Latitudinal trends in wood anatomy within species and genera: case study in Cornus s.l. (Cornaceae)

Latitudinal trends in wood anatomical characters in three Asiatic species of Cornus sensu lato (s.l.) were studied and compared with those for the whole genus based on an extensive sampling covering the specific distribution ranges and the generic data from a previous study. We studied 124 specimens of C. controversa growing between 31.5° and 45.3° N, 54 of C. kousa between 24.4° and 40.5° N, and 64 of C. macrophylla between 27.8° and 41.0° N. Characters studied were vessel element length, fiber length, vessel frequency, tangential vessel diameter, and vessel grouping index. At the species level no latitudinal trends were detected throughout the distribution ranges of the species. Neither tree size, altitude, nor climatic factors had a significant correlation with wood anatomical characters. In contrast, at the genus level, latitudinal trends were significant not just for the whole genus, but for both New and Old World species groups. At the genus level, latitude and three climatic factors all had a significant correlation with wood anatomical characters, but correlation coefficients with latitude were markedly high. The difference in latitudinal trends between the genus and species levels may be due to the radiation of Cornus along paleoclimatic gradients in the early Tertiary.     

Variable wood formation and adaptation to the alpine environment of Ephedra pachyclada (Gnetales: Ephedraceae) in the Mustang district, western Nepal

BACKGROUND AND AIMS: Plants of Ephedra normally have vessels, but are known to become nearly vessel-less in some alpine localities. Previous studies implied that wood formation in Ephedra differs fundamentally from that in dicotyledons in which vessel-bearing and vessel-less taxa are systematically distinct. Using E. pachyclada in the Mustang district of Nepal, growing in an altitudinal range of over 2000 m, variation in wood formation and adaptation to alpine environment was studied in this normally vessel-bearing species. METHODS: Variation in wood anatomy and wood formation was observed with conventional optical microscopy. The lengths of three kinds of tracheary elements were measured and statistically analysed against habitat altitude and plant size of the individuals studied. KEY RESULTS: In E. pachyclada three kinds of tracheary elements, vessel elements, tracheids and fibre-tracheids, were nearly equal in length within individuals showing no elongation after differentiation from cambial initials. Tracheary element lengths among individuals had a negative correlation with altitude and a positive correlation with plant size. Multivariate analyses showed that altitude has a stronger correlation with tracheary element lengths than plant height or stem diameter. Moreover, several individuals from high elevations completely lacked vessels, and vessel formation fluctuated even in individuals from lower elevations. CONCLUSIONS: Wood anatomical trends in E. pachyclada are considered as an adaptation to extremely dry conditions in high mountains. Fluctuation in vessel formation in individuals from low elevations indicated that vessels differentiate only when their lateral expansion is allowed. These results showed that E. pachyclada has a different system of wood formation from dicotyledons and supported the opinion that the wood structure of Gnetales is fundamentally different from that of angiosperms.     

Ontogenetic wood anatomy of tree and subtree species of Nepalese Rhododendron (Ericaceae) and characterization of shrub species

Ontogenetic trends in the wood structure of Nepalese Rhododendron were studied in 15 specimens of two tree and four subtree species. Average growth ring width was constant from pith to bark in spite of occurrences of extremely narrow, false, or discontinuous rings. Vessel density, vessel area, vessel element length, and multiseriate ray height generally had an initial increase or decrease to 1.5 cm radius and near plateau or slight decrease or increase outward. Multiseriate ray density and area percentage were variable between specimens without a clear pattern. Ontogenetic trends from pith to fully mature wood in trees plus subtrees were inferred by treating the measurements in the present study with those of mature individuals in a previous study. Comparison of trends in trees plus subtrees and those in shrubs lead to ecological or systematic groupings. Vessel features showed that alpine shrub species have distinctly small, numerous vessels composed of short vessel elements. Multiseriate ray features indicated a systematic difference between the trees plus subtrees of subgenus Hymenanthes and the shrubs of subgenus Rhododendron. Vessel features of alpine shrubs may be an adaptation against frequent freeze-thaw cycles or the result of growth stress imposed by the severe alpine environment.     

Latitudinal and altitudinal body size variation among north-west European land snail species

Aim To investigate latitudinal and altitudinal patterns in body size variation among north‐west European land snail species, as well as factors influencing such patterns. Location Latitudinal patterns were investigated in north‐west Europe from the British Isles and France in the west to Finland, Poland, Slovakia and Hungary in the east and from Norway in the north to France (with the exception of the Mediterranean part of the country), Switzerland, Austria and Hungary in the south. Altitudinal patterns were examined in the Alps in Austria and Switzerland. Methods Data on latitudinal ranges of 366 north‐west European land snail species, on altitudinal ranges of 175 species from Austria and 150 species from Switzerland, and on their body sizes were used to test for the presence of interspecific latitudinal or altitudinal body size patterns. Four methods, Stevens’ method, the midpoint method, the across‐species method, and a phylogenetically controlled analysis (CAIC) were applied. Results As a result of the predominance of some small bodied clades at higher latitudes and some large bodied clades at lower latitudes, body size of north‐west European land snails decreases significantly with increasing latitude. However, little of the body size variation across species is explained by latitude and the phylogenetically controlled analysis showed that the decrease of body size with increasing latitude is not a result of repeated and independent evolution of an association between body size and latitude in many clades. There is no significant correlation between body size of land snail species and altitude in the Alps although a negative correlation of body size and altitude is frequent within species. Main conclusion If phylogenetic effects are controlled for, neither latitudinal nor altitudinal patterns in body size could be found. Bergmann's rule, which predicts a positive correlation between body size of species and latitude, could not be confirmed for north‐west European land snails.     

Wood anatomy and wood density in shrubs: Responses to varying aridity along transcontinental transects

Wood density plays a key role in ecological strategies and life history variation in woody plants, but little is known about its anatomical basis in shrubs. We quantified the relationships between wood density, anatomy, and climate in 61 shrub species from eight field sites along latitudinal belts between 31° and 35° in North and South America. Measurements included cell dimensions, transverse areas of each xylem cell type and percentage contact between different cell types and vessels. Wood density was more significantly correlated with precipitation and aridity than with temperature. High wood density was achieved through reductions in cell size and increases in the proportion of wall relative to lumen. Wood density was independent of vessel traits, suggesting that this trait does not impose conduction limitations in shrubs. The proportion of fibers in direct contact with vessels decreased with and was independent of wood density, indicating that the number of fiber-vessel contacts does not explain the previously observed correlation between wood density and implosion resistance. Axial and radial parenchyma each had a significant but opposite association with wood density. Fiber size and wall thickness link wood density, life history, and ecological strategies by controlling the proportion of carbon invested per unit stem volume.     

Morphological variation in Puya (Bromeliaceae): an allometric study

A group of representative species of the genus Puya was studied to determine if there are allometric relationships between vegetative and floral parts, whether these relationships correlate with their pollination system and if plant size is correlated with elevation and latitude. Fifty-three species representing the morphological variation and distribution of the genus were studied. Total plant height, as well as leaf, inflorescence, petal and sepal length were measured and these data subjected to univariate and multivariate analyses. To test for correlation between plant size and altitudinal and latitudinal distribution, ANOVAs were performed. When the pollination system of a species is known, additional multivariate and univariate analyses were also performed. The results indicate that the characters studied are correlated with a size component, exhibiting positive allometry for sepal and petal length and negative allometry for leaf length. Inflorescence length is an isometric character. There was no significant correlation between plant size and altitudinal or latitudinal distribution. The ANOVAs show that the only character correlated to pollinator type was petal length. Small plants with small flowers are correlated to pollinators such as insects, while medium to large plants with medium to large-sized flowers are correlated with pollinators such as birds and bats. Large plants have small flowers, that are more evident and attract more pollinators.     

ECOLOGICAL FACTORS IN WOOD EVOLUTION: A FLORISTIC APPROACH

Wood florulas from southwestern Australia were analyzed to determine whether wood anatomy is sufficiently correlated with ecology so that vessel element features can be said to have a predictive value. Indices for vulnerability (vessel diam: vessels per sq. mm) and mesomorphy (vulnerability × vessel element length) were calculated for each species in the following florulas: karri forest understory, coastal granitic slopes, bogs, sand heaths, and desert. Wood indices for the species studied and for each florula show that these florulas form a sequence in increasing xeromorphy in the order listed. Genera represented in more than one florula validate the trends. Data for Gyrostemonaceae, Loranthaceae, and Cupressaceae are calculated separately because these are succulents, epiparasites, and conifers, respectively. Comparison with categories from floras elsewhere in the world shows the flora of Western Australia as a whole to be relatively xeromorphic. The indices devised show promise of great reliability because correlations with rainfall, temperature, and other factors are very close. Functional nature of the vessel element is thereby believed to be clarified.     

Ecological wood anatomy of NepaleseRhododendron (Ericaceae). 1. Interspecific variation

The relationship of selected wood anatomical characters of NepaleseRhododendron with stem diameter, plant height, altitude, and plant form was investigated. We studied one to three specimens each of 26 species: five species each of trees and subtrees I, three species of subtrees II, and 13 species of shrubs. Multiple regression analysis and actual distribution of character values show that pore characters and multiseriate ray ratio have a stronger correlation with stem diameter than altitude; that pore density, vessel element length, fiber-tracheid length, and multiseriate ray density and width are equally related to altitude and stem diameter, or to altitude and plant height; and that bar number, and multiseriate ray area and height have a stronger connection with altitude. Among the characters, average pore area is most strongly correlated with stem diameter and increases exponentially as diameter increases. For wood structure of NepaleseRhododendron, 17 to 63 % of the variation is affected by non-anatomical factors. The general trends in wood structure of NepaleseRhododendron show that trees and subtrees form one continuous unit whereas shrubs form another that often has wider ranges of variation.     

Spatial patterns of wood traits in China are controlled by phylogeny and the environment

Aim Wood properties are related to tree physiology and mechanical stability and are influenced by both phylogeny and the environment. However, it remains unclear to what extent geographical gradients in wood traits are shaped by either phylogeny or the environment. Here we aimed to disentangle the influences of phylogeny and the environment on spatial trends in wood traits. Location China. Methods We compiled a data set of 11 wood properties for 618 tree species from 98 sampling sites in China to assess their phylogenetic and spatial patterns, and to determine how many of the spatial patterns in wood properties are attributable to the environment after correction for phylogenetic influences. Result All wood traits examined exhibited significant phylogenetic signal. The widest divergence in wood traits was observed between gymnosperms and angiosperms, Rosids and Asterids, Magnoiliids and Eudicots, and in Lamiales. For most wood traits, the majority of trait variation was observed at genus and species levels. The mechanical properties of wood showed correlated evolution with wood density. Most of the mechanical properties of wood exhibited significant latitudinal variation but limited or no altitudinal variation, and were positively correlated with mean annual precipitation based on both Pearson's correlation analysis and the phylogenetic comparative method. Correlations at family level between mean annual temperature and wood density, compression strength, cross‐section hardness, modulus of elasticity and volumetric shrinkage coefficient became significant after correction for phylogenetic influences. Main conclusions Phylogeny interacted with the environment in shaping the spatial patterns of wood traits of trees across China because most wood properties showed strong phylogenetic conservatism and thus affected environmental tolerances and distributions of tree species. Mean annual precipitation was a key environmental factor explaining the spatial patterns of wood traits. Our study provides valuable insights into the geographical patterns in productivity, distribution and ecological strategy of trees linking to wood traits.     

Flight morphology along a latitudinal gradient in a butterfly: do geographic clines differ between agricultural and woodland landscapes?

Bergman and converse Bergman rules, amongst others, describe latitudinal variation in size of organisms, including flying ectotherms like butterflies. However, geographic clines in morphological traits of functional significance for flight performance and thermoregulation may also exist, although they have received less attention within a biogeographical context. Variation in flight‐related morphology has often been studied relative to landscape structure. However, the extent to which landscape effects interact with latitudinal clines of phenotypic variation has rarely been tested. Here we address the effect of latitude, landscape type and the interaction effect on body size and flight‐related morphology in the speckled wood butterfly Pararge aegeria. Male adult butterflies were collected from two replicate populations in each agricultural and woodland landscape types along a 700 km cline in six latitudinal zones. Overall size, adult body mass and wing area increased with latitude in line with Bergmann's rule. Forewing length, however, decreased with latitude. As predicted from thermoregulatory needs in ectotherms, the basal wing part was darker to the north. Latitudinal trends for flight‐related morphological traits were opposite to predictions about flight endurance under cooler conditions that were observed in some non‐lepidopteran insects, i.e. wing loading increased and wing aspect ratio decreased with latitude. Opposite trends can, however, be explained by other aspects of butterfly flight performance (i.e. mate‐location behaviour). As predicted from differences in environmental buffering in woodland landscapes along the latitudinal gradient, significant landscape×latitude interaction effects indicated stronger latitudinal clines and stronger phenotypic variation for size and flight morphology in the agricultural landscape compared to the woodland landscape. In agreement with significant interaction effects, morphological differentiation increased with latitude and was higher between population pairs of agricultural landscape than between population pairs of woodland landscape. These results demonstrate that landscape, latitude and their interaction contribute to the understanding of the complex geographic variation in P. aegeria adult phenotypes across Europe.     

Morphological variation in the Common Fiscal Lanius collaris along an altitudinal gradient in southern Africa

Geographic variation among four Common Fiscal subpopulations along an altitudinal gradient in South Africa demonstrated significant variation of 13 morphological features and 38 skeletal characters. Common Fiscals were largest in cooler, less humid, more arid areas and smallest in warmer, wetter, more humid localities, supporting Bergmann's Rule. Patterns of variation in morphology, anatomy and skeletal trends were significantly correlated with 11 climatic trends. Cardiopulmonary organ mass and blood haematocrit increased with altitude and reflected adaptations to low ambient temperatures and decreased oxygen pressures associated with high altitudes. These trends are concordant with those reported in various other avian species.     

Distribution and abundance of butterflies in a mountain area in the northern Iberian peninsula

The effect of alutudinal range, distance to the latitudinal boundary of geographical range, body size and larval food plant on both the distribution and abundance of butterflies have been studied in a mountain area along a marked altitudinal gradient Multiple regression analysis revealed that distribution was positively related to altitudinal range and abundance Altitudinal range accounted for a great part of vanance in species distribution Altitudinal range increased as both distance to latitudinal boundary of geographical range and body size increased Abundance was not affected by altitudinal range, body size or distance to latitudinal boundary Larval food plants family was related to the abundance of butterflies, but not to distribution or altitudinal range These results suggest that regional distributions of butterflies are likely to be limited by climatic tolerances of species, while local abundance might be influenced by local resource levels     

Wood anatomy of Phragmotheca (Bombacaceae)

The wood anatomy ofPhragmotheca (Bombacaceae) is described based on three species and three specimens. The wood features ofPhragmotheca, Matisia, andQuararibea are very similar and differ only in the size of the intervascular pits and vessel diameters. Based on wood anatomical characteristics, these three genera form a distinct and homogeneous group within both the tribe Quararibeae and the family Bombacaceae.     

Chloroplast DNA variation in the Quercus affinis-Q. laurina complex in Mexico: geographical structure and associations with nuclear and morphological variation

The geographical distribution of chloroplast DNA (cpDNA) variation in 39 populations of two hybridizing Mexican red oaks, Quercus affinis and Q. laurina, was investigated using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Six haplotypes were identified. Of these, two (H1 and H4), separated by four mutations, had high frequencies (58 and 23% of the individuals, respectively) and were present across the whole geographical range of both species, often co occurring in the same populations. The other four haplotypes were rare, geographically restricted, and are probably derived from the two frequent haplotypes. Latitudinal or other clinal patterns in diversity levels or haplotype composition of populations were not apparent. The pattern of haplotype distribution was characterized by some mosaicism, with contrasting populations often situated in proximity. Average within-population diversity (hS=0.299) and population differentiation (GST=0.499) were, respectively, higher and lower than values reported in previous studies of oak species. There was evidence for phylogeographical structure, as indicated by NST (0.566) being significantly higher than GST. Haplotypic variation was largely species-independent, although some very weak associations were detected between haplotypes H1 and H4 and morphological and nuclear molecular variation correspondingly characterizing Q. affinis and Q. laurina. These oaks probably did not experience a marked restriction to one or a few particular subregions of their present range during the last glacial cycle. It is more likely that substantial populations persisted throughout several episodes of climatic change, but experienced recurrent latitudinal and altitudinal migrations which may have caused the widespread distribution of haplotypes H1 and H4 and frequent intermixing of populations.     

Heterochrony: The evolution of ontogeny. By Michael L. McKinney and Kenneth J. McNamara. New York: Plenum Press. 1991. XIX + 437 pp. ISBN 0-306-43638-8. $ 49.50 (cloth)

Macaca fascicularis is broadly distributed in Southeast Asia across 30° of latitude and 35° of longitude (Indochinese Peninsula, Isthmus of Kra, Malay Peninsula, Greater and Lesser Sunda Islands, Philippine Islands, and numerous small, neighboring islands). The range is divisible into 1) a core area comprised of mainland Southeast Asia, Borneo, Sumatra, and Java (large land masses interconnected during the last glacial maximum, 18,000 B. P.); 2) shallow-water fringing islands, which are smaller islands connected to the core area during the last glacial maximum; and 3) deep-water fringing islands, which are peripheral islands not connected to the core area during the last glacial maximum. Skull length was used to study effects of latitude and insularity on patterns of size variation. The data are from 802 adult M. fascicularis specimens from 140 core-area localities, 63 shallow-water islands, and 29 deep-water islands. Sex-specific polynomial regressions of skull length on latitude were used to describe skull length variation in the core area. These regressions served as standards for evaluating variation among samples from shallow-water and deep-water islands. The core area exhibits Bergmannian latitudinal size clines through most of the species range. Thus, skull length decreases from about 8°S (Java) to the equator (Sumatra and Borneo), then increases as far north as about 13°N (Isthmus of Kra). Farther north, to the northernmost Indochinese localities at about 17°N, skull length in M. fascicularis decreases with increasing latitude, contrary to Bergmann's rule. Latitudinal size variation in shallow-water fringing islands generally parallels that in the core area. However, skull length tends to be smaller than in the core area at similar latitudes. Deep-water fringing islands are markedly more variable, with relatively small specimens in the Lesser Sunda Islands and relatively large specimens in the Nicobar Islands. These analyses illustrate how a primate species may vary in response to latitudinal temperature variation and to isolation. © 1993 Wiley-Liss, Inc.     

四种番荔枝科(Annonaceae)植物导管分子及其穿孔板的比较观察

番荔枝科是被子植物基部类群,木兰目中最大的一个科。为了解暗罗属(Polyalthia)的海南暗罗(Polyalthia laui)、假鹰爪属(Desmos)的假鹰爪(Desmos chinensis)、紫玉盘属(Uvaria)的山椒子(Uvaria grandiflora)、瓜馥木属Fissistigma)的瓜馥木(Fissistigma oldhamii)四个种的导管与穿孔板的形态学特征,该研究利用扫描电子显微镜(SEM)对其导管分子及穿孔板形态进行观察,首次展示了这4属4种的导管分子与穿孔板的形态特征,并对其导管的长度与直径进行了分析与比较。结果表明:这四个种导管分子端壁均为单穿孔板,部分穿孔板具尾,不同种在导管与穿孔板形态上具有明显的差异;长度与直径的统计学分析显示其种间差异极显著,导管长度与直径的相关性分析显示其没有相关性。综合导管的形态学特征与统计学分析结果,该研究认为在这四个种中,假鹰爪的导管分子直径与长度变化幅度都不大,长度较短,直径最大,穿孔板平截,不具尾或具小尾,其导管分子处于较高的演化水平。     

Wood anatomical traits as a measure of plant responses to water availability: invasive Acacia mearnsii De Wild. compared with native tree species in fynbos riparian ecotones, South Africa

Riparian ecotones in the fynbos biome of South Africa are heavily invaded by woody invasive alien species, which are known to reduce water supply to downstream environments. To explore whether variation in species-specific functional traits pertaining to drought-tolerance exist, we investigated wood anatomical traits of key native riparian species and the invasive Acacia mearnsii across different water availability proxies. Wood density, vessel resistance against implosion, vessel lumen diameter and vessel wall thickness were measured. Wood density varied significantly between species, with A. mearnsii having denser wood at sites in rivers with high discharge. As higher wood density is indicative of increased drought tolerance and typical of drier sites, this counter-intuitive finding suggests that increased wood density was more closely related to midday water stress, than streamflow quantity per se. Wood density was positively correlated with vessel resistance against implosion. Higher wood density may also be evidence that A. mearnsii is more resistant against drought-induced cavitation than the studied native species. The observed plastic response of A. mearnsii anatomical traits to variable water availability indicates the ability of this species to persist under various environmental conditions. A possible non-causal relationship between wood anatomy and drought tolerance in these riparian systems is discussed.     

Ecological wood anatomy of NepaleseRhododendron (Ericaceae). 2. Intraspecific variation

The intraspecific relationship of selected wood anatomical characters with stem diameter, plant height, and altitude was investigated in four NepaleseRhododendron species:R. anthopogon, R. lepidotum, R. campanulatum, andR. arboreum, i.e., two shrubs, one subtree, and one tree. We studied 23 to 27 specimens for each species.R. anthopogon grew from 3,380 to 4,950 m,R. lepidotum from 2,060 to 4,720 m,R. campanulatum from 2,790 to 4,140 m, andR. arboreum from 1,430 to 3,460 m. Multiple regression analysis and actual distribution of character values show that the wood anatomical characters having a significant correlation with non-anatomical factors differ between species. The number of significant characters are two inR. anthopogon andR. campanulatum, five inR. lepidotum, and nine inR. arboreum and tends to be small in species having smaller altitudinal ranges. Average pore area, most strongly correlated with non-anatomical factors in interspecific variation, is significantly correlated only inR. lepidotum andR. arboreum. The general trends in intraspecific variation among four NepaleseRhododendron species differ from the trends found in interspecific variation within the genus and are characteristic of each species.     

Latitudinal and altitudinal diversity patterns and Rapoport effects in north-west European land snails and their causes

The latitudinal and altitudinal range sizes of north-west European land-snail species increase with increasing latitude/altitude. These Rapoport effects are not caused by northern/high-altitude species with wider latitudinal/altitudinal ranges and southern/low-altitude species with narrower latitudinal/altitudinal ranges, as predicted by the climatic variability hypothesis. They are instead caused mainly by different northern/upper borders of species occurring in the south part of the study area or at low and intermediate altitudes, respectively. This pattern indicates that the observed Rapoport effects are the result mainly of differential northward/upward expansion of species that were restricted to southern/low or intermediate altitude refugia during the glacials. Although all species occurring in a refugium experienced the same climatic conditions, there is stochastic variation in their climatic tolerance. Species with broader climatic tolerance were able to expand farer northwards/upwards postglacial. The altitudinal distribution of species richness in the analysed alpine faunas cannot be explained by the Rapoport-rescue hypothesis, because species richness peaks at intermediate altitudes and because there is no negative correlation between the number of range borders and altitude. The Rapoport-rescue hypothesis alone is probably also insufficient to explain the decrease in species richness with increasing latitude.  © 2006 The Linnean Society of London, Biological Journal of the Linnean Society , 2006, 87 , 309–323.     

Marine invertebrate skeleton size varies with latitude,temperature and carbonate saturation: implications for global change and ocean acidification

There is great concern over the future effects of ocean acidification on marine organisms, especially for skeletal calcification, yet little is known of natural variation in skeleton size and composition across the globe, and this is a prerequisite for identifying factors currently controlling skeleton mass and thickness. Here, taxonomically controlled latitudinal variations in shell morphology and composition were investigated in bivalve and gastropod molluscs, brachiopods, and echinoids. Total inorganic content, a proxy for skeletal CaCO₃, decreased with latitude, decreasing seawater temperature, and decreasing seawater carbonate saturation state (for CaCO₃ as calcite (Ω_cal)) in all taxa. Shell mass decreased with latitude in molluscs and shell inorganic content decreased with latitude in buccinid gastropods. Shell thickness decreased with latitude in buccinid gastropods (excepting the Australian temperate buccinid) and echinoids, but not brachiopods and laternulid clams. In the latter, the polar species had the thickest shell. There was no latitudinal trend in shell thickness within brachiopods. The variation in trends in shell thickness by taxon suggests that in some circumstances ecological factors may override latitudinal trends. Latitudinal gradients may produce effects similar to those of future CO₂‐driven ocean acidification on CaCO₃ saturation state. Responses to latitudinal trends in temperature and saturation state may therefore be useful in informing predictions of organism responses to ocean acidification over long‐term adaptive timescales.