Ontogenetic Variation in the Thermal Biology of Yarrow's Spiny Lizard,Sceloporus jarrovii

Climate change is rapidly altering the way current species interact with their environment to satisfy life-history demands. In areas anticipated to experience extreme warming, rising temperatures are expected to diminish population growth, due either to environmental degradation, or the inability to tolerate novel temperature regimes. Determining how at risk ectotherms, and lizards in particular, are to changes in climate traditionally emphasizes the thermal ecology and thermal sensitivity of physiology of adult members of a population. In this study, we reveal ontogenetic differences in thermal physiological and ecological traits that have been used to anticipate how ectotherms will respond to climate change. We show that the thermal biological traits of juvenile Yarrow’s Spiny Lizards (Sceloporus jarrovii) differ from the published estimates of the same traits for adult lizards. Juvenile S. jarrovii differ in their optimal performance temperature, field field-active body temperature, and critical thermal temperatures compared to adult S. jarrovii. Within juvenile S. jarrovii, males and females exhibit differences in field-active body temperature and desiccation tolerance. Given the observed age- and sex-related variation in thermal physiology, we argue that not including physiological differences in thermal biology throughout ontogeny may lead to misinterpretation of patterns of ecological or evolutionary change due to climate warming. Further characterizing the potential for ontogenetic changes in thermal biology would be useful for a more precise and accurate estimation of the role of thermal physiology in mediating population persistence in warmer environments.     

Trophic niche ontogeny and palaeoecology of early Toarcian Stenopterygius (Reptilia: Ichthyosauria)

Reconstructing ecological niche shifts during ontogeny in extinct animals with no living analogues is difficult without exceptional fossil collections. Here we demonstrate how a previously identified ontogenetic shift in the size and shape of the dentition in the early Toarcian ichthyosaur Stenopterygius quadriscissus accurately predicts a particular dietary shift. The smallest S. quadriscissus fed on small, burst‐swimming fishes, with a steady shift towards faster moving fish and cephalopods with increasing body size. Larger adult specimens appear to have been completely reliant on cephalopods, with fish completely absent from gut contents shortly after onset of sexual maturity. This is consistent with a previously proposed ontogenetic niche shift based on tooth shape and body size, corroborating the idea that dental ontogeny may be a useful predictor of dietary shifts in marine reptiles. Applying the theoretical framework used here to other extinct species will improve the resolution of palaeoecological reconstructions, where appropriate sample sizes exist.     

When size makes a difference: allometry, life-history and morphological evolution of capuchins (Cebus) and squirrels (Saimiri) monkeys (Cebinae, Platyrrhini)

Background

How are morphological evolution and developmental changes related? This rather old and intriguing question had a substantial boost after the 70s within the framework of heterochrony (changes in rates or timing of development) and nowadays has the potential to make another major leap forward through the combination of approaches: molecular biology, developmental experimentation, comparative systematic studies, geometric morphometrics and quantitative genetics. Here I take an integrated approach combining life-history comparative analyses, classical and geometric morphometrics applied to ontogenetic series to understand changes in size and shape which happen during the evolution of two New World Monkeys (NWM) sister genera.

Results

Cebus and Saimiri share the same basic allometric patterns in skull traits, a result robust to sexual and ontogenetic variation. If adults of both genera are compared in the same scale (discounting size differences) most differences are small and not statistically significant. These results are consistent using both approaches, classical and geometric Morphometrics. Cebus is a genus characterized by a number of peramorphic traits (adult-like) while Saimiri is a genus with paedomorphic (child like) traits. Yet, the whole clade Cebinae is characterized by a unique combination of very high pre-natal growth rates and relatively slow post-natal growth rates when compared to the rest of the NWM. Morphologically Cebinae can be considered paedomorphic in relation to the other NWM. Geometric morphometrics allows the precise separation of absolute size, shape variation associated with size (allometry), and shape variation non-associated with size. Interestingly, and despite the fact that they were extracted as independent factors (principal components), evolutionary allometry (those differences in allometric shape associated with intergeneric differences) and ontogenetic allometry (differences in allometric shape associated with ontogenetic variation within genus) are correlated within these two genera. Furthermore, morphological differences produced along these two axes are quite similar. Cebus and Saimiri are aligned along the same evolutionary allometry and have parallel ontogenetic allometry trajectories.

Conclusion

The evolution of these two Platyrrhini monkeys is basically due to a size differentiation (and consequently to shape changes associated with size). Many life-history changes are correlated or may be the causal agents in such evolution, such as delayed on-set of reproduction in Cebus and larger neonates in Saimiri.     

New visions of dental tissue research: Tooth development,chemistry, and structure

Teeth are one of the best preserved and most commonly recovered elements in primate fossil assemblages. Taxonomic, functional, and phylogenetic hypotheses often rely on dental characters, despite considerable evidence of homoplasy in tooth form and large variation in tooth size within and among primates.^1,2 Recent studies have led to new areas of research centered on incremental tooth development, chemical composition, and internal structure. Due to rapid technological developments in imaging and elemental sampling, these new approaches have the potential to increase our understanding of developmental biology, including not only changes in the pace of growth and reproduction, but also our assessments of diets, migration patterns, environments, and taxonomy. The integration of these temporal, chemical, and structural approaches heralds a bright future for the role of dental tissue research in evolutionary anthropology. © 2008 Wiley‐Liss, Inc.     

Dynamic Scaling in the Growth of a Non-Branching Plant,Cardiocrinum cordatum

We investigated whole-plant leaf area in relation to ontogenetic variation in leaf-size for a forest perennial herb, Cardiocrinum cordatum. The 200-fold ontogenetic variability in C. cordatum leaf area followed a power-law dependence on total leaf number, a measure of developmental stage. When we normalized for plant size, the function describing the size of single leaves along the stem was similar among different-sized plants, implying that the different-sized canopies observed at different times in the growth trajectory were fundamentally similar to each other. We conclude that the growth trajectory of a population of C. cordatum plant leaves obeyed a dynamic scaling law, the first reported for a growth trajectory at the whole-plant level.     

Ontogenetic trajectories in the ornithischian endocranium

Understanding ontogenetic and developmental patterns is critical for reconstructing the life history of fossil vertebrates. In dinosaurs, ontogenetic studies have nearly exclusively focused on changes in the cranial and post‐cranial skeleton, whereas ontogenetic changes in the endocranium have received little attention. Here, we present digital reconstructions of the brain and inner ear anatomy of two ontogenetic stages of the Jurassic ornithischian dinosaur Dysalotosaurus lettowvorbecki. Results show that the endocranial anatomy underwent considerable changes during growth, including a rostrocaudal elongation of the olfactory apparatus, a reduction in the cephalic and pontine flexure and an increase in cerebellum size. Functional elements, such as the cerebral hemispheres and the inner ear, were already well developed in early ontogenetic stages, indicating a large degree of precociality. The anisotropic pattern of size and shape changes in the endocranium further indicates that ontogenetic trajectories may be controlled by functional and environmental demands in the different growth stages in Dysalotosaurus lettowvorbecki. The occurrence of similar ontogenetic patterns in the endocranial anatomy of derived ornithopod dinosaurs suggests a more widespread distribution of this growth trajectory.     

Osteological Variation among Extreme Morphological Forms in the Mexican Salamander Genus Chiropterotriton (Amphibia: Plethodontidae): Morphological Evolution And Homoplasy

Osteological variation is recorded among and within four of the most distinctive species of the Mexican salamander genus Chiropterotriton. Analysis of the data is consistent with the monophyletic status of the genus and documents previously unrecorded intraspecific and interspecific variation. Most of the recorded variation involves qualitative and quantitative proportional differences, but four fixed differences constitute autapomorphic states that affirm and diagnose some species (C. dimidiatus, C. magnipes). Osteological variation in 15 characters is analyzed with respect to predictions generated from four hypotheses: 1) phylogeny, 2) adaptation to specific habitats (the four species include cave-dwelling, terrestrial, and arboreal forms), 3) size-free shape, and 4) size. High levels of intraspecific variation suggest that the characters studied are not subject to rigid functional constraints in salamanders, regardless of size. The pattern predicted by the hypothesis based on size differences seen among these four Chiropterotriton species matches most closely the observed pattern of relative skull robustness. Since size change and heterochrony are often associated in plethodontid evolution, it is likely that changes in developmental timing play a role in the morphological transitions among these morphologically diverse taxa. Webbed feet, miniaturization, body shape, and an unusual tarsal arrangement are morphologies exhibited in species of Chiropterotrition that are shown to be homoplastic with other clades of tropical plethodontids. Although extensive homoplasy in salamanders might be seen as a roadblock to unraveling phylogenetic hypotheses, the homologous developmental systems that appear to underlie such homoplasy may reveal common and consistent evolutionary processes at work.     

Patterns of postnatal development in skulls of lynxes,genus Lynx (Mammalia: Carnivora)

Studies on ossification patterns and other ontogenetic events associated with postnatal cranial growth of wild felids are scarce. An analysis of developmental processes undergone by several cranial structures (presphenoidal and sphenooccipital synchondroses, temporal and sagittal crests, and deciduous and permanent teeth) during postnatal growth has been conducted on a sample of 336 specimens belonging to the four Recent species of lynxes (Lynx pardinus, Lynx lynx, Lynx rufus, and Lynx canadensis). Age has been estimated based on tooth replacement, skull size, and by counting the annual lines of cementum growth. Comparison of the results obtained for each of the four species reveal (1) a single pattern for both tooth replacement and ossification of the sphenooccipital synchondrosis, (2) two ossification patterns for the presphenoidal synchondrosis, (3) a common pattern for development of temporal ridges and sagittal crest showing different degrees of morphological expression, and (4) evidence suggesting the involvement of a heterochronic process, neoteny, in the morphological differentiation of several populations and species of the genus Lynx. These data also support the hypothesis that processes involved in the replacement of carnassials are based on functional requirements. © 1996 Wiley-Liss, Inc.     

Skull ontogeny in Arrhinoceratops brachyops (Ornithischia: Ceratopsidae) and other horned dinosaurs

Disentangling ontogenetic from interspecific variation is key to understanding biodiversity in the fossil record, yet information on growth in the ceratopsid subfamily Chasmosaurinae is sparse. Here, we describe the partial skull of a juvenile chasmosaurine, attributed to Arrhinoceratops brachyops, within the context of more mature specimens of this species, to better understand the ontogenetic transformations therein. We show that as A. brachyops matured, the postorbital horncores became longer and shifted from a posterior to an anterior inclination, the delta‐shaped frill epiossifications became lower and fused to the underlying frill, and the face became more elongate. In these respects, A. brachyops closely resembled Triceratops, suggesting that these ontogenetic changes may have been common to all long‐horned chasmosaurines. However, an event‐paired cladistic analysis of Chasmosaurinae using a standardized matrix of 24 developmental characters reveals that the relative timing of ontogenetic events in Arrhinoceratops was more like that of Chasmosaurus, particularly in the relatively late reduction in scalloping around the frill margins. Thus, the ontogenetic similarities between Arrhinoceratops and Triceratops appear to be plesiomorphic, partly related to the retention of the elongate postorbital horncores, which are primitive for Ceratopsidae. This study elucidates the otherwise contentious evolutionary relationships of Arrhinoceratops, and highlights the importance of ontogenetic data for resolving phylogenies when morphological data from adults alone are inadequate. © 2015 The Linnean Society of London     

Skeletal heterochrony is associated with the anatomical specializations of snakes among squamate reptiles

Snakes possess a derived anatomy, characterized by limb reduction and reorganization of the skull and internal organs. To understand the origin of snakes from an ontogenetic point of view, we conducted comprehensive investigations on the timing of skeletal elements, based on published and new data, and reconstructed the evolution of the ossification sequence among squamates. We included for the first time Varanus, a critical taxon in phylogenetic context. There is comprehensive delay in the onset of ossification of most skeletal elements in snakes when compared to reference developmental events through evolution. We hypothesize that progressing deceleration accompanied limb reduction and reorganization of the snake skull. Molecular and morphological studies have suggested close relationship of snakes to either amphisbaenians, scincids, geckos, iguanids, or varanids. Likewise, alternative hypotheses on habitat for stem snakes have been postulated. Our comprehensive heterochrony analyses detected developmental shifts in ossification for each hypothesis of snake origin. Moreover, we show that reconstruction of ancestral developmental sequences is a valuable tool to understand ontogenetic mechanisms associated with major evolutionary changes and test homology hypotheses. The “supratemporal” of snakes could be homolog to squamosal of other squamates, which starts ossification early to become relatively large in snakes.     

A quantitative approach to the cranial ontogeny of <Emphasis Type="Italic">Lycalopex culpaeus</Emphasis> (Carnivora: Canidae)

The study of cranial ontogeny is important for understanding the relationship between form and function in developmental, ecological, and evolutionary contexts. The transition from lactation to the diet of adult carnivores must be accompanied by pronounced modifications in skull morphology and feeding behavior. Our goal was to study relative growth and development in the skull ontogeny of the canid Lycalopex culpaeus, and interpret our findings in a functional context, thereby exploring the relationship between changes in shape and size with dietary habits and age stages. We performed quantitative analyses, including multivariate allometry and geometric morphometrics. Our results indicate that shape changes are related to functional improvements of the jaw mechanics related for food catching/processing. Estimates of full muscle size, mechanical advantage, and adult cranial shape are reached after sexual maturity, while adult mandible and skull size are reached after weaning, which is related to diet change (incorporation of meat and other food items). The ontogenetic pattern observed in L. culpaeus is similar to those observed in Canis familiaris and C. latrans. However, the magnitude of change seen in L. culpaeus is smaller than those seen in the felid Puma concolor and considerably smaller than those seen in the bone cracker hyaenid Crocuta crocuta. These patterns are associated with dietary habits and specializations in skull anatomy, as L. culpaeus, domestic dog and coyote are generalist species compared with hypercarnivores such as C. crocuta and P. concolor.     

Multilevel assessment of the Lacertid lizard cranial modularity

Different factors and processes that produce phenotypic variation at the individual, population, or interspecific level can influence or alter the covariance structure among morphological traits. Therefore, studies of the patterns of integration and modularity at multiple levels—static, ontogenetic, and evolutionary, can provide invaluable data on underlying factors and processes that structured morphological variation, directed, or constrained evolutionary changes. Our dataset, consisting of cranium shape data for 14 lizard species from the family Lacertidae, with substantial samples of hatchlings and adults along with their inferred evolutionary relationships, enabled us to assess modularity and morphological integration at all three levels. Five, not mutually exclusive modularity hypotheses of lizard cranium, were tested, and the effects of allometry on intensity and the pattern of integration and modularity were estimated. We used geometric morphometrics to extract symmetric and asymmetric, as well as allometric and nonallometric, components of shape variation. At the static level, firm confirmation of cranial modularity was found for hypotheses which separate anterior and posterior functional compartments of the skull. At the ontogenetic level, two alternative hypotheses (the “anteroposterior” and “neurodermatocranial” hypotheses) of ventral cranial modularity were confirmed. At the evolutionary level, the “neurodermatocranial” hypothesis was confirmed for the ventral cranium, which is in accordance with the pattern observed at the ontogenetic level. The observed pattern of static modularity could be driven by functional demands and can be regarded as adaptive. Ontogenetic modularity and evolutionary modularity show the same developmental origin, indicating conservatism of modularity patterns driven by developmental constraints.     

Evolutionary development of the neurocranium in Dissorophoidea (Tetrapoda: Temnospondyli), an integrative approach

SUMMARY Ontogenetic data can play a prominent role in addressing questions in tetrapod evolution, but such evidence from the fossil record is often incompletely considered because it is limited to initiation of ossification, or allometric changes with increasing size. In the present study, specimens of a new species of an archaic amphibian (280 Myr old), Acheloma n. sp., a member of the temnospondyl superfamily Dissorophoidea and the sister group to Amphibamidae, which is thought to include at least two of our modern amphibian clades, anurans and caudatans (Batrachia), provides us with new developmental data. We identify five ontogenetic events, enabling us to construct a partial ontogenetic trajectory (integration of developmental and transformation sequence data) related to the relative timing of completion of neurocranial structures. Comparison of the adult amphibamid morphology with this partial ontogeny identifies a heterochronic event that occurred within the neurocranium at some point in time between the two taxa, which is consistent with the predictions of miniaturization in amphibamids, providing the first insights into the influence of miniaturization on the neurocranium in a fossil tetrapod group. This study refines hypotheses of large‐scale evolutionary trends within Dissorophoidea that may have facilitated the radiation of amphibamids and, projected forward, the origin of the generalized batrachian skull. Most importantly, this study highlights the importance of integrating developmental and transformation sequence data, instead of onset of ossification alone, into investigations of major events in tetrapod evolution using evidence provided by the fossil record, and highlights the value of even highly incomplete growth series comprised of relatively late‐stage individuals.     

Short Faces,Big Tongues: Developmental Origin of the Human Chin

During the course of human evolution, the retraction of the face underneath the braincase, and closer to the cervical column, has reduced the horizontal dimension of the vocal tract. By contrast, the relative size of the tongue has not been reduced, implying a rearrangement of the space at the back of the vocal tract to allow breathing and swallowing. This may have left a morphological signature such as a chin (mental prominence) that can potentially be interpreted in Homo. Long considered an autopomorphic trait of Homo sapiens, various extinct hominins show different forms of mental prominence. These features may be the evolutionary by-product of equivalent developmental constraints correlated with an enlarged tongue. In order to investigate developmental mechanisms related to this hypothesis, we compare modern 34 human infants against 8 chimpanzee fetuses, whom development of the mandibular symphysis passes through similar stages. The study sets out to test that the shared ontogenetic shape changes of the symphysis observed in both species are driven by the same factor – the space restriction at the back of the vocal tract and the associated arrangement of the tongue and hyoid bone. We apply geometric morphometric methods to extensive three-dimensional anatomical landmarks and semilandmarks configuration, capturing the geometry of the cervico-craniofacial complex including the hyoid bone, tongue muscle and the mandible. We demonstrate that in both species, the forward displacement of the mental region derives from the arrangement of the tongue and hyoid bone, in order to cope with the relative horizontal narrowing of the oral cavity. Because humans and chimpanzees share this pattern of developmental integration, the different forms of mental prominence seen in some extinct hominids likely originate from equivalent ontogenetic constraints. Variations in this process could account for similar morphologies.     

The ontogeny of the lower reproductive tract of the landsnail Helix aspersa (Gastropoda: Mollusca)

We provide a size-based ontogenetic sequence of the development and differentiation of the lower reproductive tract of the heterobranch gastropod Helix aspersa (Müller 1774). Twelve development stages distributed among nine size classes were recognized based on readily visible changes in morphology and changes in tissue density. Geometric morphometrics was used to calculate the deformation between stages as represented by thin-plate spline bending energies. The developmental stages and sequence of developmental events are also compared to previously published scenarios for the evolution of stylommatophoran and other pulmonate reproductive tracts. These comparisons suggest that heterochronies, which include both acceleration and retardation, are operating in the morphological evolution of the pulmonate lower reproductive tract. This supports previous observations that largest number of developmental changes coincides with the transition to sexual maturity, which is also seen in the exponential curve of bending energies we observed in Helix aspersa. The belated organogenesis makes the ontogeny of the complex hermaphroditic reproductive system of pulmonates readily observable in size-friendly juveniles. This observation, coupled with the ease of raising individuals in the laboratory, recommends Helix aspersa as a potential model laboratory system for investigating molluscan evolutionary development.     

Patterns of intraspecific variation through ontogeny: a case study of the Cretaceous nautilid Eutrephoceras dekayi and modern Nautilus pompilius

The magnitude and ontogenetic patterns of intraspecific variation can provide important insights into the evolution and development of organisms. Understanding the intraspecific variation of organisms is also a key to correctly pursuing studies in major fields of palaeontology. However, intraspecific variation has been largely overlooked in ectocochleate cephalopods, particularly nautilids. Furthermore, little is known regarding the evolutionary pattern. Here, we present morphological data for the Cretaceous nautilid Eutrephoceras dekayi (Morton) and the modern nautilid Nautilus pompilius Linnaeus through ontogeny. The data are used to describe conch morphology and to elucidate the evolutionary patterns of intraspecific variation. We discovered a similar overall pattern of growth trajectories and the presence of morphological changes at hatching and maturity in both taxa. We also found that intraspecific variation is higher in earlier ontogeny than in later ontogeny in both taxa. The high variation in earlier ontogeny may imply increased flexibility in changing the timing of developmental events, which probably played an important role in nautilid evolution. We assume that the decrease in variation in later ontogeny reflects developmental constraints. Lastly, we compared the similarity/dissimilarity of ontogenetic patterns of variation between taxa. Results reveal that the similarity/dissimilarity of the ontogenetic pattern differs between E. dekayi and N. pompilius. We conclude that this shift in the ontogenetic pattern of variation may be rooted in changes in the developmental programme of nautilids through time. We propose that studying ontogenetic patterns of intraspecific variation can provide new insights into the evolution and development of organisms.     

Floral ontogenetic evidence of repeated speciation via paedomorphosis in subtribe Orchidinae (Orchidaceae)

Thoroughly sampled molecular phylogenies of the dominantly European orchid subtribe Orchidinae were used to identify a pair and a triplet of recently diverged species in which: (1) divergence involved substantial changes in floral morphology, particularly in the labellar lobes and spur; and (2) the polarity of those changes could be inferred phylogenetically. Floral ontogeny in the selected species was documented in detail through macromorphological, light microscopic, and scanning electron microscopic study of a wide range of ontogenetic stages. All study species showed differentiation of perianth segments earlier than the gynostemium. Unsurprisingly, component parts of the basic floral organs (gymnostemial auricles and rostellum, labellar lateral lobes, and spur) were initiated relatively late, the spur and ovary continuing to expand beyond anthesis. The predominant evolutionary pattern identified in the two case studies was paedomorphosis via progenesis (earlier offset of growth); this credibly explained the reduction in spur size and lateral lobing of the labellum in Gymnadenia odoratissima and, especially, G. austriaca relative to G. conopsea. Loss of resupination in G. austriaca was best viewed as the deletion of a formerly terminal ontogenetic stage. Radical reduction of the spur of Dactylorhiza viridis relative to D. fuchsii was also attributed to progenesis, although the long, narrow outline and relatively short central lobe of its labellum were attributed to increased growth of the lateral lobes (i.e. hypermorphosis resulting in peramorphosis). Microscopic study of epidermal cell types on the labellum and spur suggested a degree of decoupling of micromorphological from macromorphological transitions, although both were subject to heterochronic shifts. Each of the two case studies was consistent with, but not proof of, saltational macroevolution operating via functional changes in one or more key developmental genes. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 157 , 429–454.     

Ontogenetic integration between force production and force reception: a case study in Ctenomys (Rodentia: Caviomorpha)

During ontogeny, complex adaptations undergo changes that sometimes entail different functional capabilities. This fact constrains the behaviour of organisms at each developmental stage. Rodents have ever‐growing incisors for gnawing, and a powerful jaw musculature. The incisors are long enough, relative to their diameter, to be affected by bending stresses. This is particularly true in the subterranean Ctenomys that uses its incisors for digging. We measured bite force (BF) in individuals of different ages using a force transducer. We estimated incisor section modulus Z, a geometrical parameter proportional to bending strength. A relative strength indicator was calculated as S = Z/BF incisor length. We found that ontogenetic BF scales to body mass with positive allometry. However, an anova showed non‐significant differences in S, neither between sexes nor among age classes. This result implies that during growth, incisors might have a rather similar ability to withstand bending stresses from increasing masticatory forces, what may be considered evidence of ontogenetic integration of force production (by muscles) and force reception (by the incisors). This fact well correlates with the observation that pups and juveniles of C. talarum incorporate solid foods shortly after birth, and they are able to dig burrows early in life.     

The Response of the Alpine Dwarf Shrub Salix herbacea to Altered Snowmelt Timing: Lessons from a Multi-Site Transplant Experiment

Climate change is altering spring snowmelt patterns in alpine and arctic ecosystems, and these changes may alter plant phenology, growth and reproduction. To predict how alpine plants respond to shifts in snowmelt timing, we need to understand trait plasticity, its effects on growth and reproduction, and the degree to which plants experience a home-site advantage. We tested how the common, long-lived dwarf shrub Salix herbacea responded to changing spring snowmelt time by reciprocally transplanting turfs of S. herbacea between early-exposure ridge and late-exposure snowbed microhabitats. After the transplant, we monitored phenological, morphological and fitness traits, as well as leaf damage, during two growing seasons. Salix herbacea leafed out earlier, but had a longer development time and produced smaller leaves on ridges relative to snowbeds. Longer phenological development times and smaller leaves were associated with reduced sexual reproduction on ridges. On snowbeds, larger leaves and intermediate development times were associated with increased clonal reproduction. Clonal and sexual reproduction showed no response to altered snowmelt time. We found no home-site advantage in terms of sexual and clonal reproduction. Leaf damage probability depended on snowmelt and thus exposure period, but had no short-term effect on fitness traits. We conclude that the studied populations of S. herbacea can respond to shifts in snowmelt by plastic changes in phenology and leaf size, while maintaining levels of clonal and sexual reproduction. The lack of a home-site advantage suggests that S. herbacea may not be adapted to different microhabitats. The studied populations are thus unlikely to react to climate change by rapid adaptation, but their responses will also not be constrained by small-scale local adaptation. In the short term, snowbed plants may persist due to high stem densities. However, in the long term, reduction in leaf size and flowering, a longer phenological development time and increased exposure to damage may decrease overall performance of S. herbacea under earlier snowmelt.     

Larval growth and allometry in the cabbage butterfly Pieris brassicae (Lepidoptera: Pieridae)

By adopting a longitudinal study design and through geometric morphometrics methods, we investigated individual and ontogenetic variation in size, shape and timing during larval development of the cabbage butterfly Pieris brassicae under laboratory conditions. We found that ontogenetic size progression departs modestly, but significantly, from growth at a constant rate and that size at hatching contributes considerably to determine the size of the individual at all subsequent stages. As for the shape, ontogenetic allometry is much more conspicuous than static allometry, the latter in many cases being close to isometry. Analysis of developmental timing revealed a stage of apparently more effective developmental control at stage 3, supported by both the relatively small variance in cumulative developmental time up to stage 3 and by the pattern of correlation between duration of single stages. While presenting detailed quantitative aspects of growth in P. brassicae, in particular with respect to individual variation, this study and the associated dataset can provide a basis for further explorations of the post‐embryonic development in this insect and contribute to the ongoing investigations on growth regulation and control in insects.