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Articles 1411 - 1440 of 1541

Full-Text Articles in Terrestrial and Aquatic Ecology

First Evidence Of Plague (Yersinia Pestis) In Nebraska Is Found In Panhandle Predators, Dallas Virchow, Wayne L. Kramer, Charles S. Brown, Scott E. Hygnstrom, Alan M. Barnes Jan 1992

First Evidence Of Plague (Yersinia Pestis) In Nebraska Is Found In Panhandle Predators, Dallas Virchow, Wayne L. Kramer, Charles S. Brown, Scott E. Hygnstrom, Alan M. Barnes

Transactions of the Nebraska Academy of Sciences and Affiliated Societies

In September, 1992, plague (Yersinia pestis) antibody was found in the blood of a coyote (Canis latrans) (1:128 titer) and a badger (Taxidea taxus) (1:2048 titer) taken near a suspect black-tailed prairie dog (Cynomys ludovicianus) town in Sioux County. However, a 1989-1991 survey of 96 coyotes taken from nine Nebraska Panhandle counties demonstrated no plague antibodies. Passive hemagglutination tests of Nobuto blood-sampling paper proved useful to quickly survey a predator population that is distributed across a broad geographic area.


Distributional Survey Of The Bird-Voiced Treefrog, Hyla Avivoca (Anura: Hylidae), In Arkansas, Stanley E. Trauth Jan 1992

Distributional Survey Of The Bird-Voiced Treefrog, Hyla Avivoca (Anura: Hylidae), In Arkansas, Stanley E. Trauth

Journal of the Arkansas Academy of Science

A field study of the bird-voiced treefrog, Hyla avivoca, was conducted in Arkansas during the summer of 1991. A total of 75 separate sites in 23 counties was visited. Males with their distinctive whistle-like calls were listened for at night at each site. Breeding colonies of Hyla avivoca were found in four of the six major river basins; the study established three new county records. Currently, this species has been documented at 14 sites in 10 counties; in very few situations were the treefrogs locally abundant (voucher specimens deposited in the Arkansas State University Museum of Zoology). Habitat perturbation and …


Age Specific Analysis Of Food Habits For Arkansas Raccoons (Procyon Lotor), J. D. Wilhide, V. Rick Mcdaniel, C. Renn Tumlison Jan 1992

Age Specific Analysis Of Food Habits For Arkansas Raccoons (Procyon Lotor), J. D. Wilhide, V. Rick Mcdaniel, C. Renn Tumlison

Journal of the Arkansas Academy of Science

No abstract provided.


Maternity Colony Of Gray Bats In A Non-Cave Site, Lorraine Timmerman, V. Rick Mcdaniel Jan 1992

Maternity Colony Of Gray Bats In A Non-Cave Site, Lorraine Timmerman, V. Rick Mcdaniel

Journal of the Arkansas Academy of Science

No abstract provided.


Population Dynamics Of Feral House Mice And Meadow Voles On A Dredge Disposal Site, Georgia E. Kratimenos Oct 1991

Population Dynamics Of Feral House Mice And Meadow Voles On A Dredge Disposal Site, Georgia E. Kratimenos

Biological Sciences Theses & Dissertations

The population dynamics of two species was studied for one year on Craney Island in Portsmouth, Virginia. This dredge disposal site provided good habitat for the house mouse, Mus musculus, whose opportunistic behaviors can withstand the sudden changes in a dynamic environment. Although the site was not optimal habitat, a population of Microtus pennsylvanicus, the meadow vole, was sustained there. Of the seven species of small mammals captured, 65% were house mice and 28% were meadow voles. Meadow voles were more successful at establishing short periods of residency than were house mice; on average, each meadow vole was …


The Identification, Distribution, And Status Of The Threatened Dismal Swamp Shrew (Sorex Longirostris Fisheri), Thomas M. Padgett Oct 1991

The Identification, Distribution, And Status Of The Threatened Dismal Swamp Shrew (Sorex Longirostris Fisheri), Thomas M. Padgett

Biological Sciences Theses & Dissertations

Southeastern shrews (Sorex longirostris) were trapped throughout southeastern Virginia and northeastern North Carolina to determine if any morphological characters could

be identified that would aid in the identification and distribution of the threatened subspecies Sorex l._ fisheri, endemic to the Great Dismal Swamp, the more upland nominate subspecies Sorex l. longirostris, and possible intergrades between the two subspecies. Animals were classified a priori into three groups, based on their location of capture. Animals collected from the Great Dismal Swamp National Wildlife Refuge (GDSNWR) and associated bottomland habitats were designated as "fisheri", animals collected farthest from the Swamp as "longirostris", and …


Phyletic Coevolution Between Subterranean Rodents Of The Genus Ctenomys (Rodentia: Hystricognathi) And Nematodes Of The Genus Paraspidodera (Heterakoidea: Aspidoderidae) In The Neotropics: Temporal And Evolutionary Implications, Scott Lyell Gardner May 1991

Phyletic Coevolution Between Subterranean Rodents Of The Genus Ctenomys (Rodentia: Hystricognathi) And Nematodes Of The Genus Paraspidodera (Heterakoidea: Aspidoderidae) In The Neotropics: Temporal And Evolutionary Implications, Scott Lyell Gardner

Harold W. Manter Laboratory of Parasitology: Faculty Publications

Coevolution was studied in six species of rodents of the genus Ctenomys and their parasitic nematodes of the genus Paraspidodera, collected in Bolivia. Representatives of the families Octodontidae and Caviidae were used as outgroups for the mammals, and nematodes from caviids were used as outgroups of the nematodes from ctenomyids. For the nematodes, quantitative and qualitative morphological characteristics of both males and females and electrophoretic characters of both sexes were used to generate phylogenetic hypotheses of evolutionary relationships of the OTUs occurring in hosts of different species. Concordance estimates of cladograms generated from biochemical-genetic and morphological data of the …


Description Of The Tadpoles Of Gastrophryne Pictiventris And Nelsonophryne Aterrima (Anura: Microhylidae), With A Review Of Morphological Variation In Free-Swimming Microhylid Larvae, Maureen A. Donnelly, Rafael O. De Sá, Craig Guyer Jun 1990

Description Of The Tadpoles Of Gastrophryne Pictiventris And Nelsonophryne Aterrima (Anura: Microhylidae), With A Review Of Morphological Variation In Free-Swimming Microhylid Larvae, Maureen A. Donnelly, Rafael O. De Sá, Craig Guyer

Biology Faculty Publications

The tadpoles of Gastrophryne pictiventris and Nelsonophryne aterrima are described based on material collected in Costa Rica and Panama, respectively. The tadpole of G. pictiventris resembles those of the other species of Gastrophryne. The tadpole of N. aterrima differs from other New World microhylid tadpoles in location of the vent tube (medial), the spiracular opening (ventral to the gut), and eyes (dorsolateral). The unique configuration of mouthparts in N. aterrima is described. Morphological variation in microhylid tadpoles is reviewed and six larval characters are analyzed cladistically for IO New World microhylid genera.


An Analysis Of External Features As Predictors Of Reproductive Status In Small Mammals, Kenneth Wayne Mccravy Apr 1990

An Analysis Of External Features As Predictors Of Reproductive Status In Small Mammals, Kenneth Wayne Mccravy

Biological Sciences Theses & Dissertations

Reproductive status in specimens of nine populations of seven species of small mammals was evaluated by examining the external reproductive features of nipple size, condition of the pubic symphysis, and vaginal condition and, in males, testis position. Usefulness of these external features in predicting true monthly breeding rates was evaluated by comparing predictions of breeding rates with true rates based on necropsy. Accuracy of predictions of reproductive status of individuals based on single external features and combinations of external features and body measurements was then analyzed at a finer level by comparing those predictions with results of necropsy of the …


The Development Of A Policy For The Management Of Dingo Populations In South Australia, R. J. Downward, J. E. Bromell Mar 1990

The Development Of A Policy For The Management Of Dingo Populations In South Australia, R. J. Downward, J. E. Bromell

Vertebrate Pest Conference Proceedings: 14th (1990)

Competing concerns between conservation and sheep-growing interests in South Australia over problems associated with the naturalized dog,Canis familiaris dingo, prompted the development of a policy for the management of this subspecies. The background to the development of this policy is outlined. The policy provides for a compromise between the need to protect the livestock industry while ensuring the continued survival of the dingo as a wildlife species.


Helminth Parasitism In Martens (Martes Americana) And Ermines (Mustela Erminea) From Washington, With Comments On The Distribution Of Trichinella Spiralis, Eric P. Hoberg, Keith B. Aubry, J. David Brittell Jan 1990

Helminth Parasitism In Martens (Martes Americana) And Ermines (Mustela Erminea) From Washington, With Comments On The Distribution Of Trichinella Spiralis, Eric P. Hoberg, Keith B. Aubry, J. David Brittell

Harold W. Manter Laboratory of Parasitology: Faculty Publications

Helminths are reported for the first time from ermines (Mustela erminea) and martens (Martes americana) in Washington, USA. Among 22 adult ermines, 41% were infected by one or more of five species (Taenia mustelae, Alaria mustelae, Molineus patens, M. mustelae, and Trichinella spiralis). Among 78 adult martens from three geographic localities, the prevalence was 83%. Nine species were identified (Mesocestoides sp., T. mustelae and T. martis americana, Euryhelmis squamula, M. patens, Baylisascaris devosi, Physaloptera sp., Soboliphyme baturini, and T. spiralis). Trichinella spiralis …


Karyotypic Analysis Of Five Rodents And A Marsupial From Belize, Central America, David W. Burton, John W. Bickham, Hugh H. Genoways, Timothy J. Mccarthy May 1987

Karyotypic Analysis Of Five Rodents And A Marsupial From Belize, Central America, David W. Burton, John W. Bickham, Hugh H. Genoways, Timothy J. Mccarthy

University of Nebraska State Museum: Mammalogy Papers

Karyotypes and chromosomal banding patterns of six species of small mammals from Belize are presented and discussed in light of relevant data in the literature. Individuals of Heteromys desmarestianus had FN values of 72, which differs from previous reports. G-bands were obtained and compared to fluorescent bands (DAPI) and with the location of NOR sites. The karyotypes of Peromyscus mexicanus, Sigmodon hispidus, Oryzomys couesi, and Ototylomys phyllotis are identical to the karyotypes for these species described in the literature. Active NORs were located on four pairs of chromosomes in O. phyllotis and fluorescent bands obtained with the …


Morphological Variation, Karyology, And Systematic Relationships Of Heteromys Gaumeri (Rodentia: Heteromyidae), Mark D. Engstrom, Hugh H. Genoways, Priscilla K. Tucker Jan 1987

Morphological Variation, Karyology, And Systematic Relationships Of Heteromys Gaumeri (Rodentia: Heteromyidae), Mark D. Engstrom, Hugh H. Genoways, Priscilla K. Tucker

University of Nebraska State Museum: Mammalogy Papers

Morphological variation was assessed within and among populations of Heteromys gaumeri using univariate and multivariate statistical analyses of external and cranial measurements. Although patterns and amount of nongeographic variation in H. gaumeri were similar to other heteromyines, geographic variation was relatively conservative. Mean values of most characters were statistically homogeneous among localities and spatially unpatterned. Consequently, no association was found between levels of within- and among-sample variation for individual characters (the "Kluge-Kerfoot phenomenon"). Populations of H. gaumeri were chromosomally monomorphic. The lack of morphological and chromosomal variation in H. gaumeri contrasts sharply with patterns in other heteromyines. Heteromys gaumeri is …


Revised Checklist Of North American Mammals North Of Mexico, 1986, J. Knox Jones Jr., Dilford C. Carter, Hugh H. Genoways, Robert S. Hoffmann, Dale W. Rice, Clyde Jones Dec 1986

Revised Checklist Of North American Mammals North Of Mexico, 1986, J. Knox Jones Jr., Dilford C. Carter, Hugh H. Genoways, Robert S. Hoffmann, Dale W. Rice, Clyde Jones

University of Nebraska State Museum: Mammalogy Papers

As in previous lists, orders, families, and genera are listed in conventional phylogenetic sequence mostly following Hall (1981) but, in a departure from previous lists, species are entered alphabetically within each genus. This will facilitate use of the checklist by those unfamiliar with intrageneric taxonomy. Some assemblages are not well enough understood to create a meaningful hierarchy at the specific level.


Environmental Factors Affecting Nocturnal Migrations Of Macrobenthos, C. Timothy Morris Jul 1986

Environmental Factors Affecting Nocturnal Migrations Of Macrobenthos, C. Timothy Morris

Biological Sciences Theses & Dissertations

Nocturnally dispersing macrobenthic invertebrates of the Lafayette River, Norfolk, Virginia were collected from September 4 to October 4, 1982 to determine environmental factors affecting migrations. A total of 55 taxa were identified from 325 surface and bottom nocturnal plankton tows. Peracaridan crustaceans were the dominant (99.0% of the total density) group collected. Six of the commonly collected species showed a significant (P


The Relationship Between Habitat Structure And Small Mammal Communities In Southeastern Virginia And Northeastern North Carolina, Roger Keith Everton Jul 1985

The Relationship Between Habitat Structure And Small Mammal Communities In Southeastern Virginia And Northeastern North Carolina, Roger Keith Everton

Biological Sciences Theses & Dissertations

A variety of terrestrial habitats was pitfall trapped in the vicinity of the Great Dismal Swamp of eastern Virginia and North Carolina to evaluate the small mammal community within the region. Habitat variables were measured at the end of the growing season on 21 0.25 ha grids. Four multivariate tests were used to examine the small mammal communities, their relationship with habitat structure, and the role of habitat selection in community structure.

Cluster and ordination analysis revealed the existence of two distinct associations of small mammals, and their habitat types, within the region. The small mammal associations were interpreted as …


March Rice Rat, Oryzomys Palustris, Hugh H. Genoways Jan 1985

March Rice Rat, Oryzomys Palustris, Hugh H. Genoways

University of Nebraska State Museum: Mammalogy Papers

Includes information on other names used, description, range, habitat, life history and ecology, basis of classification, and recommendations of/for the march rice rat, Oryzomys palustris, in Pennsylvania, USA.


Pygmy Shrew, Microsorex Hoyi, Hugh H. Genoways Jan 1985

Pygmy Shrew, Microsorex Hoyi, Hugh H. Genoways

University of Nebraska State Museum: Mammalogy Papers

Includes the description, range, habitat, life history and ecology, basis of classification, and recommendations of/for the pygmy shrew (Microsorex hoyi) in Pennsylvania, USA.


Badger, Taxidea Taxus, Hugh H. Genoways Jan 1985

Badger, Taxidea Taxus, Hugh H. Genoways

University of Nebraska State Museum: Mammalogy Papers

Includes information on another name, the description, range, habitat, life history and ecology, basis of classification, and recommendations of/for the badger, Taxidea taxus, in Pennsylvania, USA.


Introduction To Species Of Special Concern In Pennsylvania, Chapter 6--Mammals, Hugh H. Genoways Jan 1985

Introduction To Species Of Special Concern In Pennsylvania, Chapter 6--Mammals, Hugh H. Genoways

University of Nebraska State Museum: Mammalogy Papers

First two paragraphs:

The mammals in Pennsylvania have long been under the management authority of the Pennsylvania Game Commission, but it was not until 1978 that an effort was made to deal with threatened and endangered mammals in the Commonwealth. At this time, Michael J. Puglisi was appointed as Coordinator for the Threatened and Endangered Species Program within the Game Commission. In late February 1979, Mr. Puglisi asked Hugh H. Genoways to chair an informal study group on endangered mammals in Pennsylvania. The immediate concern of this group was to be the development of a list of threatened and endangered …


Age And Growth Of The Bluegill Lepomis Macrochrius Rafinesque From An Unmanaged Watershed Lake In Northeast Arkansas With Observations On Lake Ecology, Stephen A. Sewell Jan 1985

Age And Growth Of The Bluegill Lepomis Macrochrius Rafinesque From An Unmanaged Watershed Lake In Northeast Arkansas With Observations On Lake Ecology, Stephen A. Sewell

Journal of the Arkansas Academy of Science

Age and growth data were compiled on 114 bluegill, Lepomis macrochirus Rafinesque, taken from floodwater retarding structure #15 of the Big Creek Watershed project in Craighead and Greene counties of northeast Arkansas. This project was completed in the early 1960's by USDA-SCS. The 73 surface acre lake has not been managed for fish production and has been subjected to unscheduled water level manipulations during dry weather periods. These manipulations have maintained the bluegill population in healthy condition. The oldest bluegill collected were age class IV+. Average condition coefficient K(TL)declined from oldest to youngest individuals (2.96 in age class IV+ - …


Gametogenesis En Chthonerpeton Indistinctum (Gymnophiona: Typhlonectidae), Rafael O. De Sá, Nibia Berois Jan 1985

Gametogenesis En Chthonerpeton Indistinctum (Gymnophiona: Typhlonectidae), Rafael O. De Sá, Nibia Berois

Biology Faculty Publications

RESUMEN:

Histológicamente, las gónadas de Chthonerpeton indistinctum son similares a las ya descritas para otras especies del orden Gymnophiona. Los lóbulos testiculares se hallan compartimentados en unidades estructurales denominadas lóculos. La espermatogénesis ocurre en cistos sincrónicos de células germinales. Durante la espermiogénesis se identifican cuatro estados consecutivos de desarrollo: 1) cistos de espermátidas redondeadas; 2) cistos de espermátidas arrifionadas; 3) cistos de espermátidas bastoniformes y 4) espermátidas en ramillete.

El análisis histológico de los ovarios mostró la presencia de tres estados en la maduración de los folículos ováricos. Estas etapas pueden ser identificadas de acuerdo a: 1) ubicación del folículo …


Estructura Del Ovario De Chthonerpeton Indistinctum (Reinhardt Y Lutken, 1862) (Amphibia: Gymnophiona) Durante La Gestación, Rafael O. De Sá, Nibia Berois Jan 1985

Estructura Del Ovario De Chthonerpeton Indistinctum (Reinhardt Y Lutken, 1862) (Amphibia: Gymnophiona) Durante La Gestación, Rafael O. De Sá, Nibia Berois

Biology Faculty Publications

La morfología e histología del ovario para varias especies del orden Gymnophiona ha sido reportada por Wake (1968, J. Morphol. 126, 291) y para C. indistinctum por los autores (1984, XXIV Reunión de Comunicaciones, Soc. Zool. Uruguay).

Continuando con los estudios sobre el aparato genital de esta especie vivípara, se presenta ahora la estructura del ovario durante la gestación.

Se procesaron con fines histológicos, ovarios de dos hembras grávidas colectadas en las costas de los Dep. Montevideo y San José en abril, 1983. El número de ejemplares trabajados es muy reducido dado lo difícil que resulta su colecta …


Demographic Analysis And Microhabitat Relationships Of A Small Mammal Community In Clearings Of The Great Dismal Swamp, Jean Ferguson Stankavich Oct 1984

Demographic Analysis And Microhabitat Relationships Of A Small Mammal Community In Clearings Of The Great Dismal Swamp, Jean Ferguson Stankavich

Biological Sciences Theses & Dissertations

Small mammals were trapped for 14 months on two grids located within a powerline right-of-way in the Great Dismal Swamp National Wildlife Refuge. During 12,354 trap nights, individuals of 10 different species were captured. They included, from highest to lowest density, Reithrodontomys humulis, Ochrotomys nuttalli, Peromyscus leucopus, Blarina brevicauda, Synaptomys cooperi, Microtus pennsylvanicus, Microtus pinetorum, Sigmodon hispidus, Mus musculus and Oryzomys palustris. The demography (densities, reproduction, home range and dispersal) of each species was analyzed when possible. Most of the species were present in relatively low densities, with a number being captured only during the latter months of the study. …


Catalog Of The Recent Scandentia And Primates In The Carnegie Museum Of Natural History, Suzanne B. Mclaren, Duane A. Schlitter, Hugh H. Genoways Sep 1984

Catalog Of The Recent Scandentia And Primates In The Carnegie Museum Of Natural History, Suzanne B. Mclaren, Duane A. Schlitter, Hugh H. Genoways

University of Nebraska State Museum: Mammalogy Papers

The Section of Mammals, Carnegie Museum of Natural History, houses six specimens of Recent tree shrews and 611 specimens of Recent primates. The only family in the Order Scandentia is Tupaiidae. Primate families represented are Lemuridae, Lorisidae, Cebidae, Callitrichidae, Cercopithecidae, Pongidae, and Hominidae. For each specimen the following data are recorded: locality; date collected; catalog number; sex; age; nature of specimen; condition of specimen and comments. The latter category gives information on the condition of the skin and skeletal material, and gives information on the availability of the specimen.


Activity Levels Of Arboreal Rodents Peromysus And Ochrotomys Evaluated With Nest Cans In Seasonally Flooded Forests, John W. Walke Jul 1984

Activity Levels Of Arboreal Rodents Peromysus And Ochrotomys Evaluated With Nest Cans In Seasonally Flooded Forests, John W. Walke

Biological Sciences Theses & Dissertations

The diversity and density of small mammals in the Dismal Swamp are believed to be small. To test this, four 1.96 ha grids were established and operated in the Dismal Swamp National Wildlife Refuge, from September 1981 to November 1982. Number 10 metal cans covered with plastic lids were placed as nest boxes at 0.5 to 1.5 m height on trees. A 2.5 cm hole allowed access by arboreal rodents, to each nest can. The activity level of the two arboreal rodents, Peromyscus leucopus and Ochrotomys nuttalli, was evaluated by observing types of activity ranging from presence of mice to …


Life History Aspects Of Reithrodontomys Humulis In Southeastern Virginia, Michelle Cawthorn Chandler Jul 1984

Life History Aspects Of Reithrodontomys Humulis In Southeastern Virginia, Michelle Cawthorn Chandler

Biological Sciences Theses & Dissertations

Reithrodontomys humulis, the eastern harvest mouse, is a small cricetid rodent which is common in old field communities in the eastern U.S. A live-trapping study was conducted in Suffolk, Virginia from March 1983 through February 1984 in order to learn the details of its life history and the vegetational characteristics which best describe its microhabitat. Specifically, population densities, trap-revealed survival times, home ranges, plant species composition of the study area, and vegetational structure were examined. In order to trap as many Reithrodontomys as possible, special traps which excluded animals weighing over 20 g were constructed. Densities of harvest mice …


Microgeographic Variation In The Mexican Vole, Microtus Mexicanus, Meredith J. Hamilton, Gary A. Heidt Jan 1984

Microgeographic Variation In The Mexican Vole, Microtus Mexicanus, Meredith J. Hamilton, Gary A. Heidt

Journal of the Arkansas Academy of Science

Altitudinal variation was assessed in 115 (62 male; 53 female) Mexican voles (Microtus mexicanus) from six localities in Jalisco, Mexico. Univariate and multivariate statistical techniques were employed in the data analyses. A total of 49 skeletal measurements were investigated, and of these, 17 showed significant interlocality variation. Rostral breadth, depth of braincase, rostral height, width of third molar and nasal length were found to be the most variable characters. Component I (a size factor) accounted for 36% of the total phenetic variation; components II and III accounted for 30% and 19%, respectively. Larger individuals were found to occur at lower …


River Otter In Arkansas Iii. Characteristics Of Otter Latrines And Their Distribution Along Beaver-Inhabited Watercourses In Southwest Arkansas, Mark R. Karnes, C. Renn Tumlison Jan 1984

River Otter In Arkansas Iii. Characteristics Of Otter Latrines And Their Distribution Along Beaver-Inhabited Watercourses In Southwest Arkansas, Mark R. Karnes, C. Renn Tumlison

Journal of the Arkansas Academy of Science

Forty-one river otter (Lutra canadensis) fecal deposit (latrine) sites were located during April 1983 through March 1984 along beaver (Castor canadensis) inhabited watercourses in Clark, Nevada, and Ouachita counties, Arkansas. Latrine sizes ranged from 64 cm² to 5.01 m² (x-bar=0.30 m²; S.D. =0.88), and contained 2 to 78 scats per latrine (x-bar=9.2; S.D. = 13.8). The most common sites for latrines included elevated leaf or moss covered banks (51.2%), beaver lodges or bank dens (17.1 %), and beaver scent mounds (12.2%). Other latrine sites included felled logs over open water, bare soil along elevated banks, and exposed sandbars. Otter presence …


Phylogeny And Paleobiogeography Of Short-Tailed Shrews (Genus Blarina), Cheri A. Jones, Jerry R. Choate, Hugh H. Genoways Jan 1984

Phylogeny And Paleobiogeography Of Short-Tailed Shrews (Genus Blarina), Cheri A. Jones, Jerry R. Choate, Hugh H. Genoways

University of Nebraska State Museum: Mammalogy Papers

Dental measurements of Pleistocene and Holocene shrews of the genus Blarina were analyzed in a multivariate assessment of phylogeny and paleobiogeography of the genus. Blarina brevicauda, or an indistinguishable precursor, apparently was the ancestral form. Two semispecies, brevicauda and talpoides, are recognizable early in the fossil record; these two phena probably appeared as a result of increasing diversity'in the environment of the late Irvingtonian. Evidently, repeated fluctuations of climate and the subsequent changes in range have not been sufficient to cause the cessation of gene flow necessary to complete speciation.

A second species, B. carolinensis, appeared in …