In the midst of only the 6th mass extinction in the Earth's history, we must rethink how we teach evolution to prevent natural selection from being incorrectly used as a biological justification for inaction in the face of today's human‐caused mass extinction crisis. Pundits, policy makers, and the general public regularly identify the extinction of endangered species as natural selection at work, rather than attributing modern‐day extinction to the sudden catastrophic bad luck of human caused environmental change, a phenomenon distinct (...) from natural selection. In this natural selection framing, the inability of species to survive in human altered environments is the normal progression of “survival of the fittest” and conservation measures designed to protect species is human interference with natural selection. Paradoxically, this erroneous framing of extinction as the normal course of natural selection ignores humanity's exceptional role in causing today's mass extinction crisis. Our examination of this issue in U.S. college students indicates that it arises from misunderstanding the role of extinction in the history of life, leading us to recommend a greater teaching emphasis on the distinction between extinction and natural selection, and on past mass extinction events. Also see the video abstract here https://youtu.be/29VRyirMdiw. (shrink)

The placozoan Trichoplax adhaerens is a tiny hairy plate and more simply organized than any other living metazoan. After its original description by F.E. Schulze in 1883, it attracted attention as a potential model for the ancestral state of metazoan organization, the “Urmetazoon”. Trichoplax lacks any kind of symmetry, organs, nerve cells, muscle cells, basal lamina, and extracellular matrix. Furthermore, the placozoan genome is the smallest (not secondarily reduced) genome of all metazoan genomes. It harbors a remarkably rich diversity of (...) genes and has been considered the best living surrogate for a metazoan ancestor genome. The phylum Placozoa presently harbors three formally described species, while several dozen “cryptic” species are yet awaiting their description. The phylogenetic position of placozoans has recently become a contested arena for modern phylogenetic analyses and view‐driven claims. Trichoplax offers unique prospects for understanding the minimal requirements of metazoan animal organization and their corresponding malfunctions. (shrink)

Metazoa are one of the great monophyletic groups of organisms. They comprise several major groups of organisms readily recognizable based on their anatomy. These major groups include the Bilateria (animals with bilateral symmetry), Cnidaria (jellyfish, corals and other closely related animals), Porifera (sponges), Ctenophores (comb jellies) and a phylum currently made up of a single species, the Placozoa. Attempts to systematize the relationships of these major groups as well as to determine relationships within the groups have been made for nearly (...) two centuries. Many of the attempts have led to frustration, because of a lack of resolution between and within groups. Other attempts have led to “a new animal phylogeny”. Now, a study by Dunn et al.,1 using the expresssed sequence tag (EST) approach to obtaining high‐throughput large phylogenetic matrices, presents an “even newer” animal phylogeny. There are two major aspects of this study that should be of interest to the general biological community. First, the methods used by the authors to generate their phylogenetic hypotheses call for close examination. Second, the relationships of animal taxa in their resultant trees also prompt further discussion. BioEssays 30:1043–1047, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Graphical AbstractFunding for understanding biodiversity on this planet has had a checkered and unsatisfactory history. There have been some true successes in developing models for assessing biodiversity, but satisfactory governmental and international support has been piecemeal and unsatisfactory. A true solution to the biodiversity crisis will require greater attention from governmental and international funding agencies.

It has been estimated that three species on the planet now go extinct every hour and that this rate is orders of magnitude higher than the planet has seen in previous catastrophic extinction events. We clearly are in the midst of a sixth extinction, and this one is different from the previous five. Why? This sixth extinction is caused by the activity of a single species—us. If there is any hope of ameliorating this extinction, it will entirely be up to (...) us, as the current stewards of this planet, to change the course. There are many challenges, though, to marshaling this effort. Two primary ones immediately come to mind. The first is that we simply haven't found the right biological tools to address this crisis. The second is that many humans on this planet don't even admit we have a problem. These are two very different problems. The first is primarily technological. Only recently has some of the more advanced biologically focused technology been available to conservation biology and extinction science. Humans are enthralled by cutting‐edge technology for the most part, and for the public, one of the more exciting possibilities in the realm of conservation biology is that some of the more charismatic species that have gone extinct might be resurrected through next‐generation technologies. While our discussion will articulate some weaknesses with the de‐extinction approach to conservation biology, we suggest that the “sexiness” of the technologies used in de‐extinction may simultaneously provide a definition of the techniques viable in conservation biology and afford a teachable moment. (shrink)

DNA barcodes, like traditional sources of taxonomic information, are potentially powerful heuristics in the identification of described species but require mindful analytical interpretation. The role of DNA barcoding in generating hypotheses of new taxa in need of formal taxonomic treatment is discussed, and it is emphasized that the recursive process of character evaluation is both necessary and best served by understanding the empirical mechanics of the discovery process. These undertakings carry enormous ramifications not only for the translation of DNA sequence (...) data into taxonomic information but also for our comprehension of the magnitude of species diversity and its disappearance. This paper examines the potential strengths and pitfalls of integrating DNA sequence data, specifically in the form of DNA barcodes as they are currently generated and analyzed, with taxonomic practice. (shrink)

We examine three critical aspects of Popper’s formulation of the ‘ Logic of Scientific Discovery ’—evidence, content and degree of corroboration—and place these concepts in the context of the Tree of Life (ToL) problem with particular reference to molecular systematics. Content, in the sense discussed by Popper, refers to the breadth and scope of existence that a hypothesis purports to explain. Content, in conjunction with the amount of available and relevant evidence, determines the testability, or potential degree of corroboration, of (...) a statement; content distinguishes scientific hypotheses from metaphysical assertions. Degree of corroboration refers to the relative and tentative confidence assigned to one hypothesis over another, based upon the performance of each under critical tests. Here we suggest that systematists attempt to maximize content and evidence to increase the potential degree of corroboration in all phylogenetic endeavors. Discussion of this “total evidence” approach leads to several interesting conclusions about generating ToL hypotheses. (shrink)

The Hawaiian Drosophila have been a model system for evolutionary, ecological, and ethological studies since the inception of the Hawaiian Drosophila Project in the 1960s. Here we review the past and present research on this incredible lineage and provide a prospectus for future directions on genomics and microbial interactions. While the number of publications on this group has waxed and waned over the years, we assert that recent systematic, biogeographic, and ecological studies have reinvigorated Hawaiian Drosophila as an evolutionary model (...) system. The characteristics that distinguish good model clades from good model organisms (e.g., Drosophila melanogaster) are somewhat different so we first define what constitutes a good evolutionary model. We argue that the Hawaiian Drosophila possess many desired aspects of a good evolutionary model, describe how this group of geographically isolated flies have been used in the past, and propose some exciting avenues for future evolutionary research on this diverse, dynamic clade of Drosophila. (shrink)

The placozoan Trichoplax adhaerens has been bridging gaps between research disciplines like no other animal. As outlined in part 1, placozoans have been subject of hot evolutionary debates and placozoans have challenged some fundamental evolutionary concepts. Here in part 2 we discuss the exceptional genetics of the phylum Placozoa and point out some challenging model system applications for the best known species, Trichoplax adhaerens.