Evolutionary and ecological genomics of non‐model plants

Abstract Dissecting evolutionary dynamics of ecologically important traits is a long‐term challenge for biologists. Attempts to understand natural variation and molecular mechanisms have motivated a move from laboratory model systems to non‐model systems in diverse natural environments. Next generation sequencing methods, along with an expansion of genomic resources and tools, have fostered new links between diverse disciplines, including molecular biology, evolution, ecology, and genomics. Great progress has been made in a few non‐model wild plants, such as Arabidopsis relatives, monkey flowers, and wild sunflowers. Until recently, the lack of comprehensive genomic information has limited evolutionary and ecological studies to larger QTL (quantitative trait locus) regions rather than single gene resolution, and has hindered recognition of general patterns of natural variation and local adaptation. Further efforts in accumulating genomic data and developing bioinformatic and biostatistical tools are now poised to move this field forward. Integrative national and international collaborations and research communities are needed to facilitate development in the field of evolutionary and ecological genomics.     

FINDING AUTONOMY IN BIRTH

Over the last several years, as cesarean deliveries have grown increasingly common, there has been a great deal of public and professional interest in the phenomenon of women 'choosing' to deliver by cesarean section in the absence of any specific medical indication. The issue has sparked intense conversation, as it raises questions about the nature of autonomy in birth. Whereas mainstream bioethical discourse is used to associating autonomy with having a large array of choices, this conception of autonomy does not seem adequate to capture concerns and intuitions that have a strong grip outside this discourse. An empirical and conceptual exploration of how delivery decisions ought to be negotiated must be guided by a rich understanding of women's agency and its placement within a complicated set of cultural meanings and pressures surrounding birth. It is too early to be 'for' or 'against' women's access to cesarean delivery in the absence of traditional medical indications – and indeed, a simple pro- or con- position is never going to do justice to the subtlety of the issue. The right question is not whether women ought to be allowed to choose their delivery approach but, rather, taking the value of women's autonomy in decision-making around birth as a given, what sorts of guidelines, practices, and social conditions will best promote and protect women's full inclusion in a safe and positive birth process.     

Geographic and stratigraphic change in the morphology of Triarthrus beckii (Green) (Trilobita): a test of the Plus ça change model of evolution

The Plus ça change model predicts that deepwater trilobite species such as Triarthrus should exhibit gradual phyletic evolution. A detailed stratigraphic sequence of Triarthrus beckii specimens considered together with geographically separated samples from a single time interval provide a test of the Plus ça change model. We examined geographic patterns of variation in cranidial shape based on specimens from four approximately synchronous levels within the Upper Ordovician (lower Edenian) strata of New York, Québec, Kentucky and Pennsylvania. All geographic populations differ in mean size, except for New York and Pennsylvania. Because allometry is present in both meraspid and holaspid phases of the trilobite, size effects on shape were removed by ontogenetic standardization. Cranidial shapes were then compared among the four study sites and eight stratophenetic samples from New York, obtained by subdividing our Mohawkian Composite Standard Section into 20-m-thick intervals. Goodall's F-test of pairwise comparisons of cranidial shape between eight subintervals in New York and the other three populations are all significant. Geographic variation in cranidial size and shape in T . beckii appears to display a gradient or cline-like pattern that is related to paleogeography. Although cranidial shape is not entirely static within the New York stratophenetic series, it is in all cases different from that sampled elsewhere in the region. Thus, there is no evidence of wholesale immigration and emigration among the geographic areas. Instead, the geographic gradient of T . beckii shape variation may have remained fairly stable over ca. 3 million years during the mid-Chatfieldian to early Edenian interval. This result is indicative of stasis. Consequently, the evolutionary history of T . beckii contradicts the Plus ça change model.     

On the occurrence, causes and potential consequences of low zooplankton to phytoplankton ratios in New Zealand lakes

SUMMARY. 1. New Zealand lakes are shown to have lower average zooplankton biomasses than north-temperate lakes of similar average phytoplankton biomass, expressed as cell volume or chlorophyll a , or similar average total phosphorus concentration, typically by a factor of 5 or more.
2. Evidence suggests that the relatively low zooplankton biomasses of New Zealand lakes may be related to a tendency for them to be dominated by large algae that are not directly available as food for zooplankton, with oligotrophy lakes in particular differing from north-temperate lakes in this respect.
3. This difference in turn may be related largely to their mixing regimes. All of the New Zealand lakes are polymietic or monomietic, whereas the northern lakes used for comparison are mostly dimietic. Also, hetero-cystous cyanobacteria are favoured by the low inorganic nitrogen concentrations that are typical of New Zealand lakes.
4. Poor nutritional quality of the phytoplankton, relating to nitrogen limitation in many New Zealand lakes, might supplement the effects of cell size.
5. Low exploitation of phytoplankton by zooplankton can be expected to produce a shift in the metabolism of New Zealand lakes towards the sediments. Among the potential consequences of this effect are increased hypolimnetic oxygen demand with increased susceptibility to development of large internal loads of nutrients, and consequently, increased sensitivity to accelerated eutrophication from any increase in external nutrient loads.     

Shifting dispersal modes at an expanding species’ range margin

While it is generally recognized that noncontiguous (long‐distance) dispersal of small numbers of individuals is important for range expansion over large geographic areas, it is often assumed that colonization on more local scales proceeds by population expansion and diffusion dispersal (larger numbers of individuals colonizing adjacent sites). There are few empirical studies of dispersal modes at the front of expanding ranges, and very little information is available on dispersal dynamics at smaller geographic scales where we expect contiguous (diffusion) dispersal to be prevalent. We used highly polymorphic genetic markers to characterize dispersal modes at a local geographic scale for populations at the edge of the range of a newly invasive grass species (Brachypodium sylvaticum) that is undergoing rapid range expansion in the Pacific Northwest of North America. Comparisons of Bayesian clustering of populations, patterns of genetic diversity, and gametic disequilibrium indicate that new populations are colonized ahead of the invasion front by noncontiguous dispersal from source populations, with admixture occurring as populations age. This pattern of noncontiguous colonization was maintained even at a local scale. Absence of evidence for dispersal among adjacent pioneer sites at the edge of the expanding range of this species suggests that pioneer populations undergo an establishment phase during which they do not contribute emigrants for colonization of neighbouring sites. Our data indicate that dispersal modes change as the invasion matures: initial colonization processes appear to be dominated by noncontiguous dispersal from only a few sources, while contiguous dispersal may play a greater role once populations become established.     

A cost‐effective method of assessing thermal habitat quality for endotherms

The conservation of many endothermic species depends critically on the availability of suitable retreat sites, yet we know little about the variation in thermal quality of such microhabitats. Studies of thermal habitat suitability for birds and mammals must account for the effect of endothermic heat production on their microclimates. For example, endotherms may significantly raise the air temperature in their retreat sites and this effect must be considered when assessing retreat site quality. We devised an inexpensive means by which to construct pseudo‐endothermic ‘environmental temperature’ models with the use of disposable heat pads. We applied this technique to investigate thermal aspects of nest box design, illustrating the potential positive and negative effects of nest box insulation depending on the environmental context. We suggest that, from a thermal perspective, the avoidance of heat stress is an important and underappreciated issue in the retreat site selection of endotherms.     

Phylogenetic Relationships of Blepharisma Americanum and Colpoda Inflata Within the Phylum Ciliophora Inferred From Complete Small Subunit Rrna Gene Sequences

ABSTRACT The complete small subunit rRNA gene sequences of the heterotrich Blepharisma americanum and the colpodid Colpoda inflata were determined to be 1719 and 1786 nucleotides respectively. the phylogeny produced by comparisons with other ciliates indicated that C. inflata is allied more closely with the nassophoreans and oligohymenophoreans than the spirotrichs. This is consistent with the placement of the colpodids in the Class Copodea. Blepharisma americanum was not grouped with the hypotrichs but instead was placed as the earliest branching ciliate. the distinct separation of B. americanum supports the elevation to class status given the heterotrichs based on morphological characters.