Genetic diversity is essential for populations to adapt to changing environments. Measures of genetic diversity are often based on selectively neutral markers, such as microsatellites. Genetic ...diversity to guide conservation management, however, is better reflected by adaptive markers, including genes of the major histocompatibility complex (MHC). Our aim was to assess MHC and neutral genetic diversity in two contrasting bottlenose dolphin (Tursiops aduncus) populations in Western Australia—one apparently viable population with high reproductive output (Shark Bay) and one with lower reproductive output that was forecast to decline (Bunbury). We assessed genetic variation in the two populations by sequencing the MHC class II DQB, which encompasses the functionally important peptide binding regions (PBR). Neutral genetic diversity was assessed by genotyping twenty‐three microsatellite loci.
We confirmed that MHC is an adaptive marker in both populations. Overall, the Shark Bay population exhibited greater MHC diversity than the Bunbury population—for example, it displayed greater MHC nucleotide diversity. In contrast, the difference in microsatellite diversity between the two populations was comparatively low.
Our findings are consistent with the hypothesis that viable populations typically display greater genetic diversity than less viable populations. The results also suggest that MHC variation is more closely associated with population viability than neutral genetic variation. Although the inferences from our findings are limited, because we only compared two populations, our results add to a growing number of studies that highlight the usefulness of MHC as a potentially suitable genetic marker for animal conservation. The Shark Bay population, which carries greater adaptive genetic diversity than the Bunbury population, is thus likely more robust to natural or human‐induced changes to the coastal ecosystem it inhabits.
Genetic diversity is crucial for populations to adapt to changing environments and is thus an important indicator for conservation. Our study compares adaptive genetic diversity of the major histocompatibility complex (MHC) and neutral genetic diversity two contrasting bottlenose dolphin populations that greatly differ with respect to population viability. The results suggest that population viability is better reflected by MHC diversity than by neutral genetic diversity.
1. Sensitivity analyses that assess the impact of changing vital rates on population growth have been widely used to guide conservation. If implemented with caution, they can provide guidance as to ...which management actions will optimize conservation outcomes. 2. In this review, we first focus on the commonly used proportional sensitivity and elasticity analyses that change each vital rate by equal proportions, to assess their importance for wildlife management. These types of analyses also feature potential pitfalls and limitations, including (1) Each vital rate is usually on a different scale. Without appropriate scaling this can result in a flawed evaluation of the importance of vital rates. (2) Vital rates rarely change at equal proportions in nature. This can bring about misguided management recommendations on the basis of vital rate changes that are unrealistic. (3) Proportional sensitivity analyses often do not reflect the feasibility and effectiveness of altering particular demographic parameters. Consequently, relying solely on proportional sensitivities or elasticities can lead to flawed evaluation of the importance of vital rates and thus prioritization of management options that are unrealistic or ineffective. 3. We outline alternative approaches, which involve assessing the impact of threats, the relative demography of stable and declining populations, the effect of observable variation of vital rates on population viability, and the potential effects of feasible management scenarios. 4. Synthesis and applications. Sensitivity analyses are useful tools to guide wildlife management. If implemented and interpreted with care, sensitivity analyses can identify key demographic parameters and threats to population viability. However, their usefulness is limited, when applied without careful evaluation as to whether the perturbations evaluated are realistic, feasible and meet the need of wildlife managers. We caution against the over-reliance on proportional sensitivity and elasticity analyses and point to alternative approaches, including life-stage simulation analysis, vital rate sensitivity analysis or manual perturbations.
Climate change is predicted to affect host–parasite interactions, and for some hosts, parasite infection is expected to increase with rising temperatures. Global population declines of important ...pollinators already have been attributed to climate change and parasitism. However, the role of climate in driving parasite infection and the genetic basis for pollinator hosts to respond often remain obscure. Based on decade‐long field data, we investigated the association between climate and Nosema bombi (Microsporidia) infection of buffed‐tailed bumblebees (Bombus terrestris), and whether host genotypes play a role. For this, we genotyped 876 wild bumblebee queens and screened for N. bombi infection of those queens between 2000 and 2010. We recorded seven climate parameters during those 11 years and tested for correlations between climate and infection prevalence. Here we show that climatic factors drive N. bombi infection and that the impact of climate depends on mitochondrial DNA cytochrome oxidase I (COI) haplotypes of the host. Infection prevalence was correlated with climatic variables during the time when queens emerge from hibernation. Remarkably, COI haplotypes best predict this association between climatic factors and infection. In particular, two host haplotypes (“A” and “B”) displayed phenotypic plasticity in response to climatic variation: Temperature was positively correlated with infection of host haplotype B, but not haplotype A. The likelihood of infection of haplotype A was associated with moisture, conferring greater resistance to parasite infection during wetter years. In contrast, infection of haplotype B was unrelated to moisture. To the best of our knowledge, this is the first study that identifies specific host genotypes that confer differential parasite resistance under variable climatic conditions. Our results underscore the importance of mitochondrial haplotypes to ward off parasites in a changing climate. More broadly, this also suggests that COI may play a pertinent role in climate change adaptations of insect pollinators.
Our decade‐long study shows that climate change impacts parasite infection of wild bumblebees (Bombus terrestris), depending on the genotypes of the bumblebees. With increasing temperatures and drier conditions, more bumblebees were infected. Surprisingly, this impact of climate change depends on mitochondrial DNA variants of the host. Bumblebees who possessed one variant were more resilient to infection under warmer, wetter conditions. In contrast, those with the other variant showed greater resilience to parasite infection in a cooler, drier climate. Therefore, these mitochondrial variants may play a crucial role for bumblebees to adapt to parasite infection in a changing climate.
Human‐caused mortality of wildlife is a pervasive threat to biodiversity. Assessing the population‐level impact of fisheries bycatch and other human‐caused mortality of wildlife has typically relied ...upon deterministic methods. However, population declines are often accelerated by stochastic factors that are not accounted for in such conventional methods. Building on the widely applied potential biological removal (PBR) equation, we devised a new population modeling approach for estimating sustainable limits to human‐caused mortality and applied it in a case study of bottlenose dolphins affected by capture in an Australian demersal otter trawl fishery. Our approach, termed sustainable anthropogenic mortality in stochastic environments (SAMSE), incorporates environmental and demographic stochasticity, including the dependency of offspring on their mothers. The SAMSE limit is the maximum number of individuals that can be removed without causing negative stochastic population growth. We calculated a PBR of 16.2 dolphins per year based on the best abundance estimate available. In contrast, the SAMSE model indicated that only 2.3–8.0 dolphins could be removed annually without causing a population decline in a stochastic environment. These results suggest that reported bycatch rates are unsustainable in the long term, unless reproductive rates are consistently higher than average. The difference between the deterministic PBR calculation and the SAMSE limits showed that deterministic approaches may underestimate the true impact of human‐caused mortality of wildlife. This highlights the importance of integrating stochasticity when evaluating the impact of bycatch or other human‐caused mortality on wildlife, such as hunting, lethal control measures, and wind turbine collisions. Although population viability analysis (PVA) has been used to evaluate the impact of human‐caused mortality, SAMSE represents a novel PVA framework that incorporates stochasticity for estimating acceptable levels of human‐caused mortality. It offers a broadly applicable, stochastic addition to the demographic toolbox to evaluate the impact of human‐caused mortality on wildlife.
Resumen
La mortalidad de la fauna causada por humanos es una amenaza continua para la biodiversidad. El análisis del impacto a nivel poblacional de la captura pesquera incidental y otras causas humanas de la mortalidad de la fauna comúnmente ha dependido de métodos determinísticos. Sin embargo, las declinaciones poblacionales con frecuencia se aceleran por los factores estocásticos que no son considerados en dichos métodos convencionales. A partir de la ecuación de extirpación biológica potencial (EBP) de extensa aplicación diseñamos una nueva estrategia de modelación poblacional para estimar los límites sustentables de la mortalidad causada por humanos y la aplicamos en un estudio de caso de los delfines nariz de botella afectados por la captura en una pesquería australiana de arrastre demersal. Nuestra estrategia, denominada mortalidad antropogénica sustentable en ambientes estocásticos (MASAM) incorpora la estocasticidad ambiental y demográfica, incluyendo la dependencia que tienen las crías por sus madres. El límite MASAM es el número máximo de individuos que pueden extirparse sin causar un crecimiento poblacional estocástico negativo. Calculamos un EBP de 16.3 delfines por año con base en la mejor estimación de abundancia disponible. Como contraste, el modelo MASAM indicó que sólo podían extirparse entre 2.3 y 8.0 delfines anualmente sin ocasionar una declinación poblacional en un ambiente estocástico. Estos resultados sugieren que las tasas reportadas de captura incidental no son sustentables a largo plazo, a menos que las tasas reproductivas sean sistemáticamente más altas que el promedio. La diferencia entre el cálculo determinístico del EBP y los límites de MASAM mostró que los enfoques determinísticos pueden subestimar el verdadero impacto de la mortalidad de la fauna causada por humanos. Lo anterior resalta la importancia de integrar la estocasticidad al evaluar el impacto de la captura incidental y otras causas humanas de la mortalidad como la caza, las medidas letales de control y las colisiones con turbinas de viento. Aunque el análisis de viabilidad poblacional (AVP) se ha utilizado para evaluar el impacto de la mortalidad causada por humanos, MASAM representa un marco novedoso de AVP que incorpora la estocasticidad para estimar los niveles aceptables de mortalidad causada por humanos. Este enfoque ofrece una adición estocástica de aplicación generalizada para las herramientas demográficas usadas para evaluar el impacto de la mortalidad causada por humanos sobre la fauna.
【摘要】
在不断变化的情景下估计野生动物死亡率的持续性限度的随机模型
人类造成的野生动物死亡是对生物多样性的普遍威胁。目前, 通常依赖于确定性方法来评估渔业副渔获物和其它人为造成的野生动物死亡在种群水平上的影响。然而, 随机因素往往会加速种群数量的下降, 但这种常规方法没有将其纳入考虑。我们在已得到广泛应用的生物可移除潜在量(Potential Biological Removal, PBR)方程的基础上, 设计了一种新的种群建模方法来估计人为造成的死亡的可持续限度, 并将其应用于澳大利亚底层拖网渔业中受影响的瓶鼻海豚的案例研究。我们的方法可以称为“随机环境中的可持续人为影响死亡率(SAMSE)”, 包含了环境和种群的随机性, 还包括了后代对母亲的依赖性。SAMSE的极限是指在不引起负面的种群随机增长的情况下可以移除的最大个体数。我们根据现有最佳的丰度估计, 计算出海豚的生物可移除潜在量为每年16.2头。相比之下, SAMSE模型则显示, 在随机环境中, 为了不引起种群下降, 每年只能移除2.3至8.0头海豚。这些结果表明, 除非繁殖率持续高于平均水平, 否则长期来看报告的副渔获率是不可持续的。确定性的PBR计算和SAMSE限制之间的差异表明, 确定性方法可能低估了人为造成野生动物死亡的真实影响。这突出了整合随机性在评估副渔获或其它人为造成的死亡(如狩猎、灭杀控制措施和风力涡轮机碰撞)对野生动物的影响中的重要性。尽管种群生存力分析(PVA)已被用于评估人为造成死亡的影响, 但SAMSE代表了一个包含随机性的PVA新框架, 可以用于估计人为造成死亡的可接受水平。它为种群统计学工具补充了一种广泛适用的随机性方法, 以评估人类造成的死亡对野生动物的影响。【翻译:胡怡思;审校:聂永刚】
Article impact statement: The new SAMSE model incorporates stochasticity to provide better estimates of sustainable limits to wildlife mortality in a changing world.
The antagonistic relationship between parasites and their hosts is strongly influenced by genotype-by-genotype interactions. Defense against parasitism is commonly studied in the context of immune ...system-based mechanisms and, thus, the focus in the search for candidate genes in host-parasite interactions is often on immune genes. In this study, we investigated the association between prevalence of parasite infection and host mitochondrial DNA (mtDNA) haplotypes in two natural populations of bumblebees (Bombus terrestris). The two most common haplotypes of the host populations, termed A and B, differ by a single nonsynonymous nucleotide substitution within the coding region of cytochrome oxidase I, an important player in metabolic pathways. We screened infection by Nosema bombi, a common endoparasite of bumblebees, and the corresponding host mtDNA-haplotype frequencies in over 1400 bumblebees between 2000 and 2010. The island population of Gotland showed lower mtDNA diversity compared to the mainland population in Switzerland. Over time, we observed large fluctuations in infection prevalence, as well as variation in host haplotype frequencies in both populations. Our long-term observation revealed that N. bombi infection of specific host genotypes is transient: We found that with increasing infection prevalence, proportionally more individuals with haplotype B, but fewer individuals with haplotype A were infected. This suggests that the presence of N. bombi in specific host genotypes relates to infection prevalence. This may be a result of parasite competition, or differential resilience of host types to ward off infections. The findings highlight the important role of host mtDNA haplotypes in the interaction with parasites.
•We screened Nosema bombi infection and mtDNA haplotypes in over 1400 bumblebees.•Infection of specific host genotypes is transient in two bumblebee populations.•With increasing infection prevalence, more B-haplotype hosts were infected.•Reversely, with increasing inf. prevalence, fewer A-haplotype hosts were infected.•This suggests that parasite presence in host haplotypes relates to prevalence.
The forecast for the viability of populations depends upon metapopulation dynamics: the combination of reproduction and mortality within populations, as well as dispersal between populations. This ...study focuses on an Indo‐Pacific bottlenose dolphin (Tursiops aduncus) population in coastal waters near Bunbury, Western Australia. Demographic modeling of this population suggested that recent reproductive output was not sufficient to offset mortality. Migrants from adjacent populations might make up this deficit, so that Bunbury would act as a “sink,” or net recipient population. We investigated historical dispersal in and out of Bunbury, using microsatellites and mitochondrial DNA of 193 dolphins across five study locations along the southwestern Australian coastline. Our results indicated limited gene flow between Bunbury and adjacent populations. The data also revealed a net‐dispersal from Bunbury to neighboring populations, with microsatellites showing that more than twice as many individuals per generation dispersed out of Bunbury than into Bunbury. Therefore, in historic times, Bunbury appears to have acted as a source population, supporting nearby populations. In combination with the prior finding that Bunbury is currently not producing surplus offspring to support adjacent populations, this potential reversal of source‐sink dynamics may have serious conservation implications for Bunbury and other populations nearby.
It has been proposed that in slow‐growing vertebrate populations survival generally has a greater influence on population growth than reproduction. Despite many studies cautioning against such ...generalizations for conservation, wildlife management for slow‐growing populations still often focuses on perturbing survival without careful evaluation as to whether those changes are likely or feasible. Here, we evaluate the relative importance of reproduction and survival for the conservation of two bottlenose dolphin (Tursiops cf aduncus) populations: a large, apparently stable population and a smaller one that is forecast to decline. We also assessed the feasibility and effectiveness of wildlife management objectives aimed at boosting either reproduction or survival. Consistent with other analytically based elasticity studies, survival had the greatest effect on population trajectories when altering vital rates by equal proportions. However, the findings of our alternative analytical approaches are in stark contrast to commonly used proportional sensitivity analyses and suggest that reproduction is considerably more important. We show that
in the stable population reproductive output is higher, and adult survival is lower;
the difference in viability between the two populations is due to the difference in reproduction;
reproductive rates are variable, whereas survival rates are relatively constant over time;
perturbations on the basis of observed, temporal variation indicate that population dynamics are much more influenced by reproduction than by adult survival;
for the apparently declining population, raising reproductive rates would be an effective and feasible tool to reverse the forecast population decline; increasing survival would be ineffective.
Our findings highlight the importance of reproduction – even in slow‐growing populations – and the need to assess the effect of natural variation in vital rates on population viability. We echo others in cautioning against generalizations based on life‐history traits and recommend that population modeling for conservation should also take into account the magnitude of vital rate changes that could be attained under alternative management scenarios.
On the basis of conventional sensitivity analyses, it is often asserted that wildlife management of slow‐growing animal populations should focus on (adult) survival. We present various lines of evidence that for the conservation of two dolphin populations and other slow‐growing vertebrate populations, reproduction – not survival – is the key to success.
Inherent difficulties in determining the sex of free-ranging sexually monomorphic species often prevents a sex-specific focus on estimating abundance, movement patterns and survival rates. This study ...provides insights into sex-specific population parameters of Indo-Pacific bottlenose dolphins (Tursiops aduncus). Systematic, boat-based photo-identification surveys (n = 417) were conducted year-round from 2007-2013 in coastal and estuarine waters off Bunbury, Western Australia. Pollock’s Robust Design was used to quantify population parameters for three datasets: i) adults and juveniles combined, ii) adult females and iii) adult males. For all datasets, abundance estimates varied seasonally, with general highs during summer and/or autumn, and lows during winter. Dolphins had seasonally structured temporary emigration rates with similar trends between sexes. The derived return rate (1-γ’) of temporary emigrants into the study area was highest from winter to spring, indicating that dolphins had a high probability of return into the study area during spring. We suggest that the return of dolphins into the study area and increase in abundance is influenced by the breeding season (summer/autumn). Prey availability is likely a main driver responsible for the movement of dolphins out of the study area during winter. Seasonal apparent survival rates were constant and high (0.98-0.99) for all datasets. High apparent survival rates suggest there is no permanent emigration from the study area. Our sex-specific modeling approach offers a comprehensive interpretation of the population dynamics of a top predator in a coastal and estuarine environment and acts as a model for future sex-based population studies on sexually monomorphic species.
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