Deterministic shifts in molecular evolution correlate with convergence to annualism in killifishes

The repeated evolution of novel life histories correlating with ecological variables offer opportunities to test scenarios of convergence and determinism in genetic, developmental, and metabolic features. Here we leverage the diversity of aplocheiloid killifishes, a clade of teleost fishes that contains over 750 species on three continents. Nearly half of these are annual or seasonal species that inhabit bodies of water that desiccate and are unfeasible for growth, reproduction, or survival for weeks to months at a time. We present a large-scale phylogenomic reconstruction of aplocheiloid killifish evolution using newly sequenced transcriptomes from all major clades. We show that developmental dormancy (diapause) and annualism have up to seven independent origins in Africa and America. We then measure evolutionary rates of orthologous genes and show that annual life history is correlated with higher dN/dS ratios. Many of these fast-evolving genes in annual species constitute key developmental genes and nuclear-encoded metabolic genes that control oxidative phosphorylation. Lastly, we compare these fast-evolving genes to genes associated with developmental dormancy and metabolic shifts in killifishes and other vertebrates and thereby identify molecular evolutionary signatures of repeated evolutionary transitions to extreme environments.

A shift towards the annual habit in selfing Arabidopsis lyrata

An annual life history is often associated with the ability to self-fertilize. However, it is unknown whether the evolution of selfing commonly precedes the evolution of annuality, or vice versa . Using a 2-year common garden experiment, we asked if the evolution of selfing in the normally perennial Arabidopsis lyrata was accompanied by a shift towards the annual habit. Despite their very recent divergence from obligately outcrossing populations, selfing plants exhibited a 39% decrease in over-winter survival after the first year compared with outcrossing plants. Our data ruled out the most obvious underlying mechanism: differences in reproductive investment in the first year did not explain differences in survival. We conclude that transitions to selfing in perennial A. lyrata may be accompanied by a shift towards annuality, but drivers of the process require further investigation.

Diurnal variations in serum metabolites of wintering redheaded buntings

ABSTRACTDaily behavioural and physiological changes in bird may reflect in biofluid metabolite composition. Locomotor activity, food intake and body temperature of group (n=7) of male migratory redheaded buntings held under short days (8L:16D, SD) were monitored besides blood sampling at midday (ZT4: 4 hours zeitgeber time starting ZT0 as lights ‘on’) and midnight (ZT16). The birds exhibited higher activity and increased feeding during daytime with negligible activity and feeding at night. Gas chromatography mass spectrometry and chemo-metric analyses of bird serum revealed higher levels of lipid (palmitic, oleic and linoleic acids) and protein (uric acid and proline) catabolites in daytime serum samples as compared to night samples. Higher night-time levels of short chain fatty acids indicated utilization of glucose and lipolysis in night fasted birds. High night-time levels of taurine, a sulphur amino acid has adaptive advantage to night migratory song birds. The diurnal differences in metabolite patterns suggests differential energy expenditure during day and renders survival benefit to buntings as night migrants. We propose a GCMS method that could be useful to unravel different annual life-history stages including migration.

Foraging and fasting can influence contaminant concentrations in animals: an example with mercury contamination in a free-ranging marine mammal

Large fluctuations in animal body mass in relation to life-history events can influence contaminant concentrations and toxicological risk. We quantified mercury concentrations in adult northern elephant seals ( Mirounga angustirostris ) before and after lengthy at sea foraging trips ( n = 89) or fasting periods on land ( n = 27), and showed that mercury concentrations in blood and muscle changed in response to these events. The highest blood mercury concentrations were observed after the breeding fast, whereas the highest muscle mercury concentrations were observed when seals returned to land to moult. Mean female blood mercury concentrations decreased by 30% across each of the two annual foraging trips, demonstrating a foraging-associated dilution of mercury concentrations as seals gained mass. Blood mercury concentrations increased by 103% and 24% across the breeding and moulting fasts, respectively, demonstrating a fasting-associated concentration of mercury as seals lost mass. In contrast to blood, mercury concentrations in female's muscle increased by 19% during the post-breeding foraging trip and did not change during the post-moulting foraging trip. While fasting, female muscle mercury concentrations increased 26% during breeding, but decreased 14% during moulting. Consequently, regardless of exposure, an animal's contaminant concentration can be markedly influenced by their annual life-history events.

Seasonal cycle of the nest composition in the Ponerine ant Cryptopone sauteri (Hymenoptera: Formicidae)

The annual life history is a basic and important factor in ecological studies on temperate ant species. The biology of Ponerinae species has been studied for many species, but little attention has been paid to their life history. Cryptopone sauteri is one of the most common ants in temperate regions of Japan. However, there is no quantitative information on the life history of this species. We report seasonal changes in brood development, the emergence of reproductives and social structures of C. sauteri. Additionally, we discuss that this species possibly exhibits a polydomous nesting system.

Desiccation plasticity and diapause in the Argentinian pearlfish Austrolebias bellottii

BackgroundThe annual life history strategy with diapauses evolved repeatedly in killifish. To understand their and to characterize their variation between species, patterns of desiccation plasticity seem central. Plasticity might have played a role in the origin of these developmental arrests, when annual fish evolved from non-annual ones. The consequences of desiccation on survival and developmental rates of embryos of annual fish are poorly known. Using detailed demographic modelling of embryonal life histories, we investigate plasticity for desiccation in the Argentinian pearlfish Austrolebias bellottii. The treatment protocol contains changing environmental conditions with successive phases of mild desiccation and rewetting.ResultsWe observed no clear diapause II and thus no increased incidence caused by mild and prolonged desiccation. Embryos arrest development in the pre-hatching stage (DIII) or in the dispersed cell phase (DI) irrespective of environmental conditions. There are limited effects of desiccation on survival, limited developmental delays and an acceleration of development into the pre-hatching stage. We found significant parental variance components on developmental rates, but hardly any effect of parental age. Hatching probabilities increased with age, when embryos had been in air at 100% RH and increased further when embryos were rewetted a second time after a two month interval.ConclusionsMild desiccation and rewetting affect survival, rates of development and hatching probability, but not the fractions of embryos that arrest development in particular stages. We can conclude that the incidences of diapause have become relatively independent of the occurrence of mild desiccation, as if they have become assimilated. In contrast to the responses to mild desiccation observed in the non-annual rivulids, Austrolebias accelerates development into the pre-hatching stage.

Amphibian terrestrial habitat selection and movement patterns vary with annual life-history period

Identification of essential habitat is a fundamental component of amphibian conservation; however, species with complex life histories frequently move among habitats. To better understand dynamic habitat use, we evaluated Wood Frog (Lithobates sylvaticus (LeConte, 1825)) habitat selection and movement patterns during the spring migration and foraging periods and described the spatiotemporal variability of habitats used during all annual life-history periods. We radio-tracked 71 frogs in Maine during 2011–2013 and evaluated spring migration, foraging activity center (FAC), and within-FAC habitat selection. Telemetered frogs spent the greatest percentage of each field season in hibernacula (≥54.4%), followed by FACs (≥25.5%), migration habitat (≥16.9%), and breeding sites (≥4.5%). FACs ranged 49 – 1 335 m2 (568.0 ± 493.4 m2) and annual home ranges spanned 1 413 – 32 165 m2 (11 780.6 ± 12 506.1 m2). During spring migration, Wood Frogs exhibited different movement patterns (e.g., turn angles), selected different habitat features, and selected habitat features less consistently than while occupying FACs, indicating that the migration and foraging periods are ecologically distinct. Habitat-use studies that do not discriminate among annual life-history periods may obscure true ecological relationships and fail to identify essential habitat necessary for sustaining amphibian populations.