Geomorphological method in the elaboration of hazard maps for flash-floods in the municipality of Jucuarán (El Salvador)

This work deals with the elaboration of flood hazard maps. These maps reflect the areas prone to floods based on the effects of Hurricane Mitch in the Municipality of Jucuarán of El Salvador. Stream channels located in the coastal range in the SE of El Salvador flow into the Pacific Ocean and generate alluvial fans. Communities often inhabit these fans can be affected by floods. The geomorphology of these stream basins is associated with small areas, steep slopes, well developed regolite and extensive deforestation. These features play a key role in the generation of flash-floods. This zone lacks comprehensive rainfall data and gauging stations. The most detailed topographic maps are on a scale of 1:25 000. Given that the scale was not sufficiently detailed, we used aerial photographs enlarged to the scale of 1:8000. The effects of Hurricane Mitch mapped on these photographs were regarded as the reference event. Flood maps have a dual purpose (1) community emergency plans, (2) regional land use planning carried out by local authorities. The geomorphological method is based on mapping the geomorphological evidence (alluvial fans, preferential stream channels, erosion and sedimentation, man-made terraces). Following the interpretation of the photographs this information was validated on the field and complemented by eyewitness reports such as the height of water and flow typology. In addition, community workshops were organized to obtain information about the evolution and the impact of the phenomena. The superimposition of this information enables us to obtain a comprehensive geomorphological map. Another aim of the study was the calculation of the peak discharge using the Manning and the paleohydraulic methods and estimates based on geomorphologic criterion. The results were compared with those obtained using the rational method. Significant differences in the order of magnitude of the calculated discharges were noted. The rational method underestimated the results owing to short and discontinuous periods of rainfall data with the result that probabilistic equations cannot be applied. The Manning method yields a wide range of results because of its dependence on the roughness coefficient. The paleohydraulic method yielded higher values than the rational and Manning methods. However, it should be pointed out that it is possible that bigger boulders could have been moved had they existed. These discharge values are lower than those obtained by the geomorphological estimates, i.e. much closer to reality. The flood hazard maps were derived from the comprehensive geomorphological map. Three categories of hazard were established (very high, high and moderate) using flood energy, water height and velocity flow deduced from geomorphological and eyewitness reports.

Pseudo-two-girdles c-axis fabric patterns in a quartz-feldspar mylonite (Costabona granodiorite, Canigo massif)

An example of the relationship that exist between the preferred crystaliografic orientation of quartz grains and the attitude of the mylonite foliation of quartz-feldspar mylonites is described. These rocks are the result of the inhomogeneous deformation under low-grade metamorphic conditions of a late Hercynian granodiorite, intruded into the gneisses of the slopes of the Canig massif (Eastern Pyrenees). The Costabona mylonites have a quartz c-axis fabric in pseudo-twogirdles symmetrical with respect to the mylonite foliation and perpendicular to the shearband systems which produce an extensional crenulation of the mylonite foliation.

Interés florístico y geobotánico de la Sierra de Alcubierre (Monegros, Aragón)

sum tini Molero, Sáez and Villar-, altered by the presence of certain thermophilous coastal species, and finicolous and residual in character, are found in a few exceptional enclaves. Finally, stress is laid on the need to introduce suitable measures for the protection of certain places in the Range, particularly the residual woods of the northern slopes, in view of the exceptional interest of the flora and landscape. Key words: Flora, Vegetation, Chorology, Cormophytes, Sierra de Alcubierre, Monegros, Ebro valley, Spain.

Stratigraphie, morphodynamique, paléoenvironnements des terrains sédimentaires meubles à forte déclivité du domaine périglaciaire alpin

Dans le contexte d'un climat de plus en plus chaud, une étude « géosystémique » de la répartition du pergélisol dans l'ensemble d'un versant périglaciaire alpin, de la paroi rocheuse jusqu'au glacier rocheux, s'avère primordiale. S'insérant dans cette problématique, ce travail de thèse vise comme objectif général l'étude des versants d'éboulis situés à l'intérieur de la ceinture du pergélisol discontinu selon deux volets de recherche différents : une étude de la stratigraphie et de la répartition du pergélisol dans les éboulis de haute altitude et des processus qui lui sont associés ; une reconstitution de l'histoire paléoenvironnementale du domaine périglaciaire alpin pendant le Tardiglaciaire et l'Holocène. La stratigraphie et la répartition spatiale du pergélisol a été étudiée dans cinq éboulis des Alpes Valaisannes (Suisse), dont trois ont fait l'objet de forages profonds, grâce à la prospection géophysique de détail effectuée à l'aide de méthodes thermiques, de résistivité, sismiques et nucléaires. Les mesures effectuées ont permis de mettre en évidence que, dans les cinq éboulis étudiés, la répartition du pergélisol est discontinue et aucun des versants n'est intégralement occupé par du pergélisol. En particulier, il a été possible de prouver de manière directe que, dans un éboulis, le pergélisol est présent dans les parties inférieures du versant et absent dans les parties supérieures. Trois facteurs de contrôle principaux de la répartition du pergélisol déterminée au sein des éboulis étudiés ont été individualisés, pouvant agir seuls ou de manière combinée : la ventilation ascendante, l'augmentation de la granulométrie en direction de l'aval et la redistribution de la neige par le vent et les avalanches. Parmi ceux-ci, la relation ventilation-granulométrie semble être le facteur de contrôle principal permettant d'expliquer la présence de pergélisol dans les parties inférieures d'un éboulis et son absence dans les parties supérieures. Enfin, l'analyse de la structure des éboulis périglaciaires de haute altitude a permis de montrer que la stratigraphie du pergélisol peut être un élément important pour l'interprétation de la signification paléoclimatique de ce type de formes. Pour le deuxième volet de la recherche, grâce aux datations relatives effectuées à l'aide de l'utilisation conjointe de la méthode paléogéographique et du marteau de Schmidt, il a été possible de définir la chrono-stratigraphie du retrait glaciaire et du développement des glaciers rocheux et des versants d'éboulis des quatre régions des Alpes suisses étudiées (régions du Mont Gelé - Mont Fort, des Fontanesses et de Chamosentse, dans les Alpes Valaisannes, et Massif de la Cima di Gana Bianca, dans les Alpes Tessinoises). La compilation de toutes les datations effectuées a permis de montrer que la plupart des glaciers rocheux actifs étudiés se seraient développés soit juste avant et/ou pendant l'Optimum Climatique Holocène de 9.5-6.3 ka cal BP, soit au plus tard juste après cet évènement climatique majeur du dernier interglaciaire. Parmi les glaciers rocheux fossiles datés, la plupart aurait commencé à se former dans la deuxième moitié du Tardiglaciaire et se serait inactivé dans la première partie de l'Optimum Climatique Holocène. Pour les éboulis étudiés, les datations effectuées ont permis d'observer que leur surface date de la période entre le Boréal et l'Atlantique récent, indiquant que les taux d'éboulisation après la fin de l'Optimum Climatique Holocène ont dû être faibles, et que l'intervalle entre l'âge maximal et l'âge minimal est dans la plupart des cas relativement court (4-6 millénaires), indiquant que les taux d'éboulisation durant la période de formation des éboulis ont dû être importants. Grâce au calcul des taux d'érosion des parois rocheuses sur la base du volume de matériaux rocheux pour quatre des éboulis étudiés, il a été possible mettre en évidence l'existence d'une « éboulisation parapériglaciaire » liée à la dégradation du pergélisol dans les parois rocheuses, fonctionnant principalement durant les périodes de réchauffement climatique rapide comme cela a été le cas au début du Bølling, du Préboréal à la fin de l'Atlantique récent et, peut-être, à partir des années 1980. - In the context of a warmer climate, a « geosystemical » study of the permafrost distribution in a whole alpine periglacial hillslope, from the rockwall to the rockglacier, is of great importance. With respect to this problem, the general objective of this PhD thesis is the global study of talus slopes located within the alpine periglacial belt following two different research axes: the analysis of the internal structure and of the permafrost distribution of high altitude talus slopes and of the related processes; the reconstruction of the palaeoenvironmental history of the alpine periglacial belt during the Lateglacial and the Holocene. The stratigraphy and the permafrost distribution were studied in five talus slopes of the Valais Alps (Switzerland) with the analysis of borehole data (on three of the five talus slopes) and other methods of permafrost prospecting: Electrical Resistivity Tomography (ERT), Refraction Seismic Tomography (RST) and nuclear well logging. The collected data shows that, in all of the studied talus slopes, permafrost distribution is discontinuous and that neither of the hillslopes is integrally characterised by permafrost. In particular, this data proves by direct investigations that, in talus slopes, permafrost is present in the lower parts of the hillslope, whereas it is absent in the upper parts. Permafrost distribution in alpine talus slopes is depending of the combination of almost three controlling factors, whose respective importance is variable: the chimney effect, the increase of grain size downslope and the redistribution of snow by avalanches. Depending on the size of the talus and on topographical and geomorphological heterogeneities, various cases are possible: one dominant controlling factor or the combination of various factors. Nevertheless, it would be an error to consider each controlling factor independently, without considering their relationships. Between these controlling factors, the relationship chimney effect/grain size seems to be the most important factor controlling the presence of permafrost in the lowest part of periglacial talus slopes, and its absence in the upper parts. Finally, the analysis of the talus structure shows that the permafrost stratigraphy may be an important element of interpretation of the palaeoclimatic significance of an alpine talus slope. The second research axe focused on the establishment of a chronology of the Lateglacial glacier retreat and the dating of rockglaciers and talus slopes development in four studied regions of the Swiss Alps (Mont Gelé - Mont Fort, Fontanesses and Chamosentse regions, in the Valais Alps, and the Cima di Gana Bianca Massif, in the Ticino Alps). The compilation of the dates acquired through the combination of the palaeogeographical method and of the Schmidt hammer indicates that most of the investigated active rockglaciers started to evolve during the early phases of the Holocene or, at the latest, after the early-to-mid Holocene Climatic Optimum (ending around 6.3 ka cal BP). For the dated relict rockglaciers, most of them started to evolve in the second half of the Lateglacial, and probably became inactive at the beginning of the Holocene Climatic Optimum. For the investigated talus slopes, the relative dating carried out allowed to show that their surface date from the period included between the Boreal and the end of the Atlantic, pointing out that the rockwall retreat after the end of the Holocene Climatic Optimum was weak, and that the interval between maximal and minimal ages is in most cases relatively short (4-6 millennia). Therefore, the rockwall retreat during the development period of the talus slopes must has been considerable. Thanks to the calculation of rockwall erosion rates based on the volume of talus accumulations for four of the investigated hillslopes, it was possible to find evidences of the existence of "paraperiglacial rockfall phases" related to the permafrost degradation in rockwalls. These phases coincide with rapid climate warming periods, as at the beginning of the Bølling, during the Preboreal or, maybe, since 1980.

Las comunidades de líquenes de las rocas silíceas no volcánicas del SE de España

This study contains the results of a survey based on 200 relevés made, following the methodology of Klement (1955), in the provinces of Murcia, Almeria and Albacete, from the coast to 2000 msm, on siliceous rocks, mainly metamorphic schists and, more rarely, on quartzite. The climate is predominantly mediterranean and arid (from 180 to 500 mm of annual rainfall), and belongs to I11 and III(1V) types of Walter and Lieth, in the low regions, and to IV4 in the mountains. The coastal zone and also a lot of south-facing slopes enjoy fairly warm winters.

Innovative Solutions for Slope Stability Reinforcement and Characterization: Vol. I, TR-489, 2005

Soil slope instability concerning highway infrastructure is an ongoing problem in Iowa, as slope failures endanger public safety and continue to result in costly repair work. Characterization of slope failures is complicated, because the factors affecting slope stability can be difficult to discern and measure, particularly soil shear strength parameters. While in the past extensive research has been conducted on slope stability investigations and analysis, this research consists of field investigations addressing both the characterization and reinforcement of such slope failures. The current research focuses on applying an infrequently-used testing technique comprised of the Borehole Shear Test (BST). This in-situ test rapidly provides effective (i.e., drained) shear strength parameter values of soil. Using the BST device, fifteen Iowa slopes (fourteen failures and one proposed slope) were investigated and documented. Particular attention was paid to highly weathered shale and glacial till soil deposits, which have both been associated with slope failures in the southern Iowa drift region. Conventional laboratory tests including direct shear tests, triaxial compression tests, and ring shear tests were also performed on undisturbed and reconstituted soil samples to supplement BST results. The shear strength measurements were incorporated into complete evaluations of slope stability using both limit equilibrium and probabilistic analyses. The research methods and findings of these investigations are summarized in Volume 1 of this report. Research details of the independent characterization and reinforcement investigations are provided in Volumes 2 and 3, respectively. Combined, the field investigations offer guidance on identifying the factors that affect slope stability at a particular location and also on designing slope reinforcement using pile elements for cases where remedial measures are necessary. The research findings are expected to benefit civil and geotechnical engineers of government transportation agencies, consultants, and contractors dealing with slope stability, slope remediation, and geotechnical testing in Iowa.

Innovative Solutions for Slope Stability Reinforcement and Characterization: Vol. II, TR-489, 2005

Soil slope instability concerning highway infrastructure is an ongoing problem in Iowa, as slope failures endanger public safety and continue to result in costly repair work. While in the past extensive research has been conducted on slope stability investigations and analysis, this current research study consists of field investigations addressing both the characterization and reinforcement of such slope failures. While Volume I summarizes the research methods and findings of this study, Volume II provides procedural details for incorporating an infrequently-used testing technique, borehole shear tests, into practice. Fifteen slopes along Iowa highways were investigated, including thirteen slides (failed slopes), one unfailed slope, and one proposed embankment slope (the Sugar Creek Project). The slopes are mainly comprised of either clay shale or glacial till, and are generally gentle and of small scale, with slope angle ranging from 11 deg to 23 deg and height ranging from 6 to 23 m. Extensive field investigations and laboratory tests were performed for each slope. Field investigations included survey of slope geometry, borehole drilling, soil sampling, in-situ Borehole Shear Testing (BST) and ground water table measurement. Laboratory investigations mainly comprised of ring shear tests, soil basic property tests (grain size analysis and Atterberg limits test), mineralogy analyses, soil classifications, and natural water contents and density measurements on the representative soil samples from each slope. Extensive direct shear tests and a few triaxial compression tests and unconfined compression tests were also performed on undisturbed soil samples for the Sugar Creek Project. Based on the results of field and lab investigations, slope stability analysis was performed on each of the slopes to determine the possible factors resulting in the slope failures or to evaluate the potential slope instabilities using limit equilibrium methods. Deterministic slope analyses were performed for all the slopes. Probabilistic slope analysis and sensitivity study were also performed for the slope of the Sugar Creek Project. Results indicate that while the in-situ test rapidly provides effective shear strength parameters of soils, some training may be required for effective and appropriate use of the BST. Also, it is primarily intended to test cohesive soils and can produce erroneous results in gravelly soils. Additionally, the quality of boreholes affects test results, and disturbance to borehole walls should be minimized before test performance. A final limitation of widespread borehole shear testing may be its limited availability, as only about four to six test devices are currently being used in Iowa. Based on the data gathered in the field testing, reinforcement investigations are continued in Volume III.

Innovative Solutions for Slope Stability Reinforcement and Characterization: Vol. III, TR-489, 2005

Soil slope instability concerning highway infrastructure is an ongoing problem in Iowa, as slope failures endanger public safety and continue to result in costly repair work. Volume I of this current study summarizes research methods and findings, while Volume II provides procedural details for incorporating into practice an infrequently-used testing technique–borehole shear tests. Volume III of this study of field investigation of fifteen slopes in Iowa demonstrates through further experimental testing how lateral forces develop along stabilizing piles to resist slope movements. Results establish the feasibility of an alternative stabilization approach utilizing small-diameter pile elements. Also, a step-by-step procedure that can be used by both state and county transportation agencies to design slope reinforcement using slender piles is documented. Initial evidence of the efficiency and cost-effectiveness of stabilizing nuisance slope failures with grouted micropiles is presented. Employment of the remediation alternative is deemed more appropriate for stabilizing shallow slope failures. Overall, work accomplished in this research study included completing a comprehensive literature review on the state of the knowledge of slope stability and slope stabilization, the preparation and performance of fourteen full-scale pile load tests, the analysis of load test results, and the documentation of a design methodology for implementing the technology into current practices of slope stabilization. Recommendations for further research include monitoring pilot studies of slope reinforcement with grouted micropiles, supplementary experimental studies, and advanced numerical studies.

Thermogravimetric Analysis of Carbonate Aggregate, HR-336, 1994

Research has shown that one of the major contributing factors in early joint deterioration of portland cement concrete (PCC) pavement is the quality of the coarse aggregate. Conventional physical and freeze/thaw tests are slow and not satisfactory in evaluating aggregate quality. In the last ten years the Iowa DOT has been evaluating X-ray analysis and other new technologies to predict aggregate durability in PCC pavement. The objective of this research is to evaluate thermogravimetric analysis (TGA) of carbonate aggregate. The TGA testing has been conducted with a TA 2950 Thermogravimetric Analyzer. The equipment is controlled by an IBM compatible computer. A "TA Hi-RES" (trademark) software package allows for rapid testing while retaining high resolution. The carbon dioxide is driven off the dolomite fraction between 705 deg C and 745 deg C and off the calcite fraction between 905 deg C and 940 deg C. The graphical plot of the temperature and weight loss using the same sample size and test procedure demonstrates that the test is very accurate and repeatable. A substantial number of both dolomites and limestones (calcites) have been subjected to TGA testing. The slopes of the weight loss plot prior to the dolomite and calcite transitions does correlate with field performance. The noncarbonate fraction, which correlates to the acid insolubles, can be determined by TGA for most calcites and some dolomites. TGA has provided information that can be used to help predict the quality of carbonate aggregate.

Recycled Paper Erosion Control Mat, HR-349, 1994

The objective of this research project was to evaluate field application results and determine whether the Earth-Gard mat made from recycled material would successfully control erosion and allow vegetation to establish in ditch bottoms and steep slopes. The research would also help determine how steep a grade in the ditch bottoms can be protected from rill and gully erosion and how steep and long a backslope or foreslope can be protected from sheet and rill erosion by the recycled material and allow establishment of vegetation. The Earth-Gard gave satisfactory performance on areas with limited drainage and gradual slopes. Earth-Gard had a longevity of only six months. It was eroded away when used on areas with greater flow or steeper slopes.

Regional Approach to Landslide Interpretation and Repair, TR-430, 2001

The objective of this report is to provide Iowa county engineers and highway maintenance personnel with procedures that will allow them to efficiently and effectively interpret and repair or avoid landslides. The research provides an overview of basic slope stability analyses that can be used to diagnose the cause and effect associated with a slope failure. Field evidence for identifying active or potential slope stability problems is outlined. A survey of county engineers provided data for presenting a slope stability risk map for the state of Iowa. Areas of high risk are along the western border and southeastern portion of the state. These regions contain deep to moderately deep loess. The central portion of the state is a low risk area where the surficial soils are glacial till or thin loess over till. In this region, the landslides appear to occur predominately in backslopes along deeply incised major rivers, such as the Des Moines River, or in foreslopes. The south-central portion of the state is an area of medium risk where failures are associated with steep backslopes and improperly compacted foreslopes. Soil shear strength data compiled from the Iowa DOT and consulting engineers files are correlated with geologic parent materials and mean values of shear strength parameters and unit weights were computed for glacial till, friable loess, plastic loess and local alluvium. Statistical tests demonstrate that friction angles and unit weights differ significantly but in some cases effective stress cohesion intercept and undrained shear strength data do not. Moreover, effective stress cohesion intercept and undrained shear strength data show a high degree of variability. The shear strength and unit weight data are used in slope stability analyses for both drained and undrained conditions to generate curves that can be used for a preliminary evaluation of the relative stability of slopes within the four materials. Reconnaissance trips to over fifty active and repaired landslides in Iowa suggest that, in general, landslides in Iowa are relatively shallow [i.e., failure surfaces less than 6 ft (2 m) deep] and are either translational or shallow rational. Two foreslope and two backslope failure case histories provide additional insights into slope stability problems and repair in Iowa. These include the observation that embankment soils compacted to less than 95% relative density show a marked strength decrease from soils at or above that density. Foreslopes constructed of soils derived from shale exhibit loss of strength as a result of weathering. In some situations, multiple causes of instability can be discerned from back analyses with the slope stability program XSTABL. In areas where the stratigraphy consists of loess over till or till over bedrock, the geologic contracts act as surfaces of groundwater accumulation that contribute to slope instability.

Modelling hydrodynamics in the Rio Parana, Argentina : an evaluation and inter-comparison of reduced-complexity and physics based models applied to a large sand-bed river

Depth-averaged velocities and unit discharges within a 30 km reach of one of the world's largest rivers, the Rio Parana, Argentina, were simulated using three hydrodynamic models with different process representations: a reduced complexity (RC) model that neglects most of the physics governing fluid flow, a two-dimensional model based on the shallow water equations, and a three-dimensional model based on the Reynolds-averaged Navier-Stokes equations. Row characteristics simulated using all three models were compared with data obtained by acoustic Doppler current profiler surveys at four cross sections within the study reach. This analysis demonstrates that, surprisingly, the performance of the RC model is generally equal to, and in some instances better than, that of the physics based models in terms of the statistical agreement between simulated and measured flow properties. In addition, in contrast to previous applications of RC models, the present study demonstrates that the RC model can successfully predict measured flow velocities. The strong performance of the RC model reflects, in part, the simplicity of the depth-averaged mean flow patterns within the study reach and the dominant role of channel-scale topographic features in controlling the flow dynamics. Moreover, the very low water surface slopes that typify large sand-bed rivers enable flow depths to be estimated reliably in the RC model using a simple fixed-lid planar water surface approximation. This approach overcomes a major problem encountered in the application of RC models in environments characterised by shallow flows and steep bed gradients. The RC model is four orders of magnitude faster than the physics based models when performing steady-state hydrodynamic calculations. However, the iterative nature of the RC model calculations implies a reduction in computational efficiency relative to some other RC models. A further implication of this is that, if used to simulate channel morphodynamics, the present RC model may offer only a marginal advantage in terms of computational efficiency over approaches based on the shallow water equations. These observations illustrate the trade off between model realism and efficiency that is a key consideration in RC modelling. Moreover, this outcome highlights a need to rethink the use of RC morphodynamic models in fluvial geomorphology and to move away from existing grid-based approaches, such as the popular cellular automata (CA) models, that remain essentially reductionist in nature. In the case of the world's largest sand-bed rivers, this might be achieved by implementing the RC model outlined here as one element within a hierarchical modelling framework that would enable computationally efficient simulation of the morphodynamics of large rivers over millennial time scales. (C) 2012 Elsevier B.V. All rights reserved.

Contrasting diffusion of Quaternary gene pools across Europe: the case of the arctic-alpine Gentiana nivalis L. (Gentianaceae).

The fate of European arctic-alpine species during Pleistocene climatic oscillations still remains debated. Did these cold-adapted species invade much of the continental steppe or did they remain restricted to warmer slopes of inner mountain massifs? To examine this question, we investigated the phylogeography of Gentiana nivalis, a typical European arctic-alpine plant species. Genome fingerprinting analyses revealed that four genetic pools are actually unevenly distributed across the continent. One cluster covers almost all mountain massifs as well as northern areas, and thus coincides with a scenario of past distribution covering a large part of the European glacial steppe. In contrast, the three other lineages are strongly restricted spatially to western, central, and eastern Alps, respectively, thus arguing towards a scenario of in situ glacial survival. The coexistence of lineages with such contrasting demographic histories in Europe challenges our classical view of refugia and corroborates several hypotheses of biogeographers from the twentieth century.

Evaluation of Crushed Limestone Rock as a Mulch Material, HR-171, 1975

Earthen fills and back slopes resulting from highway building and other construction projects pose problems with respect to erosion stabilization and establishing vegetation cover. Sediments from such slopes create stream pollution while the erosion itself results in maintenance problems. Furthermore, adverse conditions aggravated by erosion prevent satisfactory establishing of vegetative cover. A dense vegetative cover is very effective in controlling erosion but even with optimum weather and soil conditions there is a delay of about 10 weeks between seeding and the establishment of a vegetative cover. Under actual field conditions, 3 months to a year may elapse between completion of construction and establishment of a vegetative cover. A research project was initiated early in 1974 to determine the effectiveness of a rock mulch of crushed limestone aggregates in controlling soil losses on highway construction back slopes in Iowa and to find the influence of such treatments on stand establishment of grasses and legumes.

Taxonomic status of Hylomys parvus and Hylomys suillus (Insectivora: Erinaceidae): biochemical and morphological analyses

The genus Hylomys was thought to be represented by a single widespread species. Biochemical and morphometric analyses of several Southeast Asian populations reveal that Sumatra is inhabited by two distinct species, the dwarf gymnure (H. parvus) and the lesser gymnure (H. suillus). The absence of interbreeding between these two groups along with their relatively ancient common origins are documented by several diagnostic loci and a large Nei's genetic distance (D = 0.353 +/- 0.035). The dwarf gymnure has been reported only from the slopes of the Mt. Kerinci volcano in Sumatra, where the species lives at higher elevations than its potential competitor, the lesser gymnure. Other populations of Hylomys from Java, Borneo, and Malaysia are more closely related to the Sumatran sample of H. suillus, but they exhibit strong interpopulational genetic differentiation (D = 0.165 +/- 0.040) that may be accounted for by their isolated montane habitat. In addition, a principal-components analysis based on 16 measurements of the skull clearly separates adult specimens of both species. There is little overlap in the measurements between H. suillus (which is larger) and H. parvus. On Sumatra where both species may be sympatric, the notched space between premaxillary tips, soft texture of the fur, and more delicate skull and dentition are diagnostic of H. parvus.