Ecology of Laridae under conditions of unstable hydrological regime: colony sizes and synchronization of reproduction

The problem of criteria for distinguishing colonies from similar socio-demographic structures (mainly in terms of nesting density) is highly relevant and has remained in the focus of attention of ornithologists for a long time. The synchronization of reproduction in a colony is one of the criteria which require special development. Based on particular works (1972–2005), I present synchronization of the reproduction of gulls in colonies of different sizes. In contrast to previous studies, this paper uses a specially developed Index of Synchronization of Bird Breeding (Isr) to study this phenomenon, making it relatively easy to determine its level. The index distinguishes between different species of birds of this group: 75.7% (white-winged black tern) and 97.6% (black-headed gull) of the total variability of synchronization of breeding birds in colonies. Frequent failure of nesting attempts often causes repeated (compensatory) reproduction, which in the case of a mass manifestation significantly reduces the synchronization of the nesting period in colonies and thus significantly reduces this indicator. It is proved that a higher synchronization of reproduction characterizes small colonies (up to 50 nests). In all species of gulls, the beginning of reproduction in different colonies differs in terms of the appearance of the first eggs by 1–10 days and at the beginning of mass egg-laying – by 1–18 days. To the same extent, they differ in the timing of the hatching of eggs. In small colonies, the total egg-laying period is shorter by 34.9–49.7% compared to larger colonies. My observations show that large colonies are formed by the nesting of several small colonies on one plot. This phenomenon is noticeable during periods of mass re-nesting of birds after a high loss of nests (up to 69.5% or more) because of severe flooding. Differences in the breeding periods of colonies that differ in size appear when several small colonies with different breeding periods of birds are combined into one larger colony. This phenomenon is well detected in the formation of several sub-colonies and in the differences in the timing of reproduction of different parts of a large colony.

Microbiota Influences Fitness and Timing of Reproduction in the Fruit Fly Drosophila melanogaster

The ability of associated microorganisms (“microbiota”) to influence animal life history traits has been recognized and investigated, especially in the past 2 decades. For many microbial communities, there is not always a clear definition of whether the microbiota or its members are beneficial, pathogenic, or relatively neutral to their hosts’ fitness.

Primary Characterization of a Life-Cycle Mutant akasusabi of the Red Alga Neopyropia yezoensis

Gametophyte-to-sporophyte transition in the haploid-diploid life cycle depends on fertilization of male and female gametes. We describe here a mutant of the marine red seaweed Neopyropia yezoensis, designated akasusabi (aks), where the gametophyte-to-sporophyte transition occurs independently of fertilization. Although conchocelis filaments were produced from carpospores, severe defects in the maturation of carposporangia via mitosis to generate conchospores were observed. In the aks mutant, however, somatic cells of gametophytic thalli were able to produce conchocelis filaments without fertilization. Thus, apogamy occurs in aks. In addition, aks was highly sensitive to wounding that promotes both asexual and apogamous reproductive responses by producing spores, which develop either into blades or conchocelis filaments, indicating that aks responds to wounding by enhanced reproduction. These findings indicated that the aks mutation enables the transformation of vegetative cells to carpospores to produce sporophytes by apogamy and wound-inducible life cycle trade-off, stimulating a reset of the timing of reproduction during the life cycle. Therefore, AKS is involved in regulations of the gametophyte-to-sporophyte transition and asexual spore production in N. yezoensis.

Post-diapause transcriptomic restarts: insight from a high-latitude copepod

Background Diapause is a seasonal dormancy that allows organisms to survive unfavorable conditions and optimizes the timing of reproduction and growth. Emergence from diapause reverses the state of arrested development and metabolic suppression returning the organism to an active state. The physiological mechanisms that regulate the transition from diapause to post-diapause are still unknown. In this study, this transition has been characterized for the sub-arctic calanoid copepod Neocalanus flemingeri, a key crustacean zooplankter that supports the highly productive North Pacific fisheries. Transcriptional profiling of females, determined over a two-week time series starting with diapausing females collected from > 400 m depth, characterized the molecular mechanisms that regulate the post-diapause trajectory. Results A complex set of transitions in relative gene expression defined the transcriptomic changes from diapause to post-diapause. Despite low temperatures (5–6 °C), the switch from a “diapause” to a “post-diapause” transcriptional profile occurred within 12 h of the termination stimulus. Transcriptional changes signaling the end of diapause were activated within one-hour post collection and included the up-regulation of genes involved in the 20E cascade pathway, the TCA cycle and RNA metabolism in combination with the down-regulation of genes associated with chromatin silencing. By 12 h, females exhibited a post-diapause phenotype characterized by the up-regulation of genes involved in cell division, cell differentiation and multiple developmental processes. By seven days post collection, the reproductive program was fully activated as indicated by up-regulation of genes involved in oogenesis and energy metabolism, processes that were enriched among the differentially expressed genes. Conclusions The analysis revealed a finely structured, precisely orchestrated sequence of transcriptional changes that led to rapid changes in the activation of biological processes paving the way to the successful completion of the reproductive program. Our findings lead to new hypotheses related to potentially universal mechanisms that terminate diapause before an organism can resume its developmental program.

Risk-taking behaviour as a central concept in evolutionary biology

Predation is a common cause of mortality, having resulted in the evolution of a diverse kind of anti-predator behaviour across the animal kingdom. One such key behaviour is flight initiation distance (FID), defined as the distance at which animals take flight, when approached by a potential predator such as a human. Extensive research during the past two decades has revealed that optimal anti-predator behaviour is adjusted to life history (the combination of timing of reproduction, fecundity, survivorship, and others). FID is heritable, responds to natural selection and hence shows rapid micro-evolutionary change when animals are exposed to domestication, climate warming, or when introduced to novel environments. Peri-personal space (PPS) and inter-personal space (IPS) may be linked to FID, opening up the possibility of studying these disparate components of behaviour in a common context. Here, I provide a brief review of the extensive literature on FID, but much less well-studied PPS and IPS, and suggest ways in which such behaviour can provide insights into the evolution of anti-predator behaviour and life history. Such knowledge may help us resolve problems in conservation, effects of human disturbance on wild animals, problems of anti-predator behaviour for animal welfare, and potentially even maladaptive anti-predator behaviour and PPS and IPS in humans.

Diapause vs. reproductive programs: transcriptional phenotypes in a keystone copepod

Many arthropods undergo a seasonal dormancy termed “diapause” to optimize timing of reproduction in highly seasonal environments. In the North Atlantic, the copepod Calanus finmarchicus completes one to three generations annually with some individuals maturing into adults, while others interrupt their development to enter diapause. It is unknown which, why and when individuals enter the diapause program. Transcriptomic data from copepods on known programs were analyzed using dimensionality reduction of gene expression and functional analyses to identify program-specific genes and biological processes. These analyses elucidated physiological differences and established protocols that distinguish between programs. Differences in gene expression were associated with maturation of individuals on the reproductive program, while those on the diapause program showed little change over time. Only two of six filters effectively separated copepods by developmental program. The first one included all genes annotated to RNA metabolism and this was confirmed using differential gene expression analysis. The second filter identified 54 differentially expressed genes that were consistently up-regulated in individuals on the diapause program in comparison with those on the reproductive program. Annotated to oogenesis, RNA metabolism and fatty acid biosynthesis, these genes are both indicators for diapause preparation and good candidates for functional studies.

Is energetics or competition a stronger driver of male smallmouth bass seasonal reproductive timing?

ABSTRACTIntraspecific competitive ability is often associated with body size and has been shown to influence reproductive timing in many species. However, energetic constraints provide an alternative explanation for size-related differences of reproductive timing. In temperate fishes that experience a winter starvation period, for instance, a negative allometric relationship between body size and winter energy loss might explain why larger males spawn earlier in a season than smaller males, especially in fishes that exhibit paternal care, which is energetically costly and limits parental foraging opportunities. Male smallmouth bass, Micropterus dolomieu, defend nesting territories in which they care for offspring over an extended period. In northern populations, males rely on energy reserves over a winter starvation period and in spring must recoup energy losses before initiating reproduction, making them ideal systems in which to study contributions of competition and energetic allometry on differences of reproductive timing. Here, we harness data on parental male M. dolomieu from a 10-year study and show that larger males required fewer degree days-a measure of thermal energy experienced-in spring before they spawned each year and that the time of peak seasonal reproduction in the population was negatively related to the number of degree days accumulated before reproduction started. Furthermore, we found that growth of individual males between seasons better predicted changes in timing of reproduction than changes in size relative to competitors. Together, these results suggest that timing of reproduction in this population is more strongly influenced by energetic constraints than size-based competition amongst males.

In a warming river, natural-origin Chinook salmon spawn later but hatchery-origin conspecifics do not

Median timing of reproduction in salmonid populations is generally consistent among years, reflecting long-term patterns of natural selection from characteristics of the local environment. However, altered selection from factors related to climate change or human intervention might shift timing over generations, with implications for the population’s persistence. To study these processes, we modeled median timing of redd (nest) counts as an index of spawning timing by natural-origin Chinook salmon (Oncorhynchus tshawytscha) in the Skagit River system in Washington State, USA. Over the last 2–6 decades, natural-origin salmon have been spawning later by 0.03–0.52 days·year–1, while a naturally spawning group that is influenced by strays from a hatchery has been spawning earlier by 0.19 days·year–1. Trends in the spawning timing of hatchery-origin strays may reflect opposing selection from the hatchery, where egg take for propagation has become earlier by 0.58 days·year–1. As mean August river temperatures have risen over the period of record, hatchery timing trends may be moving in the opposite direction from the plastic or adaptive patterns expressed by natural-origin fish.