Reintroduction is a crucial step in the conservation efforts aiming to restore ecosystems and protect threatened species. However, studies that incorporate and evaluate the effect of plant reintroduction are scarce. A study on a population of Cephalocereus polylophus, a vulnerable cactus endemic to the southern Chihuahuan Desert, allowed us to evaluate the effect of seedling reintroduction and protection on the viability of this population. An integral projection model was used on a 5-year dataset to forecast population size over a century, and to simulate scenarios of seedling survival and protection. The study revealed an asymptotic population growth rate (λ) of 0.97 (95% CI = 0.96 – 0.99). Simulating the seedling survival and an increase in the seedling bank translated into a λ that showed only a slight increase, but remained below one, mainly because the recruitment and survival of small individuals were insufficient to compensate for the population decline. Protecting seedlings against herbivores and increasing their survival to 96.5% resulted in a larger population size (~ 8% average increase) and delayed extinction, in comparison with an unmanaged scenario with 60% survival rate. This demonstrates that increasing seedling survival rates through protection and reintroduction efforts can only be conceived as a complementary conservation strategy to those focused on preserving existing individuals. Effective reintroduction strategies can help delay the extinction of the population of this cactus, but the conservation of the current population and its habitat is pivotal for its future survival.

In many organisms, environmental temperature is a key determinant of the reproductive season, although physiological thermal responses related to reproduction often vary among taxa. Comparative analyses of reproductive seasonality within and between species can provide insights into the physiological constraints and local adaptation of reproductive traits in wild populations. This study examined wild populations of medaka (Oryzias latipes species complex). Although the photo-thermal thresholds for gonadal maturation in this species have been studied extensively in laboratory settings, geographical patterns of seasonality in gonad maturation, fecundity, and recruitment have not been thoroughly investigated in wild populations. We examined seasonal changes in gonad weight and the proportions of juveniles in wild populations of medaka at different latitudes. Our findings showed that seasonal changes in gonad weight were more pronounced in a high-latitude population in Aomori compared to a low-latitude population in Okinawa, irrespective of sex. Annual average proportions of juveniles tended to be higher in the Okinawa population compared to the Aomori and Chiba populations, suggesting a shorter recruitment period in high-latitude populations. A comparison of body size and egg number indicated that fecundity was relatively higher in high-latitude populations. We discuss whether gonad maturation at high latitudes can be explained by seasonal changes in temperature. Interpopulation differences in the gonadosomatic index and fecundity support the adaptive evolution of increased reproductive investment in high-latitude environments with shorter reproductive seasons. Additionally, trade-offs between survival and reproduction may influence ecological longevity and annual recruitment dynamics in these populations.

Speciation – the process by which new species arise – is fundamentally influenced by population-level factors such as population size and demographic dynamics. Here, we review how population size and its dynamics shape speciation mechanisms and the generation of biodiversity across evolutionary scales. Small populations can undergo rapid genetic changes via drift and founder events, potentially promoting speciation, whereas large populations harbour greater genetic diversity and adaptive potential, influencing divergence in different ways. We examine how genetic drift and gene flow interact to facilitate or impede speciation under various scenarios and how extinction risk during adaptation affects the development of reproductive isolation. Finally, we explore how speciation rates and the persistence of populations/species over time are related in theoretical models. We highlight insights from mathematical models – especially those explicitly incorporating population size – and identify open questions for future research.

The human-brown bear Ursus arctos conflicts (HBCs) have increased in Hokkaido in recent years. The recent increase in HBCs can be attributed to changes in both the bear and human sides. Brown bears in Hokkaido were added to the list of “Designated Wildlife Species for Control” and the Hokkaido Brown Bear Management Plan (Phase 2) was reviewed in 2024, and the plan includes the concept of active adaptive management, zoning management, and population management when the total population exceeds the region’s acceptable level. HBCs management should be considered as a risk management strategy for natural disasters, consisting of a combination of crisis, exposure, and vulnerability. In an adaptive management scheme, the management policy is determined every few years by each phase based on the annual conflict levels and population levels for each management unit. Zoning management aims for the coexistence of humans and bears through spatial segregation. When implementing management measures, the land is divided into bear habitat as forested areas in the deep mountains, forests around human settlements, human settlements as rural areas, and urban areas. To promote brown bear management in the future, necessary measures and monitoring and its implementation system are discussed based on the concept of risk management and zoning management.

Several attempts have been made to understand the population dynamics of fishery resources, such as tuna species using an integrated analysis model with multiple data sources. However, estimating absolute abundance levels in practical stock assessments remains a challenge. Close-kin mark–recapture (CKMR) methods provide information about the number of adults in a population using close-kinship pairs identified by genetic markers and statistical methods. In this study, we compared three methods for kinship identification using different algorithms in samples of wild Pacific bluefin tuna genotyped across 5,029 genome-wide single nucleotide polymorphisms in 4,108 samples. The fraRF method we developed employs pairwise identity-by-descent values as inputs for random-forest classification. The other two methods were CKMRsim and COLONY, which have been published and applied in several studies. These three methods were applied to the actual genotyping data with moderate missing genotypes, in addition to the pseudo-generated genotyping data for the simulation test. The simulation test mimicked genotyping data with physical linkage as well as genetic characteristics similar to those of actual samples. The three methods resulted in different numbers of inferred kinship pairs for both generated and actual data. Particularly for the half-sibling pairs, considerable number of false-positive and false-negative existed in the identification results. The differences in kinship identification results were interpreted based on a simulation test. This study may promote the understanding of behavior in each software when applying the software to SNP data with moderate missing genotypes as in the case of this study.

In the context of initiatives focused on captive breeding and reintroduction of endangered animal species, it is crucial to minimize any bias in reproductive success during the reintroduction phase in order to preserve genetic diversity. One population of Tachysurus ichikawai, a critically endangered bagrid catfish endemic to Japan, faces a threat from the construction of a dam. To address this, a captive breeding program followed by translocation is being implemented. Multiple breeding families are involved in this process; however, if there is a bias in reproductive success among them after release, it will result in a decline in genetic diversity. To identify potential biases in breeding lineages, we conducted kinship analysis between individuals born at the release site and breeding individuals. Because there were no samples available from the released individuals themselves, we examined distant kinship relationships, such as grandparent–grandchild and uncle–aunt–nephew–niece relationships, using a substantial number of single-nucleotide polymorphisms obtained from the whole genome re-sequence. Our findings indicate no bias between lineages in the first year after reintroduction, but a significant bias in the second year, emphasizing the need for continuous management and monitoring of reintroduced populations. This study demonstrates that monitoring kinship after reintroduction can correct lineage bias, which is critical for the prompt restoration of genetic diversity.

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

The recovery of mammalian species in the US Midwest through natural recolonization constitutes a conservation success story, yet management remains challenging due to many unknowns related to population dynamics and abundance. Abundance is a critical parameter for management decisions, and estimating the density and abundance of elusive species, such as terrestrial carnivores, remains challenging despite recent technological advances. In this study, we evaluated density and abundance of a recovering carnivore species, the bobcat (Lynx rufus) in two areas of Ohio using non-invasive DNA from scat. The target areas in eastern and southern Ohio have been shown to have uneven dynamics and recolonization success and we expected that this would be reflected in differences in density and abundance. We collected 298 bobcat scats between July 2018 and April 2019 on 150 km of repeated transects. Of these, 102 scats were successfully genotyped, and 55 individuals were identified (33 in eastern Ohio and 22 in southern Ohio). Using Spatially Explicit Capture-Recapture models, we estimated 17.9 ± 4.3 and 11.3 ± 2.9 bobcats/100 km2 in eastern and southern Ohio study areas, respectively. Our results support prior telemetry data which indicated that bobcats in eastern Ohio had smaller home-ranges than bobcats in southern Ohio, and thus could support a higher density of individuals. The higher densities were similar to other eastern US populations and are much higher than other Midwestern recovering populations. Our results provide a snapshot of the population status and can be used to determine sustainable management strategies for Ohio’s bobcat population