Variation In Coloration Research Articles

Signal honesty and predation risk among a closely related group of aposematic species.

Many animals have bright colours to warn predators that they have defences and are not worth attacking. However, it remains unclear whether the strength of warning colours reliably indicate levels of defence. Few studies have unambiguously established if warning signals are honest, and have rarely considered predator vision or conspicuousness against the background. Importantly, little data exists either on how differences in signal strength translate into survival advantages. Ladybirds exhibit impressive variation in coloration both among and within species. Here we demonstrate that different levels of toxicity exist among and within ladybird species, and that signal contrast against the background is a good predictor of toxicity, showing that the colours are honest signals. Furthermore, field experiments with ladybird models created with regards to predator vision show that models with lower conspicuousness were attacked more frequently. This provides one of the most comprehensive studies on signal honesty in warning coloration to date.

Nonadaptive radiation in damselflies.

Adaptive radiations have long served as living libraries to study the build-up of species richness; however, they do not provide good models for radiations that exhibit negligible adaptive disparity. Here, we review work on damselflies to argue that nonadaptive mechanisms were predominant in the radiation of this group and have driven species divergence through sexual selection arising from male-female mating interactions. Three damselfly genera (Calopteryx,Enallagma and Ischnura) are highlighted and the extent of (i) adaptive ecological divergence in niche use and (ii) nonadaptive differentiation in characters associated with reproduction (e.g. sexual morphology and behaviours) was evaluated. We demonstrate that species diversification in the genus Calopteryx is caused by nonadaptive divergence in coloration and behaviour affecting premating isolation, and structural differentiation in reproductive morphology affecting postmating isolation. Similarly, the vast majority of diversification events in the sister genera Enallagma and Ischnura are entirely driven by differentiation in genital structures used in species recognition. The finding that closely related species can show negligible ecological differences yet are completely reproductively isolated suggests that the evolution of reproductive isolation can be uncoupled from niche-based divergent natural selection, challenging traditional niche models of species coexistence.

Phylogeography and support vector machine classification of colour variation in panther chameleons.

Lizards and snakes exhibit colour variation of adaptive value for thermoregulation, camouflage, predator avoidance, sexual selection and speciation. Furcifer pardalis, the panther chameleon, is one of the most spectacular reptilian endemic species in Madagascar, with pronounced sexual dimorphism and exceptionally large intraspecific variation in male coloration. We perform here an integrative analysis of molecular phylogeography and colour variation after collecting high‐resolution colour photographs and blood samples from 324 F. pardalis individuals in locations spanning the whole species distribution. First, mitochondrial and nuclear DNA sequence analyses uncover strong genetic structure among geographically restricted haplogroups, revealing limited gene flow among populations. Bayesian coalescent modelling suggests that most of the mitochondrial haplogroups could be considered as separate species. Second, using a supervised multiclass support vector machine approach on five anatomical components, we identify patterns in 3D colour space that efficiently predict assignment of male individuals to mitochondrial haplogroups. We converted the results of this analysis into a simple visual classification key that can assist trade managers to avoid local population overharvesting.

An integrative taxonomic review of the agamid genus Bronchocela (Kuhl, 1820) from Peninsular Malaysia with descriptions of new montane and insular endemics

An integrative taxonomic analysis is used to identify and describe two new species of the agamid genus Bronchocela (Kuhl) from Peninsular Malaysia: an upland species B. shenlong sp. nov. from Bukit Larut, Perak in the Bintang Mountain Range and Parit Falls, Cameron Highlands, Pahang in the Titiwangsa Mountain Range and an insular species, B. rayaensis sp. nov., from Pulau Langkawi, Kedah off the northwest coast on the border with Thailand. Both species are diagnosed from each other and all other species of Bronchocela on the basis of body shape, scale morphology, and color pattern. The analysis also demonstrates the remarkable genetic similarity of B. cristatella (Kuhl) throughout 1120 km of its range from northern Peninsular Malaysia to western Borneo despite its highly variable coloration and pattern. The two new species are appended to a rapidly growing list of newly described lizard species (60 to date) from Peninsular Malaysia tallied within the last decade.

Mapping the cause-specific premature mortality reveals large between-districts disparity in Belgium, 2003-2009.

BackgroundReducing premature mortality is a crucial public health objective. The goal of this paper, beside updating previous mortality atlases with recent data, is to explore the relative between-districts disparity using a relative-scale map design.MethodsCauses of deaths and population data were provided by Statistics Belgium. All deaths occurring in the periods 1993–1999 and 2003–2009, in people aged 1–74 residing in Belgium were included. Age-adjusted rates by cause of death were computed for both periods; the 2003-2009 rates were classified using a relative scale with a 10% change between each level and represented on chloropleths maps with a green-to-red divergent colour scheme centred on the national mean. This particular design allows the comparability across all the maps since a same meaning is given to a specific colour. The variation coefficient and the decile ratio were calculated and compared between the 2 periods.ResultsA clear-cut regional divide at the disadvantage of Wallonia, and to some extent, of Brussels, was seen for all-cause, cardiovascular, cerebrovascular, diabetes, alcohol-related, mental and neurological diseases and non-transport accidents premature mortality. A NE-SW pattern parallel to the French border was observed for Lip, Oral Cavity, Pharynx, Larynx and oesophageal cancers, while various patterns are observed for the other cancers. The highest rates of road accident mortality are observed in the Southern districts. Many of those patterns are in continuity with earlier observations. However, the pattern of diabetes and mental and neurological diseases are new features. The variation coefficient and the decile ratios increased by 10% between the 1993-1997 and 2003-2009 periods.ConclusionsThe use of a relative scale in the maps highlights the importance of the between-districts disparity in premature mortality, with for most causes, a clear-cut regional divide at the disadvantage of Wallonia; this health gap results of complex interactions between various factors, including the socioeconomic context, cultural habits and environmental influences, as well as public health policies. It should be considered as a warning signal, warranting the attention of the policy makers. Meanwhile, these results also highlight the potential for improvement in the more disadvantaged regions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13690-015-0060-5) contains supplementary material, which is available to authorized users.

RESISTANCE TO CHILLING INJURY IN RED, LYCOPENE-ACCUMULATING TISSUE OF COLD-STORED GRAPEFRUITS

Grapefruits are widely recognized by their extreme sensitivity to develop chilling injury (CI) during postharvest storage at low temperature. Moreover, many cultivars and mutants of grapefruits exhibit important differences in both external and internal coloration, from yellow to deep red, due to a distinctive accumulation of the red carotene lycopene. Thus, in this study the genetic variability in external peel coloration of grapefruits has been used to examine the potential relationship between carotenoid content and composition, and susceptibility to CI. CI increased progressively after 2 weeks storage at 2°C in fruit of the yellow grapefruit ‘Marsh’ (M) but in the fruits of red cultivar ‘Star Ruby’ (SR) CI symptoms were exclusively restricted to the yellow areas of the peel. Thus, CI was absent in red peel tissue, even after prolonged cold storage, in which lycopene content was about 14-times higher than in yellow tissue. In addition, SR grapefruits growing under shaded conditions developed an intense external red coloration and accumulated large amount of lycopene, and were also highly resistant to CI upon subsequent postharvest cold storage. To further explore the mechanisms involved in the resistance to CI induced by lycopene, total antioxidant activity was determined in yellow and red peel tissue of grapefruit, and the potential relationship between carotenoids and the development of CI is discussed.

A review of the genus Selasia (Elateridae: Agrypninae: Drilini) in the Palaearctic Region.

The six species of the soft-bodied elaterid genus Selasia Laporte (Agrypninae: Drilini) from the Palaearctic Region are reviewed: S. arabica Geisthardt, 2003 (Yemen, Oman, The Kingdom of Saudi Arabia), S. atriventris Pic, 1914 (India, Nepal), S. boruckae Kundrata, 2012 (Nepal), S. homhilia Geisthardt, 2003 (Yemen: Socotra), S. merkli Kundrata, 2012 (Pakistan), and S. socotrana Kundrata, 2012 (Yemen: Socotra). Selasia arabica and S. atriventris are recorded for the first time from Oman and Nepal, respectively. The variability in coloration of S. arabica is discussed. Selasia bleusei Olivier, 1913 from Rhodes is redescribed and transferred to Drilus Olivier, 1790 as D. bleusei (Olivier, 1913), comb. nov. A differential diagnosis is given and taxonomically important characters are figured. An identification key as well as data on the distributions, type depositories and bibliographic references of each Palaearctic Selasia species are provided.

Selective removal of demineralized enamel using a CO2 laser coupled with near-IR reflectance imaging.

Detection and diagnosis of early dental caries lesions can be difficult due to variable tooth coloration, staining of the teeth and poor contrast between sound and demineralized enamel. These problems can be overcome by using near-infrared (NIR) imaging. Previous studies have demonstrated that lasers can be integrated with NIR imaging devices, allowing image-guided ablation. The aim of this study was to demonstrate that NIR light at 1500 - 1700 nm can be used to guide a 9.3-μm CO2 laser for the selective ablation of early demineralization on tooth occlusal surfaces. The occlusal surfaces of ten sound human molars were used in this in-vitro study. Shallow simulated caries lesions of varying depth and position were produced on tooth occlusal surfaces using a demineralization solution. Sequential NIR reflectance images at 1500 - 1700 nm were used to guide the laser for selective ablation of the lesion areas. Digital microscopy and polarization sensitive optical coherence tomography (PS-OCT) were used to assess the selectivity of removal. This study demonstrates that high contrast NIR reflectance images can be used for the image-guided laser ablation of early demineralization from tooth occlusal surfaces.

Understanding the relationships between structural features and optical/magnetic properties when designing Fe(1-x)Mg(x)MoO4 as piezochromic compounds.

Fe1-xMgxMoO4 compounds with x = 0, 0.25, 0.5, 0.75, and 1.0 were obtained after annealing under inert gas at T = 700 °C. All of the compounds exhibit a pressure-induced and/or temperature-induced phase transition between the two polymorphs adopted by AMoO4 compounds (A = Mn, Fe, Co, and Ni). For the FeMoO4 compound, for both the α and the β allotropic forms, the structural features have been correlated to the magnetic properties, the Mössbauer signals, and the optical absorption properties to gain a better understanding of the phenomena at the origin of the piezo(thermo)chromic behavior. The different contributions of the Mössbauer signals were attributed to the different Fe(2+) ions or Fe(3+) ions from the structural data (Wyckoff positions, bond distances and angles) and were quantified. Furthermore, the low Fe(3+) concentration (9 and 4 mol %, respectively, in the α and the β allotropic forms) was also quantified based on the magnetic susceptibility measurements. The net increase in the Fe(3+) quantity in the α-form in comparison to the β-form, which is associated with the occurrence of Fe-Mo charge transfer, is at the origin of the important divergence of coloration of the two forms. To design new piezo(thermo)chromic oxides and to control the pressure (temperature) of this first-order phase transition, FeMoO4-MgMoO4 solid solutions were synthesized. The optical contrast between the two allotropic forms was increased due to magnesium incorporation, and the phase transition (β → α) pressure increased steadily with the Mg content. A new generation of nontoxic and chemically stable piezochromic compounds that are sensible to various pressures was proposed.

Larval melanism in a geometrid moth: promoted neither by a thermal nor seasonal adaptation but desiccating environments.

Spatiotemporal variation in the degree of melanism is often considered in the context of thermal adaptation, melanism being advantageous under suboptimal thermal conditions. Yet, other mutually nonexclusive explanations exist. Analysis of geographical patterns combined with laboratory experiments on the mechanisms of morph induction helps to unveil the adaptive value of particular cases of polyphenism. In the context of the thermal melanism hypothesis and seasonal adaptations, we explored an array of environmental factors that may affect the expression and performance of nonmelanic vs. melanic larval morphs in different latitudinal populations of the facultatively bivoltine moth Chiasmia clathrata (Lepidoptera: Geometridae). Geographical variation in larval coloration was independent of average temperatures experienced by the populations in the wild. The melanic morph was, however, more abundant in dry than in mesic habitats. In the laboratory, the melanic morph was induced especially under a high level of incident radiation but also at relatively high temperatures, but independently of photoperiod. Melanic larvae had higher growth rates and shorter development times than the nonmelanic ones when both temperature and the level of incident radiation were high. Our results that melanism is induced and advantageous in warm desiccating conditions contradict the thermal melanism hypothesis for this species. Neither has melanism evolved to compensate time constraints due to forthcoming autumn. Instead, larvae solve seasonal variation in the time available for growth by an elevated growth rate and a shortened larval period in the face of autumnal photoperiods. The phenotypic response to the level of incident radiation and a lack of adaptive adjustment of larval growth trajectories in univoltine populations underpin the role of deterministic environmental variation in the evolution of irreversible adaptive plasticity and seasonal polyphenism.

Fecundity selection does not vary along a large geographical cline of trait means in a passerine bird

Local environmental and ecological conditions are commonly expected to result in local adaptation, although there are few examples of variation in phenotypic selection across continent-wide spatial scales. We collected standardized data on selection with respect to the highly variable plumage coloration of pied flycatcher (Ficedula hypoleucaPall.) males from 17 populations across the species' breeding range. The observed selection on multiple male coloration traits via the annual number of fledged young was generally relatively weak. The main aim of the present study, however, was to examine whether the current directional selection estimates are associated with distance to the sympatric area with the collared flycatcher (Ficedula albicollisTemminck), a sister species with which the pied flycatcher is showing character displacement. This pattern was expected because plumage traits in male pied flycatchers are changing with the distance to these areas of sympatry. However, we did not find such a pattern in current selection on coloration. There were no associations between current directional selection on ornamentation and latitude or longitude either. Interestingly, current selection on coloration traits was not associated with the observed mean plumage traits of the populations. Thus, there do not appear to be geographical gradients in current directional fecundity selection on male plumage ornamentation. The results of the present study do not support the idea that constant patterns in directional fecundity selection would play a major role in the maintenance of coloration among populations in this species. By contrast, the tendency for relatively weak mosaic-like variation in selection among populations could reflect just a snapshot of temporally variable, potentially environment-dependent, selection, as suggested by other studies in this system. Such fine-grained variable selection coupled with gene flow could maintain extensive phenotypic variation across populations.(c) 2015 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114, 808-827.

Quantitative color variation within and across morphs of the polymorphic White-throated Sparrow

ABSTRACT Coloration has evolved to serve diverse functions, including communication. In species with discrete color polymorphisms, the extent to which color variation exists within morphs and communicates multiple messages often remains unclear. We employed reflectance spectrometry to study variation in coloration in the dimorphic White-throated Sparrow (Zonotrichia albicollis), which exhibits a “white” and “tan” morph in both sexes. We explored whether distinct color traits distinguish between morph and sex classes, and whether color variation exists within classes that might reflect differences in individual quality. Further, we asked whether sexual dichromatism is more pronounced in the white morph, in which males display greater promiscuity and aggression and, thus, may be under stronger sexual selection for conspicuous coloration. Distinct aspects of crown plumage coloration differentiated the two morphs versus the two sexes and multiple types of coloration were associated with a morph, suggesting bo...

Carotenoid-based bill coloration functions as a social, not sexual, signal in songbirds (Aves: Passeriformes).

Many animals use coloration to communicate with other individuals. Although the signalling role of avian plumage colour is relatively well studied, there has been much less research on coloration in avian bare parts. However, bare parts could be highly informative signals as they can show rapid changes in coloration. We measured bill colour (a ubiquitous bare part) in over 1600 passerine species and tested whether interspecific variation in carotenoid-based coloration is consistent with signalling to potential mates or signalling to potential rivals in a competitive context. Our results suggest that carotenoid bill coloration primarily evolved as a signal of dominance, as this type of coloration is more common in species that live in social groups in the nonbreeding season, and species that nest in colonies; two socio-ecological conditions that promote frequent agonistic interactions with numerous and/or unfamiliar individuals. Additionally, our study suggests that carotenoid bill coloration is independent of the intensity of past sexual selection, as it is not related to either sexual dichromatism or sexual size dimorphism. These results pose a significant challenge to the conventional view that carotenoid-based avian coloration has evolved as a developmentally costly, condition-dependent sexual signal. We also suggest that bare part ornamentation may often signal different information than plumage ornaments.

The genus Chironius (Serpentes, Colubridae) in Paraguay: composition, distribution, and morphology

Chironius is a genus of slender snakes adapted to a diurnal and arboreal life style, and is distributed from Honduras to Uruguay inhabiting different environments. Five species are present in Paraguay: C. bicarinatus, C. exoletus, C. flavolineatus, C. maculoventris, and C. quadricarinatus. In this work, we provide data on distribution, coloration, and morphological variation of 20 Paraguayan specimens housed in scientific collections. Our results fit with known parameters for the species referred in literature. A conclusion of this work is that, based on distribution and ecological preferences of the species in the region, Paraguay is poorly sampled. Here we extend the known pholidosis range of ventral scale for females of C. bicarinatus (154-170), and for C. maculoventris (143-157 for females and 154-161 for males), and the range of subcaudal scales for males of C. maculoventris (90-125), and females of C. quadricarinatus (91-123).

The paradox of the Birds-of-Paradise: persistent hybridization as a signature of historical reinforcement

The birds-of-paradise (Paradisaeidae) exhibit some of the most diverse color patterns and courtship displays among species. Paradoxically, birds-of-paradise hybridize more frequently than other birds, even hybridizing across species and genera with remarkably divergent color patterns. Hybridization among such distinctly colored species might suggest that reinforcement was unimportant for color pattern divergence because reinforcement favors trait divergence that reduces the likelihood of hybridization over time, and is expected to eliminate hybridization between species. Here I present an alternative view: that persistent but infrequent hybridization among species that differ markedly in prezygotic isolating traits, such as color pattern in birds, represents the signature of historical reinforcement, and occurs when (i) divergence in single traits can reduce, but not prevent, hybridization, (ii) trade-offs constrain the divergence of prezygotic isolating traits, and (iii) selection against hybrids is weak when hybrids are rare. Considering these factors, the paradox of the birds-of-paradise—where species with distinct prezygotic isolating traits are more likely to hybridize at low frequencies—is the expected outcome of reinforcement. Sexual selection by female choice could further intensify the effects of reinforcement, particularly if reinforcement directs sexual selection to different traits in hybridizing populations. This latter process could potentially explain the exceptional diversity of extravagant ornaments in the birds-of-paradise.

Genetic basis and fitness correlates of dynamic carotenoid-based ornamental coloration in male and female common kestrels Falco tinnunculus.

Knowledge of the genetic basis of sexual ornaments is essential to understand their evolution through sexual selection. Although carotenoid-based ornaments have been instrumental in the study of sexual selection, given the inability of animals to synthesize carotenoids de novo, they are generally assumed to be influenced solely by environmental variation. However, very few studies have directly estimated the role of genes and the environment in shaping variation in carotenoid-based traits. Using long-term individual-based data, we here explore the evolutionary potential of a dynamic, carotenoid-based ornament (namely skin coloration), in male and female common kestrels. We first estimate the amount of genetic variation underlying variation in hue, chroma and brightness. After correcting for sex differences, the chroma of the orange-yellow eye ring coloration was significantly heritable (h2±SE=0.40±0.17), whereas neither hue (h2=0) nor brightness (h2=0.02) was heritable. Second, we estimate the strength and shape of selection acting upon chromatic (hue and chroma) and achromatic (brightness) variation and show positive and negative directional selection on female but not male chroma and hue, respectively, whereas brightness was unrelated to fitness in both sexes. This suggests that different components of carotenoid-based signals traits may show different evolutionary dynamics. Overall, we show that carotenoid-based coloration is a complex and multifaceted trait. If we are to gain a better understanding of the processes responsible for the generation and maintenance of variation in carotenoid-based coloration, these complexities need to be taken into account.

Coloration of the testicular peritoneal sheath as a synapomorphy of triatomines (Hemiptera, Reduviidae)

Recently, were described some morphological characteristics of 18 species of terrestrial hemipteran grouped in the Alydidae, Coreidae, Corimelaenidae, Lygaeidae, Rhopalidae, Scutelleridae, Tingidae and Reduviidae family that presented found variation in coloration of testicular peritoneal sheath (Reddish, Orange, Yellowish or Transparent). Thus, this study aims to analyzed the coloration of the peritoneal sheath in 44 species of triatomines grouped in nine different genera, with the aim of analyze whether the insects of the Triatominae subfamily also show variations in coloration. By means of analysis of the sheath was possible to observe that members of this subfamily have no interspecific differences, because all species have a transparent sheath. Thus, this paper describes the coloring of the peritoneal sheath in 44 species of the subfamily Triatominae and mainly suggests that the transparent color is one synapomorphy of this important group of insect vectors.

A Preliminary Assessment of Sifaka (Propithecus) Distribution, Chromatic Variation and Conservation in Western Central Madagascar

To help inform conservation efforts for the Endangered crowned sifaka Propithecus coronatus, in 2010, we attempted to better define the known distribution of sifakas in western central Madagascar through field surveys of 17 sites we considered likely to fall in or close to the historic range of P. coronatus. We observed P. coronatus at seven sites, in the Boeny, Betsiboka and Bongolava regions. At three sites at the intersection of the regions of Bongolava, Melaky and Menabe we observed populations containing sifaka of P. deckenii appearance mixed with melanistic individuals. We observed P. verreauxi at the two most southerly sites, in the Amoron'i Mania Region, and P. coquereli at one north-easterly site in the Betsiboka Region, a southern extension of 90 km to the known range of the species. At the four remaining sites, sifaka appeared to be either absent or extinct. We observed two other lemur species, Eulemur mongoz in the Boeny Region, and E. rufus in the Betsiboka Region, the latter observation being a small extension to the species' known range. We noted variation in pelage coloration amongst the P. coronatus individuals we observed, mainly regarding the extent and tone of the rufous wash on the back, arms and legs, but also in the color of the head, and the presence or absence of dark patches on the nape or at the root of the tail. The melanistic forms of P. deckenii varied greatly, some being very dark brown on large areas of the head, back, arms and legs, and appearing unlike any typical sifaka species, others exhibiting an intermediate coloration fairly similar to P. coronatus. We therefore suggest that P. coronatus should not be considered to represent an extreme melanistic form of P. deckenii, and that most previous reports of possible sympatry between the two taxa might alternatively be explained by a melanistic tendency in P. deckenii, possibly arising from occasional gene flow from P. coronatus. Our results show that P. coronatus may now be considered widely distributed through western central Madagascar, but most forests in this area are small and fragmented, and sifaka populations are highly endangered. We therefore recommend the implementation of immediate conservation interventions to ensure the maintenance of the full range of chromatic and genetic diversity of P. coronatus.

Marked colour divergence in the gliding membranes of a tropical lizard mirrors population differences in the colour of falling leaves.

Populations of the Bornean gliding lizard, Draco cornutus, differ markedly in the colour of their gliding membranes. They also differ in local vegetation type (mangrove forest versus lowland rainforest) and consequently, the colour of falling leaves (red and brown/black in mangrove versus green, brown and black in rainforest). We show that the gliding membranes of these lizards closely match the colours of freshly fallen leaves in the local habitat as they appear to the visual system of birds (their probable predators). Furthermore, gliding membranes more closely resembled colours of local fallen leaves than standing foliage or fallen leaves in the other population's habitat. This suggests that the two populations have diverged in gliding membrane coloration to match the colours of their local falling leaves, and that mimicking falling leaves is an adaptation that functions to reduce predation by birds.

A Malus crabapple chalcone synthase gene, McCHS, regulates red petal color and flavonoid biosynthesis.

Chalcone synthase is a key and often rate-limiting enzyme in the biosynthesis of anthocyanin pigments that accumulate in plant organs such as flowers and fruits, but the relationship between CHS expression and the petal coloration level in different cultivars is still unclear. In this study, three typical crabapple cultivars were chosen based on different petal colors and coloration patterns. The two extreme color cultivars, ‘Royalty’ and ‘Flame’, have dark red and white petals respectively, while the intermediate cultivar ‘Radiant’ has pink petals. We detected the flavoniods accumulation and the expression levels of McCHS during petals expansion process in different cultivars. The results showed McCHS have their special expression patterns in each tested cultivars, and is responsible for the red coloration and color variation in crabapple petals, especially for color fade process in ‘Radiant’. Furthermore, tobacco plants constitutively expressing McCHS displayed a higher anthocyanins accumulation and a deeper red petal color compared with control untransformed lines. Moreover, the expression levels of several anthocyanin biosynthetic genes were higher in the transgenic McCHS overexpressing tobacco lines than in the control plants. A close relationship was observed between the expression of McCHS and the transcription factors McMYB4 and McMYB5 during petals development in different crabapple cultivars, suggesting that the expression of McCHS was regulated by these transcription factors. We conclude that the endogenous McCHS gene is a critical factor in the regulation of anthocyanin biosynthesis during petal coloration in Malus crabapple.