Comparative mitochondrial genomics of endemic Mexican vesper yellow bats genus Rhogeessa (Chiroptera: Vespertilionidae) and insights into internal relationships in the family Vespertilionidae.

In the species-rich family Vespertilionidae, vesper yellow bats in the genus Rhogeessa include eleven species, three of them endemic to Mexico. These insectivorous bats provide important ecosystem services, including pest control. Even though some aspects of their biology are well- known, only a few genomic resources are available for these species, which limits our understanding of their biology. In this study, we assembled and annotated the mitochondrial genome of four species: R. aenea, R. genowaysi, R. mira, and R. parvula. We generated a phylomitogenomic hypothesis based on translated protein-coding genes for a total of 52 species in the family Vespertilionidae and examined the phylogenetic position of the genus Rhogeessa and species within the family. The AT-rich mitogenomes of R. aenea, R. genowaysi, R. mira, and R. parvula are 16,763, 16,781, 16,807, and 16,794 pb in length, respectively. Each studied mitogenome encodes 13 Protein Coding Genes (PCGs), 22 transfer RNA genes, and 2 rRNA genes, and contains a putative control region (CR). All tRNAs exhibit a 'cloverleaf' secondary structure, except tRNA-Serine-1 that lacked the DHU arm in all studied mitogenomes. Selective pressure analyses indicated that all protein-coding genes are exposed to purifying selection. The phylomitogenomic analysis supported the monophyletic status of the family Vespertilionidae, confirmed the placement of Rhogeessa within the tribe Antrozoini, and clarified phylogenetic relationships within and among subfamilies and tribes in this family. Our results indicate that phylomitogenomics are useful to explore the evolutionary history of vesper bats. The assembly and comprehensive analysis of mitochondrial genomes offer the potential to generate molecular references and resources beneficial for genetic analyses aimed at understanding the ecology and evolution of these remarkable bats.

Evidence of human occupation in Mexico around the Last Glacial Maximum.

The initial colonization of the Americas remains a highly debated topic1, and the exact timing of the first arrivals is unknown. The earliest archaeological record of Mexico-which holds a key geographical position in the Americas-is poorly known and understudied. Historically, the region has remained on the periphery of research focused on the first American populations2. However, recent investigations provide reliable evidence of a human presence in the northwest region of Mexico3,4, the Chiapas Highlands5, Central Mexico6 and the Caribbean coast7-9 during the Late Pleistocene and Early Holocene epochs. Here we present results of recent excavations at Chiquihuite Cave-a high-altitude site in central-northern Mexico-that corroborate previous findings in the Americas10-17of cultural evidence that dates to the Last Glacial Maximum (26,500-19,000 years ago)18, and which push back dates for human dispersal to the region possibly as early as 33,000-31,000 years ago. The site yielded about 1,900 stone artefacts within a 3-m-deep stratified sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia. More than 50 radiocarbon and luminescence dates provide chronological control, and genetic, palaeoenvironmental and chemical data document the changing environments in which the occupants lived. Our results provide new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research.

Yucatán carnivorans shed light on the Great American Biotic Interchange.

The Great American Biotic Interchange is considered to be a punctuated process, primarily occurring during four major pulses that began approximately 2.5 Ma. Central America and southeastern Mexico have a poor fossil record of this dynamic faunal history due to tropical climates. Exploration of submerged caves in the Yucatán, particularly the natural trap Hoyo Negro, is exposing a rich and remarkably well-preserved late Pleistocene fauna. Radiometric dates on megafauna range from approximately 38 400-12 850 cal BP, and extinct species include the ursid Arctotherium wingei and canid Protocyon troglodytes. Both genera were previously thought to be indigenous to and confined to South America and appear to represent an instance of large placental mammals, descended from North American progenitors, migrating back north across the Panama Isthmus. This discovery expands the distribution of these carnivorans greater than 2000 km outside South America. Their presence along with a diverse sloth assemblage suggests a more complex history of these organisms in Middle America. We suggest that landscape and ecological changes caused by latest Pleistocene glaciation supported an interchange pulse that included A. wingei, P. troglodytes and Homo sapiens.

Bite force, cranial morphometrics and size in the fishing bat Myotis vivesi (Chiroptera: Vespertilionidae)

Abstract Fish-eating in bats evolved independently in Myotis vivesi (Vespertillionidae) and Noctilio leporinus (Noctilionidae). We compared cranial morphological characters and bite force between these species to test the existence of evolutionary parallelism in piscivory. We collected cranial distances of M. vivesi, two related insectivorous bats (M. velifer and M. keaysi), two facultatively piscivorous bats (M. daubentonii and M. capaccinii), and N. leporinus. We analyzed morphometric data applying multivariate methods to test for differences among the six species. We also measured bite force in M. vivesi and evaluated if this value was well predicted by its cranial size. Both piscivorous species were morphologically different from the facultatively piscivorous and insectivorous species, and skull size had a significant contribution to this difference. However, we did not find morphological and functional similarities that could be interpreted as parallelisms between M. vivesi and N. leporinus. These two piscivorous species differed significantly in cranial measurements and in bite force. Bite force measured for M. vivesi was well predicted by skull size. Piscivory in M. vivesi might be associated to the existence of a vertically displaced temporal muscle and an increase in gape angle that allows a moderate bite force to process food.(AU)

Resumen La alimentación por peces en murciélagos evolucionó independientemente en Myotis vivesi (Vespertilionidae) y Noctilio leporinus (Phyllostomidae). En este estudio se compararon características craneales morfológicas y fuerza de mordida entre estas especies, para probar la existencia de paralelismo evolucionario en piscivoría. Se recolectaron distancias craneales en M. vivesi, dos parientes insectívoros (M. velifer y M. keaysi), dos murciélagos piscívoros facultativos (M. daubentonii y M. capaccinii), y N. leporinus. Se analizaron datos morfométricos aplicando múltiples métodos para probar las diferencias entre las seis especies. Se midió la fuerza de mordida en M. vivesi y se evalúo si puede ser predicha por el tamaño del cráneo. Las especies piscívoras fueron morfológicamente diferentes de las facultativamente piscívoras y las insectívoras, el tamaño del cráneo tuvo una contribución significativa en esta diferencia. Sin embargo, no encontramos semejanzas morfológicas y funcionales que puedan ser interpretadas como paralelismos entre M. vivesi y N. leporinus. Estas dos especies piscívoras difieren significativamente en medidas craneales y fuerza de mordida. La fuerza de mordida en M. vivesi fue efectivamente predicha por el tamaño de cráneo. La piscivoría en M. vivesi puede estar asociada con la existencia de un músculo temporal verticalmente desplazado y el incremento en el ángulo de apertura mandibular que permite moderar la fuerza de mordida para procesar el alimento.(AU)

Cambios morfológicos en la ontogenia temprana de Chirostoma riojai / Morphological changes in the early ontogeny of Chirostoma riojai

El charal de Toluca Chirostoma riojai es un pez de alto valor cultural e ictiológico. Los trabajos sobre esta especie se enfocan en el tipo de alimentación o forman parte de revisiones taxonómicas y son pocos los estudios sobre los cambios morfológicos durante su ontogenia. Se evaluó la figura de C. riojai mediante morfometría geométrica desde su eclosión hasta los 90 días de vida. Los ejemplares se cultivaron en condiciones controladas y fueron fijados 171 organismos pertenecientes a 11 intervalos de edad incluidos en cinco fases: embrión libre, apterolarva, pterolarva, juvenil y adulto. Se usaron seis puntos anatómicamente homólogos en una primera configuración de marcas y en una segunda se delinearon dos contornos (dorsal y ventralmente) de la región anterior. Un análisis de componentes principales mostró una fuerte diferenciación en su figura durante la transición larva-juvenil, en tanto un análisis de variables canónicas señaló diferencias significativas (ps<0.001) entre los 11 grupos de edad. La regresión lineal entre el logaritmo del tamaño centroide y las distancias procustes muestran que los organismos mantienen un cambio de figura constante hasta el término del periodo larvario, punto en el que el periodo juvenil comienza y las modificaciones en su figura disminuyen. La descripción del desarrollo temprano de C. riojai sin considerar el desarrollo de las aletas, muestra que la característica con el mayor cambio es el desplazamiento del poro anal, seguido por el alargamiento de la región cefálica. El tamaño y la figura de C. riojai durante su vida temprana pueden servir para diferenciar faces de desarrollo y ser utilizada en otras especies hermanas para evaluar si su figura es específica en cada fase. Los cambios morfológicos de C. riojai durante su vida temprana se pueden describir de forma gradual hasta el periodo larval y saltatoria en el cambio a juvenil.

Toluca silverside Chirostoma riojai is a fish with high cultural and ictiological values. Studies on this species have focused on the type of diet or as part of taxonomic reviews, while few reports are known on the morphological changes during its ontogeny. In this study the shape of C. riojai was evaluated by means of geometric morphometrics from hatchings up to 90 days-old individuals. Specimens of C. riojai were cultivated in controlled conditions, and 171 organisms there fixed, belonging to 11 age intervals included within five phases: free embryo, apterolarva, pterolarva, juvenile, and adult. There were used six landmarks in an initial configuration, and in a second configuration there were outlined two contours (dorsal and ventral) on the anterior region. A principal component analysis showed a strong differentiation in the shape during the transition larva-juvenile, for both an analysis of canonical variables found significant differences (ps<0.001) between the 11 age groups. The linear regression between the logarithm of the size centroid and procustes distances, showed that the individuals maintain a constant change in shape up to the end of the larval phase, at which time the youth stage begins and the changes in its shape decreases. The description of the early development of C. riojai without considering the development of the fins, shows that feature with greatest change is the movement of the anal pore, followed by the lengthening of the cephalic region. The size and shape of C. riojai during its early life could serve to differentiate developmental phases and could be used with other sister species to assess whether their shape is specific in each phase. The morphological changes of C. riojai during his early life could be described in a gradual form up to the the larval period, while saltatory in the change to juvenile.

Human (Clovis)-gomphothere (Cuvieronius sp.) association ∼ 13,390 calibrated yBP in Sonora, Mexico.

The earliest known foragers to populate most of North America south of the glaciers [∼ 11,500 to ≥ ∼ 10,800 (14)C yBP; ∼ 13,300 to ∼ 12,800 calibrated (Cal) years] made distinctive "Clovis" artifacts. They are stereotypically characterized as hunters of Pleistocene megamammals (mostly mammoth) who entered the continent via Beringia and an ice-free corridor in Canada. The origins of Clovis technology are unclear, however, with no obvious evidence of a predecessor to the north. Here we present evidence for Clovis hunting and habitation ∼ 11,550 yBP (∼ 13,390 Cal years) at "El Fin del Mundo," an archaeological site in Sonora, northwestern Mexico. The site also includes the first evidence to our knowledge for gomphothere (Cuvieronius sp.) as Clovis prey, otherwise unknown in the North American archaeological record and terminal Pleistocene paleontological record. These data (i) broaden the age and geographic range for Clovis, establishing El Fin del Mundo as one of the oldest and southernmost in situ Clovis sites, supporting the hypothesis that Clovis had its origins well south of the gateways into the continent, and (ii) expand the make-up of the North American megafauna community just before extinction.

Ancient DNA and the tropics: a rodent's tale.

Most genetic studies of Holocene fauna have been performed with ancient samples from dry and cold regions, in which preservation of fossils is facilitated and molecular damage is reduced. Ancient DNA work from tropical regions has been precluded owing to factors that limit DNA preservation (e.g. temperature, hydrolytic damage). We analysed ancient DNA from rodent jawbones identified as Ototylomys phyllotis, found in Holocene and Late Pleistocene stratigraphic layers from Loltún, a humid tropical cave located in the Yucatan peninsula. We extracted DNA and amplified six short overlapping fragments of the cytochrome b gene, totalling 666 bp, which represents an unprecedented success considering tropical ancient DNA samples. We performed genetic, phylogenetic and divergence time analyses, combining sequences from ancient and modern O. phyllotis, in order to assess the ancestry of the Loltún samples. Results show that all ancient samples fall into a unique clade that diverged prior to the divergence of the modern O. phyllotis, supporting it as a distinct Pleistocene form of the Ototylomys genus. Hence, this rodent's tale suggests that the sister group to modern O. phyllotis arose during the Miocene-Pliocene, diversified during the Pleistocene and went extinct in the Holocene.

Late Pleistocene human skeleton and mtDNA link Paleoamericans and modern Native Americans.

Because of differences in craniofacial morphology and dentition between the earliest American skeletons and modern Native Americans, separate origins have been postulated for them, despite genetic evidence to the contrary. We describe a near-complete human skeleton with an intact cranium and preserved DNA found with extinct fauna in a submerged cave on Mexico's Yucatan Peninsula. This skeleton dates to between 13,000 and 12,000 calendar years ago and has Paleoamerican craniofacial characteristics and a Beringian-derived mitochondrial DNA (mtDNA) haplogroup (D1). Thus, the differences between Paleoamericans and Native Americans probably resulted from in situ evolution rather than separate ancestry.

Geochronology: age of Mexican ash with alleged 'footprints'.

A report of human footprints preserved in 40,000-year-old volcanic ash near Puebla, Mexico (http://www.royalsoc.ac.uk/exhibit.asp?id=3616&tip=1), was the subject of a press conference that stirred international media attention. If the claims (http://www.mexicanfootprints.co.uk) of Gonzalez et al. are valid, prevailing theories about the timing of human migration into the Americas would need significant revision. Here we show by 40Ar/39Ar dating and corroborating palaeomagnetic data that the basaltic tuff on which the purported footprints are found is 1.30+/-0.03 million years old. We conclude that either hominid migration into the Americas occurred very much earlier than previously believed, or that the features in question were not made by humans on recently erupted ash.