Presence, abundance and reproductive strategies of ferns in disturbed areas of Sierra Nevada, México

Diverse reproductive strategies shown by ferns and lycophytes allow them to colonize a variety of habitats, particularly after the incidence of natural or anthropogenic disturbances. This study assessed the presence, abundance and reproductive strategies of ferns growing in soils of temperate forests with different levels of disturbance at the Sierra Nevada mountain range in the State of Mexico. Vegetation, soil and environmental variables were recorded in 200 m2 permanent plots located in four forest stands. One-Way ANOVA and Canonical Correspondence Analysis resulted in the recognition of three landscape types defined by the degree of environmental alteration: low, moderate and severe. Also, from five soil samples collected in each stand, germination of ferns and lycophytes was induced. A positive relationship was found between the alteration degree and Cheilanthes abundance. Under a low landscape alteration regime, species richness is restricted to Cheilanthes bonariensis, C. marginata and Pellaea ternifolia subsp. ternifolia. The soil is a reservoir of spores of Cheilanthes and Pellaea ternifolia subsp. ternifolia because their spores can remain viable for different time intervals. Apogamy is the usual reproductive strategy of Cheilanthes species in disturbed ecosystems, although these species also show sexual reproduction in natural ecosystems with adequate water availability. Apogamy may be related to a shorter generation time in comparison with a low disturbed ecosystem. On the other hand, Pellaea ternifolia subsp. ternifolia only has sexual reproduction. Apogamy might be related to a faster generation in comparison with a low disturbed ecosystem.     

Community structure and diversity of tropical forest mammals: data from a global camera trap network

Terrestrial mammals are a key component of tropical forest communities as indicators of ecosystem health and providers of important ecosystem services. However, there is little quantitative information about how they change with local, regional and global threats. In this paper, the first standardized pantropical forest terrestrial mammal community study, we examine several aspects of terrestrial mammal species and community diversity (species richness, species diversity, evenness, dominance, functional diversity and community structure) at seven sites around the globe using a single standardized camera trapping methodology approach. The sites-located in Uganda, Tanzania, Indonesia, Lao PDR, Suriname, Brazil and Costa Rica-are surrounded by different landscape configurations, from continuous forests to highly fragmented forests. We obtained more than 51 000 images and detected 105 species of mammals with a total sampling effort of 12 687 camera trap days. We find that mammal communities from highly fragmented sites have lower species richness, species diversity, functional diversity and higher dominance when compared with sites in partially fragmented and continuous forest. We emphasize the importance of standardized camera trapping approaches for obtaining baselines for monitoring forest mammal communities so as to adequately understand the effect of global, regional and local threats and appropriately inform conservation actions.     

A nucleosome interaction module is required for normal function of Arabidopsis thaliana BRAHMA

The BRAHMA (BRM) gene encodes the SNF2-type ATPase of the putative Arabidopsis thaliana SWI/SNF chromatin remodelling complex. This family of ATPases is characterized by the presence of a conserved catalytic domain and an arrangement of auxiliary domains, whose functions in the remodelling activity remains unclear. Here, we characterize, at the molecular and functional level, the carboxy-terminal part of Arabidopsis BRM. We have found three DNA-binding regions that bind various free DNA and nucleosomal probes with different specificity. One of these regions contains an AT-hook motif. The carboxy terminus also contains a bromodomain able to bind histones H3 and H4. We propose that this array of domains constitute a nucleosome interaction module that helps BRM to interact with its substrate. We also characterize an Arabidopsis mutant that expresses a BRM protein lacking the last 454 amino acid residues (BRM-DeltaC), encompassing the bromodomain and two of the three DNA-binding activities identified. This mutant displays an intermediate phenotype between those of the wild-type and a null allele mutant, suggesting that the nucleosome interaction module is required for the normal function of BRM but it is not essential for the remodelling activity of BRM-containing SWI/SNF complexes.     

Genetic differentiation and demographic history in Drosophila pachea from the Sonoran Desert

Genetic variation at six microsatellite DNA loci and a segment of the mitochondrial cytochrome oxidase subunit I (COI) locus was used to estimate gene flow, population structure, and demographic history in the cactophilic Drosophila pachea from the Sonoran Desert of North America, a species that shows a strict association with its senita host cactus (genus Lophocereus). For microsatellite analyses, thirteen populations of D. pachea were sampled, five in mainland Mexico and the southwestern USA, and eight on the Baja California (Baja) peninsula, covering essentially the entire range of the species. Analysis of molecular variance (AMOVA) of microsatellite data revealed that populations from both the mainland and the Baja peninsula generally showed little structure, although there were a few exceptions, suggesting some local differentiation and restriction of gene flow within both regions. Pairwise comparisons of F(ST) among each of the mainland and Baja populations showed evidence of both panmixia and population subdivision. AMOVA performed on grouped populations from both the mainland and Baja, however, revealed significant partitioning of genetic variation among the two regions, but no partitioning among localities within each region. Bayesian skyline analyses of the COI data set, consisting of four mainland and seven peninsular populations, revealed population expansions dating to the Pleistocene or late Pliocene in D. pachea from both regions, although regional differences were seen in the estimated timing of the expansions and in changes in effective population size over time.     

Tailbud-derived mesenchyme promotes urinary tract segmentation via BMP4 signaling

Urinary tract morphogenesis requires the sub-division of the ureteric bud (UB) into the intra-renal collecting system and ureter, two tissues with unique structural and functional properties. In this report we investigate the cellular and molecular mechanisms that mediate their differentiation. Fate mapping experiments in the developing chick indicate that the UB is surrounded by two distinct mesenchymal populations: nephrogenic mesenchyme derived from the intermediate mesoderm and tailbud-derived mesoderm, which is selectively associated with the domain of the UB that differentiates into the ureter. Functional experiments utilizing murine metanephric kidney explants show that BMP4, a paracrine factor secreted by tailbud-derived mesenchyme, is required for ureter morphogenesis. Conversely, ectopic BMP4 signaling is sufficient to induce ureter morphogenesis in domains of the UB normally fated to differentiate into the intra-renal collecting system. Collectively, these results indicate that the border between the kidney and ureter forms where mesenchymal tissues originating in two different areas of the early embryo meet. These data raise the possibility that the susceptibility of this junction to congenital defects in humans, such as ureteral-pelvic obstructions, may be related to the complex morphogenetic movements that are required to integrate cells from these different lineages into a single functional structure.     

Identification of land predators of African Penguins Spheniscus demersus through post-mortem examination

The African Penguin Spheniscus demersus is an endangered seabird endemic to southern Africa, and killing sprees by terrestrial predators have been one of the main threats for its mainland colonies. The methods employed to manage predators may differ depending on the species involved, therefore the implementation of strategies to limit the impacts of predation relies on the correct identification of the culprit predator. We report and quantify the lesions seen in African Penguins killed by four species of terrestrial predators: Caracal Caracal caracal (52 kills), Leopard Panthera pardus (27 kills), Domestic Dog Canis lupus familiaris (10 kills), and Cape Grey Mongoose Galerella pulverulenta (4 kills). We discuss patterns of necropsy findings that can be used to identify the predator species involved. Traditional forensic methods are useful tools to direct species-specific management actions for the conservation of the African Penguin and other seabirds so that effective mitigating measures can be deployed quickly to prevent further losses. It should be borne in mind, however, that the age, size and previous hunting experience of the predator are likely to influence the pattern of lesions that will be observed, and not all carcasses will have hallmark lesions or recognisable bite marks.     

Global Diversification at the Harsh Sea-Land Interface: Mitochondrial Phylogeny of the Supralittoral Isopod Genus Tylos (Tylidae,Oniscidea)

The supralittoral environment, at the transition between sea and land, is characterized by harsh conditions for life. Nonetheless, evolution of terrestrial isopods (Oniscidea), the only group of Crustacea fully adapted to live on land, appears to have involved a transitional step within the supralittoral. The two most basal oniscidean lineages (Ligiidae and Tylidae) have representatives that successfully colonized the supralittoral. One of them is the genus Tylos, which is found exclusively in supralittoral sandy beaches from tropical and subtropical coasts around the world. Comprehensive phylogenetic hypotheses for this genus are lacking, which are necessary for understanding the evolution and biogeography of a lineage that successfully diversified in the harsh sea-land interface. Herein, we studied the phylogenetic relationships among 17 of the 21 currently recognized species of the genus Tylos, based on sequences from four mitochondrial genes (Cytochrome Oxidase I, Cytochrome b, 16S rDNA, and 12S rDNA). Maximum Likelihood and Bayesian phylogenetic analyses identified several lineages with deep divergences and discrete geographic distributions. Phylogenetic and distributional patterns of Tylos provide important clues on the biogeography and evolution of this group. Large divergences among the most basal clades are consistent with ancient splits. Due to the biological characteristics of Tylos, which likely prevent dispersal of these isopods across vast oceanic scales, we argue that tectonic events rather than trans-oceanic dispersal explain the distribution of Tylos in different continents. Overwater dispersal, however, likely enabled range expansions within some basins, and explains the colonization of volcanic oceanic islands. Present-day distributions were also likely influenced by sea level and climate changes. High levels of allopatric cryptic genetic differentiation are observed in different regions of the world, implying that the dispersal abilities of Tylos isopods are more limited than previously thought. Our results indicate that a taxonomic revision of this group is necessary.     

AMP-activated kinase AMPK is expressed in boar spermatozoa and regulates motility

The main functions of spermatozoa required for fertilization are dependent on the energy status and metabolism. AMP-activated kinase, AMPK, acts a sensor and regulator of cell metabolism. As AMPK studies have been focused on somatic cells, our aim was to investigate the expression of AMPK protein in spermatozoa and its possible role in regulating motility. Spermatozoa from boar ejaculates were isolated and incubated under different conditions (38,5°C or 17°C, basal medium TBM or medium with Ca(2+) and bicarbonate TCM, time from 1-24 hours) in presence or absence of AMPK inhibitor, compound C (CC, 30 μM). Western blotting reveals that AMPK is expressed in boar spermatozoa at relatively higher levels than in somatic cells. AMPK phosphorylation (activation) in spermatozoa is temperature-dependent, as it is undetectable at semen preservation temperature (17°C) and increases at 38,5°C in a time-dependent manner. AMPK phosphorylation is independent of the presence of Ca(2+) and/or bicarbonate in the medium. We confirm that CC effectively blocks AMPK phosphorylation in boar spermatozoa. Analysis of spermatozoa motility by CASA shows that CC treatment either in TBM or in TCM causes a significant reduction of any spermatozoa motility parameter in a time-dependent manner. Thus, AMPK inhibition significantly decreases the percentages of motile and rapid spermatozoa, significantly reduces spermatozoa velocities VAP, VCL and affects other motility parameters and coefficients. CC treatment does not cause additional side effects in spermatozoa that might lead to a lower viability even at 24 h incubation. Our results show that AMPK is expressed in spermatozoa at high levels and is phosphorylated under physiological conditions. Moreover, our study suggests that AMPK regulates a relevant function of spermatozoa, motility, which is essential for their ultimate role of fertilization.