Role Of Rivers Research Articles

The roles of rivers and Pleistocene refugia in shaping genetic diversity in Praomys misonnei in tropical Africa

Aim This study aims to elucidate the phylogeography of the murid rodent Praomys misonnei and to document whether or not rain forest refugia and rivers structure patterns of diversity within this species. Location Tropical Africa, from Ghana to Kenya. Methods Patterns of genetic structure and signatures of population history (cytochrome b gene) were assessed in a survey of 229 individuals from 54 localities. Using maximum likelihood, Bayesian, network and genetic structure analyses, we inferred intra-specific relationships and tested hypotheses for historical patterns of gene flow within P. misonnei. Results Our phylogenetic analyses reveal a strong phylogeographical structure. We identified four major geographical clades within P. misonnei: one clade in Ghana and Benin, a Nigerian clade, a West Central African clade and a Central and East African clade. Several subclades were identified within these four major clades. A signal of population expansion was detected in most clades or subclades. Coalescence within all of the major clades of P. misonnei occurred during the Middle Pleistocene and/or the beginning of Late Pleistocene. Main conclusions Our results suggest a role for both Pleistocene refugia and rivers in structuring genetic diversity in P. misonnei. This forest-dwelling rodent may have been isolated in a number of forest fragments during arid periods and expanded its range during wetter periods. Potential forest refugia may have been localized in Benin-Ghana, south-western Cameroon, southern Gabon, northern Gabon and eastern Democratic Republic of Congo-western Uganda. The Niger and/or the Cross Rivers, the Oubangui-Congo, Sanaga, Ogooue and/or Ivindo Rivers probably stopped the re-expansion of the species from relict areas.

Mitochondrial DNA and morphometrical identification of a new species of Hylomyscus (Rodentia: Muridae) from West Africa

In this paper we describe a new species of Hylomyscus based on molecular (Cyt b and 16S rDNA gene sequencing) and morphometrical analyses. This new species occurs in Benin and Nigeria, and probably also in Togo. It differs by 8.29 to 10.40 % of sequence divergence (K2P distance for the Cyt b gene) from all other species of the H. alleni species complex, and can be distinguished from these species through morphometrical multivariate analyses. It differs significantly from its closest relative, H. simus, by four external and nine cranio-dental measurements. The role of rivers and Pleistocene forest refugia in the diversification of the H. alleni species complex is discussed.

Phylogeny and species boundaries of the endemic species complex, Eliurus antsingy and E. carletoni (Rodentia: Muroidea: Nesomyidae), in Madagascar using mitochondrial and nuclear DNA sequence data

Current understanding of the taxonomy and species relationships within the genus Eliurus, a member of the endemic Malagasy rodent subfamily Nesomyinae, is largely based on morphological characters. Little has been published about the historical biogeography and diversification factors in members of this genus. Here we examined, using molecular data, the evolutionary relationships, and species boundaries within a species complex of Eliurus and the role of rivers in their evolution. Specifically, we tested the hypothesized monophyly of E. antsingy (west) and the recently described E. carletoni (north) using two mitochondrial genes, cytochrome b, the control region, and a nuclear marker, the Interstitial Retinol Binding Protein (IRBP). We also assessed the species boundaries of E. carletoni and examined phylogeographic patterns using two mitochondrial markers and an extensive geographic sampling. Molecular data show that members of the E. antsingy and E. carletoni complex together form a monophyletic group. Although samples provisionally assigned to E. carletoni based on morphological characters from different sites in northern Madagascar cluster in three separate phylogroups, they are monophyletic and assignable to this species. Rivers do not act as strict barriers to dispersal in E. carletoni. The demonstrated monophyly of both E. antsingy and E. carletoni contributes to the amounting evidence for a biogeographic link between the north and western regions of the island.

Role of rivers in the seasonal variations of terrestrial water storage over global basins

The role of rivers in total terrestrial water storage (TWS) variations is evaluated in 29 basins. The contribution of individual storage components to total TWS is investigated by using ensemble hydrological simulations with river routing. The observed Gravity Recovery And Climate Experiment (GRACE) TWS data are used to validate model simulations. It is found TWS simulations are more accurate when river storage is taken into account except for dry basins. Rivers play different roles in various climatic regions as indicated by two new indices quantifying the significance of each TWS component and their interactions. River storage, which effectively includes downslope movement of shallow groundwater, explains up to 73% of TWS variations in Amazon. It also acts as “buffer” which smoothes TWS seasonal variations particularly in snow‐dominated basins. Neglecting river storage may lead to mismatch in the amplitude and phase of TWS seasonal variations compared to the GRACE observations.

Calcareous nannofossil surface sediment assemblages from the Sicily Channel (central Mediterranean Sea): Palaeoceanographic implications

Quantitative analysis of 67 calcareous nannofossil assemblages from surface sediments recovered in a wide area across the Sicily Channel has been carried out in order to improve the interpretation of palaeontological data based on this planktonic group in a key area for Mediterranean palaeoceanographic studies. The investigation focused on three case studies that demonstrate the high potentiality of such a combined approach, taking into account the recent distribution of taxa or groups of taxa on the sea floor and the palaeontological record. The distribution of reworked specimens over the northern Sicily Channel sea floor validates the role of southern Sicily as a source region for reworked nannofossils and the role of rivers as their carrier. Eustatic sea-level fluctuations can be considered to be the main factor that influenced the abundance variations in sedimentary sequences of this area. The distribution of Florisphaera profunda can be explained in terms of topography (positive correlation) and mesoscale oceanographic circulation. In particular, its significant anti-correlation to the amount of chlorophyll-A deduced by satellite imagery validates the use of this species as a proxy for palaeoproductivity reconstructions. Finally, high abundance values of G. oceanica are confined to the westernmost part of the Sicily Channel, coinciding with a water mass salinity minimum. In particular, abundances of up to about 10% were observed in the westernmost part of the African Margin, suggesting the importance of the Atlantic Tunisian Current, whose activity is more pronounced in winter. The comparison of data of this species between 135 and 110 kyr BP, inside and outside the Channel, led us to deduce that the physical transport in almost unmodified waters of Atlantic origin might be the most important factor for its significant occurrence.

The role of Pleistocene refugia and rivers in shaping gorilla genetic diversity in central Africa.

The role of Pleistocene forest refugia and rivers in the evolutionary diversification of tropical biota has been the subject of considerable debate. A range-wide analysis of gorilla mitochondrial and nuclear variation was used to test the potential role of both refugia and rivers in shaping genetic diversity in current populations. Results reveal strong patterns of regional differentiation that are consistent with refugial hypotheses for central Africa. Four major mitochondrial haplogroups are evident with the greatest divergence between eastern (A, B) and western (C, D) gorillas. Coalescent simulations reject a model of recent east-west separation during the last glacial maximum but are consistent with a divergence time within the Pleistocene. Microsatellite data also support a similar regional pattern of population genetic structure. Signatures of demographic expansion were detected in eastern lowland (B) and Gabon/Congo (D3) mitochondrial haplogroups and are consistent with a history of postglacial expansion from formerly isolated refugia. Although most mitochondrial haplogroups are regionally defined, limited admixture is evident between neighboring haplogroups. Mantel tests reveal a significant isolation-by-distance effect among western lowland gorilla populations. However, mitochondrial genetic distances also correlate with the distance required to circumnavigate intervening rivers, indicating a possible role for rivers in partitioning gorilla genetic diversity. Comparative data are needed to evaluate the importance of both mechanisms of vicariance in other African rainforest taxa.

Charophyte communities in cut-off river channels: The role of connectivity

The role of river and groundwater connectivity on the diversity, distribution and temporal dynamics of charophytes has been determined in cut-off river channels of the Rhône, Rhine, Ain and Doubs. Charophyte richness and abundance decrease (from 12 species in cut-off channels of the Ain River to one species in the ones of the Doubs River) when nutrient contents increase (from [NH 4]=9×10 −3 mg l −1 and [PO 4]=0.05 mg l −1 in average in the Ain River to [NH 4]=0.1 mg l −1 and [PO 4]=0.34 mg l −1 in the Doubs River), but only species richness appeared to be significantly negatively correlated with water ammonium content. Chara major and Chara globularis occurred in cut-off channels characterized by low levels of flood disturbance, whereas some other species (e.g. Chara vulgaris and Nitella confervacea) were able to maintain their presence in cut-off channels frequently scoured by flood disturbance. The temporal dynamics of some species demonstrated their ability to survive over several years in habitats characterised either by low disturbance ( C. major, Chara hispida) or high disturbance levels ( C. vulgaris). In the latter case, the high variability of the species distribution over time suggested that its maintenance involved propagule dispersal, because its shallow anchorage did not prevent the plant being uprooted during floods. These results suggest that some charophyte species should not be considered as pioneer fugitive species ( C. major) because they are able to colonise undisturbed cut-off channels over more than 15 years. Others (e.g. Nitella sp.) could be, because of their limited distribution and high variations in abundance over time.

Wisconsin Land and Life

Rolling green hills dotted with Holstein cows, red barns, and blue silos. The Great Lakes ports at Superior, Ashland, and Kenosha. A Polish wedding dance or a German biergarten in Milwaukee. The dappled quiet of the Chequamagon forest. A weatherbeaten but tidy town hall at the intersection of two county trunk highways. Ojibwa families gathering wild rice into canoes. The boat ride through the Dells. The upland ridges of the Driftless Area, falling away into hidden valleys. . . . These are images of Wisconsin's land and life, images that evoke a strong sense of place. This book, Land and Life, is an exploration of place, a series of original essays by Wisconsin geographers that offers an introduction to the state's natural environment, the historical processes of its human habitation, and the ways that nature and people interact to create distinct regional landscapes. To read it is to come away with a sweeping view of Wisconsin's geography and history: the glaciers that carved lakes and moraines; the soils and climate that fostered the prairies and great northern pine forests; the early Native Americans who began to shape the landscape and who established forest trails and river portages; the successive waves of Europeans who came to trade in furs, mine for lead and iron, cut the white pines, establish farms, work in the lumber and paper mills, and transform spent wheatfields into pasture for dairy cattle. Readers will learn, too, about the platting and naming of Wisconsin's towns, the establishment of county and township governments, the growth of urban neighborhoods and parishes, the role of rivers, railroads, and religion in shaping the state's growth, and the controversial reforestation of the cutover lands that eventually transformed hardscrabble farms and swamps into a sportsman's paradise. Abundantly illustrated with photos and maps, this book will richly reward anyone who wishes to learn more about the land and life of the place we know as Wisconsin.

Preliminary results on the role of rivers in total Hg concentrations in marine sediments and benthic organisms of a coastal area of Italy

The paper reports the results of mercury (Hg) concentrations in the <20 μm grain-size fraction of shallow sediments of the northern Tyrrhenian sea, collected near the mouths of rivers flowing down from the Monte Amiata area (central Italy), which is characterized by cinnabar mineralization which was developped as mercury mine in the past. A few species of benthic marine organisms collected in the sediment sampling area were also analyzed. From the results, it emerged that the rivers contribute to the Hg concentration in the marine sediments which already contain high natural Hg background levels. The benthic organisms, which reflect sediment contamination, showed high Hg concentrations as well.

Always a River: The Ohio River and the American Experience ed. by Robert L. Reid

TECHNOLOGY AND CULTURE Book Reviews 153 David Holly’s book concludes with seven appendixes, including specifications of each vessel in the Weems fleet, a representative sample of scheduling and board meeting minutes, construction agreements and costs, a Weems family history, and a comprehensive listing of river landings visited by Weems boats. Notes and a bibliog­ raphy round out the volume. It is, as the subtitle claims, truly “a saga of the Chesapeake,” although what is an otherwise splendid history suffers from a slight indulgence in nostalgia. (Almost as if in antici­ pation of such criticism, the author points out that “the steamboat era was inescapably romantic” [p. xvii].) It is interesting that Holly concludes that one of the contributing factors that led to the sale of the company in 1905 was the automobile. Company president Henry Williams had seen several autos on the streets of Baltimore, and a few had been carried as freight on Weems boats. From this and the increasing number of improved roads he “knew instinctively what the statistics portended” (p. 157). Perhaps so, but this conclusion sounds very much like late-20th-century hind­ sight. It does not equate with the author’s observation that “the period from 1905 to the 1920s marked the golden age of steamboating on the Chesapeake” (p. 182). This is a nicely done and carefully prepared book, a fine companion to Holly’s earlier Steamboat on the Chesapeake (Centreville, Md., 1987), the story of the Emma Giles and the Tolchester line. William Worthington Mr. Worthington is with the Division of Engineering and Industry at the National Museum of American History. Always a River: The Ohio River and the American Experience. Edited by Robert L. Reid. Bloomington: Indiana University Press, 1991. Pp. xvi+ 250; illustrations, notes. $35.00 (cloth); $12.95 (paper). The title of this volume implies continuity and may seem somewhat at odds with the editor’s central theme of regional change. Despite the apparent conflict, this is an unusually cohesive set of essays. Always a River was the name selected for the multistate humanities project that gave birth to the collection of seven essays and denotes the literary symbolism of rivers and the territorial unity fostered by the waterway. The theme of change, however, is true to the historic dynamism of both rivers and regions. Set within this contrasting framework, contributors from diverse backgrounds provide complementary per­ spectives on the role of human societies in settling and modifying the Ohio River valley. This book works because each author retains a sharp focus on the Ohio valley. Chapters deal with the role of rivers in human society, travelers’ perspectives on the valley, cultural landscapes, transporta­ 154 Book Reviews TECHNOLOGY AND CULTURE tion history, economic development, engineering works, and environ­ mental challenges. The Ohio River, as we are told repeatedly, was the principal axis for migration into the western territories, and its development followed improvements in transportation technology. Although similar dramas unfolded in other settings, the Ohio River experience perhaps exemplifies this progression more emphatically than other comparable valleys. The process of technological change is implicit rather than explicit in several chapters. Scott Sanders’s opening essay notes society’s abiding desire “for contact with untrammeled nature and at the same time longing for control” (p. 4). The human urge to dominate the Ohio valley is illustrated by travelers’ observations recorded at oppo­ site ends of the 19th century. John Jakle’s commentary reveals a pioneer’s active participation in the emerging transformation of the valley, while a scholar sought to find a garden untouched by the machine. Through their observations, as interpreted by Jakle, we see the emergence of landscapes of ruin as early as 1900. Technological change is more central to LelandJohnson’s review of navigational modifications on the Ohio River. He presents the river as an imperfect waterway in dire need of coordinated engineering. His essay contrasts the competing views of river users with the mandate of the army engineers and presents an unusually sympathetic view of the Corps of Engineers as agents of change. Johnson rightfully portrays the search for suitable wicket-dam technology as thoughtful manage­ ment, but he almost overlooks the environmental consequences of alterations...

The Horton River Breakthrough and Resulting Geomorphic Changes in a Permafrost Environment, Western Arctic Coast, Canada

Dendrochronological analysis and radiocarbon dating show that a breakthrough to the sea occurred along the lower course of the Horton River after 1640 AD. At the breakthrough site, the Horton River flowed 10 m above sea level so that river erosion and delta building would have been rapid. By 1826, when the coast was mapped by the expedition of Dr. John Richardson, the Horton Delta had a surface area of about 10 to 15 km2, approximately one third of the present area. Construction of the delta has protected the adjacent sea cliffs from wave erosion. Attention is paid to the nature of geomorphic change in a permafrost environment and the role of river and sea ice in affecting changes.

Seasonal aspects of the surface and advective heat fluxes of Kootenay Lake, British Columbia

A description is given of the heat and water balances of Kootenay Lake, British Columbia. Although the lake has a moderately high throughflow (781 m3 s−1), the heat budget is more in character with a lake that is little influenced by rivers. The discussion focuses upon the role of rivers in the thermal history of lakes; a contrast is drawn between Kootenay Lake and Kamloops Lake, British Columbia, a strongly riverine lake with a much greater heat budget. It is suggested that the riverine nature of lakes can be characterized using a renewal time that applies to that region of the lake lying above the base of the river plume. Furthermore, the relative roles of advective and surface effects can be qualitatively described using a ratio of surface buoyancy or wind energy to river production of turbulent energy. These parameterizations may prove to be useful descriptors in a lake classification system based upon riverine quality.

The Civilization Developed along Waters

In ancient societies seas and rivers played an important role in spreading of the civilizations. In Japan seas and oceans have remained important even until now. The role of rivers in Japan, however, was gradually changed to that in irrigation and drinking, and its industrial importance has now become recognized in modern ages.There are two reasons for rivers retreating from the means of spreading of the civilization.1) Basins formed by one river system became complete as the space of life but lost their integration that had existed by means of a river. This was brought about by the new method of reclamation that came from China: For the management of paddy-field with rivers being the source of water supply it was necessary for rivers to be divided into small parts one system by one system.2) By using new method of reclamation powerful families in the provinces developed the space of life. As a result consanguineal societies were changed into territorial societies. Overland routes took the place of waterways as means of contact among many territorial societies formed in one water system. And rivers lost their importance as traffic routes and became important as the source of water supply (water for irrigaition).The purpose of this article is to make clear the history of the roles of such river systems, taking an example from Sumiyoshi Shrine that used to possess a large ancient dominion on the Hyogo River. As Sumyoshi Shrine was a tutelary god, its domain was on the Bay of Osaka (that was) next to the Inland Sea of Seto. However, by forming a connection with the Imperial Court of Yamato the shrine widened its domain along the river system and gained a vast area including woods and river valley inland. Because it was not originally the god of agriculture or forestry, it began to draw back when it lost the protection of the Imperial Court of Yamato, and finally retreated to the sea-side place which it had first possessed. The shrines that lost even their first domains have maintained only the buildings in which the faith in the gods of navigation and diplomacy is slightly kept.