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Lopez-Medellin X.,National Autonomous University of Mexico | Ezcurra E.,University of California at Riverside | Gonzalez-Abraham C.,San Diego Natural History Museum | Hak J.,NatureServe | And 2 more authors.
Journal of Vegetation Science | Year: 2011

Question: Although mangrove forests are generally regarded as highly threatened, some studies have shown that mangrove canopies in the Pacific coast of Mexico have been increasing in recent decades. We investigated the possible causes driving this reported mangrove expansion. Location: The mangrove lagoons of Magdalena Bay in Baja California, Mexico. Methods: We used 50-year-old aerial photographs and 24-year-old satellite images to compare long-term vegetation change, surveyed a coastal vegetation transect to analyse flooding levels, compiled six decades of tidal and oceanographic information, as well as hurricane data to analyse changes in storm frequency or sea-level conditions, and used isotopic analysis to date the age of trees along the gradient. Results: A significant increase in mangrove cover has occurred in backwaters of the lagoons during the last 40 years, and especially during the El Niño anomalies of the 1980s and 1990s, while at the same time the mangrove fringe has been receding. Conclusions: The observed change can be attributed to the combined action of the warm surface waters of El Niño events and sea-level rise. Jointly, these two effects are sufficient to flood large areas of previously non-flooded salt flats, dispersing mangrove seedlings inland. The inland expansion of mangroves, however, does not ease conservation concerns, as it is the seaward fringes, and not the inland margins, that provide the most valuable environmental services for fisheries and coastal protection. © 2011 International Association for Vegetation Science. Source

Racicot R.A.,Yale University | Demere T.A.,San Diego Natural History Museum | Boessenecker R.W.,University of Otago | Boessenecker R.W.,University of California at Berkeley
Current Biology | Year: 2014

Modern porpoises (Odontoceti: Phocoenidae) are some of the smallest cetaceans and usually feed near the seafloor on small fish and cephalopods [1-3]. Within both extinct and extant phocoenids, no evidence for specialized mandibular morphology has been documented [4-7]. Here we describe a new species of extinct porpoise, Semirostrum ceruttii, from the marine Pliocene San Diego (4.2-1.6 mega-annum, Ma) and Purisima (5-2.5 Ma) formations of California. The mandibles comprise a long, fused, and nearly edentulous prognathous symphysis, extending farther beyond the rostrum than in any known mammal. Phylogenetic analyses based on morphology reconstruct Semirostrum ceruttii as sister to extant (crown) porpoise species with moderate support. We describe the spectacularly preserved holotype specimen based on computed tomography (CT) scans, which allowed visualization of the elongate mental and accessory canals within the symphysis. The elongate canals are similar to those found in Rynchops birds [8] and were likely involved in sensory function. Oblique labial wear facets present on numerous small conical mandibular teeth posterior to the symphysis suggest regular contact with benthic substrate. The unique mandibular and dental characteristics, along with robust scapulae, sternum, and unfused cervical vertebrae, support the interpretation that this species employed a form of benthic skim feeding by using its mandible to probe for and obtain prey. © 2014 Elsevier Ltd. Source

The genus Aseptis McDunnough (Lepidoptera, Noctuidae, Noctuinae, Xylenini, Xylenina) is revised to include 15 species based on morphological and molecular data. Several new synonymies are introduced. In addition, two genera are described because of significant morphological differences from Aseptis: Paraseptis gen. n., and Viridiseptis gen. n., resulting in the new combinations Paraseptis adnixa (Grote), comb. n., and Viridiseptis marina (Grote), comb. n. Although this work is primarily based on morphological data, DNA sequence data for the 658-base pair "barcode" segment of the mitochondrial gene for subunit 1 of cytochrome c oxidase was used as a secondary support for taxonomic changes within Aseptis and for the two new genera. Our work should provide clarity and stability in a previously difficult genus. © Tomas Mustelin, Lars G. Crabo. Source

Bisconti M.,San Diego Natural History Museum | Bosselaers M.,Royal Belgian Institute Of Natural Sciences
Zoological Journal of the Linnean Society | Year: 2016

A new extinct genus, Fragilicetus gen. nov., is described here based on a partial skull of a baleen-bearing whale from the Early Pliocene of the North Sea. Its type species is Fragilicetus velponi sp. nov. This new whale shows a mix of morphological characters that is intermediate between those of Eschrichtiidae and those of Balaenopteridae. A phylogenetic analysis supported this view and provided insights into some of the morphological transformations that occurred in the process leading to the origin of Balaenopteridae. Balaenopterid whales show specialized feeding behaviour that allows them to catch enormous amounts of prey. This behaviour is possible because of the presence of specialized anatomical features in the supraorbital process of the frontal, temporal fossa, glenoid fossa of the squamosal, and dentary. Fragilicetus velponi gen. et sp. nov. shares the shape of the supraorbital process of the frontal and significant details of the temporal fossa with Balaenopteridae but maintains an eschrichtiid- and cetotheriid-like squamosal bulge and posteriorly protruded exoccipital. The character combination exhibited by this cetacean provides important information about the assembly of the specialized morphological features responsible for the highly efficient prey capture mechanics of Balaenopteridae. © 2016 The Linnean Society of London. Source

Devitt T.J.,University of California at Berkeley | Devitt T.J.,University of Florida | Devitt S.E.C.,Ziegler | Hollingsworth B.D.,San Diego Natural History Museum | And 2 more authors.
Molecular Ecology | Year: 2013

Understanding the biotic consequences of Pleistocene range shifts and fragmentation remains a fundamental goal in historical biogeography and evolutionary biology. Here, we combine species distribution models (SDM) from the present and two late Quaternary time periods with multilocus genetic data (mitochondrial DNA and microsatellites) to evaluate the effect of climate-induced habitat shifts on population genetic structure in the Large-blotched Ensatina (Ensatina eschscholtzii klauberi), a plethodontid salamander endemic to middle and high-elevation conifer forest in the Transverse and Peninsular Ranges of southern California and northern Baja California. A composite SDM representing the range through time predicts two disjunct refugia, one in southern California encompassing the core of the species range and the other in the Sierra San Pedro Mártir of northern Baja California at the southern limit of the species range. Based on our spatial model, we would expect a pattern of high connectivity among populations within the northern refugium and, conversely, a pattern of isolation due to long-term persistence of the Sierra San Pedro Mártir population. Our genetic results are consistent with these predictions based on the hypothetical refugia in that (i) historical measures of population connectivity among stable areas are correlated with gene flow estimates; and (ii) there is strong geographical structure between separate refugia. These results provide evidence for the role of recent climatic change in shaping patterns of population persistence and connectivity within the Transverse and Peninsular Ranges, an evolutionary hotspot. © 2013 Blackwell Publishing Ltd. Source

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