Phylogeographic assessment of the northern pygmy mouse, Baiomys taylori

Abstract

The northern pygmy mouse, Baiomys taylori, occurs throughout the Trans-Mexican Volcanic Belt and southern Altiplano of central Mexico and extends northward in 3 projections into northern Mexico and the United States. We used mitochondrial DNA (from the cytochrome-b and NADH dehydrogenase 2 genes) and morphological data to assess diversity within B. taylori across its geographic range in relation to recognized subspecies and putative physiographic filter-barriers. Our results indicate 5 distinct mitochondrial clades despite little morphological variation across the species’ geographic range. The Sierra Madre Oriental and Sierra Madre Occidental separate clades representing the eastern (Gulf coastal lowlands), central (Altiplano), and Pacific coastal lowlands, which appear to be divided into 3 major mitochondrial clades. Based on a preliminary analysis of cranial morphology, we are able to reject the Balcones Escarpment of Texas as an impediment to the well-documented recent northern expansion of the species, while we are unable to reject a causal role of filter-barriers elsewhere in subspecific differentiation. Revision of subspecific taxonomy must await further genetic sampling, particularly along the western and southeastern portions of the species’ distribution. El ratón pigmeo norteño, Baiomys taylori, se distribuye a través del Eje Volcánico Transmexicano y la parte sur del Altiplano del centro de México y se extiende hacia el norte de México y los Estados Unidos en tres direcciones. Utilizamos ADN mitocondrial (del citocromo-b y del gen NADH deshidrogenasa) y datos morfológicos para evaluar la diversidad dentro de B. taylori a través de su rango geográfico en relación con las subespecies reconocidas y las supuestas barreras-filtro fisiográficas. Nuestros resultados indican 5 clados mitocondriales distintos a pesar de la escasa variación morfológica a lo largo de su rango geográfico. La Sierra Madre Oriental y la Sierra Madre Occidental separan los clados representantes de las tierras bajas del este (tierras bajas del Golfo), del centro (Altiplano), y las tierras bajas del Pacífico, que parecen estar divididas en 3 clados mitocondriales principales. Basados en un análisis preliminar de la morfología craneal, pudimos rechazar el Escarpe de Balcones de Texas como un impedimento a la bien documentada expansión norteña de la especie, mientras que no fue posible rechazar el rol causal de las otras barreras-filtro en la diferenciación subespecífica. La revisión de la taxonomía subespecífica deberá esperar un mayor muestreo genético, en particular a lo largo de las porciones oeste y sureste de la distribución de la especie.

Pygmy mouse songs reveal anatomical innovations underlying acoustic signal elaboration in rodents

“…Animals often assume an upright posture and open their mouths widely to generate loud vocalizations (Bailey, 1931;Blair, 1941;Packard, 1960;Hooper and Carleton, 1976), which are used to attract mates and repel rivals (Campbell et al, 2019;Pasch et al, 2011Pasch et al, , 2013. Northern pygmy mice (Baiomys taylori) are crepuscular cricetid rodents that inhabit arid grasslands, coastal prairie mixed scrub, post oak savanna, and mesquite-cactus habitats from Texas to Mexico (Eshelman and Cameron, 1987;Light et al, 2016;Packard, 1960;Carleton, 1980). The staccato-like song of pygmy mice is described as a 'high-pitched, barely audible squeal' produced with the head 'thrust forward and upward, stretching the throat' (Blair, 1941).…”

Molecular and geographic evaluations of the Heteromys pictus–spectabilis species complex indicate multiple cryptic species

“…One other geographic influence to consider beyond the mountain ranges are a series of geographic filter barriers (Light et al 2016) along the Pacific lowlands of southern and western Mexico: the SBRF filter barrier (1), the Río Piaxtla (2), the Laguna Grande (3), the Laguna Agua Brava (4), the sharp transition between lowlands (5), and the deep Río Ameca canyon that splits Nayarit and Jalisco (6; Fig. 1).…”

“…(Lightly) shaded areas represent geographic barriers of note: A = Sierra Madre Occidental, B = Neovolcanic (Transvolcanic) Belt, C = Sierra Madre del Sur, and D = Isthmus of Tehauntepec. Relevant filter barriers are represented by G#: G1-the Sierra Barabampo-Río Fuerte (SRBF), G2-the Río Piaxtla, G3-the Laguna Grande, G4-the Laguna Agua Brava, G5-the sharp transition between lowland semideciduous forest and pine-oak forest, and G6-the deep Río Ameca canyon that splits Nayarit and Jalisco (Light et al 2016). The map was constructed in RStudio using the R package rnaturalearth (Massicotte and South 2023), which uses free vector and raster map data from Natural Earth (naturalearthdata.com).…”

About the specific status of Baiomys musculus and B. brunneus

“…DNA sequences were edited, aligned, and visually inspected using MeGa X (Kumar et al 2018) and FinCHTv 1.4 (Patterson et al 2004). Nineteen additional CytB sequences of B. musculus were recovered from GenBank (Amman and Bradley 2004;Miller and Engstrom 2008;Light et al 2016), so in total we analyzed 23 individuals of B. musculus (representating five subspecies: B. m. brunneus, B. m. infernatis, B. m. musculus, B. m. nigriscens, and B. m. pallidus; Figure 1) and one B. taylori individual was used as the outgroup (Appendix I).…”