Integrative taxonomy, or iterative taxonomy?

Abstract

Abstract. The recently introduced term 'integrative taxonomy' refers to taxonomy that integrates all available data sources to frame species limits. We survey current taxonomic methods available to delimit species that integrate a variety of data, including molecular and morphological characters. A literature review of empirical studies using the term 'integrative taxonomy' assessed the kinds of data being used to frame species limits, and methods of integration. Almost all studies are qualitative and comparative -we are a long way from a repeatable, quantitative method of truly 'integrative taxonomy'. The usual methods for integrating data in phylogenetic and population genetic paradigms are not appropriate for integrative taxonomy, either because of the diverse range of data used or because of the special challenges that arise when working at the species/population boundary. We identify two challenges that, if met, will facilitate the development of a more complete toolkit and a more robust research programme in integrative taxonomy using species tree approaches. We propose the term 'iterative taxonomy' for current practice that treats species boundaries as hypotheses to be tested with new evidence. A search for biological or evolutionary explanations for discordant evidence can be used to distinguish between competing species boundary hypotheses. We identify two recent empirical examples that use the process of iterative taxonomy.

Species detection and individual assignment in species delimitation: can integrative data increase efficacy?

“…Variance is exemplified in non-metric multidimensional scaling (NMDS) plots between species pairs using different data-types (see electronic supplementary material, figure S3). A taxonomic approach was used to a priori define species whereby genetic (mtDNA lineages), geographical, morphological and ecological data are qualitatively combined to distinguish species [8]. This approach is hereafter termed traditional taxonomic criteria (TTC), as it is a common integrative approach used to delimit and formally describe species.…”

“…This approach can then be combined with coalescent-based tests of species boundaries [12], but specifically focuses on improving: (i) species detection and individual assignment and (ii) the cohesiveness between species discovery and description. We compare this method using various amounts of integrated data for species detection and individual assignment using: (i) a genetic clustering approach [23] and (ii) a qualitative, integrative traditional taxonomic framework [8]. We test these comparisons in an empirical system comprising 11 Australian amphibolurine lizard species (Ctenophorus maculatus complex (Squamata: Agamidae)).…”

Assessing species boundaries and the phylogenetic position of the rare Szechwan ratsnake, Euprepiophis perlaceus (Serpentes: Colubridae), using coalescent-based methods

“…molecular, morphological, ecological, and behavioral) for taxonomy is expected to reduce subjectivity in delimiting taxa (Dayrat, 2005;Leaché et al, 2009;Padial et al, 2010;Schlick-Steiner et al, 2010;Yeates et al, 2011). However, in situations where cryptic species with indistinct morphological and ecological properties are present, integrative methods will not yield a clear result since different types of data may yield discordant conclusions (Fujita et al, 2012;Wiens and Penkrot, 2002).…”

A newly recognised species that has been confused with the global polyphagous pest scale insect, Coccus hesperidum Linnaeus (Hemiptera: Coccomorpha: Coccidae)

“…Although implementing different species concepts to delineate species could affect the number of species recognised, very few taxonomists have reported which species concept they use (Yeates et al 2011). The use of the biological species concept (BSC) (Mayr 1942) might be inappropriate for this group of scale insects because they are thought to be mostly asexual and there is no direct evidence for their reproducing sexually.…”