Model type, predictor variables, Deviance Information Criteria (DIC), ΔDIC, and DIC weights () for the candidate set of logistic regression models relating misidentification of sex with personal background information.

<p>DIC is a measure of model fit, ΔDIC measures the relative difference between the best model (ΔDIC = 0) and all subsequent models in the model set, and is the relative likelihood of a model given the data.</p

Summary of misidentification rates by personal background information, sex of specimen, and location of where the survey was administered.

<p>N (number of observers), median, min, max, and 25th and 75^th percentile summarize the central tendency and spread of misidentification rates per background information trait.</p

Biplots from principal component analysis (PCA) of traditional morphometrics.

<p>(A), geometric morphometrics (B), and Fourier morphometrics (C). Colors and shapes of points correspond to females (black circle; <i>n</i> = 44) and males (gray diamond; <i>n</i> = 61) of <i>Lampsilis teres</i> (Yellow Sandshell) from Yegua Creek and the East Fork of the Trinity River. Polygons enclose convex hulls of each sex (solid line = females; dashed line = males).</p

Flow chart exploring pros and cons of different approaches to determine sex for mussels as it relates to time, effort, lethality, and accuracy.

<p>Note that Geometric or Fourier morphometrics have similar accuracy as gonadal fluid sampling but requires more effort.</p

Biplot from principal component analysis (PCA) of Fourier morphometrics.

<p>Shapes of points correspond to female (circle; <i>n</i> = 20) and males (diamond; <i>n</i> = 30) of <i>Lampsilis teres</i> (Yellow Sandshell) from Yegua Creek; gradient colors correspond to observer misidentification rates for each specimen. Polygons enclose convex hulls of each sex (solid line = females; dashed line = males). Outlined shell shapes represent a mean shape (top-right) and ± 2 × standard deviations on PC1 and PC2 axes.</p

Parameter estimates, standard errors (SE), 95% highest posterior probability density (95% HPD) intervals, odds ratios (OR), and median odd ratios (MOR) based on logistic regression models relating misidentification of sex with personal background information.

<p>Parameter estimates, standard errors (SE), 95% highest posterior probability density (95% HPD) intervals, odds ratios (OR), and median odd ratios (MOR) based on logistic regression models relating misidentification of sex with personal background information.</p

Misidentification of sex for <i>Lampsilis teres</i>, Yellow Sandshell, and its implications for mussel conservation and wildlife management

<div><p>Correct identification of sex is an important component of wildlife management because changes in sex ratios can affect population viability. Identification of sex often relies on external morphology, which can be biased by intermediate or nondistinctive morphotypes and observer experience. For unionid mussels, research has demonstrated that species misidentification is common but less attention has been given to the reliability of sex identification. To evaluate whether this is an issue, we surveyed 117 researchers on their ability to correctly identify sex of <i>Lampsilis teres</i> (Yellow Sandshell), a wide ranging, sexually dimorphic species. Personal background information of each observer was analyzed to identify factors that may contribute to misidentification of sex. We found that median misidentification rates were ~20% across males and females and that observers falsely identified the number of female specimens more often (~23%) than males (~10%). Misidentification rates were partially explained by geographic region of prior mussel experience and where observers learned how to identify mussels, but there remained substantial variation among observers after controlling for these factors. We also used three morphometric methods (traditional, geometric, and Fourier) to investigate whether sex could be more correctly identified statistically and found that misidentification rates for the geometric and Fourier methods (which characterize shape) were less than 5% (on average 7% and 2% for females and males, respectively). Our results show that misidentification of sex is likely common for mussels if based solely on external morphology, which raises general questions, regardless of taxonomic group, about its reliability for conservation efforts.</p></div