Characteristics of data subsets and selected substitution models.

<p>Data subsets used in phylogenetic analyses and their characteristics; VC = variable characters, PIC = parsimony informative characters; [ ] = ingroup only. The partitioning scheme and the respective substitution models were chosen with the software PartitionFinder <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0068082#pone.0068082-Lanfear1" target="_blank">[27]</a>.</p

Species-key to the <i>C. kelleri</i>-group.

<p>Antennae with second and third funicular segment longer than wide (<i>C. kelleri</i>, CASENT0317629).</p

How Much Variation Can One Ant Species Hold? Species Delimitation in the <i>Crematogaster kelleri</i>-Group in Madagascar

<div><p>We investigated the species-level taxonomy of the Malagasy <i>Crematogaster</i> (<i>Crematogaster</i>) <i>kelleri</i>-group and an additional more distantly related species of the same subgenus. Morphological data from worker, queen and male ants, as well as genetic data from three nuclear genes (long wavelength rhodopsin, arginine kinase and carbomoylphosphate synthase) and one mitochondrial marker (cytochrome oxidase I) led to the recognition of six species. Within the <i>C. kelleri</i>-group, three new species are described: <i>C. hazolava</i> Blaimer <b>sp. n.</b>, <i>C. hafahafa</i> Blaimer <b>sp. n.</b> and <i>C. tavaratra</i> Blaimer <b>sp. n.</b> The previously described taxa <i>C. kelleri</i> Forel and <i>C. madagascariensis</i> André are validated by our analysis. Conversely, our data suggests synonymy of <i>C. adrepens</i> Forel (with <i>C. kelleri</i>) and <i>C. gibba</i> Emery (with <i>C. madagascariensis</i>). A more distantly related and phylogenetically isolated species, <i>C. tsisitsilo</i> Blaimer <b>sp. n.</b>, is further described. We report high levels of morphological and molecular variation in <i>C. kelleri</i> and illustrate that this variation can be explained partly by geography. Species descriptions, images, distribution maps and identification keys based on worker ants, as well as on queen and male ants where available, are presented for all six species. Our work highlights the elevated species richness of <i>Crematogaster</i> ants throughout Madagascar’s humid forests, especially in the far northern tip of the island, and the need to use multiple data sources to ensure clear demarcation of this diversity.</p></div

Species-key to the <i>C. kelleri</i>-group.

<p>Postpetiole with a complete, deep, longitudinal median impression (<i>C. madagascariensis</i>, CASENT0193446).</p

<i>Crematogaster tavaratra</i>, male and distribution.

<p><b>A–C</b> male (CASENT0110524): <b>A</b> full face <b>B</b> lateral <b>C</b> dorsal; <b>D</b> species distribution.</p

<i>Crematogaster kelleri</i>, worker and queen.

<p><b>A–C</b><b> </b> worker (CASENT0060043): <b>A</b> full face <b>B</b> lateral <b>C</b> dorsal <b>D–F</b> queen (CASENT0124998) <b>D</b> full face <b>E</b> lateral <b>F</b> dorsal.</p

List of Genbank accessions.

<p>Genbank accessions of sequences included in this study. LW Rh: Long wavelength rhodopsin, ArgK: Arginine kinase, CAD: Carbomoylphosphate synthase, COI: Cytochrome oxidase I.</p

Mitochondrial phylogeny of the <i>C. kelleri</i>-group & related species.

<p>Results of Bayesian inference based on 578 bp of COI, summarized as a consensus tree in MrBayes. Support values in black represent posterior probabilities (pp), those in red ML bootstrap values, values pp<0.96 and bootstrap<60 are not shown; scalebar shows nucleotide changes per base pair. The long branch subtending outgroups <i>C. ranavalonae</i> and <i>C. madecassa</i> has been removed. Symbols beside species names on the phylogeny correspond to distribution markers in the adjacent map of Madagascar.</p

Species-key to the <i>C. kelleri</i>-group.

<p>Propodeal spiracle situated below base of propodeal spines (<i>C. tavaratra</i>, CASENT0436456).</p

Graphical plots of selected measurements of species within the <i>C. kelleri</i>-group.

<p>Based on specimen measurements as presented within species descriptions, units in mm. <b>A</b>: body size as a function of head width over Weber’s length in the <i>C. kelleri</i>-group; <b>B:</b> Propodeal spine length as a function of spine length over Weber’s length in the <i>C. kelleri</i>-group; <b>C</b>: body size as a function of head width over Weber’s length in the two forms of <i>C. kelleri</i>; <b>D</b>: Propodeal spine length as a function of spine length over Weber’s length in the two forms of <i>C. kelleri</i>.</p