Individual Growth Rates Research Articles

Population connectivity of the swordtip squid Uroteuthis edulis between southern Japan and northern Taiwan using statolith trace elemental analysis

Uroteuthis edulis (Hoyle, 1885) is an Indo-Pacific squid species widely distributing in the western Pacific, and commercially important especially in Japan and Taiwan. It has been suggested that some individuals are possibly transported from the spawning ground in north Taiwan to the coasts of Japan, however, the strength of population connectivity between those areas and its influence on U. edulis population dynamics were unveiled. To understand the U. edulis population connectivity in this area, the correlations between statolith trace elements and abiotic/biotic factors were examined first, and then squid experienced environments were postulated throughout their entire life cycle. Sr/Ca ratio showed a strongly negative correlation with ambient water temperature but no correlation with individual growth rate, suggesting that Sr/Ca ratio can be used to reflect squid experienced temperatures. Most squid caught in the Sea of Japan hatched in the areas having similar water temperature with where Taiwanese squid hatched, that would be off the north Taiwan or even warmer area. Statolith trace elements successfully distinguished the catch locations but not the hatching grounds, implying that hatching grounds of Japan and Taiwan squid were largely overlapped. Thus, we suggest that there is strong population connectivity of U. edulis population between southern Japan and northern Taiwan. As there was no clear evidence for existence of local population hatched in the Sea of Japan in this study, U. edulis population might display a source-sink population dynamics, that is, population in Taiwanese waters and/or further south as the source, and the one in the Sea of Japan as a sink population. As U. edulis should be considered as a metapopulation, collaboration among countries in the northwestern Pacific is required for sustainable fishery management of this species.

Centurial Variation in Size at Maturity of Eastern Baltic Cod (Gadus morhua) Mirrors Conditions for Growth.

The status of Eastern Baltic cod (EBC) Gadus morhua has remained poor despite low fishing mortality for over a decade, including a fishing ban since 2019. Although the decline in productivity can be explained by lower individual growth and survival rates, other aspects of life-history changes such as maturation patterns for EBC has so far not been sufficiently explored. According to current stock assessments, the median size at maturity (L 50) has halved from 40 to around 20 cm in total length since the 1990s, while the overall size distribution has become increasingly truncated. It has previously been suggested that changes in L 50 can be attributed to both fishing-induced evolution and phenotypic plasticity induced by growth rates. However, since L 50 is currently occurring around 20 cm, the maturation process must have been initiated at much smaller sizes, that is, long before the fish could be caught in the dominant trawl fishery at around 35 cm. In this study, we aimed to further investigate what drivers may have led to reduced productivity in EBC by determining variations in size at sexual maturity in longer time series than has been done before (1930s to 1980s) and include prey productivity and quality. We found that L 50 declined already in the 1930s and thereafter remained stable at around 40 cm up to the 1990s. On a centurial perspective, L 50 has been positively correlated to growth potential (L 95), length diversity, total stock biomass, total catch and yield per recruit, while Fulton's condition factor was not related to L 50. Our results suggest that the links between life-history parameters and external drivers are complex, but the present unprecedented early onset of maturity and hence decline in L 50 since the 1990s signals a decline in growth potential, which also has hampered the productivity of EBC.

Optimizing feed restriction strategies for profitable Oreochromis niloticus culture in floating cages in riverine ecosystems

High feed cost is a major obstacle for promoting the growth of nutrient-rich fish species like Nile tilapia (Oreochromis niloticus) in cage aquaculture. To address this issue, cage farming of O. niloticus was studied for a 75-day period in the Gurukchi River of Bangladesh. Three different feeding strategies (FS) were tested in floating cages: FS5- weekly restriction on feed supply for two days, FS6- weekly restriction on feed supply for one day, and FS7- no weekly restriction on feed supply, with three replications for each treatment. Water quality parameters were monitored weekly and found within suitable levels for fish cultivation. The analysis of length–weight relationship and the condition factor of O. niloticus showed positive allometric growth regardless of the diverse feeding tactics employed that consistently exhibit stability across all treatments. Both FS6 and FS7 had significantly higher (p < 0.05) final individual length, final individual weight, net yield, total yield, and specific growth rate than FS5. FS6 yielded significantly higher fish production with significantly lower feed conversion ratio than FS7. Economic analysis revealed the highest benefit–cost ratio and net revenue in FS6, recommending its use to minimize the need for supplemental feed and reduce production costs in tilapia cage culture.

Migratory-derived resources induce elongated food chains through middle-up food web effects

BackgroundSeasonal movements of animals often result in the transfer of large amounts of energy and nutrients across ecosystem boundaries, which may have large consequences on local food webs through various pathways. While this is known for both terrestrial- and aquatic organisms, quantitative estimates on its effects on food web structure and identification of key pathways are scarce, due to the difficulty in obtaining replication on ecosystem level with negative control, i.e. comparable systems without migration.MethodsIn this study, we estimate the impact of Arctic charr (Salvelinus alpinus) migration on riverine ecosystem structure, by comparing multiple streams with strictly resident populations above natural migration barriers with streams below those barriers harboring partially migratory populations. We compared density estimates and size structure between above and below populations. Diet differences were examined through the analysis of stomach contents, changes in trophic position were examined by using stable isotopes. To infer growth rate of resident individuals, back-growth calculation was performed using otoliths.ResultsWe find higher densities of small juveniles in partially migratory populations, where juvenile Arctic charr show initially lower growth, likely due to higher intraspecific competition. After reaching a size, where they can start feeding on eggs and smaller juveniles, which are both more frequent in partially migratory populations, growth surpasses that of resident populations. Cannibalism induced by high juvenile densities occurred almost exclusively in populations with migration and represents an altered energy pathway to the food web. The presence of large cannibalistic charr feeding on smaller ones that have a similar trophic level as charr from strictly resident populations (based on stomach content) coupled with steeper δ15N-size regression slopes illustrate the general increase of food chain length in systems with migration.ConclusionsOur results thus suggest that the consumption of migration-derived resources may result in longer food chains through middle-up rather than bottom-up effects. Furthermore, by occupying the apex of the food chain and feeding on juvenile conspecifics, resident individuals experience reduced competition with their young counterparts, which potentially balances their fitness with migratory individuals.

Nanostructured Surfaces Enhance Nucleation Rate of Calcium Carbonate.

Nucleation and growth of calcium carbonate on surfaces is of broad importance in nature and technology, being essential to the calcification of organisms, while negatively impacting energy conversion through crystallization fouling, also called scale formation. Previous work studied how confinements, surface energies, and functionalizations affect nucleation and polymorph formation, with surface-water interactions and ion mobility playing important roles. However, the influence of surface nanostructures with nanocurvature-through pit and bump morphologies-on scale formation is unknown, limiting the development of scalephobic surfaces. Here, it is shown that nanoengineered surfaces enhance the nucleation rate by orders of magnitude, despite expected inhibition through effects like induced lattice strain through surface nanocurvature. Interfacial and holographic microscopy is used to quantify crystallite growth and find that nanoengineered interfaces experience slower individual growth rates while collectively the surface has 18% more deposited mass. Reconstructions through nanoscale cross-section imaging of surfaces coupled with classical nucleation theory-utilizing local nanocurvature effects-show the collective enhancement of nano-pits.

The space occupation and use by tree crowns explain variations of individual growth rates in an old-growth temperate forest in Japan

Relative growth rates (RGR), i.e., growth rates per unit biomass (ΔM/M, where M is plant mass and ΔM is the change in M over a period of time), reflect growth strategies of plant species. Partitioning of RGR to net assimilation rate (ΔM/leaf area) and leaf area ratio (leaf area/M) provides further insights into allocation strategies. To apply this analytical approach to large canopy tree species, we used crown area (Ac) as a proxy for leaf area to understand variations of RGR partitioned to space use efficiency (SUE, ΔM/Ac) and space occupation efficiency (SOE, Ac/M). With UAV imagery, we measured Ac of 226 co-occurring individuals of 14 canopy tree species in a 1-ha stand in a temperate old-growth mixed-forest in Japan, and analyzed how RGR was related to SUE and SOE. The results show that deciduous species exhibited higher SOE and lower SUE compared to evergreen species, even though their RGR values largely overlapped. Late successional species tended to have higher RGR through higher SUE than early-to-middle successional species. We also analyzed the relationship of absolute growth rates (AGR) with several functional traits including DBH (diameter at breast height), Ac, leaf- and stem traits. Both Ac and DBH were strong determinants of AGR across species. Low specific leaf area (SLA, leaf area per unit leaf mass) and high wood density positively contributed to AGR across species, offering long-term growth advantages for old-growth natural forest. The analytical framework introduced in this study may be useful to elucidate the variation of tree growth strategies of canopy trees in natural forest stands.

Optimising height-growth predicts trait responses to water availability and other environmental drivers.

Future changes in climate, together with rising atmospheric , may reorganise the functional composition of ecosystems. Without long-term historical data, predicting how traits will respond to environmental conditions-in particular, water availability-remains a challenge. While eco-evolutionary optimality theory (EEO) can provide insight into how plants adapt to their environment, EEO approaches to date have been formulated on the assumption that plants maximise carbon gain, which omits the important role of tissue construction and size in determining growth rates and fitness. Here, we show how an expanded optimisation framework, focussed on individual growth rate, enables us to explain shifts in four key traits: leaf mass per area, sapwood area to leaf area ratio (Huber value), wood density and sapwood-specific conductivity in response to soil moisture, atmospheric aridity, and light availability. In particular, we predict that as conditions become increasingly dry, height-growth optimising traits shift from resource-acquisitive strategies to resource-conservative strategies, consistent with empirical responses across current environmental gradients of rainfall. These findings can explain both the shift in traits and turnover of species along existing environmental gradients and changing future conditionsand highlight the importance of both carbon assimilation and tissue construction in shaping the functional composition of vegetation across climates.

P-700 Modelling individual follicle growth rates during ovarian stimulation in medically assisted reproduction cycles to enable prediction of final follicle profiles

Abstract Study question Can the growth of individual follicles during ovarian stimulation in medically assisted reproduction (MAR) cycles be modelled to enable prediction of final follicle profiles? Summary answer Mean follicle growth rate is 1.35 mm per day. Our model reliably forecasts follicle size profiles on the final scan within ±2mm with 75.1% accuracy. What is known already Follicle growth rates during ovarian stimulation are believed to be linear with various mean growth rates reported between 1 to 4 mm per day. Follicles are believed to grow faster during ovarian stimulation than in the natural menstrual cycle. The change in mean follicle size was 1.69 mm per day with ovarian stimulation in 131 MAR cycles, and 1.4 mm per day in 50 natural cycles. However, there are only very limited data using individual follicle sizes to model follicle growth to enable prediction of future follicle size profiles. Study design, size, duration We conducted a retrospective cohort study of 12,950 patients from 11 European clinics (2005-2023). First IVF/ICSI cycles with at least three follicles and two scans were analysed. Using 8,564 cycles with scans one or two days apart, 98,029 follicles were modelled to estimate follicle growth rates per day. Stratification by age, weight, total antral follicle count (AFC), initial FSH dose, and suppressant protocol was performed. Predictive modelling was conducted using 39,698 scans including 434,082 follicles. Participants/materials, setting, methods Assessment of Follicle Growth: Follicles were ranked and the difference in corresponding follicle sizes over consecutive scans estimated, and the impact of baseline characteristics evaluated. Prediction of follicle size profile on final scan: A kernel density estimator and random forest model were developed using the same training data. Both approaches estimated future follicle growth from the initial scan. The two predictions were combined using maximum-likelihood adjustments. Generalisation error was estimated using independent test data. Main results and the role of chance The mean growth rate of individual follicles was 1.350 mm per day (95% CI 1.346 – 1.353 mm per day), which was lower than the previously reported mean follicle growth rate during ovarian stimulation (1.7 mm per day). The large number of patient-cycles and follicles assessed enabled a precise estimate of follicle growth per day during ovarian stimulation. Age, total AFC, initial FSH dose, bodyweight, and suppressant protocol had no statistically significant effect on the estimated mean growth rate. Using only the follicle sizes from the initial scan during ovarian stimulation, our model had 75.1% accuracy for predicting follicle sizes on the final scan within ±2mm. Including follicle size data from the first two scans improved the accuracy of the model to predict the follicle sizes on the final scan to 80.4%. In a confirmatory analysis, we cross-validated our findings across each of 11 individual clinics, and similar estimates for the generalisation error as for the standard test/train split were maintained, suggesting suitable generalisability of these findings. Limitations, reasons for caution A key simplifying assumption in this study is that follicles demonstrate monotonic growth patterns. Specifically, the relative ordering of follicle sizes is preserved over the entire cycle. This assumption enables straightforward extraction of growth statistics from the observed data but assumes that follicles do not regress in size. Wider implications of the findings We have used a large high-quality dataset, allied to advanced modern machine learning techniques, to precisely estimate follicle growth rates during ovarian stimulation, and use this to reliably predict future follicle size profiles during ovarian stimulation. This supports the design, personalisation, streamlining and success of future assisted conception cycles. Trial registration number None

Foraminiferal detoxification breakdown induced by fatal levels of TiO2 nanoparticles

The increase discharge of titanium dioxide (TiO2) nanoparticles, derived from engineered material waste, exerts a detrimental impact on both the marine ecosystem and public health. The cytotoxicity of TiO2 nanoparticles on marine organisms should be imperatively understood to tackle the urgent concern for the well-being of marine life. Various concentrations of TiO2 nanoparticles have proven to reach fatal levels in aquatic organisms, requiring a deeper exploration of cytotoxicity. Notably, certain benthic foraminifers, such as Ammonia veneta, have been identified as capable of incorporating TiO2 nanoparticles into vesicles. However, these organisms exhibit a detoxification mechanism through exocytosis, as indicated by previous transcriptomic inferences. This presents the advantage of assessing the tolerance of foraminifers to TiO2 nanoparticles as pollutants and investigating the long-term effects of cytotoxicity. In this study, we scrutinized the distribution of TiO2 nanoparticles within cells and the growth rates of individuals in seawater media containing 1, 5, 10, and 50 ppm TiO2 nanoparticles, comparing the results with a control group over a 5-week period, utilizing A. veneta stain. Transmission electron microscopy observations consistently revealed high concentrations of TiO2 nanoparticles in vesicles, and their expulsion from cells was evident even with exposure to 5 ppm TiO2 nanoparticles. Under the control and 1 ppm TiO2 conditions, foraminifers increased their cell volume by adding a calcification chamber to their tests every 1 or 2 days. However, the 5-week culturing experiments demonstrated that foraminifers gradually ceased growing under 5 ppm TiO2 nanoparticle exposure and exhibited no growth at &amp;gt; 10 ppm concentrations, despite an ample food supply. Consequently, these findings with A. veneta suggest that the foraminiferal detoxification system could be disrupted by concentrations exceeding 5 ppm of TiO2 nanoparticles. The toxic effect of TiO2 nanoparticles on meiofauna, such as benthic foraminifers, have been poorly understood, though these organisms play an important role in the marine ecosystem. Environmental accumulation of TiO2 nanoparticles on the coast has already exceeded twenty times more than foraminiferal detoxification level. Future studies focusing on toxic mechanism of TiO2 nanoparticles are crucial to prevent the breakdown of the marine ecosystem through accelerating discharge of TiO2 nanoparticles into the ocean.

La Rana or El Rana : Dual Language Learners' Grammatical Variability in Narrative Retells

Purpose: This longitudinal study investigated the trajectory of Spanish article accuracy in Spanish–English dual language learners (DLLs) from preschool to first grade, addressing the need for longitudinal data on the variability of Spanish grammatical skills in DLLs in English immersion classrooms. Method: Language sample analysis was conducted on 336 Spanish and English narrative retells elicited from 31 Spanish–English DLLs (range: 45–85 months). Growth curve models captured within- and between-individual change in article accuracy from the beginning of preschool to the end of first grade. Results: As a group, DLLs did not exhibit significant positive or negative growth in Spanish article accuracy over time. On average, article accuracy remained stable at 76% from preschool throughout first grade. Participants exhibited significant variability in article accuracy that was partly explained by changes in Spanish proficiency. Spanish article accuracy was lower for DLLs with lower Spanish proficiency indexed by measures from the Spanish language samples, while English proficiency indexed by the English language samples did not affect Spanish article accuracy. Conclusions: These findings suggest that expectations for Spanish grammatical performance in DLLs need to be adjusted to account for the possible impact of not receiving Spanish support in English immersion school settings. DLLs in these instructional programs do not exhibit article accuracy at a level expected for monolingual Spanish speakers. Significant individual differences in both individual status and growth rates of Spanish article accuracy highlight the broad variability in Spanish language skills of DLLs in the United States.

Effect of gestational diabetes on fetal growth rate and later overweight in the offspring.

Children of women with gestational diabetes (GDM) are often born with a higher birthweight and have an increased risk of overweight during childhood. High fetal growth rate is also associated with being overweight in childhood. To examine excessive fetal growth rate as a mediator between GDM and overweight in the offspring. This was a longitudinal cohort study, using routinely collected data on children born 2008-2014 in Aarhus, Denmark. Fetal biometrics were extracted from the patient records at Aarhus University Hospital and childhood weight from the health records at Aarhus Municipality Healthcare Service. We calculated growth trajectories for fetuses affected by GDM and for unaffected fetuses using cubic mixed model regression. We extracted individual fetal growth rate and estimated the contributing effect of fetal growth rate on the risk of being overweight in the 5-9 year-old offspring. We included 6794 mother-child pairs, 295 with GDM. Fetal growth was higher in women with GDM from week 25, and the offspring had an increased risk of being overweight (OR: 2.02 (95%CI: 1.44 - 2.84)). When adjusting for fetal growth rate in week 28 the effect attenuated by 15%, and to 1.10 (95%CI: 0.76 - 1.60) when further adjusting for pre-pregnancy BMI. Pregnancies affected by GDM had higher fetal growth rate and the offspring had a higher risk of being overweight at 5-9 years. Fetal growth rate in early third trimester was a mediator of up to 15% of this association, but pre-pregnancy BMI contributed strongly as well.

Heterogeneity and wage growth of full-time workers in Japan: An empirical analysis using micro data

In this paper we examine the driving forces of fluctuations in wage growth of full-time workers in Japan, taking into account the heterogeneity of wage structures among the workers and using micro data including those from the Basic Survey on Wage Structure. To this end, we first divide full-time workers into two classes with distinct wage structures, based on a finite mixture model estimated using various characteristics of the workers and the firms they work for. We find that the two classes correspond to what previous studies have called an "internal labor market," where labor is reallocated within firms and wages follow a seniority-based system under long-term employment practices, and an "external labor market," where labor moves across firms and wages are mainly determined by supply and demand factors in the market. We next analyze the effects of economic factors on individual full-time workers' wage growth rates. We show that in the internal labor market, neither labor market conditions at the industry and firm-size level nor the output gap at the macro level have influenced the wage growth rates in recent years at least until 2021, while higher potential growth has increased them. By contrast, in the external and the overall labor markets for full-time workers, improvements in labor market conditions and the output gap have accelerated the wage growth rates, even in recent years.

Increased eye size is favoured in Trinidadian killifish experimentally transplanted into low light, high competition environments.

Intraspecific variation in vertebrate eye size is well known. Ecological factors such as light availability are often correlated with shifts in relative eye size. However, experimental tests of selection on eye size are lacking. Trinidadian killifish (Anablepsoides hartii) are found in sites that differ in predation intensity. Sites that lack predators are characterized by lower light, high killifish densities, low resource availability, and intense competition for food. We previously found that killifish in sites that lack predators have evolved a larger "relative" eye size (eye size corrected for body size) than fish from sites with predators. Here, we used transplant experiments to test how selection operates on eye size when fish that are adapted to sites with predators are translocated into sites where predators are absent. We observed a significant "population × relative eye size" interaction; the relationship between relative eye size and a proxy for fitness (rates of individual growth) was positive in the transplanted fish. The trend was the opposite for resident fish. Such results provide experimental support that larger eyes enhance fitness and are favoured in environments characterized by low light and high competition.

Effects of growing season and individual growth rates on the occurrence of larval overwintering in Otton frog tadpoles

AbstractThe timing and size of metamorphosis are crucial for the future fitness of organisms with complex life cycles, such as amphibians. In some amphibian species, a portion of tadpoles will metamorphose in their natal year whereas others from the same cohort overwinter as tadpoles. Low temperature and food availability were previously assumed to be the underlying reasons; however, the factors influencing the decision to overwinter as tadpoles or metamorphose in the natal year have not been extensively studied. This study investigated these factors by conducting laboratory‐rearing experiments on Babina subaspera tadpoles. The tadpoles were individually reared under controlled temperature and light conditions that simulated five different growing seasons (i.e., the start month) observed in the field. Four different food quantity levels were set to induce different growth rates, which were measured individually. The results revealed that 33 tadpoles metamorphosed within their natal year, whereas 52 tadpoles were overwintered as tadpoles and metamorphosed the following spring. The size at metamorphosis was larger in tadpoles that metamorphosed after winter than in those that metamorphosed before winter. Whether tadpoles metamorphosed before or after winter was influenced by the individual growth rate and growing season. Tadpoles with slower growth rates were more likely to metamorphose after winter, possibly because slower growth prevented them from reaching the critical size threshold required for metamorphosis before winter. The threshold for the occurrence of larval overwintering varied with the growing season; tadpoles that spawned later in the year were more likely to overwinter, even with a high growth rate. The results suggested that slow‐growing B. subaspera tadpoles with insufficient time until the onset of winter would gain a higher fitness by metamorphosing after winter. This would be advantageous due to the tadpoles' potentially high survival rate during dormancy as well as their larger size at metamorphosis in the following year.

Relationships between diameter growth and functional wood anatomy in Eucalyptus globulus clones

Aim of study: We aimed to 1) analyze the variability of wood hydraulic anatomical traits in 10 clones of E. globulus Labill. with different growth rates, and 2) determine whether the magnitude of diameter growth affects the relationships between anatomical variables and diameter at breast height (DBH). Area of study: 25-year-old common garden trial in Balcarce, Buenos Aires, Argentina. Material and methods: We measured vessel diameter and number per unit area in transverse histological sections of stem wood, and calculated the proportion of vessel lumens, vessel composition (S), and theoretical specific hydraulic conductivity (Ks) of 10 E. globulus clones of high (HG) and low (LG) mean growth rates (measured as DBH) under field conditions. Main results: There was a difference in the range of variability in hydraulic anatomy between HG and LG clones, with LG clones showing a wider range. HG clones had wood with larger and fewer vessels and higher S compared to LG clones, with similar Ks between both growth groups. No clear or strong trends were observed between wood anatomy and DBH within the HG and LG groups, but across all clones a high correlation (Spearman coefficient r; p&lt;0.001) was observed between vessel number ‒ DBH (r= -0.68), and S ‒ DBH (r= 0.74). These correlations were driven by contrasting mean values of both growth groups. Research highlights: Commercial E. globulus clones present a relatively large variation in anatomical and hydraulic strategies. However, in contrast to what is postulated for various woody species, there was no clear relationship between theoretical hydraulic efficiency and individual diameter growth rate in the genotypes studied.

Empirical and model‐based evaluation of a step‐pool stream restoration project: Consequences for a highly valued fish population

AbstractObjectiveWe sought to measure a step‐pool restoration project's effects on a steelhead Oncorhynchus mykiss population and explore the capability of process‐based modeling to enhance understanding of the results.MethodsWe used before‐after–control‐impact monitoring in combination with a process‐based, individual‐based, spatially explicit fish population model to evaluate a stream restoration project that reconfigured the channel and primarily added step pools to a reach of a second‐order stream in northwestern California.ResultFive years of monitoring both before (2012–2016) and after (2018–2022) restoration indicated that restoration caused substantial increases in the abundance and biomass of steelhead. Individual growth rates and retention of fish in the study reach did not exhibit consistent patterns, even in the first 2 years after restoration, when fish abundance and biomass exhibited extreme increases of about fivefold. Model simulations predicted about a twofold increase in the abundance and biomass of steelhead in the restoration reach, which corresponded with the empirical results 4–5 years after restoration. The model also predicted a similar increase in the production of steelhead out‐migrants, a response we did not attempt to measure in the field.ConclusionStep‐pool restoration benefitted steelhead. The model's correspondence with empirical observations indicates its potential applicability to more complex resource management questions in the study area, such as how restoration will combine with changes in climate to affect the sustainability of salmonid populations.

Assessing the hydromechanical control of plant growth.

Multicellular organisms grow and acquire their shapes through the differential expansion and deformation of their cells. Recent research has addressed the role of cell and tissue mechanical properties in these processes. In plants, it is believed that growth rate is a function of the mechanical stress exerted on the cell wall, the thin polymeric layer surrounding cells, involving an effective viscosity. Nevertheless, recent studies have questioned this view, suggesting that cell wall elasticity sets the growth rate or that uptake of water is limiting for plant growth. To assess these issues, we developed a microfluidic device to quantify the growth rates, elastic properties and hydraulic conductivity of individual Marchantia polymorpha plants in a controlled environment with a high throughput. We characterized the effect of osmotic treatment and abscisic acid on growth and hydromechanical properties. Overall, the instantaneous growth rate of individuals is correlated with both bulk elastic modulus and hydraulic conductivity. Our results are consistent with a framework in which the growth rate is determined primarily by the elasticity of the wall and its remodelling, and secondarily by hydraulic conductivity. Accordingly, the coupling between the chemistry of the cell wall and the hydromechanics of the cell appears as key to set growth patterns during morphogenesis.

Invasive freshwater snails are less sensitive to population density than native conspecifics.

Understanding how and why some species or lineages become invasive is critically important for effectively predicting and mitigating biological invasions. Here, we address an important unanswered question in invasion biology: do key life-history traits of invasive versus native lineages within a species differ in response to key environmental stressors? We focus on the environmental factor of population density, which is a fundamental characteristic of all populations, and investigate how changes in density affect native versus invasive Potamopyrgus antipodarum (New Zealand mudsnail). P. antipodarum has invaded 39 countries and detrimentally affects invaded environments. Previous studies of native and invasive populations and from laboratory experiments have demonstrated that growth and reproduction of P. antipodarum is sensitive to population density, though whether and how this sensitivity varies across native versus invasive lineages remains uncharacterized. We quantified individual growth rate and reproduction in P. antipodarum from multiple distinct native and invasive lineages across three different population density treatments. The growth of native but not invasive lineages decreased as density increased. There was no differential effect of density treatment on embryo production of invasive versus native snails, but a significantly higher proportion of snails were reproductive in high density compared to intermediate density for invasive lineages. In native lineages, there were no significant differences in the relative frequency of reproductive snails across density treatments. While the extent to which these results from our laboratory study can be extrapolated to the more complex natural world remain unclear, our findings are consistent with a scenario where differential sensitivity to population density could help explain why some lineages become successful invaders. Our findings also align with previous studies that show that invasive P. antipodarum lineages exhibit a relatively wide range of tolerance to environmental stressors.

Structural and Successional Dynamics of Old-Growth Mixed Oak Forests in the West Qinling Mountains

Understanding the composition and structure of forest trees is crucial to comprehending the properties and functions of forests. It also helps in implementing effective management strategies for sustainable resource utilization. Our study analyzed the structural dynamics of the old-growth mixed oak forests in the Xiaolongshan Forest region, focusing on three long-term monitoring plots (A, B, C). We examined the tree species composition, diameter distribution, mortality, and recruitment dynamics of different successional species groups, as well as the spatial distribution patterns of living and dead trees, with surveys conducted every five years. The findings indicate: (1) Plot A experienced a decline in stand density and species diversity during the survey period, with the Importance Value Index (IVI) of pioneer successional species continually decreasing in plots B and C. (2) The tree diameter distribution structure in plot A significantly differed from other plots, showing notable change between 2007 and 2012. (3) All plots exhibited lower, well-balanced community-level demographic parameters based on stem number, but a higher recruitment rate for later successional species groups based on basal area. (4) Dead individuals in plot A had a slight clustering distribution, while the other plots showed a random distribution. We conclude that the individual growth rate significantly impacts the dynamics of the natural Quercus aliena var. acuteserrata forest, with pioneer species groups being gradually replaced by early or late-successional species groups in the succession process.

A flash in the pan? The population dynamics of a dominant pioneer species in tropical dry forest succession

AbstractGlobally, around half of all tropical forests are secondary communities which are recovering from previous disturbances. In these communities, dominant pioneers play a critical role in the successional dynamics due their ability to modify the environment, and thus to facilitate or hinder the performance of other species. In this study, we examined the population dynamics of the dominant pioneer species, Mimosa acantholoba var. eurycarpa, in a tropical dry forest during the process of secondary succession. We collected data from permanent plots over a period of 13 years and used integral projection models to analyze the vital rates and changes in population size. Most vital rates were negatively related to successional age, with resprouting, survival and recruitment of individuals responding more strongly, and individual growth rate more weakly. These vital‐rate trends translated into significant variation of population size over succession, with a maximum size at year four and a rapid decline thereafter. Overall, our findings suggest that this species benefits from its ability to display a large number of resprouts in very early stages of succession, contributing to the rapid increase in population density. However, as succession unfolds, a lack of resprouting and a decline in survival reduce its population size, to the point of local extinction. These results highlight the importance of resprouting in the early dynamics of tropical dry forest communities recovering from disturbance.