reproductive isolation and/or genetic divergence without recognizable morphological disparity [1], are a major challenge to biodiversity research
This hypothesis is consistent with the observation of large number of cryptic species of animals occurring in extreme habitats [3,4,5] and cryptic land plant species growing either in aquatic or epiphyllous habitats [6,7,8,9] or in habitats with considerable desiccation stress [10]
Identical topologies were found in the consensus tree of the Bayesian analyses of the combined dataset with a partition in two regions and the most likely tree found in the maximum likelihood analyses (–InL = 5,606.879)

Summary

Introduction

I.e. biological entities with reproductive isolation and/or genetic divergence without recognizable morphological disparity [1], are a major challenge to biodiversity research. Despite our limited understanding of the processes, some evidence indicates that the origin of some or many cryptic species may coincide with the adaptation to extreme habitats [1,2]. This hypothesis is consistent with the observation of large number of cryptic species of animals occurring in extreme habitats [3,4,5] and cryptic land plant species growing either in aquatic or epiphyllous habitats [6,7,8,9] or in habitats with considerable desiccation stress [10]. We explored the hypothesis of cryptic species in the case of derived leafy liverworts growing in extreme environment by an attempt to provide some insights into the correlations of restricted “ecospace” and origin of cryptic species

Methods

Results

Conclusion