Intercemetery morphological variation in Arikara crania from the mobridge site (39WW1)

Multivariate analysis is used to examine intrasite variation in cranial morphology in the Mobridge Arikara skeletal collection. The site included three spatially distinct burial areas. The burial areas (features) are defined according to geographic location. Feature 1 is a small hill west of the village. Feature 2 is a large, long hill 200–300 yards south of the village. Feature 3 is a small knoll 100 yards south of Feature 1. The internal chronology of Mobridge has not been established with precision, but order has been postulated based on archeological data. Previous researchers have considered area 2 to be later than areas 1 and 3. Significant morphological heterogeneity exists between areas. Sample differences indicate that specific features were used by temporally distinct populations. The archaeologically proposed temporal ordering of the cemeteries is supported by osteological evidence.     

Long bone lengths and gestational age distributions of post-contact period Arikara Indian perinatal infant skeletons

Prenatal growth is adversely affected by poor socioeconomic conditions where disease and chronic undernutrition prevail. Premature and small-for-gestational-age births occur at higher frequency. Post-contact Arikara Indian populations of South Dakota experienced a rapidly changing and disruptive environment that included deterioration of the subsistence base and increased morbidity. This research tests resulting fetal growth effects through comparative analysis of two perinatal infant samples of the early (A.D. 1600-1733) and the late (A.D. 1760-1835) post-contact period. Perinatal infants recovered from late cemeteries include a higher percentage of smaller skeletons, as determined using long bone diaphyseal lengths, than is documented for the earlier time period. This contrast shows that it is possible to detect fetal growth differences in samples of archaeological context.     

Secular changes in craniofacial morphology of the Portuguese using geometric morphometrics

This study examines patterns of secular change in cranial morphology in the New Lisbon collection, a documented skeletal collection from Lisbon, Portugal with birth years from 1806 to 1954. This period represents a time when Lisbon was undergoing increased urbanization and population growth, as well as changes in mortality and fertility patterns. Previous studies from the U.S., Europe, and Japan have reported significant secular changes in cranial morphology over the past 200 years. In the current study, secular changes were analyzed using three-dimensional geometric morphometrics methods. The results from this study demonstrate a significant change in cranial morphology over the roughly 150-year period. Allometry was rejected as a causal factor of this change because there was no association found between temporal change and size. The pattern of temporal change is similar to that observed in other populations in the U.S., Europe, and Japan, including decreased facial breadth and a more inferiorly placed cranial base. This study, along with previous research, suggests a similar pattern of change occurs in genetically and geographically diverse populations experiencing modern environmental conditions. We argue that because the secular changes are focused in the cranial base, a region of the skull that experiences a relatively early growth curve, changes related to declines in childhood morbidity and mortality are likely important factors related to the observed changes.     

Finger dermatoglyphics of the Peruvian Cashinahua

The Peruvian Cashinahua are an isolate of unmixed American Indians living in four villages in the Southeastern part of the country. Finger dermatoglyphic data were collected from the three most closely grouped villages in the summer of 1966. The relatively low proportion of whorls and high proportion of arches, and the low values of pattern intensity (10.75) and total ridge count (89.14) contrasts markedly with other American Indian groups in general, and with Amazon Basin groups in particular. The distinctive finger print patterns may be explained by factors such as genetic drift and inbreeding, which can alter gene and phenotype frequencies in small populations.     

Effects of projected future urban land cover on nitrogen and phosphorus runoff to Chesapeake Bay

This paper examined the effects of simulated land cover/land use (LC/LU) change from 2000 to 2030 on nutrient loadings to the Chesapeake Bay. The SPAtially Referenced Regression On Watershed Attributes (SPARROW) model was used with anticipated watershed-wide LC/LU change from a growth forecast model that provides spatially explicit probabilities of conversion to impervious surface. The total nitrogen (TN) and total phosphorus (TP) loadings estimated to enter the Chesapeake Bay were reduced by 20% and 19%, respectively. In general, as development replaced other LC/LUs from 2000 to 2030, TN and TP runoff was significantly reduced by losses of non-point, non-urban source loadings, yields, and land-to-water delivery. The simulation results suggest future changes in landscape composition and configuration at catchment and riparian stream buffer width scales could lower TN and TP runoff to the estuary.     

Growth and reproductive cycle of the zebra mussel in the River Rhine as studied in a river bypass

In a Rhine River bypass built at a water pollution control station, the growth and reproductive cycle of the zebra mussel (Dreissena polymorpha) were studied over a period of nearly 3 years. The experimental setup offered the possibility to manipulate the temperature of the continuously passing river water and to calculate influences of temperature and food on the growth of individually marked mussels. Shell growth rates were a function of algal density (measured as chlorophyll a). This function followed saturation curves with temperature-dependent plateau levels, and saturation occurred at values above 40 μg/l chlorophyll a. The relationship between shell growth rate and temperature followed the courses of bell-shaped curves with algal-food-dependent heights. No clear correlations could be found between shell growth and other environmental factors such as dissolved organic matter, total organic content, seston, and turbidity. Two spawning periods per year characterized the reproductive cycle of the zebra mussels at the study site. The first one covered nearly 3 months (April to July) comprising several spawning events. The second shorter one occurred in August. Young mussels of the first spawning period settled at the end of May, and they were able to reproduce a few months later (end of August) when their shell length exceeded 9 mm. This first spawning period of the young-of-the-years coincided with the second spawning period of the older generations. Through the combined analysis of the results of both body weight determinations and shell growth experiments, it was possible to model mussel growth over a period of nearly 3 successive years, and to suggest the presence of an endogenous factor that might be involved in determining the start of the annual shell growth period. Received: 8 April 1997 / Accepted: 3 November 1997     

Anthropometric variation among Bering Sea natives

Recent research indicates that anthropometrics can be used to study microevolutionary forces acting on humans. We examine the use of morphological traits in reconstructing the population history of Aleuts and Eskimos of the Bering Sea. From 1979 to 1981, W. S. Laughlin measured a sample of St. Lawrence Island Eskimos and Pribilof Island Aleuts. These samples included adult participants from St. George and St. Paul in the Pribilof Islands and from Gambell and Savoonga on St. Lawrence Island. The Relethford-Blangero method was used to examine the phylogenetic relationship between Aleuts and Eskimos. Anthropometric measurements for Native North Americans (measured by Boas and a team of trained anthropometrists in 1890-1904) and Native Mesoamericans (compiled from the literature for 1898-1952) were used for comparison. A principal components analysis of means for measurements and a neighbor-joining tree were constructed using Euclidean distances. All these tests revealed the same strong relationship among the focus populations. The R matrix from the Relethford-Blangero method clusters Aleuts and Eskimos separately and accounts for 97.3% of the variation in the data. Phenotypic variation within the population is minimal and therefore minimum F(ST) values are low. Genetic distances were compared to a Euclidean distance matrix of anthropometric measurements using a Mantel test and gave a high but not significant correlation. Our results provide evidence of a close phylogenetic relationship between Aleut and Eskimo populations in the Bering Sea. However, it is apparent that history has affected the relationship among the populations. Despite previous findings of higher European admixture in Gambell (based on blood group markers) than in Savoonga, Savoonga has greater within-group variation in anthropometric measurements. Anthropometrics reveal a close relationship between Gambell and St. Paul as a result of European admixture. The St. George population was the most divergent of the populations, indicating that it diverged from the Eskimos and St. Paul because of the compounding effects of genetic drift and limited European gene flow. These findings are in agreement with previous anthropometric and genetic studies of the Aleut and Eskimo populations and support the utility of anthropometrics in inferring population history and structure.     

On testing the competition-colonization trade-off in a multispecies assemblage

The competition-colonization trade-off has long been considered an important mechanism explaining species coexistence in spatially structured environments, yet data supporting it remain ambiguous. Most competition-colonization research examines plants and the dispersal-linked traits of their seeds. However, colonization is more than just dispersal because rapid population growth is also an important component of colonization. We tested for the presence of competition-colonization trade-offs with a commonly used artificial assemblage consisting of protozoan and rotifer species, where colonization was the ability of a species to establish populations in patches. By ranking species according to their colonization abilities and their pairwise competitive interactions, we show that these species exhibit competition-colonization trade-offs. These results reveal that the competition-colonization trade-off exists within nonplant assemblages and that even in a laboratory setting, species are constrained to be either good competitors or colonizers but not both.