Tree ring anatomy indices of Pinus tabuliformis revealed the shifted dominant climate factor influencing potential hydraulic function in western Qinling Mountains

Trees can adjust xylem anatomical structure related with potential hydraulic functions to cope with climate variability. We therefore need a better understanding of how climate variability constrains wood anatomy and tree radial growth. Pinus tabuliformis dominates natural forests and plantations over the western Qinling Mountains, which is one of the ecologically vulnerable areas in China. Here, we investigated the response of P. tabuliformis tree-ring anatomical structure to climate variability by applying wood anatomy analysis, and evaluated the influences of anatomical traits on potential hydraulic functions and the climate significance of intra-annual density fluctuations (IADFs). We found that with the increasing temperature from spring to summer, the negative effect of temperature on the formation and enlargement of earlywood and transition-wood tracheids was gradually enhanced. However, spring precipitation not only had a direct and positive influence on the formation of earlywood, but also had a delaying impact on the transition-wood cell enlargement. Besides, the smaller earlywood tracheid size of P. tabuliformis could be a substantially characteristic reflecting spring drought. The contribution of lumen diameter on conduit wall reinforcement was dominated in earlywood, while the contribution of cell wall thickness was greater than that of lumen diameter in latewood. The different contributions of anatomical traits on conduit wall reinforcement would further affect the response of potential hydraulic function to climate. IADFs of P. tabuliformis could be a potential indicator to reflect the abnormal summer precipitation events in the western Qinling Mountains. IADFs with strong and weak intensity indicated years with high and low rates of change in mid-summer precipitation, respectively. Future warmer and drier climate in the western Qinling Mountains will likely result in the production of smaller tracheids to ensure hydraulic safety, which means the stronger drought resistant of P. tabuliformis in the future. In this study, we linked the xylem anatomy and potential hydraulics functions with intra-seasonal climate variability in the context of climate warming and drying, and proposed some xylem anatomical indices reflecting potential drought events.     

Fish and fisheries in hot water: What is happening and how do we adapt?

Rapid climate changes are currently driving substantial reorganizations of marine ecosystems around the world. A key question is how these changes will alter the provision of ecosystem services from the ocean, particularly from fisheries. To answer this question, we need to understand not only the ecological dynamics of marine systems, but also human adaptation and feedbacks between humans and the rest of the natural world. In this review, we outline what we have learned from research primarily in continental shelf ecosystems and fishing communities of North America. Key findings are that marine animals are highly sensitive to warming and are responding quickly to changes in water temperature, and that such changes are often happening faster than similar processes on land. Changes in species distributions and productivity are having substantial impacts on fisheries, including through changing catch compositions and longer distances traveled for fishing trips. Conflicts over access to fisheries have also emerged as species distributions are no longer aligned with regulations or catch allocations. These changes in the coupled natural-human system have reduced the value of ecosystem services from some fisheries and risk doing so even more in the future. Going forward, substantial opportunities for more effective fisheries management and operations, marine conservation, and marine spatial planning are likely possible through greater consideration of climate information over time-scales from years to decades.     

Spatial and temporal factors associated with nest survival of Gray Flycatchers in managed ponderosa pine forests

Gray Flycatchers (Empidonax wrightii) breed in a variety of habitats in the arid and semi‐arid regions of the western United States, but little is known about their breeding biology, especially in the northern portion of their range where they nest in ponderosa pine (Pinus ponderosa) forests. From May to July 2014 and 2015, we conducted surveys for singing male Gray Flycatchers along the eastern slope of the Cascade Range in Washington, U.S.A, monitored flycatcher nests, and quantified nest‐site vegetation. We used a logistic‐exposure model fit within a Bayesian framework to model the daily survival probability of flycatcher nests. During the 2 yr of our study, we monitored 141 nests, with 93% in ponderosa pines. Mean clutch size was 3.6 eggs and the mean number of young fledged per nest was 3.2. Predation accounted for 90% of failed nests. We found a positive association between daily nest survival and both nest height and distance of nest substrates from the nearest tree. Flycatchers that locate their nests higher above the ground and further from adjacent trees may be choosing the safest alternative because higher nests may be less exposed to terrestrial predators and nests in trees that are farther from other trees may be less exposed to arboreal predators such as jays (Corvidae) that may forage in patches with connected canopies. Nests in trees farther from other trees may also allow earlier detection of approaching predators and thus aid in nest defense.     

Group versus population level demographics: An analysis of comparability using long term data on wild white‐faced capuchin monkeys (Cebus capucinus imitator)

Primates have long been used as indicator species for assessing overall ecosystem health. However, area‐wide census methods are time consuming, costly, and not always feasible under many field conditions. Therefore, it is important to establish whether monitoring a subset of a population accurately reflects demographic changes occurring in the population at large. Over the past 35 years, we have conducted 15 area‐wide censuses in Sector Santa Rosa, Costa Rica. These efforts have revealed important trends in population growth patterns of capuchin monkeys following the protection and subsequent regeneration of native forests. During this same period, we have also intensively studied a subset of the capuchin groups. Comparing these two datasets, we investigate whether the population structures of the closely monitored groups are reliable indicators of area‐wide demographic patterns. We compare the overall group size and the individual age/sex class compositions of study groups and nonstudy groups (i.e., those contacted during area‐wide censuses only). Our study groups contained more individuals overall with a larger proportion of infants, and there were indications that the proportion of adult and subadult males was lower. These differences can be ascribed either to sampling errors or real differences attributable to human presence and/or better habitat quality for the study groups. No other sex/age classes differed, and major demographic changes were simultaneously evident in both study and nonstudy groups. This study suggests that the Santa Rosa capuchin population is similarly impacted by large‐scale ecological patterns observable within our study groups.     

Co‐occurrence patterns of trees along macro‐climatic gradients and their potential influence on the present and future distribution of Fagus sylvatica L.

Aim During recent and future climate change, shifts in large‐scale species ranges are expected due to the hypothesized major role of climatic factors in regulating species distributions. The stress‐gradient hypothesis suggests that biotic interactions may act as major constraints on species distributions under more favourable growing conditions, while climatic constraints may dominate under unfavourable conditions. We tested this hypothesis for one focal tree species having three major competitors using broad‐scale environmental data. We evaluated the variation of species co‐occurrence patterns in climate space and estimated the influence of these patterns on the distribution of the focal species for current and projected future climates. Location Europe. Methods We used ICP Forest Level 1 data as well as climatic, topographic and edaphic variables. First, correlations between the relative abundance of European beech (Fagus sylvatica) and three major competitor species (Picea abies, Pinus sylvestris and Quercus robur) were analysed in environmental space, and then projected to geographic space. Second, a sensitivity analysis was performed using generalized additive models (GAM) to evaluate where and how much the predicted F. sylvatica distribution varied under current and future climates if potential competitor species were included or excluded. We evaluated if these areas coincide with current species co‐occurrence patterns. Results Correlation analyses supported the stress‐gradient hypothesis: towards favourable growing conditions of F. sylvatica, its abundance was strongly linked to the abundance of its competitors, while this link weakened towards unfavourable growing conditions, with stronger correlations in the south and at low elevations than in the north and at high elevations. The sensitivity analysis showed a potential spatial segregation of species with changing climate and a pronounced shift of zones where co‐occurrence patterns may play a major role. Main conclusions Our results demonstrate the importance of species co‐occurrence patterns for calibrating improved species distribution models for use in projections of climate effects. The correlation approach is able to localize European areas where inclusion of biotic predictors is effective. The climate‐induced spatial segregation of the major tree species could have ecological and economic consequences.     

Deep intra‐island divergence of a montane forest endemic: phylogeography of the Puerto Rican frog Eleutherodactylus portoricensis (Anura: Eleutherodactylidae)

Aim Hypotheses proposed for lineage diversification of tropical montane species have rarely been tested within oceanic islands. Our goal was to understand how basin barriers and Pleistocene climatic fluctuations shaped the distribution of diversity in Eleutherodactylus portoricensis (Eleutherodactylidae), a frog endemic to the montane rain forests of Puerto Rico. Location The north‐eastern (Luquillo) and south‐eastern (Cayey) mountains of Puerto Rico. Methods We generated mitochondrial DNA (mtDNA) control region sequences (c. 565 bp) from 144 individuals of E. portoricensis representing 16 localities, and sequenced 646 bp of cytochrome b and 596 bp of nuclear DNA (nDNA) rhodopsin exon and intron 1 from a subset of individuals. We conducted a phylogenetic analysis on the mtDNA sequence data and explored population substructure with maximum parsimony networks, a spatial analysis of molecular variance, and pairwise F_ST analysis. Coalescent simulations were performed to test alternative models of population divergence in response to late Pleistocene interglacial periods. Historical demography was assessed through coalescent analyses and Bayesian skyline plots. Results We found: (1) two highly divergent groups associated with the disjunct Luquillo and Cayey Mountains, respectively; (2) a shallow mtDNA genetic discontinuity across the La Plata Basin within the Cayey Mountains; (3) phylogeographic congruence between nDNA and mtDNA markers; (4) divergence dates for both mtDNA and nDNA pre‐dating the Holocene interglacial (c. 10 ka), and nDNA suggesting divergence in the penultimate interglacial (c. 245 ka); and (5) historical demographic stability in both lineages. Main conclusions The low‐elevation Caguas Basin is a long‐term barrier to gene flow between the two montane frog populations. Measures of genetic diversity for mtDNA were similar in both lineages, but lower nDNA diversity in the Luquillo Mountains lineage suggests infrequent dispersal between the two mountain ranges and colonization by a low‐diversity founder population. Population divergence began prior to the Holocene interglacial. Stable population sizes over time indicate a lack of demonstrable demographic response to climatic changes during the last glacial period. This study highlights the importance of topographic complexity in promoting within‐island vicariant speciation in the Greater Antilles, and indicates long‐term persistence and lineage diversification despite late Pleistocene climatic oscillations.