Female Size Research Articles

Reproduction and displacements of known-age caimans Caiman yacare in the Pantanal of Brazil

We recaptured 26 female and 24 male Pantanal caimans Caiman yacare of known-age up to 36 years after marking. The relationship between clutch size and age for known-age females was highly variable although one female captured multiple times between 18 and 26 years of age showed little variation in clutch size. Captured known-age females attending nests varied from 73 cm to 89 cm snout-vent length and from 9 to 36 years old. These females continued to grow long after their first capture, so cessation of growth does not appear to be related to reproduction. Most known-age animals were recaptured within 10 km of where they hatched, but usually on a different ranch, so ranches cannot be used as autonomous management units. Our data indicate that the ratio of snout-vent length (SVL) at first reproduction (73 cm) to mean asymptotic SVL reported for this species (85.7 cm SVL) is much higher in female Pantanal caimans (0.85) than has been reported for most other reptiles (0.7).

Density-dependent fitness and mass-rearing of Habrobracon hebetor (Say) (Hymenoptera: Braconidae) incorporating life table variability

The ectoparasitoid Habrobracon hebetor (Say) (Hymenoptera: Braconidae) is an important natural enemy insect deployed for controlling lepidopteran larvae in warehouses and fields. However, there is limited information on mass-rearing methods of H. hebetor. This study investigated the effects of different Ephestia elutella (Hübner) (Lepidoptera: Pyralidae) and parasitic egg densities on the fitness and mass-rearing efficiency of H. hebetor, aiming to determine the optimal conditions for developing an economically viable and sustainable mass-rearing system for this parasitoid. Our results showed that the average number of eggs laid per host dropped below 7.54 eggs when the number of hosts exceeded five. H. hebetor exhibited significantly increased preadult survival rate (67.41%-81.00%), female and male body size (2224.55-2379.83 μm, 2213.39-2324.65 μm), fecundity (443.98-492.43 eggs), net reproductive rate (R0=154.57-216.67 offspring), intrinsic rate of increase (r=0.2776-0.3223 d-1), net paralyzed rate (C0=72.37-93.17 larvae), and net parasitism rate (Z0=43.55-55.04 larvae) at a density of 5-15 eggs per host than at 20 eggs per host. Meanwhile, considering rearing costs and production rate, a density of 5-15 eggs per host proved to be the most economical for mass-rearing H. hebetor, achieving a daily harvest rate of 10,000 newly emerged female adults. Therefore, for an efficient mass-rearing system for H. hebetor, maintaining a density of 5-15 eggs per host is recommended considering variability in life table and discarding aged individuals (after 36 days old). In summary, providing 5-10 5th instar larvae of E. elutella per day per pair of male and female parasitoid wasps is advised for effective mass-rearing of H. hebetor.

Cutting the sap: First molecular phylogeny of twig‐girdler longhorn beetles (Coleoptera: Cerambycidae: Lamiinae: Onciderini) suggests shifts in host plant attack behaviours contributed to morphological evolution

AbstractUnderstanding how novel adaptive traits arise, evolve and impact other aspects of an organism's phenotype is a foundational question in evolutionary biology. We explore this by focusing on Onciderini (Coleoptera: Cerambycidae: Lamiinae), a tribe of longhorn beetles commonly referred to as twig girdlers because the females of some species girdle live trees to deposit their eggs. We reconstructed the first time‐calibrated phylogeny of the Onciderini, based on three genetic markers (cytochrome c oxidase subunit 1 ‘cox1’, Wingless ‘Wg’ and carbamoyl‐phosphate synthase domain of the CAD locus ‘CPS’), and used morphometric data, employing multiple models of trait evolution and phylogenetic regressions, to assess whether girdling behaviour predicts head size or head size sexual dimorphism. Our results indicate that onciderines originated c. 49 million years ago ‘Ma’ (95% highest posterior densities ‘HPD’: 44.1–54.57 Ma) and consist of two major lineages, which we formalize as subtribes Hypsiomina and Onciderina. Additionally, our analyses revealed several taxonomic inconsistencies within the tribe, which we rectify by proposing new synonymies, including Jamesia Jekel as a synonym of Hypselomus Perty, Cipriscola Dillon & Dillon of Hypsioma Audinet‐Serville and Psyllotoxus Thomson and Taricanus Thomson as a synonym of Oncideres Lacordaire, and a new combination for Periergates kenjii Nearns & Swift as Oncideres kenjii (Nearns & Swift) comb. nov. Using this new phylogenetic framework, we identified five independent unidirectional origins of girdling behaviour within the tribe. Overall, our results suggest that girdling influences head size evolution in Onciderini, as it is associated with an increase in both male and female head size of girdler species. Despite this, girdling and non‐girdling lineages do not consistently differ in head size sexual dimorphism. This study refines the classification of Onciderini and marks a significant step in understanding the evolutionary dynamics shaping the diversity of twig‐girdler beetles, a group with notable ecological and economic importance.

Role of myofiber-specific FoxP1 in pancreatic cancer-induced muscle wasting.

Cancer cachexia affects up to 80% of cancer patients and results in reduced quality of life and survival. We previously demonstrated that the transcriptional repressor Forkhead box P1 (FoxP1) is upregulated in skeletal muscle of cachectic mice and people with cancer, and when overexpressed in skeletal muscle is sufficient to induce pathological features characteristic of cachexia. However, the role of myofiber-derived FoxP1 in both normal muscle physiology and cancer-induced muscle wasting remains largely unexplored. To address this gap, we generated a conditional mouse line with myofiber-specific ablation of FoxP1 (FoxP1SkmKO) and found that in cancer-free mice, deletion of FoxP1 in skeletal myofibers resulted in increased myofiber size in both males and females, with a significant increase in muscle mass in males. In response to murine KPC pancreatic tumor burden, we found that myofiber-derived FoxP1 is required for cancer-induced muscle wasting and diaphragm muscle weakness in male mice. In summary, our findings identify myofiber-specific FoxP1 as a negative regulator of skeletal muscle with sex-specific differences in the context of cancer.

Unveiling the population structure and breeding patterns of Petrolisthes boscii (Audouin, 1826) a common intertidal inhabitant of Shivrajpur, Saurashtra Coast, Gujarat

The present study focused on investigating the population structure and breeding biology of a species of Porcellanid crab, Petrolisthes boscii (Audouin, 1826). Evaluating the population ecology of the species is essential considering its crucial role in ecological functions including the nutrition cycle and its potential vulnerability to environmental stressors. The samples were collected over a period of 12 consecutive months (from March 2019 to February 2020) in an area of 500 m2 during low tide, utilizing the catch-per-unit-effort (CPUE) method when the water receded. The collected specimens (859 individuals) were categorized into males (407 individuals), non-ovigerous females (452 individuals), and ovigerous females (303 individuals). The assessment of fecundity was conducted by measuring the egg characteristics, including the total number, size, and weight of the eggs, as well as the carapace width of the ovigerous females. There was an evident difference in size, with males (8.60 ± 2.76) being significantly larger compared to females (8.39 ± 2.46) (p < 0.001). The overall and monthly sex ratios were female-biased (1:1.17). Moreover, the size frequency distribution revealed a bimodal distribution in male as well as female individuals. Ovigerous females occurred in all the months, which shows that the species breeds continuously throughout the year, with peaks in the months of March to May and August to October. There was a significant positive relationship observed among the size of ovigerous females and their total number of eggs (130.39 ± 83.31), egg mass weight (150 ± 110 mg). The study may provide baseline information for future studies on the impacts of a continuously altering environment and the consequences of increasing anthropogenic pressure on coastal areas.

Among-population variation in sexual size dimorphism of Nepa cinerea (Heteroptera: Nepomorpha)

AbstractNepa cinerea is a common aquatic predator. It is widely distributed in various aquatic biotopes of the Palaearctic. Body size is an important trait that impacts the fitness and survival of animals and thus their evolution. Like most insects, N. cinerea males are smaller than females, but sexual size dimorphism (SSD) has not been investigated. We investigated the extent of SSD, the validity of Rensch's rule, and morphological differences between nine populations based on 51 morphological parameters. Females were found significantly and marginally significantly larger than males in all but one population. However, no difference in body length was found between the populations. Population had a significant effect on 12 traits for females and only on 5 for males, showing that females are more variable than males. Specifically, differences were found in the length of the second and third leg pairs. We did not find any support for the Rensch's rule. Nevertheless, female body size and SDI (sexual dimorphism index) were positively correlated. We suggest that fecundity selection accounts for female-biased SSD in N. cinerea.

Sex-dependent shifts in body size and condition along replicated elevational gradients in a montane colonising ectotherm, the common wall lizard (Podarcis muralis).

In ectothermic animals, elevational gradients, such as mountainous environments, are often associated with shifts in body size, although patterns differ across taxa and contexts. Mountain landscapes are characterised by relatively rapid shifts in biotic and abiotic conditions along an elevational gradient, commonly referred to as elevational zonation. Such zonation can reduce the geographic scale at which organisms experience the effects of climate change. The upslope range shifts will expose organisms at the colonization front to sub-optimal conditions. We can expect these challenging conditions to influence many life-history traits including growth rates and reproductive output. We tested the hypothesis that body size varies across elevational gradients in a contemporary montane colonizer, the common wall lizard (Podarcis muralis). Further, we assessed active body temperatures and available environmental temperatures in an attempt to discern a potential abiotic factor that might drive such a pattern. We quantified body size in lizards along four replicate transects ranging from 400 to 2400m above sea level in the Pyrenees. Male body size decreased with increasing elevation. While female body size was invariant, females at higher elevation exhibited lower body condition. These results suggest that the effects of abiotic limitations or selective pressures experienced at the high-elevation colonisation front are sex-specific. Furthermore, lizards from both sexes were able to maintain similar field active body temperatures across elevation, despite reduced ambient temperature. If available temperatures limit activity periods or necessitate higher thermoregulatory investment, as suggested by our results, then further warming may benefit lizards and favour further upslope migration.

Factors influencing management of dry cell battery waste: a case of Greater Accra Region in Ghana

Indiscriminate disposal of dry cell battery (DCB) waste contributes to environmental and public health issues in developing countries such as Ghana, due to the toxic nature of this specific waste. Accordingly, a study was conducted in Accra, Ghana, to determine the socio-economic and demographic factors influencing handling DCB waste, aiming a sustainable environment. Using a random sampling technique, a descriptive cross-sectional survey was conducted, encompassing 367 respondents from the Accra-Tema Metropolitan areas and Tema West Municipal Assembly in Greater Accra, Ghana. Using descriptive and multivariate statistical methods, the survey data were analysed with the Statistical Package for Social Sciences (SPSS) version 27. The results of this study show that female gender and residential area are likely to positively influence the use of DCB at home. Education significantly affects the use of DCB and its proper disposal. The results also suggest that 78% of the respondents disposed of DCB waste in waste bins. The mean monthly income of the respondents stands at USD 270, which is average and likely partially to positively influence the disposal of the DCB. The data collected revealed that female gender, age group, family size, and education level influence the indiscriminate disposal of DCB waste and DCB waste recycling. The results highlight that educated females above the age of 55, with a monthly income, are likely to properly segregate DCB waste. This study contributes to the knowledge gap in relation to dry cell battery waste management (DCBWM) in developing countries, aiming to advance global sustainability. This study is expected to contribute to educate and create awareness in managing DCB waste to reduce its indiscriminate disposal which leads to environmental pollution and negatively affects human health and environmental sustainability in Ghana.

Foraging strategy as a route for sexual size dimorphism evolution.

Female-biased sexual size dimorphism stands as a widespread evolutionary pattern. Fecundity selection, favouring larger females with greater reproductive output, is a leading explanation. However, larger body sizes demand greater energy intake, potentially hindering the evolution of extreme female sizes. Thus, the evolution of more lucrative foraging tactics may allow for an increase in size. Hence, coupled with selection against larger males, fecundity selection should result in larger SSD in species with more lucrative foraging strategies. Crab spiders are sit-and-wait predators that hunt in several plant substrata. Species that forage on flowers or employ prey-luring strategies likely have access to higher food intake than other species. We extracted body size measurements of 614 crab spider species from 43 genera and classified them based on their foraging strategy. Our findings show that foraging strategies that provide higher energy input (EFS) result in larger SSD. Statistical estimates indicate that females have a cephalothorax width 91% larger than males in EFS species, compared to 26% larger females than males in non-EFS species. These differences possibly arise due to larger females and smaller males. The effects on male size reduction might result from scramble competition, whereas the increase in female size is likely due to fecundity selection. These results suggest that the shift towards more lucrative foraging strategies may have been a key event in body size and SSD evolution in crab spiders.

Agronomic characteristics and economic performance of cocoa farms in Haiti

Abstract This study aimed to describe the agronomic characteristics of the cocoa based farms, estimate their agronomic and economic performance and carry out a gender analysis. Data relating to crops economic value or food security importance, household size, farmers’ age, farm size, crop yield and farm family income were collected by focus groups or individual surveys. The results showed that, in average, the households’ size was 4.37 people and the producers’ age, 52 years. The female headed farm size was 1.56 ha against 2.20 ha for the male headed ones. Cocoa farm yield was 562.98 kg/ha and average farm income, 622.3 USD for female headed farms against 1138.0 USD for male headed ones. Compared to male, female farmers possessed less land and earned lower farm income.

A magnetic resonance imaging-based morphometric analysis of bilateral L1-L5 oblique lumbar interbody fusion corridor: feasibility of safe surgical approach and influencing factors.

Retrospective cross-sectional study. To investigate the size and local anatomy of the right and the left-sided oblique corridors between L1-L5 levels and identify the potential impact of increasing age and sex on corridor size. The oblique lumbar interbody fusion (OLIF) was introduced by Silvestre and his colleagues as a solution to the approach-related complications associated with anterior lumbar interbody fusion and lateral lumbar interbody fusion. Limited data were available describing the local anatomy and morphology of this approach. Imaging data of 300 patients (150 males and 150 females) who underwent 1.5T magnetic resonance imaging (MRI) scans of the lumbar spine at Indian Spinal Injuries Centre, New Delhi, India between January 2023 and January 2024 were retrospectively reviewed. The cohort was stratified into six age groups (21-30, 31-40, 41-50, 51-60, 61-70, and >70 years) with 25 patients in each age group for both sexes. T2 weighted axial MRI images were analyzed from the L1-L5 level at the mid-disc level to calculate the corridor size. The local anatomical differences were recorded. At L1-L2, L2-L3, L3-L4, and L4-L5 levels, the mean corridor sizes in males were 17.48, 15.50, 13.41, and 9.32 mm on the left side, and 11.48, 7.12, 4.34, and 1.64 mm on the right side, respectively. The corresponding mean corridor sizes in females were 10.34, 12.94, 12.64, and 7.22 mm on the left side and 2.66, 3.52, 3.69, and 1.64 mm on the right side, respectively. For both sides, the corridor size was significantly affected by sex, increased with age, and decreased at the lower lumbar disc levels. A left-sided OLIF approach is more feasible for both sexes. The right-sided approach is less likely to be performed effectively.

Spatial distribution and fecundity of the cinnamon shrimp, Macrobrachium acanthurus (Wiegmann, 1836) (Crustacea: Decapoda: Palaemonidae) from Jequitinhonha River (BA), Brazil

ABSTRACT Macrobrachium acanthurus is an amphidromous palaemonid shrimp exploited by artisanal fishing in Brazil that presents limited published information on its population biology. Therefore, this study aimed to assess the spatial distribution and fecundity of M. acanthurus in the Jequitinhonha River (BA). Collections occurred at four points in the river downstream of the Itapebi Hydroelectric Powerplant (P1–P4). The abundance and size of the demographic categories analysed (male morphotypes, non-ovigerous females, and ovigerous females) and fecundity were compared among points. We also examined the relationship between female body size and fecundity. A total of 938 individuals were collected during the sampling period. The highest abundances were observed downstream (P3 and P4). The sizes of males and ovigerous females were greater at points farthest upstream. Three male morphotypes were identified, and their proportions varied among points. Fecundity was higher upstream, and there was a positive correlation between female size and number of eggs. All population parameters indicate a longitudinal gradient towards the estuary, with strong evidence of amphidromy. This is the first study with a polymorphic species to consider morphotypes as a population structure component. The results represent an important contribution to a better understanding of the amphidromous life cycle of palaemonid shrimp.

Is sexual size dimorphism in walleye, Sander vitreus, a driver of seasonal movements in Lake Erie?

Walleye (Sander vitreus) are a sexually dimorphic species in which females are larger than males in adulthood. Walleye can also exhibit sex- and population-based differences in migration behavior. In Lake Erie, we used acoustic telemetry to test the prediction that female walleye exhibit larger broad-scale movements than males during the summer and autumn. This prediction was based on the hypothesis that greater foraging in females would be needed to satisfy their higher energy requirements. We quantified movements of males and females from distinct spawning populations from Lake Erie's west and east basins using a lake-wide grid of acoustic receivers in 2017 and 2018. We found no differences between male and female home range sizes, core range sizes, or distances travelled in either population. Fish length-at-tagging was unrelated to the size of a fish's home range or to its distance travelled, contrary to previous predictions about body size as a driver of migration distance in the Lake Erie population. We found that west basin walleye occupied large and indiscrete portions of the lake, but the core range of females extended into the central basin, whereas males were concentrated in the west basin. Walleye originating from the east basin confined their movements primarily to the east basin and showed stronger home range overlap among members of their population than did walleye from the west basin population. Within either population, walleye had more home range overlap with members of the same sex, which likely reflects differences in the migratory tendencies of males and females.

Features are more than just filling in the blanks on body size scales

ABSTRACT Despite widespread misperceptions of body size and shape, the specific visual features influencing such judgments remain unclear. This study assessed the contribution of internal body features (e.g., colour, shading) to the accuracy of female body size judgements and whether that contribution varies with body size. Using a bodyline task, 100 female participants evaluated images of female bodies, either depicted as real bodies including internal features (feature stimuli) or images of bodies as silhouettes only (silhouette stimuli). The results showed greater overall errors in body size estimation for silhouettes compared to full feature images. However, the direction of error differed for large and small bodies: small silhouettes were judged larger than their full-feature counterparts, while large silhouettes were judged smaller. These findings emphasize the importance of internal body features in shaping perceptions of female body size and highlight the complexity of judgement accuracy across different body sizes.

Post-Copulatory Sexual Selection in an Insect With High Levels of Mating Failure.

Sexual selection is not a single process. Instead, multiple processes of sexual selection can interact with respect to a given phenotype, in either reinforcing, independent, or conflicting directions. Here we consider how different processes of sexual selection interact in the seed bug Lygaeus simulans. This species is characterised by limited pre-copulatory sexual selection, but the potential for rather strong post-copulatory sexual selection. In particular, mating failure is common in this species, with around 40%-60% of copulations failing to result in the successful transfer of sperm. Mating failure is negatively correlated with female size, with smaller females being less likely to end up inseminated. We have recently argued that this pattern is best explained by cryptic male mate choice for large, more fecund females. Males therefore preferentially inseminate larger females. Here we explore how this potential cryptic male choice interacts with another component of post-copulatory sexual selection: sperm competition. We first manipulated male and female size variation, generating large and small, male and female, size classes. Using a visible mutant marker to assign paternity, we then double-mated females with males, in all combinations of male and female size. Our results showed that sperm competition outcomes were primarily driven by copulation duration, with longer copulations leading to greater paternity share for a male. We also confirmed that larger females are more likely to produce offspring than smaller females, as predicted by cryptic male choice for large females. This effect was again linked to copulation duration, with longer copulations less likely to lead to mating failure. While larger males tended to be more successful in sperm competition, especially if copulating second, female size had little effect on paternity, suggesting that cryptic male choice and sperm competition are acting relatively independently in this species.

Shifting spawning phenology in Hudson River American Shad

AbstractObjectiveThe objectives of this study were to investigate potential shift in the phenology of spawning for the Hudson River American Shad Alosa sapidissima and to identify factors contributing to the decline of the Hudson River shad population.MethodsThis study utilized American Shad eggs collected from the Long River Ichthyoplankton Survey. Logistic models were employed to estimate spawning phenology metrics, including the onset, peak, cessation, and duration of the spawning season. Additionally, we investigated the effects of biotic and abiotic variables on spawning timing.ResultThis study suggests that temporal changes in the spawning onset exhibited high variation and were not significant. However, a significantly delayed spawning peak and cessation, along with an extended spawning season, were observed. Additionally, the findings of this study revealed a correlation between the timing of spawning onset and water temperature, indicating that a 1°C increase in water temperature was associated with a 3.66‐day earlier initiation of spawning. Smaller female spawner size was associated with delayed peak and cessation of the spawning season. With a 1‐cm decrease in the average female spawner size, the peak of the spawning season was delayed by 1.79 days and the cessation of the spawning season was delayed by 2.87 days.ConclusionThe findings indicate that water temperature may be a crucial trigger for initiating spawning in Hudson River American Shad, with higher water temperatures associated with earlier spawning onset. Moreover, the findings indicate that the timing of spawning peaks and cessations has been progressively delayed over time, and this is linked to the size of female spawners.

Male Reproductive Traits Display Increased Phenotypic Variation in Response to Resource Quality and Parental Provisioning in a Tropical Rainforest Dung Beetle, Onthophagus c.f. babirussa.

Reproductive traits that mediate differential fitness associated with mate acquisition and fertilisation success are often strongly linked to the overall condition. We investigated the effects of resource quality and parental provisioning in the phenotypic expression of sexual and non-sexual traits in a rainforest dung beetle, Onthophagus c.f. babirussa (Eschscholtz, 1822) from Singapore. F1 individuals were reared from wild-caught beetles and paired up to produce offspring (F2), and F2 larvae from the same F1 parents were reared on two dung substrates (herbivore and omnivore) in a full-sib design. Sexual traits displayed greater phenotypic variation in response to dung resource quality, with the precopulatory trait (horn length) responding more than the postcopulatory trait (testes weight). Notably, genotype-by-environment interactions between parental lines (genotype) and dung type (environment) affected male body size and horn length only, suggesting sex-specific variance in plasticity associated with sexually selected precopulatory traits. Dung type had significant effects on all measured traits. Offspring that were provisioned higher quality resource (omnivore dung) had larger absolute and relative trait values. Parental lines only significantly affected female body size but none of the male traits, suggesting an important role of environment and resource partitioning in determining precopulatory success of male offspring. Parental provisioning of larval resource varied with resource quality and brood sequence. Parents provisioned more dung when herbivore dung was presented than when they were given omnivore dung and provisioned more dung for their earlier broods when using herbivore dung but not omnivore dung. This suggests a trade-off between early offspring fitness and resource quality. We tested directly for genotype-by-environment (G × E) interactions in the expression of several morphological traits relevant to dung beetle fitness and documented that offspring with similar phenotypes may result from completely different parental resource allocation strategies. We discuss the importance of studying parental investment on trait variation and its implications on dung beetle ecology.

Characterization of the reproductive strategy of invasive Round Goby (Neogobius melanostomus) in the Upper DanubeRiver.

Originating from the Black and Caspian seas, the Round Goby (Neogobius melanostomus) has become one of the most successful invaders of freshwater ecosystems. In this study, we provide a characterization of the reproductive strategy of an established population of Round Gobies in the Upper Danube river including sex ratio, fluctuations of gonadosomatic index (GSI), analysis of timing of spawning as well as of clutch and egg size. We compare these results to other studies from the native and invaded range. In the Danube, the Round Goby population was found to be female dominated, however fluctuations in magnitude of female bias were observed between months. Monitoring of the population across 1.5 years revealed that GSI was highest from April to June, while lowest values were observed in August and September. Using time-series analysis, a delayed effect of temperature on GSI was found for females and males, while a quicker response of GSI levels to photoperiod and discharge was observed for females. GSI increased with body size for females and eggs were found to be significantly larger in May, however clutch sizes did not differ between months. Results of a literature review revealed great differences in timing and length of spawning season as well as sex ratio between populations throughout the distribution range, which can probably be explained by climatic and photoperiodic conditions together with the time since invasion and the high plasticity of Round Gobies.

Disruption of natural disturbance regime decouples habitat and life stage in a keystone species

AbstractAnthropogenic disturbance of stream ecosystems, often chronic in nature, has been studied extensively. However, when disturbance is driven by more than one resource policy over many decades, feedback between habitat evolution and biological adaptation can be disrupted and ecological function affected in unforeseen ways. We analyzed over 100 years of Chinook salmon (Oncorhynchus tshawytscha) length frequency trends associated with fisheries management and changes in available spawning substrate (habitat) linked to flow regulation in a highly altered California river. Over time, salmon lengths generally decreased, fluctuating with exploitation (ocean harvest) and hatchery production rates. Female size reduction, coupled with a degrading and coarsening channel, and perching peripheral habitat related to past mining activity, indicates available spawning substrate may be too large to support the current salmon population. Assuming a salmon can move material ~10% of her body length, length frequency data and current substrate size distribution suggest that increasing salmon sizes to historic distributions could increase available spawning habitat by as much as 13%. Alternatively, decreasing spawning substrate size could support a greater portion of the current population. To test the latter hypothesis and inform future management actions, we monitored two spawning riffles where large and small gravel was placed on top of a cobble. We observed an immediate spawning activity increase that was more pronounced where smaller gravel was deposited. Following a decade of habitat decline, the two sites were both replenished with medium gravel. Elevated spawning use occurred immediately at both sites, commensurate with this intermediate size, further supporting our hypotheses. Sediment coarsening and habitat disconnect below dams, combined with reduced salmon size, indicate the natural spawning process may be decoupled from available habitat below dams in the foreseeable future without continuous intervention. Actively managing salmon population demographics through modified hatchery and size‐selective harvest practices and developing a coarse sediment budget with size‐appropriate material for regulated anadromous rivers could produce immediate benefits for ecosystem services, including salmon populations. However, these management actions will require continued maintenance and informed socio‐ecological goals to remain successful.

Interactions between invasive pests and pathogens in a native chestnut forest

The introduction in the same area of different invasive species can result in novel interactions, with unpredictable consequences. We carried out a study in Galicia (northwestern Iberian Peninsula) with the aim of clarifying the interactions between two invasive species Cryphonectria parasitica and Dryocosmus kuriphilus. In 2018, we selected five chestnut plots affected by both species. We compared trees affected only by the insect and trees affected by both the insect and the fungus with respect to attack level, gall characteristics, female size and fecundity, and concentrations of nitrogen, water and secondary metabolites. We also evaluated female preferences in a greenhouse assay. There were higher levels of attack in trees affected by both invaders. However, the greenhouse assay showed that ovipositing females do not preferentially choose trees attacked by the fungus. The presence of the fungus had no effect on the size, wall thickness, or hardness of D. kuriphilus galls, but larvae were smaller in trees also affected by the fungus. The fecundity of females was strongly related to the presence of chestnut blight; the number of eggs per female was almost double in trees affected by the fungus. There were no relations between blight and the nitrogen or water content in the galls, where the insects feed. There were also no effects of chestnut blight on the concentration of terpenes or phenols, but condensed tannins were higher in trees with chestnut blight. The higher tannins induced by chestnut blight may directly or indirectly benefit gall wasps. Positive relationships between condensed tannin concentration and reproductive performance of other gall makers were previously reported. Tannins can also improve the negative effects of environmental conditions inside the gall. Our results indicate that the presence of chestnut blight can increase the suitability of chestnut trees for the invasive insect, D. kuriphilus, through the increase in tannins due to the presence of the fungus.