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Title: New Subspecies of the Rodent Baiomys From Central America - University of Kansas Publications, Museum of Natural History
Author: Packard, Robert L.
Language: English
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  UNIVERSITY OF KANSAS PUBLICATIONS
  MUSEUM OF NATURAL HISTORY



  Volume 9, No. 15, pp. 397-404
  December 19, 1958



  New Subspecies of the Rodent Baiomys
  From Central America

  BY

  ROBERT L. PACKARD


  UNIVERSITY OF KANSAS
  LAWRENCE
  1958



  UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

  Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
  Robert W. Wilson


  Volume 9, No. 15, pp. 397-404
  Published December 19, 1958


  UNIVERSITY OF KANSAS
  Lawrence, Kansas


  PRINTED IN
  THE STATE PRINTING PLANT
  TOPEKA, KANSAS
  1958

  27-5660



New Subspecies of the Rodent Baiomys From Central America

BY

ROBERT L. PACKARD


The southern pygmy mouse, _Baiomys musculus_, is known as far north as
the Mexican states of Jalisco, Michoacán, south of the Mesa Central,
east to central Veracruz (see Hooper, 1952a:90), and south to western
Nicaragua (see Goodwin, 1942:161). Previously, two subspecies have been
recognized from the southern part of the known range of this species:
_B. m. nigrescens_, blackish mice from Chiapas, México, and Guatemala,
and _B. m. grisescens_, grayish-brown mice from Honduras and western
Nicaragua. Study of recently acquired specimens from Guatemala, El
Salvador, and Nicaragua reveals two additional subspecies.

For the loan of comparative material, I am grateful to the United States
National Museum (USNM) and the American Museum of Natural History
(AMNH). Unless otherwise indicated, specimens are in the University of
Kansas Museum of Natural History. Measurements are as taken by Hooper
(1952b:10). Postpalatal length is the distance from the posterior margin
of the hard palate to the anterior margin of the foramen magnum. Unless
otherwise noted, statistical significance as used in this paper is at
the 95 per cent confidence limit or higher.

The two heretofore undescribed subspecies are characterized below and
may be known as:


=_Baiomys musculus handleyi_=, new subspecies

     _Type._--Adult female, USNM No. 275604 (Biological Surveys
     Collection), skin and skull; from Sacapulas, El Quiché, Guatemala;
     obtained on April 24, 1947, by Charles O. Handley, Jr., original
     number 991.

     _Distribution._--Known only from the type locality; probably
     inhabits parts of the east-west drainage of the Río Negro.

     _Diagnosis._--General ground color of upper parts between Wood
     Brown and Buffy Brown (all capitalized color terms are those of
     Ridgway, Color Standards and Color Nomenclature, Washington, D. C.,
     1912), dorsal parts of fore- and hind-feet, and ankles white; in
     region of median venter, throat, and chin, hairs white to base; in
     lateral regions hairs Neutral Gray at base; dorsal hairs below tips
     Avellaneous, Neutral Gray at base; guard hairs black-tipped; tail
     white below, brownish above; nasals truncate anteriorly;
     frontalparietal suture forming an obtuse angle with median-parietal
     suture; alveolar-length of upper molar tooth-row and tail long.

     _Comparisons._--From _Baiomys musculus nigrescens_ (paratypes, from
     the Valley of Comitán, Chiapas, México), found to the north, _B. m.
     handleyi_ differs in: color paler dorsally and ventrally; fore- and
     hind-feet whitish instead of dusky to sooty; hairs in region of
     facial vibrissae white instead of brown; tail bicolored instead of
     unicolored; anterior tips of nasals square, not rounded;
     frontoparietal suture forming obtuse angle with median parietal
     suture instead of a right angle; tail and alveolar length of upper
     molar tooth-row significantly larger (see table 1); zygomatic
     breadth, breadth of braincase, occipitonasal length, least
     interorbital constriction, and length of rostrum all averaging
     larger (see table 2).

     From _Baiomys musculus grisescens_ (paratypes, from Comayabuela,
     Honduras) to the south, _B. m. handleyi_ differs in: buff-colored
     hairs in dorsal and ventral region lacking; fore- and hind-feet
     white, not flesh-colored with gray overtones; tail bicolored, not
     unicolored; face paler, lacking buff-brown coloration; anterior
     tips of nasals squared rather than flaring; tail and upper molar
     tooth-row significantly longer (see Table 1); hind foot, ear from
     notch, and rostrum longer; braincase averaging broader (see Table
     2).

_Remarks._--The occurrence of these pale mice in the Río Negro Valley
was first noted by Goodwin (1934:39, 40) when he referred specimens from
Sacapulas and Chanquejelve, Guatemala, to _B. m. musculus_. Hooper (_op.
cit._:92-94) correctly assigned specimens from the southern coast and
eastern part of Chiapas to _B. m. nigrescens_. The continued assignment
of specimens from Sacapulas, Guatemala, to the subspecies _musculus_
produces a hiatus both in the range of _B. m. nigrescens_ and _B. m.
musculus_. Twenty-four specimens, 14 from 1 mi. S Rabinal, and 10 from
1/2 mi. N, 1 mi. E Salama, Guatemala, are intergrades between _handleyi_
and _grisescens_, but show more resemblance to the latter and,
therefore, are referred to that subspecies. To the north, _handleyi_
intergrades with _nigrescens_. The specimen from Chanquejelve is an
intergrade between the two subspecies just mentioned.

Osgood suggested (1909:259) that the degree of relative humidity might
in some way control color of pelage in this species. Relative humidity
and its subsequent effect on other related environmental factors indeed
may account for the superficial resemblance of _B. m. musculus_ to _B.
m. handleyi_ (although _handleyi_ averages paler throughout than the
paratypical series of _musculus_). Both subspecies inhabit relatively
arid country. According to Goodwin (_op. cit._:39 and Plate 5, Fig. 1),
and Handley (_in verbis_), the Río Negro Valley in the vicinity of
Sacapulas is extremely hot, dry, and rather isolated. Extremes of
climate there may exceed those in the arid habitat occupied by _B. m.
musculus_. The resemblance between these two subspecies may result from
nearly parallel selective forces that have given rise to two distinct
subspecies. _B. m. handleyi_ may have developed _in situ_.

     _Specimens examined._--Total 49, from the type locality, including
     the type (12, USNM; 37, AMNH).


=_Baiomys musculus pullus_=, new subspecies

     _Type._--Adult female, skin and skull, University of Kansas Museum
     of Natural History, No. 71605, from 8 mi. S Condega, Esteli,
     Nicaragua; obtained on July 15, 1956, by A. A. Alcorn, original No.
     4218.

     _Distribution._--West-central Nicaragua, from Matagalpa northwest
     into the valley of the Río Esteli, east as far as Jinotega.

     _Diagnosis._--Dorsum Fuscus-Black (see remarks),
     individual dorsal hairs being black-tipped with a subterminal
     Ochraceous-Buff band, Neutral Gray at base; some hairs on dorsum
     all black to Neutral Gray at base; hair on sides Neutral Gray
     tinged with blackish; facial region blackish becoming more buffy
     ventrally; vibrissae black; tail unicolored Chaetura Black; fore-
     and hind-feet whitish to dusky-white; mid-ventral region of belly
     white to as far anteriorly as region of throat, hairs being white
     to base; in region of anus and throat, hairs white-tipped, Neutral
     Gray at base; tail long; upper molar tooth-row short as in _B. m.
     nigrescens_; zygoma bowed as in _B. m. grisescens_.

     _Comparisons._--From _B. m. grisescens_ (paratypes from
     Comayaguela, Honduras), _B. m. pullus_ differs in: dorsal
     ground-color and tail darker; sides and distal region of belly
     grayish instead of buffy-brown, thus making white stripe in region
     of belly distinct; average length of body and tail significantly
     longer, thus, total length greater; length of hind foot averaging
     longer (68 per cent confidence limits); alveolar length of upper
     molar tooth-row significantly shorter; occipitonasal and rostral
     length averaging longer; zygomatic spread and interorbital region
     narrower; length of incisive foramina, depth of cranium,
     postpalatal length, and breadth of braincase all averaging larger
     (see table 2).

     From _B. m. nigrescens_ (paratypes from Valley of Comitán), _B. m.
     pullus_ differs in: dorsal ground-color slightly darker; facial
     region grayish, not sooty; mid-ventral white stripe present on
     belly and becoming grayish laterally; tail darker and less hairy,
     average length significantly longer; body, occipitonasal length of
     skull, incisive foramina, and postpalatal length averaging smaller;
     hind foot shorter; zygomatic spread, interorbital region and
     braincase broader (see table of measurements); cranium deeper.

_Remarks._--_B. m. pullus_ is the darkest dorsally of any subspecies of
this species. Dalquest (1953:156) pointed out that preserved specimens
of one of the subspecies of the northern pygmy mouse, _Baiomys taylori
taylori_, tended to fade considerably over a period of four years.
Post-mortem changes in color also are apparent in the southern species
_musculus_. For example, the series of specimens from 8 mi. S of
Condega, and 9 mi. NNW Esteli, Nicaragua, have faded from near Chaetura
Black to the present Fuscous-Black in a period of two years. The most
notable change in color came after the first six months of preservation.
Allowing for this fading, the several color differences between
_pullus_, _nigrescens_ and _grisescens_ are, nevertheless, distinctive.

TABLE 1.--ANALYSIS OF VARIATION IN ADULTS OF FOUR SUBSPECIES OF BAIOMYS
MUSCULUS (measurements in millimeters)

===============+========+========+=========+========+==========
     Number    |        | Length | Length  | Length |  Upper
   of adults   | Total  | of     |   of    |   of   |  molar
    averaged   | length | body   |  tail   |  hind  |  length
               |        |        |         |  foot  |(alveolar)
---------------+--------+--------+---------+--------+----------
               | _Baiomys musculus handleyi_
               | Sacapulas, El Quiché, Guatemala
               |
9 Av           | 121.44 |  70.77 |  50.67  |  15.33 |   3.48
Max            | 128.00 |  77.00 |  54.00  |  16.00 |   3.60
Min            | 115.00 |  66.00 |  49.00  |  15.00 |   3.40
2xStand. error |   3.60 |   3.22 |   1.26  |    .44 |    .05
---------------+--------+--------+---------+--------+----------
               | _Baiomys musculus pullus_
               | 8 mi. S Condega, Nicaragua
               |
17 Av          | 117.29 |  70.42 |  47.18  |  15.47 |   3.13
Max            | 121.00 |  74.00 |  50.00  |  17.00 |   3.20
Min            | 111.00 |  66.00 |  44.00  |  14.00 |   3.00
2xStand. error |   1.27 |   1.51 |    .75  |    .35 |    .03
---------------+--------+--------+---------+--------+----------
               | _Baiomys musculus grisescens_
               | Comayaguela, Honduras
               |
7 Av           | 103.71 |  59.00 |  44.71  |  14.57 |   3.31
Max            | 118.00 |  68.00 |  50.00  |  15.00 |   3.40
Min            |  97.00 |  51.00 |  42.00  |  13.00 |   3.20
2xStand. error |   5.50 |   4.16 |   2.40  |    .78 |    .06
---------------+--------+--------+---------+--------+----------
               | _Baiomys musculus nigrescens_
               | Valley of Comitán
               |
11 Av          | 115.00 |  72.09 |  42.91  |  15.31 |   3.15
Max            | 120.00 |  77.00 |  45.00  |  16.00 |   3.40
Min            | 108.00 |  69.00 |  39.00  |  14.50 |   2.90
2xStand. error |   2.12 |   1.59 |    1.0  |   .23  |    .10
---------------+--------+--------+---------+--------+----------

Geographically, _pullus_ is partly isolated by the Cerros De Villaguaire
and the Cerros El Zapotillo to the west and the Cerros De
Azaculapa to the north. Certain individuals of a series of specimens,
referable to _B. m. nigrescens_, from 1 mi. NW San Salvador
and 1 mi. S Los Planes, El Salvador, are intermediate in coloration
between that subspecies and _pullus_. Three of 28 specimens
from El Salvador possess the mid-ventral white stripe.

TABLE 2.--CRANIAL MEASUREMENTS (in millimeters) OF ADULTS OF FOUR
SUBSPECIES OF BAIOMYS MUSCULUS

Table headings:
Col A: Occipitonasal length
Col B: Zygomatic breadth
Col C: Postpalatal length
Col D: Least interorbital breadth
Col E: Length of incisive foramena
Col F: Length of rostrum
Col G: Breadth of braincase
Col H: Depth of cranium

================+======+======+======+======+======+=====+=====+=====
                |   A  |   B  |  C   |  D   |  E   |  F  |  G  |  H
----------------+------+------+------+------+------+-----+-----+-----
                | _Baiomys musculus handleyi_,
                | Sacapulas, El Quiché, Guatemala
Number          |
 of specimens   |   8  |   8  |   8  |   9  |   9  |  9  |  8  |  8
Type 275604 ♀   |      |      |      |      |      |     |     |
 USNM           | 20.0 | 10.4 |  7.3 |  4.0 |  4.5 | 7.3 |  9.7|  7.1
Average         | 19.6 | 10.5 |  6.9 |  4.0 |  4.2 | 7.2 |  9.8|  7.1
Maximum         | 20.7 | 11.0 |  7.4 |  4.0 |  4.5 | 7.7 | 10.2|  7.2
Minimum         | 18.8 | 10.2 |  6.4 |  3.9 |  4.0 | 7.0 |  9.7|  6.8
                |      |      |      |      |      |     |     |
----------------+------+------+------+------+------+-----+-----+-----
                | _Baiomys musculus pullus_,
                | 8 mi. S Condega, Esteli, Nicaragua
                |
Number          |      |      |      |      |      |     |     |
of specimens    | 17   | 17   |  15  |  17  |  17  | 17  | 17  | 17
Type 71605 ♀ KU | 19.2 | 10.2 |  6.8 |  3.8 |  4.3 | 6.8 |  9.5|  7.0
Average         | 19.3 | 10.2 |  7.0 |  3.9 |  4.3 | 7.0 |  9.6|  7.0
Maximum         | 19.8 | 10.6 |  7.3 |  4.1 |  4.6 | 7.4 | 10.0|  7.3
Minimum         | 18.9 |  9.7 |  6.8 |  3.8 |  4.0 | 6.5 |  9.3|  6.8
----------------+------+------+------+------+------+-----+-----+-----
                | _Baiomys musculus grisescens_,
                | Comayaguela, Guatemala
                |
Number          |
 of specimens   |  6   |  7   |  7   |  7   |  7   | 6   | 7   | 7
Average         | 19.7 | 10.5 |  6.9 |  3.9 |  4.1 | 7.1 | 9.6 | 6.9
Maximum         | 20.3 | 10.9 |  7.2 |  4.1 |  4.4 | 7.3 | 9.9 | 7.1
Minimum         | 19.2 | 10.2 |  6.7 |  3.7 |  3.9 | 6.8 | 9.3 | 6.8
----------------+------+------+------+------+------+-----+-----+-----
                | _Baiomys musculus nigrescens_,
                | Valley of Comitán, Chiapas, México
                |
Number          |
 of specimens   |  14  |  14  |  13  |  14  |  14  | 14  | 14  | 14
Average         | 19.5 | 10.1 |  7.1 |  3.8 |  4.4 | 6.9 | 9.3 | 6.9
Maximum         | 20.3 | 11.1 |  7.4 |  4.0 |  4.6 | 7.4 | 9.6 | 7.3
Minimum         | 19.1 |  9.8 |  6.7 |  3.6 |  4.2 | 6.6 | 9.0 | 6.7
----------------+------+------+------+------+------+-----+-----+-----

Albert Alcorn wrote in his itinerary that some of the type series
were taken shortly after lunch (I assume this would mean near
noon) near a small creek, and that the specimens from 9 mi. NNW
Esteli were trapped in wood piles and rock piles about dusk.

_Specimens examined._--Total (all from Nicaragua) 36 as follows: Esteli:
type locality, 22 (including the type); 8 mi. NNW Esteli, 3; 9 mi. NNW
Esteli, 8. Jinotega: 1 mi. NW Jinotega, 1; San Rafael Del Norte, 1 AMNH.
Matagalpa: Matagalpa, 1 AMNH.



LITERATURE CITED


DALQUEST, W. W.

1953. Mammals of the Mexican state of San Luis Potosí. Louisiana State
Univ. Studies, Biol. Sci. Ser. No. 1:1-229, 1 fig., December 28.

GOODWIN, G. G.

1934. Mammals collected by A. W. Anthony in Guatemala, 1924-1928.
Bull. Amer. Mus. Nat. Hist., 68:1-60, 5 pls., December 12.

HOOPER, E. T.

1952a. Notes on the pygmy mouse (Baiomys), with description of a new
subspecies from Mexico. Jour. Mamm., 33:90-97, February 18.

1952b. A systematic review of the harvest mice (Genus Reithrodontomys)
of Latin America. Misc. Publ., Mus. Zool., Univ. Mich., 77:1-255,
9 pls., January 16.

OSGOOD, W. T.

1909. Revision of the mice of the American Genus Peromyscus. N. Amer.
Fauna, 28:1-285, 8 pls., 12 figs., April 17.

_Transmitted August 25, 1958._


       *       *       *       *       *

  Transcriber's Note
  Variations of spelling as presented in the paper have been retained

  fuscus; fuscous
  foramen; foramena
  comayabuela; comayaguela

  Bold text is represented like =this=
  Italic text is represented like _this_





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