COVID-19 and “natural” experiments arising from physical distancing: a hypothetical case study from chronobiology

ABSTRACT

With countless “natural” experiments triggered by the COVID-19-associated physical distancing, one key question comes from chronobiology: “When confined to homes, how does the reduced exposure to natural daylight arising from the interruption of usual outdoor activities plus lost temporal organization ordinarily provided from workplaces and schools affect the circadian timing system (the internal 24 h clock) and, consequently, health of children and adults of all ages?” Herein, we discuss some ethical and scientific facets of exploring such natural experiments by offering a hypothetical case study of circadian biology.     

Temporal patterns of breeding and recruitment in Nerophis lumbriciformis(Pisces; Syngnathidae) related to seawater temperatures

The breeding season of Nerophis lumbriciformis , a cold water pipefish, was positively correlated with seawater temperatures <15·5° C, whilst recruitment occurred at the end of the upwelling season, when seawater temperature attained its maximum values. The observed alterations in seawater temperatures, with steady year‐round increases, and the consequent alteration of the upwelling regime, may have dramatic consequences in the maintenance of N. lumbriciformis populations, by reducing the breeding period and simultaneously contributing to the transport of pelagic larvae northwards due to specific sea currents that occur outside the upwelling season.     

Preference and performance of the hyperparasitoid Syrphophagus aphidivorus (Hymenoptera: Encyrtidae): fitness consequences of selecting hosts in live aphids or aphid mummies

Abstract.  1. Theoretical models predict that ovipositional decisions of parasitoid females should lead to the selection of the most profitable host for parasitoid development. Most parasitoid species have evolved specific adaptations to exploit a single host stage. However, females of the aphid hyperparasitoid Syrphophagous aphidivorus (Mayr) (Hymenoptera: Encyrtidae) display a unique and atypical oviposition behaviour by attacking either primary parasitoid larvae in live aphids, or parasitoid pupae in dead, mummified aphids.
2. In the laboratory, the correlation between host suitability and host preference of S. aphidivorus on the host Aphidius nigripes Ashmead parasitising the aphid Macrosiphum euphorbiae (Thomas) was investigated.
3. The relative suitability of the two host stages was determined by measuring hyperparasitoid fitness parameters (survival, development time, fecundity, sex ratio, and adult size of progeny), and calculating the intrinsic rate of population increase ( r _m). Host preference by S. aphidivorus females and the influence of aphid defence behaviour on host selection was also examined.
4. Hyperparasitoid offspring performance was highest when developing from hosts in aphid mummies and females consistently preferred this host to hosts in parasitised aphids. Although aphid defensive behaviour may influence host selection, it was not a determining factor. Ecological and evolutionary processes that might have led to dual oviposition behaviour in S. aphidivorus are discussed.     

Evolutionary relationships among hares from North Africa (Lepus sp. or Lepus spp.), cape hares (L. capensis) from South Africa, and brown hares (L. europaeus), as inferred from mtDNA PCR-RFLP and allozyme data

Systematics and taxonomy of hares of the genus Lepus (Lagomorpha) are under contentious debate, and phylogenetic relationships among many taxa are not well understood. Here we study genetic differentiation and evolutionary relationships among North African hares, currently considered subspecies of Lepus capensis , cape hares ( L. capensis ) from the Cape province in South Africa, and brown hares ( L. europeaus ) from Europe and Anatolia, using maternally (mtDNA) and biparentally (allozymes) inherited markers. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of a c. 1.8 kb long segment of the mitochondrial control region using eight hexanucleotide-recognizing restriction endonucleases yielded 28 haplotypes, and horizontal starch gel electrophoresis of proteins encoded by 25 structural gene loci revealed 52 alleles at 18 polymorphic loci. Diverse phylogenetic analyses (neighbor joining dendrogram, median joining network, multidimensional scaling of pairwise distances, AMOVA, F -statistics, hierarchical F -statistics) of genetic variants revealed marked substructuring of mtDNA into three phylogeographic groups, namely an African, a central European, and an Anatolian, but a somewhat less pronounced overall differentiation of the nuclear genome, despite a relatively high number of population-specific (private) alleles. However, all our results are not incongruent with Petter's (1959: Mammalia 23 , 41; 1961: Z. f. Säugetierkunde 26 , 30; 1972 : Société Des Sciences Naturelles et Physiques du Maroc 52 , 122) hypothesis that North African hares generally belong to L. capensis and that brown hares should be included in this species as well.     

Wiring diagrams of MAPK regulation by MEKK1, 2, and 3.

Mitogen-activated protein kinase (MAPK) pathways are activated by a plethora of stimuli. The literature is filled with papers describing the activation of different MAPKs by almost any stimulus or insult imaginable to cells. In this review, we use signal transduction wiring diagrams to illustrate putative upstream regulators for the MAPK kinase kinases, MEKK1, 2, and 3. Targeted gene disruption of MEKK1, 2, or 3 defined phenotypes for each MEKK associated with loss of specific MAPK regulation. Genetic analysis of MEKK function clearly defines specific components of the wiring diagram that require MEKK1, 2, or 3 for physiological responses. We propose that signal transduction network wiring diagrams are valuable tools for hypothesis building and filtering physiologically relevant phenotypic responses from less connected protein relations in the regulation of MAPK pathways.     

Possible Phytoplasma Disease in Papaya (Carica papaya L.) from Baja California Sur: Diagnosis by Scanning Electron Microscopy

The symptoms of possible phytoplasma infection in introduced and local varieties of papaya were first noted in the Mexican state of Baja California Sur (BCS) during field surveys in 2002–2003. Phytoplasma structures were observed using scanning electron microscopy (SEM) in phloem sieve elements in diseased papaya plants, but not in healthy plants. They were rounded structures 400–1600 nm in diameter. This is the first report of the possible association of phytoplasmas with diseased papaya plants in BCS. The use of SEM for the primary detection of disease aetiology is discussed.     

Genetic and morphometric differentiation among island populations of two Norops lizards (Reptilia: Sauria: Polychrotidae) on independently colonized islands of the Islas de Bahia (Honduras)

Aim Anole lizards (Reptilia: Sauria: Polychrotidae) display remarkable morphological and genetic differentiation between island populations. Morphological differences between islands are probably due to both adaptive (e.g. differential resource exploitation and intra‐ or interspecific competition) and non‐adaptive differentiation in allopatry. Anoles are well known for their extreme diversity and rapid adaptive speciation on islands. The main aim of this study was to use tests of morphological and genetic differentiation to investigate the population structure and colonization history of islands of the Islas de Bahia, off the coast of Honduras. Location Five populations of Norops bicaorum and Norops lemurinus were sampled, four from islands of the Islas de Bahia and one from the mainland of Honduras. Methods Body size and weight differentiation were measured in order to test for significant differences between sexes and populations. In addition, individuals were genotyped using the amplified fragment length polymorphism technique. Bayesian model‐based and assignment/exclusion methods were used to study genetic differentiation between island and mainland populations and to test colonization hypotheses. Results Assignment tests suggested migration from the mainland to the Cayos Cochinos, and from there independently to both Utila and Roatán, whereas migration between Utila and Roatán was lacking. Migration from the mainland to Utila was inferred, but was much less frequent. Morphologically, individuals from Utila appeared to be significantly different in comparison with all other localities. Significant differentiation between males of Roatán and the mainland was found in body size, whereas no significant difference was detected between the mainland and the Cayos Cochinos. Main conclusions Significant genetic and morphological differentiation was found among populations. A stepping‐stone model for colonization, in combination with an independent migration to Utila and Roatán, was suggested by assignment tests and was compatible with the observed morphological differentiation.