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171.
172.
Gualberto Pacheco‐Sierra Zachariah Gompert Jerónimo Domínguez‐Laso Ella Vázquez‐Domínguez 《Molecular ecology》2016,25(14):3484-3498
Hybrid zones represent natural laboratories to study gene flow, divergence and the nature of species boundaries between closely related taxa. We evaluated the level and extent of hybridization between Crocodylus moreletii and Crocodylus acutus using genetic and morphological data on 300 crocodiles from 65 localities. To our knowledge, this is the first genetic study that includes the entire historic range and sympatric zone of the two species. Contrary to expectations, Bayesian admixture proportions and maximum‐likelihood estimates of hybrid indexes revealed that most sampled crocodiles were admixed and that the hybrid zone is geographically extensive, extending well beyond their historical region of sympatry. We identified a few geographically isolated, nonadmixed populations of both parental species. Hybrids do not appear to be F1s or recent backcrosses, but rather are more likely later‐generation hybrids, suggesting that hybridization has been going on for several to many generations and is mostly the result of natural processes. Crocodylus moreletii is not the sister species of C. acutus, suggesting that the hybrid zone formed from secondary contact rather than primary divergence. Nonadmixed individuals from the two species were distinguishable based on morphological characters, whereas hybrids had a complex mosaic of morphological characters that hinders identification in the wild. Very few nonadmixed C. acutus and C. moreletii populations exist in the wild. Consequently, the last nonadmixed C. moreletii populations have become critically endangered. Indeed, not only the parental species but also the naturally occurring hybrids should be considered for their potential conservation value. 相似文献
173.
Aragonite infill in overgrown conceptacles of coralline Lithothamnion spp. (Hapalidiaceae,Hapalidiales, Rhodophyta): new insights in biomineralization and phylomineralogy
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Sherry Krayesky‐Self Joseph L. Richards Mansour Rahmatian Suzanne Fredericq 《Journal of phycology》2016,52(2):161-173
New empirical and quantitative data in the study of calcium carbonate biomineralization and an expanded coralline psbA framework for phylomineralogy are provided for crustose coralline red algae. Scanning electron microscopy (SEM) and energy dispersive spectrometry (SEM‐EDS) pinpointed the exact location of calcium carbonate crystals within overgrown reproductive conceptacles in rhodolith‐forming Lithothamnion species from the Gulf of Mexico and Pacific Panama. SEM‐EDS and X‐ray diffraction (XRD) analysis confirmed the elemental composition of these calcium carbonate crystals to be aragonite. After spore release, reproductive conceptacles apparently became overgrown by new vegetative growth, a strategy that may aid in sealing the empty conceptacle chamber, hence influencing the chemistry of the microenvironment and in turn promoting aragonite crystal growth. The possible relevance of various types of calcium carbonate polymorphs present in the complex internal structure and skeleton of crustose corallines is discussed. This is the first study to link SEM, SEM‐EDS, XRD, Microtomography and X‐ray microscopy data of aragonite infill in coralline algae with phylomineralogy. The study contributes to the growing body of literature characterizing and speculating about how the relative abundances of carbonate biominerals in corallines may vary in response to changes in atmospheric pCO2, ocean acidification, and global warming. 相似文献
174.
Katherine R. Gould 《Brittonia》1999,51(4):407-414
During a revisionary study ofSpigelia, three new species from Mexico were discovered. Two of these new species appear to be narrow endemics, one in the state of
Chiapas and one in the state of Guerrero, and the third is more widespread in Mexico and Guatemala. These new species are
described, illustrated, and distinguished from other North AmericanSpigelias. 相似文献
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Molting phenology of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the Baja California Peninsula,Mexico
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Claudia Tapia‐Harris Gisela Heckel Yolanda Schramm Eva María Fernández‐Martín 《Marine Mammal Science》2017,33(3):817-829
We document and compare the annual molt of the Pacific harbor seal (Phoca vitulina richardii) on two islands off the west coast of the Baja California Peninsula that are the northern and southern extremes of its distribution in Mexico. During 2014, observations were made from March to July on Todos Santos Island (northern extreme) and from January to June on San Roque Island (southern extreme). On Todos Santos, the premolt lasted 15 wk (March–June) and the molt 12 wk (April–July). On San Roque, the premolt lasted 22 wk (January–June) and the molt 17 wk (February–June). The proportion of seals undergoing molt peaked on 26 May on Todos Santos and on 7 June on San Roque. Shedding of old hair most commonly initiated on the torso and progressed to the head and flippers (reverse molting pattern). The period when the highest number of harbor seals haul out in Mexico is in late April on the more southerly islands and in early May on the more northerly islands, when a large proportion of seals are in premolt. 相似文献
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Astragalus mario-sousae is described from the central part of state of Nuevo León, Mexico. It differs fromAstragalus esperanzae by its habit, peduncles, pedicels, and fruits.
Resumen Astragalus mario-sousae (Fabaceae: Galegeae), a new species from northeastern Mexico. Brittonia 57: 314–319. 2005.—Astragalus mario-sousae es propuesta como especie nueva. Se conoce solo de la porción central del estado mexicano de Nuevo León. Se presentan una descripción e ilustración. Difiere deAstragalus esperanzae por su hábito erecto, pedúnculos, pedicelos y frutos más cortos.相似文献
180.
Eric J. Berry David L. Gorchov Bryan A. Endress Martin Henry H. Stevens 《Population Ecology》2008,50(1):63-77
Site factors have frequently been shown to affect survival, growth, and reproduction in plant populations. The source-sink
concept proposed by Pulliam is one way of integrating this spatial demographic variation into population models. Source-sink
models describe a population where propagules from “source” habitats sustain less productive “sink” areas. We adapted this
concept to model the population dynamics of the understory palm Chamaedorea radicalis on two substrates, rock outcrops and forest floor. In our model, sources and sinks correspond to fine-scale demographic structure
within the population, rather than spatially discrete subpopulations as described in the Pulliam model. We constructed a stage-structured
population matrix model that integrates the site-specific demography of individuals across two habitats types that are linked
by migration. We then parameterized this model with field data from C. radicalis. To address whether observed differences in palm demography between rock outcrops and the forest floor were due to natural
variation between microsites or due to differences in browsing intensity from free range livestock, we parameterized separate
models based on the substrate-specific demography of protected, non-browsed palms and of palms exposed to burro browse. Results
showed that herbivory reduced survival and fecundity on the forest floor, which in the absence of seed migration resulted
in a projected decline of forest floor palms (sinks). However with seed dispersal, palms persisted and total population growth
(both substrates) was projected to be positive, indicating that seed dispersal from non-browsed palms on rock outcrops (sources)
was sufficient to sustain C. radicalis on the forest floor. 相似文献