Season of Birth and Sleep-Timing Preferences in Adolescents

The aim of the present study was to explore the relationship between season of birth and sleep-timing preferences in adolescence. To this end, the Morningness-Eveningness Questionnaire for Children and Adolescents (MEQ-CA) was administered to 1912 adolescents (1058 females and 854 males), ranging in age between 10 and 17 yrs. To assess preferred sleep habits, the authors considered the answers to the open-ended questions of the MEQ-CA (items 1 and 2), regarding the preferred arising time and the preferred going to bed time. Combining the answers to these two questions, the authors also indirectly computed the preferred sleep duration and preferred midpoint of sleep. Season of birth did not significantly modulate the overall MEQ-CA score; however, spring-born participants preferred to go to bed and reached the preferred midpoint of sleep later than those born in autumn. Agreeing with a previous study on young adults, the present data point to a significant season-of-birth effect on the two parameters of the sleep-timing preferences in adolescents. (Author correspondence: lorenzo.tonetti2@unibo.it)     

Season of Birth and Lung Fibrosis among Workers Exposed to Asbestos

The season of birth has been suggested to influence the development of some diseases, but its role in lung fibrosis seems to not have been studied previously. The aim of this study was to investigate the relation between the season of birth and fibrotic abnormalities as detected radiologically in high‐resolution computed tomography (HRCT) among workers exposed to asbestos. The HRCT examination was performed on 528 study subjects. Multiple ordinal regression analysis adjusting for covariates was used to study the relations between birth month or season and radiological fibrosis signs. Subjects born in autumn or winter had more extensive fibrotic changes than those born in spring or summer. This applied to all fibrotic changes, apart from subpleural nodules, but only the overall fibrosis score, septal lines, and honeycombing showed statistically significantly higher values in comparison to spring births. The highest scores were detected among those born in autumn and winter months (September–February). These results suggest that there are differences in fibrotic radiological abnormalities according to the season of birth in adults exposed to asbestos. Several hypotheses could explain the observed findings, including the effects of early respiratory infections, cold temperature, and differences in air pollution levels, as well as some metabolic and hormonal effects.     

Further Evidence for the Influence of Photoperiod at Birth on Chronotype in a Sample of German Adolescents

Individuals differ in their circadian preferences (chronotype). There is evidence in the literature to support a season-of-birth effect on chronotype but the evidence is not convincing. In part, the relationship is obscured by a number of methodological differences between studies, including the measures used to define morningness, the way in which the seasons were categorized, and the sample size. This study adds to the literature in several ways. First, we adopt a new approach to categorizing the photoperiod rather than the calendar season; thus we prefer to use the term photoperiod at birth. Second, we used two measures of morningness. Third, we used a large and homogeneous German sample. The results show that adolescents (n?=?2905) born during the increasing photoperiod (Feb–Apr) had a significantly later midpoint of sleep (MSFsc) than those born during the decreasing photoperiod (Aug–Oct). A similar pattern was found for the Composite Scale of Morningness (CSM). Furthermore, both measures of chronotype demonstrated a significant quadratic function over a 1-yr cycle. When looking at each of six consecutive years separately, the Composite Scale of Morningness suggests a cosine rhythm linked to increasing and decreasing photoperiods that becomes weaker in amplitude with increasing age. Despite the strengths in our study, the effect of photoperiod at birth on chronotype remains small. Future studies may require larger sample sizes, may need to explore how neonatal light exposure modulates chronotype, and may need to track how puberty and adolescent lifestyle habits mask the photoperiod effect. (Author correspondence: vollmer@ph-heidelberg.de)     

Role of Patient Chronotype on Circadian Pattern of Myocardial Infarction: A Pilot Study

Population-based studies indicate the risk of acute myocardial infarction (AMI) is greatest in the morning, during the initial hours of diurnal activity. The aim of this pilot study was to determine whether chronotype, i.e., morningness and eveningness, impacts AMI onset time. The sample comprised 63 morning- and 40 evening-type patients who were classified by the Horne-Östberg Morningness-Eveningness Questionnaire (MEQ) in the hospital after experiencing the AMI. The average wake-up and bed times of morning types were ～2?h earlier than evening types. Although the lag in time between waking up from nighttime sleep and AMI onset during the day did not differ between the two chronotypes, the actual clock-hour time of the peak in the 24-h AMI pattern did. The peak in AMI of morning types occurred between 06:01 and 12:00?h and that of the evening types between 12:01 and 18:00?h. Although the results of this small sample pilot study suggest one's chronotype influences the clock time of AMI onset, larger scale studies, which also include assessment of 24-h patterning of events in neither types, must be conducted before concluding the potential influence of chronotype on the timing of AMI onset. (Author correspondence: dryavuzselvi@yahoo.com).     

Associations Between Season of Birth and the Risk of Lung Cancer: Epidemiological Findings From Hungary

Lung cancer is the leading cause of cancer deaths worldwide. Both incidence and mortality of lung cancer are especially high in Hungary. Several investigations suggested recently that month of birth (MOB) is associated with the risks of several nonmalignant disorders as well as some malignant disorders. Only a few studies investigated previously the association between MOB and risk of lung cancer, but they provided inconsistent results. We, therefore, decided to investigate this issue in a large sample of individuals who died from lung cancer. Accordingly, we determined the MOB-associated risk of death by lung cancer between the years 1970 and 2009 among all individuals born in Hungary between 1925 and 1934. The final sample included about two million people. A total of 61,904 deaths by lung cancer occurred in this sample during the period investigated. Using analysis of variance (ANOVA), we did not find significant association between MOB and risk of lung cancer death, either in the whole population investigated (F?=?1.492; p?=?.145) or in the female subpopulation (F?=?1.535; p?=?.129). However, those males born in late spring (May–June) had a lower risk of lung cancer development (F?=?2.577; p?=?.006). Results of the Edwards test also did not suggest consistent association between MOB and risk of lung cancer death in the whole investigated period (1925–1934) in any populations (i.e., whole population or male and female subpopulations). In conclusion, we did not find significant association between MOB and risk of lung cancer in our total sample (although results alluded to a weak association between MOB and risk of lung cancer development among males). The possible associations between MOB and the risk of lung cancer development (or smoking) would require confirmation (or refutation) in large studies from other populations. (Author correspondence: dome_peter@yahoo.co.uk)     

Seasonal Variation in the Orcadian Rhythm of Pulmonary Function in Stable Astthmatic Children who have Nearly Outgrown their Asthma

To study whether nocturnal bronchial obstruction changes during the year, we assessed the circadian FEV₁ variation during four consecutive seasons in 20 children (12 boys; aged 9–12 years) with episodic asthma who were outgrowing their asthma. FEV₁ was determined every 4 h between 10:00 and 10:00 during two consecutive days. The last six FEV₁ values were submitted to cosinor and coefficient of variation (CV) analyses. The seasonal means (SD) in the group 24 h percent predicted FEV₁ was 85.5 (11.4), 81.2 (10.6), 86.0 (11.6), and 82.2 (14.0)% during spring, summer, autumn, and winter, respectively. The difference between the summer and autumn FEV₁ values was statistically significant (p < 0.05). The mean (SD) of the circadian amplitude values was 4.1 (4.3), 6.0 (3.8), 4.9 (3.4), and 7.2 (4.1)% during spring, summer, autumn, and winter, respectively. The difference in amplitude between the spring and winter and between the autumn and winter values was statistically significant (p<0.05). CV values of 48 of the 80 (60%) circadian FEV, time series exceeded the average CV of 5% observed in non-asthmatic children studied in our laboratory. There was an unequal distribution during the year in elevated CV values; 6, 17, 10, and 15 of the high CV values occurred, respectively, in the spring, summer, autumn, and winter. These results suggest that nocturnal bronchial obstruction may change seasonally in terms of severity and amplitude in children who have nearly outgrown their asthma. (Chronobiology International, 13(4), 295–303, 1996)     

Season of birth and lung fibrosis among workers exposed to asbestos

The season of birth has been suggested to influence the development of some diseases, but its role in lung fibrosis seems to not have been studied previously. The aim of this study was to investigate the relation between the season of birth and fibrotic abnormalities as detected radiologically in high-resolution computed tomography (HRCT) among workers exposed to asbestos. The HRCT examination was performed on 528 study subjects. Multiple ordinal regression analysis adjusting for covariates was used to study the relations between birth month or season and radiological fibrosis signs. Subjects born in autumn or winter had more extensive fibrotic changes than those born in spring or summer. This applied to all fibrotic changes, apart from subpleural nodules, but only the overall fibrosis score, septal lines, and honeycombing showed statistically significantly higher values in comparison to spring births. The highest scores were detected among those born in autumn and winter months (September-February). These results suggest that there are differences in fibrotic radiological abnormalities according to the season of birth in adults exposed to asbestos. Several hypotheses could explain the observed findings, including the effects of early respiratory infections, cold temperature, and differences in air pollution levels, as well as some metabolic and hormonal effects.     

SEASON OF BIRTH AND SMOKING: FINDINGS FROM THE NORTHERN FINLAND 1966 BIRTH COHORT

A season of birth effect in addictive disorders has scarcely been studied. As smoking is known to be a highly addictive behavior, we examined whether there exists an association between season of birth and smoking habits among the general population in the Northern Finland 1966 Birth Cohort (NFBC, n?=?8,319). The birth month of each cohort member was categorized into one of the four seasons: spring (March–May), summer (June–August), autumn (September–November), or winter (December–February). Smoking habits of the cohort members were assessed by a postal questionnaire at the age of 31 yrs. Those who reported that they regularly smoked 11 or more cigarettes/day were regarded as heavy smokers. The association between season of birth and smoking was assessed with a logistic regression analysis: first, after controlling for early pregnancy-related and perinatal characteristics (Model 1) and second, after controlling for cohort members' hospital-treated psychiatric disorders, suicide attempts, adult educational level, and marital status (Model 2). Compared to males born in winter, the likelihood for heavy daily smoking was significantly increased, up to 1.3-fold, among males born in the autumn in both logistic regression models. However, among females the likelihood for heavy smoking was statistically significantly elevated among those born during any season other than winter. Season of birth may modify the development of dopaminergic or other neurotransmitter systems divergently among males and females. Altered expression of dopaminergic genes due to environmental climatic factors could explain the association between season of birth and heavy smoking. (Author correspondence: kaisa.riala@oulu.fi).     

Circadian rhythm in plasma aldosterone concentration and its seasonal modulation in the camel (Camelus dromedarius) living in the Algerian Sahara desert

Five male camels dwelling in the Algerian Sahara were studied for circadian rhythmicity in plasma aldosterone concentration and its seasonal modulation. Blood was sampled at a frequency of 1 h or less for a span of 27 h during each season of the year. The mean plasma aldosterone concentration exhibited a significant circadian rhythmicity in every season of the year. Plasma aldosterone concentration was lowest in the morning, increased in the afternoon, and generally highest in the late evening. The peak of the circadian rhythm exhibited seasonal variation; it occurred at 20:04h in October, 16:41h in December, 20:40h in March, and 24:16h in June. The rhythm's 24h mean also exhibited seasonal variability, being significantly higher in March and June compared to October.     

Genetic Aspects of Circadian Dyschronism: Comparison Between Asiatic-Japanese and Caucasian-French Populations

Differences in period (T) length of a variety of arcadian rhythms of a given subject (internal desynchronization or circadian dyschronism) have been demonstrated in shift workers and subjects exposed to natural environmental Zeitgebers. The aims of the present study were to compare the frequency distributions of circadian TS of the oral temperature (OT) rhythm in an Asiatic-Japanese (AJ) population to that of a Caucasian-French (CF) population, as well as to evaluate the possibility that in both populations the observed circadian dyschronism is facilitated by a similar inherited control mechanism. There were 98 healthy adult males in the CF group (including 78 shift workers) and 42 healthy subjects in the AJ group (all shift workers). OT was measured for at least 8 days, four to six times every 24 h. Power spectrum analyses were used to quantify accurately the prominent OT circadian T. In both populations, TS of the sleep-wake rhythm seldom differed from 24 h (four of 42 in the AJ group, none in the CF group), despite irregularities in working hours. In contrast, 30% of OT rhythm TS differed from 24 h in both populations (exhibiting TS of > 24 h or TS of < 24 h). The T distributions exhibited a trimodal (symmetric from both sides) distribution. The trimodal distribution in TS of OT observed in the AJ group did not differ from that observed in the CF group. In both groups the interval of deviation from TS of 24 h predominantly clustered in multiples of +0.8 h and -0.8 h [e.g., 24 h + n(0.8 h), yielding TS of 24.8 h, 25.6 h, etc.]. The observed distribution of TS in AJ and its multiplitive structure were nearly identical to those observed in the CF and were compatible with the Dian-Circadian model suggested for the genetic background of circadian dyschronism of CF.     

Birth in winter can reduce the risk of lung cancer: A retrospective study of the birth season of patients with lung cancer in Beijing area,China

The season of birth is an important risk factor for several diseases. We explored the relationship between birth season and lung cancer. In this population-based retrospective study, we focused on patients with lung cancer who had registered at the Beijing Institute for Cancer Research from 2003 to 2012. In total, 33,025 patients were divided into five subgroups based on their histologic classification, and these five subgroups were compared with the general population (i.e., the permanent resident population of Beijing in 2013). A binary logistic regression method with sex and age as control factors was used to evaluate the relationship between birth season and lung cancer; P < 0.01 was statistically significant. Taking winter as a reference in our analysis of the relationship between season of birth and lung cancer, we found that people who were born in other seasons had a higher probability of developing lung cancer (spring: odds ratio [OR] = 1.06, 95% confidence interval [CI] = 1.03–1.09; summer: OR = 1.07, 95% CI = 1.04–1.10; autumn: OR = 1.06, 95% CI = 1.03–1.09) (P < 0.01). Among the five subgroups, persons with squamous cell carcinoma who were born in summer were more likely to develop lung cancer than those who were born in winter (OR = 1.09, 95% CI = 1.02–1.15, P = 0.006). The other subgroups showed no correlation with season of birth (P > 0.01). This study demonstrates that for people born in winter, the risks of developing lung cancer and squamous cell carcinoma are comparatively lower than those for people born in other seasons. Differences in immune function and the maternal nutrition status during pregnancy of people born in different seasons may explain this finding.     

Vegetation analogs and differences in the Northern and Southern Hemispheres: A global comparison

Biogeographic comparisons help to identify similarities, differences, larger contexts, and useful hypotheses. Between the (extra-tropical) Northern and Southern Hemispheres taxonomy differs almost completely, but other useful bases for vegetation comparison include phenophysiognomy, form composition and vegetation architecture, subphysiognomic morphology, environmental limits of plant types, taxonomic richness, and some aspects of function. All major biome types occur in both hemispheres except the boreal forests and analogous montane coniferous forests of the Northern Hemisphere. Some vegetation and plant types appear clearly unique, including Eucalyptus, campo cerrado, and flat-cushions such as Azorella, all of these in the Southern Hemisphere. Different but parallel adaptations to different but analogous conditions include the tall submediterranean forests, temperate rainforests, and continental versus maritime temperate deserts. Climatic limits appear similar in the two hemispheres, but mechanisms for some differences remain unresolved. Per unit land area, the Southern Hemisphere has higher annual net primary productivity than the Northern. Dissimilar analogs continue to suggest hypotheses and research questions.     

Season of birth and reproductive performance: an analysis of family reconstitutions of 800 women born in The Netherlands at the end of the 19th century

Background: Several studies have reported associations between season of birth and reproductive characteristics such as menarcheal age, fecundability, and twinning, but the results are inconsistent with respect to the location of high- and low-risk seasons. To assess whether this disagreement could be due to the use of populations from different geographic areas and time frames instead of different etiologic pathways, we investigated the season-of-birth dependency of a variety of reproductive outcomes within one time- and arealimited population. Methods: In a historic follow-up study, the reconstituted families of 800 women born between 1873 and 1887 in or near Rotterdam, The Netherlands, were used to determine eight types of reproductive outcome: childlessness, interval to first pregnancy, pregnancy interval, stillbirth, neonatal death, postneonatal death, multiple birth, and gender of offspring. The relation of these outcomes with season of birth was modeled using cosinor functions with periods of 1 year or a half year. Data were analyzed by use of logistic regression or general estimation equations (GEE), dependent on whether outcomes could occur more than once per woman. Results: Peaks in the model-based risks of reproductive failure were found within two small temporal ranges, January 1 to February 11 and July 1 to August 11 for all outcomes except gender. The picture did not change after controlling for known and possible risk factors, including age, offspring's birth cohort, and some social variables. Conclusions: This study reconfirms the idea that seasonal factors around conception or birth influence later reproductive characteristics. Observing the consistency of the location of high-risk seasons across a variety of outcomes, the explanation of season-of-birth dependency of different reproductive outcomes need not involve multiple etiological pathways. (Chronobiology International, 18(3), 525-539, 2001)     

Contrasting diversity patterns of breeding Anatidae in the Northern and Southern Hemispheres

For sustaining ecosystem functions and services, environmental conservation strategies increasingly target to maintain the multiple facets of biodiversity, such as functional diversity (FD) and phylogenetic diversity (PD), not just taxonomic diversity (TD). However, spatial mismatches among these components of biodiversity can impose challenges for conservation decisions. Hence, understanding the drivers of biodiversity is critical. Here, we investigated the global distribution patterns of TD, FD, and PD of breeding Anatidae. Using null models, we clarified the relative importance of mechanisms that influence Anatidae community. We also developed random forest models to evaluate the effects of environmental variables on the Anatidae TD, FD, and PD. Our results showed that geographical variation in Anatidae diversity is hemispheric rather than latitudinal. In the species‐rich Northern Hemisphere (NH), the three diversity indices decreased with latitude within the tropical zone of the NH, but increased in the temperate zone reaching a peak at 44.5–70.0°N, where functional and phylogenetic clustering was a predominant feature. In the Southern Hemisphere (SH), Anatidae diversity increased poleward and a tendency to overdispersion was common. In NH, productivity seasonality and temperature in the coldest quarter were the most important variables. Productivity seasonality was also the most influential predictor of SH Anatidae diversity, along with peak productivity. These findings suggested that seasonality and productivity, both consistent with the energy‐diversity hypothesis, interact with the varying histories to shape the contrasting hemispheric patterns of Anatidae diversity. Phylogenetic diversity (PD) and FD underdispersion, widespread across the species‐rich, seasonally productive mid‐to‐high latitudes of the NH, reflects a rapid evolutionary radiation and resorting associated with Pleistocene cycles of glaciation. The SH continents (and southern Asia) are characterized by a widespread tendency toward PD and FD overdispersion, with their generally species‐poor communities comprising proportionately more older lineages in thermally more stable but less predictably productive environments.     

Association between moringness-eveningness preference and mental/physical premenstrual symptoms in Japanese females 12 to 31 years of age

This study investigates the relationship between circadian typology, i.e., morningness-eveningness (M-E) preference, and the occurrence and severity of premenstrual mental and physical symptoms among 154 young Japanese female university students (range, 18 to 31 yrs; mean±S.D., 20.69±3.69 yrs) and 417 junior high school students (range, 12 to 15 yrs; mean±S.D., 14.29±0.67 yrs) living in an urban or suburban area of Kochi prefecture. Female university students experienced melancholy mood more frequently than did males, and the female university students who frequently became melancholy were more evening-typed than those who did not experience melancholy. Female university students who experienced frequent fluctuations in mood and/or menstrual pain were more evening-typed than those who were not so affected. M-E preference of junior high school students was not correlated with stability of mood or frequency of menstrual pain. In urban areas, however junior high school students who had very stable menstrual cycles were significantly more morning-typed than those whose menstrual cycles were not stable. In suburban areas, the bedtimes of female junior high students who had stable menstrual cycles were significantly earlier than those whose menstrual cycle duration was not stable. A physiological relationship between the circadian system, M-E, and attributes of the menstrual cycle seems to be present in adolescent female Japanese junior high school students.     

Influence of Chronotype,Season, and Sex of Subject on Sleep Behavior of Young Adults

The aim of this study was to investigate whether sex, season, and/or chronotype influence the sleep behavior of university students. Detailed data were collected on activity/rest patterns by wrist actigraphy combined with diaries. Thirty‐four medical students (19 female and 15 male) were monitored by Actiwatch® actometers for 15 consecutive days in May and again in November. The data of a modified Horne and Östberg chronotype questionnaire, which were collected from 1573 female and 1124 male medical school students surveyed in the spring and autumn over an eight‐year period, were evaluated. Actiwatch® sleep analysis software was used to process the activity data with statistical analyses performed with ANOVA. We found no significant sex‐specific differences in sleep efficiency, sleep onset latency, or actual sleep‐time duration. However, we did find a difference in sleep efficiency between morning and evening types, with morning types having a higher sleep efficiency (87.9%, SD=1.3) than evening types (84.3%, SD=0.87%; p=0.007). Seasonal differences were also detected: the actual sleep‐time duration in autumn was significantly longer (mean 6.9 h, SD=0.13 h) than in spring (6.6 h, SD=0.1 h; p=0.013). Evaluation of the chronotype questionnaire data showed that individuals with no special preference for morningness or eveningness (i.e., so‐called intermediates) were most common. The distribution of chronotypes was related to the sex of subject. Men displayed eveningness significantly more often than women (28.9% males vs. 20.8% females; p<0.001), while females exhibited greater morningness (20.3% females vs.15.6% males; p<0.001). Sex influences chronotype distribution, but not actual sleep time‐duration, sleep onset latency, or sleep efficiency. The latter, however, differed among chronotypes, while actual sleep‐time duration was affected by season.     

Relationship Between Infant and Mother Circadian Rest-Activity Rhythm Pre- and Postpartum,in Comparison to an Infant With Free-Running Rhythm

Some infants show a free-running rhythm in their rest-activity. We do not know why, nor do we know exactly what the entrainment factors are for the development of the normal 24-h rest-activity rhythm. Actigraphic recordings on 10 primiparae during late pregnancy and these mothers and their infants during the 2nd, 6th, and 12th wks after birth were made over 3–5 continuous days to investigate maternal and infant entrainment. One infant showed a free-running rest-activity circadian rhythm. In late pregnancy, the period in the autocorrelogram of the mother with the free-running infant was longer than the significant period of the mean autocorrelogram of the mothers with non-free-running infants. The finding of this study indicates the free-running rhythm of infant is not reset by maternal entrainment factors. (Author correspondence: nishihara-kk@igakuken.or.jp)     

Comparison of the circadian eclosion rhythm between non-diapause and diapause pupae in the onion fly,Delia antiqua: the effect of thermoperiod

When non-diapause and diapause pupae of Deliaantiqua were exposed to various thermoperiods where thermophase (T) was 25 °C and the cryophase (C) was 15 or 20 °C (TC₁₅ or TC₂₀) in constant darkness (DD), the majority of both types of flies emerged before the rise in temperature. Eclosion time was delayed at the lower cryophase temperature. Moreover, there was a significant difference in the time of adult eclosion between non-diapause and diapause pupae; diapause pupae eclosed earlier than non-diapause pupae. When the two types of pupae were transferred to a constant low temperature (15 or 20 °C) after having experienced TC₁₅ or TC₂₀ 12:12 h, they showed circadian rhythmicity in eclosion. The free-running period (τ) of the eclosion rhythm changed after transfer to constant low temperatures in both non-diapause and diapause pupae, suggesting that this change represents a transient cycle until the temperature-sensitive oscillator is coupled again to the temperature-insensitive pacemaker. However, diapause pupae tended to show a shorter τ than non-diapause pupae. This observation suggests that the difference in adult eclosion time under thermoperiodic conditions between non-diapause and diapause pupae is related to their different τ s.     

Phylogeny of the leafy liverwort Ptilidium: cryptic speciation and shared haplotypes between the Northern and Southern Hemispheres

The small, phylogenetically isolated liverwort genus Ptilidium has been regarded as of cool-Gondwanic origin with the bipolar, terrestrial Ptilidium ciliare giving rise to the Northern Hemisphere epiphytes Ptilidium pulcherrimum and Ptilidium californicum. This hypothesis is examined using a dataset including three chloroplast DNA regions from 134 Ptilidium accessions and one accession each of its closest relatives Trichocoleopsis and Neotrichocolea. Maximum likelihood and parsimony analyses point to a close relationship between P. ciliare and P. pulcherrimum, whereas P. californicum is placed sister to the remainder of the genus, separated by a long branch. Haplotype analysis and our phylogeny indicate the presence of Southern Hemisphere haplotypes of P. ciliare in the Northern Hemisphere, and shared haplotypes of P. ciliare and P. pulcherrimum between Europe and North America. Based on our findings, we reject the Gondwana-scenario and propose recent long distance dispersal as an explanation for the bipolar disjunct range. Ptilidium ciliare is resolved as paraphyletic with P. pulcherrimum nested within it. An isolated Ptilidium lineage with the morphology of P. ciliare from the Himalaya region likely represents a hitherto unrecognized cryptic species. Ptilidium pulcherrimum splits into a Japanese clade and a clade with accessions from Europe and North America.