Invader or resident? Ancient-DNA reveals rapid species turnover in New Zealand little penguins

The expansion of humans into previously unoccupied parts of the globe is thought to have driven the decline and extinction of numerous vertebrate species. In New Zealand, human settlement in the late thirteenth century AD led to the rapid demise of a distinctive vertebrate fauna, and also a number of ''turnover'' events where extinct lineages were subsequently replaced by closely related taxa. The recent genetic detection of an Australian little penguin (Eudyptula novaehollandiae) in southeastern New Zealand may potentially represent an additional ‘cryptic’ invasion. Here we use ancient-DNA (aDNA) analysis and radiocarbon dating of pre-human, archaeological and historical Eudyptula remains to reveal that the arrival of E. novaehollandiae in New Zealand probably occurred between AD 1500 and 1900, following the anthropogenic decline of its sister taxon, the endemic Eudyptula minor. This rapid turnover event, revealed by aDNA, suggests that native species decline can be masked by invasive taxa, and highlights the potential for human-mediated biodiversity shifts.     

Tree species richness decreases while species evenness increases with disturbance frequency in a natural boreal forest landscape

Understanding species diversity and disturbance relationships is important for biodiversity conservation in disturbance‐driven boreal forests. Species richness and evenness may respond differently with stand development following fire. Furthermore, few studies have simultaneously accounted for the influences of climate and local site conditions on species diversity. Using forest inventory data, we examined the relationships between species richness, Shannon''s index, evenness, and time since last stand‐replacing fire (TSF) in a large landscape of disturbance‐driven boreal forest. TSF has negative effect on species richness and Shannon''s index, and a positive effect on species evenness. Path analysis revealed that the environmental variables affect richness and Shannon''s index only through their effects on TSF while affecting evenness directly as well as through their effects on TSF. Synthesis and applications. Our results demonstrate that species richness and Shannon''s index decrease while species evenness increases with TSF in a boreal forest landscape. Furthermore, we show that disturbance frequency, local site conditions, and climate simultaneously influence tree species diversity through complex direct and indirect effects in the studied boreal forest.     

Clarifying Baker's Law

Background

Baker''s Law states that colonization by self-compatible organisms is more likely to be successful than colonization by self-incompatible organisms because of the ability for self-compatible organisms to produce offspring without pollination agents. This simple model has proved very successful in plant ecology and has been applied to various contexts, including colonizing or ruderal species, islands colonizers, invasive species or mating system variation across distribution ranges. Moreover, it is one of the only models in population biology linking two traits of major importance in ecology, namely dispersal and mating system. Although Baker''s Law has stimulated a large number of empirical studies reporting the association of self-fertilization and colonizing ability in various contexts, the data have not established a general pattern for the association of traits.

Scope

In this paper, a critical position is adopted to discuss and clarify Baker''s Law. From the literature referring to Baker''s Law, an analysis made regarding how mating success is considered in such studies and discrepancies with population genetics theory of mating systems are highlighted. The data reporting the association of self-fertilization and colonizing ability are also briefly reviewed and the potential bias in interpretation is discussed. Lastly, a recent theoretical model analysing the link between colonizing ability and self-fertilization is considered.

Conclusions

Evolutionary predictions are actually more complex than Baker''s intuitive arguments. It appears that Baker''s Law encompasses a variety of ecological scenarios, which cannot be considered a priori as equivalent. Questioning what has been considered as self-evident for more than 50 years seems a reasonable objective to analyse in-depth dispersal and mating system traits.     

A novel hearing specialization in the New Zealand bigeye,Pempheris adspersa

The New Zealand bigeye, Pempheris adspersa, is a nocturnal planktivore and has recently been found to be an active sound producer. The rostral end of the swim bladder lies adjacent to Baudelot''s ligament which spans between the bulla and the cleithrum bone of the pectoral girdle. The aim of this study was to use the auditory evoked potential technique to physiologically test the possibility that this structure provides an enhanced sensitivity to sound pressure in the bigeye. At 100 Hz, bigeye had hearing sensitivity similar to that of goldfish (species with a mechanical connection between the swim bladder and the inner ear mediated by the Weberian ossicles) and were much more sensitive than other teleosts without ancillary hearing structures. Severing Baudelot''s ligament bilaterally resulted in a marked decrease in hearing sensitivity, as did swim bladder puncture or lateral line blockage. These results show that bigeye have an enhanced sensitivity to sound pressure and provide experimental evidence that the functional basis of this sensitivity represents a novel hearing specialization in fish involving the swim bladder, Baudelot''s ligament and the lateral line.     

Shift in precipitation regime promotes interspecific hybridization of introduced Coffea species

The frequency of plant species introductions has increased in a highly connected world, modifying species distribution patterns to include areas outside their natural ranges. These introductions provide the opportunity to gain new insight into the importance of flowering phenology as a component of adaptation to a new environment. Three Coffea species, C. arabica, C. canephora (Robusta), and C. liberica, native to intertropical Africa have been introduced to New Caledonia. On this archipelago, a secondary contact zone has been characterized where these species coexist, persist, and hybridize spontaneously. We investigated the impact of environmental changes undergone by each species following its introduction in New Caledonia on flowering phenology and overcoming reproductive barriers between sister species. We developed species distribution models and compared both environmental envelopes and climatic niches between native and introduced hybrid zones. Flowering phenology was monitored in a population in the hybrid zone along with temperature and precipitation sequences recorded at a nearby weather station. The extent and nature of hybridization events were characterized using chloroplast and nuclear microsatellite markers. The three Coffea species encountered weak environmental suitability compared to their native ranges when introduced to New Caledonia, especially C. arabica and C. canephora. The niche of the New Caledonia hybrid zone was significantly different from all three species' native niches based on identity tests (I Similarity and D Schoener's Similarity Indexes). This area appeared to exhibit intermediate conditions between the native conditions of the three species for temperature‐related variables and divergent conditions for precipitation‐related ones. Flowering pattern in these Coffea species was shown to have a strong genetic component that determined the time between the triggering rain and anthesis (flower opening), specific to each species. However, a precipitation regime different from those in Africa was directly involved in generating partial flowering overlap between species and thus in allowing hybridization and interspecific gene flow. Interspecific hybrids accounted for 4% of the mature individuals in the sympatric population and occurred between each pair of species with various level of introgression. Adaptation to new environmental conditions following introduction of Coffea species to New Caledonia has resulted in a secondary contact between three related species, which would not have happened in their native ranges, leading to hybridization and gene flow.     

Reconstructing demographic events from population genetic data: the introduction of bumblebees to New Zealand

Four British bumblebee species (Bombus terrestris, Bombus hortorum, Bombus ruderatus and Bombus subterraneus) became established in New Zealand following their introduction at the turn of the last century. Of these, two remain common in the United Kingdom (B. terrestris and B. hortorum), whilst two (B. ruderatus and B. subterraneus) have undergone marked declines, the latter being declared extinct in 2000. The presence of these bumblebees in New Zealand provides an unique system in which four related species have been isolated from their source population for over 100 years, providing a rare opportunity to examine the impacts of an initial bottleneck and introduction to a novel environment on their population genetics. We used microsatellite markers to compare modern populations of B. terrestris, B. hortorum and B. ruderatus in the United Kingdom and New Zealand and to compare museum specimens of British B. subterraneus with the current New Zealand population. We used approximate Bayesian computation to estimate demographic parameters of the introduction history, notably to estimate the number of founders involved in the initial introduction. Species-specific patterns derived from genetic analysis were consistent with the predictions based on the presumed history of these populations; demographic events have left a marked genetic signature on all four species. Approximate Bayesian analyses suggest that the New Zealand population of B. subterraneus may have been founded by as few as two individuals, giving rise to low genetic diversity and marked genetic divergence from the (now extinct) UK population.     

Knower–guesser differentiation in ravens: others' viewpoints matter

Differentiating between individuals with different knowledge states is an important step in child development and has been considered as a hallmark in human evolution. Recently, primates and corvids have been reported to pass knower–guesser tasks, raising the possibility of mental attribution skills in non-human animals. Yet, it has been difficult to distinguish ‘mind-reading’ from behaviour-reading alternatives, specifically the use of behavioural cues and/or the application of associatively learned rules. Here, I show that ravens (Corvus corax) observing an experimenter hiding food are capable of predicting the behaviour of bystanders that had been visible at both, none or just one of two caching events. Manipulating the competitors'' visual field independently of the view of the test-subject resulted in an instant drop in performance, whereas controls for behavioural cues had no such effect. These findings indicate that ravens not only remember whom they have seen at caching but also take into account that the other''s view was blocked. Notably, it does not suffice for the birds to associate specific competitors with specific caches. These results support the idea that certain socio-ecological conditions may select for similar cognitive abilities in distantly related species and that some birds have evolved analogous precursors to a human theory-of-mind.     

Is Rapoport's rule a recent phenomenon? A deep time perspective on potential causal mechanisms

Macroecology strives to identify ecological patterns on broad spatial and temporal scales. One such pattern, Rapoport''s rule, describes the tendency of species'' latitudinal ranges to increase with increasing latitude. Several mechanisms have been proposed to explain this rule. Some invoke climate, either through glaciation driving differential extinction of northern species or through increased seasonal variability at higher latitudes causing higher thermal tolerances and subsequently larger ranges. Alternatively, continental tapering or higher interspecific competition at lower latitudes may be responsible. Assessing the incidence of Rapoport''s rule through deep time can help to distinguish between competing explanations. Using fossil occurrence data from the Palaeobiology Database, we test these hypotheses by evaluating mammalian compliance with the rule throughout the Caenozoic of North America. Adherence to Rapoport''s rule primarily coincides with periods of intense cooling and increased seasonality, suggesting that extinctions caused by changing climate may have played an important role in erecting the latitudinal gradients in range sizes seen today.     

Spatial and temporal extinction dynamics in a freshwater cetacean

Geographical range contraction is a fundamental ecological characteristic of species population decline, but relatively little investigation has been conducted into general trends in the dynamic properties of range collapse. The Yangtze River dolphin or baiji (Lipotes vexillifer), probably the first large mammal species to have become extinct in over 50 years, was believed to have experienced major range collapse during its decline through progressive large-scale range contraction and fragmentation. This range-collapse model is challenged by a new dataset of 406 baiji last-sighting records collected from across the baiji''s historical range during an interview survey of Yangtze fishing communities. Although baiji regional abundance may have varied across its range, analyses of the extensive new sighting series provide comprehensive evidence that baiji population decline was not associated with any major contraction in geographical range across the middle–lower Yangtze drainage, even in the decade immediately before probable global extinction of the species. Extinction risk in baiji was therefore seemingly not related to evidence of range collapse. Baiji apparently underwent large-scale periodic and seasonal movements across their range, and we propose that range contraction and fragmentation may not be general biogeographic characteristics for declining populations of mobile species in connected landscapes.     

Introduction history of non-native freshwater fish in Okinawa-jima Island: ornamental aquarium fish pose the greatest risk for future invasions

We examined the introduction history of non-native freshwater fish in Okinawa-jima Island, Japan, to identify the pathway posing the greater risk for future invasions and to measure the strength of ornamental fish introductions as a vector of new invasions using all available records of freshwater fish introductions to date. At least 45 non-native freshwater fish have been introduced to Okinawa-jima Island. Of those, 22 species have successfully established in natural waters and, consequently, non-native fish species represent 76 % of the total freshwater fish fauna. The most important pathway was via the dumping of unwanted ornamental aquarium fish, which accounted for 71 % of the total introductions. The introduction of ornamental fish has occurred extensively in recent decades, and all fish introduced since the 1980s have been ornamental aquarium fish. The overall rate of establishment success was estimated at 51 %, although this is undoubtedly an overestimate because of unreported failed introductions. Establishment rates varied between stocked fish (100 %) and dumped ornamental fish (39 %), which may reflect the low propagule pressure of ornamental fish. From the observed trends in freshwater fish introductions, the dumping of ornamental fish into natural waters is expected to continue if no action is taken to reduce this most important pathway. We recommend regulations against the release of unwanted pet fish into natural waters, better programs for returning unwanted pet fish to stores or local zoos, educational programs for aquarists and retailers, and regulations against selling and trading ornamental fish that are judged to pose a high risk of causing economic or ecological harm.     

Effect of Entomopathogenic Nematode Concentration on Survival during Cryopreservation in Liquid Nitrogen

Entomopathogenic nematodes are used for biological control of insect pests. A method for improved cryopreservation of infective juvenile stage nematodes has been developed using Steinernema carpocapsae and Heterorhabditis bacteriophora. Optimum survival for both species was achieved with 12,000 infective juveniles/ml in glycerol and 7,500/ml in Ringer''s solution. For S. carpocapsae, maximum survival also was observed with 60,000 infective juveniles/ml in glycerol and 25,000/ml in Ringer''s solution. These concentrations resulted in 100% post-cryopreservation survival of S. carpocapsae and 100% retention of original virulence to Galleria mellonella larvae. This is the first report of achieving 100% survival of an entomopathogenic nematode after preservation in liquid nitrogen. Maximum survival of H. bacteriophora following cryopreservation was 87%.     

New Guinea highland origin of a widespread arthropod supertramp

The biologically and geologically extremely diverse archipelagos of Wallacea, Australasia and Oceania have long stimulated ecologists and evolutionary biologists. Yet, few molecular phylogenetic analyses of the terrestrial fauna have been carried out to understand the evolutionary patterns. We use dense taxon and character sampling of more than 7000 bp DNA sequence data for a group of diving beetles ranging from the Holarctic throughout Asia to as far east as French Polynesia. We here show that an ecologically diverse, common and widespread (Portugal to New Zealand) arthropod supertramp species originated in the highlands of New Guinea, ca 6.0–2.7 Myr ago. The approximately 25 closely related species are narrow endemics in Australasia/Oceania. The ancestor of this clade colonized that region from Eurasia ca 9–7 Myr ago. Our finding contradicts the widely held view of local endemism as an evolutionary dead end, as we find multiple peripatric speciation events within the Pleistocene and complex colonization patterns between the Oriental and Australian zoogeographic regions, including the recolonization of Eurasia, jumping across Wallace''s line and colonization of continental Australia out of New Guinea. Our study strongly highlights the importance of dispersal over water gaps in shaping biogeographic patterns.     

Grateloupia turuturu (Halymeniaceae,Rhodophyta) is the correct name of the non-native species in the Atlantic known as Grateloupia doryphora

Grateloupia doryphora (Montagne) Howe, originally described from Peru, has repeatedly been reported as an invasive species in Atlantic and Mediterranean waters. Various attempts to explain this species' route of introduction have been unsatisfactory. New evidence from comparative rbcL sequence analysis and morphology suggests that this adventive species in the NE and NW Atlantic corresponds with G. turuturu Yamada, originally described from Japan. This provenance follows a well-recognized trend of invasive marine organisms that have colonized the Atlantic Ocean and Mediterranean Sea from Pacific NE Asia.     

The role of competition and introduction effort in the success of passeriform birds introduced to New Zealand

Abstract The finding that passeriform birds introduced to the islands of Hawaii and Saint Helena were more likely to successfully invade when fewer other introduced species were present has been interpreted as strong support for the hypothesis that interspecific competition influences invasion success. I tested whether invasions were more likely to succeed when fewer species were present using the records of passeriform birds introduced to four acclimatization districts in New Zealand. I also tested whether introduction effort, measured as the number of introductions and the total number of birds released, could predict invasion outcomes, a result previously established for all birds introduced to New Zealand. I found patterns consistent with both competition and introduction effort as explanations for invasion success. However, data supporting the two explanations were confounded such that the greater success of invaders arriving when fewer other species were present could have been due to a causal relationship between invasion success and introduction effort. Hence, without data on introduction effort, previous studies may have overestimated the degree to which the number of potential competitors could independently explain invasion outcomes and may therefore have overstated the importance of competition in structuring introduced avian assemblages. Furthermore, I suggest that a second pattern in avian invasion success previously attributed to competition, the morphological overdispersion of successful invaders, could also arise as an artifact of variation in introduction effort.     

Dung beetles in an avian-dominated island ecosystem: feeding and trophic ecology

Globally, dung beetles (Scarabaeidae: Scarabaeinae) are linked to many critical ecosystem processes involving the consumption and breakdown of mammal dung. Endemic New Zealand dung beetles (Canthonini) are an anomaly, occurring at high abundance and low diversity on an island archipelago historically lacking terrestrial mammals, except bats, and instead dominated by birds. Have New Zealand’s dung beetles evolved to specialise on bird dung or carrion, or have they become broad generalist feeders? We test dietary preferences by analysing nitrogen isotope ratios of wild dung beetles and by performing feeding behaviour observations of captive specimens. We also use nitrogen and carbon stable isotopes to determine if the dung beetle Saphobius edwardsi will consume marine-derived carrion. Nitrogen isotope ratios indicated trophic generalism in Saphobius dung beetles and this was supported by behavioural observations where a broad range of food resources were utilised. Alternative food resource use was further illustrated experimentally by nitrogen and carbon stable isotope signatures of S. edwardsi, where individuals provided with decomposed squid had δ¹⁵N and δ¹³C values that had shifted toward values associated with marine diet. Our findings suggest that, in the absence of native mammal dung resources, New Zealand dung beetles have evolved a generalist diet of dung and carrion. This may include marine-derived resources, as provided by the seabird colonies present in New Zealand forests before the arrival of humans. This has probably enabled New Zealand dung beetles to persist in indigenous ecosystems despite the decline of native birds and the introduction of many mammal species.     

Norway rats reciprocate help according to the quality of help they received

Direct reciprocity, according to the decision rule ‘help someone who has helped you before’, reflects cooperation based on the principle of postponed benefits. A predominant factor influencing Homo sapiens'' motivation to reciprocate is an individ­ual''s perceived benefit resulting from the value of received help. But hitherto it has been unclear whether other species also base their decision to cooperate on the quality of received help. Previous experiments have demonstrated that Norway rats, Rattus norvegicus, cooperate using direct reciprocity decision rules in a variant of the iterated Prisoner''s Dilemma, where they preferentially help cooperators instead of defectors. But, as the quality of obtained benefits has not been varied, it is yet unclear whether rats use the value of received help as decision criterion to pay help back. Here, we tested whether rats distinguish between different cooperators depending purely on the quality of their help. Our data show that a rat''s propensity to reciprocate help is, indeed, adjusted to the perceived quality of the partner''s previous help. When cooperating with two conspecific partners expending the same effort, rats apparently rely on obtained benefit to adjust their level of returned help.     

Evaluating an icon of population persistence: the Devil's Hole pupfish

The Devil''s Hole pupfish Cyprinodon diabolis has iconic status among conservation biologists because it is one of the World''s most vulnerable species. Furthermore, C. diabolis is the most widely cited example of a persistent, small, isolated vertebrate population; a chronic exception to the rule that small populations do not persist long in isolation. It is widely asserted that this species has persisted in small numbers (less than 400 adults) for 10 000–20 000 years, but this assertion has never been evaluated. Here, we analyse the time series of count data for this species, and we estimate time to coalescence from microsatellite data to evaluate this hypothesis. We conclude that mean time to extinction is approximately 360–2900 years (median 410–1800), with less than a 2.1% probability of persisting 10 000 years. Median times to coalescence varied from 217 to 2530 years, but all five approximations had wide credible intervals. Our analyses suggest that Devil''s Hole pupfish colonized this pool well after the Pleistocene Lakes receded, probably within the last few hundred to few thousand years; this could have occurred through human intervention.     

Parallel usage of medicinal plants by africans and their caribbean descendants

Cultivated plants are cited by anthropologists as important indicators of man’s past. Medicinal species, to a large extent, have been overlooked even though in some cases these plants represent some of the social and cultural traditions of the people who use them. A number of cultivated plants have been traced from the Old World to the New World and are generally believed to have been carried there by European explorers and early settlers. However, some evidence has been accumulating to indicate that there may have been contacts other than by European colonists. One trade route that has been neglected is that of the slave trade from west Africa to the Caribbean. Three plant species,Citrus aurantifolia, Ricinus communis andAbrus precatorius, may exemplify the role and use of this route. They also indicate the migration and assimilation of west African Fulani, Hausa, and Mandingo cultures and Obeah religion into Caribbean society.     

Evaluating the accuracy and biological meaning of visits to RFID‐enabled bird feeders using video

Radio‐frequency identification (RFID) technology has gained popularity in ornithological studies as a way to collect large quantities of data to answer specific biological questions, but few published studies report methodologies used for validating the accuracy of RFID data. Further, connections between the RFID data and the behaviors of interest in a study are not always clearly established. These methodological deficiencies may seriously impact a study''s results and subsequent interpretation. We built RFID‐equipped bird feeders and mounted them at three sites in Tompkins County, New York. We deployed passive integrated transponder tags on black‐capped chickadees, tufted titmice, and white‐breasted nuthatches and used a GoPro video camera to record the three tagged species at the feeders. We then reviewed the video to determine the accuracy of the RFID reader and understand the birds’ behavior at the feeders. We found that our RFID system recorded only 34.2% of all visits by tagged birds (n = 237) and that RFID detection increased with the length of a visit. We also found that our three tagged species and two other species that visited the feeders, American goldfinch and hairy woodpecker, retrieved food in 79.5% of their visits. Chickadees, titmice, nuthatches, and woodpeckers spent, on average, 2.3 s at feeders to collect one seed per visit. In contrast, goldfinches spent an average of 9.0 s at feeders and consumed up to 30 seeds per visit. Our results demonstrate the importance of confirming detection accuracy and that video can be used to identify behavioral characteristics associated with an RFID reader''s detections. This simple—yet time‐intensive—method for assessing the accuracy and biological meaning of RFID data is useful for ornithological studies but can be used in research focusing on various taxa and study systems.     

Host–parasite coevolution: Partitioning the effects of natural selection and environmental change using coupled Price equations

George Price showed how the effects of natural selection and environmental change could be mathematically partitioned. This partitioning may be especially useful for understanding host–parasite coevolution, where each species represents the environment for the other species. Here, we use coupled Price equations to study this kind of antagonistic coevolution. We made the common assumption that parasites must genetically match their host''s genotype to avoid detection by the host''s self/nonself recognition system, but we allowed for the possibility that non‐matching parasites have some fitness. Our results show how natural selection on one species results in environmental change for the other species. Numerical iterations of the model show that these environmental changes can periodically exceed the changes in mean fitness due to natural selection, as suggested by R.A. Fisher. Taken together, the results give an algebraic dissection of the eco‐evolutionary feedbacks created during host–parasite coevolution.