Hydrobiologia 298: 15-44, 1995.
D. Belk, H. J. Dumont & C. Maier (eds), Studies on Large Branchiopod Biology and Aquaculture II.
©1995 Kluwer Academic Publishers.
15
Diagnosis and phylogeny of the New World Streptocephalidae
(Branchiopoda: Anostraca)
Alejandro M. Maeda-Martfnez1,3, Denton Belk2, Hortencia Obregon-Barboza l ,3 &
Henri 1. Dumont l
1 Laboratory of Animal Ecology, University of Ghent, K. L. Ledeganckstraat 35, B-9000 Ghent, Belgium
2 Biology Department, Our Lady of the Lake University of San Antonio, TX 78207-4666, USA
3 Current address: Centro de Investigaciones Biologicas del Noroeste, S. C, Division Biolog{a Marina, Apdo.
Postal 128, La Paz, Baja California Sur, Mexico
Key words: Streptocephalus, morphology, systematics, North America, new species, cladistics, fairy shrimp
Abstract
We present an updated diagnosis of 13 Streptocephalus species of North America. Three new species are included.
A key to the species is provided.
The phylogeny of the group is discussed on the basis of (1) a systematic approach (Maeda-Martinez et aI., 1995;
this volume), which considers the entire distal antennal outgrowth, the frontal appendage, and the morphology of
the ovaries as essential in defining different genetic lineages or species-groups, and (2) a cladistic analysis. We
suggest that of nine monophyletic groups, three are represented in both the Old and New World. Thus, contrary
to former disparsalist hypotheses, we argue that the New World species represent relict forms of ancestral groups
fragmented by continental drift (vicariance model).
Introduction
In the New World, 10 species of Streptocephalus are
recognized as valid, viz. S. similis Baird, 1852, S. texanus Packard, 1871, S. sealii Ryder, 1879, S. dorothae
Mackin, 1942, S. antillensis Mattox, 1950, S. mackini
Moore, 1966, S. linderi Moore, 1966, S. moorei Belk,
1973, S. kargesi Spicer, 1985, and S. woottoni Eng,
Belk & Eriksen, 1990 (Creaser, 1930; Moore, 1958,
1966; Belk, 1975; Spicer, 1985; Eng et al., 1990). We
add three new species. Two are from Mexico, one of
these previously reported by Maeda-Martinez (1991)
from Coahuila, the other from San Luis Potosi, and the
third one is from Texas, USA.
Comprehensi ve studies on the diagnosis of the New
World streptocephalids were made by Packard (1883),
Daday (1910), Creaser (1930), and Moore (1966).
Beside the former authors, keys to species have been
presented by Mackin (1942), Dexter (1959), and Belk
(1975), and for taxa of the USA by Pennak (1953,
1978,1989).
Only few authors have treated the phylogeny
of the group. On the basis of hybridization tests,
Wiman (1979a, b) discussed species relationships
and speciation. Because of the extensive interfertility between Streptocephalus mackini and other species,
Wiman(1979a) suggested this species may represent
a primitive stock from which the other species were
derived. Also, Wiman proposed that the American
species group is probably derived and diversified
from a streptocephalid stock introduced from Africa
(Wiman, 1979a). On the other hand, Spicer (1985),
used cladistics on morphological characters, to present
a phylogenetic analysis of the North American Streptocephalus. The cladogram of Spicer (1985), however,
leads to two controversial positions: first, in disagreement with Wiman's proposal, S. mackini is far from
representing the ancestral stock, and second, a close
relationship seems to exist between two extremely different species, S. kargesi and S. moorei.
Dealing with the biogeography of the whole genus,
Belk (1984) proposed that modern North American
and African species were derived from a common
Laurasian stock. This thesis is supported by the absence
of streptocephalids in South America and Australia
(Belk, 1984). Banarescu (1990) proposed, besides
the former explanation, an alternative by accepting
an African origin and subsequent dispersal to Europe,
D. Belk, H. J. Dumont & C. Maier (eds), Studies on Large Branchiopod Biology and Aquaculture II.
©1995 Kluwer Academic Publishers.
15
Diagnosis and phylogeny of the New World Streptocephalidae
(Branchiopoda: Anostraca)
Alejandro M. Maeda-Martfnez1,3, Denton Belk2, Hortencia Obregon-Barboza l ,3 &
Henri 1. Dumont l
1 Laboratory of Animal Ecology, University of Ghent, K. L. Ledeganckstraat 35, B-9000 Ghent, Belgium
2 Biology Department, Our Lady of the Lake University of San Antonio, TX 78207-4666, USA
3 Current address: Centro de Investigaciones Biologicas del Noroeste, S. C, Division Biolog{a Marina, Apdo.
Postal 128, La Paz, Baja California Sur, Mexico
Key words: Streptocephalus, morphology, systematics, North America, new species, cladistics, fairy shrimp
Abstract
We present an updated diagnosis of 13 Streptocephalus species of North America. Three new species are included.
A key to the species is provided.
The phylogeny of the group is discussed on the basis of (1) a systematic approach (Maeda-Martinez et aI., 1995;
this volume), which considers the entire distal antennal outgrowth, the frontal appendage, and the morphology of
the ovaries as essential in defining different genetic lineages or species-groups, and (2) a cladistic analysis. We
suggest that of nine monophyletic groups, three are represented in both the Old and New World. Thus, contrary
to former disparsalist hypotheses, we argue that the New World species represent relict forms of ancestral groups
fragmented by continental drift (vicariance model).
Introduction
In the New World, 10 species of Streptocephalus are
recognized as valid, viz. S. similis Baird, 1852, S. texanus Packard, 1871, S. sealii Ryder, 1879, S. dorothae
Mackin, 1942, S. antillensis Mattox, 1950, S. mackini
Moore, 1966, S. linderi Moore, 1966, S. moorei Belk,
1973, S. kargesi Spicer, 1985, and S. woottoni Eng,
Belk & Eriksen, 1990 (Creaser, 1930; Moore, 1958,
1966; Belk, 1975; Spicer, 1985; Eng et al., 1990). We
add three new species. Two are from Mexico, one of
these previously reported by Maeda-Martinez (1991)
from Coahuila, the other from San Luis Potosi, and the
third one is from Texas, USA.
Comprehensi ve studies on the diagnosis of the New
World streptocephalids were made by Packard (1883),
Daday (1910), Creaser (1930), and Moore (1966).
Beside the former authors, keys to species have been
presented by Mackin (1942), Dexter (1959), and Belk
(1975), and for taxa of the USA by Pennak (1953,
1978,1989).
Only few authors have treated the phylogeny
of the group. On the basis of hybridization tests,
Wiman (1979a, b) discussed species relationships
and speciation. Because of the extensive interfertility between Streptocephalus mackini and other species,
Wiman(1979a) suggested this species may represent
a primitive stock from which the other species were
derived. Also, Wiman proposed that the American
species group is probably derived and diversified
from a streptocephalid stock introduced from Africa
(Wiman, 1979a). On the other hand, Spicer (1985),
used cladistics on morphological characters, to present
a phylogenetic analysis of the North American Streptocephalus. The cladogram of Spicer (1985), however,
leads to two controversial positions: first, in disagreement with Wiman's proposal, S. mackini is far from
representing the ancestral stock, and second, a close
relationship seems to exist between two extremely different species, S. kargesi and S. moorei.
Dealing with the biogeography of the whole genus,
Belk (1984) proposed that modern North American
and African species were derived from a common
Laurasian stock. This thesis is supported by the absence
of streptocephalids in South America and Australia
(Belk, 1984). Banarescu (1990) proposed, besides
the former explanation, an alternative by accepting
an African origin and subsequent dispersal to Europe,