Species delimitation: a case study in a problematic ant taxon.

Department of Entomology, University of Georgia, Athens, GA 30602, USA.
Systematic Biology (Impact Factor: 11.53). 03/2010; 59(2):162-84. DOI: 10.1093/sysbio/syp089
Source: PubMed

ABSTRACT Species delimitation has been invigorated as a discipline in systematics by an influx of new character sets, analytical methods, and conceptual advances. We use genetic data from 68 markers, combined with distributional, bioclimatic, and coloration information, to hypothesize boundaries of evolutionarily independent lineages (species) within the widespread and highly variable nominal fire ant species Solenopsis saevissima, a member of a species group containing invasive pests as well as species that are models for ecological and evolutionary research. Our integrated approach uses diverse methods of analysis to sequentially test whether populations meet specific operational criteria (contingent properties) for candidacy as morphologically cryptic species, including genetic clustering, monophyly, reproductive isolation, and occupation of distinctive niche space. We hypothesize that nominal S. saevissima comprises at least 4-6 previously unrecognized species, including several pairs whose parapatric distributions implicate the development of intrinsic premating or postmating barriers to gene flow. Our genetic data further suggest that regional genetic differentiation in S. saevissima has been influenced by hybridization with other nominal species occurring in sympatry or parapatry, including the quite distantly related Solenopsis geminata. The results of this study illustrate the importance of employing different classes of genetic data (coding and noncoding regions and nuclear and mitochondrial DNA [mtDNA] markers), different methods of genetic data analysis (tree-based and non-tree based methods), and different sources of data (genetic, morphological, and ecological data) to explicitly test various operational criteria for species boundaries in clades of recently diverged lineages, while warning against over reliance on any single data type (e.g., mtDNA sequence variation) when drawing inferences.

Download full-text


Available from: Marina S Ascunce, Jun 30, 2015
1 Follower
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: DNA barcoding has emerged as a routine tool in modern taxonomy. Although straightforward, this approach faces new challenges, when applied to difficult situation such as defining cryptic biodiversity. Ants are prime examples for high degrees of cryptic biodiversity due to complex population differentiation, hybridization and speciation processes. Here, we test the DNA barcoding region, cytochrome c oxidase 1 and two supplementary markers, 28S ribosomal DNA and long-wavelength rhodopsin, commonly used in ant taxonomy, for their potential in a layered, character-based barcoding approach across different taxonomic levels. Furthermore, we assess performance of the character-based barcoding approach to determine cryptic species diversity in ants. We found (i) that the barcode potential of a specific genetic marker varied widely among taxonomic levels in ants; (ii) that application of a layered, character-based barcode for identification of specimens can be a solution to taxonomical challenging groups; (iii) that the character-based barcoding approach allows us to differentiate specimens even within locations based on pure characters. In summary, (layered) character-based barcoding offers a reliable alternative for problematic species identification in ants, and can be used as a fast and cost-efficient approach to estimate presence, absence or frequency of cryptic species. This article is protected by copyright. All rights reserved.
    Molecular Ecology Resources 02/2015; DOI:10.1111/1755-0998.12395 · 5.63 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A small minority of the presently recognized ∼12,500 species of ants are slave-makers, which permanently depend on the help of “slave workers,” that is workers of other ant species, which they pillage as brood from their nests in well-organized slave raids. The genus Myrmoxenus is one of the most species-rich taxa of slave-making ants, but individual species are often not well-delimited. Here, we compare behavior, morphometry, and nuclear and mtDNA sequences between two taxa of Myrmoxenus: Myrmoxenus tamarae (Arnoldi, 1968), known only from its type locality in Georgia, and the wide-spread M. ravouxi (André, 1896) to determine if the former might simply represent a Caucasian variant of the latter. Workers of the two taxa differed clearly in locomotor activity and slightly also in morphometry, while genetic investigations with nuclear and mitochondrial genes revealed only a weak differentiation. Given that Myrmoxenus appears to be a genus with a relatively recent radiation, we suggest to conservatively keep the present taxonomic situation with M. ravouxi and M. tamarae as separate species. The latter would then include specimens from Eastern Turkey and probably also Ukraine. Further studies, in particular in Greece and Turkey, might help to clarify the status of these endangered ants.
    Organisms Diversity & Evolution 09/2014; 14(3):259-267. DOI:10.1007/s13127-014-0174-6 · 3.37 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Species from the Solenopsis saevissima (Smith) (Hymenoptera: Formicidae) species group are native to South America and have a cosmopolitan distribution because they have been accidentally introduced in many countries around the world. In Brazil, they have a wide distribution, including urban areas. The present study was conducted to investigate the characterization of Solenopsis genus populations associated with urban/human interference sites in Brazil by analyzing the mitochondrial gene cytochrome oxidase I and estimating the degree of relatedness of these populations to make inferences about their phylogeny and also observe the patterns of mitochondrial haplotype (mitotype) distribution across their range. The results revealed complete geographical coherence and polyphyly for the Solenopsis invicta Buren and Solenopsis saevissima species groups, which confirms the diversity of the genera. It also suggests the possibility that reproductively-isolated populations occur, resulting in the evolutionary process of speciation. No predominant haplotype was found in the populations analyzed, but some were more prevalent
    Journal of Insect Science 04/2014; 14:1-17. DOI:10.1093/jis/14.1.50 · 0.92 Impact Factor