Ontogenetic Pathways Research Articles

Jean-Baptiste Payer (1818–1860), prolific botanist and enlightened French citizen: his legacy in flower development and a need for a new, global compendium

ABSTRACT Jean-Baptiste Payer was among the pioneer botanists who promoted ontogeny as a clue to understanding the morphological nature and affinities of floral parts. He can be rightly seen as the father of floral developmental studies. In his magnus opus, Traité d’organogénie comparée de la fleur, he compared developmental stages across 333 species from 130 families sensu APGIV to explain phenomena such as the integration of the receptacle in the flower, the nature of the perianth, congenital fusion, shifts in stamen number, and the homology of carpels. His work is breathtaking not only in its scale and beauty, but also in providing a solid scientific basis for understanding the processes involved in the differentiation of flowers. Despite being pre-Darwinian, his research demonstrates the potential for evolutionary changes in flowers, in the context of the understanding of angiosperm classification at that time. Many of Payer’s ideas are still up-to-date and his observations are of great value in contemporary studies. In addition to botany, Payer had a lightning career in politics starting from the 1848 revolution. First a rioter, he then served two terms in the Constituent Assembly, before going back to science in 1852. In poor health, he died at the age of 42. This article aims at celebrating Payer as a scientist and a politician. We highlight a need for a new, global (encompassing at least all angiosperm orders) compendium on flower development that will facilitate analyses of evolutionary transitions of ontogenetic pathways. An outline of this research program is provided.

Two pathways to fleshiness: fruit ontogeny in Bromelioideae species (Bromeliaceae Juss.)

Capsule-type fruits are predominant in Bromeliaceae. However, the late divergent subfamily Bromelioideae generally presents fleshy fruits, which display a diverse range of morphologies even in related genera; however, there is almost no information regarding their anatomical and ontogenetic aspects. In this study we evaluate the fruit ontogeny of species from the major lineages of Bromelioideae, to better understand the possible paths in which fleshiness can be achieved in the subfamily. Flowers at pre-anthesis and anthesis, and fruits of Acanthostachys strobilacea, Billbergia pyramidalis, and Bromelia antiacantha were collected and processed with standard methods for analysis under light microscopy. Two basic ontogenetic pathways for achieving fleshiness were identified among the examined species. In the two former species, belonging to the core Bromelioideae, the pericarp development occurs solely through cell expansion and anticlinal cell division in the mesocarp. Conversely, in B. antiacantha, belonging to the tankless lineages, the pericarp development proceeds via both periclinal and anticlinal cell divisions of the outer and inner mesocarp. The analysis of fruit anatomy in the species included in this study highlights unprecedented traits of Bromelioideae fruits, such as the presence of the pericarp´s massive extra-carpellary portion in B. antiacantha, which contains many mucilage channels and fibrous tissue, and an intrusive septum in the carpellary portion, which acts as the main nutritive portion of the fruit. Additionally, in the present study, unique features of the ovary and the fruit, essential for characterizing the species were detailed, including the elongated placental tissue and the aliform projections of A. strobilacea. Our observations highlight distinct developmental processes to fleshy fruit formation in Bromelioideae. In this way, exploring the fruit ontogenetic diversity in Bromelioideae offers an exciting opportunity for future investigations. Besides, the unique fruit features identified bring out the importance of fruits as tools for genus delineation within this subfamily.

Comparative floral development in Mimosa (Fabaceae: Caesalpinioideae) brings new insights into merism lability in the mimosoid clade.

The genus Mimosa L. (Leguminosae; Caesalpinioideae; mimosoid clade), comprising more than 500 species, is an intriguing genus because, like other members of the mimosoid clade, it presents an enormous variation in floral characteristics and high merism lability. Thus, this study aimed to elucidate the floral development and identify which ontogenetic pathways give rise to merism variation and andromonoecy in Mimosa caesalpiniifolia, M. pudica, M. bimucronata, and M. candollei. Floral buds at various stages of development and flowers were collected, fixed, and processed for surface analysis (SEM). The development of the buds is synchronous in the inflorescences. Sepals appear simultaneously as individualized primordia in M. caesalpiniifolia and in reversed unidirectional order in M. bimucronata, with union and formation of an early ring-like calyx. Petal primordia appear in unidirectional order, with a noticeably elliptical shape in M. caesalpiniifolia. The wide merism variation in Mimosa results from the absence of organs from inception in the perianth and androecium whorls: in dimerous, trimerous, or tetramerous flowers, the additional organs primordia to compose the expected pentamerous flowers are not initiated. The haplostemonous androecium of M. pudica results from the absence of antepetalous stamens from inception. In the case of intraspecific variations (instabilities), there is no initiation and subsequent abortion of organs in the events of reduction in merosity. In addition, extra primordia are initiated in supernumerary cases. On the other hand, staminate flowers originate from the abortion of the carpel. Mimosa proved to be an excellent model for studying merism variation. The lability is associated with actinomorphic and rather congested flowers in the inflorescences. Our data, in association with others of previous studies, suggest that the high lability in merism appeared in clades that diverged later in the mimosoid clade. Thus, phylogenetic reconstruction studies are needed for more robust evolutionary inferences. The present investigation of ontogenetic processes was relevant to expand our understanding of floral evolution in the genus Mimosa and shed light on the unstable merism in the mimosoid clade.

New remains from the Cenomanian Candeleros Formation, Neuquén Basin (Patagonia, Argentina) provide insights into the formation of the sacro-urostylic complex in early pipimorph frogs (Amphibia, Anura)

An incomplete anuran skeleton collected from outcrops of the Cenomanian Candeleros Formation on the western shore of the Ramos Mexia Reservoir, Neuquén Province, Patagonia, is described herein. It consists of several partially articulated postcranial bones that are exposed in ventral view and belong to a post-metamorphic frog that is probably an adult. The axial column consists of eight opisthocoelous presacral vertebrae; fusion of the first two anterior vertebrae cannot be determined. Most of the sacrum is formed by the expanded diapophyses of Vertebra IX. However, Vertebra X also has distally expanded diapophyses that fuse to those of Vertebra IX. Traces of a suture between the urostyle and sacrum are evident. The morphology of the sacro-urostylic region casts doubts on the previous interpretation of the fused condition of sacrum and urostyle in the holotype of Avitabatrachus uliana from the same stratigraphic unit. The material described here contributes new information about the formation of the sacrum and suggests that different ontogenetic pathways are involved in formation of different sacral morphologies. The sacrum formed only by Vertebra IX probably is plesiomorphic in pipimorphs. It is hypothesized that the more complex structure described here evolved from it and incorporates postsacral vertebrae as well as synostotic fusion with the urostyle. Complete synostotic fusion of sacrum and urostyle, when present, seems to have been an event that occurred relatively late in the ontogeny of early pipimorphs. This fusion might have shifted to earlier developmental stages relative to the ancestor independently on different branches of the pipimorph tree.

Resolving the non-papilionaceous flower of Camoensia scandens, a papilionoid legume of the core genistoid clade: development, glands and insights into the pollination and systematics of the group.

Camoensia scandens is a papilionoid legume inserted in the core genistoid clade. It has large, crepuscular, scented flowers but the corolla is non-papilionaceous, which deviates from the pattern found in the subfamily. The vexillum has a folded claw, forming a tube, which is opposed to the androecium opening; all petals have yellow-gold crinkled margins. In addition, there is a long hypanthium, which stores a translucid liquid. The goal of this study is to elucidate the ontogenetic pathways that result in such a peculiar flower and the glands responsible for the sweet fragrance of the petals. Floral buds and flowers were processed for SEM, TEM and light microscopy analyses. Five sepals arise unidirectionally followed by five petals that initiate simultaneously. After the petals, 11 stamens emerge unidirectionally; a pair of adaxial stamens is opposite to the vexillum. In the intermediate developmental stages the sepals unite basally; the two adaxial sepals unite with each other to a greater extent than with the other sepals. The filaments are basally connate, forming a tube with an adaxial opening at the base. The carpel emerges concomitantly with the two abaxial antepetalous stamens. The long hypanthium forms from the outer floral organs (base of the sepals, petals, filaments) and is attached tothe base of the stipe. The corolla is noticeable in the intermediate stages of development. The crinkled golden margins house scent glands formed of a secretory epidermis with secretory trichomes and secretory subepidermal cells. The odor is composed of neutral polysaccharides, nitrogenous substances and essential oils. An extensive nectariferous region is found on the inner surface of the hypanthial tube. The nectar is translucent, viscous and released through large pores. The comparison of our data with that of other genistoid flowers enabled discussions about the pollination and systematics of the group.

Sexual Dimorphism in the Postcranial Skeleton of Dinosaurs

Sex-related variability in the tetrapod skeleton has regular patterns that reflect the different ontogenetic pathways leading to the formation of adult sexual features. In dinosaurs (as well as amniotes in general), these features are most pronounced in the morphology of postcranial bones. In males, sex-related traits reflect improved adaptations of the locomotor apparatus, while in females they are associated with the adaptation to hatching and laying eggs. Therefore, beyond the specifics of sex differences in different taxa of dinosaurs, there are also common patterns: in all adult males, neural spines are higher and limb bones are more robust than in females, while the volume of the abdominal cavity and the width of the pelvis are greater in females. The case study of ceratopsians (Ornithischia: Neoceratopsia) shows that knowledge of basic sex-related characters (those most constant in tetrapods) facilitates the search for accessory characters (more taxon-specific) that are correlated with basic ones, which provide a way to establish the limits of sexual variability typical for a given taxon.

A release from developmental bias accelerates morphological diversification in butterfly eyespots

Development can bias the independent evolution of traits sharing ontogenetic pathways, making certain evolutionary changes less likely. The eyespots commonly found on butterfly wings each have concentric rings of differing colors, and these serially repeated pattern elements have been a focus for evo-devo research. In the butterfly family Nymphalidae, eyespots have been shown to function in startling or deflecting predators and to be involved in sexual selection. Previous work on a model species of Mycalesina butterfly, Bicyclus anynana, has provided insights into the developmental control of the size and color composition of individual eyespots. Experimental evolution has also shown that the relative size of a pair of eyespots on the same wing surface is highly flexible, whereas they are resistant to diverging in color composition, presumably due to the underlying shared developmental process. This fixed color composition has been considered as a prime example of developmental bias with significant consequences for wing pattern evolution. Here, we test this proposal by surveying eyespots across the whole subtribe of Mycalesina butterflies and demonstrate that developmental bias shapes evolutionary diversification except in the genus Heteropsis which has gained independent control of eyespot color composition. Experimental manipulations of pupal wings reveal that the bias has been released through a novel regional response of the wing tissue to a conserved patterning signal. Our study demonstrates that development can bias the evolutionary independence of traits, but it also shows how bias can be released through developmental innovations, thus, allowing rapid morphological change, facilitating evolutionary diversification.

Audible calls and their ontogenetic relationship with ultrasonic vocalization in a rodent with a wide vocal range, the fat-tailed gerbil (Pachyuromys duprasi)

Ontogeny of audible and ultrasonic calls is poorly studied in Gerbillinae rodents. In this study, analysis of calls, emitted by pup and adult fat-tailed gerbils Pachyuromys duprasi during 420-s isolation-and-handling procedures, allowed testing two hypotheses. Hypothesis1 predicted that audible squeaks and clicks follow the same ontogenetic pathway (towards higher-frequency and shorter calls) that has been previously documented for the ultrasonic calls of fat-tailed gerbil. Hypothesis2 predicted that the audible call types would alternate with the ultrasonic call types along ontogeny in this species. Hypothesis1 was tested with comparison of acoustic variables of audible calls (squeaks and clicks), emitted by 1–10-day old pups and by adults. Clicks of 8.3–8.7 kHz and high-frequency squeaks of 1.92–3.57 kHz were present in pups and adults, whereas mid-frequency squeaks of 0.31−0.67 kHz and low-frequency squeaks of 0.04−0.11 kHz were only present in pups. In agreement with Hypothesis1, pup high-frequency squeaks were longer, lower in fundamental frequency and higher in peak frequency. Against predictions, clicks did not differ acoustically between pups and adults. Hypothesis2 was tested with comparison of percentages of test trials containing the audible and/or ultrasonic call types of pups, repeatedly tested in 15 age classes along ontogeny from 1 to 40 days of age and in adults. The audible calls occurred in all age classes, whereas the ultrasonic calls emerged from day five of pup life and then prevailed over the audible squeaks in all age classes. We discuss that, in fat-tailed gerbil, ontogenetic pathways of acoustic variables of audible and ultrasonic calls (towards higher-frequency and shorter calls) are unusual for rodents although are typical for social and echolocation calls of bats. The is another parallelism of acoustic communication between bats and rodents aside from the recently discovered similarity between bat ultrasonic echolocation and echo-based navigation with bouts of ultrasonic calls in blind leaping rodents.

The Late Devonian ammonoid subfamily Paratornoceratinae

Ammonoids of the subfamily Paratornoceratinae are characterised by disc-shaped adult conchs; furthermore they display a wide range of ontogenetic pathways leading to a similar adult conch morphology. The subfamily Paratornoceratinae occurs in the late early Famennian shelf sediments of various regions from the Anti-Atlas of Morocco to the Canning Basin of Western Australia; where endemic species of the genera Paratornoceras and Acrimeroceras appear in stratigraphic succession. We revise the species Paratornoceras lentiforme (Sandberger, 1857) and describe the new species Paratornoceras thuringense Korn, Bartzsch & Weyer n. sp., P. harounense Korn & Ebbighausen n. sp., P. ayense Korn & Buchwald n. sp., P. peterseni Korn & Buchwald n. sp., Acri meroceras hoppeckense Korn & Buchwald n. sp., A. ropicense Korn, Bartzsch & Weyer n. sp. and A. saalense Korn, Bartzsch & Weyer n. sp.

«All the principles of being and becoming»: Schelling’s ontogenetic hypothesis

Schelling’s Naturphilosophie was, from the outset, more concerned with ontogeny than ontology, i.e. not on what nature is but on what it does: ubiquitous creation. Therefore, the processes articulated in the Philosophy of Mythology remain instances of a philosophy driven by what might be called a post-naturalist naturalism. The two aims of this paper are, firstly, to demonstrate this nature-philosophical continuity throughout Schelling’s so-called Protean philosophical projects in order, secondly, to re-prepare Schellingian themes for current debates concerning ontology. To this end, I draw on the worldmaking and abundance postulates of Goodman and Feyerabend, respectively, to demonstrate the persistence of Schellingian ontogenetic pathways for remodelling process metaphysics for contemporary philosophy. Finally, the paper argues that the logical form of the hypothesis (antecedent and consequent) is itself consequent upon the ontogeny it hypothesises.

Levelling playing field: synchronization and rapid facial mimicry in dog-horse play

Social play is a window on cognitive and communicative abilities of species. Inter-specific play, in particular, is a fertile venue to explore the capacity to correctly perceive and interpret signals emitted by partners. Up to now, most studies have focussed on dog-human play due to the important implications such studies have in understanding the peculiar relationship we establish with our pets. Here, we focussed on social play between dogs and horses. By using a set of specific keywords (dog, horse, play, friend) we selected 20 videos of dog-horse social play (with each session lasting >30 s) from the open video-sharing website YouTube. We described the behavioural patterns composing each session by defining analogous and species-specific patterns shown by dogs and horses. The rates of self-handicapping and variability in playful actions did not differ between the two interacting subjects thus suggesting well-balanced playful tactics. The Relaxed Open Mouth (ROM, a widespread playful facial expression in mammals) was also similarly performed by dogs and horses. The Rapid Facial Mimicry (RFM) is an automatic, fast response in which individuals mimic others’ expressions (less than 1 s) that seems to have a role in mood sharing during social interactions. The dogs and horses under study showed a stronger and rapid mimicry response (less than 1 s) after perceiving ROM than after perceiving an attempt to bite (a play pattern resembling ROM in its motor performance). Taken together, our results suggest that, despite the difference in size, the phylogenetic distance, and differences in the behavioural repertoire, dogs and horses are able to fine-tune their actions thus reducing the probability of misunderstanding and escalating into aggression. One of the future challenges is to explore the role of ontogenetic pathways and familiarity in shaping inter-specific communicative ability of animals that can be at the basis of a universal language of play.

Rapid development of mature vocal patterns of ultrasonic calls in a fast-growing rodent, the yellow steppe lemming (Eolagurus luteus).

Ultrasonic vocalizations (USV) of laboratory rodents may serve as age-dependent indicators of emotional arousal and anxiety. Fast-growing Arvicolinae rodent species might be advantageous wild-type animal models for behavioural and medical research related to USV ontogeny. For the yellow steppe lemming Eolagurus luteus, only audible calls of adults were previously described. This study provides categorization and spectrographic analyses of 1176 USV calls emitted by 120 individual yellow steppe lemmings at 12 age classes, from birth to breeding adults over 90 days (d) of age, 10 individuals per age class, up to 10 USV calls per individual. The USV calls emerged since 1st day of pup life and occurred at all 12 age classes and in both sexes. The unified 2-min isolation procedure on an unfamiliar territory was equally applicable for inducing USV calls at all age classes. Rapid physical growth (1 g body weight gain per day from birth to 40 d of age) and the early (9–12 d) eyes opening correlated with the early (9–12 d) emergence of mature vocal patterns of USV calls. The mature vocal patterns included a prominent shift in percentages of chevron and upward contours of fundamental frequency (f0) and the changes in the acoustic variables of USV calls. Call duration was the longest at 1–4 d, significantly shorter at 9–12 d and did not between 9-12-d and older age classes. The maximum fundamental frequency (f0max) decreased with increase of age class, from about 50 kHz in neonates to about 40 kHz in adults. These ontogenetic pathways of USV duration and f0max (towards shorter and lower-frequency USV calls) were reminiscent of those in laboratory mice Mus musculus.

Clinical implications of age-related change of the mandibular plane angle.

To identify trajectories of ontogenetic change in the mandibular plane angle (MPA) and to describe the influence of sex and other factors on MPA during growth. The data consisted of 7026 MPA measurements from lateral cephalographs representing longitudinal series from ages 6 to 21 for 728 individuals from the Craniofacial Growth Consortium Study (CGCS). Facial type was determined from MPA for each assessment, with the assessment closest to age 18 representing the adult facial type. The sample includes 366 males and 362 females, each with between 2 and 15 cephalographs. The mean number of cephalographs per individual is 10. Variation in childhood MPA (earliest assessment between 6 and 9years of age) and adult MPA (closest assessment to age 18 between 15 and 21years of age), and change in MPA from childhood to adulthood were compared by sex and adult facial type using ANOVA and post hoc t tests. Mandibular plane angle decreased from childhood to adulthood in 92% of males and 81% of females, yet increased in 36% of males and 50% of females with the hyper-divergent adult facial type. Childhood MPA and overall change in MPA were significantly different by adult facial type. Adult facial type is associated with differences in childhood MPA and change in MPA during growth. There are multiple ontogenetic pathways by which an individual can achieve a normo-divergent adult facial type, and an individual's childhood MPA does not necessarily correspond to his or her adult facial type.

Rise of an empire: analyzing the high diversity of the earliest sauropodomorph dinosaurs through distinct hypotheses

ABSTRACT Several new early sauropodomorphs have been described from Carnian South American strata that include the oldest unambiguous dinosaurs worldwide. Hence, these findings suggest a high diversity in the origin of the group. Here we offer three hypotheses based in novel data that can explain this diversity at the first branches of the long evolutionary tree of the sauropodomorphs. The first hypothesis explains that the Triassic specimens excavated from Brazilian strata are not coeval owing to the lack of stratigraphic control. Fortunately, new studies are constraining the age of Triassic outcrops from Brazil. The second hypothesis suggests an overstated diversity in response to the unknown ontogenetic pathways adopted by early dinosaurs. This hypothesis still demands new findings in order to clarify these ontogenetic pathways. The third hypothesis supports a high diversity in the same time span in response to distinct ecological roles adopted by the early sauropodomorphs. Indeed, there are specimens with different tooth morphologies, indicating diverse feeding strategies. This hypothesis is supported in an ecomorphological analysis derived from discrete anatomical traits. Therefore, although facing many conflicting questions regarding alpha taxonomy of Carnian sauropodomorphs, new discoveries and alternative approaches are leading towards a better understanding of the early evolution of Sauropodomorpha.

Origin and development of classical dendritic cells.

Classical dendritic cells (cDCs) are mononuclear phagocytes of hematopoietic origin specialized in the induction and regulation of adaptive immunity. Initially defined by their unique T cell activation potential, it became quickly apparent that cDCs would be difficult to distinguish from other phagocyte lineages, by solely relying on marker-based approaches. Today, cDCs definition increasingly embed their unique ontogenetic features. A growing consensus defines cDCs on multiple criteria including: (1) dependency on the fms-like tyrosine kinase 3 ligand hematopoietic growth factor, (2) development from the common DC bone marrow progenitor, (3) constitutive expression of the transcription factor ZBTB46 and (4) the ability to induce, after adequate stimulation, the activation of naïve T lymphocytes. cDCs are a heterogeneous cell population that contains two main subsets, named type 1 and type 2 cDCs, arising from divergent ontogenetic pathways and populating multiple lymphoid and non-lymphoid tissues. Here, we present recent knowledge on the cellular and molecular pathways controlling the specification and commitment of cDC subsets from murine and human hematopoietic stem cells.

Floral development of Moraceae species with emphasis on the perianth and androecium

The mulberry and fig family (Moraceae) has tiny flowers with a single whorled or absent perianth and inner whorls with a reduced number of organs. Relevant questions about this reduced floral structure still remain unresolved. Thus, we studied the ontogenic processes that culminate in such a reduced flower, as well as the close relationship between the floral envelope and the androecium in Brosimum gaudichaudii, Castilla elastica, Clarisia ilicifolia, Maclura tinctoria and Morus nigra. Flower buds and flowers were processed for surface (scanning electron microscopy) and anatomical (light microscopy) analyses. The perianth consists of sepals, except the flowers of B. gaudichaudii and C. elastica (staminate), in which the perianth is lacking. The staminate flower of B. gaudichaudii exhibits a bracteole enveloping the stamens. In monochlamydeous flowers the order of sepal initiation is helical or asynchronous. No petals are initiated. The calyx displays different degrees of synorganization being united only basally or along its entire extension. The sepals can have tector and glandular trichomes or only tector trichomes. Laticifers, phenolic and crystalliferous idioblasts occur in the sepal mesophyll. Stamens initiate concomitant with the pistillode in B. gaudichaudii and after initiation of the pistillode in M. tinctoria and M. nigra. In C. ilicifolia there is no pistillode and the stamens initiate after the sepals. The stamens show variation in filament shape and connective structure. The filament is inflexed in M. tinctoria and M. nigra and straight in the other species, although these structures are anatomically similar. The connective is expanded (except in M. nigra and C. ilicifolia) and has phenolic idioblasts. We conclude that the tiny flowers of these species result of two distinct ontogenetic pathways: absence of organs from the inception and by abortion, mechanisms that act to decrease the number of floral whorls as well as the number of organs in each whorl.

A novel lncRNA-focus expression signature for survival prediction in endometrial carcinoma

BackgroundEndometrial cancer (UCEC) is a complex malignant tumor characterized by both genetic level and clinical trial. Patients with UCEC exhibit the similar clinical features, however, they have distinct outcomes due to molecular heterogeneity. The aim of this study was to access the prognostic value of long non-coding RNAs (lncRNAs) in UCEC patients and to identify potential lncRNA signature for predicting patients’ survival and improving patient-tailored treatment.MethodsWe performed a comprehensive genome-wide analysis of lncRNA expression profiles and clinical data in a large cohort of 301 UCEC patients. UCEC patients were randomly divided into the discovery cohort (n = 150) and validation cohort (n = 151). A novel lncRNA-focus expression signature was identified in the discovery cohort, and independently accessed in the validation cohort. Additionally, the lncRNA signature was evaluated by multivariable Cox regression and stratification analysis as well as functional enrichment analysis.ResultsWe detected a novel lncRNA-focus expression signature (LFES) consisting of 11 lncRNAs that were associated with survival based on risk scoring strategy in UCEC. The risk score based on the LFES was able to separate patients of discovery cohort into high-risk and low-risk groups with significantly different overall survival and progression-free survival, and has been successfully confirmed in the validation cohort. Furthermore, the LFES is an independent prognostic predictor of survival and demonstrates superior prognostic performance compared with the clinical covariates for predicting 5-year survival (AUC = 0.887). Functional analysis has linked the expression of prognostic lncRNAs to well-known tumor suppressor or ontogenetic pathways in endometrial carcinogenesis.ConclusionsOur study revealed a novel 11-lncRNA signature to predict survival of UCEC patient. This lncRNA signature may be a valuable and alternative marker for risk evaluation to aid patient-tailored treatment and improve the outcome of patients with UCEC.

How to become larger: ontogenetic basis of among‐population size differences in a moth

AbstractEvolutionary studies on animal body size have primarily focussed on selective pressures operating during the adult life. In contrast, ontogenetic pathways leading to differently sized adults have received less attention. In the present study, based on a common garden experiment, we report considerable genetic differences in body size among European populations of Ematurga atomaria (L.) (Lepidoptera: Geometridae). In terms of body mass, the moths from a southern (Georgian) population are twice as large as their northern (Estonian) conspecifics. Detailed monitoring of larval growth schedules revealed that the size difference arises through a longer development period of the Georgian larvae, with no difference in the number of instars. Differential (instantaneous) growth rates of the larvae do not differ between the populations. Eggs and newly hatched larvae are larger in the Georgian population but the difference vanishes in the second instar. The larger size of the Georgian moths is regained through higher relative mass increments during each of the three final instars. Such gradual ‘accumulation of the difference’ confirms the idea about constraints on substantial evolutionary changes in growth patterns within a single instar. The larger Georgian moths were found to be considerably more fecund which implies a strong selection for large female size. It remains unclear which counteracting selective pressures have favored the smaller size of Estonian conspecifics. As the associated difference in egg size appears not to be carried over to larger larval size, the adaptive value of larger eggs is not likely in contributing to the prospective large adult size. The larger eggs of the Georgian population should have an adaptive value per se, or represent a mechanistic consequence of larger maternal body size.

Iterative ontogenetic development of ammonoid conch shapes from the Devonian through to the Jurassic

AbstractWe measured longitudinal growth in conch cross‐sections of 177 Devonian to Jurassic ammonoid species to test whether conch ontogenetic development parallels the iterative evolution of pachyconic or globular conch shapes. Ontogenetic trajectories of two cardinal conch parameters, conch width index and umbilical width index, show a few common recurring ontogenetic pathways in terms of the number of ontogenetic phases. The most common, with three phases in the conch width index (decrease–increase–decrease) and umbilical width index (increase–decrease–increase), is termed here C‐mode ontogeny (after the Carboniferous genus Cravenoceras). Many of the studied globular Palaeozoic and Triassic species (of the latter, particularly the arcestid ammonoids) share principal patterns in the triphasic C‐mode conch ontogeny in closely related groups but also between unrelated groups as well. The repetition of conch growth patterns is an example of convergent evolution of the entire life history of globular ammonoids. The studied Jurassic globular shaped ammonoids deviate from the growth patterns seen in earlier groups showing less pronounced ontogenetic trajectories with nearly isometric or weakly asymmetric growth without distinct phases. This trajectory is termed here M‐mode ontogeny (after the Jurassic genus Macrocephalites). No major change in the ontogenetic modes of pachyconic and globular ammonoids occurred moving from the Palaeozoic into the Mesozoic; the survivors of the end‐Permian extinction event iteratively developed conch ontogenies similar to those of Palaeozoic forms. In contrast, the Triassic–Jurassic boundary marks the major event with the evolution of some cardinal conch parameters relating to globular ammonoid ontogeny.

Male disguised females: costs and benefits of female‐limited dimorphism in a butterfly

1. In polymorphic species, two or more discrete phenotypes co‐occur simultaneously. Sex‐limited polymorphism is a particular case of polymorphism, in which several discrete morphs coexist within one of the two sexes only. Several hypotheses were proposed to explain the existence and the maintenance of sex‐limited polymorphism in insects: (i) the morphs have similar fitness, such as similar survival and expected fecundity, and their frequencies vary randomly (i.e. the null hypothesis); (ii) harassment by males is reduced towards the less common female morph, in this case andromorph females (i.e. the male mimicry and learned mate recognition hypotheses); (iii) morphs differ in predation risk (i.e. the predation hypothesis); or (iv) morphs differ in thermoregulation ability (i.e. the thermoregulation hypothesis).2. Field observations and experiments were employed to compare the relative support of these hypotheses using dimorphic females of the bog fritillary butterfly. Differences were detected between morphs in survival, fecundity, harassment by males, predation pressure and thermal properties, thereby rejecting the null hypothesis.3. The lifestyle of both morphs is associated with different costs and benefits, with advantages in daily survival and precocious emergence for the gynomorph females, and advantages in fecundity, predation and male harassment for the andromorph females. Besides, as the bog fritillary butterfly is protandrous (i.e. males emerge before females), the longer development of andromorph females puts them at risk of emerging when all the males are dead. The results raise the question as to which mechanisms control the ontogenetic pathways driving the production of the two morphs (i.e. genetic polymorphism or phenotypic plasticity).