A Review of the North American Freshwater Snail Genus Pyrgulopsis

NUMBER 554 83
and southeastern Arizona form a clade (Clade 3) defined by
three transformations, including unique synapomorphies involving
loss of penial lobe (30-3) and terminal gland (32-3).
Other unique synapomorphies defining sub-clades within this
group are an enlarged ventral gland (43-2) and superficial
position of ventral gland (44-1). Members of this clade usually
have globose shells, and their penes are ornamented by a
ventral gland, sometimes accompanied by a large dorsal gland.
A second western clade (Clade 4) is comprised of 10 species
from eastern California, northern Arizona, and Snake River
environs of Wyoming, Idaho, and Oregon; and includes all
members of the subgenus Natricola sensu Gregg and Taylor
(1965). This group is defined by five synapomorphies, of which
only one, presence of a dot-like Dgl penial gland, is unique;
this character is transformed in advanced members of this
clade. Other defining characters are homplasious, and include a
strong ventral callus on the operculum (10-1), and three
features relating to Dgl (37-1, 38-2, 40-1). There is extensive
parallelism in penial and female genitalic character transformations
between this clade and that discussed below. Members of
this group often are large, have ovate-conic shells, and have
penes ornamented by terminal gland, Dgl, and sometimes Dg2
and/or Dg3.
A third western clade (Clade 5), comprised of 18 species
from various drainages, closely approximating the "Ffontelicella].
californiensis series" of Taylor (1987), is defined by
five character-state transformations. Three of these (33-1,34-1,
35-1) are associated with the unique occurrence of a penial
gland (Pg) in this clade. The other two, involving a strong
ventral callus on operculum (10-1) and loss of anterior capsule
gland vestibule (48-0), are homoplasious. Within this group,
sub-clades are defined by die following unique or near-unique
character-state transformations: proximally bifurcate penial
gland (35-2, one parallel within this clade), Dgl a short strip
(36-2), multiple minor dorsal glands (42-2, paralleled by two
species), posterior position of ovary (46-1, parallel by one
species within this clade), multiple ventral glands (43-2), and
elongate bursa copulatrix (52-1, two parallels and one reversal).
Members of this group have globose to elongate-conic shells
and penes ornamented by a terminal and penial gland, often
accompanied by one or more dorsal glands.
The 17 Western American species having a relatively simple
penis (ornamented solely by terminal gland) do not comprise a
monophyletic group and, in general, are poorly resolved on the
cladogram. Four globose-shelled species from southern Nevada
(carinifera, nanus, fairbanksensis, isolata) are basally
placed on the cladogram, but are not a well-defined group; and
an assemblage of eight species scattered throughout the West,
approximating the "F[ontelicellaJ. stearnsiana series" of
Taylor, 1987), forms an unsupported polytomy. On the other
hand, two small groups of species are more strongly supported.
One pair from Gila River drainage of Arizona (bacchus, sola)
is defined by a small penis (26-1, unique synapomorphy),
bifurcate penial lobe (paralleled in one species), and simple
terminal gland on penis (32-0, a homoplasious reversal). A
second group, comprised of three highly disjunct species from
internal drainage of northern Mexico (brandi), Amargosa River
drainage (amargosae) and lower Snake River drainage (bruneauensis);
is defined by three character-state transformations:
weak ventral operculum attachment scar (9-0, homoplasious),
penial filament (28-1, paralleled in one species), and bursal
duct positioned lateral to albumen gland (59-0, homoplasious).