Population Crashes Research Articles

Common, curled or miscellaneous: The need for species-specific recordings of octopuses to inform stock assessments

The curled octopus Eledone cirrhosa and common octopus Octopus vulgaris could be considered resident to the waters around the UK, though the latter is considered rare following historic population crashes and severe range contractions. There is evidence of an emerging fishery for octopus in the UK though understanding population dynamics between the two species and producing meaningful stock assessments are difficult because most landings data are not species specific. This emerging fishery, together with the government’s plan for octopus to be included in fisheries management plans, and a growing desire among fishers and the public to have more fisheries certified for sustainability means there is a need for octopus landings data to be species specific. A similar case has existed for two species of megrim (Lepidorhombus whiffiagonis and L. boscii) whereby both species were initially subject to a single total allowable catch (TAC), however concerns about sustainability presented the need for the species to be assessed, and their fisheries managed, separately. We consider this work to be applicable to any other commercially important species which are currently assessed as a single unit but where localised populations may exist.

The Black Death and Consequences for Labor

Abstract From the perspective of the Black Death, the economic consequences for laborers in our unfolding pandemic, COVID-19, might come as a surprise. Instead of labor shortages benefiting workers, especially the unskilled, and narrowing the gap between rich and poor, our pandemic has sent economic inequality racing forward across the world with laborers’ health and material well-being plummeting. However, a closer examination of the Black Death suggests that the consequences for labor of the two pandemics may not be as different as first assumed. This essay explores the silver lining for labor after the dramatic crash in population caused by the Black Death and subsequent waves of plague during the second half of the fourteenth century. By first turning to Europe as a whole and then concentrating on Italy, this essay challenges notions that labor conditions and standards of living improved immediately after the Black Death's halving of populations and that these changes were almost universal across Europe or even within city-states, such as Florence, or in rural areas hosting different sorts of agricultural workers. In Italy, where real wages have been calculated, the Black Death's silver lining for laborers failed to arrive until two or three generations after 1348. Moreover, compressing economic inequality from the late fourteenth to the late fifteenth centuries spurred reactions from elites that wrought new inequalities in other spheres of activity.

Uncovering inbreeding, small populations, and strong genetic isolation in an Australian threatened frog, Litoria littlejohni

AbstractThe status of many amphibian populations remains unclear due to undetected declines driven by disease and difficulties in obtaining accurate population estimates. Here, we used genome complexity reduction-based sequencing technology to study the poorly understood Littlejohn’s treefrog, Litoria littlejohni across its fragmented distribution in eastern Australia. We detected five identifiable genetic clusters, with moderate to strong genetic isolation. At a regional scale, population isolation was likely driven by population crashes, resulting in small populations impacted by founder effects. Moderate genetic isolation was detected among populations on the Woronora Plateau despite short distances between population clusters. Evidence of recent declines was apparent in three populations that had very small effective population size, reduced genetic diversity and high inbreeding values. The rates of inbreeding detected in these populations combined with their small size leave these populations at elevated risk of extinction. The Cordeaux Cluster was identified as the most robust population as it was the largest and most genetically diverse. This study exemplifies the value of employing genetic methods to study rare, cryptic species. Despite low recapture rates using traditional capture-recapture demographic methods, we were able to derive population estimates, describe patterns of gene flow, and demonstrate the need for urgent conservation management.

From farm to forest – 50 years of ecological transformation on Mana Island, New Zealand

Ecological surveys of Mana Island, Wellington, in 1972 and 1975 confirmed that house mice (Mus musculus) were the only pest mammals present, and resulted in nationally significant populations of Cook Strait giant weta (Deinacrida rugosa) and of two threatened lizard species being confirmed or discovered. Photographs taken in June 1972 were re-taken in June 2022, and are used to document social and ecological change on the island over this 50-year interval. Mana Island was farmed until 1986, and has been a conservation reserve administered by the Department of Conservation (DOC) since 1987. Mice reached plague numbers after farm stock were removed, and caused a population crash of McGregor’s skink (Oligosoma macgregori). Following mouse eradication in 1989–90, the island has been free of introduced mammals. A major revegetation effort since 1987 included planting of more than 443,000 trees and shrubs over about 36% of the 217 ha island. For the last two decades, conservation management of the island has largely followed a comprehensive ecological restoration plan that was published in 1999. The Friends of Mana Island was formed in 1998, and has taken the lead role in most conservation initiatives on the island since then, in partnership with Ngāti Toa Rangatira (mana whenua) and DOC. In addition to the revegetation programme, weed control, and recreation of a wetland, 22 animal species have been translocated to the island, and several bird species have colonised naturally. Conservation successes and failures are described, and research relevant to restoration ecology undertaken on the island is summarised.

Addressing prey naivety in native mammals by accelerating selection for antipredator traits.

Harnessing natural selection to improve conservation outcomes is a recent concept in ecology and evolutionary biology and a potentially powerful tool in species conservation. One possible application is the use of natural selection to improve antipredator responses of mammal species that are threatened by predation from novel predators. We investigated whether long-term exposure of an evolutionary naïve prey species to a novel predator would lead to phenotypic changes in a suite of physical and behavioral traits. We exposed a founder population of 353 burrowing bettongs (Bettongia lesueur) to feral cats (Felis catus) over 5 years and compared the physical and behavioral traits of this population (including offspring) to a control (non-predator exposed) population. We used selection analysis to investigate whether changes in the traits of bettongs were likely due to phenotypic plasticity or natural selection. We also quantified selection in both populations before and during major population crashes caused by drought (control) and high predation pressure (predator-exposed). Results showed that predator-exposed bettongs had longer flight initiation distances, larger hind feet, and larger heads than control bettongs. Trait divergence began soon after exposure and continued to intensify over time for flight initiation distance and hind foot length relative to control bettongs. Selection analysis found indicators of selection for larger hind feet and longer head length in predator-exposed populations. Results of a common garden experiment showed that the progeny of predator-exposed bettongs had larger feet than control bettongs. Results suggest that long-term, low-level exposure of naïve prey to novel predators can drive phenotypic changes that may assist with future conservation efforts.

The population genomic legacy of the second plague pandemic

Human populations have been shaped by catastrophes that may have left long-lasting signatures in their genomes. One notable example is the second plague pandemic that entered Europe in ca. 1,347 CE and repeatedly returned for over 300 years, with typical village and town mortality estimated at 10%-40%.1 It is assumed that this high mortality affected the gene pools of these populations. First, local population crashes reduced genetic diversity. Second, a change in frequency is expected for sequence variants that may have affected survival or susceptibility to the etiologic agent (Yersinia pestis).2 Third, mass mortality might alter the local gene pools through its impact on subsequent migration patterns. We explored these factors using the Norwegian city of Trondheim as a model, by sequencing 54 genomes spanning three time periods: (1) prior to the plague striking Trondheim in 1,349 CE, (2) the 17th-19th century, and (3) the present. We find that the pandemic period shaped the gene pool by reducing long distance immigration, in particular from the British Isles, and inducing a bottleneck that reduced genetic diversity. Although we also observe an excess of large FST values at multiple loci in the genome, these are shaped by reference biases introduced by mapping our relatively low genome coverage degraded DNA to the reference genome. This implies that attempts to detect selection using ancient DNA (aDNA) datasets that vary by read length and depth of sequencing coverage may be particularly challenging until methods have been developed to account for the impact of differential reference bias on test statistics.

Disappearance of an ecosystem engineer, the white-lipped peccary (Tayassu pecari), leads to density compensation and ecological release

Given the rate of biodiversity loss, there is an urgent need to understand community-level responses to extirpation events, with two prevailing hypotheses. On one hand, the loss of an apex predator leads to an increase in primary prey species, triggering a trophic cascade of other changes within the community, while density compensation and ecological release can occur because of reduced competition for resources and absence of direct aggression. White-lipped peccary (Tayassu pecari—WLP), a species that typically co-occurs with collared peccary (Pecari tajacu), undergo major population crashes—often taking 20 to 30-years for populations to recover. Using a temporally replicated camera trapping dataset, in both a pre- and post- WLP crash, we explore how WLP disappearance alters the structure of a Neotropical vertebrate community with findings indicative of density compensation. White-lipped peccary were the most frequently detected terrestrial mammal in the 2006–2007 pre-population crash period but were undetected during the 2019 post-crash survey. Panthera onca (jaguar) camera trap encounter rates declined by 63% following the WLP crash, while collared peccary, puma (Puma concolor), red-brocket deer (Mazama americana) and short-eared dog (Atelocynus microtis) all displayed greater encounter rates (490%, 150%, 280%, and 500% respectively), and increased in rank-abundance. Absence of WLP was correlated with ecological release changes in habitat-use for six species, with the greatest increase in use in the preferred floodplain habitat of the WLP. Surprisingly, community-weighted mean trait distributions (body size, feeding guild and nocturnality) did not change, suggesting functional redundancy in diverse tropical mammal assemblages.

The impact of symbiotic population crash (or reduction) on microbiome structure and composition

To examine how the sterilization techniques affect the structure, composition and diversity of gut bacterial communities, we used antibiotics and eggs disinfection approaches to generate aposymbiotic and axenic flies, respectively. Fruit flies often bear complex communities which are greatly reduced by such treatments. Here, we examine the effect of these procedures on the structure of the remaining bacterial communities of Bactrocera dorsalis. The antibiotics (Norfloxacin and Ceftazedime) were administered to 1 day old adult flies through sugar meal for seven days, and eggs were surface sterilized and dechorionated to produce axenic lines. The flies were starved from protein before they were offered full diets for their maintenance. Antibiotic treatments and eggs disinfection resulted in significant reduction of the vast majority of gut bacteria, especially Proteobacteria, Firmicutes and Bacteroidetes. However, Actinobacteria, Cyanobacteria and Acidobacteria which were in minority in symbiotic flies increased in size after treatments. These results suggest that alterations of gut bacteria through the sterilization techniques used here are suitable for generating aposymbiotic and axenic flies for functional study of gut bacteria in fruit fly.

Are white-rumped vultures (Gyps bengalensis) scavengers or predators at a vulture safe feeding site of Nepal?

Abstract. Gautan R, Baral N, Sharma HP. 2022. Are white-rumped vultures (Gyps bengalensis) scavengers or predators at a vulture safe feeding site of Nepal?. Biodiversitas 23: 3808-3812. Establishing safe feeding sites has been promoted as a strategy to conserve wild vultures following the population crash in South Asia due to the contamination of natural food by veterinary diclofenac. Several feeding sites have been established in the region, including Nepal and it is important to evaluate their effectiveness. One aspect that is not clear yet is whether such safe feeding sites change the behaviors of wild vultures in South Asia. Here, we report incidents of White-rumped Vultures Gyps bengalensis attacking live animals at the Vulture Safe Feeding Site in Ghachok village in central Nepal. Even though a carcass was available nearby to feed upon, three White-rumped Vultures attacked an adult cow and a calf at the feeding site. The vultures’ attack served as an ancillary cause of the calf’s death in this case. These two incidents of vultures’ attacking live animals at the safe feeding site may allude to changing behaviors and cast doubt on their status of being classified as an obligate scavengers. The findings suggest alteration of vulture behaviors at the safe feeding site. Further research is needed to test the hypothesis of vulture behavior change.

Was the decline of saltmarsh tabanid populations after the 2010 oil spill associated with change in the larval food web?

AbstractHorse flies of the species Tabanus nigrovittatus and Tabanus acutus are native to coastal marshlands. Their larvae are apex invertebrate predators, and their development is dependent on the food web in the marsh sediment. Surveillance of T. nigrovittatus after the 2010 Deepwater Horizon Oil Spill in the Gulf of Mexico showed population crashes of adult flies in southeast Louisiana marshes near oil landfall, but not in southwest Louisiana where oil did not reach. Sediment collection in 2011 from Louisiana marshes showed a near‐complete absence of larvae in the southeast yet high numbers in the southwest. We hypothesized that oil contamination destroyed critical components of the larval food web and/or residual toxicity led to larval death. We used 18S rRNA gene metagenomics to identify components of the food web in larval guts and sediment from southeast and southwest Louisiana marshes. Sediment oil contamination, biochemistry, and toxicity could not explain the lack of larvae in the southeast, because oiling at our high‐tide mark sites was low at the time of the study and toxicity was independent of sediment biochemistry. Hexapods were the main food web components in tabanid larval guts. Abundance of stink bug, vinegar fly, and mosquito species in the sediment was positively associated with the presence of larvae. However, these taxa were enriched in southeastern (near oil) versus southwestern (unoiled reference) sediment, and thus, lack of major food web components due to oiling could not explain lack of larva in the east. We conclude that the immediate crash in adult populations in oiled regions was the main cause for the absence of larvae the following year. While most saltmarsh arthropod groups had rebounded within a year after the oil spill, recovery of saltmarsh horse flies was ongoing for 5 years.

Whole genome resequencing reveals signatures of rapid selection in a virus-affected commercial fishery.

Infectious diseases are recognized as one of the greatest global threats to biodiversity and ecosystem functioning. Consequently, there is a growing urgency to understand the speed at which adaptive phenotypes can evolve and spread in natural populations to inform future management. Here we provide evidence of rapid genomic changes in wild Australian blacklip abalone (Haliotis rubra) following a major population crash associated with an infectious disease. Genome scans on H. rubra were performed using pooled whole genome resequencing data from commercial fishing stocks varying in historical exposure to haliotid herpesvirus‐1 (HaHV‐1). Approximately 25,000 single nucleotide polymorphism loci associated with virus exposure were identified, many of which mapped to genes known to contribute to HaHV‐1 immunity in the New Zealand pāua (Haliotis iris) and herpesvirus response pathways in haliotids and other animal systems. These findings indicate genetic changes across a single generation in H. rubra fishing stocks decimated by HaHV‐1, with stock recovery potentially determined by rapid evolutionary changes leading to virus resistance. This is a novel example of apparently rapid adaptation in natural populations of a nonmodel marine organism, highlighting the pace at which selection can potentially act to counter disease in wildlife communities.

Weather and butterfly responses: a framework for understanding population dynamics in terms of species' life-cycles and extreme climatic events.

Understanding population responses to environmental conditions is key in the current context of climate change and the extreme climatic events that are threatening biodiversity in an unprecedented way. In this work, we provide a framework for understanding butterfly population responses to weather and extreme climatic seasons by taking into account topographic heterogeneity, species' life-cycles and density-dependent processes. We used a citizen-science database of Mediterranean butterflies that contains long-term population data (28years) on 78 butterfly species from 146 sites in the Mediterranean mesic and alpine climate regions. Climatic data were obtained from 93 meteorological stations operating during this period near the butterfly sites. We studied how seasonal precipitation and temperature affect population growth while taking into account the effects of density dependence. Our results reveal (i) the beneficial effects of winter and spring precipitation for butterfly populations, which are most evident in the Mediterranean region and in univoltine species, and mainly affect the larval stage; (ii) a general negative effect of summer rain in the previous year, which affects the adult stage; and (iii) a consistent negative effect of mild autumns and winters on population growth. In addition, density dependence played a major role in the population dynamics of most species, except for those with long-term negative population trends. Our analyses also provide compelling evidence that both extreme population levels in previous years and extreme climatic seasons in the current year provoke population crashes and explosions, especially in the Mediterranean mesic region.

A Draft Reference Genome Assembly of the Critically Endangered Black Abalone, Haliotis cracherodii.

The once abundant black abalone, Haliotis cracherodii, is a large, long-lived grazing marine mollusk that inhabits the rocky intertidal along the coast of California. The species has experienced dramatic declines since the mid-1980s largely due to the fatal bacterial disease called withering syndrome, leading to the collapse of an economically important fishery and to its inclusion into the IUCN listing as a critically endangered species. In some places impacted by the disease, populations of black abalone have declined by more than 90%, prompting population crashes associated with very little recruitment of new individuals and changes to intertidal communities. Habitats that were dominated by crustose coralline algae and bare rock have become dominated instead by fleshy algae and sessile invertebrates. Here, we present the first high-quality black abalone reference genome, assembled with PacBio HiFi long-reads and assembled with Dovetail Omni-C data to generate a scaffold-level assembly. The black abalone reference genome will be an essential resource in understanding the evolutionary history of this species as well as for exploring its current levels of genetic diversity and establishing future management and restoration plans.

Variation in Survival and Gut Microbiome Composition of Hatchery-Grown Native Oysters at Various Locations within the Puget Sound.

ABSTRACTThe Olympia oyster (Ostrea lurida) of the Puget Sound suffered a dramatic population crash, but restoration efforts hope to revive this native species. One overlooked variable in the process of assessing ecosystem health is association of bacteria with marine organisms and the environments they occupy. Oyster microbiomes are known to differ significantly between species, tissue type, and the habitat in which they are found. The goals of this study were to determine the impact of field site and habitat on the oyster microbiome and to identify core oyster-associated bacteria in the Puget Sound. Olympia oysters from one parental family were deployed at four sites in the Puget Sound both inside and outside of eelgrass (Zostera marina) beds. Using 16S rRNA gene amplicon sequencing of the oyster gut, shell, and surrounding seawater and sediment, we demonstrate that gut-associated bacteria are distinct from the surrounding environment and vary by field site. Furthermore, regional differences in the gut microbiota are associated with the survival rates of oysters at each site after 2 months of field exposure. However, habitat type had no influence on microbiome diversity. Further work is needed to identify the specific bacterial dynamics that are associated with oyster physiology and survival rates.IMPORTANCE This is the first exploration of the microbial colonizers of the Olympia oyster, a native oyster species to the West Coast, which is a focus of restoration efforts. The patterns of differential microbial colonization by location reveal microscale characteristics of potential restoration sites which are not typically considered. These microbial dynamics can provide a more holistic perspective on the factors that may influence oyster performance.

Genomic evaluation of hybridization in historic and modern North American Bison (Bison bison)

During the late nineteenth century North American bison underwent a significant population bottleneck resulting in a reduction in population size of over 99% and a species-level near-extinction event. Factors responsible for this destruction included indiscriminate killing, loss of access to suitable habitat, and diseases. At the nadir of this population crash, very few wild plains bison survived and were restricted to Yellowstone National Park, USA and a small number of wild wood bison remained in Wood Buffalo National Park, Canada. However, most surviving bison in the late 1800’s were maintained by cattle ranchers in private herds where hybridization between bison with various breeds of domestic cattle was often encouraged. Over the last 20 years, the legacy of this introgression has been identified using mitochondrial DNA and limited nuclear microsatellite analyses. However, no genome-wide assessment has been performed, and some herds were believed to be free of introgression based on current genetic testing strategies. Herein, we report detailed analyses using whole genome sequencing from nineteen modern and six historical bison, chosen to represent the major lineages of bison, to identify and quantitate signatures of nuclear introgression in their recent (within 200 years) history. Both low and high coverage genomes provided evidence for recent introgression, including animals from Yellowstone, Wind Cave, and Elk Island National Parks which were previously thought to be free from hybridization with domestic cattle. We employed multiple approaches, including one developed for this work, to identify putative cattle haplotypes in each bison genome. These regions vary greatly in size and frequency by sample and herd, though we detected domestic cattle introgression in all bison genomes tested. Since our sampling strategy spanned across the diversity of modern bison populations, these finding are best explained by multiple historical hybridization events between these two species with significant genetic recombination over the last 200 years. Our results demonstrate that whole genome sequencing approaches are required to accurately quantitate cattle introgression in bison.

Ecosystem Services and Land Rental Markets: Producer Costs of Bat Population Crashes

Nonmarket natural capital provides crucial inputs across the economy. We use land rental market data to calculate the welfare impacts of a change in an unpriced natural capital while accounting for spatial spillovers. We apply the welfare analysis to examine the cost of white-nose syndrome (WNS) in bats, which provide pest control services to agricultural producers. WNS, a disease that decimates bat populations, arrived in the United States in the mid-2000s. Leveraging the exogenous change in bat populations, we find that the loss of bats in a county causes land rental rates to fall by $2.84 per acre plus $1.50 per acre per neighboring county with WNS. Agricultural land falls by 1,102 acres plus 582 acres per neighboring county with WNS. As of 2017, agricultural losses from WNS were between $426 and $495 million per year. These estimates of ecosystem service values can inform public management of society’s natural capital.

Irruptive dynamics of invasive carnivores and prey populations, and predator control, affect kea survivorship across the Southern Alps

ABSTRACT Invasive carnivores are threatening the indigenous fauna of Aotearoa, but impacts vary with time, space and species. Conservation strategies require knowledge of predator-prey dynamics specific to different ecosystems and allowing for long-term guild shifts. To build this knowledge, we model the survivorship of the kea, a long-lived, ground-nesting parrot with an expansive species-range, using a dataset spanning two decades (1998–2021) and spanning several forest-dominated South Island montane ecosystems. Kea survivorship was lower in eastern ecosystems compared to western ones, depressed during carnivore irruptions, and elevated after predator control. Kea of all ages and both sexes fell prey to stoats and feral cats whilst foraging and roosting, not whilst nesting. Stoat depredation happened in all ecosystems, whereas feral cats featured more in eastern ones. Annual survivorship was high in most contexts (adults > 90%, juveniles > 70%), but a peak in stoat and feral cat predation in eastern ecosystems during 2020–2021 reduced adult survival to <60%. This predation peak followed a rodent population crash, the primary prey of carnivores in eastern beech forests. We conclude that predator impacts on kea are concentrated into post-mast years. Recommendations for management are provided.

Early instar mortality of a forest pest caterpillar: which mortality sources increase during an outbreak crash?

AbstractCollapses of insect pest outbreaks are often attributed to delayed density dependence of predation. The forest tent caterpillar, Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae), is an outbreaking pest species defoliating mixed wood boreal forests in eastern Canada. This species presents periodic population dynamics with peaks every 10 years and outbreaks lasting 1–3 years impacting the health of its host tree. We asked about the relative importance of various sources of early‐instar mortality during and after the crash of an outbreak, testing for density dependence. We used a triad set‐up of complete predator exclusion, partial exclusion, and free colonies to distinguish between intrinsic mortality (caused by, e.g., pathogens) and mortality caused by flighted and walking natural enemies, and compared defoliated outbreak sites with control sites. Overall, survival was lowest in the free colonies and increased with partial and complete predator exclusion. Survival was also higher in control than in outbreak sites and higher in the final year of the outbreak than in the following year. We observed no changes in mortality from walking enemies, but an increase in intrinsic mortality and mortality from flighted enemies. in the year following the outbreak. This increase is consistent with density dependence of these mortality sources, but its occurrence in the control sites as well was unexpected. These findings show that mortality from flighted natural enemies and intrinsic source increases after the outbreak, but do not contribute to the population crash. However, they help maintain low endemic levels between outbreaks.

Demographic decline and lineage-specific adaptations characterize New Zealand kiwi.

Small and fragmented populations may become rapidly differentiated due to genetic drift, making it difficult to distinguish whether neutral genetic structure is a signature of recent demographic events, or of long-term evolutionary processes that could have allowed populations to adaptively diverge. We sequenced 52 whole genomes to examine Holocene demographic history and patterns of adaptation in kiwi (Apteryx), and recovered 11 strongly differentiated genetic clusters corresponding to previously recognized lineages. Demographic models suggest that all 11 lineages experienced dramatic population crashes relative to early- or mid-Holocene levels. Small population size is associated with low genetic diversity and elevated genetic differentiation (FST), suggesting that population declines have strengthened genetic structure and led to the loss of genetic diversity. However, population size is not correlated with inbreeding rates. Eight lineages show signatures of lineage-specific selective sweeps (284 sweeps total) that are unlikely to have been caused by demographic stochasticity. Overall, these results suggest that despite strong genetic drift associated with recent bottlenecks, most kiwi lineages possess unique adaptations and should be recognized as separate adaptive units in conservation contexts. Our work highlights how whole-genome datasets can address longstanding uncertainty about the evolutionary and conservation significance of small and fragmented populations of threatened species.

Gene drive that results in addiction to a temperature-sensitive version of an essential gene triggers population collapse in Drosophila

One strategy for population suppression seeks to use gene drive to spread genes that confer conditional lethality or sterility, providing a way of combining population modification with suppression. Stimuli of potential interest could be introduced by humans, such as an otherwise benign virus or chemical, or occur naturally on a seasonal basis, such as a change in temperature. Cleave and Rescue (ClvR) selfish genetic elements use Cas9 and guide RNAs (gRNAs) to disrupt endogenous versions of an essential gene while also including a Rescue version of the essential gene resistant to disruption. ClvR spreads by creating loss-of-function alleles of the essential gene that select against those lacking it, resulting in populations in which the Rescue provides the only source of essential gene function. As a consequence, if function of the Rescue, a kind of Trojan horse now omnipresent in a population, is condition dependent, so too will be the survival of that population. To test this idea, we created a ClvR in Drosophila in which Rescue activity of an essential gene, dribble, requires splicing of a temperature-sensitive intein (TS-ClvRdbe). This element spreads to transgene fixation at 23 °C, but when populations now dependent on Ts-ClvRdbe are shifted to 29 °C, death and sterility result in a rapid population crash. These results show that conditional population elimination can be achieved. A similar logic, in which Rescue activity is conditional, could also be used in homing-based drive and to bring about suppression and/or killing of specific individuals in response to other stimuli.