Herpetologists` League

Herpetologists' League
Phylogeographic Patterns in Kinosternon subrubrum and K. baurii Based on Mitochondrial
DNA Restriction Analyses
Author(s): DeEtte Walker, Paul E. Moler, Kurt A. Buhlmann, John C. Avise
Source: Herpetologica, Vol. 54, No. 2 (Jun., 1998), pp. 174-184
Published by: Herpetologists' League
Stable URL: http://www.jstor.org/stable/3893425
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174
HERPETOLOGICA
trial Vertebrates in the Neotropical Realm. Dr. W
Junk, The Hague, The Netherlands.
PARKER, H. W 1935. The lizards of Trinidad. Trop.
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PINTO, M. N. 1994. Cerrado: CaracterizaVao, Ocupa,Vo e Perspectivas (2nd ed.). Editora Universidade de Brasilia, Brasilia, Brasil.
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19:189-192.
VITT, L. J. 1982. Sexual dimorphism and reproduction in the microteiid lizard, Gymnophthalmus
multiscutatus. J. Herpetol. 16:325-329.
SHERBROOKE,
Accepted: 29 June 1997
Associate Editor: Daniel Formanowicz, Jr.
Herpetologica,54(2), 1998, 174-184
? 1998 by The Herpetologists' League, Inc.
PHYLOGEOGRAPHIC PATTERNS IN KINOSTERNON
SUBRUBRUM AND K. BAURII BASED ON MITOCHONDRIAL
DNA RESTRICTION ANALYSES
DEETTE
WALKER,'
PAUL E. MOLER,2 KURT A. BUHLMANN,3 AND JOHN
C. AVISE'
'Department of Genetics, University of Georgia, Athens, GA 30602, USA
2Wildlife Research Laboratory, Florida Game and Fresh Water Fish Commission, 4005 South Main Street,
Gainesville, FL 32601, USA
3Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29801, USA
ABSTRACT: We used restriction assays of mitochondrial (mt) DNA to estimate phylogeographic
variation in two sister taxa of muid turtles in the southeastern United States. Extensive mtDNA
variation characterized Kinosternon subrubrum and, to a lesser degree, K. baurii. Each of 26
mtDNA haplotypes from the 83 assayed specimens was localized spatially. Collectively, these
mtDNA haplotypes demarcated four major matrilineal assemblages, each with a well defined regional distribution: a western group (A) in Missouri and Louisiana, a central group (B) throughout
the Gulf coastal states, an eastern group (C) along the Atlantic coastal states north of Florida, and
a southern group (D) in peninsular Florida. All assayed samples of K. baurii belonged to the mtDNA
C assemblage. The two species in Florida are thus highly distinct in mtDNA genotype, but they
exhibit minimal mtDNA divergence along the Atlantic coastal states. These findings raise questions
concerning the evolutionary history and taxonomy of these two recognized species. MtDNA phylogeographic patterns in the baurii/subrubrum complex are remarkably similar to those reported
previously for two other southeastern kinosternids, Sternotherus minor and S. odoratus.
Key words: Mud turtles; Phylogeography; Gene flow; Population struicture; Southeastern United
States; Kinosternon.
MUD turtles (Kinosternon)
are semiaquatic organisms typically associated with
slow-moving, often ephemeral waters such
as shallow bayous, swamps, and ditches.
These turtles commonly are observed traversing land (Ernst and Barbour, 1989;
Ernst et al., 1994), a habit that may influence patterns of inter-drainage gene flow
(Gibbons, 1983) and geographic population structure. Sixteen species of mud turtles are recognized in North, Central, and
South America (Ernst et al., 1994), two of
June 1998]
HERPETOLOGICA
***K.
175
b auriit
K. s. hippocrepis
K. s. subrubrum
K. s. steindachneri
FIG. 1.-Map of the southeastern United States showing collection sites for mud turtle specimens (black
dots, K. subrubrum; stars, K. baurii). The described range of K. baurii is to the east and south of the heavy
line (i.e., the Atlantic coastal plain and all of peninsular Florida).
which (Kinosternon subrubrum and K.
baurii) occur in the southeastern United
States.
Three subspecies of K. subrubrum currently are recognized (Conant and Collins,
1991; Ernst et al., 1994: Fig. 1). The eastern mud turtle, K. s. subrubrum, occurs
along the Atlantic coast from Long Island,
New York to northern Florida and west
into the lower and central Mississippi Riv-
er basin. The Florida mud turtle, K. s.
steindachneri, is confined to the Florida
peninsula. The Mississippi mud turtle, K.
s. hippocrepsis, inhabits primarily western
Mississippi, Louisiana, and portions of Arkansas, Oklahoma, and Texas. Intergradation is reported between these subspecies
where their ranges adjoin or overlap
(Ernst et al., 1974; Iverson, 1977). The
striped mud turtle, K. baurii, occurs along
176
HERPETOLOGICA
the Atlantic coast from southern Virginia
to the Florida Keys (Ernst et al., 1994;
Lamb and Lovich, 1990; Mitchell, 1994).
Most southern specimens of K. baurii
display pronounced stripes on the carapace and head, but these stripes ebb in
northern specimens, which causes identification difficulties with K. s. subrubrum,
a subspecies lacking such markings (Lamb,
1983a,b; Lamb and Lovich, 1990). Prior
phylogenetic analyses based on allozymes
(Seidel et al., 1986), karyology (Sites et al.,
1979), and morphology (Iverson, 1991)
suggested that K. baurii and K. subrubrum
are closely related sister taxa within the Kinosternidae, but these studies were not
designed to assess geographic variability
within either species. Here we examine
mitochondrial (mt) DNA variation within
and between geographic populations of K.
baurii and K. subrubrum.
MATERIALS AND METHODS
Samples and Laboratory Procedures
[Vol. 54, No. 2
1.-MtDNA
haplotypes observed in Kinosternon subrubrum and K baurii. Letters from left to
right in the descriptions represent digestion profiles
for the restriction enzymes BanI, Bcll, BglI, BglII,
DraII, EcoRI, Hindll, HindIII, KpnI, NciI, NsiI,
PvuII, StuI, and XbaI.
TABLE
Haplotype
code
K subrl
No. of
individuals
3
3
6
Description
K subr2
K subr3
K subr4
K subr5
K subr6
K subr7
K subr8
K subr9
K subrlO
K subrll
K subrl2
K subrl3
K subrl4
K subrl5
K subrl6
K subrl7
K subrl8
K subrl9
K subr20
5
16
1
CCCDCCCCCCCCCD
CBCDCCCCCCCCCD
CBCDCCCCCDCCCC
BBCDDCCCBDCCCC
CBCDCCCFCDCCCC
CBCDCCCCCCBCCC
CBCDBCCCCDCCCC
CBCDBCCCCDCCDC
BACCFCABBBEDCC
AACCFCABBBEDCB
BACCFCBBBBEDCC
BACCFCABBBEECC
DACDECGACAFCBC
DACDECGADCFCCC
DACDECDACCFCCC
DACEECDACBFCCC
BACBFCABBFEDCC
BACCFCABBFEDCC
CEDCEBEECCHCFC
BACGFCABBBEDCB
K baur2l
4
CBCDCCCCCCCACC
1
1
3
2
1
9
2
1
3
1
1
1
2
2
1
We collected 64 specimens of K. subru- K baur22
CBCDCCCCCCCCCC
10
CBCDCCFCCCCBCC
brum from 32 locales and 19 specimens of K baur23
1
baur24
CBCDCCFECCCBCC
K. baurii from 11 locales (Fig. 1, Appendix K
K baur25
2
CBCDCCICCCCBCC
I). The specimens of K. baurii from Florida K baur26
1
CACDCCFCCCCBCC
were easily distinguished morphologically
from K. subrubrum because they displayed
the characteristic stripes on the carapace
and head. Specimens of K. baurii from At- gested by 14 restriction enzymes (Table 1)
lantic coast drainages had head stripes; following recommendations of the manutheir identification to species by Joseph facturer (Boehringer Mannheim). FragMitchell was based on these morphological ments were radioactively end-labeled uscriteria. In addition, morphological species ing Klenow and 32P-labeled nucleotides,
assignments were confirmed by application size-separated by electrophoresis through
of the discriminant function analyses de- 1.2-1.5% agarose gels, and visualized by
fined in Lamb (1983b), as applied to five autoradiography (Lansman et al., 1981).
shell characteristics measured in all speci- The digestion profiles proved informative
mens of mud turtles collected along the At- in the sense that they yielded restriction
lantic coast from the Carolinas through fragment length polymorphisms (RFLP's)
Florida. All specimens are deposited in The whose differences within and between K.
University of Georgia Museum of Natural baurii and K. subrubrum provisionally
History (UGAMNH 28567-28648) except could be interpreted as restriction site
those from Cohoke Mill Creek (Virginia) gains or losses.
which were donated to the Smithsonian
Data Analyses
Museum (USNM numbers 515120,515121,
515124-515127, 515212, and 515213).
Each mtDNA digestion profile was asWe extracted mtDNA from heart, liver, signed a letter code (Table 1). These letand muscle tissues following Lansman et ters were compiled for each individual into
al. (1981). Closed-circular mtDNA was di- a composite mtDNA haplotype. From the
HERPETOLOGICA
June 1998]
presence/absence matrixof restrictionsites
summarizing these haplotypes, sequence
divergences (Nei and Li, 1979) and genotypic and nucleotide diversities (Nei,
1987) were calculated.
Phenetic relationships among haplotypes were inferred from the genetic distance matrix using the neighbor-joining
(N-J) method (Saitou and Nei, 1987) as
implemented in PHYLIP (Felsenstein,
1991) and rooted by the mid-point criterion. We conducted parsimony analyses
from the presence/absence matrix of restriction sites using the heuristic search
option in PAUP (Swofford, 1990). Statistical support was based on 1000 bootstrap
pseudoreplicates. A parsimony network
was hand-generated using observed numbers of restrictionsite differences between
the mtDNA haplotypes. Outgroup taxa
were not employed to root the parsimony
networks,because other assayedspecies of
Kinosternidae (Walker et al., 1995, 1997)
proved too divergent in most of the
mtDNA digestion profiles to permit secure
scoring of restriction site changes.
RESULTS
The mtDNA restriction site differences
between K. baurii and some specimens of
K. subrubrum were minimal, so the data
were analyzed collectively. In total, the 14
informative restriction enzymes revealed
26 different mtDNA haplotypes:20 for K.
subrubrum and six for K. baurii (Table 1).
The mtDNA molecule was approximately
16.3 kilobases in length in both species,
with no evident size differences among individuals. A mean of 43 restriction sites
per individual was scored, reflecting 451
base pairs of recognition sequence or
about 2.8% of the mtDNA genome.
The gel digestion profiles were interpreted with respect to restriction site
changes by methods described in Avise
(1994). Fifty-nine of the 81 scored restriction sites were variable (Table 2), and 31
were informativephylogenetically(i.e., not
confined to a single individual). For the
pooled collection of samples, estimated
genotypic diversity was 0.927 and nucleotide diversity was 0.041. Most of this diversity stemmed from large differences be-
177
tween mtDNA genotypes in separate geographic regions.
Parsimony networks (Fig. 2; see also
legend to Fig. 3) and a neighbor-joining
tree (Fig. 3) for the mtDNA haplotypes
are based strictly on genotypic considerations and essentially agree in all major features. Four fundamental phylogenetic
groups (A-D), each showing a strong geographic orientation (Fig. 4), are evident.
Group A occurs in the western-most portion of the range of K. subrubrum; group
B occurs in the central portion of the
range of K. subrubrum in the Gulf coastal
states; group C includes K. subrubrum
from Atlantic coastal states north of Florida, plus all individuals of K. baurii (including those from the Florida peninsula);
and group D consists of all specimens of
K. subrubrum from the Florida peninsula.
The mean levels of genetic divergence estimated among haplotypes within each assemblage (0.000, 0.003, 0.006, and 0.008
for groups A, B, C, and D, respectively)
typically are much smaller than those between assemblages (0.071, 0.068, 0.057,
0.054, 0.032, and 0.038, respectively, for
the paired combinations A-B, A-C, A-D,
B-C, B-D, and C-D).
Intra-assemblage genetic variation differed considerably among the four genetic
groups. The largest numbers of mtDNA
haplotypes (seven and eight, respectively)
were observed in genetic groups B and C.
However, the highest values for genotypic
diversity (0.918) and nucleotide diversity
(0.013) occurred in the Florida peninsula
with turtles representing both the C and
D groups co-occurring there.
In peninsular Florida, all specimens assigned by morphology to K. subrubrum
belonged to mtDNA group D, and all
specimens morphologically referable to K.
baurii belonged to group C. However,
group C (with bootstrap support 99%: Fig.
3) also included all sampled turtles from
the Atlantic coastal states, regardless of
taxonomic status (K. baurii or K. subrubrum). Within the C group, specimens of
K. baurii from Florida differed consistently from those in Georgia and Virginia by
at least two restriction site changes (Fig.
2).
TABLE
tRestriction
Haplotype
BanI
code
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
subrl
subr2
subr3
subr4
subr5
subr6
subr7
subr8
subr9
subrlO
subrll
subrl2
subrl3
subrl4
subrl5
subrl6
subrl7
subrl8
subrl9
subr20
baur2l
baur22
baur23
baur24
baur25
baur26
2.-Presence
(1) versus absence (0) matrix of mtDNA restriction sites in Kinostemnon subrub
sites
BclI
BglI
1111100
11110
11
1111100
1111100
1111110
1111100
1111100
1111100
1111100
1111110
1111111
1111110
1111110
1101100
1101100
1101100
1101100
1111110
1111110
1111100
1111110
11100
11100
11100
11100
11100
11100
11100
11101
11101
11101
11101
11101
11101
11101
11101
11101
11101
11001
11101
1111100
11100
1111100
1111100
1111100
1111100
1111100
11100
11100
11100
11100
11101
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
11
10
11
11
11
11
11
11
11
BglII
00000
00000
00000
00000
00000
00000
00000
00000
11000
11000
11000
110 00
00000
1o0o1o00
00000
00000
10010
11100
11000
11000
11001
00000
00000
00000
00000
000o00
00000
Drall
EcoRI
11111110
11111110
11111110
01111110
11111110
11111110
11111100
11111100
10100101
10100101
10100101
10100101
10100100
101 00100
1010 0100
10100100
10100101
10100101
10100100
10100101
11111110
11111110
11111110
11111110
11111110
11111110
110
110
110
110
110
110
110
110
110
110
110
110
110
110
110
110
110
110
1
110
110
110
110
110
110
110
HindIl
111111100000000
111111100000000
111111100000000
111111100000000
111111100000000
111111100000000
111111100000000
111111100000000
101011111000000
101011111000000
101011111100000
10101111000000
111111110010000
111111110010000
111111110000000
111111110000000
101011111000000
10101111000000
010101100001110
101011111000000
111111100000000
111111100000000
110111100000000
110111100000000
110111100000001
110111100000000
Hindill
KpnI
11100
11100
11100
11100
01100
11100
11100
11100
10100
10100
10100
10 100
10101
10101
10101
10101
10100
10100
100 10
10100
11100
11100
11100
01100
11100
11100
1100
1100
1100
1110
1100
1100
1100
1100
1110
1110
1110
1110
1100
1101
1100
1100
1110
1110
1100
1110
1100
1100
0o0
1100
1100
1100
1100
NciI
10000
100000
11000
11000
11000
10000
11000
11000
10110
10110
10110
10110
10000
1000
0oo0
10110
10111
10111
10000
10110
10000
1000
10000
10000
10000
10000
179
HERPETOLOGICA
June 1998]
K.subrl
K.subr2
K.baur2l
HI
4K.baur22
0.002
K.subr6
A
K.subr4
group
.subr5
l/
K.subr3
99
6C
~~~~~~~~~~~~2
C
K.subr7
K.subr8
K.baur26
K.baur23
K.baur25
K.baur24
17
K.subrI2
18
K.subrl 1
1
13
D
1 00
K.subrl7
group
B
K.subr18
K.subr20
Kasubri 0
B
K.subrg
parsimony network estimating relationships among the composite mtDNA
haplotypes (numbered as in Table 1) scored in the
collections of K. baurii (indicated by asterisks) and
K. subrubrum. Slashes along branches are inferred
character state (restriction site) changes, and those
along branches connecting the four major genotypic
groups (A-D) represent the minimum numbers of
such changes between any representatives of these
respective groups.
FIG. 2.-Hand-generated
DISCUSSION
Genetic Variation and Phylogeographic
Patterns
In several respects, the levels and spatial
distributions of mtDNA variation in the
Kinosternon
subrubrum/baurii
complex
are remarkably similar to those reported
previously for two other species of kinosternid turtles in the southeastern United
States: the musk turtle, Sternotherus minor (Walker et al., 1995), and the stinkpot,
S. odoratus (Walker et al., 1997). First,
mtDNA variation is extensive. The genotypic diversity value (0.927) observed in
the collection of Kinosternon approximates
values reported within S. minor (0.859)
and S. odoratus (0.899) and the overall nucleotide diversity (0.041) in the assayed
Kinosternon complex surpasses such estimates within either of the species of Sternotherus examined (0.017 and 0.016, respectively).
168
K.subr16
group
D
K.subr3
K.subri4
K.subrl
5
K.subrl9
J
A
FIG. 3.-Neighbor-joining tree for mtDNA haplotypes (numbered as in Table 1) in mud turtles. The
tree is mid-point rooted and branch lengths are
drawn according to numbers of inferred restriction
site changes. A computer-generated parsimony network (not shown, but with consistency index 0.76)
essentially agreed in identifying all major mtDNA
groups, and yielded levels of bootstrap support
(>65%) that are shown here superimposed on the
neighbor-joining tree.
Second, most of the mtDNA haplotypes
observed in Kinosternon were localized
geographically, usually confined to a single
site or set of adjacent locales (Fig. 4). The
primary exceptions involved haplotype 19
in K. subrubrum, which was observed both
in southern Missouri and southern Louisiana, and haplotype 9 in this same species,
which was found in sites from northern
Georgia, Mississippi,
Alabama, and the
panhandle of Florida (Fig. 4). However,
about local population
any conclusions
structure in these turtles must remain
tempered
given the small numbers of
specimens assayed per locale.
Third, the numerous
mtDNA haplotypes in the species of Kinosternon align
phylogenetically into highly distinct groups
that also show a striking macro-geographic
180
HERPETOLOGICA
1
FAZ~~~~~~~~~~~~~~~~~~~~2
E
1
[Vol. 54, No. 2
~~~~~~~~~~~~O
2~~~~~~~~~
2
23
25D(C
FIG. 4.-Geographic
distributions of mtDNA haplotypes (numbered as in Table 1) in mud turtles and of
the four major mtDNA groups.
orientation (Fig. 4). Four genetically distinct assemblages (A-D) were observed in
the Kinosternon complex, compared to
two in S. minor and 3-4 in S. odoratus.
The geographic distributions of mtDNA
groups A, B, and D (Fig. 4) generally conform well to the described ranges of the
three conventionally recognized subspecies within K. subrubrum (Fig. 1), with the
exception that mtDNA group B apparently
does not extend into the Atlantic coastal
states that traditionally are included within
the range of K. s. subrubrum (Figs. 1, 4).
The overall distributions of the major
phylogeographic assemblages were remarkably similar for the species of Kinosternon and Sternotherus. In all cases (S.
minor, S. odoratus, and K. subrubrumi
baurii), the Atlantic coastal populations
were dramatically divergent in mtDNA
cornposition from those to the west and
along the upper Gulf coastal states. Furthermore, in both the Kinosternon complex and in S. odoratus, populations in
peninsular Florida displayed pronounced
mtDNA differences from those along the
Atlantic coast to the north and from those
in all Gulf coastal states to the west. Such
patterns, in general, complement those
observed in several species of freshwater
fish in the southeasternU.S. (Bermingham
and Avise, 1986), as well as in some terrestrial vertebrates (reviewed in Avise,
1996). Probably, numerous details in the
historicalpatternsof drainageisolationand
coalescence and their influences on gene
June 1998]
HERPETOLOGICA
181
C and D groups as these latter are from
one another. Finally, in contradistinction
to morphological patterns mentioned
above (Lovich and Lamb, 1995), samples
of K. s. hippocrepis (assemblage A) proved
Relationships between K. subrubrum and highly divergent in mtDNA composition
K. baurii
from K. baurii (assemblage C). Thus, with
Considerable discussion has centered on respect to matrilineal ancestry, K. subruthe topic of morphological and taxonomic brum appears to be genealogically paradistinction between K. subrubrum and K. phyletic (Neigel and Avise, 1986) in relabaurii. In an investigation of the subspe- tion to K. baurii (Fig. 3).
One conceivable explanation for the apcific status of a lower Florida Keys population of K. baurii, Iverson (1978) con- parent paraphyly is that the current mtcluded that the highly variable color pat- DNA restriction site data provide grossly
terns on the head and carapace were un- inadequate descriptions of matrilineal rereliable in distinguishing populations of K. lationships within the Kinosternon combaurii. According to Lamb (1983a,b),
plex, perhaps because of scoring difficulthese patterns also cause occasional misi- ties associated with inferences from digesdentifications with sympatric K. s. subru- tion profiles alone. However, this is unbrum. Lamb (1983a,b), using multivariate likely because we also have sequenced
discriminant function analyses of morpho- portions of the mtDNA control region
metric characters, concluded that the two from representative samples of K. subruspecies in Florida and along the Atlantic brum and K. baurii, and all conclusions
Coast could be separated reliably. These about the major mtDNA phylogeographic
analyses also demonstrated that the range groups within the complex are supported
of K. baurii extends into Georgia and fully (Walker et al., 1998). Alternatively,
South Carolina. A broader geographic sur- several competing evolutionary explanavey by Lamb and Lovich (1990) again in- tions might account for the paraphyletic
dicated that the two species were distin- pattern observed. Perhaps K. baurtii and K.
guishable along the Atlantic coast, and ex- subrubrum are "good" biological species,
tended the described range of K. baurii as is suggested by partial sympatry and the
into southeastern Virginia. However, a lat- morphometric differences, but K. baurii is
er assessment of samples of K. baurii a recent phylogenetic derivative of K. subagainst the western subspecies (hippocre- rubrum. Consistent with this possibility is
pis) of K. subrubrum failed to distinguish that K. baurii may have split recently from
these taxa by the same morphometric cri- Atlantic-like populations of K. subrubrum,
teria (Lovich and Lamb, 1995).
accounting for its overall mtDNA similarThe current mtDNA restriction site data ity to K. subrubrum in Atlantic coast drainplace all assayed samples morphologically ages, and that the species secondarily inreferable to K. baurii in the C matrilineal vaded the Florida peninsula, thus accountgroup, which extends from southern Vir- ing for its strong mtDNA divergence from
ginia to southern peninsular Florida. All K. subrubrum in that area. Such a history
individuals of K. subrubrum collected
also might account for the carapace and
from the Atlantic coastal states north of facial patterns wherein specimens of K.
Florida also belong to this mtDNA C baurii tend to be easier to differentiate
group. However, all peninsular Florida from K. subrubrum in Florida than along
specimens referable by morphology to K. the Atlantic coast. On the other hand, hissubrubrum belong to the sharply differ- torical introgressive hybridization in some
entiable mtDNA D assemblage. Further- other plant and animal taxa is known to
more, K. subrubrum across its broader produce occasional gene tree/species tree
geographic distribution to the west dis- discordances (Avise, 1994). Perhaps samplays at least two other matrilineal assem- ples of K. subrubrum from the Atlantic
blages that are at least as distinct from the coastal states are similar in mtDNA com-
flow (Bermingham and Avise, 1986; Swift
et al., 1985) have contributed to these observed genetic patterns in freshwater turtles.
182
[Vol. 54, No. 2
HERPETOLOGICA
position to samples of K. baurii because
has
gender-asymmetric
hybridization
moved mtDNA of K. baurii into K. subrubrum, or vice versa, in this geographic
area. Further evaluation of possibilities involving hybridization will require evidence
from nuclear genes. In any event, the
mtDNA data strongly indicate that any
such hybridization has not genetically
merged K. subrubrum and K. baurii in
peninsular Florida.
It is possible that populations of K. baurii from the Atlantic coastal states always
have been classified improperly as "K. subrubrum". If so, a revised range for K. subrubrum would include the Florida peninsula and all relevant Gulf coastal and interior states to the west, but would not extend northward along the Atlantic coast
which instead is occupied solely by K. baurii. The two species thus overlap only in
the Florida peninsula. Arguing against this
possibility is the morphological separation
between these two species in Atlantic
coastal regions (Lamb 1983a,b; Lamb and
Lovich, 1990; current study).
Another taxonomic revision imaginable
would be to consider the highly divergent
mtDNA groups A, B, and D within K. subrubrum to reflect the presence of distinct
phylogenetic (and, or, biological) species.
However, none of these or other such taxonomic alterations can as yet be recommended with great certitude, because the
genetic assays thus far are confined to a
single "gene" (mtDNA). In principle,
"gene trees" can differ from "species
trees" for several plausible historicaldemographic reasons, such as idiosyncratic
sorting of gene-tree lineages in transitional
populations that are large relative to internodal times as measured in organismal
generations (Maddison, 1995; Neigel and
Avise, 1986; Pamilo and Nei, 1988). As
emphasized by Avise and Ball (1990) and
Avise and Wollenberg (1997), a firm demarcation of taxonomic entities under either a biological species concept or a properly formulated phylogenetic species concept ideally requires concordant historical
inferences from multiple independent
genes or the traits that they encode.
Acknowledgmnents.-We thank the following for
help with the collections: R. Babb, I. Barak, V. Burke,
M. Case, A. Davis, S. Doody, S. Emms, M. Goodisman, M. Hare, C. Hobson, C. Holod, T. Ingstrom,
D. Jansen, T. Johnson, A. Jones, B. Mansell, P. Mayne, J. Mitchell, B. Nelson, G. Ortf, P. Prodohl, F.
Rose, C. Starlin, D. Stevenson, R. Vandevender, D.
Wilson, K. Wood, and personnel from the Avise laboratory and The University of Georgia Golf Course.
We also thank personnel from the National Fish
Hatcheries of Bo Ginn, Carbon Hill, Tupelo, McKinney Lake, Orangeburg, Warm Springs, and Welaka.
All specimens were collected under relevant state
permits. Work was supported by a National Institutes
of Health training grant to DeEtte Walker, by Department of Energy contract DE-FC09-96SR18546
between the U.S. Department of Energy and The
University of Georgia's Savannah River Ecology Laboratory, and by a National Science Foundation grant
to John Avise.
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Accepted: 17 July 1997
Associate Editor: David Green
APPENDIX
I
Collection Sites
K. subrubrum: Altamaha River basin-Oconee
River, Oconee Co., GA (n = 1); University of Georgia
Golf Course, Clarke Co., GA (n = 2); Apalachicola
River basin-Warm Springs National Fish Hatchery
ponds, Meriwether Co., GA (n = 2); Camel Lake
Road, east of SR 12, Liberty Co., FL (n = 1); Bayou
Lafourche drainage-Laurel
Plantation Road near
Thibodaux, LaFourche Parish, LA (n = 1); Bayou
Boeuf near Kraemer, LaFourche Parish, LA (n = 2);
Bayou L'Ourse drainage-bayou on SR 70, Assumption Parish, LA (n = 6); Bayou L'Ourse, Assumption
Parish, LA (n = 2); Coosa (Mobile) River basinJames Floyd State Park, Chattooga Co., GA (n = 3);
Withlacoochee River basin-Hwy 19, 10 km. north of
Crystal River, Citrus Co., FL (n = 1); Edisto River
National Fish Hatchery ponds,
basin-Orangeburg
Orangeburg Co., SC (n = 2); Mississippi River basin-cypress
swamp, Big Cane Conservation Area,
Butler Co., MO (n = 5); Ochlockonee River basinCounty Road 268 near intersection with County Road
65B, Gadsden Co., FL (n = 1); Apalachicola National
Forest Rd. 13, Liberty Co., FL (n = 1); Ogeechee
River basin-ponds
on Ft. Stewart Military Base,
Bryan Co., GA (n = 5); Pascagoula River basinLake Ivy, Clarkco State Park, Clark Co., MS (n = 3);
Pee Dee River basin-McKinney Lake National Fish
Hatchery ponds, Richmond Co., NC (n = 3); St.
Mark's River basin-Hwy 319 north of Tallahassee,
Leon Co., FL (n = 1); pond south of Tallahassee near
junction of Hwys. 319/263 and Hwy 363, Leon Co.,
FL (n = 2); Savannah River basin-Long
Creek,
Oglethorpe Co., GA (n = 1); Hwy 22 near Philomath,
Oglethorpe Co., GA (n = 1); ditch near Tillman, Jasper Co., SC (n = 1); Sopchoppy River basin-Apa-
184
HERPETOLOGICA
lachicola National Forest Rd 13, Wakulla Co., FL (n
= 1); Tickfaw River basin-swamp on Hwy 15 near
Pontchatook, Tangipohoa Parish, LA (n = 3); Tombigbee (Mobile) River basin-Carbon Hill National
Fish Hatchery ponds, Walker Co., AL (n = 1); Tupelo
National Fish Hatchery, Lee Co., MS (n = 2); Yellow
River basin-Yellow River Flood Plain, Hwy 90, Okaloosa Co., FL (n = 2); Shoal River at Hwy 90, Okaloosa Co., FL (n = 1); York River basin-Cohoke
Mill Creek, King William Co., VA (n = 3); Florida
coastal integrated drainages-Chassahowitzka Wildlife Management Area, Hernando Co., FL (n = 2);
Palm Beach,
Florida disjointed drainages-West
Palm Beach Co., FL (n = 2).
Road
K. baurii: Indian River basin-Maytown
[Vol. 54, No. 2
near Oak Hill, Volusia Co., FL (n = 1); Ogeechee
River basin-Bo Ginn National Fish Hatchery, Jenkins Co., GA (n = 1); St. John's River basin-Welaka
National Fish Hatchery, Putnam Co., FL (n = 1);
Hwy 441, Payne's Prairie, Alachua Co., FL (n = 1);
Co. Rd 346 near Hwy 121, Alachua Co., FL (n = 2);
Withlacoochee River basin-Hwy 471 south of Tarrytown, Sumter Co., FL (n = 1); Hwy 19, 10 km.
north of Crystal River, Citrus Co., FL (n = 1); Hwy
50, approximately 4 km west Sumter Co. line, Hernando Co., FL (n = 1); York River basin-Cohoke
Mill Creek, King William Co., VA (n = 4); Florida
coastal integrated drainages-Snapper Creek Canal,
Dade Co., FL (n = 4); Florida disjointed drainagesDade/Collier Training Airport, Collier Co., FL (n =
1).
Herpetologica, 54(2), 1998, 184-206
? 1998 by The Herpetologists' League, Inc.
THE PHYLOGENETIC POSITION OF THE MEXICAN BLACKTAILED PITVIPER (SQUAMATA: VIPERIDAE: CROTALINAE)
RONALD L. GUTBERLET,
JR.
Department of Biology, Box 19498, The University of Texas at Arlington, Arlington, TX 76019-0498, USA
ABSTRACT: Phylogenetic analyses of 52 morphological characters from Agkistrodon contortrix,
Atropoides nummifer, Bothriechis bicolor, B. lateralis, B. nigroviridis, B. schlegelii, Bothrops asper,
Cerrophidion godmani, Gloydius blomhoffii, Ophryacus undulatus, Porthidium melanurum, P. nasutum, and P. ophryomegas indicate that the Mexican black-tailed pitviper (Porthidium melanurum)
is more closely related to Ophryacus undulatus than it is to its congeners P. nasutum and P.
ophryomegas. To achieve a monophyletic classification, P. melanurum is placed in the genus Ophryacus.
Key words: Crotalinae; Morphology; Ophryacus; Phylogenetic systematics; Porthidium; Porthidium melanurum; Viperidae
RECENT investigations into relationships
among Neotropical pitvipers have led to
the generic recognition of several putatively monophyletic groups. In an unpublished
doctoral dissertation, Burger (1971) divided the morphologically diverse and potentially polyphyletic genus Bothrops into five
genera: Bothriechis, Bothriopsis, Bothrops,
Ophryacus, and Porthidium. Subsequently, Perez-Higareda et al. (1985) published
this taxonomic arrangement. Campbell
and Lamar (1989) adopted this classification but suggested that additional studies
into the relationships and generic limits of
these groups, especially Porthidium, were
needed.
Further study revealed that Porthidium
(sensu Burger, in Perez-Higareda et al.,
1985) is polyphyletic, and new genera
were proposed to rectify this unnatural
grouping. Werman (1992) erected the genus Atropoides, the jumping pitvipers, to
contain three of the 14 species formerly
included in Porthidium: A. nummifer, A.
olmec, and A. picadoi. Campbell and Lamar (1992) segregated an additional three
species of Porthidium into Cerrophidion,
the montane pitvipers: C. barbouri, C.
godmani, and C. tzotzilorum.
These revisions reduced the content of
Porthidium to eight species. Solorzano
(1994) later increased the number of species in Porthidium to nine with the description of P. volcanicum. Eight of these