Introduction: Social Complexity and the Bow in the Prehistoric North American Record

This Special Issue of Evolutionary Anthropology grew out of a symposium at the 2012 Society for American Archaeology (SAA) meeting in Memphis, Tennessee (April 18–22). The goal of the symposium was to explore what we will argue is one of the most important and promising opportunities in the global archeological enterprise. In late prehistoric North America, the initial rise of cultures of strikingly enhanced complexity and the local introduction of a novel weapon technology, the bow, apparently correlate intimately in a diverse set of independent cases across the continent, as originally pointed out by Blitz. 1 If this empirical relationship ultimately proves robust, it gives us an unprecedented opportunity to evaluate hypotheses for the causal processes producing social complexity and, by extension, to assess the possibility of a universal theory of history. The rise of comparably complex cultures was much more recent in North America than it was elsewhere and the resulting fresher archeological record is relatively well explored. These and other features make prehistoric North America a unique empirical environment. Together, the symposium and this issue have brought together outstanding investigators with both empirical and theoretical expertise. The strong cross‐feeding and extended interactions between these investigators have given us all the opportunity to advance the promising exploration of what we call the North American Neolithic transitions. Our goal in this paper is to contextualize this issue.     

Large-scale terrestrial gastropod community composition patterns in the Great Lakes region of North America

Abstract: Previous ordination studies of land snail community composition have been limited to four or fewer habitat types from sites separated by no more than 300 km. To investigate the nature of large-scale patterns, North American land snail assemblages at 421 sites, representing 26 habitat types and covering a 1400 × 800 km area, were ordinated using global, nonmetric multi-dimensional scaling (NMDS). These data were then subjected to model-based cluster analysis and kmeans clustering to identify the main compositional groups and most important environmental covariables. Six primary compositional groups were identified. Three of these largely represent upland forest and rock outcrop sites, while the remaining largely represent either lowland forest, lowland grassland or upland grassland habitats. The geographical location and moisture level of sites also influences community composition. A strong compositional difference exists between sites having duff vs. turf soil surface layers. Only 8% of sites were improperly classified when soil surface architecture was used as the sole predictor variable. Fully 43% of taxa exhibited significant preferences towards one of these surface types, while only 15% of relatively common (10 + occurrence) taxa showed no preferences. Twelve groups of closely related taxa within the same genus had members that favoured different surface types, indicating that differential selection pressures have existed over evolutionary time scales. While turf faunas appeared unaffected by anthropogenic disturbance, duff faunas were strongly impacted, suggesting that their conservation will require protection of soil surface architecture.     

One haploid parent contributes 100% of the gene pool for a widespread species in northwest North America

The monoicous peatmoss Sphagnum subnitens has a tripartite distribution that includes disjunct population systems in Europe (including the Azores), northwestern North America and New Zealand. Regional genetic diversity was highest in European S. subnitens but in northwestern North America, a single microsatellite‐based multilocus haploid genotype was detected across 16 sites ranging from Coos County, Oregon, to Kavalga Island in the Western Aleutians (a distance of some 4115 km). Two multilocus haploid genotypes were detected across 14 sites on South Island, New Zealand. The microsatellite‐based regional genetic diversity detected in New Zealand and North American S. subnitens is the lowest reported for any Sphagnum. The low genetic diversity detected in both of these regions most likely resulted from a founder event associated with vegetative propagation and complete selfing, with one founding haploid plant in northwest North America and two in New Zealand. Thus, one plant appears to have contributed 100% of the gene pool for the population systems of S. subnitens occurring in northwest North America, and this is arguably the most genetically uniform group of plants having a widespread distribution yet detected. Although having a distribution spanning 12.5° of latitude and 56° of longitude, there was no evidence of any genetic diversification in S. subnitens in northwest North America. No genetic structure was detected among the three regions, and it appears that European plants of S. subnitens provided the source for New Zealand and northwest North American populations.     

Zoogeography of the San Andreas Fault system: Great Pacific Fracture Zones correspond with spatially concordant phylogeographic boundaries in western North America

The purpose of this article is to provide an ultimate tectonic explanation for several well‐studied zoogeographic boundaries along the west coast of North America, specifically, along the boundary of the North American and Pacific plates (the San Andreas Fault system). By reviewing 177 references from the plate tectonics and zoogeography literature, I demonstrate that four Great Pacific Fracture Zones (GPFZs) in the Pacific plate correspond with distributional limits and spatially concordant phylogeographic breaks for a wide variety of marine and terrestrial animals, including invertebrates, fish, amphibians, reptiles, birds, and mammals. These boundaries are: (1) Cape Mendocino and the North Coast Divide, (2) Point Conception and the Transverse Ranges, (3) Punta Eugenia and the Vizcaíno Desert, and (4) Cabo Corrientes and the Sierra Transvolcanica. However, discussion of the GPFZs is mostly absent from the zoogeography and phylogeography literature likely due to a disconnect between biologists and geologists. I argue that the four zoogeographic boundaries reviewed here ultimately originated via the same geological process (triple junction evolution). Finally, I suggest how a comparative phylogeographic approach can be used to test the hypothesis presented here.     

Mammalian turnover and community structure in the Paleocene of North America

The effects of faunal turnover on mammalian community structure are evaluated for 17 faunal zones of the North American Paleocene through early Eocene land mammal ages (Puercan through early Wasatchian). Generic disappearances were significantly high at the end of the Puercan, Torrejonian, and Tiffanian land mammal ages, but appearances were significantly high only during the early Puercan. Generic richness rose rapidly in the early Puercan, remained stable throughout most of the Paleocene, and increased from the late Paleocene into the early Eocene. The null hypothesis that generic turnover clustered preferentially according to dentally defined trophic or body size categories could be rejected or attributed to sampling problems for all but the early (Pu0) and late Paleocene (Ti5‐Cf2). Early Paleocene change in community structure most probably represented endemic radiation of mammals into previously unoccupied niches. Community restructuring in the late Paleocene reflected a complex of causes, including climatic wanning, intercontinental dispersal, and competition.     

Distribution and systematics of the freshwater red algal family Thoreaceae in North America

North American populations and type specimens of Thorea and Nemalionopsis were compared using multivariate morphometrics and image analysis. We continue to recognise the separation of the two genera based on spore-bearing branch-to-assimilatory filament length ratio and assimilatory filament density (≤0·3 and loose for Thorea and ≥0·6 and compressed for Nemalionopsis, respectively). Four species of Thorea were distinguished worldwide: T. hispida (syn. T. andina, T. lehmannii, T. ramosissima), T. violacea (syn. T. bachmannii, T. brodensis, T. gaudichaudii, T. okadae, T. prowsei and T. riekei), T. clavata and T. zollingeri. The former two species have variable branched, non-clavate assimilatory filaments, whereas the latter two have unbranched, clavate assimilatory filaments. Thorea hispida has copious secondary branches while T. violacea is sparsely branched. Thorea clavata is differentiated from T. zollingeri by having fewer monosporangia per cluster. Two of these species were found in North America: T. hispida in Mexico, Grenada and Jamaica, and T. violacea in Texas and Mexico. Two species of Nemalionopsis were differentiated: N. shawii with long assimilatory filaments composed of barrel-shaped cells and n. tortuosa (syn. N. shawii f. caroliniana) with short assimilatory filaments having cylindrical cells. Only N. tortuosa has been collected on the continent, from Florida, Louisiana and North Carolina.     

Bryozoan provinces and patterns of generic evolution and extinction in the Late Ordovician of North America

The Late Ordovician bryozoan genera of central and southeastern North America are geographically distributed in three biotic provinces, separated by boundaries reflecting major lithofacies differences. The central Cincinnati Province contains most of the North American endemic genera, and represents a narrow ecological zone separating the clastic wedges of the marginal Reedsville-Lorraine Province from the cratonic carbonate platform of the Red River-Stony Mountain Province. The provinces provided major life zones, or biomes, for each of the five bryozoan orders. Genera comprising the provinces differed as well in morphologic complexity, geochronologic survivorship, tiering, endemism and eurytopy. Regions on either side of the Cincinnati Province were dominated by inferred immigrants from Baltoscandia. Al-logenic provincial succession produced time-averaged mixed faunas in regions near the provincial boundaries. Although most generic originations took place within the Cincinnati Province, evolutionary novelties are associated with the Reedsville-Lorraine Province. The loss of the diverse Cincinnati Province, connected with global cooling and a eustatic lowering of sea level, may have been a chief factor in the Late Ordovician extinction of bryozoan genera. Genera from the Red River-Stony Mountain Province differentially survived into the Silurian.     

The biogeography of aquatic macrophytes in North America since the Last Glacial Maximum

Aim To document the post‐glacial migration of the major aquatic macrophytes of North America. Location North America north of Mexico. Methods Aquatic macrophyte pollen were extracted from the North American Pollen Database. The modern pollen distribution was mapped and related to the climate to document the geographical and climatic constraints on these taxa. The fossil pollen were mapped at 2‐ka intervals for the past 21 ka. Results Numerous genera were present in ice‐free Alaska during the Last Glacial Maximum, and south of the Laurentide Ice Sheet in the southeast. Those taxa with the widest modern climatic ranges migrated rapidly into ice‐marginal areas, first in the west and then in the east of North America. Subsequent changes in the range and abundance were smaller. Main conclusions There were four migration routes of aquatic macrophytes during the late‐glacial and post‐glacial periods: a southward migration from Alaska between 14–13 and ka, a northern migration in the west at the same time into the ice‐free Cordilleran region, and movements east and west of Appalachia as early as 19 ka for some taxa into the lower Mississippi and into the upper Mississippi and Great Lakes by 11 ka. As the Laurentide ice sheet wasted, aquatic taxa with the broadest contemporary temperature tolerances rapidly occupied ice‐marginal environments.     

Resilience of terrestrial and aquatic fauna to historical and future wildfire regimes in western North America

Wildfires in many western North American forests are becoming more frequent, larger, and severe, with changed seasonal patterns. In response, coniferous forest ecosystems will transition toward dominance by fire‐adapted hardwoods, shrubs, meadows, and grasslands, which may benefit some faunal communities, but not others. We describe factors that limit and promote faunal resilience to shifting wildfire regimes for terrestrial and aquatic ecosystems. We highlight the potential value of interspersed nonforest patches to terrestrial wildlife. Similarly, we review watershed thresholds and factors that control the resilience of aquatic ecosystems to wildfire, mediated by thermal changes and chemical, debris, and sediment loadings. We present a 2‐dimensional life history framework to describe temporal and spatial life history traits that species use to resist wildfire effects or to recover after wildfire disturbance at a metapopulation scale. The role of fire refuge is explored for metapopulations of species. In aquatic systems, recovery of assemblages postfire may be faster for smaller fires where unburned tributary basins or instream structures provide refuge from debris and sediment flows. We envision that more‐frequent, lower‐severity fires will favor opportunistic species and that less‐frequent high‐severity fires will favor better competitors. Along the spatial dimension, we hypothesize that fire regimes that are predictable and generate burned patches in close proximity to refuge will favor species that move to refuges and later recolonize, whereas fire regimes that tend to generate less‐severely burned patches may favor species that shelter in place. Looking beyond the trees to forest fauna, we consider mitigation options to enhance resilience and buy time for species facing a no‐analog future.     

Ecological niche modelling of montane mammals in the Great Basin, North America: examining past and present connectivity of species across basins and ranges

Aim The goal of this study was to determine the extent of suitable habitats across the basins and ranges of the Great Basin for 13 montane mammals in the present and during the Last Glacial Maximum (LGM). For all these mammal species, we test whether: (1) more suitable habitat was available in basin areas during the LGM; (2) suitable habitat shifted upwards in elevation between the LGM and the present; (3) more ranges have suitable habitat than are currently occupied; and (4) these species are currently restricted to suitable habitats at higher‐elevation range areas. We also examine whether and how much distributional response varies among these montane mammal species. Location The Great Basin of western North America. Methods We re‐examine the past and present distributions of 13 Great Basin montane mammals using ecological niche modelling techniques that utilize now widely available species occurrence data and new, fine‐scale past climatological GIS layers in the present and at the LGM. These methods provide an objective, repeatable means for visual comparison of past and present modelled distributions for species examined in previous biogeographical studies. Results Our results indicate greater areal and lower elevational suitable habitat in the LGM than at present for nearly all montane mammals, and that there is more suitable habitat at present than is currently occupied. Our results also show that lowland areas provide suitable dispersal routes between ranges for most of the montane mammals both at the LGM and at present. However, three of the 13 species have little to no predicted suitable habitat in the LGM near currently occupied ranges, in contrast to the pattern for the other 10. For these species, the model results support more recent long‐distance colonization. Main conclusions Our finding of suitable lowland dispersal routes in the present for most species supports and greatly extends similar findings from single‐species studies. Our results also provide a visually striking confirmation that changes in species distribution and colonization histories of Great Basin montane mammals vary in a fashion related to the tolerances and requirements of each of these species; this has previously been hypothesized but not rigorously tested for multiple montane mammals in the region.     

Of glaciers and refugia: a decade of study sheds new light on the phylogeography of northwestern North America

Glacial cycles have played a dominant role in shaping the genetic structure and distribution of biota in northwestern North America. The two major ice age refugia of Beringia and the Pacific Northwest were connected by major mountain chains and bordered by the Pacific Ocean. As a result, numerous refugial options were available for the regions taxa during glacial advances. We reviewed the importance of glaciations and refugia in shaping northwestern North America’s phylogeographic history. We also tested whether ecological variables were associated with refugial history. The recurrent phylogeographic patterns that emerged were the following: (i) additional complexity, i.e. refugia within refugia, in both Beringia and the Pacific Northwest; and (ii) strong evidence for cryptic refugia in the Alexander Archipelago and Haida Gwaii, the Canadian Arctic and within the ice‐sheets. Species with contemporary ranges that covered multiple refugia, or those with high dispersal ability, were significantly more likely to have resided in multiple refugia. Most of the shared phylogeographic patterns can be attributed to multiple refugial locales during the last glacial maximum or major physiographic barriers like rivers and glaciers. However, some of the observed patterns are much older and appear connected to the orogeny of the Cascade‐Sierra chain or allopatric differentiation during historic glacial advances. The emergent patterns from this review suggest we should refine the classic Beringian‐southern refugial paradigm for northwestern North American biota and highlight the ecological and evolutionary consequences of colonization from multiple refugia.     

Identifying mesopredator release in multi-predator systems: a review of evidence from North America

1. The mesopredator release hypothesis, defined as the change in distribution, abundance or behaviour of a middle-ranking predator in response to a decrease in density or distribution of an apex predator, is an increasingly popular topic in ecology. Terrestrial mesopredators have been reported as being released in multiple systems globally, particularly in North America, over the past century.
2. We reviewed 2687 scientific articles, of which we determined that 38 met our criteria for investigating mesopredator release (MR) in terrestrial North American mammalian predators.
3. We observed no support or mixed support for MR in 46% of all relevant studies, including conflicting evidence between measures (mesopredator distribution, abundance or behaviour) within a given study and among studies of the same community in different settings.
4. To advance the study of MR, we provide a conceptual framework that 1) highlights the multiple spatial, temporal and ecological scales at which mesopredator responses can occur; 2) suggests the relative weight of evidence for MR that is provided by measures of mesopredator responses at each scale; and 3) clearly defines the threshold for determining when MR is occurring.
5. In increasingly reshuffled predator communities with declining apex predators, there is a need for future studies to assess in more detail the contexts in which mesopredator behavioural responses scale up to the population-level processes and species-level distribution changes needed to identify these responses as MR.

     

Taxonomy and biogeography of the fiddler crabs (Ocypodidae: Genus Uca) of the Atlantic and Gulf coasts of eastern North America

Fifteen species of fiddler crabs are reported for eastern North America between Massachusetts and Quintana Roo, Mexico. Thirteen occur in the United States and 11 in Mexico, with eight in common to the two countries. Of 13 species in the Gulf of Mexico, five are endemic and a sixth is restricted largely to the peninsulas of Florida and Yucatan. The status of U. rapax in the northern Gulf remains to be resolved. Range limits of most species approximate one or the other of two sets of intersecting thermal and geological boundaries that subdivide the Gulf of Mexico along north-south and east-west axes. Species belonging to subgenus Minuca tend to replace one another at the thermally-controlled Carolinian-Caribbean marine biotic boundary across the Florida peninsula and northern Gulf. However, only U. minax of all the North American fiddler crabs exhibits the classical disjunct Carolinian distribution, and this appears basically to reflect the discontinuous distribution of temperate salt marshes that are the habitat of the species. Distributions of species belonging to subgenus Celuca adhere for the most part to the subdivision of the Gulf into western terrigenous and eastern carbonate sedimentary provinces. The northern transition occurs in the vicinity of Apalachee Bay and the southern at Laguna de Terminos. A third distributional pattern is shown by U. subcylindrica , a specialized endemic species of the hypersaline Laguna Madre system of the western Gulf. The level of endemism in the fiddler crabs is relatively high in comparison with that of other marine groups within the Gulf of Mexico. This may be a consequence of the adaptations of fiddler crabs as specialized deposit feeders to regional differences in climatic and edaphic characteristics of a marginally marine upper shore habitat. The distributional patterns of the endemics could prove useful in reconstructing palaeoecological events of evolutionary significance within the Gulf of Mexico.     

Durophagous predation on scaphitid ammonoids in the Late Cretaceous Western Interior Seaway of North America

This study is the first to report a trend of predation intensity on scaphitid ammonoids from the Turonian to the Maastrichtian (Late Cretaceous) on the basis of analysis of ventral shell breakage in large samples from the US Western Interior Province. Analysis of 835 adult specimens revealed ventral shell breakage in 50 specimens. In most of the damaged specimens, the breakage occurred in a preferred position at the rear part of the body chamber. Ventral breakage is rare in the Turonian specimens, whereas it is common in the Campanian and Maastrichtian specimens. The shell diameter of adult scaphitid ammonoids tends to increase with time. The position of the breakage and the absence of repairs indicate that the ventral breakage resulted from lethal predation. Based on the incidence of breakage and the size and shape of the breaks, possible predators include fish, reptiles and cephalopods such as Placenticeras, Eutrephoceras and coleoids. Our statistical analysis of ventral shell breakage indicates that the incidence of lethal predation increased in conjunction with an increase in adult shell size, suggesting that the body size of the prey was an important factor in predator–prey interactions. In addition, the predatory damage is more extensive in larger adults.     

Exploring the potential of food forestry to assist in ecological restoration in North America and beyond

Food forests—edible, perennial, polyculture systems—are of increasing interest in North America and the United Kingdom, as reflected in projects ranging from urban food initiatives to integrated conservation and restoration planning. To examine emerging food forestry (FF) against the backdrop of ecological restoration (ER), we conducted semi‐structured interviews with eight experts each from the fields of FF and ER in conjunction with observations of food forests in Canada, the United States, and the United Kingdom. Using content analysis, our study builds a FF model that encompasses the underlying goals of emerging FF—forest function; diversity of yields; education and culture sharing; healthy habitats for people and other species; and sustainability. We argue that FF has potential as an urban restoration tool in terms of enhancing the multifunctionality of heterogeneous landscapes undergoing significant changes. This will require meaningful consideration of ethical issues (e.g. commodification of nature), landscape contexts, ecological integrity, integration of historical knowledge, and resilience for interdependent, dynamic social and ecological systems. Moreover, systematic, long‐term monitoring of different types of food forests will be crucial in order to mindfully apply FF in ER. This research provides one of the first in‐depth analyses of how emerging FF might contribute to restoration in the time of the Anthropocene, especially outside traditional tropic regions where most FF has been practiced.     

The Aristida pansa complex and a key to the Divaricatae group of North America (Gramineae: Aristideae)

Variation in lateral awn length and pulvini development is described for A. pansa and A. gypsophila. The two species are distinguished by lateral awn development. Within each species, forms are based on pulvini development. Three new forms are described (A. pansa f. contracta; A. gypsophila f. gypsophiloides and f. diffusa), A. dissita is reduced to a form of A. pansa, and A. tehuacanensis is considered synonymous with A. pansa f. dissita. Keys, illustrations, and maps are provided.     

Predicting the distribution of Sasquatch in western North America: anything goes with ecological niche modelling

The availability of user-friendly software and publicly available biodiversity databases has led to a rapid increase in the use of ecological niche modelling to predict species distributions. A potential source of error in publicly available data that may affect the accuracy of ecological niche models (ENMs), and one that is difficult to correct for, is incorrect (or incomplete) taxonomy. Here we remind researchers of the need for careful evaluation of database records prior to use in modelling, especially when the presence of cryptic species is suspected or many records are based on indirect evidence. To draw attention to this potential problem, we construct ENMs for the North American Sasquatch (i.e. Bigfoot). Specifically, we use a large database of georeferenced putative sightings and footprints for Sasquatch in western North America, demonstrating how convincing environmentally predicted distributions of a taxon's potential range can be generated from questionable site-occurrence data. We compare the distribution of Bigfoot with an ENM for the black bear, Ursus americanus , and suggest that many sightings of this cryptozoid may be cases of mistaken identity.     

Potential Changes in the Distributions of Western North America Tree and Shrub Taxa under Future Climate Scenarios

Increases in atmospheric greenhouse gases are driving significant changes in global climate. To project potential vegetation response to future climate change, this study uses response surfaces to describe the relationship between bioclimatic variables and the distribution of tree and shrub taxa in western North America. The response surfaces illustrate the probability of the occurrence of a taxon at particular points in climate space. Climate space was defined using three bioclimatic variables: mean temperature of the coldest month, growing degree days, and a moisture index. Species distributions were simulated under present climate using observed data (1951–80, 30-year mean) and under future climate (2090–99, 10-year mean) using scenarios generated by three general circulation models—HADCM2, CGCM1, and CSIRO. The scenarios assume a 1% per year compound increase in greenhouse gases and changes in sulfate (SO₄) aerosols based on the Intergovernmental Panel on Climate Change (IPCC) IS92a scenario. The results indicate that under future climate conditions, potential range changes could be large for many tree and shrub taxa. Shifts in the potential ranges of species are simulated to occur not only northward but in all directions, including southward of the existing ranges of certain species. The simulated potential distributions of some species become increasingly fragmented under the future climate scenarios, while the simulated potential distributions of other species expand. The magnitudes of the simulated range changes imply significant impacts to ecosystems and shifts in patterns of species diversity in western North America. Received 12 May 2000; accepted 20 December 2000.