Deconstructing age estimates for angiosperms

Estimates of the age of angiosperms from molecular phylogenies vary considerably. As in all estimates of evolutionary timescales from phylogenies, generating these estimates requires assumptions about the rate that molecular sequences are evolving (using clock models) and the time duration of the branches in a phylogeny (using fossil calibrations and branching processes). Often, it is difficult to demonstrate that these assumptions reflect current knowledge of molecular evolution or the fossil record. In this study we re-estimate the age of angiosperms using a minimal set of assumptions, therefore avoiding many of the assumptions inherent to other methods. The age estimates we generate are similar for each of the four datasets analysed, ranging from 130 to 400 Ma, but are far less precise than in previous studies. We demonstrate that this reduction in precision results from making less stringent assumptions about both rate and time, and that the analysed molecular dataset has very little effect on age estimates

Rebuttal to “(2786) Proposal to change the conserved type of Ipomoea, nom. cons. (Convolvulaceae)”

A rebuttal to the proposal to change the conserved type of Ipomoea is presented. We argue the proposal is unnecessary and has no basis in evidence or precedent that justifies its approval

The relationship between entrepreneurial competencies and the recurring entrepreneurial intention and action of existing entrepreneurs

BACKGROUND : Many scholars focus their research efforts on the entrepreneurial intention of students and non-entrepreneurs, yet most of these scholars found empirical evidence that intention does not necessarily lead these individuals to start businesses (entrepreneurial action). Possible explanations for this could be that: (1) previous studies focused on the wrong samples; (2) they measured entrepreneurial intention as a single construct; and (3) there is a missing link between intention and action. AIM: To address these gaps, we determine the relationship between recurring entrepreneurial intention attitudes and action as well as entrepreneurial intention behaviours and action of 154 existing entrepreneurs in South Africa. By focusing on a sample of existing entrepreneurs who have already started a business, we shed light on the set of entrepreneurial competencies as a missing link between intention and action. This article is of academic importance as it focuses on the recurring process that entrepreneurs follow instead of the initial intention that is often overemphasised in literature. As far as could be determined, no other studies have investigated the relationships between entrepreneurial competencies, recurring entrepreneurial intention attitudes, recurring entrepreneurial intention behaviours and recurring entrepreneurial action. SETTING: The research was conducted on 154 existing entrepreneurs in South Africa. METHODS: A self-administered survey was used and the findings indicate that entrepreneurial competencies have a positive relationship with recurring entrepreneurial action, recurring entrepreneurial intention behaviours and recurring entrepreneurial intention attitudes. RESULTS: There was no significant relationship between entrepreneurial action and recurring entrepreneurial intention behaviours. This is an unexpected finding as a positive relationship was expected for a sample that had prior entrepreneurial experience and already engaged in prior behaviours. However, this study contributes to the entrepreneurial intention–action literature by suggesting that existing entrepreneurs with recurring intention should also be measured in these relationships, in comparison to other research that mainly focused on the intentions of students and non-entrepreneurs. CONCLUSION: The practical contribution of this article is in the identification of specific entrepreneurial competencies, such as creative problem-solving, opportunity recognition and value creation that existing entrepreneurs relied on the most when engaging in entrepreneurial action. Potential, nascent, existing and serial entrepreneurs could focus on these competencies if they wish to engage in entrepreneurial action as well as recurring entrepreneurship.https://sajesbm.co.zapm2020Business Managemen

Atlantic bluefin tuna : a novel multistock spatial model for asessing population biomass

© The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 6 (2011): e27693, doi:10.1371/journal.pone.0027693.Atlantic bluefin tuna (Thunnus thynnus) is considered to be overfished, but the status of its populations has been debated, partly because of uncertainties regarding the effects of mixing on fishing grounds. A better understanding of spatial structure and mixing may help fisheries managers to successfully rebuild populations to sustainable levels while maximizing catches. We formulate a new seasonally and spatially explicit fisheries model that is fitted to conventional and electronic tag data, historic catch-at-age reconstructions, and otolith microchemistry stock-composition data to improve the capacity to assess past, current, and future population sizes of Atlantic bluefin tuna. We apply the model to estimate spatial and temporal mixing of the eastern (Mediterranean) and western (Gulf of Mexico) populations, and to reconstruct abundances from 1950 to 2008. We show that western and eastern populations have been reduced to 17% and 33%, respectively, of 1950 spawning stock biomass levels. Overfishing to below the biomass that produces maximum sustainable yield occurred in the 1960s and the late 1990s for western and eastern populations, respectively. The model predicts that mixing depends on season, ontogeny, and location, and is highest in the western Atlantic. Assuming that future catches are zero, western and eastern populations are predicted to recover to levels at maximum sustainable yield by 2025 and 2015, respectively. However, the western population will not recover with catches of 1750 and 12,900 tonnes (the “rebuilding quotas”) in the western and eastern Atlantic, respectively, with or without closures in the Gulf of Mexico. If future catches are double the rebuilding quotas, then rebuilding of both populations will be compromised. If fishing were to continue in the eastern Atlantic at the unregulated levels of 2007, both stocks would continue to decline. Since populations mix on North Atlantic foraging grounds, successful rebuilding policies will benefit from trans-Atlantic cooperation.This work was supported by grants from the TAG A Giant Foundation, the Monterey Bay Aquarium Foundation, the Lenfest Ocean Program, Washington, DC, USA, the Canadian Fisheries and Oceans International Governance Strategies Fund and the National Oceanic and Atmospheric Administration (NOAA) of the United States

Preliminary management strategy evaluation for blue shark in the Indian Ocean using a data-limited approach

In tuna-RFMOs there has been an effort to move to quantitative stock assessments for pelagic sharks, especially for the main species such as blue shark Prionace glauca. In IOTC, blue shark was last assessed in 2017 with the use of an integrated length-based age-structured model (SS3). This paper now presents a preliminary exercise with data-limited Management Strategy Evaluation (MSE) to test options for different potential management procedures (MPs), using the data-limited methods toolkit (DLMtool). Reference points have not yet been adopted for sharks in IOTC, so for this exercise we set some tentative reference points noting that those can be updated in the future as needed. Eighty-nine MPs were evaluated with 9 considered potentially acceptable. Options and tradeoffs between those MPs are shown and described in the paper. We have focused mainly on trade-offs between biomass and yield, but according to the management objectives agreed other performance metrics can be applied. Even thought this is a preliminary exercise at this point, we hope that it provides initial thoughts and opens the discussion for the advancement of the blue shark management and conservation in the Indian Ocean

Improving management of a mid-Atlantic coastal barrier island through assessment of habitat condition

AbstractTo achieve desired environmental outcomes, environmental condition and trends need to be rigorously measured and communicated to resource managers, scientists, and a broader general audience. However, there is often a disconnect between responsive ecosystem monitoring and decision making for strategic long-term management. This project demonstrates how historical monitoring data can be synthesized and used for future planning and decision making, thereby closing the management feedback cycle. This study linked disparate datasets, collected for a variety of purposes and across multiple temporal and spatial scales, in order to assess and quantify current habitat conditions. The results inform integrated resource management decision-making at Assateague Island National Seashore (Maryland and Virginia, USA) by using ecological reference conditions to identify monitoring needs, areas of high vulnerability, and areas with potential for improved management. The approach also provides a framework that can be applied in the future to assess the effectiveness of these management decisions on the condition of island habitats, and is a replicable demonstration of incorporating diverse monitoring datasets into an adaptive management cycle

Phylogenomics and the rise of the angiosperms

Angiosperms are the cornerstone of most terrestrial ecosystems and human livelihoods1, 2. A robust understanding of angiosperm evolution is required to explain their rise to ecological dominance. So far, the angiosperm tree of life has been determined primarily by means of analyses of the plastid genome3, 4. Many studies have drawn on this foundational work, such as classification and first insights into angiosperm diversification since their Mesozoic origins5–7. However, the limited and biased sampling of both taxa and genomes undermines confidence in the tree and its implications. Here, we build the tree of life for almost 8,000 (about 60%) angiosperm genera using a standardized set of 353 nuclear genes8. This 15-fold increase in genus-level sampling relative to comparable nuclear studies9 provides a critical test of earlier results and brings notable change to key groups, especially in rosids, while substantiating many previously predicted relationships. Scaling this tree to time using 200 fossils, we discovered that early angiosperm evolution was characterized by high gene tree conflict and explosive diversification, giving rise to more than 80% of extant angiosperm orders. Steady diversification ensued through the remaining Mesozoic Era until rates resurged in the Cenozoic Era, concurrent with decreasing global temperatures and tightly linked with gene tree conflict. Taken together, our extensive sampling combined with advanced phylogenomic methods shows the deep history and full complexity in the evolution of a megadiverse clade