Evolutionary trade-offs in dormancy phenology.

Seasonal animal dormancy is widely interpreted as a physiological response for surviving energetic challenges during the harshest times of the year (the physiological constraint hypothesis). However, there are other mutually non-exclusive hypotheses to explain the timing of animal dormancy, that is, entry into and emergence from hibernation (i.e. dormancy phenology). Survival advantages of dormancy that have been proposed are reduced risks of predation and competition (the 'life-history' hypothesis), but comparative tests across animal species are few. Using the phylogenetic comparative method applied to more than 20 hibernating mammalian species, we found support for both hypotheses as explanations for the phenology of dormancy. In accordance with the life-history hypotheses, sex differences in hibernation emergence and immergence were favored by the sex difference in reproductive effort. In addition, physiological constraint may influence the trade-off between survival and reproduction such that low temperatures and precipitation, as well as smaller body mass, influence sex differences in phenology. We also compiled initial evidence that ectotherm dormancy may be (1) less temperature dependent than previously thought and (2) associated with trade-offs consistent with the life-history hypothesis. Thus, dormancy during non-life-threatening periods that are unfavorable for reproduction may be more widespread than previously thought.

Reproductive Biology of Trichopria anastrephae (Hymenoptera: Diapriidae), a Biological Control Agent of Drosophila suzukii (Matsumura) (Diptera: Drosophilidae).

Hymenopteran parasitoids, like any other insect, employ strategies to ensure their reproduction. Understanding these strategies is important for ecological purposes, but also to improve mass rearing of biological control agents. Here, we describe mating strategies used by the pupal parasitoid Trichopria anastrephae Lima (Hymenoptera: Diapriidae), a potential biocontrol agent, that has been considered for augmentative releases for management of the invasive pest species Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). We studied the emergence pattern of males and females of T. anastrephae and the effects of parental ae on offspring number and sex ratio. Polygamy was also studied and its effects on parasitism and offspring production were described. Adults from this species emerge in the first hours of photophase, and males emerge before females, demonstrating that T. anastrephae is a protandrous species. Parasitoid age when first mated influences the parasitism and sex ratio. Younger females result in a higher number of offspring (8.16 parasitoids/day), while older males result in a more female-biased sex ratio of offspring (64% females). Both males and females are polygamic, and the order in which a female is mated by the male affects parasitism, viability of parasitized pupae, and sex ratio of offspring, with the first female performing the highest parasitism and sex ratio (63.83 and 61% of females, respectively), but the lowest viability (92.92%). Females that are allowed to mate multiple times generate lower numbers of offspring (113.05 parasitoids) when compared to virgin or single-mated females (135.20 and 130.70 parasitoids, respectively), but the highest sex ratio (49% of females). Data present in this study and how it can be used to improve parasitoid rearing and field releases of T. anastrephae, in biological control programs for D. suzukii are discussed.

Sexes in sync: phenotypic plasticity, sexual selection and phenological synchrony between the sexes in a wild hibernator.

Desynchrony of phenological responses to climate change is a major concern for ecological communities. Potential uncoupling between one of the most fundamental divisions within populations, males and females, has not been well studied. To address this gap, we examined sex-specific plasticity in hibernation phenology in two populations of Columbian ground squirrels (Urocitellus columbianus). We find that both sexes display similar phenological plasticity to spring snowmelt dates in their timing of torpor termination and behavioural emergence from hibernation. As a result of this plasticity, the degree of protandry (i.e. males' emergences from hibernation preceding those of females) did not change significantly over the 27-year study. Earlier male behavioural emergence, relative to females, improved the likelihood of securing a breeding territory and increased annual reproductive success. Sexual selection favouring earlier male emergence from hibernation may maintain protandry in this population, but did not contribute to further advances in male phenology. Together, our results provide evidence that the sexes should remain synchronized, at least in response to the weather variation investigated here, and further support the role of sexual selection in the evolution of protandry in sexually reproducing organisms.

Dark-centred umbels in Apiaceae: diversity, development and evolution.

The wild carrot (Daucus carota) is famous for its dark flowers in the umbel centre. Several studies have been conducted to figure out their functional significance, but the evolution of the dark centre remains an enigma. In the present paper, we consider all known apioid species with dark-centred umbels to get a deeper understanding of their biology and evolution. Based on herbaria studies, literature and field work, we reconstructed the distribution area of 10 species (7 genera, 6 clades) of Apiaceae-Apioideae. To recognize homology of the dark structures, developmental studies were conducted in Artedia squamata and Echiophora trichophylla Field studies included architecture, flower morph distribution (andromonoecy) and flowering sequence within the plants, abundancy and behaviour of umbel visitors and preliminary manipulation experiments (removal/adding of dark structures). The dark structures are not homologous to each other. In the Daucus alliance, central flowers or umbellets are conspicuous, whereas in other species dark brush-like (A. squamata) or club-shaped structures (Dicyclophora persica, Echinophora trichophylla, Tordylium aegyptiacum, T. cappadocicum) develop from a naked receptacle. Species are andromonoecious, have a modular architecture and flower in multicyclic protandrous sequence. Among the many umbel visitors, beetles were the most abundant group. Only visitors found on umbels in both flowering phases were recognized as possible pollinators. Manipulation experiments indicated that the dark structures influence the behaviour of some, but not all umbel visitors. In Echinophora trichophylla, a massive gall infection was observed. It is evident that the dark structures evolved several times in parallel. The brush- and club-shaped structures are interpreted as the results of mutations affecting umbel development. Dark umbel centres are most likely stabilized by selection due to their general adaptive function. Their appearance in an area known as a hotspot of beetle pollination gives rise to the assumption that they may act as beetle marks.

Sexual antagonism in sequential hermaphrodites.

Females and males may have distinct phenotypic optima, but share essentially the same complement of genes, potentially leading to trade-offs between attaining high fitness through female versus male reproductive success. Such sexual antagonism may be particularly acute in hermaphrodites, where both reproductive strategies are housed within a single individual. While previous models have focused on simultaneous hermaphroditism, we lack theory for how sexual antagonism may play out under sequential hermaphroditism, which has the additional complexities of age-structure. Here, we develop a formal theory of sexual antagonism in sequential hermaphrodites. First, we construct a general theoretical overview of the problem, then consider different types of sexually antagonistic and life-history trade-offs, under different modes of genetic inheritance (autosomal or cytoplasmic), and different forms of sequential hermaphroditism (protogynous, protoandrous or bidirectional). Finally, we provide a concrete illustration of these general patterns by developing a two-stage two-sex model, which yields conditions for both invasion of sexually antagonistic alleles and maintenance of sexually antagonistic polymorphisms.

Reproductive Biology and Breeding Systems of Two Opisthopappus Endemic and Endangered Species on the Taihang Mountains.

Opisthopappus is a perennial, endemic herb of the Taihang Mountains in China. Two species of this genus (O. longilobus and O. taihangensis) are important wild genetic resources for Asteraceae; however, their reproductive biology has been lacking until now. This study is the first detailed report on the reproductive biology and breeding systems of two Opisthopappus species. Through field observations, the floral syndromes of O. longilobus and O. taihangensis were found to possess a similar pattern, although O. taihangensis has a relatively larger capitulum, more ray ligules, and disc florets. The flowers of both O. longilobus and O. taihangensis are protandrous, a character that can prevent autogamy at the single-flower level, and insects are required for pollination. Further, brightly ligules, brightly bisexual florets, unique fragrance, and amount of nectar suggest that these species propagate via an entomophilous pollination system. Hymenopteran and Diptera species were observed as the effective pollinators for these two species. The outcrossing index, pollen/ovule ratio and the results of hand pollination indicated that these Opisthopappus species might have a mixed mating system that combines cross-fertilization and partial self-fertilization for O. longilobus and O. taihangensis, outcrossing predominated in the breeding system, while self-pollination played an important role in seed production when insect pollination was unavailable, particularly in a harsh environment, such as the Taihang Mountains cliffs. Meanwhile, O. taihangensis might better adapt to severe surroundings with relatively complex floral syndromes, specifically through the attraction of visiting insects and a high seed set rate. The above results not only provide reference information toward a better understanding of the survival strategies of O. longilobus and O. taihangensis in the Taihang Mountains but also lay a solid foundation for further exploring the molecular mechanisms that underly their adaptation under cliff environments.

Sexual conflict over phenological traits: selection for protandry can lock populations into temporally mismatched reproduction.

In seasonal environments, competition among males can drive males to emerge before females. Females, simultaneously, should avoid emerging at times after sufficient male availability. We show that the consequent sexual conflict over timing traits can produce arms races toward ever earlier emergence, if low mate-search efficiency or sperm limitation elevate the latter risk for females. In reality, however, arms races over timing cannot proceed indefinitely as this ignores the relevant ecological context for phenology: the temporal niche of resource availability for offspring development. We model the interaction of natural and sexual selection to predict the sexual conflict load, i.e., the loss of population fitness caused by sexual conflict. We show that selection to avoid matelessness can exacerbate another problem of maladaptation: a temporal mismatch between the organism (e.g., insect) and its resource (e.g., host plant). Load frequently associates with protandry if males can mate multiply, yet lack of multiple mating does not imply zero load. A temporal mismatch can still evolve, where both sexes emerge and mate suboptimally early with respect to the seasonal resource peak, because monogamy does not guarantee that every individual finds one mate, and selection favors early individuals in mate-finding contexts.

Adult male birds advance spring migratory phenology faster than females and juveniles across North America.

Advances in spring migratory phenology comprise some of the most well-documented evidence for the impacts of climate change on birds. Nevertheless, surprisingly little research has investigated whether birds are shifting their migratory phenology equally across sex and age classes-a question critical to understanding the potential for trophic mismatch. We used 60 years of bird banding data across North America-comprising over 4 million captures in total-to investigate both spring and fall migratory phenology for a total of 98 bird species across sex and age classes, with the exact numbers of species for each analysis depending on season-specific data availability. Consistent with protandry, in spring (n = 89 species), adult males were the first to arrive and immature females were the last to arrive. In fall (n = 98), there was little difference between sexes, but adults tended to depart earlier than juveniles. Over 60 years, adult males advanced their phenology the fastest (-0.84 days per decade, 95 CrI = -1.22 to -0.47, n = 36), while adult and immature females advanced at a slower pace, causing the gap in male and female arrival times to widen over time. In the fall, there was no overall trend in phenology by age or sex (n = 57), driven in part by high interspecific variation related to breeding and molt strategies. Our results indicate consistent and predictable age- and sex-based differences in the rates at which species' springtime phenology is shifting. The growing gap between male and female migratory arrival indicates sex-based plasticity in adaptation to climate change that has strong potential to negatively impact current and future population trends.

Nesting Biology of the Potter Wasp Ancistrocerus flavomarginatus (Hymenoptera, Vespidae, Eumeninae) Revealed by Trap-Nest Experiments in Southern Brazil.

This paper provides the first description of the nesting biology of Ancistrocerus flavomarginatus (Brèthes) (Hymenoptera, Vespidae, Eumeninae), the only species of the genus found in Brazil. Our trap-nest experiments were conducted in two Mixed Ombrophilous Forest fragments and two adjacent matrices in Guarapuava (Paraná state, Brazil) from August 2017 to July 2018. In each area, we set 192 trap nests divided into six groups of 32 units, totalling 768 trap nests. We obtained a total of 47 nests of A. flavomarginatus, the vast majority of them (43, 91.5%) founded in the forest fragments. Most nests were built in wooden traps with a bore diameter of either 5 or 7 mm (19 nests in each type, 80.8%). Nests comprised 1-12 subcylindrical brood cells arranged linearly and separated from one another by transverse partitions of soil mastic. Larvae consumed 6-10 lepidopteran caterpillars before spinning the cocoon. Ancistrocerus flavomarginatus produced up to 6 annual generations (multivoltinism) and its immature forms were parasitized by chrysidid and ichneumonid wasps. The calculated sex ratio (1.78:1) was statistically biased towards males, but since they (21.3 ± 2.0 mg) were significantly lighter than females (50.9 ± 4.0 mg), the resulting investment ratio (1.34:1) was female biased. Males emerged from more external cells and developed significantly faster (27.2 ± 0.46 days) than females (30.1 ± 0.66 days), hence a case of protandry. We demonstrated that A. flavomarginatus is largely dependent on the Atlantic Rainforest and thus that deforestation poses a critical threat to this important species.

Proporción sexual y hermafroditismo del molusco, Anadara tuberculosa (Bivalvia: Arcidae) en Panamá / Sexual proportion and hermaphroditism of the mollusc, Anadara tuberculosa (Bivalvia: Arcidae) in Panama

Introducción: El bivalvo Anadara tuberculosa es un recurso pesquero y económico importante en el Pacífico Este Tropical. La proporción sexual varia a lo largo de su área de distribución, con casos de aparición de hermafroditismo, ocasional para algunas poblaciones, normal en otras. Estas características podrían ser una respuesta a presiones antropogénicas y ambientales. Objetivo: Evaluar la proporción sexual y el hermafroditismo en la especie en el Pacífico de Panamá. Métodos: Se analizó información reproductiva de A. tuberculosa generada entre 1994 y 2020 para el Golfo de Montijo, así como datos de 2017 para el manglar de David. Se aplicaron procedimientos macroscópicos, contrastados con histológicos y se generó un factor de corrección para ajustar la proporción sexual macroscópica, debido al efecto, sobre la proporción sexual, que ocasiona los organismos indeterminados. Resultados: Para el Golfo de Montijo, la histología indicó una proporción sexual hembra a macho de 1:1 hasta 3.2:1, entre 1994 y 2017, mientras que la macroscopía varió de 1.9:1 a 5.1:1 entre 2004 y 2020. Para el manglar de David, la histología indicó una proporción sexual de 3.7:1, y de 7.9:1 por macroscopía en el 2017. En ambas localidades, especímenes más grandes mostraron mayor variación en la proporción sexual, pese a la técnica implementada, así como hermafroditismo protándrico no casual en el 2017. Conclusiones: La aparición del hermafroditismo protándrico y los cambios en la proporción sexual indican que la población de A. tuberculosa, en ambas localidades, está respondiendo a presiones antropogénicas y ambientales.

Introduction: The bivalve Anadara tuberculosa is an important fishery in the Eastern Tropical Pacific. The sex ratio varies along its geographic range and there are cases of hermaphroditism, occasional in some populations, normal in others. These characteristics may be a response to anthropogenic and environmental pressure. Objective: To evaluate sex ratio and hermaphroditism of the species in the Panamanian Pacific. Methods: Data on reproductive features of A. tuberculosa generated between 1994 and 2020 for Gulf of Montijo, as well as 2017 data from mangroves of David was analyzed. Macroscopic diagnosis of individual sex is sensitive to the problem of indeterminate individuals, which in turn can skew the sex ratio analysis; therefore, the macroscopic method was compared with histological sections to generate a correction factor to adjust the macroscopically determined sex ratio. Results: For Montijo, histology indicated that the female to male sex ratio ranged from 1:1 to 3.2:1 between 1994 and 2017, while macroscopy indicated 1.9:1 to 5.1:1 between 2004 and 2020. For David, histology indicated a ratio of 3.7:1, and macroscopy 7.9:1. At both localities, larger specimens had more sex ratio variation, independently of the technique, and there was non-casual protandric hermaphroditism in 2017. Conclusion: The occurrence of protandric hermaphroditism and sex ratio changes suggest anthropogenic and environmental pressure in all populations.

Transcriptome Profiling and Expression Localization of Key Sex-Related Genes in a Socially-Controlled Hermaphroditic Clownfish, Amphiprion clarkii.

Clownfish can be an excellent research model for investigating the socially-controlled sexual development of sequential hermaphrodite teleosts. However, the molecular cascades underlying the social cues that orchestrate the sexual development process remain poorly understood. Here, we performed a comparative transcriptomic analysis of gonads from females, males, and nonbreeders of Amphiprion clarkii, which constitute a complete social group, allowing us to investigate the molecular regulatory network under social control. Our analysis highlighted that the gonads of nonbreeders and males exhibited high similarities but were far from females, both in global transcriptomic profiles and histological characteristics, and identified numerous candidate genes involved in sexual development, some well-known and some novel. Significant upregulation of cyp19a1a, foxl2, nr5a1a, wnt4a, hsd3b7, and pgr in females provides strong evidence for the importance of steroidogenesis in ovarian development and maintenance, with cyp19a1a playing a central role. Amh and sox8 are two potential key factors that may regulate testicular tissue development in early and late stages, respectively, as they are expressed at higher levels in males than in females, but with slightly different expression timings. Unlike previous descriptions in other fishes, the unique expression pattern of dmrt1 in A. clarkii implied its potential function in both male and female gonads, and we speculated that it might play promoting roles in the early development of both testicular and ovarian tissues.

Increase in protandry over time in a long-distance migratory bird.

Protandry is a widespread life-history phenomenon describing how males precede females at the site or state of reproduction. In migratory birds, protandry has an important influence on individual fitness, the migratory syndrome, and phenological response to climate change. Despite its significance, accurate analyses on the dynamics of protandry using data sets collected at the breeding site, are lacking. Basing our study on records collected during two time periods, 1979 to 1988 and 2006 to 2016, we aim to investigate protandry dynamics over 38 years in a breeding population of willow warblers (Phylloscopus trochilus). Change in the timing of arrival was analyzed in males and females, and protandry (number of days between male and female arrival) was investigated both at population level and within breeding pairs. Our results show advancement in the arrival time at the breeding site in both sexes, but male arrival has advanced to a greater extent, leading to an increase in protandry both at the population level and within breeding pairs. We did not observe any change in sex ratio that could explain the protandry increase, but pronounced temperature change has occurred and been reported in the breeding area and along the migratory route. Typically, natural selection opposes too early arrival in males, but given warmer springs, this counteracting force may be relaxing, enabling an increase in protandry. We discuss whether our results suggest that climate change has induced sex-specific effects, if these could be evolutionary and whether the timing of important life-history stages such as arrival at the breeding site may change at different rates in males and females following environmental shifts.

Mating and fitness consequences of variation in male allocation in a wind-pollinated plant.

In hermaphrodites, the allocation of resources to each sex function can influence fitness through mating success. A prediction that arises from sex allocation theory is that in wind-pollinated plants, male fitness should increase linearly with investment of resources into male function but there have been few empirical tests of this prediction. In a field experiment, we experimentally manipulated allocation to male function in Ambrosia artemisiifolia (common ragweed) and measured mating success in contrasting phenotypes using genetic markers. We investigated the effects of morphological traits and flowering phenology on male siring success, and on the diversity of mates. Our results provide evidence for a linear relation between allocation to male function, mating, and fitness. We find earlier onset of male flowering time increases reproductive success, whereas later flowering increases the probability of mating with diverse individuals. Our study is among the first empirical tests of the prediction of linear male fitness returns in wind-pollinated plants and emphasizes the importance of a large investment into male function by wind-pollinated plants and mating consequences of temporal variation in sex allocation.

Morphological, anatomical, ultrastructural, and histochemical study of flowers and nectaries of Iris sibirica L.

The insufficient pollinator visitation is the most important limitation of fruit and seed production, which is common and ubiquitous in entomophilous angiosperms. The scent and attractive colours with flower guides and such floral rewards as nectar, pollen, and oil are important attractants for insects visiting and pollinating flowers in the family Iridaceae. The aim of this study was to investigate the morphology of flowers and the micromorphology, anatomy, and ultrastructure of floral nectaries in the rare and endangered species Iris sibirica with the use of light, scanning, and transmission electron microscopes and histochemical assays. Osmophores in the form of papillae were located on the adaxial surface of outer tepals and on the abaxial surface of the stylodium channel. The nectaries were located on the inner surface of the perianth tube and were composed of a single-layered epidermis with papillae and several layers of glandular parenchyma with vascular bundles. I. sibirica nectaries represent the presecretory starch-accumulating type, where nectar is released for a short time immediately after flower opening. Nectar was produced throughout the flower lifespan in both male and female stages. It was secreted in the granulocrine mode and released through microchannels in the reticulate cuticle of nectary papillae. Transport of pre-nectar components proceeded via symplastic and apoplastic pathways. The nectary epidermal cells with papillae and glandular parenchyma cells contained total lipids, acidic lipids, and polysaccharides, whereas the epidermal cells with papillae additionally contained neutral lipids and polyphenol compounds. The nectaries and nectar production in I. sibirica flowers share the common location and follow several secretion patterns characteristic for the nectaries in some members of the family Iridaceae and the subfamily Iridoideae. Nevertheless, the mode of nectar release through the cuticle of epidermal papillae has been described in Iridaceae family for the first time. The visual, aromatic, and food attractants characteristic of I. sibirica flowers probably stimulate potential visits by pollinators, but the short nectar secretion period may limit the effectiveness of pollinators and sexual reproductive success.

Reproductive Biology of Rheum webbianum Royle, a Vulnerable Medicinal Herb From Alpines of North-Western Himalaya.

Information on reproductive biology and pollination ecology studies of threatened plants are essential to develop strategies for their sustainable utilization and effective conservation. As such, these studies were conducted on Rheum webbianum, a high-value "vulnerable" medicinal herb of the north-western Himalaya. This species presents a unique mode of reproductive behavior through the involvement of different floral events, including the movement of reproductive organs. The plants survive extremely cold conditions through underground perennating rhizomes that sprout into juvenile shoots with the onset of the favorable climatic conditions. The peduncle arises from the axils of the radical leaves, bearing a globular collection of densely arranged hermaphrodite flowers with temporally separated male and female phases; the male phase precedes the female phase (protandry). Anther dehiscence and stigma receptivity is post-anthesis. Anthers dehisce longitudinally along margins, liberating a large mass of spherical and tricolpate pollen with spinulose exine. Pollen viability decreased to < 10% on day 9. Pistil is tristylous, with each style terminating into a fan-shaped stigma lobe. The pollen receptive surface of each stigmatic lobe remains incurved at an angle of 360° and shows upward movement after anthesis, forming a funnel-like structure at an angle of 180° with respect to the ovary. Pollination syndrome is ambophilous. Spontaneous autogamy or geitonogamy to a certain extent is achieved in this species due to the arrangement of flowers in the inflorescence and overlapping of male and female reproductive phases among them. Incurved stigmatic lobes and outward movement of stamens too facilitate outcrossing. Pollen/ovule ratio estimates, results of pollination experiments on breeding behavior, outcrossing, and self-compatibility indices demonstrated that plants are self-compatible and cross-fertile.

Changes in female function and autonomous selfing across floral lifespan interact to drive variation in the cost of selfing.

PREMISE: Morphological and developmental changes as flowers age can impact patterns of mating. At the same time, direct or indirect costs of floral longevity can alter their fitness outcomes. This influence has been less appreciated, particularly with respect to the timing of selfing. We investigated changes in stigma events, autonomous selfing, outcross seed set capacity, and autofertility-a measure representing the potential for reproductive assurance-across floral lifespan in the mixed-mating biennial Sabatia angularis. METHODS: We examined stigma morphology and receptivity, autonomous self-pollen deposition, and seed number and size under autonomous self-pollination and hand outcross-pollination for flowers of different ages, from 1 d of female phase until 14 d. We compared autonomous seed production to maximal outcross seed production at each flower age to calculate an index of autofertility. RESULTS: The stigmatic lobes begin to untwist 1 d post anthesis. They progressively open, sextend, coil, and increase in receptivity, peaking or saturating at 8-11 d, depending on the measure. Autonomous seed production can occur early, but on average remains low until 6 d, when it doubles. In contrast, outcross seed number and size start out high, then decline precipitously. Consequently, autofertility increases steeply across floral lifespan. CONCLUSIONS: Changes in stigma morphology and receptivity, timing of autonomous self-pollen deposition, and floral senescence can interact to influence the relative benefit of autonomous selfing across floral lifespan. Our work highlights the interplay between evolution of floral longevity and the mating system, with implications for the maintenance of mixed mating in S. angularis.

Studies on Reproductive Development and Breeding Habit of the Commercially Important Bamboo Bambusa tulda Roxb.

Compared to other grasses, flowering in bamboo is quite divergent, yet complex with respect to time to flower, number of individual culms in a population that have been induced at a time (sporadic vs. gregarious), nature of monocarpy, morphology of inflorescences (solitary spikelet vs. pseudospikelet), biology of pollen and nature of genetic compatibility. Wide diversity exists even across species and genotypes. However, due to the rarity of flowering and inaccessibility, few studies have been done to systematically analyse diverse aspects of the reproductive behaviour of bamboo. In this study, four recurrently occurring, sporadic flowering populations of Bambusa tulda have been closely observed over the last seven years. Detailed inflorescence and floral morphology and development of reproductive organs have been studied. Pollen viability was assessed by staining and in vitro germination. Self and cross pollination experiments were performed in a plantation site to assess the genetic nature of pollen-pistil interaction. The study identifies interesting reproductive features, that are not common in other grasses. A few important observations include the early appearance of a solitary spikelet vs. late appearance of a pseudospikelet in the flowering cycle, low rate of pollen germination, protandry, self-incompatibility and higher rate of seed setting by the pseudospikelet as compared to the solitary spikelet. The findings will not only be useful to understand the reproductive behaviour of this non-woody timber plant, but will also be useful for forest management and sustainable use of bamboo bioresources.

Coping with Environmental Extremes: Population Ecology and Behavioural Adaptation of Erebia pronoe, an Alpine Butterfly Species.

A mark-recapture study of the nominotypical Erebia pronoe in the Alps was conducted to survey its ecological demands and characteristics. Population structure analysis revealed a combination of protandry (one-week earlier eclosion of males) and serial eclosion. Significant differences between both sexes were found in population density (males: 580/ha ± 37 SE; females: 241/ha ± 66 SE), sex-ratio (2.4) and behaviour (57.7 vs. 11.9% flying). Both sexes used a wide range of nectar plants (Asteraceae, 77.3%; Dipsacaceae, 12.3%; Gentianaceae, 9.7%). The use of nectar plants shows a non-specific spectrum, which, however, completely avoids overlap with the locally co-occurring species Erebia nivalis. Movement patterns show the establishment of homeranges, which significantly limits the migration potential. Due to its broad ecological niche, E. pronoe will probably be able to react plastically to the consequences of climate change. The formation of high population densities, the unconcerned endangerment status, the unspecific resource spectrum and the sedentary character of the species make E. pronoe a potential indicator of the quality and general resource occurrence of alpine rupicolous grasslands.

Why do males emerge before females? Sexual size dimorphism drives sexual bimaturism in insects.

Conspecific females and males often follow different development trajectories which leads to sex differences in age at maturity (sexual bimaturism, SBM). Whether SBM is typically selected for per se (direct selection hypothesis) or merely represents a side-effect of other sex-related adaptations (indirect selection hypothesis) is, however, still an open question. Substantial interspecific variation in the direction and degree of SBM, both in invertebrates and vertebrates, calls for multi-species studies to understand the relative importance of its evolutionary drivers. Here we use two complementary approaches to evaluate the evolutionary basis of SBM in insects. For this purpose, we assembled an extensive literature-derived data set of sex-specific development times and body sizes for a taxonomically and ecologically wide range of species. We use these data in a meta-analytic framework to evaluate support for the direct and indirect selection hypotheses. Our results confirm that protandry - males emerging as adults before females - is the prevailing form of SBM in insects. Nevertheless, protandry is not as ubiquitous as often presumed: females emerged before males (= protogyny) in about 36% of the 192 species for which we had data. Moreover, in a considerable proportion of species, the sex difference in the timing of adult emergence was negligible. In search for the evolutionary basis of SBM, we found stronger support for the hypothesis that explains SBM by indirect selection. First, across species, the direction and degree of SBM appeared to be positively associated with the direction and degree of sexual size dimorphism (SSD). This is consistent with the view that SBM is a correlative by-product of evolution towards sexually dimorphic body sizes. Second, within protandrous species, the degree of protandry typically increased with plastic increase in development time, with females prolonging their development more than males in unfavourable conditions. This pattern is in conflict with the direct selection hypothesis, which predicts the degree of protandry to be insensitive to the quality of the juvenile environment. These converging lines of evidence support the idea that, in insects, SBM is generally a by-product of SSD rather than a result of selection on the two sexes to mature at different times. It appears plausible that selective pressures on maturation time per se generally cannot compete with viability- and fecundity-mediated selection on insect body sizes. Nevertheless, exceptions certainly exist: there are undeniable cases of SBM where this trait has evolved in response to direct selection. In such cases, either the advantage of sex difference in maturation time must have been particularly large, or fitness effects of body size have been unusually weak.

Flower Development of Heterodichogamous Juglans mandshurica (Juglandaceae).

Juglans mandshurica is a monoecious heterodichogamous species with protogynous and protandrous mating strategies that occur at a 1:1 ratio and are randomly distributed in the population. The inconsistent male and female flowering periods of the same mating type result in an imbalance of the ratio of male and female flowers, contributing to the low yield of this species. However, little more is known about its floral development. Following three consecutive years of observations, histological analysis, and scanning electron microscopy, we found that the morphological and anatomical development of the male and female flowers were synchronous. The male floral morphological development of J. mandshurica was divided into seven phases, while that of the female flower was nine. Four stages were shared between the male and female flower's anatomical development. Our findings indicate that there was minimal overlap between sexual functions within the same mating type, guaranteeing synchronization, mutual non-interference, outcrossing, and avoidance of self-fertilization. These results provide a theoretical basis for the improvement of fruit yield and quality through the reasonable allocation of protogynous and protandrous individuals in a population, and for artificial pollination control. Further, these findings lay a foundation for further research on the genetic mechanisms and environmental effects on flower development of heterodichogamous J. mandshurica.