The theory of precautionary saving is shown in this paper to be isomorphic to the Arrow-Pratt theory of risk aversion, making possible the application of a large body of knowledge about risk aversion to precautionary saving, and more generally, to the theory of optimal choice under risk In particular, a measure of the strength of precautionary saving motive analogous to the Arrow-Pratt measure of risk aversion is used to establish a number of new propositions about precautionary saving, and to give a new interpretation of the Oreze-Modigliani substitution effect

Precautionary Saving in the Small and in the Large

https://www.cell.com/current-biology/pdf/S0960-9822(12)01138-4.pdf

The magnitude of global marine species diversity

In the last decade, new methods of estimating global species richness have been developed and existing ones improved through the use of more appropriate statistical tools and new data. Taking the mean of most of these new estimates indicates that globally there are approximately 1.5 million, 5.5 million, and 7 million species of beetles, insects, and terrestrial arthropods, respectively. Previous estimates of 30 million species or more based on the host specificity of insects to plants now seem extremely unlikely. With 1 million insect species named, this suggests that 80% remain to be discovered and that a greater focus should be placed on less-studied taxa such as many families of Coleoptera, Diptera, and Hymenoptera and on poorly sampled parts of the world. DNA tools have revealed many new species in taxonomically intractable groups, but unbiased studies of previously well-researched insect faunas indicate that 1–2% of species may be truly cryptic.

How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth

Ecologists and evolutionary biologists are increasingly using big-data approaches to tackle questions at large spatial, taxonomic, and temporal scales. However, despite recent efforts to gather two centuries of biodiversity inventories into comprehensive databases, many crucial research questions remain unanswered. Here, we update the concept of knowledge shortfalls and review the tradeoffs between generality and uncertainty. We present seven key shortfalls of current biodiversity data. Four previously proposed shortfalls pinpoint knowledge gaps for species taxonomy (Linnean), distribution (Wallacean), abundance (Prestonian), and evolutionary patterns (Darwinian). We also redefine the Hutchinsonian shortfall to apply to the abiotic tolerances of species and propose new shortfalls relating to limited knowledge of species traits (Raunkiaeran) and biotic interactions (Eltonian). We conclude with a general framework for the combined impacts and consequences of shortfalls of large-scale biodiversity knowledge f...

Seven Shortfalls that Beset Large-Scale Knowledge of Biodiversity

Reconstructing the phylogenetic relationships that unite all lineages (the tree of life) is a grand challenge. The paucity of homologous character data across disparately related lineages currently renders direct phylogenetic inference untenable. To reconstruct a comprehensive tree of life, we therefore synthesized published phylogenies, together with taxonomic classifications for taxa never incorporated into a phylogeny. We present a draft tree containing 2.3 million tips-the Open Tree of Life. Realization of this tree required the assembly of two additional community resources: (i) a comprehensive global reference taxonomy and (ii) a database of published phylogenetic trees mapped to this taxonomy. Our open source framework facilitates community comment and contribution, enabling the tree to be continuously updated when new phylogenetic and taxonomic data become digitally available. Although data coverage and phylogenetic conflict across the Open Tree of Life illuminate gaps in both the underlying data available for phylogenetic reconstruction and the publication of trees as digital objects, the tree provides a compelling starting point for community contribution. This comprehensive tree will fuel fundamental research on the nature of biological diversity, ultimately providing up-to-date phylogenies for downstream applications in comparative biology, ecology, conservation biology, climate change, agriculture, and genomics.

/pdf/synthesis-of-phylogeny-and-taxonomy-into-a-comprehensive-3f5xhgpe57.pdf

Synthesis of phylogeny and taxonomy into a comprehensive tree of life

We found that trends in the rate of description of 580,000 marine and terrestrial species, in the taxonomically authoritative World Register of Marine Species and Catalogue of Life databases, were similar until the 1950s. Since then, the relative number of marine to terrestrial species described per year has increased, reflecting the less explored nature of the oceans. From the mid-19th century, the cumulative number of species described has been linear, with the highest number of species described in the decade of 1900, and fewer species described and fewer authors active during the World Wars. There were more authors describing species since the 1960s, indicating greater taxonomic effort. There were fewer species described per author since the 1920s, suggesting it has become more difficult to discover new species. There was no evidence of any change in individual effort by taxonomists. Using a nonhomogeneous renewal process model we predicted that 24-31% to 21-29% more marine and terrestrial species remain to be discovered, respectively. We discuss why we consider that marine species comprise only 16% of all species on Earth although the oceans contain a greater phylogenetic diversity than occurs on land. We predict that there may be 1.8-2.0 million species on Earth, of which about 0.3 million are marine, significantly less than some previous estimates. (Biodiversity; biogeography; deep-sea modeling; macroecology; marine; taxonomy; terrestrial.)

/pdf/predicting-total-global-species-richness-using-rates-of-57kx1b04jy.pdf

Predicting Total Global Species Richness Using Rates of Species Description and Estimates of Taxonomic Effort

Recent studies show that there are more taxonomists describing species in recent decades than before. However, whether the rate of increase in number of taxonomists is greater than the rate of new species description has been questioned. We found a statistically significant decline in the proportion of species being described per number of taxonomists (i.e., authors of recent species descriptions) during the past century for (i) families of insects that had been stated not to show this trend and (ii) a sample of over 0.5 million marine, terrestrial, and freshwater species. We suggest that this decreased “catch” of species per taxonomic effort, despite scientists’ greater ability to explore and sample habitats, means it is getting harder to discover new species and supports recent studies suggesting that

More Taxonomists Describing Significantly Fewer Species per Unit Effort May Indicate That Most Species Have Been Discovered

Factors influencing when species are first named and estimating global species richness

A growing literature shows that there are more people describing species new to science than ever before, that this is not due to multiple authorships of papers, and that the proportions of people (i.e. taxonomists) who describe many or only one species in their life-time has not changed. These data also show that there is a decreasing number of new species described in proportion to the number of taxonomists. Although descriptions are generally now more comprehensive and may take more time, this may be offset by modern efficiencies in field, laboratory and publication methods. We explain how the analyses of Bebber et al. (2014) support these findings; contrary to the tone of their paper. They conclude that c. 75% of flowering plant species have been described, and because of synonyms that the total number of 350 000 plant species may not change. This further supports our interpretation of the decreasing species catch per unit effort as an indication that most (c. 2/3) of species have been named and thus there are 2–3 million species on Earth.

https://nph.onlinelibrary.wiley.com/doi/pdf/10.1111/nph.12689

Further evidence of more taxonomists discovering new species, and that most species have been named: response to Bebber et al. (2014)

http://www.tara.tcd.ie/bitstream/handle/2262/63770/Nonparametric%20Predictive%20Utility%20Inference.pdf;sequence=1

Brett Houlding

Papers

Predicting Total Global Species Richness Using Rates of Species Description and Estimates of Taxonomic Effort

More Taxonomists Describing Significantly Fewer Species per Unit Effort May Indicate That Most Species Have Been Discovered

Factors influencing when species are first named and estimating global species richness

Further evidence of more taxonomists discovering new species, and that most species have been named: response to Bebber et al. (2014)

Nonparametric predictive utility inference