Cryptic Speciation Patterns in Iranian Rock Lizards Uncovered by Integrative Taxonomy

Faraham Ahmadzadeh,Omid Mozaffari,Wolfgang Böhme,Morris Flecks,D James Harris,Dennis Rödder,Susana Freitas,Miguel A Carretero,Ulrich Joger

doi:10.1371/journal.pone.0080563

Faraham Ahmadzadeh, Omid Mozaffari + Show 7 more

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https://doi.org/10.1371/journal.pone.0080563

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Abstract

While traditionally species recognition has been based solely on morphological differences either typological or quantitative, several newly developed methods can be used for a more objective and integrative approach on species delimitation. This may be especially relevant when dealing with cryptic species or species complexes, where high overall resemblance between species is coupled with comparatively high morphological variation within populations. Rock lizards, genus Darevskia, are such an example, as many of its members offer few diagnostic morphological features. Herein, we use a combination of genetic, morphological and ecological criteria to delimit cryptic species within two species complexes, D. chlorogaster and D. defilippii, both distributed in northern Iran. Our analyses are based on molecular information from two nuclear and two mitochondrial genes, morphological data (15 morphometric, 16 meristic and four categorical characters) and eleven newly calculated spatial environmental predictors. The phylogeny inferred for Darevskia confirmed monophyly of each species complex, with each of them comprising several highly divergent clades, especially when compared to other congeners. We identified seven candidate species within each complex, of which three and four species were supported by Bayesian species delimitation within D. chlorogaster and D. defilippii, respectively. Trained with genetically determined clades, Ecological Niche Modeling provided additional support for these cryptic species. Especially those within the D. defilippii-complex exhibit well-differentiated niches. Due to overall morphological resemblance, in a first approach PCA with mixed variables only showed the separation between the two complexes. However, MANCOVA and subsequent Discriminant Analysis performed separately for both complexes allowed for distinction of the species when sample size was large enough, namely within the D. chlorogaster-complex. In conclusion, the results support four new species, which are described herein.

Highlights

Systematics is the biological science that addresses the fundamental patterns and processes associated with biological diversity and diversification [1,2], whose main goals are the discovery and description of species and the determination of the phylogenetic relationships between them [3]
Phylogeny and Bayesian Species Delimitation Our estimate of the phylogeny of Darevskia derived from cytochrome b data supports monophyly of D. chlorogaster
Both clades show remarkably high intraspecific divergences in this mitochondrial gene, exceeding interspecific divergences between many congeners (Figure S1.1 in File S1). This strongly suggests treating them as species complexes, with D. steineri included within the D. defilippii-complex

Summary

Introduction

Systematics is the biological science that addresses the fundamental patterns and processes associated with biological diversity and diversification [1,2], whose main goals are the discovery and description of (new) species and the determination of the phylogenetic relationships between them [3]. The fundamental unit in biology is the species, which plays a central role in research on ecology, evolution, conservation and biogeography [4,5,6]. Species concepts and species delimitation have been a matter of controversy since the early days of systematic biology [7,8]. Several recently developed methods for species delimitation offer the possibility to supplement each other [10,11,12,13,14], facilitating the call for an integrative taxonomy [15]. Morphological differences between populations may not necessarily be correlated with species boundaries and might not always be useful in discriminating species. Evolution under similar selective pressures or severe environmental extremes can limit changes in morphology and, lead to similar morphotypes [16]. It is acknowledged that most cryptic species result from recent speciation so that morphological or other diagnosable traits have not yet evolved or become manifested [20]

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