Maximum Population Growth Rate Research Articles

Diatom abundance in the polar oceans is predicted by genome size.

A principal goal in ecology is to identify the determinants of species abundances in nature. Body size has emerged as a fundamental and repeatable predictor of abundance, with smaller organisms occurring in greater numbers than larger ones. A biogeographic component, known as Bergmann's rule, describes the preponderance, across taxonomic groups, of larger-bodied organisms in colder areas. Although undeniably important, the extent to which body size is the key trait underlying these patterns is unclear. We explored these questions in diatoms, unicellular algae of global importance for their roles in carbon fixation and energy flow through marine food webs. Using a phylogenomic dataset from a single lineage with worldwide distribution, we found that body size (cell volume) was strongly correlated with genome size, which varied by 50-fold across species and was driven by differences in the amount of repetitive DNA. However, directional models identified temperature and genome size, not cell size, as having the greatest influence on maximum population growth rate. A global metabarcoding dataset further identified genome size as a strong predictor of species abundance in the ocean, but only in colder regions at high and low latitudes where diatoms with large genomes dominated, a pattern consistent with Bergmann's rule. Although species abundances are shaped by myriad interacting abiotic and biotic factors, genome size alone was a remarkably strong predictor of abundance. Taken together, these results highlight the cascading cellular and ecological consequences of macroevolutionary changes in an emergent trait, genome size, one of the most fundamental and irreducible properties of an organism.

Adequate nutrient intake mitigate the toxic effects of bromate on the rotifer Brachionus calyciflorus.

Bromate is receiving increased attention as a typical disinfection by-product in aquatic environments, but bromate toxicity tests on invertebrate such as Brachionus calyciflorus rotifer are inadequate. In the present study, the long-term toxicity tests on B. calyciflorus were performed during 21 days under the exposure of different bromate concentrations and two algal density conditions. Furthermore, we evaluated the feeding behaviors of the rotifers under the impact of bromate. The maximum population density of rotifers was significantly reduced at 100 and 200 mg/L bromate exposure at the two algal density conditions. However, we observed that the maximum population density and population growth rate of rotifers were higher at 3.0 × 106 cells/mL algal density than those at 1.0 × 106 cells/mL under the same conditions of bromate exposure. These results suggest that higher food density may have alleviated the negative effects of bromate on rotifers. Meanwhile, the ingestion rate at an algal density of 3.0 × 106 cells/mL was higher than that at 1.0 × 106 cells/mL. The present study provides a basic reference to comprehensively evaluate the toxic effects of bromate on aquatic organisms.

Extrapolation of Metal Toxicity Data for the Rotifer Brachionus calyciflorus Using an Individual-Based Population Model.

Ecological risk assessment (ERA) of metals typically starts from standardized toxicity tests, the data from which are then extrapolated to derive safe concentrations for the envisioned protection goals. Because such extrapolation in conventional ERA lacks ecological realism, ecological modeling is considered as a promising new approach for extrapolation. Many published population models are complex, that is, they include many processes and parameters, and thus require an extensive dataset to calibrate. In the present study, we investigated how individual-based models based on a reduced version of the Dynamic Energy Budget theory (DEBkiss IBM) could be applied for metal effects on the rotifer Brachionus calyciflorus. Data on survival over time and reproduction at different temperatures and food conditions were used to calibrate and evaluate the model for copper effects. While population growth and decline were well predicted, the underprediction of population density and the mismatch in the onset of copper effects were attributed to the simplicity of the approach. The DEBkiss IBM was applied to toxicity datasets for copper, nickel, and zinc. Predicted effect concentrations for these metals based on the maximum population growth rate were between 0.7 and 3 times higher in all but one case (10 times higher) than effect concentrations based on the toxicity data. The size of the difference depended on certain characteristics of the toxicity data: both the steepness of the concentration-effect curve and the relative sensitivity of lethal and sublethal effects played a role. Overall, the present study is an example of how a population model with reduced complexity can be useful for metal ERA. Environ Toxicol Chem 2024;43:324-337. © 2023 SETAC.

The ten-million-year explosion: Paleocognitive reconstructions of domain-general cognitive ability (G) in extinct primates

The correlation between primate “Big G” scores and brain volume in 68 extant species was employed to estimate probable G values for an additional 68 extinct and 1 extant species with endocranial volume data, employing phylogenetic bracketing. Three different methods were used to generate bracketed estimates, which all showed high convergence. The average of these G estimates (for the extinct primates) coupled with the values from the extant species were found to correlate strongly with neurocognitive measures of both extant and extinct primate taxa, specifically Transfer Index scores (an indicator of cognitive flexibility) and the neuroanatomical covariance ratio (a measure of neural integration). Ancestral character reconstruction incorporating G values was made possible with a phylogenetic tree containing data on the relationships among extant and extinct primates. Negative correlations were found between G and branch length, indicating that higher-G species do not persist as long as lower-G ones, consistent with the presence of the grey-ceiling effect (brain mass negatively predicts maximum population growth rate, and therefore a heightened vulnerability to extinction). Cladogenesis rates were also positively associated with G. Both associations were robust to models that controlled for false positive rates. Comparative models revealed that G evolved in extinct and extant primates in a punctuated pattern. The biggest increase in G occurred after the split between the members of the tribes Hominini and Gorillini 10 million years ago. Hence at the macroevolutionary scale, there can be said to have been a “ten-million-year explosion” in primate G leading up to modern humans.

Econometric Methods of Substantiating Steps Aimed at Passing to the Stage of Extended Population Reproduction in Russisa

The article studies approaches to substantiate lines in social and economic policy of Russia aimed at passing to the stage of extended population reproduction, which became possible after revealing econometric methods of dependence of demographic process intensity indicators on living conditions in the country. As such indicators the authors used maximum and standardized rates of population growth depending only on age birth and death factors and net-coefficient of reproduction. Specific features of their content and methods of their estimation were provided, as well as yearly figures of these indicators in Russia in 2000–2020. Options of econometric models were shown that describe regularity of these indicators changeability depending on factors characterizing living conditions in the country. By using factors of indicator flexibility necessary changes in living conditions were roughly estimated, which could provide transition from depopulation to sustainable growth in population in Russia. The authors critically analyzed the results that are characterized by serious discrepancy in indicators assessing necessary positive changes in living conditions needed to overcome the demographic crisis. It was shown that the most trustworthy estimations correspond to the standardized growth rate.

Tropical rays are intrinsically more sensitive to overfishing than the temperate skates

Overfishing, habitat loss, and climate change are driving population declines in many species. Understanding a species' capacity to recover from these and other threats is necessary for prioritising management. The maximum intrinsic rate of population increase (rmax) can be used to compare which species or groups are particularly sensitive to ongoing threats. To investigate global patterns of intrinsic sensitivity of rays and skates (superorder Batoidea), we calculated rmax of 85 species using a modified Euler-Lotka model that accounts for survival to maturity. We examined how rmax varies with body mass, temperature, and depth using an information-theoretic approach through model selection, accounting for phylogenetic non-independence. Although we observed an overall positive relationship between rmax and temperature, we found that warm, shallow-water rays were more intrinsically sensitive to exploitation (lower rmax) than cold, deep-water skates (higher rmax). We hypothesise that this pattern is likely driven by their different reproductive strategies as live-bearing rays have fewer offspring compared to egg-laying skates, and caution that future research should focus on understanding differences in the mortality schedule of juveniles and sub-adults to understand if survival to maturity is comparable. Our findings highlight the high vulnerability of warm, shallow-water ray species to overexploitation and other threats due to their intrinsically low maximum population growth rates. These differences in rmax have conservation implications for our understanding of the geographic patterns in extinction risk, suggesting that tropical rays are more intrinsically sensitive.

An initial assessment of the sustainability of waterbird harvest in the United Kingdom

Abstract There is a need to assess the sustainability of wild bird harvest in the United Kingdom (UK), and more widely, across Europe. Yet, data on populations and harvest sizes are limited. We used a demographic invariant method (DIM) to estimate potential excess growth (PEG) for populations of UK wintering waterbirds and calculated a sustainable harvest index (SHI) for each. We compared this with population trends and conservation classifications (e.g. Birds of Conservation Concern [BoCC]) to assess the sustainability of harvests and the utility of these classifications. Our approach found evidence for potential overharvest of mallard Anas platyrhynchos, Eurasian teal Anas crecca, gadwall Mareca strepera, Canada geese Branta canadensis, greylag geese Anser anser and woodcock Scolopax rusticola. Whether DIM methods predict overharvest is highly dependent on estimates of maximum population growth rates inferring PEG. We found estimates of maximum population growth to be variable across a range of different methods. We found no relationship between SHI and short‐term wintering trends or conservation classification under the UK's BoCC framework. There was however a positive relationship between SHI and long‐term wintering trends. Policy implications. Our results suggest that UK‐based harvest is unlikely to be a major determinant of population trends for the majority of UK overwintering waterbirds, but harvest rates for some species may exceed that required to maintain stationary population growth. The lack of a relationship between conservation classifications and SHI strongly suggests that such conservation classifications are not an appropriate tool for making decisions about harvest management. Instead, our assessment provides the basis for a framework to make evidence‐based decisions on sustainable harvest levels in the face of incomplete data. There is currently no clear policy instrument in the UK to support such a framework via controls on either harvest effort or mortality of waterfowl. We believe such an instrument is urgently needed to ensure the UK can adapt to changing pressures and ensure the sustainable use of our wildlife populations.

Improvement of breeding methods of predatory mites Neoseiulus cucumeris and Transeius montdorensis for biological plant protection

The possibility of breeding of phytoseiid predatory mites Neoseiulus cucumeris and Transeius montdorensis using hardwood sawdust as a substrate and frozen dried fruit mite (Carpoglyphus lactis) as feed was studied. The number of larvae produced by N. cucumeris was 31.5 % lower on frozen feed in sawdust than in the control, while in T. montdorensis it was lower by 47.7 %. The number of individuals surviving to adulthood compared to the control was lower by 28.6 % and 42.9 %, respectively. The maximum daily growth rate of the population was reduced relatively to the control by 3.7 individuals in N. cucumeris, and by 4.5 in T. montdorensis –. On frozen feed in bran, N. cucumeris produced 20.5 % fewer larvae than in the control, T. montdorensis – 35.1 % fewer larvae. The number of individuals surviving to adulthood was reduced by 18.3 % and 35.3 %, respectively, compared to the control. The maximum daily population growth rate was 1.7 individuals lower than in the control in N. cucumeris, and – 3.9 individuals lower in T. montdorensis. On live feed in sawdust, larval production was similar to the control (lower by 1.1 % in N. cucumeris and 14.2 % in T. montdorensis). The number of individuals was reduced relatively to the control by 1.7 % and 14.8 %, respectively. The maximum daily population growth rate in N. cucumeris is slightly lower (by 0.7 individuals) than in the control, and in T. montdorensis it even exceeded the control by 0.6 individuals per day. Our results showed the possibility of using sawdust as a cheaper substrate for breeding of both species of predatory mites and poor performance of the frozen feed compared to the live one.

Life‐history traits and temporal patterns in the incidence of coastal fishes experiencing tropicalization

AbstractClimate change is causing shifts in the geographic distributions of coastal fish species toward higher latitudes. However, local fish communities found in higher latitudes today are not simply those found in lower latitudes in the past because the sensitivity of species to various environmental conditions is different. Responses of fish to environmental conditions differ depending on their life‐history traits such as the maximum population growth rate, age of maturity, and generation time because these traits are constrained by environmental conditions. Here, we investigate associations among temporal patterns in presence–absence (incidence) data, life‐history traits of species, and environmental conditions to elucidate the potential mechanisms behind the effects of climate change on coastal fish communities. In this study, fish monitoring data collected semi‐monthly between 1982 and 2019 from eight major bays in the northwestern Gulf of Mexico were analyzed with generalized additive models. Smooth patterns over seasons and years in the incidence data of 77 species were estimated, and the data were associated with environmental variables. Further, these temporal patterns were associated with the life‐history traits of species. The results show that species that are more common in the summer months (non‐winter spawners) tend to exhibit an increasing trend and that species common during the spring (winter spawners) tend to exhibit a decreasing trend, suggesting the importance of summer conditions in driving tropicalization. Salinity had significant effects on species in general, and longer‐lived species tended to be affected by temperature. These results suggest seasonal differences in the effects of environmental conditions and variation in sensitivity to environmental conditions among different life‐history strategies. These findings represent major steps toward understanding the mechanisms behind the tropicalization of estuarine communities.

Deriving Population Scaling Rules from Individual-Level Metabolism and Life History Traits.

AbstractIndividual metabolism generally scales with body mass with an exponent around 3/4. From dimensional arguments it follows that maximum population growth rate (rmax) scales with a -1/4 exponent. However, the dimensional argument implicitly assumes that offspring size is proportional to adult size. Here, we calculate rmax from metabolic scaling at the level of individuals within size-structured populations while explicitly accounting for offspring size. We identify four general patterns of how rmax scales with adult mass based on four empirical life history patterns employed by groups of species. These life history patterns are determined by how traits of somatic growth rate and/or offspring mass relate to adult mass. One life history pattern-constant adult-to-offspring mass ratio and somatic growth rate independent of adult mass-leads to the classic -1/4 scaling of rmax. The other three life history patterns either lead to nonmetabolic population growth scaling with adult mass or do not follow a power-law relationship at all. Using life history data on five marine taxa and terrestrial mammals, we identify species groups that belong to one of each case. We predict that elasmobranchs, copepods, and mammals follow standard -1/4 power-law scaling, whereas teleost fish and bivalves do not have a pure power-law scaling. Our work highlights how taxa may deviate from the classic -1/4 metabolic scaling pattern of maximum population growth. The approach is generic and can be applied to any taxa.

Abundance and Potential Biological Removal of Common Dolphins Subject to Fishery Impacts in South Australian Waters

Conservation management of wildlife species should be underpinned by knowledge of their distribution and abundance, as well as impacts of human activities on their populations and habitats. Common dolphins (Delphinus delphis) are subject to incidental capture in a range of Australia’s commercial fisheries including gill netting, purse seining and mid-water trawling. The impact these fishery interactions have on common dolphin populations is uncertain, as estimates of abundance are lacking, particularly for the segments of the populations at risk of bycatch and in greater need of protection. Here we used double-observer platform aerial surveys and mark-recapture distance sampling methods to estimate the abundance of common dolphins in 2011 over an area of 42,438 km2in central South Australia, where incidental mortality of common dolphins due to fisheries bycatch is the highest. We also used the potential biological removal (PBR) method to estimate sustainable levels of human-caused mortality for this segment of the population. The estimated abundance of common dolphins was 21,733 (CV = 0.25; 95% CI = 13,809–34,203) in austral summer/autumn and 26,504 in winter/spring (CV = 0.19; 95% CI = 19,488–36,046). Annual PBR estimates, assuming a conservative maximum population growth rate ofRmax= 0.02 and a recovery factor ofFr= 0.5 for species of unknown conservation status, ranged from 95 (summer/autumn) to 120 dolphins (winter/spring), and from 189 (summer/autumn) to 239 dolphins (winter/spring) with anRmax= 0.04. Our results indicate that common dolphins are an abundant dolphin species in waters over the central South Australian continental shelf (up to 100 m deep). Based on the 2011 abundance estimates of this species, the highest estimated bycatch of common dolphins (423 mortalities in 2004/05) in the southern Australian region exceeded the precautionary PBR estimates for this population segment. Recent bycatch levels appear to be below PBR estimates, but low observer coverage and underreporting of dolphin mortalities by fishers means that estimates of dolphin bycatch rates are not robust. The effects of cumulative human impacts on common dolphins are not well understood, and thus we recommend a precautionary management approach to manage common dolphin bycatch based on local abundance estimates.

Prescribed fire has slight influence on Roosevelt elk population dynamics

Prescribed fires often stimulate short-term productivity of grasslands that influences use by large, grazing herbivores. But studies examining burning effects on large herbivore population dynamics while simultaneously considering other environmental factors that might also influence population dynamics are lacking. We examined the influences of burned area, precipitation during the growing season, and possible distributional shifts from a nearby public hunt on maximum intrinsic rate of population growth (rmax) and environmental carrying capacity (K). We examined the influences of these predictors in a Roosevelt elk (Cervus elaphus roosevelti) population studied across 43 years where abundances ranged from 4 to 322 animals and prescribed fires ranged from 14 to 891 ha of burned area in Redwood National and State Parks, California, USA. The highest count across surveys conducted in a year was our index of elk (females, juveniles, subadult males) abundance. We estimated Ricker type models in a hierarchical, state-space formulation that separated observer error from process variation. We found a slight influence from burned area on both rmax and K but a stronger influence from precipitation during the growing season. The lack of a substantial effect from burned area on elk population parameters might be from a variety of factors such as spatial and temporal variation in intensity of prescribed fires and weak density dependence. Nonetheless, one positive benefit to elk population processes was that the patchwork of burning retarded encroachment of woody plants into forage habitat and, thus, maintained a constant area of forage habitat across 43 years.

Puerto Rico plain pigeon, scaly-naped pigeon and red-tailed hawk: population dynamics and association patterns before and after hurricanes

Since the 1980s, 3 major hurricanes have made landfall on Puerto Rico: Hugo in September 1989 (Saffir-Simpson scale, category 4), Georges in September 1998 (category 3) and María in September 2017 (category 4). María was the most devastating hurricane since the 3 major hurricanes that occurred in 1899-�1932. Major hurricanes can cause severe abundance declines and population bottlenecks by decreasing survival and reproductive rates and increasing predation and competition for limited resources. In April to June 1986-2021, we used distance sampling to estimate abundance and monitor the population dynamics of the endangered Puerto Rico plain pigeonPatagioenas inornata wetmoreiand the abundant scaly-naped pigeonP.squamosaand red-tailed hawkButeo jamaicensis. Here, we fit a Bayesian state-space logistic model with distance sampling abundance estimates to generate posterior estimates of maximum population growth rate and population carrying capacity, and predict abundance in April to June 2020-2030. In addition, we usedN-mixture and 2-species models to assess association patterns in April to June 2015-2019. The scaly-naped pigeon and red-tailed hawk populations did not decline, or recovered faster from their declines than the plain pigeon population after the hurricanes. The association patterns between species were positive but variable for the 2 pigeon species and negative but variable for the plain pigeon and red-tailed hawk. At lowered abundance (i.e. mean ± SE estimatesN̂= 1043 ± 476 island-wide andN̂= 522 ± 157 at the centre of abundance in the east-central region in April to June 2018-2021), the plain pigeon may become extinct if another hurricane with the path and intensity of María makes landfall on the island during the current decade.

Life-history, exploitation and extinction risk of the data-poor Baraka's whipray (Maculabatis ambigua) in small-scale tropical fisheries.

The Baraka's whipray (Maculabatis ambigua) is a major constituent of small-scale fisheries catch in the south-western Indian Ocean. Despite this, little is known of its life-history or exploitation status. We provide the first estimates of crucial life-history parameters and the maximum intrinsic population growth rate rmax , using specimens collected from small-scale fisheries landings in Kenya, Zanzibar and Madagascar (with northern Madagascar representing a range extension for this species). We assess the relative risk of overexploitation by combining rmax with estimates of total Z, fishing F, and natural M mortality, and an estimate of the exploitation ratio E. The data indicate that Baraka's whipray is a medium-sized, fast-growing, early maturing species, with a relatively long lifespan. This results in a high rmax relative to many other elasmobranchs, which when combined with estimates of F suggests that the species is not at imminent risk of extinction. Yet, estimates of exploitation ratio E indicate likely overfishing for the species, with full recruitment to the fishery being post-maturation and exploitation occurring across a broad range of age and size classes. Thus, Baraka's whipray is unlikely to be biologically sustainable in the face of current fisheries pressures. This paper makes an important contribution to filling the gap in available data and is a step towards developing evidence-based fisheries management for this species. Further, it demonstrates a simple and widely applicable framework for assessment of data-poor elasmobranch exploitation status and extinction risk.

The comparative energetics of petrels and penguins

Petrels and penguins form the clade Austrodyptornithes. The Add-my-Pet collection of referenced data and Dynamic Energy Budget (DEB) parameters presently has 64 members of this clade. Adaptations to their wandering life style could now be studied; I here try to characterise this clade from an energy perspective. It turned out that petrels are in several respects extreme among birds, showing adaptations to life at low mean food levels. Penguins show the same tendency, but less extreme. Almost all petrel species show a weight-reduction well prior to fledging till the adult weight. This permanent weight reduction suggests that the mean adult feeding level is about 80% of the maximum one. This pattern is well-captured by the standard DEB model, in which (energy) reserve plays an important role. They also have relatively large eggs, and long incubation times and low reproduction rates. I argue that large eggs minimize the age at fledging, given that a particular maturity threshold needs to be reached for fledging. Austrodyptornithes have a high age at puberty, which, in combination with low reproduction rates, causes very low maximum population growth rates. The energy allocation to reproduction for petrels is typical among birds, so the low reproduction rates are the results of the large eggs. Another adaptation to low mean food levels is the large stomach/gut capacity, which appeared to be coupled to a high reserve capacity. This points to be an adaptation to a patchy occurrence of their food, probably in combination with spells of poor weather conditions for feeding. Petrels have a high supply stress and altriciality coefficient, compared to birds, while penguins are a very small altriciality coefficient. This reflects a very high maturity level at puberty for both taxa, in combination with high maturity level at birth for petrels and a typical one for penguins. They have a relatively long life span, compared to other birds, but not extreme. The relative egg size of penguins is typical for birds, to smaller than typical. Penguins combine small eggs with long foraging trips, while small young need frequent feeding. They evolved two adaptation for this: crop milk feeding and collecting lipid-rich food for their offspring. The energetic differences that have been found between petrels and penguins may directly relate to feeding in surface waters by petrels and in deeper waters by penguins; seasonal fluctuations in food density are more pronounced in surface waters. The higher clades Aequornithes and Aequorlitornithes are in many respect intermediate between Austrodyptornithes and other birds, demonstrating a clear taxonomic coherence in energy parameters.

Monitoring, modeling and harvest management of non-native invasive green iguanas on Grand Cayman, Cayman Islands

The green iguana (Iguana iguana) was most likely introduced as a pet and became overabundant during the last 20 years on Grand Cayman. Because negative impacts were unmanageable (e.g., damage to buildings and other infrastructure), a harvest management strategy was developed and implemented, and over 874,252 green iguanas were removed between October 2018 and August 2019. Distance sampling surveys were conducted to estimate abundance in February 2019 and annually in August 2014–2019. Abundance estimates were used to develop a Bayesian state-space logistic model, generate the posterior distributions of population and harvest management parameters, and make future predictions of abundance for August 2020–2030. Abundance increased over fivefold between August 2014 and 2018, from an average of 254,162 to 1,319,939 green iguanas. However, after harvesting for 5 months, abundance declined to an average of 600,113 green iguanas in February 2019; and after 11 months, abundance declined to an average of 103,020 green iguanas in August 2019. Maximum population growth rate averaged 1.552, carrying capacity averaged 1,611,013, equilibrium abundance averaged 805,506, maximum sustainable total harvest averaged 628,491, and maximum sustainable harvest rate averaged 0.776. With harvest rates between 0.600 and 0.800, predicted abundance averaged 28,751 green iguanas for August 2020–2030. However, harvest mortality may have unforeseen outcomes due to the release from density dependence and overcompensation through high survival and fecundity rates. Because natural resource managers have partial control over harvesting and incomplete understanding of green iguana population dynamics, monitoring and modeling are essential to assess population response and guide harvest management decisions.

Enhancing rotifer Brachionus calyciflorus population growth with commercial probiotics

The effect of a commercial probiotic (NanoCrusta, Altacrusta, Mexico City, Mexico) on the growth performance of Brachionus calyciflorus Pallas, 1766, was evaluated. In a first approach, probiotics were supplied in four densities (2.0 × 10³, 1.1 × 10⁵, 2.1 × 10⁵ and 2.1 × 10⁶ cells/ml), alone and in combination with Chlorella vulgaris (1 × 10⁶ cells/ml). The test rotifer did not grow on the probiotic alone. However, when probiotics + C. vulgaris were added, the maximum densities (Dₘₐₓ; ind/ml) and population growth rates (r) observed were higher. In the second experiment, probiotics were supplied at five higher densities (2.1 × 10⁶, 4.2 × 10⁶, 8.5 × 10⁶, 1.7 × 10⁷ and 3.4 × 10⁷ cells/ml) with C. vulgaris and a control treatment with only C. vulgaris (probiotic‐free). Treatments supplied with probiotics between 2.1 × 10⁶ and 1.7 × 10⁷ cells/ml showed significantly higher Dₘₐₓ and r than the control treatment. The results showed a positive effect of probiotic bacteria when supplied with C. vulgaris. The best outcome showed a Dₘₐₓ 2.16 times and an r 1.63 times higher than the density of the control treatment. Growth rates were higher in the treatments with probiotics compared to the control. We conclude that application of NanoCrusta is feasible to improve B. calyciflorus production, but the effects need to be tested in larger scales.

Functional traits explain the Hutchinsonian niches of plant species

AbstractAimThe Hutchinsonian niche is a foundational concept in ecology and evolutionary biology that describes fundamental characteristics of any species: the global maximum population growth rate (rmax); the niche optimum (the environment for which rmax is reached); and the niche width (the environmental range for which intrinsic population growth rates are positive). We examine whether these characteristics are related to inter‐ and intraspecific variation in functional traits.LocationCape Floristic Region, South Africa.Time periodPresent day.Major taxa studiedTwenty‐six plant species (Proteaceae).MethodsWe measured leaf, plant‐architectural and seed traits across species geographical ranges. We then examined how species‐mean traits are related to demographically derived niche characteristics of rmax, in addition to niche optima and widths in five environmental dimensions, and how intraspecific trait variation is related to niche widths.ResultsInterspecific trait variation generally exceeded range‐wide intraspecific trait variation. Species‐mean trait values were associated with variation in rmax (R2 = 0.27) but were more strongly related to niche optima (mean R2 = 0.56). These relationships generally matched trait–environment associations described in the literature. Both species‐mean traits and intraspecific trait variability were strongly related to niche widths (R2 = 0.66 and 0.59, respectively). Moreover, niche widths increased with intraspecific trait variability. Overall, the different niche characteristics were associated with few, largely non‐overlapping sets of traits.Main conclusionsOur study relating functional traits to Hutchinsonian niches demonstrates that key demographic properties of species relate to few traits with relatively strong effects. Our results further support the hypothesis that intraspecific trait variation increases species niche widths. Given that niche characteristics were related to distinct sets of traits, different aspects of environmental change might affect axes of trait variation independently. Trait‐based studies of Hutchinsonian niches thus yield important insights into the mechanisms shaping functional biodiversity, which should reinforce the role of traits in functional biogeography.

Enhanced biomass production and fatty acid accumulation in Scenedesmus sp. LX1 treated with 6-benzylaminopurine

Microalgae have great potential for use in the production of valuable products. However, the low productivity of microalgal cultures is a bottleneck that restricts their large-scale application. In this study, the effects of an artificial, synthetic plant growth-promoting substance, 6-benzylaminopurine (6-BA), on the growth characteristics and physiology of Scenedesmus sp. LX1 was investigated. The results showed that 6-BA affected microalgae growth and physiology in a dose-dependent manner; low doses promoted growth while high doses inhibited growth. At the optimum dose (0.1mgL−1), the maximum algal density and the maximum population growth rate were increased by 20% and 52%, respectively, compared with the control. Meanwhile, the yield of fatty acid methyl esters (FAME) also increased, and their compositions were changed, which resulted in an increase in monounsaturated fatty acid content at lower doses. The rates of nitrogen and phosphorus uptake were also enhanced at low doses. The measurement of photosynthetic activity in the microalgae indicated that lower doses of 6-BA enhanced activity by increasing the amounts of chlorophyll, which promoted the growth of microalgae. Metabolic activity analysis showed that lower doses of 6-BA enhanced dehydrogenase activity and ATP accumulation in microalgal cells. Overall, this study shows that 6-BA has a high potential for use in the development efficient microalgal culture systems.

Life-history constraints on maximum population growth for loggerhead turtles in the northwest Atlantic.

Conservation planning for protected species often relies on estimates of life‐history parameters. A commonly used parameter is the instantaneous maximum population growth rate (r max) that can be used to limit removals and design recovery targets. Estimation of r max can be challenging because of limited availability of species‐ and population‐specific data and life‐history information. We applied a method proposed by Neil and Lebreton, originally developed for birds, to loggerhead turtles. The method uses age‐at‐first‐reproduction and adult survival to estimate r max. We used a variety of datasets and matrix population models to confirm an allometric assumption required by the method, and to generate estimates of age‐at‐first‐reproduction and adult survival. A meta‐analysis was applied to parameters from reported growth curves, which were then combined with the size distribution of neophyte nesters to derive estimates of age‐at‐first‐reproduction. Adult survival rates were obtained from an existing matrix population model. Monte Carlo simulation was then used to combine the estimates of the allometric coefficients, age‐at‐first‐reproduction, and adult survival to obtain a probability distribution of approximate r max values. Estimated annual maximum population growth rates averaged 0.024, with a mode of 0.017 and a 95% highest density interval of 0.006–0.047. These estimates were similar to values reported by others using different methods and captured the variability in positive, annual change estimates across nesting beach sites for the northwest Atlantic loggerhead population. The use of life‐history parameters has a long history in wildlife and fisheries management and conservation planning. Our estimates of r max, while having some biases and uncertainty, encompassed values presently used in recovery planning for loggerhead turtles and offer additional information for the management of endangered and threatened species.