On Reviving Extinct Predator Species

Ecological networks are tightly interconnected, such that loss of a single species can trigger additional species extinctions. Theory predicts that such secondary extinctions are driven primarily by loss of species from intermediate or basal trophic levels. In contrast, most cases of secondary extinctions from natural systems have been attributed to loss of entire top trophic levels. Here, we show that loss of single predator species in isolation can, irrespective of their identity or the presence of other predators, trigger rapid secondary extinction cascades in natural communities far exceeding those generally predicted by theory. In contrast, we did not find any secondary extinctions caused by intermediate consumer loss. A food web model of our experimental system-a marine rocky shore community-could reproduce these results only when biologically likely and plausible nontrophic interactions, based on competition for space and predator-avoidance behaviour, were included. These findings call for a reassessment of the scale and nature of extinction cascades, particularly the inclusion of nontrophic interactions, in forecasts of the future of biodiversity.

Borhyaenoids were marsupial predators that inhabited South America during the Cenozoic. They were very significant because no other mammals rivaled them as terrestrial hunters of large prey. Here we estimate the bite force of three species of borhyaenoids by two different methods to infer predatory behaviour in extinct taxa. One of the methods uses mainly the skull and only some simple measurements of the mandible; the other uses several measurements within the dentary. The results show that bite forces are very high in comparison to predators of the order Carnivora, a feature manifest by several other living and extinct marsupial predators. Differences in size, bite mechanics and special adaptations among the borhyaenoids suggest a very wide range of predatory behaviours that rival those represented in the extant families of the Order Carnivora.

Aim Resolving the spatio‐temporal diversification patterns and systematic relationships of endemic Australian land snails against the backdrop of Neogene aridification through analyses of a combined nuclear and mitochondrial DNA sequence dataset. Location Western Australia. Taxon Mollusca, Stylommatophora, Bothriembryontidae, Bothriembryon. Methods We employed Bayesian Inference and Maximum Likelihood to reconstruct the phylogenetic relationships in a group of Australian land snails using mitochondrial (COI, 16S) and nuclear (ANT) DNA sequences. Divergence times have been estimated by employing optimised molecular clocks using BEAST2, and RelTime in MEGA12. Speciation and net‐diversification rates have been modelled using revBayes to visualise diversification dynamics in lineage‐through‐time (LTT) plots. We employed automated species delimitation methods ASAP and bPTP to estimate taxonomic diversity. Results Our final sequence dataset contained 1052 new DNA sequences from 374 individuals, representing 97% of all accepted species plus 26 putatively new species based on morphology and distribution. Recognizing almost three times as many candidate species, both DNA‐based species delimitation methods have excessively inflated diversity estimates, casting doubt on the usefulness of these methods in groups with marked phylogeographic structure. Nine well‐supported principal clades were recovered. Fossil‐calibrated chronograms revealed an early bifurcation of Bothriembryon followed by an accumulation of lineages over time. LTT plots revealed a relative flattening of the speciation curve from 15 to 10 Ma on. However, we also detected a steep increase in intraspecific lineage diversification during the last approx. 1 Ma. The modeled speciation and net diversification rates have continuously declined over the last 25 Ma, while extinction rates have remained relatively steady until about 5 Ma, when they also started to climb. Main Conclusions Declining diversification rates during much of the Neogene, followed by increasing extinction rates, coincided with increasing aridity throughout Western Australia. A more recent increase in lineage diversification rates, driven by intraspecific differentiation, coincides with the rise of mesic conditions since the end of the Pleistocene. Both trends imply that through influencing extinction and diversification rates, historical climate change has likely contributed to shaping the current distribution patterns in Bothriembryon land snails that are characterised by fragmentation. Moreover, by uncovering many undescribed taxa, including multiple short‐range endemics, this study highlights the importance of continued conservation efforts in this globally important biodiversity hotspot. Key habitats, such as lithorefugia, in an otherwise harsh and exposed landscape are important strongholds for Bothriembryon to weather the impact of aridification.

The evolutionary patterns of animal species clades in an evolving food web system were examined by computer simulation. In this system, each animal species fed on other species according to feeding preference. The food web system evolved via the appearance and extinction of species. The model succeeded in reproducing evolutionary patterns of diversity similar to those seen in the fossil record. This result indicates that the model reproduced the temporal changes of the rates of colonization and extinction of species in the system, which have been decided a priori in the previous stochastic models. In the food web system, the numbers of both predatory and prey species influenced the temporal diversity patterns in each clade in the system. The number of prey species fluctuated strongly, whereas the number of predatory species gradually increased with time. Therefore, temporal diversity patterns were influenced mainly by the number of predatory species. As a result of the gradual increase of the number of predatory species, it was difficult for each clade to maintain its species diversity for a long time. Slight changes of interspecific interaction can sometimes decide the destiny of a clade. When a clade is faced with extinction, if one predatory species of the clade becomes extinct and one or two prey species of the clade appear, the species diversity in the clade increases again. This result indicates that slight changes of interspecific interaction sometimes decide the destiny of a clade.

Changes in biodiversity will mediate the consequences of agricultural intensification and expansion for ecosystem services. Regulating services, like pollination and pest control, generally decline with species loss. In nature, however, relationships between service provision and species richness are not always strong, partially because anthropogenic disturbances purge species from communities in nonrandom orders. The same traits that make for effective service providers may also confer resistance or sensitivity to anthropogenic disturbances, which may either temper or accelerate declines in service provision with species loss. We modeled a community of predators interacting with insect pest prey, and identified the contexts in which pest control provision was most sensitive to species loss. We found pest populations increased rapidly when functionally unique and dietary-generalist predators were lost first, with up to 20% lower pest control provision than random loss. In general, pest abundance increased most in the scenarios that freed more pest species from predation. Species loss also decreased the likelihood that the most effective service providers were present. In communities composed of species with identical traits, predators were equally effective service providers and, when competing predators went extinct, remaining community members assumed their functional roles. In more realistic trait-diverse communities, predators differed in pest control efficacy, and remaining predators could not fully compensate for the loss of their competitors, causing steeper declines in pest control provision with predator species loss. These results highlight diet breadth in particular as a key predictor of service provision, as it affects both the way species respond to and alter their environments. More generally, our model provides testable hypotheses for predicting how nonrandom species loss alters relationships between biodiversity and pest control provision.

1. Global declines in biodiversity have stimulated much research into the consequences of species loss for ecosystems and the goods and services they provide. Species at higher trophic levels are at greater risk of human-induced extinction yet remarkably little is known about the effects of consumer species loss across multiple trophic levels in natural complex ecosystems. Previous studies have been criticized for lacking experimental realism and appropriate temporal scale, running for short periods that are not sufficient to detect many of the mechanisms operating in the field. 2. We manipulated the presence of two predator species and two groups of their prey (primary consumers) and measured their independent and interactive effects on primary producers in a natural marine benthic system. The presence of predators and their prey was manipulated in the field for 14months to distinguish clearly the direct and indirect effects of predators on primary producers and to identify mechanisms driving responses. 3. We found that the loss of either predator species had indirect negative effects on species diversity and total cover of primary producers. These cascading effects of predator species loss were mediated by the presence of intermediate consumers. Moreover, the presence of different intermediate consumers, irrespective of the presence or absence of their predators, determined primary producer assemblage structure. We identified direct negative effects of predators on their prey and several indirect effects of predators on primary producers but not all interactions could have been predicted based on trophic level. 4. Our findings demonstrate the importance of trophic cascade effects coupled with non-trophic interactions when predicting the effects of loss of predator species on primary producers and consequently for ecosystem functioning. There is a pressing need for improved understanding of the effects of loss of consumers, based on realistic scenarios of diversity loss, to test conceptual frameworks linking predator diversity to variation in ecosystem functioning and for the protection of biodiversity, ecosystem functioning and related services.

Summary A key rationale for pursuing de‐extinction is the potential to restore lost processes and function to modern ecosystems. However, understanding and providing for the ecological requirements of the candidate species will also play a key role in determining the ultimate success of a de‐extinction. This assessment is challenging for prehistoric extinct species, where empirical studies or observations on their ecology are not available or are incomplete. A healthy, stable and self‐sustaining population of a resurrected species needs to be embedded in an ecological interaction network that consists not only of interactions between a resurrected species and its external environment (e.g. habitat, diet), but also those where the resurrected species is the environment (e.g. microbiota and parasites). Palaeoecology can provide information on all of these interactions for extinct species, and this information can help guide and inform the selection of suitable de‐extinction candidates or traits for resurrection. Ecological interaction network analyses offer a complementary tool to existing frameworks for determining the suitability of de‐extinction candidates, allowing palaeoecological information to be used to identify and quantify the potential implications of removing or adding resurrected species/functions to an ecosystem. Although palaeoecological data and understanding clearly have an important role in informing and modelling the potential ecological functions provided by extinct species, they can only ever provide an incomplete picture and therefore would only complement, rather than replace, observational or experimental data on the resurrected organisms themselves. A lay summary is available for this article.

We study a differential equation system with diffusion and time delays which models the dynamics of predator-prey interactions within three biological species. Our main focus is on the persistence (non-extinction) of u-species which is at the bottom of the nutrient hierarchy, and the permanence effect (long-term survival of all the predators and prey) in this model. When u-species persists in the absence of its predators, we generate a condition on the interaction rates to ensure that it does not go extinction under the predation of the v- and w-species. With certain additional conditions, we can further obtain the permanence effect (long-term survival of all three species) in the ecological system. Our proven results also explicitly present the effects of all the environmental data (growth rates and interaction rates) on the ultimate bounds of the three biological species. Numerical simulations of the model are also given to demonstrate the pattern of dynamics (extinction, persistence, and permanence)in the ecological model.

For almost 100 years, biologists have made fundamental discoveries using a handful of model organisms that are not representative of the rich diversity found in nature. The advent of CRISPR genome editing now opens up a wide range of new organisms to mechanistic investigation. This increases not only the taxonomic breadth of current research but also the scope of biological problems that are now amenable to study, such as population control of invasive species, management of disease vectors such as mosquitoes, the creation of chimeric animal hosts to grow human organs and even the possibility of resurrecting extinct species such as passenger pigeons and mammoths. Beyond these practical applications, work on non-model organisms enriches our basic understanding of the natural world. This special issue addresses a broad spectrum of biological problems in non-model organisms and highlights the utility of genome editing across levels of complexity from development and physiology to behaviour and evolution.

Though the maximum sustainable yield (MSY) approach has been legally adopted for the management of world fisheries, it does not provide any guarantee against from species extinction in multispecies communities. In the present article, we describe the appropriateness of the MSY policy in a Holling-Tanner prey-predator system with different types of functional responses. It is observed that for both type I and type II functional responses, harvesting of either prey or predator species at the MSY level is a sustainable fishing policy. In the case of combined harvesting, both the species coexist at the maximum sustainable total yield (MSTY) level if the biotic potential of the prey species is greater than a threshold value. Further, increase of the biotic potential beyond the threshold value affects the persistence of the system.

Island Mammal Extinctions are Determined by Interactive Effects of Life History, Island Biogeography, Mesopredator Suppression

Traditionally, community models have focused on density-dependent factors. More recently, though, studies that consider populations interacting on a spatial (as well as temporal) scale have become very popular. These metacommunity models often use the patch-occupancy approach, where the focus is on regional dynamics (patches are classied as simply occupied or vacant). A few studies have extended this work by modelling local dynamics explicitly, although the food webs involved have been relatively simple. This paper takes the next step and considers a spatially explicit habitat where species interact across three trophic levels. The aim is to investigate how web connectance, patch abundance and dispersal patterns aect a community's ability to recover from the loss of a species. I nd that asynchrony among patch dynamics may arise from relatively low rates of migration, and that the inclusion of space signicantly reduces the risk of cascading extinctions. It is shown that communities with sparsely connected food webs are the most sensitive to perturbations, but also that they are particularly well stabilised by the introduction of space. In agreement with theoretical studies of non-spatial habitats, species holding the highest trophic rank are the most susceptible to secondary extinctions, although they often take the longest to die out. This is particularly pronounced in spatial habitats, where the top predator appears to be the least well adapted to exploit the stabilising properties of space. Results such as these are discussed in detail, and their implications are set in the context of habitat management.

th May. Abstract. Here, we update the current list of amphibian and reptile fauna present in the Balearic Islands, probably the most outstanding case in the Mediterranean and of the most in the world where massive species introduction is in conflict with the survi- vorship of highly restricted endemic taxa. Resulting of a long term evolution in insu- larity, endemic herpetofauna was already decimated during the Pleistocene but, after the human colonisation of the archipelago, the introduction of alien species, passive or deliberate, has been provoking new extinctions and range retractions in the native her - petofauna. Such process is not interrupted but has even intensified during the last years. The current species list is composed by five amphibians (one native) and 21 reptiles (2 native). A critical review of the evidence on extinctions and introductions is provided together with the conservation implications. Compared to the last review (Mayol, 1985) six new reptile species are now naturalised or are in process of naturalization, colubrid snakes constituting the most conflicting element due to their predator role.

There is evidence of plankton mortality and extinction at various temporal and spatial scales induced by man-made pollution, or by natural causes (ageing, competition, predation, diseases, natural pollution). If mortalities take place at large scale they might become of environmental concern and may impact other biotic compartments including fisheries substantially. Such mortalities are a consistent phenomenon at time scales from geological mass extinctions to regularly occurring HABs, that appear to be increasing on a global basis. Several mass mortalities might have escaped our notice for their patchy and erratic occurrences. This also holds for mortalities caused by hydrothermal vents (HVs) that cover possibly more than 1.5% of the ocean floor. We studied zooplankton diversity, abundance and distribution patterns above shallow water hydrothermal vents at Kueishan Tao (Turtle Island), off the northeast coast of Taiwan (West Pacific). The HVs at this side provide an opportunity for the study of mortality, community and population effects of HV effluents with ecophysiological investigations that are otherwise difficult to perform at the more common HV environment, the deep sea. We found evidence for a bottle-neck situation for plankton above vent sites since holoplankton was generally deadly affected when immersed directly in vent plumes. Here we used copepods from HV sites for ecotoxicological testing in mesocosm field experiments.

Cretaceous-Tertiary (KT) sequences in Nuevo Leon and Tamaulipas, Mexico, contain trace fossils that shed important light on the nature and duration of deposition of the KT boundary strata in that region. The KT clastic sequence in northeastern Mexico typically is divided into three distinct sedimentary units which represent distinctly different depositional events. Unit I is an unbioturbated, laminated deposit of alternating smectite grains and calcite spherules. Unit II is a sandstone that is mostly unbioturbated, but a few spherule-filled burrows occur near the base of the unit. Several burrows were truncated by overlying sand layers within Unit II, indicating that they were excavated following deposition of the first sand layers and then filled with spherules, scoured, and overlain by more Unit II sand. Unit III consists of alternating sandstone, siltstone, and shale that contain abundant trace fossils, including Chondrites, Ophiomorpha, Planolites, and Zoophycos. The nature of the trace fossil occurrences attest to at least three successive colonization episodes of the accreting substrate. The sandstone beds of Unit III were deposited episodically, and burrowing occurred during the period of deposition, not after deposition had ceased. The burrows were filled with late Cretaceous sediment. Trace fossil evidence indicates, therefore, that the entire KT clastic sequence must have been deposited over a long period of time. If the spherules in Unit I are material derived from an extraterrestrial impact, that impact must have predated the extinction of Cretaceous plankton by a significant time interval, which is represented by the periods of deposition of Units II and III. The ichnologic information indicates episodic deposition of Units II and III over an extended time period. Thus, the event that produced the calcite spherules in Unit I is not directly related to the Cretaceous plankton extinctions at the KT boundary, which occur at the top of Unit III.