Adaptive Communication: Languages with More Non-Native Speakers Tend to Have Fewer Word Forms

Explaining the diversity of languages across the world is one of the central aims of typological, historical, and evolutionary linguistics. We consider the effect of language contact-the number of non-native speakers a language has-on the way languages change and evolve. By analysing hundreds of languages within and across language families, regions, and text types, we show that languages with greater levels of contact typically employ fewer word forms to encode the same information content (a property we refer to as lexical diversity). Based on three types of statistical analyses, we demonstrate that this variance can in part be explained by the impact of non-native speakers on information encoding strategies. Finally, we argue that languages are information encoding systems shaped by the varying needs of their speakers. Language evolution and change should be modeled as the co-evolution of multiple intertwined adaptive systems: On one hand, the structure of human societies and human learning capabilities, and on the other, the structure of language.     

Correlating early evolution of parasitic platyhelminths to Gondwana breakup

Investigating patterns and processes of parasite diversification over ancient geological periods should involve comparisons of host and parasite phylogenies in a biogeographic context. It has been shown previously that the geographical distribution of host-specific parasites of sarcopterygians was guided, from Palaeozoic to Cainozoic times, mostly by evolution and diversification of their freshwater hosts. Here, we propose phylogenies of neobatrachian frogs and their specific parasites (Platyhelminthes, Monogenea) to investigate coevolutionary processes and historical biogeography of polystomes and further discuss all the possible assumptions that may account for the early evolution of these parasites. Phylogenetic analyses of concatenated rRNA nuclear genes (18S and partial 28S) supplemented by cophylogenetic and biogeographic vicariance analyses reveal four main parasite lineages that can be ascribed to centers of diversity, namely Australia, India, Africa, and South America. In addition, the relationships among these biogeographical monophyletic groups, substantiated by molecular dating, reflect sequential origins during the breakup of Gondwana. The Australian polystome lineage may have been isolated during the first stages of the breakup, whereas the Indian lineage would have arisen after the complete separation of western and eastern Gondwanan components. Next, polystomes would have codiverged with hyloid sensu stricto and ranoid frog lineages before the completion of South American and African plate separation. Ultimately, they would have undergone an extensive diversification in South America when their ancestral host families diversified. Therefore, the presence of polystome parasites in specific anuran host clades and in discrete geographic areas reveals the importance of biogeographic vicariance in diversification processes and supports the occurrence and radiation of amphibians over ancient and recent geological periods.     

Effects of aldosterone and mineralocorticoid receptor antagonism on cardiac ion channels in the view of upstream therapy of atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia in man. Over the past years, importance of the renin-angiotensin-aldosterone system in AF pathophysiology has been recognized. Lately, the role of aldosterone in AF pathophysiology and mineralocorticoid receptor (MR) antagonism in "upstream" AF treatment is discussed with special regards concerning the effects on AF-induced structural remodeling. However, there is more and more evidence that MR antagonism also influences atrial electrophysiology and, respectively, AF-induced electrical remodeling, whereas the molecular mechanisms are almost unknown. The aim of this mini-review is to give an overview about the role of aldosterone in AF pathophysiology in principle and to summarize current available data concerning affection of cardiac ion channels by aldosterone and MR antagonism. Finally, as modulation of oxidative stress is discussed as one main therapy principle of "upstream" treatment of AF, potential mechanisms how modulation of oxidative stress by aldosterone and accordingly MR antagonism might alter atrial ion currents are delineated. Summarized, publications concerning potential mechanisms of aldosterone- and MR antagonism-modulated cardiac ion channels in various experimental settings are almost exclusively limited to the ventricular level and, partly, they are also contradictorily. Translation of these data to the atria is problematic because atrial and ventricular electrophysiology exhibit remarkable differences. It can be concluded that further research on the "atrial level" is needed in order to clarify the potential impact of the affection of atrial ion channels by aldosterone and accordingly MR antagonism in "upstream" therapy of AF.     

Genetic architecture and phenotypic plasticity of thermally-regulated traits in an eruptive species, <Emphasis Type="Italic">Dendroctonus ponderosae</Emphasis>

Phenotypic plasticity in thermally-regulated traits enables close tracking of changing environmental conditions, and can thereby enhance the potential for rapid population increase, a hallmark of outbreak insect species. In a changing climate, exposure to conditions that exceed the capacity of existing phenotypic plasticity may occur. Combining information on genetic architecture and trait plasticity among populations that are distributed along a latitudinal cline can provide insight into how thermally-regulated traits evolve in divergent environments and the potential for adaptation. Dendroctonus ponderosae feed on Pinus species in diverse climatic regimes throughout western North America, and show eruptive population dynamics. We describe geographical patterns of plasticity in D. ponderosae development time and adult size by examining reaction norms of populations from multiple latitudes. The relative influence of additive and non-additive genetic effects on population differences in the two phenotypic traits at a single temperature is quantified using line-cross experiments and joint-scaling tests. We found significant genetic and phenotypic variation among D. ponderosae populations. Simple additive genetic variance was not the primary source of the observed variation, and dominance and epistasis contributed greatly to the genetic divergence of the two thermally-regulated traits. Hybrid breakdown was also observed in F₂ hybrid crosses between northern and southern populations, further indication of substantial genetic differences among clinal populations and potential reproductive isolation within D. ponderosae. Although it is unclear what maintains variation in the life-history traits, observed plasticity in thermally-regulated traits that are directly linked to rapid numerical change may contribute to the outbreak nature of D. ponderosae, particularly in a changing climate.     

Epstein-Barr virus latent membrane protein 1 (LMP1) C-terminal-activating region 3 contributes to LMP1-mediated cellular migration via its interaction with Ubc9

Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1), the principal viral oncoprotein and a member of the tumor necrosis factor receptor superfamily, is a constitutively active membrane signaling protein that regulates multiple signal transduction pathways via its C-terminal-activating region 1 (CTAR1) and CTAR2, and also the less-studied CTAR3. Because protein sumoylation among other posttranslational modifications may regulate many signaling pathways induced by LMP1, we investigated whether during EBV latency LMP1 regulates sumoylation processes that control cellular activation and cellular responses. By immunoprecipitation experiments, we show that LMP1 interacts with Ubc9, the single reported SUMO-conjugating enzyme. Requirements for LMP1-Ubc9 interactions include enzymatically active Ubc9: expression of inactive Ubc9 (Ubc9 C93S) inhibited the LMP1-Ubc9 interaction. LMP1 CTAR3, but not CTAR1 and CTAR2, participated in the LMP1-Ubc9 interaction, and amino acid sequences found in CTAR3, including the JAK-interacting motif, contributed to this interaction. Furthermore, LMP1 expression coincided with increased sumoylation of cellular proteins, and disruption of the Ubc9-LMP1 CTAR3 interaction almost completely abrogated LMP1-induced protein sumoylation, suggesting that this interaction promotes the sumoylation of downstream targets. Additional consequences of the disruption of the LMP1 CTAR3-Ubc9 interaction revealed effects on cellular migration, a hallmark of oncogenesis. Together, these data demonstrate that LMP1 CTAR3 does in fact function in intracellular signaling and leads to biological effects. We propose that LMP1, by interaction with Ubc9, modulates sumoylation processes, which regulate signal transduction pathways that affect phenotypic changes associated with oncogenesis.     

Factors affecting germline mutations in a hypervariable microsatellite: a comparative analysis of six species of swallows (Aves: Hirundinidae)

Microsatellites mutate frequently by replication slippage. Empirical evidence shows that the probability of such slippage mutations may increase with the length of the repeat region as well as exposure to environmental mutagens, but the mutation rate can also differ between the male and female germline. It has been hypothesized that more intense sexual selection or sperm competition can also lead to elevated mutation rates, but the empirical evidence is inconclusive. Here, we analyzed the occurrence of germline slippage mutations in the hypervariable pentanucleotide microsatellite locus HrU10 across six species of swallow (Aves: Hirundinidae). These species exhibit marked differences in the length range of the microsatellite, as well as differences in the intensity of sperm competition. We found a strong effect of microsatellite length on the probability of mutation, but no residual effect of species or their level of sperm competition when the length effect was accounted for. Neither could we detect any difference in mutation rate between tree swallows (Tachycineta bicolor) breeding in Hamilton Harbour, Ontario, an industrial site with previous documentation of elevated mutation rates for minisatellite DNA, and a rural reference population. However, our cross-species analysis revealed two significant patterns of sex differences in HrU10 germline mutations: (1) mutations in longer alleles occurred typically in the male germline, those in shorter alleles in the female germline, and (2) male germline mutations were more often expansions than contractions, whereas no directional bias was evident in the female germline. These results indicate some fundamental differences in male and female gametogenesis affecting the probability of slippage mutations. Our study also reflects the value of a comparative, multi-species approach for locus-specific mutation analyses, through which a wider range of influential factors can be assessed than in single-species studies.     

Modeling cold tolerance in the mountain pine beetle, Dendroctonus ponderosae

Cold-induced mortality is a key factor driving mountain pine beetle, Dendroctonus ponderosae, population dynamics. In this species, the supercooling point (SCP) is representative of mortality induced by acute cold exposure. Mountain pine beetle SCP and associated cold-induced mortality fluctuate throughout a generation, with the highest SCPs prior to and following winter. Using observed SCPs of field-collected D. ponderosae larvae throughout the developmental season and associated phloem temperatures, we developed a mechanistic model that describes the SCP distribution of a population as a function of daily changes in the temperature-dependent processes leading to gain and loss of cold tolerance. It is based on the changing proportion of individuals in three states: (1) a non cold-hardened, feeding state, (2) an intermediate state in which insects have ceased feeding, voided their gut content and eliminated as many ice-nucleating agents as possible from the body, and (3) a fully cold-hardened state where insects have accumulated a maximum concentration of cryoprotectants (e.g. glycerol). Shifts in the proportion of individuals in each state occur in response to the driving variables influencing the opposite rates of gain and loss of cold hardening. The level of cold-induced mortality predicted by the model and its relation to extreme winter temperature is in good agreement with a range of field and laboratory observations. Our model predicts that cold tolerance of D. ponderosae varies within a season, among seasons, and among geographic locations depending on local climate. This variability is an emergent property of the model, and has important implications for understanding the insect's response to seasonal fluctuations in temperature, as well as population response to climate change. Because cold-induced mortality is but one of several major influences of climate on D. ponderosae population dynamics, we suggest that this model be integrated with others simulating the insect's biology.     

Temperature Determines Symbiont Abundance in a Multipartite Bark Beetle-fungus Ectosymbiosis

In this study, we report evidence that temperature plays a key role in determining the relative abundance of two mutualistic fungi associated with an economically and ecologically important bark beetle, Dendroctonus ponderosae. The symbiotic fungi possess different optimal temperature ranges. These differences determine which fungus is vectored by dispersing host beetles as temperatures fluctuate over a season. Grosmannia clavigera is the predominant fungus carried by dispersing beetles during cool periods but decreases in prevalence as daily maximum temperatures approach 25°C, and becomes extremely rare when temperatures reach or exceed 32°C. In contrast, Ophiostoma montium increases in prevalence as temperatures approach 25°C, and becomes the predominant symbiont dispersed when temperatures reach or exceed 32°C. The possession of different optimal growth temperatures may facilitate the stable coexistence of the two fungi by supporting growth of each fungus at different times, minimizing direct competition. Furthermore, the beetle may reduce its risk of being left aposymbiotic by exploiting not one, but two symbionts, whose combined growth optima span a wide range of environmental conditions. The possession of multiple symbionts with different temperature tolerances may allow the beetle to occupy highly variable habitats over a wide geographic range. Such temperature-driven symbiont shifts are likely to have major consequences for both the host and its symbionts under current temperature regimes and those predicted to occur because of climate change.