Genomic diversity,population structure,and migration following rapid range expansion in the Balsam Poplar,Populus balsamifera

Rapid range expansions can cause pervasive changes in the genetic diversity and structure of populations. The postglacial history of the Balsam Poplar, Populus balsamifera, involved the colonization of most of northern North America, an area largely covered by continental ice sheets during the last glacial maximum. To characterize how this expansion shaped genomic diversity within and among populations, we developed 412 SNP markers that we assayed for a range‐wide sample of 474 individuals sampled from 34 populations. We complemented the SNP data set with DNA sequence data from 11 nuclear loci from 94 individuals, and used coalescent analyses to estimate historical population size, demographic growth, and patterns of migration. Bayesian clustering identified three geographically separated demes found in the Northern, Central, and Eastern portions of the species’ range. These demes varied significantly in nucleotide diversity, the abundance of private polymorphisms, and population substructure. Most measures supported the Central deme as descended from the primary refuge of diversity. Both SNPs and sequence data suggested recent population growth, and coalescent analyses of historical migration suggested a massive expansion from the Centre to the North and East. Collectively, these data demonstrate the strong influence that range expansions exert on genomic diversity, both within local populations and across the range. Our results suggest that an in‐depth knowledge of nucleotide diversity following expansion requires sampling within multiple populations, and highlight the utility of combining insights from different data types in population genomic studies.     

Survival and Breeding Transitions for a Reintroduced Bison Population: a Multistate Approach

Abstract: The iconic plains bison (Bison bison) have been reintroduced to many places in their former range, but there are few scientific data evaluating the success of these reintroductions or guiding the continued management of these populations. Relying on mark-recapture data, we used a multistate model to estimate bison survival and breeding transition probabilities while controlling for the recapture process. We tested hypotheses in these demographic parameters associated with age, sex, reproductive state, and environmental variables. We also estimated biological process variation in survival and breeding transition probabilities by factoring out sampling variation. The recapture rate of females and calves was high (0.78 ± 0.15 [SE]) and much lower for males (0.41 ± 0.23), especially older males (0.17 ± 0.15). We found that overall bison survival was high (>0.8) and that males (0.80 ± 0.13) survived at lower rates than females (0.94 ± 0.04), but as females aged survival declined (0.89 ± 0.05 for F ≥15 yr old). Lactating and non-lactating females survived at similar rates. We found that females can conceive early (approx. 1.5 yr of age) and had a high probability (approx. 0.8) of breeding in consecutive years, until age 13.5 years, when females that were non-lactating tended to stay in that state. Our results suggest senescence in reproduction and survival for females. We found little support for the effect of climatic covariates on demographic rates, perhaps because the park's current population management goals were predicated from drought-year conditions. This reintroduction has been successful, but continued culling actions will need to be employed and an adaptive management approach is warranted. Our demographic approach can be applied to other heavily managed large-ungulate systems with few or no natural predators.     

Winter and summer upwelling modes and their biological importance in the California Current Ecosystem

Analysis of monthly coastal upwelling intensities revealed two seasonal and biologically relevant upwelling ‘modes’ in the California Current Ecosystem (CCE). The first mode reflected upwelling during the summer months and was characterized by low‐frequency (multidecadal) processes, including significant (P<0.01) linear trends at some latitudes. In contrast, the second mode reflected wintertime upwelling and was defined by higher‐frequency variability associated with the North Pacific High and El Niño Southern Oscillation events. These modes were compared with multidecadal time series of splitnose rockfish (Sebastes diploproa) otolith growth, yelloweye rockfish (S. ruberrimus) otolith growth, Chinook salmon (Oncorhynchus tshawytscha) scale growth, and indices of Cassin's auklet (Ptychoramphus aleuticus) and common murre (Uria aalge) reproduction in the central‐northern CCE. In redundancy and correlation analyses, salmon growth and Cassin's auklet fledgling success associated with the summer upwelling mode while all other time series associated with the winter upwelling mode, indicating that CCE biology was differentially sensitive to these seasonal upwelling patterns. Thus, upwelling occurred in unrelated seasonal modes with contrasting trends, atmospheric forcing mechanisms, and impacts on the biology of the CCE, underscoring the importance of seasonality when evaluating ecosystem response to climate variability and change.     

Phytochelatin–metal(loid) transport into vacuoles shows different substrate preferences in barley and Arabidopsis

Cadmium (Cd) and arsenic (As) are toxic to all living organisms, including plants and humans. In plants, Cd and As are detoxified by phytochelatins (PCs) and metal(loid)‐chelating peptides and by sequestering PC–metal(loid) complexes in vacuoles. Consistent differences have been observed between As and Cd detoxification. Whereas chelation of Cd by PCs is largely sufficient to detoxify Cd, As–PC complexes must be sequestered into vacuoles to be fully detoxified. It is not clear whether this difference in detoxification pathways is ubiquitous among plants or varies across species. Here, we have conducted a PC transport study using vacuoles isolated from Arabidopsis and barley. Arabidopsis vacuoles accumulated low levels of PC₂–Cd, and vesicles from yeast cells expressing either AtABCC1 or AtABCC2 exhibited negligible PC₂–Cd transport activity compared with PC₂–As. In contrast, barley vacuoles readily accumulated comparable levels of PC₂–Cd and PC₂–As. PC transport in barley vacuoles was inhibited by vanadate, but not by ammonium, suggesting the involvement of ABC‐type transporters. Interestingly, barley vacuoles exhibited enhanced PC₂ transport activity when essential metal ions, such as Zn(II), Cu(II) and Mn(II), were added to the transport assay, suggesting that PCs might contribute to the homeostasis of essential metals and detoxification of non‐essential toxic metal(loid)s.     

Branching out: a remarkable new branching syllid (Annelida) living in a Petrosia sponge (Porifera: Demospongiae)

We describe the morphology and biology of a previously unknown form of branching annelid, Ramisyllis multicaudata gen. et sp. nov. , an endosymbiont of shallow‐water marine sponges (Petrosia sp., Demospongiae) in northern Australia. It belongs to the polychaete family Syllidae, as does Syllis ramosa McIntosh, 1879, the only other named branching annelid, which was collected from deep‐water hexactinellid sponges during the 1875 Challenger expedition. It differs from S. ramosa in parapodial and chaetal morphology. Ramisyllis multicaudata gen. et sp. nov. has segments of several types, including specialized posterior segments on the emergent portions of the worm, and simplified elongate segments that bridge larger cavities in the sponge interior. Aside from the obvious branching form, the new annelid is similar to Parahaplosyllis, differing from it in lacking pharyngeal armature and in the details of the parapodial chaetae and dorsal cirri. Molecular evidence from 16S and 18S rDNA supports a sister‐group relationship with Parahaplosyllis, with both being sister to Trypanosyllis and Eurysyllis. The phylogenetic position of R. multicaudata gen. et sp. nov. indicates that branching has evolved independently in Ramisyllis gen. nov. and Syllis. This is supported by differences in the branching process between the two taxa: in S. ramosa branching is initiated by segment addition at the parapodium, whereas in R. multicaudata gen. et sp. nov. segments are added from a region between parapodia. A model for branching in R. multicaudata gen. et sp. nov. is proposed and possible developmental processes underlying branching in Annelida, and body symmetry comparisons with other invertebrates, are also discussed. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 481–497.     

Hemagglutination and Erythrophagocytosis Associated with the Anemia of Plasmodium berghei Infections of Rats*

SYNOPSIS. The presence of anemia that often seems excessive for the amount of parasitemia in Plasmodium berghei infections had led to the suggestion that autoimmunity might be in part responsible for the anemia. In another erythrocytic infection, Anaplasma marginale of cattle, the association of erythrophagocytosis, autohemagglutination and anemia with infection has led to the suggestion that autoimmunization may occur in anaplasmosis. The possibility that similar findings might be present in P. berghei infections of rats has been investigated. Groups of rats infected with P. berghei were examined at 2–3 day intervals during the course of infection. Red blood cell counts, hematocrit values and percentages of parasitized erythrocytes were determined. The rats were bled at intervals and the sera tested for agglutinins for trypsinized rat erythrocytes. Other infected rats were killed, and their spleens and bone marrow were examined for evidence of erythrophagocytosis. Parasitemia reached a peak on the 9th day of infection and became subpatent by the 14th. The greatest depression in erythrocyte numbers occurred on the 11th day, and the counts remained below normal until the 23rd day. Phagocytized erythrocytes, predominantly uninfected, were found in the phagocytes of the spleen and bone marrow from the 5th through the 21st day. Agglutinins for trypsinized normal rat erythrocytes were present in the sera of the rats in titers as high as 1:64 from the 5th through 14th day of infection. Lower agglutinin titers (1:8) were found from time to time in sera of rats made anemic by repeated bleedings. It is not clear whether these agglutinins are responsible for erythrophagocytosis; however, the fact that predominantly uninfected erythrocytes were phagocytized suggests that the erythrocytes might have been opsonized by an autoantibody associated with the P. berghei infections.