Genetic rescue: a safe or risky bet?

Small and isolated populations face threats from genetic drift and inbreeding. To rescue populations from these threats, conservation biologists can augment gene flow into small populations to increase variation and reduce inbreeding depression. Spectacular success stories include greater prairie chickens in Illinois (Westermeier et al. 1998 ), adders in Sweden (Madsen et al. 1999 ) and panthers in Florida (Johnson et al. 2010 ). However, we also know that performing such crosses risks introducing genes that may be poorly adapted to local conditions or genetic backgrounds. A classic example of such ‘outbreeding depression’ occurred when different subspecies of ibex from Turkey and the Sinai were introduced to assist recovery of an ibex population in Czechoslovakia (Templeton 1986 ). Despite being fertile, the hybrids birthed calves too early, causing the whole population to disappear. In the face of uncertainty, conservation biologists have tended to respect genetic identity, shying away from routinely crossing populations. In this issue of Molecular Ecology, Frankham ( 2015 ) compiles empirical data from experimental studies to assess the costs and benefits of between‐population crosses (Fig.  1 ). Crosses screened to exclude those involving highly divergent populations or distinct habitats show large heterosis with few apparent risks of outbreeding depression. This leads Frankham to advocate for using assisted gene flow more widely. But do the studies analysed in this meta‐analysis adequately test for latent outcrossing depression?     

Does metazooplankton regulate the ciliate community in a shallow eutrophic lake?

1. As grazers on picoplankton and nanoplankton, planktonic ciliates form an important link in pelagic food webs. Ciliate communities may be controlled by predation by metazooplankton. In eutrophic systems, however, where the number of large crustaceans is often low, the mechanisms that regulate ciliate dynamics have rarely been described. 2. We conducted an enclosure experiment with natural and screened (145 μm) summer plankton communities to investigate the effect of the small‐sized crustacean zooplankton on ciliate community structure and the microbial loop in a shallow eutrophic lake. 3. The removal of the larger fraction of crustaceans initiated a decrease in total ciliate abundance. At the community level, we observed a substantial increase in large‐sized predacious ciliates (>100 μm) and a simultaneous decrease in the abundance of smaller ciliates (<20–40 μm) that were mostly bacterivores and bacterio‐herbivores. The compositional shift in the ciliate community, however, did not cascade down to the level of bacteria and edible phytoplankton.     

What factors control planktonic ciliates during summer in a highly eutrophic lake?

A mesocosm experiment in 24 enclosures (6 m³) started at the end of June 1996 in a highly eutrophic shallow lake, Lake Köyliönjärvi (SW Finland). The original factorial design with nutrient, fish and macrophyte treatments was lost due to strong winds causing leakages. However, after the walls were made leak-proof again on July 11, the planktonic communities developed in divergent ways. On July 31 there was a tenfold variation in total crustacean biomass among the enclosures and the lake (40.2–417.5 g C l^–1), and chlorophyll a varied from 9.5 to 67.0 g l^–1. Here, the single-day data on the 25 planktonic communities is analysed by means of correlation and factor analysis in order to identify factors controlling the protozoans, with particular emphasis on ciliates. The data set comprised: total phosphorus, nitrogen, chlorophyll, bacteria, autotrophic picoplankton, heterotrophic flagellates, abundance and species composition of ciliates, phytoplankton and metazooplankton. The results indicate that although the total ciliate abundance (ranging from 16.2 to 95.0 ind l^–1) was controlled by food resources, the observed differences in ciliate community structure could be attributed partly to differential predation by metazooplankton. The effect of Daphnia cucullata, the dominant daphnid cladoceran, was stronger than that of other metazoans.     

Dynamics of bacterioplankton in oligotrophic and eutrophic aquatic environments: bottom-up or top-down control?

Measurements of bacterial biomass, production and mortality have been carried out in a large range of aquatic environments, including eutrophic and oligotrophic ones. The general trends of variations of bacterial biomass, size, specific growth rate and mortality rate in all these environments are examined. The overall flux of bacterial production is taken as an index of the flux of organic matter available to bacteria, thus characterizing the richness of the environment. Bacterial biomass is roughly proportional to richness, while mean cell size increases with it. The turnover rate of biomass, as revealed either by growth or by mortality rates, appears to be fairly independent of richness.These observations are compatible with a simple resource-limited (bottom-up controlled) model of the dynamics of bacterioplankton. On the other hand, they are in contradiction with the predictions of a predator-controlled (top-down controlled) model.     

Ectoplasmic specialization: a friend or a foe of spermatogenesis?

The ectoplasmic specialization (ES) is a testis-specific, actin-based hybrid anchoring and tight junction. It is confined to the interface between Sertoli cells at the blood-testis barrier, known as the basal ES, as well as between Sertoli cells and developing spermatids designated the apical ES. The ES shares features of adherens junctions, tight junctions and focal contacts. By adopting the best features of each junction type, this hybrid nature of ES facilitates the extensive junction-restructuring events in the seminiferous epithelium during spermatogenesis. For instance, the alpha6beta1-integrin-laminin 333 complex, which is usually limited to the cell-matrix interface in other epithelia to facilitate cell movement, is a putative apical ES constituent. Furthermore, JAM-C and CAR, two tight junction integral membrane proteins, are also components of apical ES involving in spermatid orientation. We discuss herein the mechanisms that maintain the cross-talk between ES and blood-testis barrier to facilitate cell movement and orientation in the seminiferous epithelium.     

Cell size: a matter of life or death?

Proper growth and development of multicellular organisms require the tight regulation of cell growth, cell division and cell death. A recent study has identified a novel regulatory link between two of these processes: cell growth and cell death.     

Positive effects of UV radiation on a calanoid copepod in a transparent lake: do competition, predation or food availability play a role?

Zooplankton tolerant to ultraviolet radiation (UVR) could beindirectly affected by UVR through interactions with UV-sensitivespecies in the same ecosystem. In Lake Giles, Pennsylvania,USA, the calanoid copepod Leptodiaptomus minutus is more UVRtolerant than the cohabiting species Daphnia catawba and Cyclopsscutifer. We asked whether L. minutus is affected by UV-inducedmortality of a food competitor (D. catawba) or a predator ofits nauplii (C. scutifer). We conducted two in situ enclosureexperiments with six treatments: L. minutus alone, L . minutus+ Daphnia and L. minutus + Cyclops in the presence and absenceof UVR. There were few differences in survival among treatmentsin Experiment 1, which had enhanced food and a cumulative UVR(320 nm) dose of 9.3 kJ m^–2. In Experiment 2, which hadambient food and a UVR (320 nm) dose of 20.0 kJ m^–2, L.minutus survival and reproduction were higher in the +UVR comparedto –UVR, regardless of competitors or predators. Chlorophylla (Chl a) in Experiment 2 was higher in the +UVR than –UVR.While interactions between zooplankton species of differingUVR tolerances are potentially important, these results insteaddemonstrate that the beneficial UVR effect on L. minutus isindependent of concurrent detrimental UVR effects on competitorsand predators. Further research on the phytoplankton communityis necessary to determine whether UVR alleviates bacterial competition,increases nutrient availability or affects phytoplankton byother mechanisms.     

Sediment resuspension and light attenuation in Peoria Lake: can macrophytes improve water quality in this shallow system?

We examined sediment resuspension and light attenuation in relation to the potential for macrophytes to improve water quality conditions in Peoria Lake, Illinois (U.S.A.). The lake exhibited high total suspended solids (TSS) loading and retention of predominantly fine-grained particles in 2000. Large fetches along prevailing wind rose, coupled with shallow morphometry and sediment particles composed of >90% silt and clay resulted in frequent periods of sediment resuspension. As calculated (wave theory) shear stress increased above the critical shear stress (measured experimentally), turbidity increased substantially at a resuspension monitoring station. Resuspension model explorations suggested that establishment of submersed aquatic macrophytes could substantially reduce sediment resuspension in Peoria Lake. However, K _d is currently very high, while Secchi transparency low, at in-lake stations. Thus, in order to establish a persistent macrophyte population in the lake to control resuspension, the underwater light regime will have to improve quite dramatically.     

Phytoplankton seasonal variation in a shallow stratified eutrophic reservoir (Garças Pond, Brazil)

This study aimed at describing the phytoplankton dynamics and structure in a shallow eutrophic reservoir, the Garças Pond, located in the Parque Estadual das Fontes do Ipiranga (23°38′40.6′′ S, 46°37′28.0′′ W), in the Municipality of São Paulo, southeast Brazil. Samples were collected monthly from January to December 1997 in five depths (subsurface, 1 m, 2 m, 3 m, and 20 cm above the bottom) in the pelagic zone (Z _max = 4.7 m). Abiotic variables studied were: water temperature, turbidity, transparency, conductivity, pH, dissolved oxygen, alkalinity, inorganic carbon, and N and P dissolved and total forms. Altogether 236 phytoplankton taxa distributed among 10 classes were identified. Phytoplankton seasonal and vertical variation was related to shifts in the water chemical features as a consequence of a warm-wet season with stratified water column (phase 1, January–March and September–December) alternating with a cool-dry season with mixed water column (phase 2, April–August). There were shifts in cyanobacterial dominance over the entire year. During phase 1, Raphidiopsis/Cylindrospermopsis was one of the most important taxon. During phase 2, Raphidiopsis/Cylindrospermopsis biomass decreased, whereas richness and diversity increased and diatoms were relatively abundant. In September, when the water column was markedly stratified, a cyanobacterial bloom (Sphaerocavum brasiliense) occurred. Changes in water chemical variables caused by the bloom allowed recognition of a phase 3, in which pH and chlorophyll a, TP and CO₃ ^2? concentration reached their highest values. According to Reynolds and collaborators’ functional groups approach, phase 1 was marked by groups S/W1/W2/H1/Y, phase 2 by groups K/L _M /L _O /D/P/X1/F, and phase 3 by group M. This sequence was corroborated by canonical correspondence analysis (CCA) results.     

Actinomycetes in lake muds: dormant spores or metabolically active mycelium?

Homogenization and ultrasonication experiments on samples of lake muds indicated that Micromonospora strains were present as a mixture of mycelium and spores. In contrast, strains of streptomycetes and nocardioforms appeared to be in the form of arthrospores or fragmentation spores respectively. Micromonospora strains originally isolated from lakes were able to grow in both native and enriched muds incubated in the laboratory. Numbers of streptomycetes and nocardioforms did not increase in these muds and are presumed to be relatively inactive in this habitat. We postulate that Micromonospora strains have an active role in the lacustrine environment as well as in soil.     

Management of chronic insomnia using hypnotics: a friend or a foe?

Sleep and Biological Rhythms - Epidemiological studies suggest that 10–15% adults meet the present criteria for the diagnosis of insomnia disorder; however, there may be geographical...     

Inflammation in atherosclerosis: a cause or a result of vascular disorders?

Sound data support the concept that in atherosclerosis, inflammation and dyslipidemia intersect each other and that irrespective of the initiator, both participate from the early stages to the ultimate fate of the atheromatous plaque. The two partakers manoeuvre a vicious circle in atheroma formation: dyslipidaemia triggers an inflammatory process and inflammation elicits dyslipidaemia. Independent of the initial cause, the atherosclerotic lesions occur focally, in particular arterial-susceptible sites, by a process that, although continuous, can be arbitrarily divided into a sequence of consecutive stages that lead from fatty streak to the fibro-lipid plaque and ultimately to plaque rupture and thrombosis. In the process, the initial event is a change in endothelial cells (EC) constitutive properties. Then, the molecular alarm signals send by dysfunctional EC are decoded by specific blood immune cells (monocytes, T lymphocytes, neutrophils, mast cells) and by the resident vascular cells, that respond by initiating a robust inflammatory process, in which the cells and the factors they secrete hasten the atheroma development. Direct and indirect crosstalk between the cells housed within the nascent plaque, complemented by the increase in risk factors of atherosclerosis lead to atheroma development and outcome. The initial inflammatory response can be regarded as a defense/protective reaction mechanism, but its further amplification, speeds up atherosclerosis. In this review, we provide an overview on the role of inflammation and dyslipidaemia and their intersection in atherogenesis. The data may add to the foundation of a novel attitude in the diagnosis and treatment of atherosclerosis.     

p73: a Positive or Negative Regulator of Angiogenesis,or Both?

The role of p73, the homologue of the tumor suppressor p53, in regulating angiogenesis has recently been extensively investigated, resulting in the publication of five articles. Of these, two studies suggested a suppressive role, while the others implied a stimulatory role for the p73 isoforms in regulating angiogenesis. A negative role for TAp73, the full-length form that is often associated with tumor suppression, in blood vessel formation, is consistent with its general attributes and was proposed to be effected indirectly through the degradation of hypoxia-inducible factor 1α (HIF1-α), the master angiogenic regulator. In contrast, a positive role for TAp73 coincides with its recently understood role in supporting cellular survival and thus tumorigenesis, consistent with TAp73 being not-mutated but rather often overexpressed in clinical contexts. In the latter case, TAp73 expression was induced by hypoxia via HIF1-α, and it appears to directly promote angiogenic target gene activation and blood vessel formation independent of HIF1-α. This mini review will provide an overview of these seemingly opposite recent findings as well as earlier data, which collectively establish the definite possibility that TAp73 is indeed capable of both promoting and inhibiting angiogenesis, depending on the cellular context.     

Colonization of ephemeral detrital patches by vagile macroinvertebrates in a brackish lake: a body size-related process?

The mechanisms regulating the build-up of invertebrate assemblages on ephemeral detritus patches are still poorly understood. Here, the daily colonization of decaying reed leaves by vagile macroinvertebrates was monitored in an brackish lake in Italy. The highly variable abundance patterns of dominant taxa were analysed by spectral and geostatistical techniques to test for nonrandomness and to further determine whether they were related to body size. Comparisons between two contrasting sites allowed an assessment of the generality of our observations. At both sites, the macroinvertebrate assemblage was dominated by three detritivorous taxa, i.e. the isopod Lekanesphaera monodi, the amphipod Microdeutopus gryllotalpa and the polychaete Neanthes caudata. Overall, their abundance patterns were characterised by short-term fluctuations of a nonrandom, autocorrelated nature. In addition, a significant covariation was observed between the average body mass of each taxon and the complexity of the respective abundance pattern, expressed by the fractal dimension D. The covariation was observed at both study sites, notwithstanding the diverging outcomes of bivariate pattern comparisons for similar-sized taxa. Our findings indicate that the size of macroinvertebrates is strongly related to the short-term dynamics of their abundance patterns on reed detritus, suggesting that the interaction between vagile consumers and ephemeral resource patches might be influenced by individual energetics. The implications of size-related constraints for the coexistence of species on decaying detrital patches are discussed.