During the vulnerable stages of early life, most ectothermic animals experience hourly and diel fluctuations in temperature as air temperatures change. While we know a great deal about how different ...constant temperatures impact the phenotypes of developing ectotherms, we know remarkably little about the impacts of temperature fluctuations on the development of ectotherms. In this study, we used a meta-analytic approach to compare the mean and variance of phenotypic outcomes from constant and fluctuating incubation temperatures across reptile species. We found that fluctuating temperatures provided a small benefit (higher hatching success and shorter incubation durations) at cool mean temperatures compared with constant temperatures, but had a negative effect at warm mean temperatures. In addition, more extreme temperature fluctuations led to greater reductions in embryonic survival compared with moderate temperature fluctuations. Within the limited data available from species with temperature-dependent sex determination, embryos had a higher chance of developing as female when developing in fluctuating temperatures compared with those developing in constant temperatures. With our meta-analytic approach, we identified average mean nest temperatures across all taxa where reptiles switch from receiving benefits to incurring costs when incubation temperatures fluctuate. More broadly, our study indicates that the impact of fluctuating developmental temperature on some phenotypes in ectothermic taxa are likely to be predictable via integration of developmental temperature profiles with thermal performance curves.
The social amoeba Dictyostelium discoideum switches between solitary growth and social fruitification depending on nutrient availability. Under starvation, cells aggregate and form fruiting bodies ...consisting of spores and altruistic stalk cells. Once cells socially committed, they complete fruitification, even if a new source of nutrients becomes available. This social commitment is puzzling because it hinders individual cells from resuming solitary growth quickly. One idea posits that traits that facilitate premature de-commitment are hindered from being selected. We studied outcomes of the premature de-commitment through forced refeeding. Our results show that when refed cells interacted with non-refed cells, some of them became solitary, whereas a fraction was redirected to the altruistic stalk, regardless of their original fate. The refed cells exhibited reduced cohesiveness and were sorted out during morphogenesis. Our findings provide an insight into a division of labor of the social amoeba, in which less cohesive individuals become altruists.
•Expansion of urban areas is one of the greatest threats to reptiles.•These findings are contradictory and based solely on lizard species.•Fluctuating asymmetry is used to express developmental ...instability.•Urban land use has a negative effect on development stability of dice snakes.•Human-modified habitats lead to poorer body condition of dice snakes.
The expansion of urban areas leads to a decrease in natural habitats, resulting some species to live in urban environments. Novel environmental factors might influence their size, body condition and development stability. The environmentally induced developmental instability can be indicated by fluctuating symmetry, which means random deviations from perfect symmetry in bilaterally symmetric creatures.
Our research aimed to explore the impact of various urbanization factors on snake populations within urban habitats. To achieve this, we examined how dice snake (Natrix tessellata) populations differ in their asymmetry, body condition and size in a lake characterized by highly modified lakeside habitats, intensive urban land use, and severe human disturbance. The average size, body condition and two asymmetry indices were determined for 25 dice snake populations around Lake Balaton in Hungary. The impacts of the urban environment were characterized by land use and local variables, and the risk of road kill was also estimated.
Populations living in areas with a more intensive road network or near a main road showed more asymmetric traits. It is conceivable that pollutants from vehicle traffic lead to developmental disorders that manifest themselves in more asymmetric individuals. In addition, the body condition of snakes was negatively correlated with the area of the harbours, possibly due to the intensive boat traffic and human disturbance. Finally, populations living in more urbanized areas had larger body sizes meaning that despite its negative effects through pollution, anthropized areas can provide a suitable habitat for dice snakes.
While urban artificial surroundings can function as suitable habitats, our results confirm that urban environmental factors have negative effects on dice snakes. Our findings indicate that the density of road networks and the proximity of roads have adverse effects on the developmental stability of urban snakes. This underscores the need to implement conservation actions to mitigate the negative effects of roads on biodiversity.
Epigenetic processes manage gene expression and products in a real‐time manner, allowing a single genome to display different phenotypes. In this paper, we discussed the relevance of assessing the ...different sources of epigenetic variation in natural populations. For a given genotype, the epigenetic variation could be environmentally induced or occur randomly. Strategies developed by organisms to face environmental fluctuations such as phenotypic plasticity and diversified bet‐hedging rely, respectively, on these different sources. Random variation can also represent a proxy of developmental stability and can be used to assess how organisms deal with stressful environmental conditions. We then proposed the microbiome as an extension of the epigenotype of the host to assess the factors determining the establishment of the community of microorganisms. Finally, we discussed these perspectives in the applied context of conservation.
The g-loss predicted based on genetic selection is smaller than that observed across various ratio-scale measures of cognitive ability. The difference may result in part from the accumulation of ...deleterious mutations across generations, reducing g via their effects on developmental stability/fitness. Previously published secular trend data on a developmental stability measure, craniofacial fluctuating asymmetry (FA) size, for white US males and females covering 14 and 15 decades respectively, are re-analysed. When the secular increases in FA size are rescaled as declines in latent developmental stability, and multiplied by the validity and reliability adjusted developmental stability-g correlation, g-losses of −.16 points per decade are predicted for the males, females and the combined sample. Predicted fitness losses due to mutation accumulation may account for 30% of the generational decline (−.05 points per decade), indicating only a small role for mutations in secular g-loss. The remaining 70% (−.11 points per decade) may result from developmental stability disrupting environmental change, such as increased exposure to pollutants. Adding these to the g-loss due to selection (re-estimated at −.54 points per decade) yields a combined decadal loss of −.70 points. Additional adjustments for replacement migration and the generation length-g interaction yield a larger magnitude decadal g-loss of −1.25 points.
•Published data on secular trends in craniofacial fluctuating asymmetry are reanalyzed.•Significant linear increases in FA are found for white males and females are found spanning 160years.•This suggests a secular decline in developmental stability.•FA and g are robustly negatively correlated.•Equivalent g-loss for the combined sex sample is −.16 points per decade.
Hybridization is a source of phenotypic novelty and variation because of increased additive genetic variation. Yet, the roles of nonadditive allelic interactions in shaping phenotypic mean and ...variance of hybrids have been underappreciated. Here, we examine the distributions of male-mating traits in F1 hybrids via a meta-analysis of 3208 effect sizes from 39 animal species pairs. Although additivity sets phenotypic distributions of F1s to be intermediate, F1s also showed recessivity and resemblance to maternal species. F1s expressed novel phenotypes (beyond the range of both parents) in 65% of species pairs, often associated with increased phenotypic variability. Overall, however, F1s expressed smaller variation than parents in 51% of traits. Although genetic divergence between parents did not impact phenotypic novelty, it increased phenotypic variability of F1s. By creating novel phenotypes with increased variability, nonadditivity of heterozygotic genome may play key roles in determining mating success of F1s, and their subsequent extinction or speciation.
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•FA in P. ridibundus meristic traits is used to evaluate the environmental health.•The values of FAMI index get higher with the increasing pollution gradient.•FA in P. ridibundus ...meristic traits can be used in bioindication analises.•FA in meristic morphological traits in P. ridibundus is a reliable biomarker.
The aim of this study was to investigate the levels of fluctuating asymmetry in Pelophylax ridibundus populations inhabiting the River of Sazliyka (southern Bulgaria), polluted with domestic sewage and industrial pollution. The study was conducted 5 years after the construction of a modern, wastewater treatment facility near the town of Stara Zagora, whose wastewater is one of the main pollutants of the river. The main objective was to compare the values of the integral indicator for developmental stability (FA) in P. ridibundus with those obtained in a previouis study, conducted before the construction of wastewater treatment facility; and on the basis of that comparison to make an additional independent assessment parallel to the physicochemical analyses. The tested frogs in the present study (25 males and 25 females individuals from each site) were adult and sexually mature. Fluctuating asymmetry was defined according to 10 morphological traits, using the index frequency of asymmetric manifestation of an individual (FAMI). On the basis of the observed average FAMI values the status of the populations (respectively the corresponding biotops) was rated according to a scale from 1 to 5, describing the degree of environmental contamination. Lower values of FAMI were found in the populations of P. ridibundus that inhabit relatively clean sites, whereas higher values of FAMI were found in the sites with anthropogenic pollution. The results of our work give us the opportunity to assume that FA in meristic morphological traits in this species of anurans can be used as a reliable biomarker, an alternative to physicochemical analyses that require expensive laboratory equipment and consumables.
Animal personality can be defined as conspecific individuals consistently differing in behavioral tendencies. Personality is typically identified by behavioral repeatability, which occurs when ...within‐individual variance is low relative to among‐individual variance in the population. Intraspecific comparisons of behavioral repeatability in juveniles and adults within and across years are rare, but would be useful for testing hypotheses related to origins of animal personality and whether individuals exhibit stable or diverging behavior with ontogeny. To examine within‐ and across‐year behavioral repeatability for eastern box turtles (Terrapene carolina), we assessed boldness (movement latency after brief confinement) of captive‐born juveniles twice within three days when eight months old. We then repeated these tests for the same individuals one year later. Juveniles exhibited repeatable boldness within and across years. Although increasing body temperature was slightly associated with decreased movement latency, test year (1 or 2), or housing experience (being raised in an enriched or unenriched condition) had no effects on boldness. We also assessed across‐year repeatability of boldness (head emergence from the shell after brief confinement) for wild adults at 1–3 year intervals. Adults also exhibited repeatable across‐year boldness that was of similar magnitude to juveniles. We found no indication that sex class or whether adults had been radio‐tracked influenced boldness. Our results suggest eastern box turtles demonstrate consistent individuality in boldness from an early age that is largely unaffected by temporal or environmental variation, and these behavioral differences can be maintained for multiple years in captivity and the wild, contrasting with theoretical expectations for personality development. These findings add to recent accumulating evidence demonstrating juvenile and adult box turtles exhibit multiple repeatable behaviors over the short‐ and long‐term. We suggest this species is quickly gaining traction as a model organism for studying the proximate and ultimate causes of personality development within long‐lived animals.
Developmental processes may play a key role in producing animal personality. However, captive juvenile and wild adult box turtles exhibit similar repeatability of behavior, but particular aspects of behavioral variation appear to change over the course of development.
Colour patterns (e.g. irregular, spotted or barred forms) are widespread in the animal kingdom, yet their potential role as signals of quality has been mostly neglected. However, a review of the ...published literature reveals that pattern itself (irrespective of its size or colour intensity) is a promising signal of individual quality across species of many different taxa. We propose at least four main pathways whereby patterns may reliably reflect individual quality: (i) as conventional signals of status, (ii) as indices of developmental homeostasis, (iii) by amplifying cues of somatic integrity and (iv) by amplifying individual investment in maintenance activities. Methodological constraints have traditionally hampered research on the signalling potential of colour patterns. To overcome this, we report a series of tools (e.g. colour adjacency and pattern regularity analyses, Fourier and granularity approaches, fractal geometry, geometric morphometrics) that allow objective quantification of pattern variability. We discuss how information provided by these methods should consider the visual system of the model species and behavioural responses to pattern metrics, in order to allow biologically meaningful conclusions. Finally, we propose future challenges in this research area that will require a multidisciplinary approach, bringing together inputs from genetics, physiology, behavioural ecology and evolutionary-developmental biology.
The idea that symmetry in facial traits is associated with attractiveness because it reliably indicates good physiological health, particularly to potential sexual partners, has generated an ...extensive literature on the evolution of human mate choice. However, large-scale tests of this hypothesis using direct or longitudinal assessments of physiological health are lacking. Here, we investigate relationships between facial fluctuating asymmetry (FA) and detailed individual health histories in a sample (n = 4732) derived from a large longitudinal study (Avon Longitudinal Study of Parents and Children) in South West England. Facial FA was assessed using geometric morphometric analysis of facial landmark configurations derived from three-dimensional facial scans taken at 15 years of age. Facial FA was not associated with longitudinal measures of childhood health. However, there was a very small negative association between facial FA and IQ that remained significant after correcting for a positive allometric relationship between FA and face size. Overall, this study does not support the idea that facial symmetry acts as a reliable cue to physiological health. Consequently, if preferences for facial symmetry do represent an evolved adaptation, then they probably function not to provide marginal fitness benefits by choosing between relatively healthy individuals on the basis of small differences in FA, but rather evolved to motivate avoidance of markers of substantial developmental disturbance and significant pathology.
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