The exchangeability of shape

Abstract

BackgroundLandmark based geometric morphometrics (GM) allows the quantitative comparison of organismal shapes. When applied to systematics, it is able to score shape changes which often are undetectable by traditional morphological studies and even by classical morphometric approaches. It has thus become a fast and low cost candidate to identify cryptic species. Due to inherent mathematical properties, shape variables derived from one set of coordinates cannot be compared with shape variables derived from another set. Raw coordinates which produce these shape variables could be used for data exchange, however they contain measurement error. The latter may represent a significant obstacle when the objective is to distinguish very similar species.ResultsWe show here that a single user derived dataset produces much less classification error than a multiple one. The question then becomes how to circumvent the lack of exchangeability of shape variables while preserving a single user dataset. A solution to this question could lead to the creation of a relatively fast and inexpensive systematic tool adapted for the recognition of cryptic species.ConclusionsTo preserve both exchangeability of shape and a single user derived dataset, our suggestion is to create a free access bank of reference images from which one can produce raw coordinates and use them for comparison with external specimens. Thus, we propose an alternative geometric descriptive system that separates 2-D data gathering and analyzes.

Origins of house reinfestation with Triatoma infestans after insecticide spraying in the Argentine Chaco using wing geometric morphometry

“…Each individual classification was performed on shape variables computed from the total of reference specimens plus the individual to be classified; thus, for each classification, shape variables of the reference specimens were recomputed after adding only one post-spraying individual (Dujardin et al, 2010; Dujardin & Kitthawee, 2012). When partial warps are used, the one-by-one procedure avoids distorting shape variations between reference groups.…”

Triatoma jatai sp. nov. in the state of Tocantins, Brazil (Hemiptera: Reduviidae: Triatominae)

“…According to Dujardin et al (2010), the morphometric geometric of wings allows observing conformational changes undetectable by traditional morphological methods and has been used for taxonomic identification of cryptic species in Triatominae for the genus Rhodnius (Matias et al 2001, Villegas et al 2002, Rosa et al 2012), Triatoma (Gumiel et al. 2003, Carbajal de la Fuente 2007, Carbajal de la Fuente et al 2011) and Mepraia (Campos et al 2011 ).…”

Plasmodium infections and fluctuating asymmetry among children and teenagers from Senegal

“…For each trait, the components of asymmetry were estimated in the total population (n = 107) following the methodology of Palmer and Strobeck (1986), with the use of CLIC software (Dujardin et al, 2010). The variables showing typical FA (no directional asymmetry) were analyzed separately at the individual level and their sides differences correlated with clinical history.…”