Late Pleistocene lineage divergence among populations of Neolitsea sericea (Lauraceae) across a deep sea‐barrier in the Ryukyu Islands

Aim Our goals were: (1) to assess the population genetic structure and demographic divergence history of a bird‐dispersed tree, Neolitsea sericea, endemic to East Asian land‐bridge islands; and (2) to interpret the results in the light of controversies over the dating and configurations of land bridges through the Japanese Ryukyu Island Arc. Location Japan–Ryukyu–Taiwan Island Arc and Chinese/Korean offshore islands. Methods We applied 10 nuclear microsatellites (nSSRs) and one chloroplast (cp) DNA sequence marker (psbA–trnH intergenic spacer) to 31 populations (397 and 326 individuals, respectively) from throughout the species’ range to infer current patterns of genetic diversity and structure, and pollen‐to‐seed migration ratios (r). A coalescent‐based isolation‐with‐migration (IM) model was applied to the combined nSSR/cpDNA data set to estimate lineage divergence times and population demographic parameters. Results The geographic structure of nSSRs and the distribution of most cpDNA haplotypes revealed two distinct lineages located in areas north and south of the ‘Tokara Gap’, a narrow (c. 37 km wide) but deep (> 1000 m) sea‐strait between the northern and central Ryukyus. Based on the IM analyses, we (1) dated the divergence of these northern and southern lineages to c. 0.07 Ma (90% highest posterior density interval: 0.02–0.38 Ma); (2) estimated a slightly smaller effective population size for the northern compared to the southern lineage; and (3) recovered only trivial signals of post‐divergence gene flow between them. Main conclusions The estimated divergence time for northern and southern lineages is consistent with geological evidence for the existence of land connections in the Tokara region during cold stages of the latest Pleistocene; it is thus incompatible with an ‘ancient sea‐barrier hypothesis’ for the Ryukyu Arc, where we would have expected much older divergences related to the initial formation of the Tokara and Kerama tectonic straits during the Pliocene. Multiple factors are likely to have had a role in the divergence of N. sericea, including not only land‐bridge submergence, but also island configuration, and/or constraints on adaptation along a latitudinal temperature gradient.     

Habitat filtering drives the local distribution of congeneric species in a Brazilian white‐sand flooded tropical forest

The investigation of ecological processes that maintain species coexistence is revealing in naturally disturbed environments such as the white‐sand tropical forest, which is subject to periodic flooding that might pose strong habitat filtering to tree species. Congeneric species are a good model to investigate the relative importance of ecological processes that maintain high species diversity because they tend to exploit the same limiting resources and/or have similar tolerance limits to the same environmental conditions due to their close phylogenetic relationship. We aim to find evidence for the action and relative importance of different processes hypothesized to maintain species coexistence in a white‐sand flooded forest in Brazil, taking advantage of data on the detailed spatial structure of populations of congeneric species. Individuals of three Myrcia species were tagged, mapped, and measured for diameter at soil height in a 1‐ha plot. We also sampled seven environmental variables in the plot. We employed several spatial point process models to investigate the possible action of habitat filtering, interspecific competition, and dispersal limitation. Habitat filtering was the most important process driving the local distribution of the three Myrcia species, as they showed associations, albeit of different strength, to environmental variables related to flooding. We did not detect spatial patterns, such as spatial segregation and smaller size of nearby neighbors, that would be consistent with interspecific competition among the three congeneric species and other co‐occurring species. Even though congeners were spatially independent, they responded to differences in the environment. Last, dispersal limitation only led to spatial associations of different size classes for one of the species. Given that white‐sand flooded forests are highly threatened in Brazil, the preservation of their different habitats is of utmost importance to the maintenance of high species richness, as flooding drives the distribution of species in the community.     

Aggregated spatial distributions of species in a subtropical karst forest,southwestern China

Aims Spatial distribution patterns of species reflect not only the ecological processes but also the habitat features that are related to species distribution. In karst topography, species distribution patterns provide more specific information about their environments. The objectives of this study are as follows: (i) to analyse and explain the spatial distribution patterns of conspecific trees in an old-growth subtropical karst forest; (ii) to investigate pattern changes at different spatial scales; (iii) to test the spatial pattern similarity (or dissimilarity) between trees at different abundances, diameter at breast height classes, canopy layers and different functional groups (shade tolerance and seed dispersal mode); (iv) to examine whether habitat heterogeneity has an important effect on the species spatial distribution.Methods The spatial distributions of woody species with ≥20 individuals in a 1-ha subtropical karst forest plot at Maolan in southwestern China were quantified using the relative neighbourhood density Ω based on the average density of conspecific species in a circular neighbourhood around each species.Important findings Aggregated distribution is the dominant pattern in the karst forest, but the ratio of aggregated species in total species number decreases with an increase in spatial scale. Less abundant species are more aggregated than most abundant species. Aggregation is weaker in larger diameter classes, which is consistent with the prediction of self-thinning. Seed dispersal mode influences spatial patterns, with species dispersed by animals being less aggregated than those dispersed by wind and gravity. Other species functional traits (e.g. shade tolerance) also influence the species spatial distributions. Moreover, differences among species habitat associations, e.g. with rocky outcrops, play a significant role in species spatial distributions. These results indicate that habitat heterogeneity, seed dispersal limitation and self-thinning primarily contribute to the species spatial distributions in this subtropical karst forest.     

Density‐dependence in common tree species in a tropical dry forest in Mudumalai,southern India

Abstract. Density‐dependence in tree population dynamics has seldom been examined in dry tropical forests. Using long‐term data from a large permanent plot, this study examined 16 common species in a dry tropical forest in southern India for density‐dependence. Employing quadrat‐based analyses, correlations of mortality, recruitment and population change with tree densities were examined. Mortality in 1–10 cm diameter trees was largely negatively correlated with conspecific density, whereas mortality in > 10 cm diameter trees was positively correlated. Mortality was, however, largely unaffected by the basal area and abundance of heterospecific trees. Recruitment was poor in most species, but in Lagerstroemia microcarpa (Lythraceae), Tectona grandis (Verbenaceae) and Cassia fistula (Fabaceae), species that recruited well, strong negative correlations of recruitment with conspecific basal area and abundance were found. In a few other species that could be tested, recruitment was again negatively correlated with conspecific density. In Lagerstroemia, recruitment was positively correlated with the basal area and abundance of heterospecific trees, but these correlations were non‐significant in other species. Similarly, although the rates of population change were negatively correlated with conspecific density they were positive when dry‐season ground fires occurred in the plot. Thus, the observed positive density‐dependence in large‐tree mortality and the negative density‐dependence in recruitment in many species were such that could potentially regulate tree populations. However, repeated fires influenced density‐dependence in the rates of population change in a way that could promote a few common species in the tree community.     

Effects of sika deer on tree seedlings in a warm temperate forest on Yakushima Island,Japan

High-density herbivore species often play an important role in forest regeneration. Native sika deer (Cervus nippon yakushimae) inhabit a high density (51.5–63.8head/km², estimated by a pellet count method) area in the western part of a lowland natural forest on Yakushima Island, Japan. To test experimentally the impact of sika deer on the mortality and the survivability of current-year seedlings, which are at a more vulnerable stage than the later stages, we constructed fenced exclosures, planted seeds of nine sapfruit tree species and compared the mortality and the survivability of current-year seedlings between fenced and unfenced quadrats. Large seeded species had significantly greater survivability in fenced quadrats than in unfenced quadrats. However, the survivability disagreed with feeding preferences. Sika deer activity increased seedling mortality of large-seeded species more than that of small-seeded species, and did not decrease much seedling survivability of not-preferred species. We found that the physical disturbance by the high density of sika deer resulted in mortality for both preferred and not-preferred species, and that deer herbivory was important for preferred species.     

Microtopography and distribution of canopy trees in a subtropical evergreen broad-leaved forest in the northern part of Okinawa Island,Japan

The spatial distribution of trees in relation to topography was investigated using two topographic indices, slope steepness and slope configuration, in a 4-ha plot in a subtropical evergreen forest in the northern part of Okinawa Island, Japan. Most species showed an aggregated distribution and patch size was related to various microtopographical features, including small ridges and valleys. In a cluster analysis based on the dissimilarity of each species distribution, the species were divided into three major clusters. A significant correlation between the dissimilarity and the distance between each species on the axis of the two topographic indices indicated that species association was, in part, explained by the topographic indices. I suggest that species distributed on steep and concave slopes regenerate depending on disturbances such as landslides on unstable topography, whereas species distributed on ridges and upper slopes regenerate depending on the canopy gap. A number of species that were less abundant in the 4-ha plot occurred in the riparian area near a stream, where the density of more abundant species was low. The results of this study support the existence of habitat niche divergence related to topography in a subtropical evergreen broad-leaved forest.     

Comparison of lepidopteran larval communities among tree species in a temperate deciduous forest, Japan

Abstract.  1. The enormous diversity of phytophagous insects in forest canopies is hypothesised to be supported by the number of herbivorous species per host tree species or host specificity. It is therefore necessary to examine the effect of host plant species on compositional changes in the herbivore communities.
2. The lepidopteran larval communities were examined in the canopies of 10 tree species in a temperate deciduous forest of Japan. The phylogeny and leaf flush phenology of host plant species were taken into account as factors affecting the herbivore community assembly.
3. Examination of seasonal changes in the larval community structures on each tree species showed that larval species richness, abundance, and evenness decreased significantly from spring to summer. Larval species richness and abundance were characterised by family-level phylogenetic differences among tree species, whereas evenness was determined at a higher taxonomic level.
4. Compositional changes in the larval communities among tree species showed a remarkable pattern, with a phylogenetic effect at a high taxonomic level in spring, similar to evenness, but a phenological effect in summer. This suggests that host specificity could support the lepidopteran larval diversity in spring.
5. These results suggest that the differences in host utilisation of the herbivore, which reflects the phylogenetic effect of the host plants, can be important as a factor affecting the diversity of lepidopteran larval communities in temperate forests.     

广西大青山次生林的群落特征及主要乔木种群的空间分布格局

本文依托广西友谊关森林生态系统国家定位观测研究站在大青山设置的1 ha长期监测样地, 分析了森林群落的物种组成、区系特征及乔木种群的径级结构, 并用点格局分析方法的O-ring统计对主要乔木植物种群的空间分布格局及其空间关联性进行了研究, 旨在深入探讨该区域次生林的物种多样性特点及其维持机制, 分析影响优势树种空间分布格局的可能因素。大青山次生林共调查到植物109种, 其中乔木58种、灌木29种、草本22种, 樟科为样地内物种最丰富的科, 区系组成以泛热带成分为主; 乔木树种的径级结构接近倒“J”形, 主要种群的个体集中分布于中小径级范围(1-5 cm), 林分结构合理, 更新良好。从物种多度、胸高断面积和重要值来看, 大叶栎(Quercus griffithii)和锈毛梭子果(Eberhardtia aurata)是群落中的共优种, 其个体数占总个体数的30.8%, 鸭公树(Neolitsea chuii)、广东琼楠(Beilschmiedia fordii)和尖连蕊茶(Camellia cuspidata)为群落的主要伴生树种。用完全随机模型不排除生境异质性的条件下, 主要种群多数呈聚集分布; 用异质性随机模型排除生境异质性的条件下, 主要种群的聚集程度显著下降, 仅在小尺度上呈聚集分布; 主要树种均在一定尺度上表现为两两间正相关, 且在0-50 m的大部分尺度上显示出相互独立的特点, 没有表现出负相关。     

Canopy disturbance and gap partitioning promote the persistence of a pioneer tree population in a near‐climax temperate forest of the Qinling Mountains,China

An unresolved question of temperate forests is how pioneer tree species persist in mature forests. In order to understand the responsible mechanisms, we investigated a near‐climax mixed temperate forest dominated by Betula albosinensis in the Qinling Mountains of China. Through establishing four 50 m × 50 m plots, we examined the canopy disturbance characteristics and its effects on tree recruitments. We further test the intra‐ and interspecific effects on the recruitment of B. albosinensis. The obtained data demonstrated canopy disturbance was frequent but most small‐sized. The canopy gaps are caused mainly by adult B. albosinensis by snapping. The regeneration of coexistent tree species shows a distinct preference for gap size. B. albosinensis were clumped at the juvenile stage and small scales. B. albosinensis juveniles were positively associated with B. utilis juveniles and negatively associated with the conspecific and B. utilis large trees. In addition, B. albosinensis juveniles showed negative associations with contemporary other tree species. Our results suggested that canopy disturbance caused by canopy trees and gap partitioning among the coexistent tree species are important for the persistence of the mixed forest. As a main gapmaker, B. albosinensis appear to develop a self‐perpetuating life‐history trait and allow them to persist.     

Variation in wood density,wood water content,stem growth and mortality among twenty‐seven tree species in a tropical rainforest on Borneo Island

Abstract Interspecific variation among wood density (WD), wood water content (WWC), tree mortality and diameter at breast height (d.b.h.) increment was examined for 27 tree species (from 13 families), based on a 9‐year interval data obtained from a permanent 1‐ha forest plot setup for long‐term studies of tree dynamics in Kuala Belong rainforest, Brunei, on Borneo Island. The species were also categorized into three adult stature groups of understorey (maximum height ≤15–20 m tall, n = 14), midcanopy (maximum height, 20–30 m tall, n = 8) and canopy/emergent (>maximum height, >30 m tall, n = 5) tree species. All measured traits varied appreciably among species. Tree WD varied between 0.3 and 0.8 g cm⁻³, and exhibited the least coefficient of variation (14.7%). D.b.h. increment was low, averaging 1.05 (95% confidence limits: 0.57–2.13) mm year⁻¹ and was attributed to predominance of understorey species in the sampled plot. Overall, annual mortality was also low, averaging 2.73% per year. The three adult stature groups differed significantly in d.b.h. increment and WWC but not in tree mortality and WD. Across species and especially more so when phylogenetic effect is minimized, WD was negatively related to tree mortality and d.b.h. increment, while a positive trend was observed between d.b.h. increment and tree mortality. A negative trend was also detected between maximum plant height and WWC, which was interpreted as a consequence of increased evaporative demand and use of xylem stored water by taller trees in order to compensate for hydraulic limitations to water transport induced by frictional resistance. No doubt, the traits chosen may vary spatially, but the consistent interspecific patterns observed in this study among coexisting species of differing adult stature reflect ‘vertical’ niche differentiation and may help to explain population regulation in a multispecies ecosystem like tropical rainforest.     

Gap-phase dynamics and coexistence of a long-lived pioneer and shade-tolerant tree species in the canopy of an old-growth coastal temperate rain forest of Chiloé Island, Chile

Aim A major question with regard to the ecology of temperate rain forests in south‐central Chile is how pioneer and shade‐tolerant tree species coexist in old‐growth forests. We explored the correspondence between tree regeneration dynamics and life‐history traits to explain the coexistence of these two functional types in stands apparently representing a non‐equilibrium mixture. Location This study was conducted in northern Chiloé Island, Chile (41.6° S, 73.9° W) in a temperate coastal rain forest with no evidence of stand disruption by human impact. Methods We assessed stand structure by sampling all stems within two 50 × 20 m and four 5 × 100 m plots. A 600‐m long transect, with 20 uniformly spaced sampling points, was used to quantify seedling and sapling densities, obtain increment cores, and randomly select 10 tree‐fall gaps. We used tree‐ring analysis to assess establishment periods and to relate the influences of disturbances to the regeneration dynamics of the main canopy species. Results Canopy emergent tree species were the long‐lived pioneer Eucryphia cordifolia and the shade‐tolerant Aextoxicon punctatum. Shade‐tolerant species such as Laureliopsis philippiana and several species of Myrtaceae occupied the main canopy. The stem diameter distribution for E. cordifolia was distinctly unimodal, while for A. punctatum it was multi‐modal, with all age classes represented. Myrtaceae accounted for most of the small trees. Most tree seedlings and saplings occurred beneath canopy gaps. Based on tree‐ring counts, the largest individuals of A. punctatum and E. cordifolia had minimum ages estimated to be > 350 years and > 286 years, respectively. Shade‐tolerant Myrtaceae species and L. philippiana had shorter life spans (< 200 years). Most growth releases, regardless of tree species, were moderate and have occurred continuously since 1750. Main conclusions We suggest that this coastal forest has remained largely free of stand‐disrupting disturbances for at least 450 years, without substantial changes in canopy composition. Release patterns are consistent with this hypothesis and suggest that the disturbance regime is dominated by individual tree‐fall gaps, with sporadic multiple tree falls. Long life spans, maximum height and differences in shade tolerance provide a basis for understanding the long‐term coexistence of pioneer and shade‐tolerant tree species in this coastal, old‐growth rain forest, despite the rarity of major disturbances.     

Temperate migrants and resident bird species in Afro‐tropical savannahs show similar levels of ecological generalism

The specificity of an animal's habitat requirements will determine its ability to deal with anthropogenic climate and habitat change. Migratory birds are thought to be particularly vulnerable to such change, but theory predicts that they should be largely generalists. This prediction was tested with the aim of assessing whether migratory Palaearctic‐breeding birds wintering in the savannah biome of Africa are more or less generalist in their habitat use compared with taxonomically and ecologically similar Afro‐tropical resident species. The degree of specialization of these species groups to certain habitat characteristics was assessed and compared by calculating the relative occurrence of the species along habitat gradients, where wide occurrence indicates generalism and narrow occurrence indicates specialism. Palaearctic migrants as a group could not clearly be distinguished as generalists relative to Afro‐tropical residents with respect to habitat attributes. The only indication of greater flexibility in Palaearctic migrants was a significant tendency to use habitats over a wider latitudinal range. The results suggest that migrants are generalists, but not necessarily more generalist than taxonomically similar resident species that also occur over a wide range of habitat types within the savannah biome. The availability of specific habitat requirements on the wintering grounds in Africa is therefore unlikely to be a primary limiting factor for many Afro‐Palaearctic migratory bird species.     

An assessment of riparian restoration outcomes in two rural catchments in south‐western Victoria: Focusing on tree and shrub species richness,structure and recruitment characteristics

Riparian ecosystems are among the most degraded systems in the landscape, and there has been substantial investment in their restoration. Consequently, monitoring restoration interventions offers opportunities to further develop the science of riparian restoration, particularly how to move from small‐scale implementation to a broader landscape scale. Here, we report on a broad range of riparian revegetation projects in two regions of south‐western Victoria, the Corangamite and Glenelg‐Hopkins Catchment Management Areas. The objectives of restoration interventions in these regions have been stated quite broadly, for example, to reinstate terrestrial habitat and biodiversity, control erosion and improve water quality. This study reports on tree and shrub composition, structure and recruitment after restoration works compared with remnant vegetation found regionally. Within each catchment, a total of 57 sites from six subcatchments were identified, representing three age‐classes: <4, 4–8 and >8–12 years after treatment, as well as untreated (control) sites. Treatments comprised fencing to exclude stock, spraying or slashing to reduce weed cover, followed by planting with tube stock. Across the six subcatchments, 12 reference (remnant) sites were used to provide a benchmark for species richness, structural and recruitment characteristics and to aid interpretation of the effects of the restoration intervention. Vegetation structure was well developed in the treated sites by 4–8 years after treatment. However, structural complexity was higher at remnant sites than at treated or untreated sites due to a higher richness of small shrubs. Tree and shrub recruitment occurred in all remnant sites and at 64% of sites treated >4 years ago. Most seedling recruitment at treatment sites was by Acacia spp. This assessment provides data on species richness, structure and recruitment characteristics following restoration interventions. Data from this study will contribute to longitudinal studies of vegetation processes in riparian landscapes of south‐western Victoria.     

Dispersion pattern and mortality of seeds and seedlings ofFagus crenata Blume in a cool temperate forest in western Japan

The seed and seedling mortality ofFagus crenata Blume after a mast year (1993) was examined in relation to density and distance from the nearest conspecific adult tree in a mixed conifer-hardwood forest in Ohdaigahara, western Japan. The mortality of fallen seeds during winter amounted to 93.7%, and 79.2% of the current-year seedlings died in the first growing season. The most important factor of death for both seeds and seedlings was predation by vertebrates. The mortality of seeds during winter was positively correlated with sound seed density. The mortality of seedlings was positively correlated with density but not significantly related to the distance from the nearest crown edge of a conspecific adult tree. Mortality patterns varied with stages and spatial scales due to the behavior of predators; it is thus important to investigate the spatial pattern of seeds and seedling mortality at various temporal and spatial scales. After the first growing season, the difference in seedling density between distance classes was not significant at <4m from the nearest adult trees due to density-dependent mortality. However, seedling density was significantly lower in the ≥4 m class than in the <4 m classes.     

Substrate conditions,foliar nutrients and the distributions of two canopy tree species in a Costa Rican secondary rain forest

A 28 yr old secondary lowland rain forest in Costa Rica was dominated by two tree species of contrasting ecologies, Vochysia ferruginea - a species typical of well-drained but infertile soils of high Al saturation, and Cordia alliodora, a species requiring soils of at least moderate fertility. The two species exhibited markedly different spatial distributions in the forest and we sought to determine whether or not these different distributions were related to variation in substrate conditions and the nutrient requirements of the two species. Two soil types were present: Ultisols (Typic Haplohumults) and Inceptisols (Typic Dystropepts) and topography was of low hills. The study formed part of an analysis of site quality for timber production in the two species and therefore used standard forestry methods for such analyses. 36 plots of 20 m×20 m were established using predetermined criteria of site uniformity, presence of at least four dominant trees of at least one of the study species, and absence of disturbance. The abundance (number of individuals 10 cm dbh) of each species was determined in each plot. Soil samples were taken in 27 of the 36 plots, 9 plots being considered to replicate conditions already sampled, and 14 soil chemical and physical variables were measured using standard methods. Foliar nutrient analyses were carried out for trees of both species with crowns fully exposed to sunlight, distributed across the gradient of soil conditions. Variations in species abundances were not related to soil type, but plots in which Vochysia ferruginea was more abundant tended to be on steeper slopes with soils of higher exchangeable acidity and lower concentrations of Mn; Cordia alliodora was more abundant on gentler topography where soils had much lower exchangeable acidity but higher Mn. Differences between the two species in foliar nutrient concentrations were marked and supported previous interpretations of their nutrient requirements; foliar nutrients of Vochysia ferruginea were typical of tree species of moist tropical forest on infertile soils, and those of Cordia alliodora typical of a species requiring more fertile soils. Factors such as the distributions of seed trees at site abandonment may affect the spatial distributions of tree species in secondary forests such as that studied. The relationships of the distributions of the two species to substrate variation, however, and their evidently different nutrient requirements, support the hypothesis that variation in the composition and structure of the forest studied is at least partially related to exchangeable acidity and its dominant cation, Al.     

Habitat associations with topography and canopy structure of tree species in a tropical montane forest on Mount Kinabalu,Borneo

Habitat associations with topography and canopy structure of 42 abundant tree species were studied in a 2.74-ha plot of tropical montane forest on Mount Kinabalu, Borneo. Many of these species belong to the same higher taxa including eight families and four genera. Analysis of intraspecific spatial distributions for stems ≥ 10 cm diameter revealed that 28 species (including all six species of Fagaceae) showed aggregated distributions at the 100-m² and/or 400-m² scales, and that 20 species showed habitat associations with topography by torus-translation tests; 17 species showed both characteristics. Species' associations with the local canopy structure were characterized by crown position index (CPI), which was defined relative to neighbour trees. The CPI differed greatly among individual stems at 10–40 cm diameter, and 19 species showed significantly different frequencies of crowns exposed vertically versus those shaded beneath the canopy. Mean growth rates at 10–40 cm diameter and size distributions of species were not related to topographic associations, but were explained by the associations with canopy structure; species with more exposed crowns grew faster and had less positively skewed distributions. Diversity in habitat associations was manifest between two genera (Syzygium and Tristaniopsis) in the family Myrtaceae and among species in these genera, but was less evident in other families and two genera (Garcinia and Lithocarpus). This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of hydrographic features on larval fish distribution during the south‐westerly monsoon in the waters of Taiwan,western North Pacific Ocean

The spatial distribution patterns of fish larvae and the relationships with hydrographic conditions in the waters surrounding Taiwan were studied in August 2004 when the south‐westerly monsoon prevailed. A total of 6566 fish larvae were identified, belonging to 80 families, 129 genera and 230 species. Cluster analysis revealed two station groups, one associated with the South China Sea Surface Current (SCSSC) and the other with the Kuroshio Current (KC). The SCSSC group was characterized by mostly coastal and neritic species, and the KC group was predominated by oceanic species. Larger fish larvae were generally more abundant in the neritic waters west of Taiwan where the SCSSC prevails than in the waters east of Taiwan where the KC prevails. The combination of chlorophyll a, zooplankton and nitrite best explained the relationship of larval fish distribution and environmental variables, implying that the distribution of fish larvae in summer was closely linked to the food source. The changing of monsoons potentially affects the succession of water masses and the transport and assemblage of fish larvae in this study area.     

Testing the divergent adaptation of two congeneric tree species on a rainfall gradient using eco‐physio‐morphological traits

In tropical Africa, evidence of widely distributed genera transcending biomes or habitat boundaries has been reported. The evolutionary processes that allowed these lineages to disperse and adapt into new environments are far from being resolved. To better understand these processes, we propose an integrated approach, based on the eco‐physio‐morphological traits of two sister species with adjacent distributions along a rainfall gradient. We used wood anatomical traits, plant hydraulics (vulnerability to cavitation, wood volumetric water content, and hydraulic capacitance), and growth data from the natural habitat, in a common garden, to compare species with known phylogeny, very similar morphologically, but occupying contrasting habitats: Erythrophleum ivorense (wet forest) and Erythrophleum suaveolens (moist forest and forest gallery). We identified some slight differences in wood anatomical traits between the two species associated with strong differences in hydraulics, growth, and overall species distribution. The moist forest species, E. suaveolens, had narrower vessels and intervessel pits, and higher vessel cell‐wall reinforcement than E. ivorense. These traits allow a high resistance to cavitation and a continuous internal water supply of the xylem during water shortage, allowing a higher fitness during drought periods, but limiting growth. Our results confirm a trade‐off between drought tolerance and growth, controlled by subtle adaptations in wood traits, as a key mechanism leading to the niche partitioning between the two Erythrophleum species. The generality of this trade‐off and its importance in the diversification of the African tree flora remains to be tested. Our integrated eco‐physio‐morpho approach could be the way forward.     

Aggregated recruitment patterns under adult crowns in Photinia glabra,a bird‐dispersed tree species

To clarify recruitment patterns of Photinia glabra, which is an evergreen, broad‐leaved, bird‐dispersed tree species, we analyzed spatial distribution in P. glabra recruits at each growth stage and demography of current‐year seedlings with respect to distributions of adults in a warm‐temperate secondary forest, western Japan. Although individuals ≥ 5 cm diameter at breast height (DBH) that had nearly produced fruits showed a random distribution, seedlings (≥ 1 year old, < 10‐cm stem length [SL]), small saplings (10 ≤ SL < 30 cm) and large saplings (≥ 30‐cm SL, < 5‐cm DBH) were clumped and associated with reproductive adults at approximately 2–3‐m scales, nearly equal to their average crown radius. Based on monitoring the demography of current‐year seedlings, emerged seedling density profoundly decreased, and no seedlings survived at longer than an adult's crown scales, with distance‐dependent mortality as a result of disease and herbivory not greatly affecting the current‐year seedling mortality. Thus, aggregated seed dispersal under the crown of adult P. glabra would directly influence the distribution of recruits for P. glabra in this forest. Of the bird‐dispersed tree species in this forest, P. glabra produced the highest amount of fruits during large crop years, and their fruits ripened during the late seasonal period (early January), suggesting that birds might be strongly attracted to these species, in turn leading to seeds being deposited mostly under the tree crowns. We propose that dispersal limitation would occur, even in a bird‐dispersed tree species such as P. glabra, owing to plant–bird interactions in the forest.