Exceptionally preserved North American Paleogene metatherians: adaptations and discovery of a major gap in the opossum fossil record

A major gap in our knowledge of the evolution of marsupial mammals concerns the Paleogene of the northern continents, a critical time and place to link the early history of metatherians in Asia and North America with the more recent diversification in South America and Australia. We studied new exceptionally well-preserved partial skeletons of the Early Oligocene fossil Herpetotherium from the White River Formation in Wyoming, which allowed us to test the relationships of this taxon and examine its adaptations. Herpetotheriidae, with a fossil record extending from the Cretaceous to the Miocene, has traditionally been allied with opossums (Didelphidae) based on fragmentary material, mainly dentitions. Analysis of the new material reveals that several aspects of the cranial and postcranial anatomy, some of which suggests a terrestrial lifestyle, distinguish Herpetotherium from opossums. We found that Herpetotherium is the sister group to the crown group Marsupialia and is not a stem didelphid. Combination of the new palaeontological data with molecular divergence estimates, suggests the presence of a long undocumented gap in the fossil record of opossums extending some 45Myr from the Early Miocene to the Cretaceous.     

Comparative Endocranial Anatomy,Encephalization, and Phylogeny of Notoungulata (Placentalia,Mammalia)

Journal of Mammalian Evolution - Cranial endocasts are one of the most direct tools available to obtain information about the endocranial cavity of fossil mammals, but few anatomical comparisons...     

Genome based identification and analysis of the pre-replicative complex of Arabidopsis thaliana

Eukaryotic DNA replication requires an ordered and regulated machinery to control G1/S transition. The formation of the pre-replicative complex (pre-RC) is a key step involved in licensing DNA for replication. Here, we identify all putative components of the full pre-RC in the genome of the model plant Arabidopsis thaliana. Different from the other eukaryotes, Arabidopsis houses in its genome two putative homologs of ORC1, CDC6 and CDT1. Two mRNA variants of AtORC4 subunit, with different temporal expression patterns, were also identified. Two-hybrid binary interaction assays suggest a primary architectural organization of the Arabidopsis ORC, in which AtORC3 plays a central role in maintaining the complex associations. Expression profiles differ among pre-RC components suggesting the existence of various forms of the complex, possibly playing different roles during development. In addition, the expression of the putative pre-RC genes in non-proliferating plant tissues suggests that they might have roles in processes other than DNA replication licensing.     

Permanent genetic resources added to Molecular Ecology Resources Database 1 October 2011-30 November 2011

This article documents the addition of 139 microsatellite marker loci and 90 pairs of single‐nucleotide polymorphism sequencing primers to the Molecular Ecology Resources Database. Loci were developed for the following species: Aglaoctenus lagotis, Costus pulverulentus, Costus scaber, Culex pipiens, Dascyllus marginatus, Lupinus nanus Benth, Phloeomyzus passerini, Podarcis muralis, Rhododendron rubropilosum Hayata var. taiwanalpinum and Zoarces viviparus. These loci were cross‐tested on the following species: Culex quinquefasciatus, Rhododendron pseudochrysanthum Hay. ssp. morii (Hay.) Yamazaki and R. pseudochrysanthum Hayata. This article also documents the addition of 48 sequencing primer pairs and 90 allele‐specific primers for Engraulis encrasicolus.     

Quantitative Comparison of Ontogenetic and Phylogenetic Character Changes in the Synapsid Mandible and Auditory Region

The dual transformations of the post-dentary bones into sound conducting elements of the basicranium in synapsid evolutionary and developmental histories are quantitatively compared using a modified version of a previously published methodology. Sensitivity analyses were performed to test the effects of using different phylogenies and statistics. The relative sequences of discrete osteological character transformations of the mandible and auditory region compared between the ontogeny of Monodelphis domestica. the gray short-tailed opossum, and two phylogenetic hypotheses for synapsids are statistically correlated using two different tests (Spearman's R correlation and Kendall's Tau). Presumably, the characters examined in this study form a functionally integrated morphological unit that is distinct throughout evolutionary and developmental history. Assuming a von Baerian developmental pattern, the methodology discussed here could potentially be used as a test of similarity between phylogenetic hypotheses; however, further work needs to be done to test this potential.     

An intraspecific analysis of trade-offs in sprinting performance in a West Indian lizard species (Anolis lineatopus)

We examined whether a trade-off exists in sprinting ability among individuals within the Caribbean lizard Anolis lineatopus. Specifically, we made the following predictions: Longer-legged (relative to body size) individual lizards should sprint faster than shorter-legged lizards on a broad (5.1 cm diameter) rod. However, longer-legged lizards should also decline in sprinting performance to a greater extent than shorter-legged lizards when sprinting on rods of different diameters. To test these predictions, we examined morphology and sprinting performance in adult male, adult female and juvenile A. lineatopus. As predicted, longer-legged lizards are faster sprinters than shorter-legged lizards on the broad substrate, but they also decline more in speed between the broad and narrow (0.7 cm diameter) dowel. However, despite statistically significant morphological differences among intraspecific classes, differences in morphology did not result in differences in sprinting performance among intraspecific classes, with the exception that larger lizards run faster than smaller lizards on each dowel size.     

Genetic diversity of reintroduced tree populations in restoration plantations of the Brazilian Atlantic Forest

Long‐term ecological success of large‐scale restoration programs planned for the next decades will rely on genetic diversity (GD) of reintroduced or colonizing species, a limiting factor in highly fragmented landscapes. In small and isolated natural remnants or restoration areas, substantial reduction in population's size or connectivity may lead to local extinctions due to the accumulation of deleterious recessive alleles and ongoing reduction of fecundity, plant vigor, recruitment success, and adaptive potential. Despite the paramount role of GD for species persistence, its levels in restoration programs are poorly known. We assessed the GD of four model tree species (different succession stages, dispersal, and pollination syndromes) from the Brazilian Atlantic Forest, comparing two high‐diversity restoration plantations, one forest fragment and one conserved remnant. Contrary to the expectation that the plantation strategies adopted in the restoration programs could result in genetic composition homogenization, we found that restoration areas established heterogeneous genetic groups with similar levels of neutral GD and inbreeding to those observed in natural forest remnants. This pattern was consistent across the four functionally different tree species, despite some species idiosyncrasies. For instance, we observed lower allelic richness in early successional species in restoration sites, suggesting that some species may be more prone to reintroduction with lower GD. Thus, we advocate the use of high GD levels in restoration to support biodiversity conservation in human‐modified landscapes, thus reinforcing the role of ecological restoration for recovering the diversity of genes—the basic constituent of biodiversity.     

Organization of the Olfactory and Respiratory Skeleton in the Nose of the Gray Short-Tailed Opossum Monodelphis domestica

The internal nasal skeleton in Monodelphis domestica, the gray short-tailed opossum, primarily supports olfactory and respiratory epithelia, the vomeronasal organ, and the nasal gland. This scaffold is built by the median mesethmoid, and the paired vomer and ethmoid bones. The mesethmoid ossifies within the nasal septum cartilage. The bilateral ethmoid segregates respiratory and olfactory regions, and its geometry offers insight into the functional, developmental, and genomic organization of the nose. It forms through partial coalescence of separate elements known as turbinals, which in Monodelphis comprise the maxilloturbinal, nasoturbinal, five endoturbinals, and two ectoturbinals. Geometry of the ethmoid increases respiratory mucosal surface area by a factor of six and olfactory mucosal surface by nearly an order of magnitude. Respiratory epithelium warms and humidifies inspired air, recovers moisture as air is exhaled, and may help mediate brain temperature. In contrast, the olfactory skeleton functions as a series of small funnels that support growth of new olfactory neurons throughout life. Olfactory mucosa lines the mouth of each funnel, forming blind olfactory recesses known as the ethmoid cells, and neuronal axons are funneled from the epithelium through tiny olfactory foramina in the cribriform plate, into close proximity with target glomeruli in the olfactory bulb of the brain where each axon makes its first synapse. The skeleton may thus mediate topological correspondence between odorant receptor areas in the nose with particular glomeruli in the olfactory bulb, enabling growth throughout life of new olfactory neurons and proper targeting by their axons. The geometric arrangement of odorant receptors suggests that a measure of volatility may be a component in the peripheral olfactory code, and that corresponding glomeruli may function in temporal signal processing. Supporting visualizations for this study are available online at www.DigiMorph.org.