Abstract: The white-footed deer mouse (Peromyscus leucopus) and the North American deer mouse (P. maniculatus) are widely distributed throughout North America, often with overlapping distributions. These species are believed to be sympatric east of the Balcones fault zone in Texas, but records from natural history collections indicate that P. maniculatus is not common from this region. Given that these two species are notoriously difficult to differentiate morphologically, it is possible that specimens have been incorrectly identified and that P. maniculatus may be rare or not present in East Texas. This study aims to determine if P. leucopus and P. maniculatus can be differentiated morphologically east of the Balcones fault zone in Texas. Cranial and external characters from genetically identified specimens representing each species were analyzed using traditional and geometric morphometric methods. Morphological analyses revealed that genetically identified specimens of P. leucopus and P. maniculatus from east of the Balcones fault zone could be differentiated using a suite of morphological characters. Many of the specimens of P. leucopus used in this study were originally misidentified, suggesting that P. maniculatus is rare in East Texas.

Resumen: El ratón ciervo de patas blancas (Peromyscus leucopus) y el ratón ciervo norteamericano (P. maniculatus) estan ampliamente distribuidos por toda Norteamérica, frecuentemente con distribuciones superpuestas. Se cree que en la región este de la falla de Balcones, Texas estas especies son simpátricas, pero los registros de su historia natural indican que P. maniculatus no es común en esta región. Debido a que estas dos especies son notoriamente difíciles de diferenciar morfológicamente, es posible que los especímenes hayan sido identificados incorrectamente y que P. maniculatus sea rara o pueda no estar presente en el este de Texas. Este estudio pretende determinar si P. leucopus y P. maniculatus pueden diferenciarse morfológicamente en la zona del este de la falla de Balcones, Texas. Los caracteres craneales y externos de especímenes identificados genéticamente que representan cada especie fueron analizados utilizando métodos morfométricos tradicionales y geométricos. Los análisis morfológicos revelaron que los especímenes genéticamente identifacados de P. leucopus y P. maniculatus del este de la zona de la falla de Balcones podrían diferenciarse utilizando un conjunto de caracteres morfológicos. Muchos de los especímenes de P. leucopus usados en este estudio fueron identificados erróneamente, lo que sugiere que P. maniculatus es raro en el este de Texas.

Aphidicolin (APC)-induced chromosomal breakage was analyzed for women representing three generations of a single family and carrying a Robertsonian translocation rob(14q21q). Fluorescence in situ hybridization (FISH) analysis confirmed the dicentric constitution of the derived chromosome and indicated the absence of beta-satellite signal at the translocation region. Per-individual analysis of metaphases from APC-treated peripheral blood lymphocyte cultures identified significantly nonrandom chromosomal breakage at the translocation region in all three individuals examined. The APC-inducible fragility at the 14q21q translocation region suggests that this rearrangement was the result of chromosomal mutation at fragile site(s) in the progenitor chromosomes, or that this fragility was the result of the fusion of nonfragile progenitor chromosomes.