Speciation of the Wandering Shrew

Part 1

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================================================================== UNIVERSITY OF KANSAS PUBLICATIONS MUSEUM OF NATURAL HISTORY

Volume 9, No. 1, pp. 1-68, figures 1-18 -------------------- December 10, 1955 ---------------------

Speciation of the Wandering Shrew

BY JAMES S. FINDLEY

UNIVERSITY OF KANSAS LAWRENCE 1955

UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, A. Byron Leonard, Robert W. Wilson

Volume 9, No. 1, pp. 1-68, figures 1-18 Published December 10, 1955

UNIVERSITY OF KANSAS Lawrence, Kansas

PRINTED BY FERD VOILAND, JR., STATE PRINTER TOPEKA, KANSAS 1955 [Illustration: union label] 25-7903

Speciation of the Wandering Shrew

JAMES S. FINDLEY

CONTENTS

PAGE

INTRODUCTION 4

MATERIALS METHODS AND ACKNOWLEDGMENTS 4

NON-GEOGRAPHIC VARIATION 7

CHARACTERS OF TAXONOMIC WORTH 8

PELAGE CHANGE 9

GEOGRAPHIC DISTRIBUTION AND VARIATION 9 Pacific Coastal Section 9 Inland Montane Section 11 Great Basin and Columbia Plateau Section 12 Summary of Geographic Variation 13

ORIGIN OF THE Sorex vagrans RASSENKREIS 16

RELATIONSHIPS WITH OTHER SPECIES 26

CONCLUSIONS 60

TABLE OF MEASUREMENTS 62

LITERATURE CITED 66

FIGURES

FIGS. 1-2.--CRANIAL MEASUREMENTS 5

Part 2

FIG. 3.--GRAPH ILLUSTRATING WEAR OF TEETH 8

FIG. 4.--GRAPH ILLUSTRATING HETEROGONIC GROWTH OF ROSTRUM 10

FIG. 5.--PRESENT GEOGRAPHIC DISTRIBUTION OF Sorex vagrans 15

FIG. 6.--SKULLS OF Sorex vagrans 17

FIGS. 7-10.--PAST GEOGRAPHIC DISTRIBUTION OF SHREWS 19-20-22-27

FIGS. 11, 12.--MEDIAL VIEW OF LOWER JAWS OF TWO SHREWS 30

FIGS. 13, 14.--SECOND UNICUSPID TEETH OF SHREWS 30

FIG. 15.--DIAGRAM OF PROBABLE PHYLOGENY OF SHREWS 32

FIGS. 16-18.--GEOGRAPHIC DISTRIBUTION OF SUBSPECIES 33-40-53

INTRODUCTION

The purpose of this report is to make clear the biological relationships between the shrews of the Sorex vagrans-obscurus "species group." This group as defined by H. H. T. Jackson (1928:101) included the species Sorex vagrans, S. obscurus, S. pacificus, S. yaquinae, and S. durangae. The last mentioned species has been shown (Findley, 1955:617) to belong to another species group. Sorex milleri, also assigned to this group by Jackson (1947:131), seems to have its affinities with the cinereus group as will be explained beyond. The position of the vagrans group in relationship to other members of the genus will be discussed.

Of this group, the species that was named first was Sorex vagrans Baird, 1858. Subsequently many other names were based on members of the group and these names were excellently organized by Jackson in his 1928 revision of the genus. Subsequent students of western mammals, nevertheless, have been puzzled by such problems as the relationship of (1) Sorex vagrans monticola to Sorex obscurus obscurus in the Rocky Mountains, (2) Sorex pacificus, S. yaquinae, and S. obscurus to one another on the Pacific Coast, and (3) S. o. obscurus to S. v. amoenus in California. Few studies have been made of these relationships. Clothier (1950) studied S. v. monticola and S. o. obscurus in western Montana and concluded that the two supposed kinds actually were not separable in that area. Durrant (1952:33) was able to separate the two kinds in Utah as was Hall (1946:119, 122) in Nevada. Other mammalogists who worked within the range of the vagrans-obscurus groups have avoided the problems in one way or another. Recently Rudd (1953) has examined the relationships of S. vagrans to S. ornatus.

MATERIALS METHODS AND ACKNOWLEDGMENTS

Approximately 3,465 museum study skins and skulls were studied. Most of these were assembled at the University of Kansas Museum of Natural History, but some were examined in other institutions.

Specimens were grouped by geographic origin, age, and sex. Studies of the role of age and sex in variation were made. Because it was discovered that secondary sexual variation was negligible, both males and females, if of like age and pelage, were used in comparisons designed to reveal geographic variation.

External measurements used were total length, length of tail, and length of hind foot. After studying a number of cranial dimensions I chose those listed below as the most useful in showing differences in size and proportions of the skull. Figures 1 and 2 show the points between which those measurements were taken.

Condylobasal length.--From anteriormost projection of the premaxillae to posteriormost projection of the occipital condyles (a to a').

Maxillary tooth-row.--From posteriormost extension of M3 to anteriormost extension of first unicuspid (b to b').

Palatal length.--From anteriormost projection of premaxillae to posteriormost part of bony palate (c to c').

Cranial breadth.--Greatest lateral diameter of braincase (d to d').

Least interorbital breadth.--Distance between medialmost superior edges of orbital fossae, measured between points immediately above and behind posterior openings of infraorbital foramina (e to e').

Maxillary breadth.--Distance between lateral tips of maxillary processes (f to f').

In descriptions of color, capitalized terms refer to those in Ridgway (1912). In addition the numerical and alphabetical designations of these terms are given since a knowledge of the arrangements of these designations enables one quickly to evaluate differences between stated colors. Color terms which are not capitalized do not refer to any precise standard of color nomenclature.

In the accounts of subspecies, descriptions, unless otherwise noted, are of first year animals as herein defined. Descriptions of color are based on fresh pelages.

Unless otherwise indicated, specimens are in the University of Kansas Museum of Natural History. Those in other collections are identified by the following abbreviations:

AMNH American Museum of Natural History CM Carnegie Museum ChM Chicago Museum of Natural History CMNH Cleveland Museum of Natural History FC Collection of James S. Findley HC Collection of Robert Holdenreid SGJ Collection of Stanley G. Jewett CDS Collection of Charles D. Snow AW Collection of Alex Walker NMC National Museum of Canada OSC Oregon State College PMBC British Columbia Provincial Museum of Natural History SD San Diego Natural History Museum BS United States Biological Surveys Collection USNM United States National Museum UM University of Michigan Museum of Zoology OU University of Oregon Museum of Natural History UU University of Utah Museum of Zoology WSC Washington State College, Charles R. Conner Museum

In nature, the subspecies of Sorex vagrans form a cline and are distributed geographically in a chain which is bent back upon itself. The subspecies in the following accounts are listed in order from the southwestern end of the chain clockwise back to the zone of overlap.

The synonymy of each subspecies includes the earliest available name and other names in chronological order. These include the first usage of the name combination employed by me and other name combinations that have been applied to the subspecies concerned.

Part 3

In the lists of specimens examined, localities are arranged first by state or province. These are listed in tiers from north to south and in any given tier from west to east. Within a given state, localities are grouped by counties, which are listed in the same geographic sequence as were the states and provinces (N to S and W to E). Within a given county, localities are arranged from north to south. If two or more localities are at the same latitude the westernmost is listed first. Marginal localities are listed in a separate paragraph at the end of each account. The northernmost marginal locality is listed first and the rest follow in clockwise order. Those records followed by a citation to an authority are of specimens which I have not personally examined. Marginal records are shown by dots on the range maps. Marginal records which cannot be shown on the maps because of undue crowding are listed in Italic type.

To persons in charge of the collections listed above I am deeply indebted. Without their generous cooperation in allowing me to examine specimens in their care this study would not have been possible. Appreciated suggestions in the course of the work have been received from Professors Rollin H. Baker, A. Byron Leonard, R. C. Moore, Robert W. Wilson, and H. B. Tordoff, and many of my fellow students. Mr. Victor Hogg gave helpful suggestions on the preparation of the illustrations. My wife, Muriel Findley, devoted many hours to secretarial work and typing of manuscript. Finally I am grateful to Professor E. Raymond Hall for guidance in the study and for assistance in preparing the manuscript. During the course of the study I received support from the University of Kansas Endowment Association, from the Office of Naval Research, and from the National Science Foundation.

NON-GEOGRAPHIC VARIATION

Non-geographic variation, that is to say, variation within a single population of shrews, consists of variation owing to age and normal individual variation. In Sorex I have detected no significant secondary sexual differences between males and females; accordingly the two sexes are here considered together.

Variation with age must be considered in order to assemble comparable samples of these shrews. Increased age results in wear on all teeth and in particularly striking changes in the size and shape of the first incisors. Skulls of older shrews develop sagittal and lambdoidal ridges, and further differ from skulls of young animals in being slightly broader and shorter, and in developing thicker bone, particularly on the rostrum which thus seems to be, but is not always in fact, more robust. Pruitt has recently (1954) noted these same cranial differences in specimens of Sorex cinereus of different ages.

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