Identity and genetic structure of the photobiont of the epiphytic lichen Ramalina menziesii on three oak species in southern California

Lichens, a classic example of an obligate symbiosis between fungi and photobionts (which could be algae or cyanobacteria), are abundant in many terrestrial ecosystems. The genetic structure of the photobiont population found in association with a lichen-forming fungal species could be affected by fungal reproductive mode and by the spatial extent of gene flow in the photobiont. Using DNA sequences from one nuclear ribosomal and two chloroplast loci, we analyzed the genetic structure of the photobiont associated with the fungus Ramalina menziesii at an oak woodland study site in southern California. We had previously shown that the fungus exhibited no genetic structure among four local sites or three phorophyte species. Our goals were to identify the photobiont species and assess its genetic structure. We found that R. menziesii was highly specific in its photobiont choice and associated with one alga, Trebouxia decolorans. In contrast to the fungal population, we found significant differentiation among the algae sampled on three oak species and little genetic structure among the sites for two of the three algal loci. We hypothesize that R. menziesii is locally adapted to the phorophyte species through habitat specialization in the algal partner of the symbiosis.     

Intestinal length of three California pinniped species

Forty-eight intestinal tracts, extracted from both sexes of California sea lions, Harbour seals and Northern elephant seals, were measured. The majority of intestinal tracts were removed from stranded animals that died from various causes. The sea lions and elephant seals, approximately equal in size, were larger than the Harbour seals. All species possess a small intestine which is significantly longer than even the entire gastrointestinal tract of herbivores of comparable size. Elephant seal small intestines, averaging approximately 25 times the seal's body length, were considerably longer than the small intestines of either sea lions (averaged more than 18 times the body length) or Harbour seals (averaged nearly 16 times the body length). However, the large intestines of elephant seals were shorter than either of the other two species. Among the sea lions and Harbour seals the large intestines were approximately equal in length. Sea lions and Harbour seals also showed a close correlation between standard length and total intestinal length. Among elephant seals these two parameters showed greater variability. The functional significance of the extremely long small intestine remains unclear. Certainly, the large body mass and high energy requirements of these animals has contributed to the development of a long intestinal tract. It also appears likely that diet and the high motility rate of digesta influenced the intestinal development. Comparatively, the significantly shorter large intestine of elephant seals probably relates to this species' remarkable capabilities in water conservation and metabolic water retention.     

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.     

The cork oak tree in California

There are 5,000 trees in various parts of the State, planted at various times, and recent experimental strippings of the largest have yielded 600 to 1,000 pounds of high quality cork per tree. Does this presage an American cork industry?     

Conservation genetics of three flightless beetle species in southern California

Regional scale conservation decisions can be aided by information on the distribution of intraspecific diversity, especially the extent to which patterns are common to multiple species. We compare patterns of intraspecific mitochondrial cytochrome oxidase I (COI) variation among three flightless beetles (Coleoptera: Tenebrionidae: Nyctoporis carinata LeConte; Staphylinidae: Sepedophilus castaneus (Horn); Carabidae: Calathus ruficollis Dejean) in the southern part of the California Floristic Province biodiversity hotspot. All species exhibit moderate to high levels of total variation, ranging from 2% to 10% (maximum uncorrected distance). Most populations of all species exhibit unique haplotypes, but few populations’ haplotypes constitute exclusive clades. Many adjacent pairs of populations show indications of some, though limited, genetic connectedness, due either to gene flow or ancestral polymorphism. However, in most cases this diminishes sharply over greater distances. By both statistical and phylogenetic measures, Sierra Nevadan populations are highly distinct from those in the coast and transverse ranges. Among the latter, the eastern transverse ranges are generally most unique and isolated, with diversity in the western parts of these ranges showing fewer barriers. Otherwise, few measures agree on areas of highest conservation value, and overall patterns tend to be species-specific.     

Patterns of intra- and interspecific association in leaf-mining insects on three oak host species

Abstract. 1. We determined mortality and distributional patterns of leaf miners on three oak host species (Quercus falcata, Q.nigra and Q.hemisphaerica) in northern Florida, U.S.A.
2. Patterns of intra- and interspecific occurrence within leaves, and mortality of five most abundant leaf miner species were analysed as a test of competition.
3. Miners co-occurred on leaves more often that expected by chance (P<0.05) in six of ten possible species combinations and log-linear model analysis showed no negative higher-order interactions.
4. All five miner species had highly clumped distributions between leaves (P<0.01).
5. Leaf miner survival was less than expected for four of five species when co-occurring on leaves with conspecifics than when mining with heterospecifics or alone (P<0.05).
6. We conclude that interspecific competition is unapparent within this leaf miner guild and that intraspecific competition occurs in four of the five major leaf miner species. We discuss leaf miner selection of common leaves, perhaps based on chemical/physical leaf characters, as a cause of intra- and interspecific aggregation.     

Different ability of three Mediterranean oak species to tolerate progressive water stress

Inter-comparisons in the gas exchange patterns and root characteristics under both well-watered and drought conditions were done in three-years-old seedlings of three oak species (Quercus cerris L., Q. frainetto Ten., and Q. ilex L.) growing in controlled environment. Well-watered Q. cerris had greater physiological performances than other oaks, but under drought it was not able to face the water stress showing also structural modifications such as reduction of root length and average diameter. On the other hand, Q. ilex maintained root growth both in drought or well-watered soils. Moreover, it was able to keep open stomata also under water stress, although stomatal conductance (g _s) was low. Q. frainetto had an intermediate position in regard to its physiological and root structural characteristics between Q. cerris and Q. ilex under drought stress. For all oaks the relationship between g _s and the ratio of sub-stomatal and ambient CO₂ concentration (C _i/C _a) highlighted the dynamic adaptation of g _s to the increase of hydraulic resistances of leaf, stem, and roots portions, more evident during the air humidity change and progressive soil dehydration. This suggests a well-triggered above-and under-ground mechanism to endure the drought stress.     

Seed size and recruitment limitation influence seedling establishment in three tallgrass prairie species

A seed size–seed number tradeoff predicts that large numbers of seeds have an establishment advantage under low levels of competition, while large seed size is advantageous under asymmetric competition. Testing these predictions in the context of tallgrass prairie restoration should increase predictability of outcomes of species composition—restoration technique combinations. I conducted field and greenhouse experiments comparing seedling establishment among three tallgrass prairie species with different seed mass-seed number combinations, but with similar mass of seeds sown. Species were prairie dock [Silphium terebinthinaceum, mass = 33.2 + 2.1 mg ( \(\overline{x}\)  + SE, n = 100)], wild quinine (Parthenium integrifolium, mass = 3.1 + 0.3 mg), and smooth blue aster (Symphyotrichum laeve var. laeve, mass = 0.53 + 0.02 mg). Seeds were sown into mowed or tilled plots with shade and mulch treatments in an old field in northeastern Illinois USA, and seeds were sown into containers with or without vegetative cover in a greenhouse. In mowed plots, species with larger numbers of seeds sown had higher seedling densities. In tilled plots, seedling densities of the large-seeded Silphium were reduced less by shade than the small-seeded Parthenium. Symphyotrichum, however, did not respond to treatments as expected based on its seed size. High relative growth rate possibly increased Symphyotrichum seedling establishment in competitive environments. Results of this study demonstrated recruitment limitation when seedlings established into existing vegetation, and suggest that species composition resulting from specific seeding rates during prairie restoration may be more predictable when species are interseeded into existing vegetation, than when seeds are sown into tilled fields.     

Effects of seed size on the survival of insect- infested acorns in three oak species

种子内的寄生昆虫可以严重影响种子的发育、损害种子活力.种子足余策略理论认为大种子有利于抵御和适应昆虫寄生取食,但动物最优觅食理论推测,大种子更易遭受昆虫寄生.为对这两种对立观点进行验证,本实验以青冈、苦槠和麻栎各2个种群的种子为材料,对昆虫寄生与完好种子间的体积和萌发率进行比较,并对寄生种子萌发率与种子体积的关系进行了分析.结果显示:(1)在6个种群的种子中,只有松阳麻栎和青冈种群的寄生种子体积大于完好种子,其余4个种群的寄生种子体积小于完好种子,但这种差异不显著;(2)所有寄生种子的整体萌发率(18%)显著低于完好种子(45.66%)(P＜0.001),在不同种群内,寄生种子的萌发率也分别显著低于完好种子.(3)比较同种植物体积差异显著的寄生种子的萌发率发现,大种子总比小种子具有更高的萌发率,但差异不显著;在不同植物的寄生种子间比较时,体积最大的麻栎种子萌发率显著高于体积较小的青冈和苦槠种子.研究结果表明,象虫在种子上产卵时对大种子没有选择偏好,在昆虫寄生取食严重损害种子活力的压力下,大种子比小种子具有更强的耐受力.     

Effects of waterlogging on seed germination of three Mediterranean oak species: Ecological implications

Soil water saturation during prolonged periods of time generates a negative impact on nearly all terrestrial plants. In Mediterranean woodlands, precipitation can be very abundant during the wet season, inducing temporary soil waterlogging, coinciding with the seed dispersal and germination time of many species. We investigated the effects of waterlogging on seed germination and early root growth of three coexisting oak species (Quercus canariensis, Q. suber and Q. pyrenaica), by completely flooding of seeds for various periods of time. The three oak species showed a certain level of tolerance to waterlogging, only being affected those seeds subjected for long periods of submersion (over 30 days). Waterlogging during prolonged periods of time decreased the probability of seed germination in the three oak species, lengthened the time to germination, and hampered root development in two of the studied species. The main differences between oak species occurred in terms of root growth (Q. canariensis being the less affected, and Q. suber the most); these differential responses could be related to a species rank of waterlogging tolerance. Thus inter-specific differences in germination responses to waterlogging could contribute to explain, at least partially, species habitat and distribution patterns across landscapes. Seed mass also played an important role on different aspects of germination, though its relative importance varied as function of species and waterlogging treatment. The tolerance to stress induced by waterlogging increased with seed mass, but only in the case of Q. canariensis.     

Low-temperature limitations of photosynthesis in three tropical Vigna species: A chlorophyll fluorescence study

The temperature-dependence of photosynthesis and chlorophyll (Chl) fluorescence quenching components was studied between 0 and 45°C in three tropical, chilling-sensitive Vigna species and in chilling-tolerant pea. Photosynthesis of the Vigna spp. was approx. 20% more reduced by temperatures between 7 and 30°C than in pea. The latter revealed significant changes in Chl fluorescence parameters at much lower temperature than the Vigna spp. Below 15°C, the reduction state of Q_A increased quickly in pea, while in Vigna already below 30°C, an increase of reduced Q_A was obtained. The analysis of different components of non-photochemical Chl fluorescence quenching (q_N) revealed, that in pea photoinhibitory quenching (q_I) occurred below 13°C. Below ca. 7°C, a sudden breakdown of both q_P and the fast relaxing component of q_N was observed in pea.In Vigna, susceptibility of LHC II phosphorylation or limitation of electron flow by damage to PS I, the PS II reaction centre or the water-splitting system were not responsible for the chilling-sensitivity of photosynthesis between 5 and 30°C. Instead, photosynthesis was gradually limited by an inefficient use of reduction equivalents. This, in turn may increase susceptibilty to photoinhibition, which occurred below 20°C in Vigna. The combined study of q_P and of the different components of q_N allowed the demonstration of the subsequent occurrence of different limiting processes with decreasing temperature in the chilling-sensitive Vigna species.     

Settlement and recruitment of three damselfish species: larval delivery and competition for shelter space

Spatial patterns of settlement and abundance of older life stages were examined for three species of damselfish in the genus Dascyllus by monitoring natural colonization of standard amounts of initially empty juvenile microhabitat (anemones for D. trimaculatus; branching coral for D. flavicaudus and D. aruanus) transplanted to a series of sites within lagoons of Moorea, French Polynesia. Large spatial differences in larval colonization were observed, which were temporally consistent but different among the species. At the whole-island scale, D. trimaculatus settled primarily on the northern shore, while settlement of the other two species was greatest at the southern end. The three species also showed different patterns of settlement within lagoons: D. aruanus settled mainly nearer to shore, D. flavicaudus primarily on offshore lagoon portions and D. trimaculatus colonized equally across the lagoons. Among sites around the island, the relative abundance of older juveniles after 10 months was a curvilinear function of the relative abundance of settlers for two species (D. trimaculatus and D. flavicaudus). There was no relationship between patterns of settlement and abundance of older juveniles for D. aruanus, although juvenile abundance was inversely related to that of juvenile D. flavicaudus. At the within-lagoon scale, settlement mirrored almost exactly the relative abundance of older lifestages of D. trimaculatus and D. flavicaudus, whereas there was just a qualitative match for D. aruanus. A competition experiment revealed that juvenile D. flavicaudus had a greater effect on population growth of D. aruanus than vice versa, and this mechanism helped explain why the modification of settlement patterns was greatest in D. aruanus. Interspecific variation in abundance of older stages was shaped to differing extents by both patterns of larval delivery and subsequent density-dependent processes involving competition for shelter space. Received: 9 April 1998 / Accepted: 6 August 1998     

Presence of triploids among oak species

BACKGROUND AND AIMS: Polyploids, organisms that have multiple sets of chromosomes, are common in certain plant and animal taxa. However, there are only a few reports of intraspecific ploidy variation within the genus Quercus. The aim of the study was to investigate the suspected ploidy level of two oaks that have unusual microsatellite banding patterns. METHODS: Polyploidy was investigated by using microsatellite analysis, stomata length measurements and nuclear DNA content estimation by flow cytometry. KEY RESULTS: Each putative triploid tree has patterns of microsatellite variation unexpected for diploid genomes, with up to three alleles at some loci, significantly longer stomata and 1.5 times more DNA per nucleus compared with diploids. CONCLUSIONS: To our knowledge, this report contains the first evidence for triploidy in Q. petraea and confirmation of this phenomenon in Q. robur. Regardless of the positive or negative aspects of the presence of triploid oaks in forest stands, it is of value to be able to screen for them. This study demonstrates that nuclear microsatellites and estimation of DNA content by flow cytometry can readily be used for this purpose.     

Seed dispersal of three sympatric oak species by forest rodents in the Qinling Mountains, Central China

Forest rodents play an essential role as seed dispersal vectors through their caching behaviors. Using seeds of Quercus aliena, Q. glandulifera, and Cyclobalanopsis engleriana (Fagaceae), which are dominant, but poorly studied species, in the Qinling Mountains, Central China, we investigated seed predation and dispersal by forest rodents in 2010 and 2011. There were significant differences in rodent seed-eating and caching strategies among the three tree species. Seeds of Q. aliena and C. engleriana had hard coats, high nutrition contents (e.g., protein, fat, and starch), and long germination schedules (C. engleriana only). They were less frequently eaten in situ, but more likely to be eaten after removal or cached. Seeds of Q. glandulifera had soft coats and low nutrition contents and were more often eaten in situ and less likely to be eaten after removal or cached. Our findings indicated that forest rodents were primarily responsible for seed predation and dispersal of these three tree species in the Qinling Mountains, and seed traits, especially coat hardness, nutrition content, and germination schedule, were important factors influencing rodent eating and caching behaviors. In addition, seed dispersal process of each tree species differed significantly between the 2 years, reflecting the effect of mast seeding on the eating and caching strategies of forest rodents.     

Response of ants and spiders to prescribed fire in oak woodlands of California

Conservation managers of oak woodlands have been reintroducing fire both as an ecological process per se and to assist in restoring native plant communities. To increase our understanding of the impacts of reintroduced fire on ground-dwelling invertebrates we examined the response of ants and spiders to a late season (autumn) prescribed fire conducted in a blue oak (Quercus douglasii) woodland ecosystem in northern California. Twelve 100 m × 100 m plots were established, six plots received a burn treatment and the remaining six plots were unburned controls. Ants and spiders were sampled using pitfall traps left open continuously and collected approximately every 32 days. Sampling was conducted over a year, consisting of four pre-burn and nine post-burn collections. Abundance was analyzed using a repeated measures ANOVA, which showed seed-harvester ants decreased significantly in the two months following the fire. Total spider abundance also showed a significant decrease in two months, although this did not occur immediately after the burn. One spider hunting guild, the ‘diurnal ambush’ group (Thomisidae) remained suppressed for up to nine months. Correspondence analysis measures of ant species abundance with environmental and vegetation variables (percent rock, bare ground, plant species richness and height of herbaceous vegetation) were higher than expected by chance, which assists in explaining some of the responses. Findings from this study revealed that the reintroduction of autumn burns has modest and short-term effect on the invertebrates sampled, suggesting that late season fires are compatible with other conservation goals for oak woodland ecosystems.     

Demography, reproduction, and dormancy along altitudinal gradients in three intermountain Allium species with contrasting abundance and distribution

Little is known about the variation in demographics, flower number, fruit set, and summer dormancy in Allium species native to the Intermountain West region of the United States. The purpose of this study was to investigate demographic patterns, summer dormancy traits, and variation in reproductive characteristics among habitats. Three populations of each of three species, Allium acuminatum, A. brandegei, and A. passeyi, were studied along an altitudinal gradient in northern Utah, USA, from 2004 to 2006. Demographic data were collected from individuals in permanent plots established in each population. Individual flowering plants were periodically monitored and used to calculate reproductive characteristics. Leaf area measurements throughout the 2005 growing season and soil temperature sensors were used to assess the relationship between habitat and dormancy characteristics. Populations of the widely distributed species, A. acuminatum and A. brandegei, were dominated by individuals in seedling and flowering stages while the restricted A. passeyi had populations containing a majority of individuals in the post-seedling, but non-flowering stage-class. There was a strong directional trend in A. acuminatum reproductive traits, with flower number and fruit set decreasing with increasing elevation. The mid-elevation A. brandegei populations were reproductively more successful than the high and low-elevation populations. The high-elevation A. passeyi population had more flowers per plant and higher fruit set in comparison to the lower elevation populations. The onset of summer dormancy as indicated by the timing of leaf senescence, was associated with high soil temperatures specific to each species. In general, the timing of leaf senescence was later in higher elevation populations in all species. A smaller proportion of non-flowering individuals in A. acuminatum and A. brandegei may indicate a high seedling mortality rate or a shorter juvenile phase in comparison to A. passeyi. The A. passeyi populations exhibit demographic characteristics of rare taxa; low seed production and low seedling recruitment. The high number of non-flowering plants in A. passeyi likely includes many reproductively mature individuals which are influenced by the unique habitat and environment of this species. Temperature is likely the key environmental cue inducing summer dormancy in all three species.     

Avian hemosporidian parasites from northern California oak woodland and chaparral habitats

During spring-summer 2003-2004, the avian community was surveyed for hemosporidian parasites in an oak (Quercus spp.) and madrone (Arbutus spp.) woodland bordering grassland and chaparral habitats at a site in northern California, a geographic location and in habitat types not previously sampled for these parasites. Of 324 birds from 46 species (21 families) sampled (including four species not previously examined for hemosporidians), 126 (39%) were infected with parasites identified as species of one or more of the genera Plasmodium (3% of birds sampled), Haemoproteus (30%), and Leucocytozoon (11%). Species of parasite were identified by morphology in stained blood smears and were consistent with one species of Plasmodium, 11 species of Haemoproteus, and four species of Leucocytozoon. We document the presence of one of the parasite genera in seven new host species and discovered 12 new parasite species-host species associations. Hatching-year birds were found infected with parasites of all three genera. Prevalence of parasites for each genus differed significantly for the entire sample, and prevalence of parasites for the most common genus, Haemoproteus, differed significantly among bird families. Among families with substantial sample sizes, the Vireonidae (63%) and Emberizidae (70%) were most often infected with Haemoproteus spp. No evidence for parasite between-genus interaction, either positive or negative, was found. Overall prevalence of hemosporidians at the northern California sites and predominance of Haemoproteus spp. was similar to that reported in most other surveys for the USA, Canada, and the Caribbean islands.     

Seasonal variation in leaf chemistry of the coast live oak Quercus agrifolia and implications for the California oak moth Phryganidia californica

Summary The perennial foliage of the California coast live oak (Quercus agrifolia Nee) permits herbivores to feed on this oak species throughout the year. Patterns of herbivory for a two-year period on Q. agrifolia were observed in relation to seasonal and age-related changes in the nutritional and defensive characteristics of leaves. Nitrogen and phosphorus contents were higher in new leaves compared to mature foliage. Structural compounds (e.g., cellulose) in leaves rapidly increased with age. Concentrations of tatal phenolics (Folin-Denis) and astringency were higher in new foliage, and concentrations of condensed tannins gradually increased as the leaves matured. Peaks of herbivore damage were observed in June and in September–October, and were caused by outbreaks of the California oak moth (Phryganidia californica). P. californica, a bivoltine oak specialist, exhibited feeding preferences in June for old leaves over emerging leaves, and showed no preferences for leaf classes in September. These results suggest that P. californica is adapted to survive on nutritionally poor foliage and to circumvent quantitative defenses such as condensed tannins.