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Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 56 (2): 839-844, June 2008
Resurrection of the name Albula pacifica (Beebe, 1942) for the shafted
bonefish (Albuliformes: Albulidae) from the eastern Pacific
Edward Pfeiler
Centro de Investigación en Alimentación y Desarrollo, A.C., Unidad Guaymas, Apartado Postal 284, Guaymas,
Sonora C.P. 85480, México. Phone: +52-622-221-6533; epfeiler@asu.edu
Received 23-XI-2007. Corrected 01-III-2008. Accepted 11-III-2008.
Abstract: The name Albula nemoptera (Fowler, 1911) is currently applied to the Shafted, or Threadfin, Bonefish
(Albuliformes: Albulidae) inhabiting the tropical coastal waters of both the western Atlantic and eastern Pacific.
In the present paper I provide a brief review of the taxonomy and nomenclature of A. nemoptera, and argue that
the available morphological, biogeographical and molecular evidence supports resurrecting the name A. pacifica
(Beebe, 1942) for the population of A. nemoptera from the eastern Pacific. Rev. Biol. Trop. 56 (2): 839-844.
Epub 2008 June 30.
Key words: cryptic species, Elopomorpha, mitochondrial DNA, molecular systematics, speciation.
The Shafted, or Threadfin, Bonefish from
the tropical coastal waters of the western
Atlantic and eastern Pacific (type locality:
Santo Domingo, Dominican Republic) is cur-
rently recognized as a single species, Albula
nemoptera (Fowler, 1911). Although A. nem-
optera originally was assigned to the genus
Dixonina Fowler 1911, Rivas and Warlen
(1967) proposed that Dixonina should be
placed into the synonymy of Albula Scopoli,
1777, an arrangement which generally has been
followed for forty years (Nelson et al. 2004),
and which recently has received support from
mitochondrial DNA studies (Pfeiler et al. 2006,
Bowen et al. 2008).
In the eastern Pacific, A. nemoptera is
distributed from Ecuador to the outer Pacific
coast of Baja California Sur (BCS), Mexico
(Castro-Aguirre et al. 1999, Pfeiler et al.
2002, Robertson and Allen 2006). Although
present in the southern Gulf of California at
Mazatlán, Sinaloa (Rivas and Warlen 1967,
van der Heiden and Findley 1990), and at La
Paz, BCS (Balart et al. 1995), the apparent
lack of collection records from the central and
northern gulf (Pfeiler et al. 2002) indicates that
it may be rare, or absent, in this region. In the
western Atlantic and Caribbean, A. nemoptera
is found from the Greater Antilles, Panama
and the northern coast of South America, south
to Brazil (Rivas and Warlen 1967, Lopes and
Sampaio 2002, Loebmann and Vieira 2005).
In 1942, William Beebe described the
Shafted Bonefish from the eastern Pacific as
a distinct species, Dixonina pacifica (type
locality: Port Culebra, Costa Rica). Beebe’s
(1942) material included 19 specimens from
the Pacific, but published records of only two
Atlantic specimens (Fowler 1911, Metzelaar
1919) were available at that time for mor-
phological comparisons. Hildebrand (1963)
did not recognize D. pacifica, and placed
it into the synonymy of D. (= Albula) nem-
optera. Although Berry (1964) argued in sup-
port of retaining the name A. pacifica, Rivas
and Warlen (1967), after conducting a more
detailed morphological analysis of Atlantic and
Pacific specimens, concluded that there was
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Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 56 (2): 839-844, June 2008
no basis for separating them as two species.
Although the name A. nemoptera has been
generally accepted as applying to both Atlantic
and Pacific populations of the Shafted Bonefish
(van der Heiden and Findley 1990, Bussing and
López 1993, Balart et al. 1995) I argue here
that there is now sufficient evidence for resur-
recting the name A. pacifica for the population
from the eastern Pacific.
Morphological Comparisons: Because of
the historical importance of the work of Rivas
and Warlen (1967) regarding the placement of
A. pacifica into the synonymy of A. nemoptera,
a brief summary of their findings is provided
here. Rivas and Warlen (1967) analyzed 23
morphometric characters, expressed as percent
standard length (SL), in nine Atlantic and seven
Pacific specimens of juvenile and adult A.
nemoptera of similar mean length (246 and 205
mm SL, respectively). In addition, 14 meristic
comparisons were conducted on 20–28 Atlantic
specimens and 16–21 Pacific specimens. The
morphological differences between individu-
als from Atlantic and Pacific populations were
found to be slight, with overlap seen in most
characters. There was, however, one exception.
Table 2 of Rivas and Warlen (1967) shows that
mean lower caudal-fin lobe length was 20.0%
SL (range 18.7–20.8%) in the Atlantic speci-
mens and 22.2% (21.2–23.0%) in Pacific speci-
mens. Although no overlap was seen, this was
apparently overlooked, as Rivas and Warlen
(1967: 254) stated that of the five characters
that showed significant differences among indi-
viduals of the two populations (dorsal- and
anal-fin heights, length of last dorsal-fin ray,
and upper and lower caudal-fin lobe lengths)
all showed broad overlap. Inter-population dif-
ferences were also seen in the number of gill
rakers, but this was attributed to difficulties in
counting gill rakers in larger specimens, and
the mean size differences among the Atlantic
and Pacific samples. Rivas and Warlen (1967)
concluded that the slight differences noted in
a few morphological characters among the
Atlantic and Pacific specimens did not war-
rant separating them into two species, or even
subspecies. At that time, however, the extent of
cryptic speciation in the genus Albula revealed
by molecular studies (Shaklee and Tamaru
1981, Colborn et al. 2001) was not known.
There is also some evidence that the shape
of the otoliths (sagittae) differ among individu-
als from Atlantic and Pacific populations of A.
nemoptera, although more individuals need to
be examined for confirmation. Frizzell (1965)
first figured and described a pair of otoliths,
14.3 mm in length, obtained from a specimen
of A. nemoptera from the Caribbean coast of
Colombia. The sagittae obtained from a speci-
men of A. nemoptera collected near Acapulco
in the eastern Pacific (Fig. 1) were of similar
size (12.3-12.5 mm) and showed clear differ-
ences when compared to those of Frizzell’s
Caribbean specimen. The most prominent dif-
ference was a pronounced dome on the dorsal
margin of each sagitta in the region of the
vertical midline in the Pacific specimen (Fig.
1). Frizzell (1965) mentioned that a “tiny
dome” was present in the same region of the
sagittae in the Caribbean specimen, but the
dorsal outline of the sagittae in that specimen
was relatively flat (see Pl. 4, Fig. 5a and 5b of
Frizzell 1965).
Molecular Evidence for Cryptic Species:
As mentioned above, since the work of Rivas
and Warlen (1967) molecular methods have
revealed an increasing number of marine organ-
isms that show ancient genetic divergences
with little or no change in external morphol-
ogy (Rocha-Olivares et al. 1999, Quattro et al.
2001, 2006). Cryptic speciation is especially
prominent in the bonefishes, in which few
morphological differences are evident in lin-
eages that have been separated for an estimated
20–30 million years (Shaklee and Tamaru
1981, Colborn et al. 2001, K. Hidaka et al.,
2008). Where morphological characters have
been found that can supposedly discriminate
among bonefish species, they have not always
proved reliable and can lead to misidentifica-
tions (Pfeiler et al. 2006). In the two sibling
species of bonefishes from the A. vulpes com-
plex that inhabit the eastern Pacific (Albula sp.
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Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 56 (2): 839-844, June 2008
A and C), analyses of 16 morphometric and
8 meristic characters (N = 7 for each species)
were unable to distinguish between the two
lineages which show a mitochondrial DNA
cytochrome b (Cytb) divergence of ~5.3% (E.
Pfeiler et al., unpublished). Although the appli-
cation of molecular methods to define species
boundaries is controversial, these methods can
be especially useful in taxa such as the bon-
efishes where morphological characters alone
provide poor resolution (Wiens and Penkrot
2002). In light of the recent findings on cryptic
speciation in the bonefishes, therefore, it is not
surprising that Rivas and Warlen (1967) found
only slight differences in morphology among
their Atlantic and Pacific specimens.
Because gene flow among western Atlantic
and eastern Pacific populations of A. nemoptera
has been restricted by the Isthmus of Panama
for about 3.5 million years (Coates et al. 1992),
the expected genetic divergence among the two
populations can be estimated based on results
obtained from known sister species of marine
fishes separated by the Isthmus (geminate spe-
cies). These predictions can then be used to
address the issue of whether the Atlantic and
Pacific populations of A. nemoptera should be
considered separate species. Molecular clock
Fig. 1. Medial views of left sagitta (A) and right sagitta (B) from an adult specimen (283 mm SL) of Albula nemoptera
(=A. pacifica) collected in January, 2006 near Laguna Chautengo, ~80 km SE of Acapulco, Guerrero, Mexico [16°31’26˝N,
99°16’36˝W; catalog no. CIAD 06-203 (Centro de Investigación en Alimentación y Desarrollo, A.C. -Unidad Guaymas,
Sonora)]. Arrows show the prominent dome on the dorsal margin. Scale bar = 2 mm.
Fig. 1. Vistas mediales de la sagitta izquierda (A) y la sagitta derecha (B) de un espécimen adulto (283 mm longitud están-
dar) de Albula nemoptera (=A. pacifica) recolectado en enero de 2006 cerca de Laguna Chautengo, ~80 km al sureste de
Acapulco, Guerrero, México [16°31’26˝N, 99°16’36˝W; número de catalogo CIAD 06–203 (Centro de Investigación en
Alimentación y Desarrollo, A.C. -Unidad Guaymas, Sonora)]. Las flechas demuestran el domo prominente en el margen
dorsal. Línea de escala = 2 mm.
A
B
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Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 56 (2): 839-844, June 2008
estimations for the Cytb gene in bony fishes
are roughly 1.0−1.5% sequence divergence
per million years (Bermingham et al. 1997,
Banford et al. 2004). If we assume that Atlantic
and Pacific populations of A. nemoptera were
initially isolated by the Isthmus of Panama
(but see Knowlton et al. 1993 and Marko
2002), expected sequence divergence between
the two populations is ~3.5−5.3%. The mean
genetic divergence (uncorrected p distance and
Kimura’s [1980] 2-parameter [K2P] distance)
between A. nemoptera from the Pacific and the
previously unidentified Albula sp. E (Colborn
et al. 2001) from Bahia, Brazil is ~4% (Pfeiler
et al. 2006, Bowen et al. 2008), within the
expected range, and also within the range of
Cytb divergences reported for sister species of
fishes (Johns and Avise 1998).
The accumulated evidence indicates that
Albula sp. E, genetically characterized by tissue
samples from a Brazilian fish market, actually
represents the Atlantic A. nemoptera. First, the
Pacific A. nemoptera is linked to the Atlantic
Albula sp. E by a unique amino acid substitu-
tion in the translated Cytb gene segment which
is absent from all other members of the genus
Albula (Pfeiler et al. 2006). Second, molecular
phylogenetic trees constructed with a variety
of assumptions consistently show that A. nem-
optera from various eastern Pacific localities
(Mexico, Costa Rica, and El Salvador) and
Albula sp. E are sister lineages (Pfeiler et al.
2006, Bowen et al. 2008). Third, the occur-
rence of A. nemoptera has been confirmed
in the region of Bahia, Brazil, where the tis-
sue samples for Albula sp. E. were obtained
(Lopes and Sampaio 2002). However, voucher
specimens of Albula sp. E are not yet avail-
able (Colborn et al. 2001, Pfeiler et al. 2006),
as Atlantic A. nemoptera is rare and directed
efforts to collect specimens have not been
successful. Vouchers are desirable to link the
morphological identification (Atlantic A. nem-
optera) and genetic characterization (Albula
sp. E), but this lack does not directly impact
the morphological, biogeographic, and genetic
arguments for resurrecting A. pacifica as the
proper name for the form inhabiting the eastern
Pacific. In particular, all genetic analyses show
that that form is millions of years divergent
from other members of the genus Albula.
In reference to Hildebrand’s (1963) place-
ment of A. pacifica (as D. pacifica) into
the synonymy of A. nemoptera, Berry (1964)
stated “...once a specific name has been pro-
posed that distinguishes a geographically iso-
lated form from its congener, it is usually
better (certainly in this instance) to retain the
name until adequate material is available and
adequate assessment is made to properly define
the relationship”. The molecular evidence now
available, indicating that cryptic speciation is
widespread in the bonefishes, would certainly
cast doubt on whether a purely morphological
comparison of geographically isolated bon-
efish populations is sufficient to adequately
define relationships. In addition, the evidence
presented here, including slight morphological
differentiation, strongly indicates that Atlantic
and Pacific populations of A. nemoptera are
indeed valid sister species which have diverged
to an extent similar to other recognized sis-
ter species now geographically isolated by
the Isthmus of Panama. On these grounds,
and considering that reproductive isolation
is ancient and absolute, I propose that the
name A. pacifica (Beebe, 1942) be reinstated
for the population of A. nemoptera from the
eastern Pacific. Suggested common names are
Shafted Bonefish for A. pacifica and Threadfin
Bonefish for the western Atlantic A. nemoptera
(Bowen et al. 2008).
The first published record of A. pacifica
(as D. nemoptera) is apparently the report of
Myers (1936) on a specimen (USNM 75547)
obtained from Acapulco, Guerrero, Mexico
(Beebe 1942). This same specimen was later
figured by Hildebrand (1963: 143, Fig. 24).
Beebe (1942) also considered the illustration
of a specimen of a Shafted Bonefish from the
southern Gulf of California incorrectly labeled
as A. vulpes (Kumada and Hiyama 1937: 47, Pl.
5; also see Walford 1939), as the second pub-
lished record of A. pacifica. Albula pacifica (as
A. nemoptera) has also been figured by Bussing
and López (1993: 37), Allen and Robertson
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Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 56 (2): 839-844, June 2008
(1994: 41) and Robertson and Allen (2006).
The holotype of Dixonina (=Albula) paci-
fica, originally deposited in the Department of
Tropical Research of the New York Zoological
Society (Beebe 1942, Mead 1958), is now
housed at the California Academy of Sciences,
San Francisco, California, USA (catalog no.
SU 46486).
ACKNOWLEDGMENTS
I am grateful to B.W. Bowen and L.T.
Findley for kindly reviewing and suggesting
improvements to an earlier draft of the manu-
script. I also thank B. Bitler, J. Egido-Villarreal,
J.-P. Gallo-Reynoso, T.A. Markow, J. Pugh, R.
Ulloa and T. Watts for their help. Much of the
molecular research on eastern Pacific bon-
efishes described herein was supported in part
by NSF grant DEB-0346773 to T.A. Markow.
RESUMEN
El nombre Albula nemoptera (Fowler, 1911) se
aplica actualmente a las poblaciones del macabí de hebra
(Albuliformes: Albulidae) de las aguas costeras tropicales
del Atlántico Occidental y el Pacifico Oriental. En este
artículo se presenta una revisión breve de la taxonomía y
nomenclatura de A. nemoptera, y se sugiere que la eviden-
cia morfológica, biogeográfica y molecular apoya el rees-
tablecimiento del nombre A. pacifica (Beebe, 1942) para la
población de A. nemoptera del Pacifico Oriental.
Palabras clave: ADN mitocondrial, Elopomorpha, espe-
ciación, especies crípticas, sistemática molecular.
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