The role of abiotic and biotic factors in determining coexistence of multiple pollinators in the yucca–yucca moth mutualism

The determinants of a species' geographic distribution are a combination of both abiotic and biotic factors. Environmental niche modeling of climatic factors has been instrumental in documenting the role of abiotic factors in a species' niche. Integrating this approach with data from species interactions provides a means to assess the relative roles of abiotic and biotic components. Here, we examine whether the high host specificity typically exhibited in the active pollination mutualism between yuccas and yucca moths is the result of differences in climatic niche requirements that limit yucca moth distributions or the result of competition among mutualistic moths that would co‐occur on the same yucca species. We compared the species distribution models of two Tegeticula pollinator moths that use the geographically widespread plant Yucca filamentosa. Tegeticula yuccasella occurs throughout eastern North America whereas T. cassandra is restricted to the southeastern portion of the range, primarily occurring in Florida. Species distribution models demonstrate that T. cassandra is restricted climatically to the southeastern United States and T. yuccasella is predicted to be able to live across all of eastern North America. Data on moth abundances in Florida demonstrate that both moth species are present on Y. filamentosa; however, T. cassandra is numerically dominant. Taken together, the results suggest that moth geographic distributions are heavily influenced by climate, but competition among pollinating congeners will act to restrict populations of moth species that co‐occur.     

Estimating migratory connectivity of birds when re‐encounter probabilities are heterogeneous

Understanding the biology and conducting effective conservation of migratory species requires an understanding of migratory connectivity – the geographic linkages of populations between stages of the annual cycle. Unfortunately, for most species, we are lacking such information. The North American Bird Banding Laboratory (BBL) houses an extensive database of marking, recaptures and recoveries, and such data could provide migratory connectivity information for many species. To date, however, few species have been analyzed for migratory connectivity largely because heterogeneous re‐encounter probabilities make interpretation problematic. We accounted for regional variation in re‐encounter probabilities by borrowing information across species and by using effort covariates on recapture and recovery probabilities in a multistate capture–recapture and recovery model. The effort covariates were derived from recaptures and recoveries of species within the same regions. We estimated the migratory connectivity for three tern species breeding in North America and over‐wintering in the tropics, common (Sterna hirundo), roseate (Sterna dougallii), and Caspian terns (Hydroprogne caspia). For western breeding terns, model‐derived estimates of migratory connectivity differed considerably from those derived directly from the proportions of re‐encounters. Conversely, for eastern breeding terns, estimates were merely refined by the inclusion of re‐encounter probabilities. In general, eastern breeding terns were strongly connected to eastern South America, and western breeding terns were strongly linked to the more western parts of the nonbreeding range under both models. Through simulation, we found this approach is likely useful for many species in the BBL database, although precision improved with higher re‐encounter probabilities and stronger migratory connectivity. We describe an approach to deal with the inherent biases in BBL banding and re‐encounter data to demonstrate that this large dataset is a valuable source of information about the migratory connectivity of the birds of North America.     

Niche shifts during the global invasion of the Asian tiger mosquito, Aedes albopictus Skuse (Culicidae), revealed by reciprocal distribution models

Aim Niche‐based distribution models are often used to predict the spread of invasive species. These models assume niche conservation during invasion, but invasive species can have different requirements from populations in their native range for many reasons, including niche evolution. I used distribution modelling to investigate niche conservatism for the Asian tiger mosquito (Aedes albopictus Skuse) during its invasion of three continents. I also used this approach to predict areas at risk of invasion from propagules originating from invasive populations. Location Models were created for Southeast Asia, North and South America, and Europe. Methods I used maximum entropy (Maxent ) to create distribution models using occurrence data and 18 environmental datasets. One native model was created for Southeast Asia; this model was projected onto North America, South America and Europe. Three models were created independently for the non‐native ranges and projected onto the native range. Niche overlap between native and non‐native predictions was evaluated by comparing probability surfaces between models using real data and random models generated using a permutation approach. Results The native model failed to predict an entire region of occurrences in South America, approximately 20% of occurrences in North America and nearly all Italian occurrences of A. albopictus. Non‐native models poorly predict the native range, but predict additional areas at risk for invasion globally. Niche overlap metrics indicate that non‐native distributions are more similar to the native niche than a random prediction, but they are not equivalent. Multivariate analyses support modelled differences in niche characteristics among continents, and reveal important variables explaining these differences. Main conclusions The niche of A. albopictus has shifted on invaded continents relative to its native range (Southeast Asia). Statistical comparisons reveal that the niche for introduced distributions is not equivalent to the native niche. Furthermore, reciprocal models highlight the importance of controlling bi‐directional dispersal between native and non‐native distributions.     

Population genomic evidence for multiple Pliocene refugia in a montane‐restricted harvestman (Arachnida,Opiliones, Sclerobunus robustus) from the southwestern United States

The integration of ecological niche modelling into phylogeographic analyses has allowed for the identification and testing of potential refugia under a hypothesis‐based framework, where the expected patterns of higher genetic diversity in refugial populations and evidence of range expansion of nonrefugial populations are corroborated with empirical data. In this study, we focus on a montane‐restricted cryophilic harvestman, Sclerobunus robustus, distributed throughout the heterogeneous Southern Rocky Mountains and Intermontane Plateau of southwestern North America. We identified hypothetical refugia using ecological niche models (ENMs) across three time periods, corroborated these refugia with population genetic methods using double‐digest RAD‐seq data and conducted population‐level phylogenetic and divergence dating analyses. ENMs identify two large temporally persistent regions in the mid‐latitude highlands. Genetic patterns support these two hypothesized refugia with higher genetic diversity within refugial populations and evidence for range expansion in populations found outside hypothesized refugia. Phylogenetic analyses identify five to six genetically divergent, geographically cohesive clades of S. robustus. Divergence dating analyses suggest that these separate refugia date to the Pliocene and that divergence between clades pre‐dates the late Pleistocene glacial cycles, while diversification within clades was likely driven by these cycles. Population genetic analyses reveal effects of both isolation by distance (IBD) and isolation by environment (IBE), with IBD more important in the continuous mountainous portion of the distribution, while IBE was stronger in the populations inhabiting the isolated sky islands of the south. Using model‐based coalescent approaches, we find support for postdivergence migration between clades from separate refugia.     

Effect of geographic background and equilibrium state on niche model transferability: predicting areas of invasion of Leptoglossus occidentalis

Niche conservatism providing support for using ecological niche modeling in biological invasions has been widely noticed, however, the equilibrium state and geographic background effect on niche model transferability has received scant attention. The western conifer seed bug, Leptoglossus occidentalis, native to western North America, has expanded its range eastward and has become an invasive pest in Europe and Asia. Niche models calibrated on the ranges of a small native population and two large expanding populations were compared. We found that the climate niche of L. occidentalis is conserved during its steady expansion in North America and rapid spread in Europe. Models based on the small western native range successfully captured the eastern expanding and introduced European populations, whereas the large area-based models varied with the presumed state of equilibrium. The equilibrium state based model succeeded but the non-equilibrium based model failed to predict the range in Europe. Our study estimates global invasion risk zones for L. occidentalis and suggests that, based on niche conservatism, modeling based on a reasonable geographic distribution at a climatic equilibrium of a species could guarantee the transferability of niche model prediction. Caution is warranted in interpreting low niche model transferability with niche differentiation and forwarding message for management strategy.     

Phylogeography of a widespread small carnivore,the western spotted skunk (Spilogale gracilis) reveals temporally variable signatures of isolation across western North America

We analyzed phylogeographic patterns in the western spotted skunk, Spilogale gracilis Merriam, 1890 (Carnivora: Mephitidae) in relation to historical events associated with Pre‐Pleistocene Divergence (PPD) and Quaternary climate change (QCC) using mitochondrial DNA from 97 individuals distributed across Western North America. Divergence times were generated using BEAST to estimate when isolation in putative refugia occurred. Patterns and timing of demographic expansion was performed using Bayesian skyline plot. Putative climatic refugia resulting from Quaternary climate change were identified using paleoecological niche modeling and divergence dates compared to major vicariant events associated with Pre‐Pleistocene conditions. We recovered three major mitochondrial clades corresponding to western North America (California, Baja, and across the Great Basin), east‐central North America (Texas, central Mexico, New Mexico), and southwestern Arizona/northwestern Mexico. Time to most recent common ancestor for S. gracilis occurred ~1.36 Ma. Divergence times for each major clade occurred between 0.25 and 0.12 Ma, with signature of population expansion occurring 0.15 and 0.10 Ma. Ecological niche models identified three potential climatic refugia during the Last Interglacial, (1) west coast of California and Oregon, (2) northwestern Mexico, and (3) southern Texas/northeastern Mexico as well as two refugia during the Last Glacial Maximum, (1) western USA and (2) southern Texas/northeastern Mexico. This study supports PPD in shaping species‐level diversity compared to QCC‐driven changes at the intraspecific level for Spilogale, similar to the patterns reported for other small mammals (e.g., rodents and bats). Phylogeographic patterns also appear to have been shaped by both habitat and river vicariance, especially across the desert southwest. Further, continuing climate change during the Holocene coupled with anthropogenic modifications during the Anthropocene appears to be removing both of these barriers to current dispersal of western spotted skunks.     

A trans‐national monarch butterfly population model and implications for regional conservation priorities

1. The monarch has undergone considerable population declines over the past decade, and the governments of Mexico, Canada, and the United States have agreed to work together to conserve the species. 2. Given limited resources, understanding where to focus conservation action is key for widespread species like monarchs. To support planning for continental‐scale monarch habitat restoration, we address the question of where restoration efforts are likely to have the largest impacts on monarch butterfly (Danaus plexippus Linn.) population growth rates. 3. We present a spatially explicit demographic model simulating the multi‐generational annual cycle of the eastern monarch population, and use the model to examine management scenarios, some of which focus on particular regions of North America. 4. Improving the monarch habitat in the north central or southern parts of the monarch range yields a slightly greater increase in the population growth rate than restoration in other regions. However, combining restoration efforts across multiple regions yields population growth rates above 1 with smaller simulated improvements in habitat per region than single‐region strategies. 5. S ynthesis and applications: These findings suggest that conservation investment in projects across the full monarch range will be more effective than focusing on one or a few regions, and will require international cooperation across many land use categories.     

Population genetic structure of a common host predicts the spread of white‐nose syndrome,an emerging infectious disease in bats

Landscape complexity influences patterns of animal dispersal, which in turn may affect both gene flow and the spread of pathogens. White‐nose syndrome (WNS) is an introduced fungal disease that has spread rapidly throughout eastern North America, causing massive mortality in bat populations. We tested for a relationship between the population genetic structure of the most common host, the little brown myotis (Myotis lucifugus), and the geographic spread of WNS to date by evaluating logistic regression models of WNS risk among hibernating colonies in eastern North America. We hypothesized that risk of WNS to susceptible host colonies should increase with both geographic proximity and genetic similarity, reflecting historical connectivity, to infected colonies. Consistent with this hypothesis, inclusion of genetic distance between infected and susceptible colonies significantly improved models of disease spread, capturing heterogeneity in the spatial expansion of WNS despite low levels of genetic differentiation among eastern populations. Expanding our genetic analysis to the continental range of little brown myotis reveals strongly contrasting patterns of population structure between eastern and western North America. Genetic structure increases markedly moving westward into the northern Great Plains, beyond the current distribution of WNS. In western North America, genetic differentiation of geographically proximate populations often exceeds levels observed across the entire eastern region, suggesting infrequent and/or locally restricted dispersal, and thus relatively limited opportunities for pathogen introduction in western North America. Taken together, our analyses suggest a possibly slower future rate of spread of the WNS pathogen, at least as mediated by little brown myotis.     

INTEGRATIVE TESTING OF HOW ENVIRONMENTS FROM THE PAST TO THE PRESENT SHAPE GENETIC STRUCTURE ACROSS LANDSCAPES

Tests of the genetic structure of empirical populations typically focus on the correlative relationships between population connectivity and geographic and/or environmental factors in landscape genetics. However, such tests may overlook or misidentify the impact of candidate factors on genetic structure, especially when connectivity patterns differ between past and present populations because of shifting environmental conditions over time. Here we account for the underlying demographic component of population connectivity associated with a temporarily dynamic landscape in tests of the factors structuring population genetic variation in an Australian lizard, Lerista lineopunctulata, from 24 nuclear loci. Correlative tests did not support significant effect from factors associated with a static contemporary landscape. However, spatially explicit demographic modeling of genetic differentiation shows that changes in environmental conditions (as estimated from paleoclimatic data) and corresponding distributional shifts from the past to present landscape significantly structures genetic variation. Results from model‐based inference (i.e., from an integrative modeling approach that generates spatially explicit expectations that are tested with approximate Bayesian computation) contrasts with those from correlative analyses, highlighting the importance of expanding the landscape genetic perspective to tests the links between pattern and process, revealing how factors shape patterns of genetic variation within species.     

A rangewide herbarium‐derived dataset indicates high levels of gene flow in black cherry (Prunus serotina)

Isolation by Distance (IBD) is a genetic pattern in which populations geographically closer to one another are more genetically similar to each other than populations which are farther apart. Black cherry (Prunus serotina Ehrh.) (Rosaceae) is a forest tree species widespread in eastern North America, and found sporadically in the southwestern United States, Mexico, and Guatemala. IBD has been studied in relatively few North American plant taxa, and no study has rigorously sampled across the range of such a widespread species. In this study, IBD and overall genetic structure were assessed in eastern black cherry (P. serotina Ehrh. var. serotina), the widespread variety of eastern North America. Eastern North America. Prunus serotina Ehrh. var. serotina (Rosaceae). Dense sampling across the entire range of eastern black cherry was made possible by genotyping 15 microsatellite loci in 439 herbarium samples from all portions of the range. Mantel tests and STRUCTURE analyses were performed to evaluate the hypothesis of IBD and genetic structure. Mantel tests demonstrated significant but weak IBD, while STRUCTURE analyses revealed no clear geographic pattern of genetic groups. The modest geographic/genetic structure across the eastern black cherry range suggests widespread gene flow in this taxon. This is consistent with P. serotina's status as a disturbance‐associated species. Further studies should similarly evaluate IBD in species characteristic of low‐disturbance forests.     

Postglacial recolonization of North America by spadefoot toads: integrating niche and corridor modeling to study species’ range dynamics over geologic time

Understanding the factors that shape species’ distributions is a key topic in biogeography. As climates change, species can either cope with these changes through evolution, plasticity or by shifting their ranges to track the optimal climatic conditions. Ecological niche modeling (ENM) is a widespread technique in biogeography that estimates the niche of the organism by using occurrences and environmental data to estimate species’ potential distributions. ENMs are often criticized for failing to take species’ dispersal abilities into consideration. Here, we attempt to fill this gap by combining ENMs with dispersal and corridor modeling to study the range dynamics of North American spadefoot toads (Scaphiopodidae) over the Holocene. We first estimated the current and past distributions of spadefoot toads and then estimated their past distributions from the Last Glacial Maximum (LGM) to the present day. Then, we estimated how each taxon recolonized North American by using dispersal and corridor modeling. By combining these two modeling approaches we were able to 1) estimate the LGM refugia used by the North American spadefoot toads, 2) further refine these projections by estimating which of the putative LGM refugia contributed to the recolonization of North America via dispersal, and 3) estimate the relative influence of each LGM refugium to the current species’ distributions. The models were tested using previously published phylogeographic data, revealing a high degree of congruence between our models and the genetic data. These results suggest that combining ENMs and dispersal modeling over time is a promising approach to investigate both historical and future species’ range dynamics.     

Is phylogeography helpful for invasive species risk assessment? The case study of the bark beetle genus Dendroctonus

Despite evidence that conspecific lineages may display different climatic tolerances, most invasion risk assessment tools are calibrated without considering phylogeographic information. This study aims to investigate the existence of intraspecific niche divergence within a group of insect pests and to explore how the inclusion of phylogeographic information into species distribution models may alter the estimation of the potential distribution of a species. We studied North American bark beetles belonging to the genus Dendroctonus, a group of pests of conifers that are listed as quarantine species in numerous countries. Most Dendroctonus species exhibit strong genetic divergence that appears to be geographically structured and shaped by historical events and biotic factors. We modeled all lineage distributions within five species, using MaxEnt and Boosted Regression Trees, and compared the results with the models fitted at the species scale. Multivariate analysis and niche similarity and equivalency tests were additionally performed to investigate the existence and magnitude of climatic niche divergence between conspecific lineages. We also tested the ability of lineage‐based models to predict the region invaded by D. valens in China. Conspecific lineages showed a climatic niche more similar than expected by chance, but displayed different climatic envelopes in their native range and, consequently, different estimates of potential distributions. We also observed that classical models calibrated using the entire range of the species could potentially under‐ or overestimate the potential range of the species when compared to a global prediction built by aggregating lineage‐based projections. This study showed that the invasive phylogeographic lineage of D. valens has invaded regions characterized by climatic conditions highly similar to those encountered in its native range suggesting that preadaptations to environment might have played a role in this invasion. This study highlights how our perception of the invasion risk of pests may be altered when integrating phylogeographic information.     

Phylogeographic diversification of antelope squirrels (Ammospermophilus) across North American deserts

We investigated the biogeographic history of antelope squirrels, genus Ammospermophilus, which are widely distributed across the deserts and other arid lands of western North America. We combined range‐wide sampling of all currently recognized species of Ammospermophilus with a multilocus data set to infer phylogenetic relationships. We then estimated divergence times within identified clades of Ammospermophilus using fossil‐calibrated and rate‐calibrated molecular clocks. Lastly, we explored generalized distributional changes of Ammospermophilus since the last glacial maximum using species distribution models, and assessed responses to Quaternary climate change by generating demographic parameter estimates for the three wide‐ranging clades of A. leucurus. From our phylogenetic estimates we inferred strong phylogeographic structure within Ammospermophilus and the presence of three well‐supported major clades. Initial patterns of historical divergence were coincident with dynamic alterations in the landscape of western North America, and the formation of regional deserts during the Late Miocene and Pliocene. Species distribution models and demographic parameter estimates revealed patterns of recent population expansion in response to glacial retreat. When combined with evidence from co‐distributed taxa, the historical biogeography of Ammospermophilus provides additional insight into the mechanisms that impacted diversification of arid‐adapted taxa across the arid lands of western North America. We propose species recognition of populations of the southern Baja California peninsula to best represent our current understanding of evolutionary relationships among genetic units of Ammospermophilus. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 949–967.     

Evaluating niche changes during invasion with seasonal models in Capsella bursa-pastoris

Premise

Researchers often use ecological niche models to predict where species might establish and persist under future or novel climate conditions. However, these predictive methods assume species have stable niches across time and space. Furthermore, ignoring the time of occurrence data can obscure important information about species reproduction and ultimately fitness. Here, we assess compare ecological niche models generated from full-year averages to seasonal models.

Methods

In this study, we generate full-year and monthly ecological niche models for Capsella bursa-pastoris in Europe and North America to see if we can detect changes in the seasonal niche of the species after long-distance dispersal.

Results

We find full-year ecological niche models have low transferability across continents and there are continental differences in the climate conditions that influence the distribution of C. bursa-pastoris. Monthly models have greater predictive accuracy than full-year models in cooler seasons, but no monthly models can predict North American summer occurrences very well.

Conclusions

The relative predictive ability of European monthly models compared to North American monthly models suggests a change in the seasonal timing between the native range to the non-native range. These results highlight the utility of ecological niche models at finer temporal scales in predicting species distributions and unmasking subtle patterns of evolution.     

Invasion of Old World Phragmites australis in the New World: precipitation and temperature patterns combined with human influences redesign the invasive niche

After its introduction into North America, Euro‐Asian Phragmites australis became an aggressive invasive wetland grass along the Atlantic coast of North America. Its distribution range has since expanded to the middle, south and southwest of North America, where invasive P. australis has replaced millions of hectares of native plants in inland and tidal wetlands. Another P. australis invasion from the Mediterranean region is simultaneously occurring in the Gulf region of the United States and some countries in South America. Here, we analysed the occurrence records of the two Old World invasive lineages of P. australis (Haplotype M and Med) in both their native and introduced ranges using environmental niche models (ENMs) to assess (i) whether a niche shift accompanied the invasions in the New World; (ii) the role of biologically relevant climatic variables and human influence in the process of invasion; and (iii) the current potential distribution of these two lineages. We detected local niche shifts along the East Coast of North America and the Gulf Coast of the United States for Haplotype M and around the Mississippi Delta and Florida of the United States for Med. The new niche of the introduced Haplotype M accounts for temperature fluctuations and increased precipitation. The introduced Med lineage has enlarged its original subtropical niche to the tropics‐subtropics, invading regions with a high annual mean temperature (> ca. 10 °C) and high precipitation in the driest period. Human influence is an important factor for both niches. We suggest that an increase in precipitation in the 20th century, global warming and human‐made habitats have shaped the invasive niches of the two lineages in the New World. However, as the invasions are ongoing and human and natural disturbances occur concomitantly, the future distribution ranges of the two lineages may diverge from the potential distribution ranges detected in this study.     

Niche shift versus niche conservatism? Climatic characteristics of the native and invasive ranges of the Mediterranean house gecko (Hemidactylus turcicus)

Aim The use of ecological niche models (ENMs) to predict potential distributions of species is steadily increasing. A necessary assumption is that climatic niches are conservative, but recent findings of niche shifts during biological invasion indicate that this assumption is not always valid. Selection of predictor variables may be one reason for the observed shifts. In this paper we assess differences in climatic niches in the native and invaded ranges of the Mediterranean house gecko (Hemidactylus turcicus) in terms of commonly applied climate variables in ENMs. We analyse which variables are more conserved versus relaxed (i.e. subject to niche shift). Furthermore, we study the predictive power of different sets of climate variables. Location The Mediterranean region and North America. Methods We developed models using Maxent and various subsets of variables out of 19 bioclimatic layers including: (1) two subsets comprising almost all variables excluding only highly collinear ones; (2) two subsets with minimalistic variable sets of water availability and energy measures; (3) two subsets focused on temperature‐related parameters; (4) two subsets with precipitation‐related parameters; and (5) one subset comprising variables combining temperature and precipitation characteristics. Occurrence data from the native Mediterranean range were used to predict the potential introduced range in North America and vice versa. Degrees of niche similarity and conservatism were assessed using both Schoener's index and Hellinger distances. The significance of the results was tested using null models. Results The degree of niche similarity and conservatism varied greatly among the predictors and variable sets applied. Shifts observed in some variables could be attributed to active habitat selection while others apparently reflected background effects. Main conclusions The study was based on comprehensive occurrence data from all regions where Hemidactylus turcicus is present in Europe and North America, providing a robust foundation. Our results clearly indicate that the degree of conservatism of niches in H. turcicus largely varies among predictors and variable sets applied. Therefore, the extent of niche conservatism of variables applied should always be tested in ENMs. This has an important impact on studies of biological invasion, impacts of climate change and niche evolution.     

Genotyping‐in‐Thousands by sequencing reveals marked population structure in Western Rattlesnakes to inform conservation status

Delineation of units below the species level is critical for prioritizing conservation actions for species at‐risk. Genetic studies play an important role in characterizing patterns of population connectivity and diversity to inform the designation of conservation units, especially for populations that are geographically isolated. The northernmost range margin of Western Rattlesnakes (Crotalus oreganus) occurs in British Columbia, Canada, where it is federally classified as threatened and restricted to five geographic regions. In these areas, Western Rattlesnakes hibernate (den) communally, raising questions about connectivity within and between den complexes. At present, Western Rattlesnake conservation efforts are hindered by a complete lack of information on genetic structure and degree of isolation at multiple scales, from the den to the regional level. To fill this knowledge gap, we used Genotyping‐in‐Thousands by sequencing (GT‐seq) to genotype an optimized panel of 362 single nucleotide polymorphisms (SNPs) from individual samples (n = 461) collected across the snake's distribution in western Canada and neighboring Washington (USA). Hierarchical STRUCTURE analyses found evidence for population structure within and among the five geographic regions in BC, as well as in Washington. Within these regions, 11 genetically distinct complexes of dens were identified, with some regions having multiple complexes. No significant pattern of isolation‐by‐distance and generally low levels of migration were detected among den complexes across regions. Additionally, snakes within dens generally were more related than those among den complexes within a region, indicating limited movement. Overall, our results suggest that the single, recognized designatable unit for Western Rattlesnakes in Canada should be re‐assessed to proactively focus conservation efforts on preserving total genetic variation detected range‐wide. More broadly, our study demonstrates a novel application of GT‐seq for investigating patterns of diversity in wild populations at multiple scales to better inform conservation management.     

Global invasion by <Emphasis Type="Italic">Anthidium manicatum</Emphasis> (Linnaeus) (Hymenoptera: Megachilidae): assessing potential distribution in North America and beyond

The wool carder bee, Anthidium manicatum, is the most widely distributed unmanaged bee in the world. It was unintentionally introduced to North America in the late 1960s from Europe, and subsequently, into South America, New Zealand and the Canary Islands. We provide information on the local distribution, seasonal abundance and sex ratio of A. manicatum from samples collected in an intensive two-year survey across Utah, USA. Anthidium manicatum was detected in 10 of the 29 Utah counties, largely in urban and suburban settings. Combining presence-only and MaxEnt background data from literature, museum databases and new records from Utah, we constructed three species distribution models to examine the potential distribution of A. manicatum in its native Eurasian range as well as invaded ranges of North and South America. The A. manicatum model based on locality and background data from the species’ native range predicted 50% of the invasive records associated with high habitat suitability (HS ≥ 0.90). The invasive North American model predicted a much broader distribution of A. manicatum (214% increase); whereas, the South American model predicted a narrower distribution (88% decrease). The poor predictive power of the latter model in estimating suitable habitats in the invasive South American range of A. manicatum suggests that the bee may still be limited by the bioclimatic constraints associated with a novel environment. Estimates of niche similarity (D) between the native and invasive models find that the North America bioclimatic niche is more similar to the bioclimatic niche of the native model (D = 0.78), whereas the bioclimatic niche of the South America invasion is relatively dissimilar (D = 0.69). We discuss the naturalization of A. manicatum in North America, possibly through punctuated dispersal, the probability of suitable habitats across the globe and the synanthropy exhibited by this invasive species.     

Differential regional response of the bushy‐tailed woodrat (Neotoma cinerea) to late Quaternary climate change

Aim To reconstruct the regional biogeographical history of the bushy‐tailed woodrat, Neotoma cinerea (Rodentia: Cricetidae), across its distribution using multiple sources of information, including genetic data, ecological niche models and the palaeorecord. Location Western North America. Methods We analysed complete cytochrome b gene (1143 bp) sequences from 182 specimens of N. cinerea using Bayesian and coalescent methods to infer phylogenetic relationships, time of major divergences, and recent demographic trends. For comparison, we developed clade‐specific ecological niche models for groups of interest and analysed spatial trends of N. cinerea in the palaeorecord as well as temporal frequency trends across strata of individual palaeomiddens. Results We found two largely allopatric clades within N. cinerea, with several regionally distinct subclades showing contrasting recent population dynamics. Niche models showed consistent habitat at the Last Glacial Maximum (LGM) and modern times in the Rocky Mountains and northern United States, while the Great Basin may have been markedly less suitable at the LGM than today. The palaeorecord showed great spatio‐temporal variability in the presence of N. cinerea, but documents broad‐scale patterns of occupancy and regional population trends. Main conclusions The Quaternary dynamics and evolutionary history of N. cinerea appear to have been shaped by both vicariant events associated with geographical barriers and the availability of suitable habitat through time. Divergence of the two major clades dates to the Pliocene–Pleistocene transition, with clades separated by the Green and Colorado rivers and northern Rocky Mountain Pleistocene glaciations. We found largely concordant genetic, niche model and palaeorecord patterns suggesting long‐term population stability in the Rocky Mountains, while extant clades in the Great Basin and far north appear to have expanded or re‐expanded into these regions relatively recently. Furthermore, disjunct haplotype distributions, regional demographic history, and historical distribution of suitable habitat suggest that the Great Basin has been a particularly dynamic region.     

GENETIC POPULATION STRUCTURE AND LEVELS OF GENE FLOW IN THE STREAM DWELLING WATERSTRIDER,AQUARIUS (=GERRIS) REMIGIS (HEMIPTERA: GERRIDAE)

Gene flow, in combination with selection and drift, determines levels of differentiation among local populations. In this study we estimate gene flow in a stream dwelling, flightless waterstrider, Aquarius remigis. Twenty-eight Aquarius remigis populations from Quebec, Ontario, New Brunswick, Iowa, North Carolina, and California were genetically characterized at 15 loci using starch gel electrophoresis. Sampling over two years was designed for a hierarchical analysis of population structure incorporating variation among sites within streams, streams within watersheds, watersheds within regions, and regions within North America. Hierarchical F statistics indicated that only sites within streams maintained enough gene flow to prevent differentiation through drift (Nm = 27.5). Above the level of sites within streams gene flow is highly restricted (Nm ≤ 0.5) and no correlation is found between genetic and geographic distances. This agrees well with direct estimates of gene flow based on mark and recapture data, yielding an N_e of approximately 170 individuals. Previous assignment of subspecific status to Californian A. remigis is not supported by genetic distances between those populations and other populations in North America. Previous suggestion of specific status for south-eastern A. remigis is supported by genetic distances between North Carolina populations and other populations in North America, and a high proportion of region specific alleles in the North Carolina populations. However, because of the high degree of morphological and genetic variability throughout the range of this species, the assignment of specific or subspecific status to parts of the range may be premature.