An investigation of dominance in phytoplankton using the PROTECH model

1. Using a model (PROTECH-C) that simulates the simultaneous daily growth of eight phytoplankton species, the following hypotheses were tested: (i) for each given set of simulated conditions, the species with the most appropriate trait, as predicted by a functional group classification, should dominate the community; (ii) with removal of this dominant species, the next best-adapted species should dominate and should be from the same, or a close, functional group where available; (iii) a reduction in the inoculum size of the initially dominant species will not prevent its eventual dominance of the community.
2. For clearer insight into the mechanisms underlying these community processes, a functional group classification based upon species morphology has been used to produce a matrix analogous to Grime's CSR (C, competitor; S, stress tolerator; R, ruderal) paradigm. The effects upon this phytoplankton community of temperature, grazing, limiting light and nutrients over a simulated year were recorded.
3. The results supported all three hypotheses. It was found that, for a given selective constraint, functional traits provided excellent predictors of the dominant types. Also, under conditions of resource competition, the number of functional groups represented decreased. Competition was greatest within functional groups where niche overlap was high, but one species was always clearly the strongest competitor, i.e. its superiority over its nearest functional competitor was regularly expressed even when the difference in inoculum size was great (1000-fold). These conclusions emphasized the power that trait selection can have in the shaping of communities.     

DEVELOPMENT OF TASSEL SEED 2 INFLORESCENCES IN MAIZE

The normal pattern of maize floral development of staminate florets on the terminal inflorescence (tassel) and pistillate florets on the lateral inflorescences (ears) is disrupted by the recessive mutation tassel seed 2. Tassel seed 2 mutant plants develop pistillate florets instead of staminate florets in the tassel. In addition, the ears of tassel seed 2 plants display irregular rowing of kernels due to the development of the normally suppressed lower floret of each spikelet. The morphology of tassel and ear florets of the recessive maize mutant tassel seed 2 has been compared to those of wild-type maize through development. We have identified the earliest stages at which morphological signs of sex differentiation are evident. We find that sex determination occurs during the same stage on tassel and ear development. Early postsex determination morphology of florets in wild-type ears and in tassel seed 2 tassels and ears is identical.     

CYP78A5 encodes a cytochrome P450 that marks the shoot apical meristem boundary in Arabidopsis

The normal development of shoot structures depends on controlling the growth, proliferation and differentiation of cells derived from the shoot apical meristem. We have identified the CYP78A5 gene encoding a putative cytochrome P450 monooxygenase that is the first member of the CYP78 family from Arabidopsis. This gene is strongly expressed in the peripheral regions of the vegetative and reproductive shoot apical meristems, defining a boundary between the central meristematic zone and the developing organ primordia. In addition, CYP78A5 shows a dynamic pattern of expression during floral development. Overexpression of CYP78A5 affects multiple cell types, causing twisting and kinking of the stem and defects in floral development. To define the relationship of CYP78A5 to genes controlling meristem function, we examined CYP78A5 expression in plants mutant for SHOOT MERISTEMLESS, ZWILLE and ARGONAUTE, and have found that CYP78A5 expression is altered in these mutant backgrounds. We propose that CYP78A5 has a role in regulating directional growth in the peripheral region of the shoot apical meristem in response to cues established by genes regulating meristem function.     

Interactions Between tassel seed Genes and Other Sex Determining Genes in Maize (Article was originally published in Developmental Genetics 15:155–171.)

Erin E. Irish, Jane A. Langdale, and Timothy Nelson. Interactions Between tassel seed Genes and Other Sex Determining Genes in Maize (Article was originally published in Developmental Genetics 15:155–171.) An incorrect version of Table 2 was printed in the above article. The corrected version is shown below.     

Impact of cancer surgery slowdowns on patient survival during the COVID-19 pandemic: a microsimulation modelling study

Background:With the declaration of the global pandemic, surgical slowdowns were instituted to conserve health care resources for anticipated surges in patients with COVID-19. The long-term implications on survival of these slowdowns for patients with cancer in Canada is unknown.Methods:We constructed a microsimulation model based on real-world population data on cancer care from Ontario, Canada, from 2019 and 2020. Our model estimated wait times for cancer surgery over a 6-month period during the pandemic by simulating a slowdown in operating room capacity (60% operating room resources in month 1, 70% in month 2, 85% in months 3–6), as compared with simulated prepandemic conditions with 100% resources. We used incremental differences in simulated wait times to model survival using per-day hazard ratios for risk of death. Primary outcomes included life-years lost per patient and per cancer population. We conducted scenario analyses to evaluate alternative, hypothetical scenarios of different levels of surgical slowdowns on risk of death.Results:The simulated model population comprised 22 799 patients waiting for cancer surgery before the pandemic and 20 177 patients during the pandemic. Mean wait time to surgery prepandemic was 25 days and during the pandemic was 32 days. Excess wait time led to 0.01–0.07 life-years lost per patient across cancer sites, translating to 843 (95% credible interval 646–950) life-years lost among patients with cancer in Ontario.Interpretation:Pandemic-related slowdowns of cancer surgeries were projected to result in decreased long-term survival for many patients with cancer. Measures to preserve surgical resources and health care capacity for affected patients are critical to mitigate unintended consequences.

Declaration of the global COVID-19 pandemic led to the implementation of several clinical and policy-related measures to mitigate risk to vulnerable populations and conserve health care resources. Literature from early waves of the pandemic characterized patients with cancer as a vulnerable population.^1,2 Moreover, cancer surgery can be highly resource intensive, which could strain the health care system’s ability to respond to the pandemic. Accordingly, in March 2020, the Ontario government recommended reducing the number of cancer surgeries, along with other elective surgeries performed in the province. These measures were aimed at reducing both patient morbidity and use of health care resources, primarily by decreasing routine postoperative admissions to wards and intensive care units, in anticipation of a potential surge of patients with COVID-19.³Although necessary, this initial strategy resulted in a backlog of cancer surgeries, and some patients faced longer wait times to surgical treatment.⁴ Given clear evidence showing that longer surgical wait times can increase cancer-related risk of death, there is concern for the unintended consequences of the surgical slowdowns during the COVID-19 pandemic.^5–8 International data have projected the negative impact on long-term survival associated with potential delays to cancer diagnosis or surgery across various cancer types.^9–11 Recognizing the global differences in level of infection, response to the COVID-19 pandemic and cancer survival rates, country-specific data are required to understand local consequences and better guide future responses to times of resource constraint. As such, the objective of the current study was to evaluate the long-term implications of pandemic–related cancer surgery slowdowns on cancer survival in Ontario, Canada.     

Geographical and temporal variation in the diet of Bank Cormorants Phalacrocorax neglectus in South Africa

The Bank Cormorant Phalacrocorax neglectus is endemic to the Benguela upwelling ecosystem off southwest Africa and is classified as Endangered owing to a recent large reduction in its number. It is thought that food scarcity, including a decreased abundance of West Coast rock lobster Jasus lalandii, has been a major driver of the decrease, yet its diet in South Africa is poorly known. We collected 941 pellets regurgitated by Bank Cormorants, at 18 South African breeding colonies during 1975–1985, and 1 523 pellets at 17 colonies during 1995–2002. The species composition of the diet (% numbers) was significantly different between the two periods, with widespread decreases in proportions of rock lobster in the west and of octopus and cuttlefish Sepia spp. at most localities. These taxa were replaced in the diet by fish, including Gobiidae and Clinidae. The pelagic goby Sufflogobius bibarbatus, an important prey of Bank Cormorants in Namibia, was absent from pellets collected in 1975–1985 but common at northern localities from 1995–2002. Composition of the diet by frequency of occurrence was only determined for 1995–2002, when rock lobster was present in 67% of all samples collected, cuttlefish in 39%, and Clinidae in 32%. Data for 1975–1985 and 1995–2002 showed that carapace lengths of rock lobsters eaten by Bank Cormorants averaged 56 mm (range 22–82 mm) and 50 mm (range 22–75 mm), respectively, which compares to the minimum legal size of 75 mm for fisheries in South Africa. This energy- rich prey item was an important constituent of the diet in the winter breeding period.