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Aim: Quantifying niche shifts of non‐native species and their interactions with natives is vital in evaluating invasion risk yet remains difficult. Climate filtering and competition with native congeners are two important processes impacting niche changes and yielding contradictory predictions for the coexistence of non‐native and native species. Closely related species representing the Eastern Asia (EA)–Eastern North America (ENA) floristic disjunction provide a powerful yet unexplored system for assessing the relative roles of these two processes. Here, we tested three niche change scenarios (unfilling, expansion and stable) using EA species naturalized in ENA. We aim to answer: (1) which scenario is observed for naturalized species? and (2) how has niche overlap between EA and ENA congeners changed after naturalization? Location: ENA and EA. Time Period: Present. Major Taxa Studied: Angiosperms. Methods: Niches were estimated using both occurrences and predictions generated by ecological niche models. Niche changes of naturalized species and their niche overlap with natives were measured using Schoener's D. Contributions of niche expansion and unfilling on niche changes of naturalized niches were evaluated using hierarchical partitioning and linear regressions. We further measured pairwise phylogenetic distances among EA and ENA congeners and evaluated the association with niche overlap. Results: Unfilling‐dominated postintroduction niche changes of the naturalized species. EA species naturalized in ENA exhibited lower niche overlap with ENA native congeners compared with native range populations in EA. These results remain when considering time since introduction and potential physical dispersal limitations interpreted by projecting suitable niche space between EA and ENA. However, dispersal limitation may contribute to the degree of niche unfilling. Main Conclusions: Using intercontinental disjunct species as a study system, we found that naturalization is shaped jointly by climate filtering and competition with native congeners, providing valuable insights for evaluating invasion risk underlying global floristic exchanges. [ABSTRACT FROM AUTHOR]

The cross-species transmission (CST) of pathogens can have dramatic consequences, as highlighted by recent disease emergence events affecting human, animal and plant health. Understanding the ecological and evolutionary factors that increase the likelihood of disease agents infecting and establishing in a novel host is therefore an important research area. Previous work across different pathogens, including rabies virus (RABV), found that increased evolutionary distance between hosts reduces the frequency of cross-species transmission and of permanent host shifts. However, whether this effect of host relatedness still holds for transmission among recently diverged hosts is not well understood. We aimed to ask if high host relatedness can still increase the probability of a host shift between more recently diverged hosts, and the importance of this effect relative to ecological predictors. We first addressed this question by quantifying the CST frequency of RABV between North American bat species within the genus Myotis, using a multi-decade data set containing 128 nucleoprotein (N) RABV sequences from ten host species. We compared RABV CST frequency within Myotis to the rates of CST between nine genera of North American bat species. We then examined whether host relatedness or host range overlap better explains the frequency of CST seen between Myotis species. We found that at the within genus scale, host range overlap, rather than host relatedness best explains the frequency of CST events. Moreover, we found evidence of CST occurring among a higher proportion of species, and CST more frequently resulting in sustained transmission in the novel host in the Myotis dataset compared to the multi-genus dataset. Our results suggest that among recently diverged species, the ability to infect a novel host is no longer restricted by physiological barriers but instead is limited by physical contact. Our results improve predictions of where future CST events for RABV might occur and clarify the relationship between host divergence and pathogen emergence. [ABSTRACT FROM AUTHOR]

Modern North American carnivorous mammal assemblages consist of species from a single clade: the Carnivora. Carnivorans once coexisted with members of other meat-eating clades, including the creodonts (Hyaenodontida and Oxyaenida). Creodonts, however, went extinct in North America during the late Eocene and early Oligocene, potentially due to niche overlap and resource competition with contemporary carnivorans. In this study, we employ a community ecology approach to understand whether the dietary niches of coexisting creodonts and carnivorans overlapped during the late Eocene (Chadronian North American Land Mammal Age), a time when creodonts were dwindling and carnivorans were diversifying. We quantify niche overlap based on inferences of diet from carnassial tooth shape estimated using Orientation Patch Count, Dirichlet's Normal Surface Energy, and linear dental measurements as well as from body mass for all species in the Calf Creek Local Fauna of Cypress Hills, Saskatchewan (Treaty 4 land). Although creodonts and carnivorans shared characteristics of their carnassial tooth shape, suggesting similar chewing mechanics and feeding habits, we find that marked differences in body size likely facilitated niche partitioning, at least between the largest creodonts and carnivorans. Calculations of prey focus masses and prey mass spectra indicate that only the smallest creodont may have experienced significant competition for prey with the coeval carnivorans. We suggest that the ultimate extinction of creodonts from North America during the late Eocene and Oligocene was unlikely to have been driven by factors related to niche overlap with carnivorans. [ABSTRACT FROM AUTHOR]

Aim: Dispersal and subsequent adaptation to local environmental and climatic conditions play major roles in the evolution and current‐day distribution of plants and animals, but their relative importance is not always easy to disentangle. The aim of this study was to provide a comprehensive phylogenetic analysis of the terrestrial orchid genus Cypripedium to better understand the role of niche evolution and historical dispersal events in driving the radiation of the genus in North America and Eurasia. Location: Northern Hemisphere. Taxon: Cypripedium (Orchidaceae). Methods: We used a relaxed molecular clock analysis to infer phylogenetic relationships among 45 Cypripedium species and to estimate divergence times. Niche modelling was used to assess the potential distribution of each species in both continents, whereas ancestral area reconstructions using BioGeoBEARS were used to estimate changes in historical biogeography. Subsequently, the ancestral state of niche conditions was assessed for each species using maximum likelihood methods and we tested for phylogenetic signal in the evolution of niche conditions using Blomberg's K and Pagel's λ. A mantel test was used to test for a correlation between phylogenetic distances and niche overlap in Cypripedium. Results: We found that Cypripedium originated in Central America and underwent multiple dispersal events between North America and Eurasia after long‐distance seed dispersal or dispersal via the Bering land bridge. The mountainous area of Southwest China provided refuge areas for Cypripedium orchids during episodes of increased glaciation. Our results further showed that Cypripedium has gradually increased its tolerance to seasonal temperature changes, providing evidence for significant niche evolution through time. No significant correlation between current niches and phylogenetic relatedness was observed. Main conclusions: Our study provides clear evidence that repeated dispersal and adaptation to increased cooling after the Eocene−Oligocene Transition has contributed to the radiation of Cypripedium in the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

Aim: The plant species sharing ancestors now disjunctly distributed in eastern Asia (EAS) and eastern North America (ENA) have long been a biogeographic puzzle. Species within the EAS–ENA disjunct genera are presumed to exhibit niche conservatism, the tendency of closely related species to be more ecologically similar, reflecting lineages' common evolutionary history. However, the hypothesis has not been well examined at the species level. Location: EAS and ENA. Time period: Current. Major taxa studied: Species within the EAS–ENA disjunct genera. Methods: We compiled data on climate, species occurrence, growth form, and phylogeny to examine niche conservatism. We first built a phylogenetic tree to select intercontinental congeneric pairwise species and obtained their divergence times. We then quantified the observed niche overlaps with Schoener's D, which has a 0–1 range, based on species occurrence and climate of species' native ranges. To obtain projected distributions, each species' niche was projected to the non‐native region using ensemble ecological niche models. Projected‐related niche overlaps were then calculated using projected distributions and the corresponding climatic conditions. Results: Average observed niche overlaps of congeneric pairwise species were relatively small:.124,.211 and.109 for all, herbaceous and woody species, respectively. Both observed and projected‐related niche overlaps had significant negative relationships with divergence times of intercontinental congeneric pairwise species, with niche overlap for herbaceous species being higher than that for woody plants when controlling for divergence times. Main conclusions: We conclude that the significant negative relationships between niche overlap and divergence times of congeneric pairwise species confirm niche conservatism among species of EAS–ENA disjunct plants and that the extent of niche conservatism is slightly different for herbaceous and woody plants. These findings suggest the potential role of allopatric speciation in EAS, and could help to understand the evolutionary history and the Asian‐bias diversity pattern of the EAS–ENA disjunct plants. [ABSTRACT FROM AUTHOR]

Animal foraging and competition are defined by the partitioning of three primary niche axes: space, time, and resources. Human disturbance is rapidly altering the spatial and temporal niches of animals, but the impact of humans on resource consumption and partitioning--arguably the most important niche axis--is poorly understood. We assessed resource consumption and trophic niche partitioning as a function of human disturbance at the individual, population, and community levels using stable isotope analysis of 684 carnivores from seven communities in North America. We detected significant responses to human disturbance at all three levels of biological organization: individual carnivores consumed more human food subsidies in disturbed landscapes, leading to significant increases in trophic niche width and trophic niche overlap among species ranging from mesocarnivores to apex predators. Trophic niche partitioning is the primary mechanism regulating coexistence in many communities, and our results indicate that humans fundamentally alter resource niches and competitive interactions among terrestrial consumers. Among carnivores, niche overlap can trigger interspecific competition and intraguild predation, while the consumption of human foods significantly increases human-carnivore conflict. Our results suggest that human disturbances, especially in the form of food subsidies, may threaten carnivores by increasing the probability of both interspecific competition and human-carnivore conflict. Ultimately, these findings illustrate a potential decoupling of predator-prey dynamics, with impacts likely cascading to populations, communities, and ecosystems. [ABSTRACT FROM AUTHOR]

Organisms with multiple biotic attributes may also have conflicting niche determinants, and we assessed whether the realized niche reflects single or multiple biotic attributes. A group of all‐female salamanders found in eastern North America (unisexual salamanders; Ambystoma spp.) embody two potentially competing biotic states: hybridism and obligate reproductive parasitism. In theory, hybrids should occupy areas that are transitional to those used by parental species, parasites must live in syntopy with their hosts, and parasites that engage in ecological competition with hosts should be most successful in habitats that are moderately suitable for hosts. We built niche models for bisexual salamanders (Ambystoma laterale and Ambystoma jeffersonianum), as well as for unisexual Ambystoma that posses nuclear DNA from both of these species. These unisexuals are both phenotypic hybrids and obligate reproductive parasites of the bisexual species. We characterized realized niches predicted for unisexual Ambystoma via a hybrid‐framework model (e.g., using environmental predictors) and a parasite‐framework model (e.g., using host suitability predictors). Model validation using ancillary data permitted evaluation of which biotic state (hybrid vs. parasite) fit the observed patterns of occupancy. The hybrid model conformed strongly with predictions that the unisexual niche would be transitional between A. laterale and A. jeffersonianum bisexuals. Average annual temperatures and terrestrial salamander species richness (a proxy for competition) were particularly descriptive of parental niches and hybrid occupancy of transitional environments. While the parasite model behaved as expected, model validation did not fully corroborate its utility for determining patterns of occupancy. Instead, model selection revealed that the hybrid model was more descriptive of unisexual occurrence than the parasite model. Despite the fundamental importance of reproductive parasitism to the persistence of unisexual Ambystoma, we suggest that hybridism has greater contribution to the realized niche. When species have competing ecological attributes, one primary biotic state may dominate as a determinant of the realized niche. [ABSTRACT FROM AUTHOR]

Premise: The distributions of plant clades are shaped by abiotic and biotic factors as well as historical aspects such as center of origin. Dispersals between distant areas may lead to niche evolution when lineages are established in new environments. Alternatively, dispersing lineages may exhibit niche conservatism, moving between areas with similar environmental conditions. Here we test these contrasting hypotheses in the Datureae clade (Solanaceae)., Methods: We used maximum likelihood methods to estimate the ancestral range of Datureae along with the history of biogeographic events. We then characterized the niche of each taxon using climatic and soil variables and tested for shifts in environmental niche optima. Finally, we examined how these shifts relate to the niche breadth of taxa and clades within Datureae and the degree of overlap between them., Results: Datureae originated in the Andes and subsequently expanded its range to North America and non-Andean regions of South America. The ancestral niche, and that of most Datura and Trompettia species, is dry, while Brugmansia species likely shifted toward a more mesic environment. Nonetheless, most Datureae present moderate to high overlap in niche breadth today., Conclusions: The expansion of Datureae into North America was associated with niche conservatism, with dispersal into similarly dry areas as occupied by the ancestral lineage. Subsequent niche evolution, including the apparent shift to a mesic niche in Brugmansia, diversified the range of habitats occupied by species in the tribe Datureae but also led to significant niche overlap among the three genera., (© 2019 Botanical Society of America.)

Premise of the Study: Bipolar species represent the greatest biogeographical disjunction on Earth, raising many questions about the colonization and adaptive processes behind such striking distribution. We investigated climatic niche differences of five Carex bipolar species in North and South America to assess niche shifts between these two regions. Moreover, we assessed potential distribution changes with future climate change., Methods: We used 1202 presence data points from herbarium specimens and 19 bioclimatic variables to assess climatic niche differences and potential distributions among the five species using ordination methods and Maxent., Key Results: The niche overlap analyses showed low levels of niche filling and high climatic niche expansion between North and South America. Carex macloviana and C. maritima showed the greatest niche expansion (60% and 96%, respectively), followed by C. magellanica (45%) and C. microglochin (39%). Only C. canescens did not colonize new environments (niche expansion = 0.2%). In contrast, all species but C. magellanica had niche filling that was <40%; hence, they are absent in the south from many environments they inhabit in North America. Climate change will push all species toward higher latitudes and elevation, reducing the availability of suitable environments., Conclusions: The colonization of South America seems to have involved frequent climatic niche shifts. Most species have colonized new environments from those occupied in the North. Observed niche shifts appear congruent with time since colonization and with current genetic structure within species. In these cold-dwelling species, climate change will most likely decrease their suitable environments in the future., (© 2017 Botanical Society of America.)