Multivariate analysis applied to morphological parameters in wild rodents / Tecniche statistiche di analisi multivariata applicate su parametri morfologici rilevati in Roditori selvatici

<strong>Abstract</strong> Several techniques in multivariate analysis were applied in concert to evaluate the environmental impact by means of biological indicators (Murine Rodents). Morphometric and epigenetic characters, especially of the skull, have been recorded bilaterally in order to detect possible alterations in the homeostatic mechanisms of development. To this purpose, 120 murines have been captured in three different sites (Due Ponti Tevere, Colleferro, Palombara Sabina); 12 morphometric (quantitative) variables and 15 epigenetic (qualitative) characters have been considered. The first set of variables has been analyzed by a sequence of one-way and two-way analysis of variance. Subsequently these characters have been classified firstly into two groups (asymmetry, symmetry) and then in three (left asymmetry, symmetry, right asymmetry). The qualitative characters were classified into four groups (left ill-formed/right ill-formed; left ill-formed/right regular; left regular/right ill-formed; left regular/right regular). The logit linear and the log-linear models have been applied in order to investigate on their dependence upon the stratification factor (Locality) and the structural variables (Species, Age, Sex). Finally, the entire set of epigenetic and morphometric variables (these were recorded in five levels of asymmetry) has been studied by means of multiple correspondence analysis, considering the stratification and structural factors as supplementary variables in the same analysis. The presence of a "noise" in the fenetic homeostasis stands out from statistical results especially in Palombara Sabina, an area subjected to agricultural impact. The combined utilization of these techniques defines a "strategy of analysis" which turned out to be very fruitful in environmental surveys. <strong>Riassunto</strong> Al fine delle valutazioni di impatto ambientale tramite indicatori biologici (Rodentia, Murinae) vengono introdotte differenti tecniche di analisi multivariata allo scopo di individuare metodologie statistiche da impiegare nello studio morfologico. In particolare sui crani degli esemplari sono stati rilevati bilateralmente caratteri morfometrici ed epigenetici allo scopo di evidenziare eventuali alterazioni controlaterali del normale equilibrio omeostatico imputabili a stress ambientati (località) o ad altre cause strutturali (specie, età, sesso). Sono stati catturati 120 Murini in tre località differenti (Due Ponti Tevere, Colleferro, Palombara Sabina) su cui sono state rilevate 12 variabili morfometriche (quantitative) e 15 variabili epigenetiche (qualitative). La matrice delle variabili è stata analizzata tramite l'Analisi della varianza ad 1 e 2 vie, il Modello logistico ed il Modello 1og-lineare. Infine è stato studiato l'intero insieme delle variabili morfometriche ed epigenetiche attraverso l'Analisi delle corrispondenze multiple. Dai risultati statistici emerge la presenza di disturbi sull'omeostasi fenetica riscontrati soprattutto in località Palombara Sabina, interessata da impatto di origine agricola