The latitudinal position of peak marine diversity in living and fossil biotas

Aim Peak marine taxonomic diversity has only rarely occurred at or near the equator during the Phanerozoic Eon, in contrast to the present‐day pattern. This fundamental difference is difficult to reconcile because the latitude at which peak diversity occurs for living marine taxa has not yet been explicitly determined at a broad taxonomic and spatial scale. Here, we attempt to determine this value in order to compare the contemporary and fossil patterns directly. Location Our data are global in coverage. Methods We used a literature compilation of 149 present‐day marine latitudinal diversity gradients. We summed the number of marine taxa that exhibited peak diversity within 10° latitudinal bins. In addition, we recorded locality data, general habitat (benthic/pelagic), and the taxonomic level of the study organisms. Results We found that peak diversity for most sampled marine taxa currently occurs between 10° and 20° N, even after correcting for a Northern Hemisphere sampling bias. Moreover, this peak position is a global phenomenon: it is found across habitats and higher taxa, within all sampled ocean basins, and on both sides of the Atlantic and Pacific oceans. Benthic taxa, which dominate our data, exhibit one peak at 10°–20° N, while pelagic taxa exhibit a peak at 10°–20° N and an additional peak at 10°–20° S, producing a distinct trough at the equator. Main conclusions Our data indicate that peak marine diversity for many taxa is currently within 10°–20° N rather than at the equator, and that this is not likely to result from either undersampling at lower latitudes or the pattern being dominated by a particular taxon. Possible explanations may include a coincidence with the intertropical convergence zone, a mid‐domain effect, abundant shallow marine habitat, or high ocean temperatures at latitudes nearest the equator. Regardless of its exact cause, the position of peak diversity should be considered a fundamental feature of the latitudinal diversity gradient that must be accounted for within attempts to explain the latter’s existence.     

CLASI-FISH: Principles of combinatorial labeling and spectral imaging

Although the number of phylotypes present in a microbial community may number in the hundreds or more, until recently, fluorescence in situ hybridization has been used to label, at most, only a handful of different phylotypes in a single sample. We recently developed a technique, CLASI-FISH for combinatorial labeling and spectral imaging – fluorescence in situ hybridization, to greatly expand the number of distinguishable taxa in a single FISH experiment. The CLASI technique involves labeling microbes of interest with combinations of probes coupled with spectral imaging to allow the use of fluorophores with highly overlapping excitation and emission spectra. Here, we present the basic principles and theory of CLASI-FISH along with some guidelines for performing CLASI-FISH experiments. We further include a protocol for creating fluorescence spectral reference standards, a vital component of successful CLASI-FISH.     

The Erwin equation of biodiversity: From little steps to quantum leaps in the discovery of tropical insect diversity

Almost 40 years ago, Terry L. Erwin published a seemingly audacious proposition: There may be as many as 30 million species of insects in the world. Here, we translate Erwin's verbal argument into a diversity-ratio model—the Erwin Equation of Biodiversity—and discuss how it has inspired other biodiversity estimates. We categorize, describe the assumptions for, and summarize the most commonly used methods for calculating estimates of global biodiversity. Subsequent diversity-ratio extrapolations have incorporated parameters representing empirical insect specialization ratios, and how insect specialization changes at different spatial scales. Other approaches include macroecological diversity models and diversity curves. For many insect groups with poorly known taxonomies, diversity estimates are based on the opinions of taxonomic experts. We illustrate our current understanding of insect diversity by focusing on the six most speciose insect orders worldwide. For each order, we compiled estimates of the (a) maximum estimated number of species, (b) minimum estimated number of species, and (c) number of currently described species. By integrating these approaches and considering new information, we believe an estimate of 5.5 million species of insects in the world is much too low. New molecular methodologies (e.g., metabarcoding and NGS studies) are revealing daunting numbers of cryptic and previously undescribed species, at the same time increasing our precision but also uncertainty about present estimates. Not until technologies advance and sampling become more comprehensive, especially of tropical biotas, will we be able to make robust estimates of the total number of insect species on Earth.     

Leveraging remote learning during the Covid‐19 pandemic to enhance student understanding of biodiversity

We evaluated whether individual nature‐based ecological (NBE) study used in tandem with group collaboration enhanced undergraduate student understanding of ecological concepts and pro‐environmental perceptions. In response to the Covid‐19 pandemic, we developed a multiweek unit on the latitude diversity gradient (LDG) for fully online instruction that leveraged the unique situation of students learning in disparate geographic locations. Student understanding of the LDG and pro‐environmental perceptions were assessed with surveys administered both pre‐ and post‐activity in an introductory‐level biology laboratory course. Student understanding of the geographic location where biodiversity is the highest was high prior to the start of the laboratory unit and exhibited only a small improvement after the unit. In contrast, students’ higher order thinking around the LDG was enhanced by the lab activity. Student environmental perceptions shifted toward ecocentric views and away from anthropocentric views after the laboratory unit. The greatest gains in ecological understanding and shifts toward ecocentric viewpoints occurred in the group of students who visited their field sites most often. Our results provide further evidence as to the value of NBE for the introductory biology laboratory, even in an online learning setting. The lab unit described in this study provides a potential approach to teaching ecology in an online format that could easily be adapted to fit the needs of a particular curriculum.     

小麦耐盐种质遗传多样性的RAPD分析

选用２２个引物对２４份小麦耐盐种质进行ＲＡＰＤ分析,共产生２００条扩增片段,多态性片段数为１７２条,扩增片段的多态性百分率为８６％,利用ＮＹＳＴＳ软件根据Ｊａｃｃａｒｄ系统分析ＲＡＰＤ结果,并按ＵＰＧＭＡ类平均法进行聚类。２４份材料相似系数在０．２１￣０．９７之间,其中含有多枝赖草、黑麦和偃麦草等外源染色体的多１７４、ＷＲ８３０和南前１２７被分别在３个独立的组,多１７４和南前１２７的亲关系最远,相     

Evaluation of a DNA pooled-sampling strategy for estimating the RFLP diversity of maize populations

Molecular characterization by means of RFLPs of large sets of populations is presently limited by experimental costs. In order to reduce costs, we have evaluated a method based on the RFLP analysis of balanced bulks of DNA from several individuals. The precision of this approach for estimating allele frequencies within each population was investigated using (i) DNA extracted from controlled bulks of leaf tissues of maize inbred lines, (ii) data obtained from individual analyses of 10 maize populations. Both approaches showed that allele frequencies can generally be estimated with a high precision (coefficients of determination up to 0.99 for some probe-enzyme combinations assayed), relative to the variation in allele frequencies observed among maize populations. Although further efforts are needed to define a set of probe-enzyme combinations that can be routinely image processed, these results, and preliminary results from a 65 maize populations project, suggest that this approach could provide highly informative data for large sets of populations, and at relatively low costs.     

Evidence for specificity of cultivable bacteria associated with arbuscular mycorrhizal fungal spores

Bacteria associated with arbuscular mycorrhizal (AM) fungal spores may play functional roles in interactions between AM fungi, plant hosts and defence against plant pathogens. To study AM fungal spore-associated bacteria (AMB) with regard to diversity, source effects (AM fungal species, plant host) and antagonistic properties, we isolated AMB from surface-decontaminated spores of Glomus intraradices and Glomus mosseae extracted from field rhizospheres of Festuca ovina and Leucanthemum vulgare. Analysis of 385 AMB was carried out by fatty acid methyl ester (FAME) profile analysis, and some also identified using 16S rRNA gene sequence analysis. The AMB were tested for capacity to inhibit growth in vitro of Rhizoctonia solani and production of fluorescent siderophores. Half of the AMB isolates could be identified to species (similarity index 0.6) within 16 genera and 36 species. AMB were most abundant in the genera Arthrobacter and Pseudomonas and in a cluster of unidentified isolates related to Stenotrophomonas. The AMB composition was affected by AM fungal species and to some extent by plant species. The occurrence of antagonistic isolates depended on AM fungal species, but not plant host, and originated from G. intraradices spores. AM fungal spores appear to host certain sets of AMB, of which some can contribute to resistance by AM fungi against plant pathogens.     

Detecting DNA polymorphism and genetic diversity in Lentil (Lens culinaris Medik.) germplasm: comparison of ISSR and DAMD marker

Genetic diversity and interrelationships among 31 lentil genotypes were evaluated using 10 Inter-Simple Sequence Repeat (ISSR) and 10 directed amplification of minisatellite DNA region (DAMD) primers. A total of 43 and 48 polymorphic bands were amplified by ISSR and DAMD markers, respectively. Average polymorphism information content (PIC) for ISSR and DAMD markers were 0.37 and 0.41, respectively. All 31 lentil genotypes could be distinguished by ISSR markers into three groups and by DAMD markers into two groups. Various molecular markers show a different efficiency for evaluating DNA polymorphism in lentil and indicate that the patterns of variation are clearly influenced by the genetic marker used. Comparatively, the genetic diversity of examined lentil genotypes by two different marker techniques (ISSR and DAMD) was high and indicated that ISSR and DAMD are effective and promising marker systems for fingerprinting in lentil and give useful information on its genetic relationships.