Genetic variation and differentiation in populations of Japanese emperor oak <Emphasis Type="Italic">Quercus dentata</Emphasis> Thunb. and Mongolian oak <Emphasis Type="Italic">Quercus mongolica</Emphasis> Fisch. ex Ledeb.) in the south of the Russian Far East

Allozyme variation of Japanese emperor oak Quercus dentata Thunb. and Mongolian oak Quercus mongolica Fisch. ex Ledeb.) was examined in 11 populations of these species from southern Primorye. Analysis of 18 loci showed that in these populations, 66.7% of genes of Mongolian oak are polymorphic, the number of alleles per locus being 2.28. In Japanese emperor oak, these parameters were respectively 59.8 and 2.36%. The observed heterozygosity in both species did not differ from the expected values, constituting 0.198 in Japanese emperor oak and 0.161 in Mongolian oak. The Nei’s distance between Quercus mongolica and Q. dentata was 0.053. The main contribution to the species differentiation is made by loci Lap-1, Idh-1, Pgm-1, and Ndh-1, although none of them is diagnostic. The Japanese emperor oak and Mongolian oak populations formed separate clusters in an UPGMA dendrogram. Taking into account morphological and ecological isolation of the species, we suggest that the differences in gene frequencies may reflect selection acting in favor of adaptation to different growth conditions and counteracting between-species hybridization.     

Interspecific variation in functional traits of oak seedlings (<Emphasis Type="Italic">Quercus ilex,Quercus trojana,Quercus virgiliana</Emphasis>) grown under artificial drought and fire conditions

To face summer drought and wildfire in Mediterranean-type ecosystems, plants adopt different strategies that involve considerable rearrangements of biomass allocation and physiological activity. This paper analyses morphological and physiological traits in seedlings of three oak species (Quercus ilex, Quercus trojana and Quercus virgiliana) co-occurring under natural conditions. The aim of this study was to evaluate species-specific characteristics and the response of these oak seedlings to drought stress and fire treatment. Seedlings were kept in a growth chamber that mimicked natural environmental conditions. All three species showed a good degree of tolerance to drought and fire treatments. Differences in specific biomass allocation patterns and physiological traits resulted in phenotypic differences between species. In Q. ilex, drought tolerance depended upon adjustment of the allocation pattern. Q. trojana seedlings undergoing mild to severe drought presented a higher photosystem II (PSII) efficiency than control seedlings. Moreover, Q. trojana showed a very large root system, which corresponded to higher soil area exploitation, and bigger leaf midrib vascular bundles than the other two species. Morphological and physiological performances indicated Q. trojana as the most tolerant to drought and fire. These characteristics contribute to a high recruitment potential of Q. trojana seedlings, which might be the reason for the dominance of this species under natural conditions. Drought increase as a result of climate change is expected to favour Q. trojana, leading to an increase in its spatial distribution.     

Buds buried in bark: the reason why <Emphasis Type="Italic">Quercus suber</Emphasis> (cork oak) is an excellent post-fire epicormic resprouter

Key message

Cork oak has buds protected by the full thickness of its substantial phellem, thus explaining why it is the only European tree that can epicormically resprout after higher intensity fire.

Abstract

Epicormic resprouting has various ecological advantages over basal resprouting. However, after higher intensity fires epicormic resprouting is rare as it is difficult for trees and shrubs to keep both their buds and vascular cambia alive. Quercus suber (cork oak) is the only European tree that can resprout epicormically after higher intensity fires. Q. suber develops very thick bark and it has been assumed, without anatomical evidence, that the bark protects the epicormic buds. We investigated if developmental anatomy could explain why Q. suber is an excellent post-fire epicormic resprouter. We examined buds from mature Q. suber trees, macroscopically using a stereo microscope and microscopically using semi-thin microtome sections. Q. suber produced buds in the foliage leaf axils and the bud scale axils. With the commencement of extensive phellem (cork) production the base of the epicormic buds remained at, or just below, the level of the phellogen and thus cork began to bury the buds, although a narrow tube connected each bud to the bark surface. Q. suber epicormic buds became deeply buried in the phellem and would be protected from heat by the full phellem thickness. With its rapid and substantial development of phellem Q. suber had well-protected epicormic buds even in relatively small diameter stems. These results provide the anatomical evidence to show why Q. suber is a noted epicormic resprouter after crown fire.

     

Acorns of invasive Northern Red Oak (<Emphasis Type="Italic">Quercus rubra</Emphasis>) in Europe are larval hosts for moths and beetles

In their first phase of expanding into new areas, invasive plants often take advantage of the inability of existing herbivores and pathogenic species to exploit them. However, in the longer term local enemies may adapt to using these invasive species as a food source. This study assesses the use of mature acorns of two oak species in Europe (the native Pedunculate Oak Quercus robur and the invasive Northern Red Oak Quercus rubra) by moths Cydia fagiglandana and Cydia splendana and beetles Curculio spp. We show that acorns of invasive oak species can be equally attractive to C. splendana but only partially so to C. fagiglandana where infestation rates where significantly lower (approximately half) compared to the native oak. The infestation by Curculio beetles of Northern Red Oak was marginal, less than 1% of the rate in the native oak species. The larval final weights did not differ significantly between host species, but emergence of C. splendana and Curculio spp. took significantly longer in acorns of Northern Red Oak. It is likely that C. fagiglandana and C. splendana have increased their niche breadths by exploiting invasive oak species and avoiding competition with the Curculio weevils. Furthermore, the occurrence of Northern Red Oak could stabilize food resources during years when native oak species have poor acorn crops.     

Species-specific alleles at a <Emphasis Type="Italic">β-</Emphasis>tubulin gene show significant associations with leaf morphological variation within <Emphasis Type="Italic">Quercus petraea</Emphasis> and <Emphasis Type="Italic">Q. robur</Emphasis> populations

Quercus petraea and Q. robur are largely sympatric oak species in western and central Europe and known for their intensive genetic exchange which has made the discovery of species-diagnostic markers a huge challenge. Various natural white oak populations (Q. petraea/Q. robur including mixed stands) were investigated for their variability and differentiation patterns at a β-tubulin gene (qutub8) in a European-wide survey. This gene was chosen as a possible candidate among loci subjected to selection and maintaining integrity between species. Two frequent alleles depicted as indels within qutub8’s first intron showed remarkably high interspecific genetic differentiation, with Weir and Cockerham’s theta per allele values ranging from 0.17 to 0.30 for one allele and from 0.04 to 0.19 for the other allele in such mixed oak stands where the multi-allelic qutub8 locus showed significant interspecific F _ST . For three mixed stands, qutub8’s F _ST significantly departed from the expected neutral differentiation patterns (F _ST ranging from 0.063 to 0.080 for this multi-allelic marker) and thus could be influenced by selection. Significant associations were found between genotypic variation and leaf dimensions as well as leaf structure patterns, after having accounted for species and stand effects. Qutub8 represents a locus that exhibits significant species differentiation and is linked to morphological discriminant traits. Consequently, qutub8 likely contributes to species divergence within the European white oak complex.     

The effect of fodder plant genotype on the variation of larval fitness traits in genotype classes of green oak leafroller moth

The effect of genetic variation of oak (Quercus pubescens L. and Q. petraea L.) on the genotype fitness components in green oak leafroller moth larvae (Tortrix viridana L.) at esterase (Est-4) and protease (Pts-4) loci was studied. The samples of larvae were collected from nine oak trees, whose genetic variation was assayed by RAPD-PCR using primer OPA14. The contributions of the factors of oak species/genotype and green oak leafroller moth genotype and their interaction to the variation of important size-related traits of the larvae were evaluated by two-way ANOVA. It was shown that the same larval genotype can display maximum fitness on the trees of one species or genotype and minimum, on the trees of other species or genotype. The interactions between the oak genotype and green oak leafroller moth genotype factors lead to the relationships that appear in statistically significant associations between genotype classes of green oak leafroller moth and oak. These results are discussed from the standpoint of a recently developed new field, community or ecosystem genetics.     

Development of microsatellite markers for the carnivorous plant <Emphasis Type="Italic">Genlisea aurea</Emphasis> (Lentibulariaceae) using genomics data of NGS

Genlisea aurea A.St.-Hil. is a carnivorous plant endemic species to Brazil in the Lentibulariaceae family. Very few studies have addressed the genetic structure and conservation status of G. aurea and the Lentibulariaceae. Microsatellites markers are advantageous tools that can be employed to predict the vulnerability of Lentibulariaceae species. Therefore, the development of molecular markers focusing the population analyses of Genlisea for future genetic studies and conservation actions are essential. Thus, we developed simple sequence repeats (SSRs) based on in silico analyses of G. aurea draft genome assembly. We characterized 40 individuals from several populations and identified 12 loci that were polymorphic, with heterozygosity between 0.123 and 0.650. We demonstrated that the G. aurea SSR markers work cross-species in Genlisea filiformis, G. repens, G. tuberosa and G. violacea. These markers will be important for future population, phylogeographic and conservation studies in G. aurea and other Genlisea species.     

Complex phylogeographic patterns indicate Central American origin of two widespread Mesoamerican <Emphasis Type="Italic">Quercus</Emphasis> (Fagaceae) species

The northern Neotropical region is characterized by a heterogeneous geological and climatic history. Recent studies have shown contrasting patterns regarding the role of geographic elements as barriers that could have determined phylogeographic structure in various species. Recently, the phylogeography and biogeography of Quercus species have been studied intensively, and the patterns observed so far suggest contrasting evolutionary histories for Neotropical species in comparison with their Holarctic relatives. The goal of this study was to describe the phylogeographic structure of two Neotropical oak species (Quercus insignis and Quercus sapotifolia) in the context of the geological and palaeoclimatic history of the northern Neotropics. Populations through the distribution range of both species were collected and characterized using nine chloroplast DNA microsatellite loci. Both oak species showed high levels of genetic diversity and strong phylogeographic structure. The distribution of genetic variation in Q. insignis suggested an influence of two major barriers, the Isthmus of Tehuantepec and the Nicaraguan Depression, while Q. sapotifolia exhibited a genetic structure defined by the heterogeneity of the Chortis highlands. The haplotype networks of both species indicated complex histories, suggesting that colonization from the Sierra Madre de Chiapas to central Mexico and from the north of the Nicaraguan Depression to the Costa Rican mountains may have occurred during different stages, and apparently more than one time. In conclusion, the phylogeographic structure of Neotropical oak species seems to be defined by a combination of geological and climatic events.     

Increased nitrogen deposition alleviated the adverse effects of drought stress on <Emphasis Type="Italic">Quercus variabilis</Emphasis> and <Emphasis Type="Italic">Quercus mongolica</Emphasis> seedlings

The plasticity response of Quercus variabilis and Quercus mongolica seedlings to combined nitrogen (N) deposition and drought stress was evaluated, and their performance in natural niche overlaps was predicted. Seedlings in a greenhouse were exposed to four N deposition levels (0, 4, 8, and 20 g N m^?2 year^?1) and two water levels (80 and 50 % field-water capacity). Plant traits associated with growth, biomass production, leaf physiology, and morphology were determined. Results showed that drought stress inhibited seedling performance, altered leaf morphology, and decreased fluorescence parameters in both species. By contrast increased N supply had beneficial effects on the nutritional status and activity of the PSII complex. The two species showed similar responses to drought stress. Contrary to the effects in Q. mongolica, N deposition promoted leaf N concentration, PSII activity, leaf chlorophyll contents, and final growth of Q. variabilis under well-watered conditions. Thus, Q. variabilis was more sensitive to N deposition than Q. mongolica. However, excessive N supply (20 g N m^?2 year^?1) did not exert any positive effects on the two species. Among the observed plasticity of the plant traits, plant growth was the most plastic, and leaf morphology was the least plastic. Therefore, drought stress played a primary role at the whole-plant level, but N supply significantly alleviated the adverse effects of drought stress on plant physiology. A critical N deposition load around 20 g N m^?2 year^?1 may exist for oak seedlings, which may more adversely affect Q. variabilis than Q. mongolica.     

Morphological diversity and phylogeography of the Georgian durmast oak (<Emphasis Type="Italic">Q. petraea</Emphasis> subsp. <Emphasis Type="Italic">iberica</Emphasis>) and related Caucasian oak species in Georgia (South Caucasus)

The Caucasus region is one of the 25 global biodiversity hotspots and constitutes a shelter area for Neogene relict species as well as a center of ongoing radiation. In order to elucidate the taxonomic identity, divergence patterns, and evolutionary history of the largely widespread Georgian durmast oak (Quercus petraea subsp. iberica), we examined leaf morphology and chloroplast DNA (cpDNA) (trnH-psbA, trnK-matK) sequence variation across its South Caucasian range. Six other oak taxa distributed throughout Georgia were included in the dataset and used for comparison. Evidence for differentiation in both sets of traits was found. Populations represented by different taxa from ecologically equivalent areas showed common morphological features and genetic structures. Molecular analysis clearly indicated the presence of two major haplotype lineages (West Caucasian vs. East Caucasian zonation type) and suggested a maternal lineage diversification of Q. petraea subsp. iberica in the Late Miocene, as a likely result of complex patterns associated with major orogenic and climatic changes. The Quaternary glacial oscillations resulted in a number of less common, derived haplotypes. Based on mismatch distribution analysis and neutrality tests, we found no evidence of demographic expansion for the populations from the West and East Caucasian zonation types. The two Caucasian provinces therefore acted as important shelter/diversification areas and as a lineage crossroad for the Georgian oaks. Close intra- and interspecific cpDNA relationships shared with other oaks from bordering countries support the relevant role played by the Colchis region as a primary refugium for the European temperate forest species.     

Genetic determination of tannins and herbivore resistance in <Emphasis Type="Italic">Quercus ilex</Emphasis>

Genetic variability of trees influences the chemical composition of tissues. This determines herbivore impact and, consequently, herbivore performance. We evaluated the independent effects of plant genotype and provenance on the tannin content of holm oak (Quercus ilex) and their consequences for herbivory and performance of gypsy moth (Lymantria dispar) larvae. Oak seedlings of 48 open-pollinated families from six populations were grown in a common garden in central Spain. Half the plants were subjected to defoliation by gypsy moth larvae and the other half were destructively sampled for chemical analysis. Tannin content of leaves did not differ significantly among populations but differed significantly among families. Estimates of heritability (h ²) and quantitative genetic differentiation among populations for tannin content (Q _ST) were 0.83 and 0.12, respectively. Defoliation was not related to the tannin content of plants nor to spine and trichome densities of leaves, although positive family–mean associations were observed between defoliation and both seed weight and plant height (P < 0.003). Among the oak populations, differential increase in larval weight gain with defoliation was observed. Leaf tannin content in Q. ilex is genetically controlled but does not influence defoliation or predict performance of the larvae. Different efficiencies of food utilisation depending on the oak genotypes indicate that other plant traits are influencing the feeding patterns and fitness of L. dispar and consequent population dynamics.     

Do litter-mediated plant-soil feedbacks influence Mediterranean oak regeneration? A two-year pot experiment

Background & Aims

Oak seedling establishment is difficult and may be partly explained by litter-mediated interactions with neighbors. Litter effects can be physical or chemical and result in positive or negative feedback effects for seedlings. Mediterranean species leaves contain high levels of secondary metabolites which suggest that negative litter effects could be important.

Methods

Seedlings of Quercus ilex and Quercus pubescens were grown for two years in pots with natural soil and litter inputs from 6 Mediterranean woody species, artificial litter (only physical effect) or bare soil.

Results

Litter types had highly different mass loss (41–80%), which correlated with soil organic C, total N and microbial activity. Litter of Q. pubescens increased soil humidity and oak seedlings aerial biomass. Litters of Cotinus coggygria and Rosmarinus officinalis, containing high quantities of phenolics and terpenes respectively, decomposed fast and led to specific soil microbial catabolic profiles but did not influence oak seedling growth, chemistry or mycorrhization rates.

Conclusions

Physical litter effects through improved soil humidity seem to be predominant for oak seedling development. Despite high litter phenolics content, we detected no chemical effects on oak seedlings. Litter traits conferring a higher ability to retain soil moisture in dry periods deserve further attention as they may be critical to explain plant-soil feedbacks in Mediterranean ecosystems.

     

Refoliation of deciduous canopy trees following severe insect defoliation: comparison of <Emphasis Type="Italic">Fagus crenata</Emphasis> and <Emphasis Type="Italic">Quercus crispula</Emphasis>

Deciduous trees can survive severe defoliation by herbivores and often refoliate in the same season. Refoliation following severe defoliation represents compensatory regrowth to recover foliage biomass. Although the relationship between defoliation intensity and degree of refoliation at the individual level has been quantified following artificial defoliation for saplings and small trees, no study has examined the relationship for canopy trees and interspecific differences in this relationship. In this study, defoliation by gypsy moths in an outbreak year and subsequent refoliation were visually surveyed for canopy trees of Fagus crenata (n?=?80) and Quercus crispula (n?=?113) in central Japan. Defoliation and refoliation estimates were scored in 10% classes as the ratio to foliage present before defoliation. The degree of refoliation and the proportion of refoliated trees were high in severely defoliated trees. For 60 and 100% defoliated trees, respective refoliations were 2 and 66% for F. crenata, and 37 and 88% for Q. crispula. All of the 90 and 100% defoliated trees refoliated. These results indicate that severely defoliated trees show an increased need for refoliation to maintain metabolism. Beta regression analysis showed that Q. crispula possessed higher refoliation capability than F. crenata. This is likely associated with the relatively large storage reserves and recurrent growth flush pattern of oak species, which are strong characteristics of oaks and adaptive for response to herbivory and catastrophic disturbances. Interspecific differences in refoliation capability may exert differential effects on forest ecosystem processes, such as influencing the growth of understory species.     

Influence of genetic variation of oak trees as a nutrient substrate adaption of the pea green oak leaf-roller

The influence of the genetic variation of the DNA (RAPD polymerase chain reaction, primer OPA-14) of two oak species (Quercus pubescens L. and Q. petraea L.) on the variation of certain important fitnesslinked traits of the imago of the pea green oak leaf-roller (Tortrix viridana L.) in different classes of genotypes and allozyme loci is studied. The results obtained demonstrate that pea green oak leaf-roller individuals of the same genotype class may possess maximal fitness (a component associated with fecundity and body size) to trees of one genotype and minimal fitness to trees of another genotype. The interaction of the two factors, oak genotype—pea green oak leaf-roller genotype, leads to the appearance of links between the genotype classes of the leaf-roller and the oak tree. The results obtained are discussed from the point of view of a new area of research, community or ecosystem genetics, a field that has only recently developed.     

Geographic patterns of genetic variation in nuclear and chloroplast genomes of two related oaks (<Emphasis Type="Italic">Quercus aliena</Emphasis> and <Emphasis Type="Italic">Q. serrata</Emphasis>) in Japan: implications for seed and seedling transfer

In this study, we assessed geographic patterns of genetic variations in nuclear and chloroplast genomes of two related native oaks in Japan, Quercus aliena and Q. serrata, in order to facilitate development of genetic guidelines for transfer of planting stocks for each species. A total of 12 populations of Q. aliena and 44 populations of Q. serrata were analyzed in this study. Genotyping of nuclear microsatellites in Q. aliena was done with only nine populations (n = 212) due to limited numbers of individuals in two populations, while all 12 populations (n = 89) were used in sequencing chloroplast DNA (cpDNA). In Q. serrata, 43 populations (n = 1032) were genotyped by nuclear microsatellite markers, while cpDNA of 44 populations (n = 350) was sequenced. As anticipated, geographic patterns detected in the variations of Q. aliena’s nuclear genome and its chloroplast haplotype distribution clearly distinguished northern and southern groups of populations. However, those of Q. serrata were inconsistent. The geographic distribution of its chloroplast haplotypes tends to show the predicted differentiation between northern and southern lineages, but geographic signals in the genetic structure of its nuclear microsatellites are weak. Therefore, treating northern and southern regions of Japan as genetically distinct transferrable zones for planting stocks is highly warranted for Q. aliena. For Q. serrata, the strong NE-SW geographic structure of cpDNA should be considered.     

Holocene vegetation and fire history of the mountains of Northern Sicily (Italy)

Knowledge about vegetation and fire history of the mountains of Northern Sicily is scanty. We analysed five sites to fill this gap and used terrestrial plant macrofossils to establish robust radiocarbon chronologies. Palynological records from Gorgo Tondo, Gorgo Lungo, Marcato Cixé, Urgo Pietra Giordano and Gorgo Pollicino show that under natural or near natural conditions, deciduous forests (Quercus pubescens, Q. cerris, Fraxinus ornus, Ulmus), that included a substantial portion of evergreen broadleaved species (Q. suber, Q. ilex, Hedera helix), prevailed in the upper meso-mediterranean belt. Mesophilous deciduous and evergreen broadleaved trees (Fagus sylvatica, Ilex aquifolium) dominated in the natural or quasi-natural forests of the oro-mediterranean belt. Forests were repeatedly opened for agricultural purposes. Fire activity was closely associated with farming, providing evidence that burning was a primary land use tool since Neolithic times. Land use and fire activity intensified during the Early Neolithic at 5000 bc, at the onset of the Bronze Age at 2500 bc and at the onset of the Iron Age at 800 bc. Our data and previous studies suggest that the large majority of open land communities in Sicily, from the coastal lowlands to the mountain areas below the thorny-cushion Astragalus belt (ca. 1,800 m a.s.l.), would rapidly develop into forests if land use ceased. Mesophilous Fagus-Ilex forests developed under warm mid Holocene conditions and were resilient to the combined impacts of humans and climate. The past ecology suggests a resilience of these summer-drought adapted communities to climate warming of about 2 °C. Hence, they may be particularly suited to provide heat and drought-adapted Fagus sylvatica ecotypes for maintaining drought-sensitive Central European beech forests under global warming conditions.     

Effects of plant hybridization on the structure and composition of a highly rich community of cynipid gall wasps: the case of the oak hybrid complex <Emphasis Type="Italic">Quercus magnoliifolia</Emphasis> x <Emphasis Type="Italic">Quercus resinosa</Emphasis> in Mexico

The richness and composition of herbivore communities can be influenced by the genetic variation of host plants. Hybrid plant populations are ideal to test these effects because they usually harbor high genetic variation and display a mosaic of phenotypic characters. The goal of this study was to examine the effect of hybridization between two Mexican white oaks, Q. magnoliifolia and Q. resinosa, on the composition and diversity of the associated cynipid gall wasp community. We used eight nuclear microsatellite markers to genotype 150 oak individuals sampled at three different altitudes at the Tequila volcano and conducted monthly samplings of galls in each individual over the course of 2 years. A Bayesian assignment analysis indicated genetic admixture between the two oak species at the study site and allowed classifying individuals as Q. magnoliifolia, Q. resinosa or hybrids. Gall morphospecies richness was significantly higher in the hybrids, intermediate in Q. magnoliifolia and lower in Q. resinosa. Overall, 48 different gall morphospecies were found, with 21 of them being shared among the three groups of plants, 13 between two groups of plants, and 14 were unique to one group of plants, with eight of these being found in hybrids. Several of the shared galls showed differences in abundance among plant groups. Therefore, genetic structure in this oak complex significantly influences the diversity and composition of the associated gall wasp community, and hybrid individuals are probably acting as potential sinks and bridges for the colonization of plant hosts by these highly specialized insect species.     

Leaf functional trait responses to changes in water status differ among three oak (<Emphasis Type="Italic">Quercus</Emphasis>) species

We monitored differences in rates of foliar carbon-compound increases with progressive drought as an indicator of sink limitation status and subsequent drought tolerance. We postulate that species which increase foliar carbohydrates and protein-precipitable phenolics (PPP) more quickly than related species over the same time period and drought conditions have stronger sink limitations and are therefore less drought tolerant. Quercus macrocarpa, Q. shumardii, and Q. virginiana saplings were subjected to two treatments for approximately 3.5 months: (1) watered, which received the equivalent of average weekly precipitation for College Station, TX, USA, and (2) droughted, in which precipitation was reduced by 100%. Q. virginiana’s photosynthesis (A) and stomatal conductance (g_s) were 44 and 54% greater, respectively, than the other species in the drought treatment. Q. virginiana’s g_s also increased more dramatically with watering and subsequent increases in predawn leaf water potential. This plasticity suggests Q. virginiana is best equipped to deal with sporadic rainfall events and soil moisture changes, at least in the short term. Results indicate that the three species allocate carbon from photosynthate in different ways. Q. shumardii had the most soluble sugar in its foliage but had the least PPP, while Q. virginiana and macrocarpa had more PPP and less sugar than Q. shumardii. Diameter:height growth rate was greatest in Q. shumardii. Foliar protein-precipitable phenolic content appears to be more affected by factors other than drought. Differences in species’ physiological responses to drought may result in stand composition shifts with future climate alterations.     

Microhabitat affects acorn removal in three sympatric and endangered Neotropical oak species

Acorn removal and predation are processes that can influence forest dynamics and the ecological niche segregation of sympatric oak species. Different factors affect these processes, including differences in acorn germination rate and exposure to predators and/or dispersers. This study evaluated acorn removal and predation patterns in three threatened tropical cloud forest oak species (Quercus germana, Quercus sartorii and Quercus cortesii). Acorns were placed in two accessibility treatments (open to all potential acorn consumers vs. accessible to mice only) and in two types of microhabitat (covered by trunks, shrubs and herbaceous plants vs. uncovered). In addition, acorn germination rate was evaluated in a greenhouse. After 130 days, 76.67 ± 2.45 % of the seeds had been removed and the two accessibility treatments did not differ significantly. Mice were therefore shown as important predators and/or dispersers of acorns. Removal was greater in the covered (93.33 ± 2.04 %) compared to the uncovered (60.00 ± 4.01 %; P < 0.05) microhabitat. Acorn removal and germination were highest for Q. germana (82.00 ± 3.86 %, 91.67 ± 4.41 %, respectively), followed by Q. sartorii (79.00 ± 4.09 %; 50.00 ± 7.64 %) and Q. cortesii (69.00 ± 4.64 %; 13.33 ± 4.41 %); the same trend was recorded in the acorn germination rate (P < 0.05). Our findings suggest that uncovered sites with partial shade might function as regeneration microhabitats where less acorn removal and higher germination occur. The implications of differential acorn trait preferences by rodents for the coexistence of these oak species are discussed.     

A novel set of single-copy nuclear gene markers in white oak and implications for species delimitation

Oaks have often been the focus of research on plant evolution owing to their propensity to intercross and their important role in ecology and economy. Compared with traditional molecular markers, such as amplified fragment length polymorphisms (AFLPs) and simple sequence repeats (SSRs), multiple single-copy nuclear genes (SCNGs) are of greater utility in inferring evolutionary processes in oaks. Nineteen primer pairs were developed from expressed sequence tags (ESTs) of Quercus mongolica and Q. robur that could produce orthologous products in Chinese white oaks (section Quercus). These SCNG markers showed a moderate to high level of nucleotide polymorphism in 42 individuals of two closely related white oaks, Q. mongolica and Q. liaotungensis, and demonstrated high transferability across seven white oaks, four oaks from section Cerris, and one oak from section Lobatae. A phylogenetic tree based on these SCNGs provided resolution at deep nodes and robust support for delimiting populations of Q. mongolica and Q. liaotungensis; Bayesian analysis clustered individuals into their respective species with high probability and no admixture. When the same individuals were used, Bayesian clusters based on either 194 AFLPs or 19 SSRs gave comparable results, but one or several individuals respectively were identified as having admixed ancestry. This indicates that the hybridization rate between these two oaks may have been overestimated using SSR markers due to the occurrence of homoplasy. The SCNGs are powerful for species delimitation of white oaks, and these markers could be useful for future phylogenetics and phylogeography research in white oaks.