Population Persistence Research Articles

Intensive cropping influences the success of seed dormancy breaking methods in Australian collected Hordeum, Avena, and Bromus sp.

Seed dormancy is a critical evolutionary trait that enhances the persistence of plant populations under both natural and managed conditions. It is influenced by genetic and environmental factors, with crop management practices like tillage and herbicide use reportedly selecting for increased seed dormancy in weeds. This study aimed to compare the success of seed dormancy breaking methods between weed populations collected from intensively managed crop fields and unmanaged ruderal locations. Weeds from intensively managed fields, including Hordeum glaucum, H. leporinum, Avena fatua, Bromus diandrus, and B. rigidus exhibited significantly higher seed dormancy and didn't respond largely to seed dormancy breaking methods compared to those from unmanaged areas. Dormancy-breaking treatments such as sandpaper scarification were effective in barley grass, while endosperm excision followed by cold stratification alleviated dormancy in brome grass and wild oat. Dark incubation consistently improved germination across all species, enhancing the efficacy of treatments like cold stratification, sandpaper scarification, and gibberellic acid (GA3). Weeds in managed fields develop greater seed dormancy, likely as an adaptive response to agricultural practices. Techniques such as tillage, which incorporate seeds deeper into the soil, may help mitigate seed dormancy traits by reducing light exposure. These findings highlight the importance of dormancy management in controlling persistent weed populations. © 2024 Society of Chemical Industry.

PFKFB3-dependent redox homeostasis and DNA repair support cell survival under EGFR-TKIs in non-small cell lung carcinoma

BackgroundThe efficacy of tyrosine kinase inhibitors (TKIs) targeting the EGFR is limited due to the persistence of drug-tolerant cell populations, leading to therapy resistance. Non-genetic mechanisms, such as metabolic rewiring, play a significant role in driving lung cancer cells into the drug-tolerant state, allowing them to persist under continuous drug treatment.MethodsOur study employed a comprehensive approach to examine the impact of the glycolytic regulator 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase (PFKFB3) on the adaptivity of lung cancer cells to EGFR TKI therapies. We conducted metabolomics to trace glucose rerouting in response to PFKFB3 inhibition during TKI treatment. Live cell imaging and DCFDA oxidation were used to quantify levels of oxidation stress. Immunocytochemistry and Neutral Comet assay were employed to evaluate DNA integrity in response to therapy-driven oxidative stress.ResultsOur metabolic profiling revealed that PFKFB3 inhibition significantly alters the metabolic profile of TKI-treated cells. It limited glucose utilization in the polyol pathway, glycolysis, and TCA cycle, leading to a depletion of ATP levels. Furthermore, pharmacological inhibition of PFKFB3 overcome TKI-driven redox capacity by diminishing the expression of glutathione peroxidase 4 (GPX4), thereby exacerbating oxidative stress. Our study also unveiled a novel role of PFKFB3 in DNA oxidation and damage by controlling the expression of DNA-glycosylases involved in base excision repair. Consequently, PFKFB3 inhibition improved the cytotoxicity of EGFR-TKIs by facilitating ROS-dependent cell death.ConclusionsOur results suggest that PFKFB3 inhibition reduces glucose utilization and DNA damage repair, limiting the adaptivity of the cells to therapy-driven oxidative stress and DNA integrity insults. Inhibiting PFKFB3 can be an effective strategy to eradicate cancer cells surviving under EGFR TKI therapy before they enter the drug-resistant state. These findings may have potential implications in the development of new therapies for drug-resistant cancer treatment.

Moving to Venice and settling there: a synthesis on the biology of Sandwich Tern (<i>Thalasseus sandvicensis</i>) in the largest Mediterranean wetland during the 1995-2023 years

In 1995, the first colony of Thalasseus sandvicensis settled in a saltmarsh islet in the Lagoon of Venice, NE Italy. The number of nesting pairs rose from 202 (1995) pairs to 3503 (2023), with the arrival of immigrants peaking in 2014 (+887 pairs) and 2023 (+1884). From 1995 to 2023, the number of breeding pairs showed a moderate increase (p<0.01), with a yearly rate of +5.7%. Two kinds of colony sites were used: i) salt marsh islets, where birds nested mostly on windrows. These sites were usually in well-secluded area, with low levels of human disturbance; ii) man-made sites such as dredge islands, with nests placed on the bare ground. These man-made sites, in one case located at about 200 m from the town of Venice, were used only since 2014 and now support a large fraction of the breeding population. Overall, 73 colonies were found (361±423 pairs, range: 5-2762; median: 203). Each year there were one to six colonies; 21 colony sites were used at least once. On average, a site was used for 3.5±5.4 years (range 1-25), but the first site was used 25 years out of 29. The turnover rate was overall 41.4%. Over the study period, the biggest cause of clutch loss was flooding during extreme high tides, which are becoming more and more frequent and responsible for more than 90% of losses until 2022. In 2023, an H5N1 avian influenza outbreak annihilated the productivity of the whole nesting season. Clutch size was 1.7±0.5 (n=1338) without differences between saltmarsh and dredge islands: 1.64±0.5 vs 1.81±0.45 eggs per clutch. At the colonies, the association between T. sandvicensis and Larus ridibundus was strong and moderate with Sterna hirundo; instead, a negative and moderate correlation was found between T. sandvicensis and Sternula albifrons. The persistence of the largest Italian population appears threatened by several factors, among which the multiple effects of climate change are the most dangerous.

Wolbachia strain wMelM disrupts egg retention by Aedes aegypti females prevented from ovipositing.

Aedes aegypti mosquitoes are well adapted to dry climates and can retain their eggs for extended periods in the absence of suitable habitat. Wolbachia strains transferred from other insects to mosquitoes can be released to combat dengue transmission by blocking virus replication and spreading through populations, but host fitness costs imposed by Wolbachia, particularly under some environments, can impede spread. We, therefore, assessed the impact of two Wolbachia strains being released for dengue control (wAlbB and wMelM) on fecundity and egg viability following extended egg retention (up to 24 days) under laboratory conditions. Egg viability following retention decreased to a greater extent in females carrying wMelM compared to uninfected or wAlbB females. Fertility fully recovered in uninfected females following a second blood meal after laying retained eggs, while wMelM females experienced only partial recovery. Effects of wMelM on egg retention were similar regardless of whether females were crossed to uninfected or wMelM males, suggesting that fitness costs were triggered by Wolbachia presence in females. The fecundity and hatch proportions of eggs of wMelM females declined with age, regardless of whether females used stored sperm or were recently inseminated. Costs of some Wolbachia strains during egg retention may affect the invasion and persistence of Wolbachia in release sites where larval habitats are scarce and/or intermittent.IMPORTANCEWolbachia mosquito releases are expanding around the world with substantial impacts on dengue transmission. Releases have succeeded in many locations, but the establishment of Wolbachia has been challenging in some environments, and the factors contributing to this outcome remain unresolved. Here, we explore the effects of Wolbachia on a novel trait, egg retention, which is likely to be important for the persistence of mosquito populations in locations with intermittent rainfall. We find substantial impacts of the Wolbachia strain wMelM on the quality of retained eggs but not the wAlbB strain. This cost is driven by the Wolbachia infection status of the female and can partially recover following a second blood meal. The results of our study may help to explain the difficulty in establishing Wolbachia strains at some field release sites and emphasize the need to characterize Wolbachia phenotypes across a variety of traits and strains.

Presence of the smalltooth sawfish in the Cuban Archipelago

The smalltooth sawfish Pristis pectinata is listed as Critically Endangered by the International Union for Conservation of Nature. A greater focus on the status of sawfish globally, including Cuba, is yielding much needed information on the status of this species. Interviews were conducted in 2011, 2019, and 2022 (n = 473) with coastal community members from 80 sites throughout Cuba to assess whether sawfish are still extant in Cuban waters. Traditional ecological knowledge results show sawfish encounters (n = 33) at 26 sites in Cuba since the 1960s. Northern Camagüey province was identified as the region with the highest number of sightings, with the most recent in Cárdenas Bay in 2019. The highest number of sightings occurred in relatively deep water and along the coral reef drop off. Reports, specimens, and rostra represented a wide range of sizes, from very young to mature individuals collected throughout Cuba’s northern and southern shores, suggesting the persistence of a resident population, though occasional movements between Cuba and neighboring countries are possible. We recommend the following actions to better understand and protect sawfish in Cuba: (1) amending the National Plan of Action for the Conservation and Management of Chondrichthyes in the Republic of Cuba to include specific measures that address sawfishes; (2) designing and implementing sawfish awareness, outreach, and encounter recording programs that focus on raising awareness and reducing threats to sawfish, including best handling practices; and (3) conducting genetic studies to assess whether Cuba’s population is resident or shared with the Bahamas and/or Florida.

A spatiotemporal model for the effects of toxicants on the competitive dynamics of aquatic species

In this paper, we develop a reaction–diffusion model with negative toxicant–taxis that incorporates spatiotemporally inhomogeneous toxicant input to investigate the impact of toxicants on the competitive dynamics of two species in a polluted aquatic environment. Here the negative toxicant–taxis models the evasive movement of avoiding toxicants by species. We establish the global well-posedness of the model, analyze the existence and stability of spatially homogeneous steady states, and derive sufficient conditions for species extinction and coexistence. Through linear stability analysis, we identify sufficient conditions on model parameters that destabilize spatially homogeneous steady states under spatiotemporally uniform toxicant input. Numerical experiments reveal the influence of key toxicant-related factors (input rate, taxis intensity, and diffusivity) on competition outcomes and species distributions. Notably, strong negative toxicant–taxis can induce spatial aggregation and segregation patterns between the species and the toxicant under uniform toxicant input. Our findings suggest that toxicant–taxis may promote population persistence and coexistence, particularly when the toxicant input is not uniform in space and time and the toxicant does not diffuse fast (i.e. weak diffusivity). However, strong toxicant diffusion can diminish the impact of taxis, adversely affecting population persistence and species coexistence.

Environmental change mediates plasticity in offspring traits through maternal effects in a coral reef fish

Wild populations are continuously challenged by natural environmental variation as well as threatened by anthropogenically-induced habitat loss and fragmentation. Non-genetic parental effects may be a key mechanism across taxa to cope with such environmental challenges and threats. However, the way in which environmental change modulates parental and offspring traits remains poorly studied in marine fish, especially in the wild. We empirically test whether environmental change directly affects monthly reproductive output and offspring phenotypes, including egg size, larval size and larval swimming abilities, in a wild population of anemonefish. In addition, we test whether environmentally induced parental physiology (hormones) modify parental traits, as well as offspring traits intergenerationally. First, we demonstrate plasticity in parental reproductive output when habitat size (anemone surface area) was experimentally manipulated. Second, we show intergenerational plasticity in wild anemonefish offspring traits. When habitat size increased, offspring traits were unchanged, but reproductive output was increased. Maternal reproductive hormones, such as 17ß-estradiol, showed a trend to increase when habitat size increased and 17ß-estradiol correlates positively with reproductive output. When habitat size decreased, reproductive output decreased, and smaller eggs and larvae were produced, however, these larvae swam faster. Our results provide evidence for marine fish plasticity in both reproductive output and offspring traits. In addition, the maternal reproductive hormone 17ß-estradiol plays a role in determining reproductive output and larval phenotypic traits. Through our study conducted in the wild, we show how changes in habitat size affect fitness of both parents and offspring in different ways. We highlight how parental and offspring plasticity, via intergenerational maternal effects, may ensure population persistence under environmental change.

Seasonally variable thermal performance curves prevent adverse effects of heatwaves.

1. Differential vulnerability to heatwaves may affect community dynamics in a changing climate. In temperate regions, this vulnerability to heatwaves depends on the interactions between seasonal temperature fluctuations and the capacity to rapidly shift thermal performance curves. 2. Here we investigate how these dynamics affect the vulnerability of two ecologically important copepod congeners, Acartia tonsa and A. hudsonica, to heatwaves of different durations. Using a combination of field observations and simulated laboratory heatwave experiments, we uncover strong seasonal variation in the performance curves of A. tonsa but not A. hudsonica. This translated to species-specific seasonal patterns of vulnerability to heatwaves, with increased vulnerability in A. hudsonica. 3. By reducing parental stress during simulated heatwaves, seasonal performance curve shifts likely reduced indirect, transgenerational effects of these events on offspring performance in A. tonsa. 4. Our results illustrate how different levels of seasonal variation in thermal performance curves will affect population persistence in a changing climate.

How Do Species Traits and Biogeographical Factors Determine the Fate of Amphibians After Long‐Term Fragmentation?

ABSTRACTAimIdentifying key factors that render certain species more vulnerable to fragmentation is vital for elucidating processes underlying extinction and targeting conservation priorities. However, few studies have explored the delayed ecological responses of species following isolation. To bridge the gap, we conducted comprehensive analyses of correlates of extinction vulnerability and biogeographical variation in amphibians over long‐term fragmentation.LocationZhoushan Archipelago, China.MethodsWe sampled the occupancy of amphibians on 37 land‐bridge islands. We calculated three metrics of extinction vulnerability (population extinction rate, island occupancy frequency and species nestedness ranking) for each species and correlated these variables with eight species' traits. We further explored biogeographical variations in amphibians by relating five biogeographical variables to species' probability of occurrence and calculated the threshold for the persistence of each species on islands.ResultsSpecies with low natural abundance, larger egg sizes, smaller clutch sizes or restricted geographical distributions were more likely to experience higher population extinction rates and species nestedness rankings, while lower island occupancy frequencies across islands. Although most species were found on larger islands, we observed significant increases in the occurrence probabilities with island area for five species. The estimated areas with a 50% chance of occurrence ranged from 0.39 to 199.5 km2. Interestingly, the likelihood of occurrence of Hyla chinensis (treefrog) was negatively related to distance to the mainland after controlling for the effect of area.Main ConclusionsOur study highlights the variation in the fragmentation sensitivity of amphibians. Species distribution was primarily regulated by area‐related extinction, particularly for those with ‘slow’ life history strategies or restricted ranges. Overall, management efforts should focus on species with extinction‐prone traits and landscape features that threaten the persistence of populations. Future studies should consider the sequential separation of island populations and the interaction of traits to reveal the fate of species to fragmentation.

Impacts of river flow and thermal regimes on fish growth dynamics during early life history

Growth during early life stages is critical to fish population persistence. Few studies explore how river discharge and thermal regimes impact growth dynamics of young-of-the-year (YOY) fishes. We used otolith biochronologies and generalised additive mixed models to partition the effects of age, individual, river, temperature, discharge, and variance in discharge on daily growth rates of YOY fishes with an opportunistic life-history strategy: Galaxias vulgaris and Gobiomorphus breviceps. Growth of both species increased with temperature. Galaxias growth decreased with discharge, while Gobiomorphus growth increased with lowered discharge but only to a point (ca. 1/3 of median discharge), after which growth plateaued. Floods had a strong negative effect on YOY growth. Our study systems and species had different characteristics to those that formed the basis of the Riverscape Recruitment Synthesis Model (RRSM) and may explain why our results were only partially consistent with flow predictions for opportunistic species of the RRSM. Further, Galaxias growth was a negative function of high-frequency, daily variation in flow, and we present testable hypotheses to explain this result.

Inbreeding avoidance and cost in a small, isolated trout population.

The persistence of small populations is influenced by the degree and cost of inbreeding, with the degree of inbreeding depending on whether close-kin mating is passively or actively avoided. Few studies have simultaneously studied these factors. We examined inbreeding in a small, isolated population of westslope cutthroat trout using extensive genetic and demographic data. Passive inbreeding avoidance was low, with predicted lifetime dispersal of approximately 36 and 74 m for females and males, respectively. Additionally, we found limited evidence for active inbreeding avoidance during reproduction. Relatives remained spatially clustered into adulthood, and observed relatedness among mate pairs was greater than expected under random mating by 0.09, suggesting that inbreeding is a concern in this population. Further, we examined sex-specific inbreeding depression throughout the life cycle and provide evidence for inbreeding depression in some fitness components, including family size, juvenile survival and reproductive success. Our results suggest that, in an at-risk trout population, limited passive and active inbreeding avoidance lead to a higher degree of inbreeding than expected under random mating. Observed inbreeding, along with evidence for fitness reduction due to inbreeding depression, could put the population at a heightened risk of decline or extirpation.

Climate Change Could Reduce the Geographic Distribution of the Natterjack Toad in Semi-Arid Regions: A 34-Year Study in Central Spain

Amphibians are globally threatened due to pollution, infection diseases, invasive species, habitat loss and climate change. Rising temperatures and shifts in precipitation regimes can have a major impact on the persistence of amphibian populations, especially in semi-arid regions. In this study, we used a long term time series spanning 34 years in central Spain to evaluate the effect of three climatic variables on the reproductive success of the natterjack toad (Epidalea calamita) in temporary ponds. Our results showed that reproductive success was only possible for seven years (20.6%). We found that reproductive success is positively related to the accumulated spring precipitation, while negatively related to mean spring temperature and spring evaporation. This study highlights the importance of conserving and restoring amphibian breeding habitats in order to minimize the potential impacts of climate change and habitat loss.

A host-directed adjuvant resuscitates and sensitizes intracellular bacterial persisters to antibiotics.

There are two major problems in the field of antimicrobial chemotherapy-antibiotic resistance and antibiotic tolerance. In the case of antibiotic tolerance, antibiotics fail to kill the bacteria as their phenotypic state affords them protection from the bactericidal activity of the antibiotic. Antibiotic tolerance can affect an entire bacterial population, or a subset of cells known as persister cells. Interaction with the host induces the formation of persister cells in numerous pathogens, with reactive oxygen and nitrogen species production being heavily implicated in the collapse of bacterial energy levels and entrance into an antibiotic tolerant state. Here, we developed a high-throughput screen to identify energy modulators for intracellular Staphylococcus aureus . The identified compound, KL1 , increases intracellular bacterial energy and sensitizes the persister population to antibiotics, without causing cytotoxicity or bacterial outgrowth. We demonstrate that KL1 exhibits adjuvant activity in a murine model of S. aureus bacteremia and intracellular infection of Salmonella Typhimurium . Transcriptomic analysis and further studies on its mechanism of action reveal that KL1 modulates host immune response genes and suppresses the production of reactive species in host macrophages, alleviating one of the major stressors that induce antibiotic tolerance. Our findings highlight the potential to target intracellular persister cells by stimulating their metabolism and encourage larger efforts to address antibiotic tolerance at the host-pathogen interface, particularly within the intracellular milieu.

A prolonged outbreak of tuberculosis associated with an intellectual disability daycentre in Ireland

Abstract One of the factors impeding tuberculosis elimination in low burden countries is its persistence and concentration in vulnerable populations. This is a complex, prolonged Tuberculosis (TB) outbreak in a daycentre for adults with intellectual disability in Ireland. This is a particularly vulnerable population with special considerations for Public Health (PH) management. There are eight cases of active TB, 46 cases of Latent TB Infection (LTBI) and a cumulative total of 116 contacts associated with this outbreak, with diagnosis spanning 15 years. The last three cases were identical on Whole Genome Sequencing. The index case was an Irish-born, Caucasian, social care worker, with smear positive pulmonary TB, who was symptomatic in the facility for three months prior to diagnosis. Case 2 was a household contact of the index case and the other 6 cases were Service Users (SUs) at the facility. At least five of the subsequent seven cases are secondary cases of the index case. Significant to this outbreak was the change in Irish guidance, 2010, relating to the management of contacts of cases. Following the notification of the most recent case, July 2023, the Outbreak Control Team decided a retrospective review be conducted of all SU contacts of the seven cases associated with the facility. The contacts were stratified according to hierarchical risk. A total of six contacts met the criteria for review and offered screening, re-screening or treatment as appropriate. In this outbreak 21.8% of the total contacts and 16.1% of SU contacts completed treatment for LTBI. The significance of this outbreak lies in its duration, infectivity of the index case and particular vulnerabilities of the SUs. There were issues with overcrowding and difficulties in relation to symptom recognition, diagnosis and treatment. The PH team tailored their approach to meet the SU needs, demonstrating the importance of person-centred contact tracing in the disruption of transmission. Key messages • A factor impeding tuberculosis elimination in low burden countries is it’s persistence and concentration in vulnerable populations. • Adapting a patient-centred approach to contact tracing can lead to higher participation rate and the disruption of infection transmission.

Life's a ditch: demographic history and environmental factors shape fine-scale local adaptation within small populations of brook trout

Many studies have investigated the loss of adaptive potential in endangered or exploited species experiencing recent population declines. Less research has studied adaptive genomic variation in small populations known to have persisted for long periods, despite the unique contribution that such populations provide for determining mechanisms underlying population persistence in evolutionary and conservation modeling. Small populations of Brook trout (Salvelinus fontinalis) have persisted in Cape Race, Newfoundland for >12,000 years. We used genotyping-by-sequencing data to investigate the demographic history and adaptive genomic variation of 26 populations with effective population sizes (Ne) ranging from 11 to 442, and to explore mechanisms underlying long-term persistence. We show that all populations experienced demographic declines following postglacial colonization but have remained in their current, small Ne state for thousands of years. We also reveal greater homozygosity in adaptive alleles within the smallest populations and found signatures of adaptive divergence in small populations relating to several abiotic and biotic factors. Our study illustrates how the demographic history of a species can influence the adaptive dynamics of small populations persisting over long time periods.

Summer roost site selection of a declining bat species

AbstractSummer habitats are critical to bat population persistence as they support multiple life history stages, including maternity colonies, nursery sites, and foraging locations. The tricolored bat (Perimyotis subflavus) is a hibernating North American bat species that uses forested landscapes during summer months; however, information on the summer habitat requirements is limited. The objective of this work was to quantify the characteristics of roost sites selected by tricolored bats during summer months. We captured, tagged, and tracked 15 bats using radio-telemetry to 55 roost locations. At each roost, we recorded roost habitat characteristics and other forest characteristics within a 0.1 ha circular plot surrounding the roost tree and a 1 km buffer at the landscape scale. We repeated these measurements for three random trees per roost tree to characterize available habitat for selection. We used a suite of mixed conditional logistic regression models to test multiple factors known to influence roost-site selection for various bat species and compared using Akaike information criterion to select the best model. The top model at the roost scale demonstrated that roost selection was influenced by roost tree height, while the landscape scale was influenced by deciduous forest and distance to roads. There is a critical information gap for the ongoing recovery of tricolored bats; better understanding of summer habitat and proper forest management implications, as well as information on scale-specific habitat selection, is needed to better understand tricolored bat management needs.

Role of DNA Double-Strand Break Formation in Gyrase Inhibitor-Mediated Killing of Nonreplicating Persistent Mycobacterium tuberculosis in Caseum.

Tuberculosis is the leading cause of mortality by infectious agents worldwide. The necrotic debris, known as caseum, which accumulates in the center of pulmonary lesions and cavities is home to nonreplicating drug-tolerant Mycobacterium tuberculosis that presents a significant hurdle to achieving a fast and durable cure. Fluoroquinolones such as moxifloxacin are highly effective at killing this nonreplicating persistent bacterial population and boosting TB lesion sterilization. Fluoroquinolones target bacterial DNA gyrase, which catalyzes the negative supercoiling of DNA and relaxes supercoils ahead of replication forks. In this study, we investigated the potency of several other classes of gyrase inhibitors against M. tuberculosis in different states of replication. In contrast to fluoroquinolones, many other gyrase inhibitors kill only replicating bacterial cultures but produce negligible cidal activity against M. tuberculosis in ex vivo rabbit caseum. We demonstrate that while these inhibitors are capable of inhibiting M. tuberculosis gyrase DNA supercoiling activity, fluoroquinolones are unique in their ability to cleave double-stranded DNA at low micromolar concentrations. We hypothesize that double-strand break formation is an important driver of gyrase inhibitor-mediated bactericidal potency against nonreplicating persistent M. tuberculosis populations in the host. This study provides general insight into the lesion sterilization potential of different gyrase inhibitor classes and informs the development of more effective chemotherapeutic options against persistent mycobacterial infections.

The Evolution of Gene Expression Plasticity During Adaptation to Salt in Chlamydomonas reinhardtii.

When environmental change is rapid or unpredictable, phenotypic plasticity can facilitate adaptation to new or stressful environments to promote population persistence long enough for adaptive evolution to occur. However, the underlying genetic mechanisms that contribute to plasticity and its role in adaptive evolution are generally unknown. Two main opposing hypotheses dominate-genetic compensation and genetic assimilation. Here, we predominantly find evidence for genetic compensation over assimilation in adapting the freshwater algae Chlamydomonas reinhardtii to 36 g/L salt environments over 500 generations. More canalized genes in the high-salt (HS) lines displayed a pattern of genetic compensation (63%) fixing near or at the ancestral native expression level, rather than genetic assimilation of the salt-induced level, suggesting that compensation was more common during adaptation to salt. Network analysis revealed an enrichment of genes involved in energy production and salt-resistance processes in HS lines, while an increase in DNA repair mechanisms was seen in ancestral strains. In addition, whole-transcriptome similarity among ancestral and HS lines displayed the evolution of a similar plastic response to salt conditions in independently reared HS lines. We also found more cis-acting regions in the HS lines; however, the expression patterns of most genes did not mimic that of their inherited sequence. Thus, the expression changes induced via plasticity offer temporary relief, but downstream changes are required for a sustainable solution during the evolutionary process.

Evaluating intra- and inter-life stage density-dependent dynamics for management of perennial amphidromous fish.

Compensatory density-dependent (DD) processes play an integral role in fisheries management by underpinning fundamental population demographics. However, DD processes are often assessed only for specific life stages, likely resulting in misleading evaluations of population limitations. Here, we assessed the relative roles of intra- and inter-life stage DD interactions in shaping the population dynamics of perennial freshwater fish with demographically open populations. Specifically, we monitored populations of amphidromous banded kōkopu (Galaxias fasciatus), giant kōkopu (Galaxias argenteus), and shortjaw kōkopu (Galaxias postvectis) in five streams where migratory post-larvae are fished and in three no-take ("closed") streams located on New Zealand's South Island for two years. Using mark-recapture data, we investigated whether fishing altered densities of "small" (non-territorial recruits ≤1-year-old) and "large" (territorial fish >1-year-old) kōkopu size classes, and how subsequent density shifts affected the apparent survival and growth of each class while controlling for other confounding factors (e.g., habitat characteristics). We found that closed areas had substantially greater biomass of small kōkopu, particularly following the two-month fishing season. Despite this greater influx of recruits, there was no difference in the biomass of large kōkopu at the species level, or as a combined assemblage between stream types. This indicated that although fishing of post-larvae reduced recruit influxes into adult habitats, there was no subsequent evidence of recruitment-limitation within adult populations. Instead, kōkopu demographics were underpinned by intra- and inter-life stage DD competition and predation. Greater large fish densities played a key role in regulating the survival, growth, and/or presence of various kōkopu classes. In contrast, greater small fish densities had positive effects on the growth of opportunistic and insectivorous congeners, likely due to cannibalism and altered foraging behaviors, respectively. Our study details the prominent role of intra- and inter-life stage DD interactions in regulating the population dynamics of perennial migratory freshwater fishes, even in populations with inhibited recruit and juvenile availability. We emphasize the importance for fisheries management to implement recruitment dependencies and complex interactions between distinct life stages to avoid deleterious DD responses and ensure population persistence.

Tuft Dynamics and the Reproductive Phenology of Zostera caespitosa on the Southern Coast of Korea

The aim of study is to determine which environmental factors could influence the biological traits of Z. caespitosa, a unique tuft-forming seagrass. This study examined the dynamics of tufts and the growth of Z. caespitosa, along with the environmental factors. The reproductive traits were also examined to estimate the potential importance of sexual reproduction in population persistence. The density of tufts remained constant, and no new tufts produced through seedling recruitment were observed throughout the sampling period. On the other hand, the tuft size and growth exhibited clear seasonal manners and strong correlations with the water temperature, indicating that water temperature regulates the tuft dynamics and growth. The optimal growth temperature for Z. caespitosa at the study site was approximately ~22.5 °C during early summer, with growth severely inhibited during periods of high-water temperatures. Z. caespitosa was characterized by a low flowering percentage and fewer inflorescences, resulting in extremely low potential seed production. Z. caespitosa maintained its populations through clonal tuft growth with low sexual reproduction and restricted growth at high water temperatures. Hence, this seagrass species may be vulnerable to disturbances, exhibiting low resilience and facing a high risk of becoming a threatened species in coastal waters.