Effect of investigator disturbance in experimental forensic entomology: succession and community composition

Abstract

Carrion insect succession studies have historically used repeated sampling of single or a few carcasses to produce data, either weighing the carcasses, removing a qualitative subsample of the fauna present, or both, on every visit over the course of decomposition and succession. This study, conducted in a set of related experimental hypotheses with two trials in a single season, investigated the effect that repeated sampling has on insect succession, determined by the number of taxa collected on each visit and by community composition. Each trial lasted at least 21 days, with daily visits on the first 14 days. Rat carcasses used in this study were all placed in the field on the same day, but then either sampled qualitatively on every visit (similar to most succession studies) or ignored until a given day of succession, when they were sampled qualitatively (a subsample) and then destructively sampled in their entirety. Carcasses sampled on every visit were in two groups: those from which only a sample of the fauna was taken and those from which a sample of fauna was taken and the carcass was weighed for biomass determination. Of the carcasses visited only once, the number of taxa in subsamples was compared to the actual number of taxa present when the carcass was destructively sampled to determine if the subsamples adequately represented the total carcass fauna. Data from the qualitative subsamples of those carcasses visited only once were also compared to data collected from carcasses that were sampled on every visit to investigate the effect of the repeated sampling. A total of 39 taxa were collected from carcasses during the study and the component taxa are discussed individually in relation to their role in succession. Number of taxa differed on only one visit between the qualitative subsamples and the actual number of taxa present, primarily because the organisms missed by the qualitative sampling were cryptic (hidden deep within body cavities) or rare (only represented by very few specimens). There were no differences discovered between number of taxa in qualitative subsamples from carcasses sampled repeatedly (with or without biomass determinations) and those sampled only a single time. Community composition differed considerably in later stages of decomposition, with disparate communities due primarily to small numbers of rare taxa. These results indicate that the methods used historically for community composition determination in experimental forensic entomology are generally adequate.

Insect succession and decomposition patterns on shaded and sunlit carrion in Saskatchewan in three different seasons

“…However, they concluded that representative insect collection from carrion does not impede the natural succession of the insects. Additionally, a subsequent study by De Jong and Hoback [18] provided further evidence that repeated sampling does not impact the qualitative assessment of the natural community of species on carrion. Thus, three pig carcasses per habitat were employed.…”

Preliminary study of insects associated to indoor body decay in Colombia

“…Studies on arthropods succession associated to outdoor animal remains decomposition are well documented in temperate regions (Anderson & VanLaerhoven 1996;Arnaldos et al 2001;Grassberger & Frank 2004;Tabor et al 2005;De Jong & Hoback 2006), as well as for the Neotropical region (Jirón et al 1982;Moura et al 1997;Cruz & Vasconcelos 2006;, Carvalho & Linhares 2001Iannacone 2003;Velásquez 2008;Souza et al 2008;Vasconcelos & Araujo 2012). In Colombia, studies on forensic entomology started out in 2001, and have focused mainly on patterns of decomposition in outdoor environments and aquatics conditions (Wolff et al 2001;Pérez et al 2005;Camacho 2005;Martínez et al 2007;Segura et al 2009;Grisales et al 2010;Segura et al 2011;Ramos-Pastrana & Wolff 2011;Barrios & Wolff 2011).…”

Effect of Investigator Disturbance in Experimental Forensic Entomology: Carcass Biomass Loss and Temperature

“…The methods for weighing or qualitatively sampling the fauna were identical to those used on the destructively sampled (DS) carcasses prior to collection. “W carcasses” were only weighed on every visit, the fauna from the “P carcasses” was sampled qualitatively on every visit (10,11), and the “P&W carcasses” were weighed and qualitatively sampled on every visit. P, W, and P&W carcasses were returned to their exact position on the ground after biomass measurement or collection of insects.…”

“…Student’s t ‐tests were used to compare treatments; however, because of the numerous pairwise comparisons, the Bonferroni correction factor (α/ k , where k is the number of tests to be performed) was applied when appropriate (20,30). All raw data can be found in De Jong’s thesis (10). …”

“…It has already been demonstrated that the carcass environment, including even microenvironments within the carcass, has profound effects on the succession and physiological development of the fauna (8,9). This study is part of a recent effort to examine the effects of investigator disturbance in experimental forensic entomology (10,11). …”