The dynamics of genome size and GC contents evolution in genus Nicotiana

Hybridization and Polyploidization are most common of the phenomenon observed in plants, especially in the genus Nicotiana leading to the duplication of genome. Although genomic changes associated with these events has been studied at various levels but the genome size and GC content variation is less understood because of absence of sufficient genomic data. In this study the flow cytometry technique was used to uncover the genome size and GC contents of 46 Nicotiana species and we compared the genomic changes associated with the hybridization events along evolutionary time scale. The genome size among Nicotiana species varied between 3.28 pg and 11.88 pg whereas GC contents varied between 37.22% and 51.25%. The tetraploid species in genus Nicotiana including section Polydiclae, Repandae, Nicotiana, Rustica and Sauveolentes revealed both up and downsizing in their genome sizes when compared to the sum of genomes of their ancestral species. The genome sizes of three homoploid hybrids were found near their ancestral species. Loss of large genome sequence was observed in the evolutionary more aged species (>10 Myr) as compared to the recently evolved one’s (<0.2 Myr). The GC contents were found homogenous with a mean difference of 2.46% among the Nicotiana species. It is concluded that genome size change appeared in either direction whereas the GC contents were found more homogenous in genus Nicotiana.

Wager on Global Food Prices 2001–2020: Who Won and What Does it Mean?

This paper presents the results of a 2011 wager between Stan Becker and David Lam about the trajectory of world food prices for the period 2011–2020 versus the period 2002–2010. The wager was a response to Lam’s 2011 presidential address to the Population Association of America, which showed that many health and socio-demographic indicators had improved over the previous fifty years, in spite of the addition of four billion people to the world’s population. Lam lost the wager, with the Food and Agriculture Organization’s price index for five food groups averaging about twenty per cent higher for 2011–2020 than for 2001–2010. Becker and Lam discuss the background of the wager, give their differing interpretations of the outcome and discuss future trends in population, food production and food prices. Lam gives a more optimistic perspective on future trends, while Becker raises concerns about rapid degradation of planetary ecosystems, species loss and global warming.

167 Impacts on Biodiversity, Environment and Society of Beef Production in the Mexican Tropics: A Life Cycle Assessment Approach

Beef production exerts strong environmental pressures and can also generate negative social effects. In this study, the impacts on biodiversity, environment and society of beef production in the Mexican tropics, were evaluated through the Life Cycle Assessment (LCA) approach. The functional unit of the study was 1 kg live weight of calf and focused on three productive systems: native silvopastoral (NSP), intensive silvopastoral (ISP) and monoculture (MC). This research was divided into four analysis steps. (1) social impacts; (2) damage to biodiversity; (3) methane emissions and 4) environmental LCA impacts. Using the Social-LCA, we evaluated 18 social indicators, grouped into five categories: human rights, working conditions, health and safety, socio-economic repercussions, and governance. The results showed similarities between the three livestock systems, which revealed a deficient social performance. For projecting the biodiversity damage of pasture land use from an LCA perspective, characterization factors (CFs) were estimated. CFs consist of dimensionless figures representing the potential for damage per unit area of pasture land (potential species loss per m2). The CFs were calculated for three levels of pasture land use intensity (minimal/NSP, light/ISP, intense/MC). Based on the characterization factors developed, the MC showed the least potential species loss. Enteric methane emissions from the production systems were determined using the IPCC Tier 2. The results revealed that the emissions values from enteric methane calculated with Tier 1 overestimated the emissions compared to Tier 2 methodology. LCA indicated a lower environmental impact of the MC on four of the seven categories analyzed, highlighting its lower contribution to climate change and reducing species loss. However, consumption of water and scarcity of fossil fuel resources increased. To achieve tropical sustainable livestock farming, further lines of research should be aimed at evaluating its economic impacts and propose management systems that guarantee better social and environmental performance.

The structure and robustness of tripartite ecological networks

ABSTRACTUntil recently, most ecological network analyses have focused on a single interaction type. In nature, however, diverse interactions co-occur, each of them forming a layer of a ‘multilayer’ network. Data including information on multiple interactions has recently started to emerge, giving us the opportunity to have a first glance at possible commonalities in the structure of these networks. We studied the structural features of 44 tripartite ecological networks from the literature, each composed of two layers of interactions (e.g. herbivory, parasitism, pollination), and investigated their fragility to species losses. We found that the way in which the different layers of interactions are connected to each other affect how perturbations spread in ecological communities. Our results highlight the importance of considering multiple interactions simultaneously to better gauge the robustness of ecological communities to species loss and to more reliably identify the species that are important for robustness.

Maintenance of community function through compensation breaks down over time in a desert rodent community

Understanding the ecological processes that maintain community function in systems experiencing species loss, and how these processes change over time, is key to understanding the relationship between community structure and function and predicting how communities may respond to perturbations in the Anthropocene. Using a 30-year experiment on desert rodents, we show that the impact of species loss on community-level energy use has changed dramatically over time, due to changes in both species composition and in the degree of functional redundancy among the same set of species. Although strong compensation, initially driven by the dispersal of functionally redundant species to the local community, occurred in this system from 1996-2010, since 2010, compensation has broken down due to decreasing functional overlap within the same set of species. Simultaneously, long-term changes in sitewide community composition due to niche complementarity have decoupled the dynamics of compensation from the overall impact of species loss on community-level energy use. These results highlight the importance of explicitly long-term, metacommunity, and eco-evolutionary perspectives on compensatory dynamics, zero-sum constraints, and the link between species-level fluctuations and community function in a changing world.Original submissionThis submission analyzes long-term data on rodent community abundance and energy use from the Portal Project. Sections of this timeseries have been analyzed in numerous other publications, but this is the first to analyze data from 2007-2020 on compensation on experimental and control plots.No prior publicationThis submission is posted as a preprint on bioRxiv at [bioRxiv].Animal welfareRodent censuses were conducted with IACUC approval, most recently under protocol 201808839_01 at the University of Florida.Open researchAll data and code to reproduce these analyses are archived on Zenodo at https://doi.org/10.5281/zenodo.5544362 and https://doi.org/10.5281/zenodo.5539881.Analytic methodsAll analyses were conducted in R version 4.0.3.

Universal scaling of robustness of ecosystem services to species loss

Ensuring reliable supply of services from nature is key to the sustainable development and well-being of human societies. Varied and frequently complex relationships between biodiversity and ecosystem services have, however, frustrated our capacity to quantify and predict the vulnerability of those services to species extinctions. Here, we use a qualitative Boolean modelling framework to identify universal drivers of the robustness of ecosystem service supply to species loss. These drivers comprise simple features of the networks that link species to the functions they perform that, in turn, underpin a service. Together, they define what we call network fragility. Using data from >250 real ecological networks representing services such as pollination and seed-dispersal, we demonstrate that network fragility predicts remarkably well the robustness of empirical ecosystem services. We then show how to quantify contributions of individual species to ecosystem service robustness, enabling quantification of how vulnerability scales from species to services. Our findings provide general insights into the way species, functional traits, and the links between them together determine the vulnerability of ecosystem service supply to biodiversity loss.