Phylogenetic systematics of Reticulidia Brunckhorst, 1990 (Mollusca, Nudibranchia), with the description of a new species from the tropical Indo-Pacific

10 Pages·2002·7.9 MB·English

by  Angel Valdes

Phylogenetic Systematics oe Reticulidia
Brunckhorst, 1990 (Mollusca,
Nudibranchia), with the Description oe a
New Species erom the Tropicae
Indo-Pacieic
/
Angel Valdes^ and David W. Behrens^
ABSTRACT. The genus Reticulidia includes three previously described species, R. halgerda and R. fungia
from the tropical Indo-Pacific, and R. gofasi from the Atlantic. A new species, R. suzanneae, is described
onthe basis ofspecimenscollectedfromtheIndianOceancoastofThailand.Thisspeciesisdistinguishable
from the other species by having an orange external coloration with circular black spots and the bursa
copulatrix smallerthan the seminal receptacle.
Aphylogenetic analysis ofReticulidia shows thatR. gofasiisthe sistertaxontotheIndo-Pacificspecies,
and a vicariant event probably produced this pattern. Reticulidia suzanneae is a derived species within
Reticulidia and is the sister taxon to R. fungia. Reticulidia is a monophyletic group supported by three
synapomorphies related to the shape ofthe buccal bulb, the oral glands, and the esophageal connection.
The dorsal ridges, which were used by other authors to define this genus, are absent in R. gofasi and
therefore their presence is a synapomorphy ofthe Indo-Pacificclade.
INTRODUCTION ticulidia to be a monophyletic group, supportedby
a single synapomorphy, the presence ofradially ar-
The genus Reticulidia was described by Brunck- ranged glandular discs on the buccal mass. How-
horst (1990) to include a single described speciesof ever, these authors did not propose a hypothesis of
Indo-Pacific Phyllidiidae, R. halgerda Brunckhorst
the phylogenetic relationships within Reticulidia.
and Burn, 1990. This species is characterized by The present paper examines the phylogenetic re-
having smooth reticulate ridges on the dorsum and lationships ofmembers ofReticulidia and describes
rraydnigaelallyoarrbruacnagledbugllbanodnultahre bduicsccsalwmiatshsi.nAthseecpohna-d a new species collected from the Andaman Sea,
Thailand. Previously described species are studied
species of the genus, R. fungia, was subsequently
here again in order to describe characters used in
introduced by Brunckhorst and Gosliner (in
the phylogenetic analysis. Additionally, the phylo-
Brunckhorst, 1993), also from the tropical Indo-
genetic hypothesis is used to further understandthe
Pacific. Separationofthesetwospecieswasjustified biogeographyofthe genus Reticulidia andthemost
onthe basis ofdifferencesintheexternalcoloration
likely speciation patterns within this group.
(Brunckhorst, 1993). Later, Valdes and Ortea
(1996) described a third species of this genus, coL MATERIALS AND METHODS
lected from western Atlantic seamounts, between
76 and 340 m depth. This new species, R. gofasi ThematerialexaminedisdepositedintheNaturalHistory
Valdes and Ortea, 1996, is remarkably different MuseumofLosAngelesCounty(LACM),theDepartment
from the two Indo-Pacific members ofthe genus in of Invertebrate Zoology and Geology of the Galifornia
having dorsal conical tubercles, rather than dorsal Academy ofSciences (GASIZ), and the MuseumNational
ridges. The two Indo-Pacific species are sympatric, d’Histoire Naturelle, Paris, France (MNHN).
whereas R. gofasi is isolated by continental land Specimens were dissected by dorsal incision. Their in-
masses. ternal featureswereexamined anddrawnunderadissect-
Valdes and Gosliner (1999), based on a phylo- ingmicroscopebyusingacameralucida.Specialattention
genetic analysis ofthe radula-less dorids,foundRe- was paid to the morphology of the reproductive and di-
gestive systems. Features of living animals were recorded
from photographs or from notes ofcollectors.
1. Natural History Museum of Los Angeles County, To calculate the most parsimonious phylogenetic tree,
900ExpositionBoulevard,LosAngeles,California90007. data were analyzed with Phylogenetic analysis usingpar-
E-mail: [email protected]. simony (PAUP), Version4.0b8 (Swofford,2001) byusing
2. CaliforniaAcademyofSciences,DepartmentofInver- the exhaustive algorithm. Characters were polarized by
tebrateZoologyandGeology,GoldenGatePark,SanFran- using the outgroup selection of the genera Phyllidia Cu-
cisco, California 94118. E-mail: [email protected]. vier, 1797 [Phyllidia varicosa Lamarck, 1801) and Phyl-
Contributionsin Science, Number 492, pp. 1-10
NaturalHistoryMuseum ofLos Angeles County, 2002
2 Contributionsin Science, Number492 Valdes and Behrens: Phylogeny ofReticulidia
Contributions in Science, Number 492 Valdes and Behrens: Phyiogeny ofReticulidia 3
lidiella Bergh, 1869 {Phyilidieila pustulosa [Cuvier, almostrounded. Fromitsdistalportionemergesthe
1804]), and subsequent analysis with PAUP. This out- postampulary duct, which divides into the prostate
group selection was made on the basis of the study by and a long oviduct. The prostate is wide, long, and
Valdes and Gosliner (1999), where the clade containing convoluted, distally narrowing and expanding
PhyllidiaandPhyilidieilawashypothesizedtobethesister
again into the long muscular ejaculatory portion.
tfaorxmoantitoonReotnicPuhlyildliiad,iawhaincdhPhiysialidmioeniolpahwyalsetoibctagirnoeudp.frIonm- The distal portion of the deferent duct opens into
the literature (Brunckhorst, 1993; Valdes and Gosliner, a short, common atrium with the vaginal duct. The
1999) andnewlyexaminedspecimens(Table 1).ABremer penial hooks have a long and robust pointed cusp
support analysis (Bremer, 1994) was carried out to esti- and a narrow base (Fig. 2C). They are about 70
matebranchsupport. SeeKitchingetal. (1998)forathor- [xm long. The vaginal duct opens into the bursa
ough explanation of the advantages of Bremer’s method copulatrix. The bursa copulatrix is oval and con-
in morphological data analyses. Synapomorphies were nects to the seminal receptacle by a short duct.
identified by thecharactertrace optioninMacClade,Ver- Near the seminal receptacle this duct is joined by
sion 4.0 (Maddison and Maddison, 2000).
the uterine duct, which enters the female gland
SYSTEMATICS mass. The bursa copulatrix is about five times as
large as the oval seminal receptacle.
Genus Reticulidia Brunckhorst GEOGRAPHIC RANGE. This species is known
Reticulidia Brunckhorst, 1990:567-568. Type spe- from the central and western Pacific Ocean (includ-
cies: Reticulidia halgerda Brunckhorst and Burn, ing Fiji and the Marshall Islands), from eastern
1990, by original designation. Australia to Taiwan (Brunckhorst, 1993).
REMARKS. The anatomy of this species has
DIAGNOSIS. Medium-sized phyllidiid nudi- been studied byBrunckhorst(1993) andValdesand
branchs with the dorsum normally coveredwith ir- Gosliner (1999). The reproductive system of the
regular ridges or exceptionally conical tubercles. specimen examined here is very similarto thosede-
Buccal mass with several radially arranged glan- scriptions and no substantial differences have been
4ular discs (synapomorphy). Esophagusconnecting found.
into the dorsal surface of the rounded buccal bulb According to Brunckhorst (1993), this species
(synapomorphies). Reproductive system similar to differs from R. fungia in lacking a bluish back-
that of other phyllidiid nudibranchs. ground coloration and havingnarrowerridges. An-
atomical differences found in this study include a
Reticulidia halgerda Brunckhorst shorter atrium and the presence of two ducts, in-
and Burn, 1990 stead of one, connecting to the bursa copulatrix of
Figures lA, 2A-C R. halgerda. In addition, the penial hooks of R.
Reticulidia halgerda Brunckhorst and Burn in halgerda are very large, about 70 |xm long, with a
Brunckhorst, 1990:570-575, figs. 2A-C, 3-7. robust cusp and a short base, whereas those of R.
fungia are smaller and have a more delicate,curved
MATERIAL EXAMINED. North side of Rasch cusp and a more elongate base.
Passage, near Madang, Papua New Guinea, depth
mm
38 m, 17June 1992, 1 specimen 34 preserved Reticulidia fungia Brunckhorst
length, collected by T.M. Gosliner (CASIZ and Gosliner, 1993
086401). Figures IB, 2D-F
EXTERNAL MORPHOLOGY. The external
dorsal morphology ofthis species was described in Reticulidia fungia Brunckhorst and Gosliner in
detail by Brunckhorst (1993), and a description is Brunckhorst, 1993:78-79, fig. 31D, pi. 9H.
not repeated here. A specimen from Madang, Pap- MATERIAL EXAMINED. Ima Anchorage,
ua New Guinea, is illustrated (Fig. lA) to confirm north coast ofTagula Island, Calvados Chain, Lou-
the identityofthe materialexamined. Ventrally,the isiade Archipelago, Solomon Sea, Papua New
mantlemarginis narrow (aboutone-fourththefoot Guinea, depth 10 m, 3 June 1998, 1 specimen 36
mm
width). Spots of different sizes are irregularly dis- preserved length, collected by G. Williams
tributed in one or two rows. Some ofthem are lo- (CASIZ 113687).
bate and some are circular. The oral tentacles are EXTERNAL MORPHOLOGY. The external
separated from each other and have a lateral lon- dorsal morphology ofthis species was described in
gitudinal groove. The respiratory leaves show al- detail by Brunckhorst (1993), and a description is
ternation in size (Fig. 2B). not repeated here. A specimen from Anilao, Phil-
INTERNALMORPHOLOGY.Thereproductive ippines, isillustrated (Fig. IB). Ventrally,themantle
system is triaulic (Fig. 2A). The ampulla is oval. margin is wide (about one-half the foot width).
Figure 1 Livinganimals.A,Reticulidiahalgerda,specimenfromMadang,PapuaNewGuinea,photographbyT.Gosliner.
1^, Reticulidiafungia, specimen from Anilao, Batangas, Philippines, photograph byA. Valdes. C, Reticuliasiizanneaesp.
i|ov., holotype (LACM 2897), photograph by M. Strickland.
4 Contributionsin Science, Number492 Valdes and Behrens: Phylogeny ofReticulidia
Table 1. Additional specimens ofphyllidiids examined for the phylogenetic analysis, includinglocality,depth,collection
date, collector, and museum registrationnumber.
Species Locality and depth Date Collector Registrationnumber
Phyllidia varicosa Dawapia Rocks, Simpson Harbor,
Bismarck Arch., 0-12m 24 August 1981 A.J. Ferreira LACM 1981-27.1
Pelangi and Putri Islets, Pulau-Pulau
Seribu Is.,Java, 10-30 m 16-18 May 1986 J.H. McLean LACM 1986-163.7
Phyllidiellapustulosa South ofSuva Pt., Viti Levu, Fiji,
0-1 m 16-17 May 1979 J.H. McLean LACM 1979-40.7
Low Isles, off Port Douglas, Queens-
land, Australia, 0-1 m 13 August 1981 A.J. Ferreira LACM 1981-20.1
with a few elongate spots arranged in a single row The respiratory leaves do not alternate in size (Fig.
around the mantle margin. Spots are shorter, al- 2E).
most circular, near the anterior and posterior ends INTERNALMORPHOLOGY.Thereproductive
of the foot. The oral tentacles are separated from system is triaulic (Fig. 2D). The ampulla is oval,
each other and have a lateral longitudinal groove. almost rounded. From its distal portion emergethe
Figure 2 Anatomy of Reticulidia. A, Reticulidia halgerda (CASIZ 086401), reproductive system; scale bar = 1 mm. B,
Same specimen, ventral respiratory leaves; scale bar = 1 mm. C, Same specimen, penial hook; scale bar = 2 |xm. D,
Reticulidiafungia (CASIZ 113687),reproductivesystem;scalebar = 1 mm.E,Samespecimen,ventralrespiratoryleaves;
scale bar = 1 mm. F, Same specimen, penialhooks; scale bar = 2 |xm. Abbreviations: am, ampulla; be, bursacopulatrix;
dd, deferent duct; fg, female gland; pr, prostate; sr, seminal receptacle; v, vagina
Contributions in Science, Number492 Valdes and Behrens: Phylogeny ofReticulidia 5
prostate and a long oviduct. The prostate is wide, Reticulidia byValdes and Ortea (1996) onthe basis
long, and convoluted, distally narrowing and ex- of the morphology ofthe buccal bulb, with several
panding again into the long muscular ejaculatory glandular discs, which is characteristic of this ge-
portion. The distal portion of the deferent duct nus.
opens into a very long, common atrium with the
vaginal duct. The penial hooks have a curved and Reticulidia suzanneae, new species
delicate cusp and an elongate base. They are about Figures 1C, 3
40 |JLm long (Fig. 2F). The vaginal duct opens into
Reticulidia halgerda (Brunckhorst and Burn): De-
the bursa copulatrix. The bursa copulatrix is oval. behus, 1999:277.
From the vaginal duct, near the bursa copulatrix,
Reticulidia sp. 1 Rudman, 2000: http://www.
leads a duct. This duct connects to the seminal re-
seaslugforum.net/retispl.htm.
ceptacle and to the short uterine duct, which opens
into the female glands. The bursa copulatrix is MATERIAL EXAMINED. Similan Island, An-
about three times as large as the rounded seminal daman Sea, Thailand, depth 21 m, February 2001,
mm
receptacle. 1 specimen 37 preserved length, collected by
GEOGRAPHIC RANGE. This species occurs M. Strickland on coral rubble, Holotype (LACM
sympatricallywithR. halgerda, butitisalsoknown 2897).
from Christmas Island, in the eastern Indian Ocean ETYMOLOGY. Reticulidia suzanneae is named
(Brunckhorst, 1993). in recognition of Suzanne Forman, Phuket, Thai-
land, who was the first to bring this species to our
Reticulidia gofasi Valdes and Ortea, 1996 attention and was instrumental incollectingtheho-
lotype.
ReticulidiagofasiValdes and Ortea, 1996:7-8,figs. EXTERNAL MORPHOLOGY. The living ani-
IF, 4C, 8. mals are 40-70 mmin length. The body isoval and
MATERIAL EXAMINED. Lusitanian sea- high, and the notal surface is covered with a series
mounts,Josephine Bank (36°40.02'N, 14°16.00'W: of sharp ridges that form a reticulate pattern (Fig.
Seamount I Expedition station DW61), depth200- 1C). The ridges, which are irregular and serrated,
mm
205 m, 7 October 1987, 1 specimen 11 delimit pits of various shapes from square to pen-
preserved length, Holotype (MNHN). Meteor tagonal and triangular. The anus is positioned dor-
Group seamounts, Atlantis Bank (34°06.20'N, soventrally. The perfoliate rhinophores have 18 la-
30°16.00'W: Seamount II Expedition station mellae. The background color ofthe body is bright
DW256), 340 m depth, 2 February 1993, 1 speci- yellow and the crests of the ridges are white. One
men 9 mm preserved length, Paratype (MNHN). or more large black spots are found at the bottom
EXTERNAL MORPHOLOGY. The external ofeach pit. The rhinophores are uniformlyorange.
dorsal and ventral morphology of this species was Ventrally, the mantle margin is approximately as
described in detail and figured byValdes and Ortea wide as the foot, with several oval spots arranged
(1996: fig. IF), and another description is not in- in two rows around the mantle margin. The spots
cluded here. ofthe inner row are larger and fewer than those of
INTERNAL MORPHOLOGY. Anatomical de- the outerrow. The oraltentaclesareseparatedfrom
scriptions are based on the illustrations by Valdes each other (Fig. 3D). The respiratory leaves show
and Ortea (1996:fig. 8B). The reproductive system alternation in size (Fig. 3E).
is triaulic. The ampulla is oval. From its distal por- INTERNALMORPHOLOGY.Thereproductive
tion emerge the prostate and a long oviduct. The system is triaulic (Fig. 3A). The ampulla is oval,
prostate is narrow, long, and convoluted, distally almost rounded. From its distal portion emerge the
narrowing and expanding again into the long mus- prostate and a longoviduct.Theprostateisnarrow,
cular ejaculatory portion. The distal portion ofthe long, and convoluted, distally narrowing and ex-
deferent duct opens into averyshort,commonatri- panding again into the short muscular ejaculatory
um with the vaginal duct. The vaginal duct opens portion. The distal portion of the deferent duct
into the bursa copulatrix. The bursa copulatrix is opens into a long, common atriumwith thevaginal
oval. From the vaginal duct, near the bursa copu- duct. The penial hooks have a wide base and a
latrix, leads another duct that connects to the sem- long, strong, and pointed cusp. They are about 50
inal receptacle and the short uterine duct, which jam in length (Fig. 3B). The vaginal ductopensinto
opens into the female glands. The bursa copulatrix the bursa copulatrix. The bursa copulatrix is
is approximately 10 times as large as the pyriform rounded and connects with the seminal receptacle
seminal receptacle. by a long and wide duct. Near the seminal recep-
GEOGRAPHIC RANGE. Reticulidia gofasi is tacle, this duct is joined by the uterine duct, which
only known from the Atlantic Ocean (Valdes and enters the female gland mass. The pyriformseminal
Ortea, 1996), in the Meteor Group seamounts (At- receptacle is about twice as large as the bursa co-
lantis Bank), Lusitanian seamounts (Josephine pulatrix.
Bank), and the Azores (slope ofTerceira). The buccal mass is composed of an oval to
REMARKS. This is the only species ofthe genus rounded buccal bulb and the oral tube (Fig. 3C).
that lacks dorsal ridges. It was placed in the genus The buccal bulb is covered with several radiallyar-
6 Contributionsin Science, Number 492 Valdes and Behrens: Phylogeny ofReticulidia
Figure 3 Anatomy of Reticulidia suzanneae sp. nov., holotype (LACM 2897). A, Reproductive system; scale bar = 1
mm. B, Penial hook; scale bar = 2 |xm. C, Buccalmass; scale bar = 1 mm. D,Moutharea; scalebar = 1 mm.E,Ventral
respiratory leaves; scale bar = 1 mm. Abbreviations: am, ampulla; be, bursacopulatrix;dd,deferentduct;es,esophagus;
fg, female gland; m, retractor muscle; o, oral tube; og, oral gland; ot, oral tentacle; pr, prostate; sr, seminalreceptacle;v,
vagina
rangedglandulardiscs. Theesophagusopensonthe rounded in the other species ofthe genus. The atri-
dorsal side ofthe buccal mass, where two large re- um of this species is very elongate, similar to that
tractor muscles attach. of R. fungia.
GEOGRAPHIC RANGE. This species is known
only from several localities in the Phuket Province, PHYLOGENETIC ANALYSIS
Andaman Sea, Thailand.
TAXA
REMARKS. Reticulidia suzanneae is clearly dis-
tinguishable from other members ofthe genus. The For a phylogenetic analysis, six taxa have been in-
external coloration resembles that of R. fungia by cluded. They are all four species ofReticulidia and
having orange pigment with black spots, but R. two outgroups, Phyllidia varicosa Lamarck, 1801,
suzanneae lacks the bluish background pigment and Rhyllidiella pustulosa (Cuvier, 1804).
present in the latter. Also, the black spots of R.
suzanneae are always rounded, whereas in R. fun- CHARACTERS
gia they are irregular in shape. In addition, theven-
tral side of R. suzanneae has two rows of black The eight characters of external and internal mor-
spots, whereas R. fungia has only one. Thedescrip- phology used to resolve the phylogeny of Reticuli-
tion of R. suzanneae is not based only on the ex- dia are listed below. All characters are coded as
amination of a single specimen, but also on several binary. The character states are indicated with
unpublished (by M. Strickland) and publishedpho- numbers, 0: plesiomorphic condition, 1: apo-
tos (Debelius, 1999; Rudman, 2000). The four morphic condition. The polarities discussed below
specimens photographed show a very similar and have not been obtained a priori, but rather as the
distinct color pattern, and no significant variation result of outgroup comparison in the phylogenetic
analysis. The distribution of plesiomorphic and
has been observed.
The reproductive system of R. suzanneae is dis- apomorphic character states is found in Table 2.
tinctive in having the bursa copulatrix clearly 1. Dorsal morphology. Species of Phyllidia and
smaller than the seminal receptacle. Also, the sem- Phyllidiella have the dorsum covered with tu-
inal receptacle is pear-shaped, whereas it is oval or bercles, which can be simple or compound, and
Contributions in Science,Number 492 Valdes and Behrens: Phylogeny ofReticulidia 7
Table 2. Data matrix ofcharacterstates in the taxainvolvedin thephylogeneticanalysis.Datacode: 0 = plesiomorphic
condition, 1 = apomorphiccondition.
1 2 3 4 5 6 7 8
Phyllidia varicosa 0 0 0 0 0 0 0 0
Phyllidiellapustulosa 0 0 0 0 0 0 0 0
Reticulidia halgerda 1 1 1 1 1 1 0 0
Reticulidiafungia 1 1 0 1 1 1 1 1
Reticulidiagofasi 0 0 1 1 1 1 1 0
Reticulidiasuzanneae 1 1 1 1 1 1 0 1
are supported by integumentary spicules [0]. In 4. Buccal bulb shape. In the genera Phyllidia and
most species of Reticulidia, there are no dorsal Phyllidiella the buccal bulb is oval to elongate
tubercles, but rather ridges that are not sup- [0],whereas inReticulidia itismorecircular [1].
ported by spicules [1], except for R. gofasi, 5. Oral gland shape. In species of Phyllidia and
which has simple, conical tubercles [0]. Phyllidiella the oral glands are stalkedprotuber-
2. Body texture. Most phyllidiid nudibranchs, in- ances [0], more densely arranged on the poste-
cluding Phyllidia varicosa, Phyllidiella pustulo- rior and dorsal sides of the buccal mass. How-
sa, and Reticulidiagofasihave a very dense net- ever, in the genus Reticulidia the oral glands are
work of calcareous spicules in the body [0], radially arranged glandular discs [1].
which gives the body a rigid texture. In other 6. Esophageal connection. In all species of Reticu-
members of Reticulidia, the network ofspicules lidia the esophagus connects to the buccal bulb
is not so dense and the body texture is softer through its dorsal surface 11], whereas in Phyl-
and more flexible [1]. lidia and Phyllidiella it connects to the posterior
3. Ventralrespiratoryleaves.Therespiratoryleaves end of the buccal mass [0].
ofPhyllidia varicosa, Phyllidiellapustulosa, and 7. Bursa copulatrix. The bursa copulatrix ofPhyl-
Reticulidia fungia are all similar in size or lidia varicosa, Phyllidiellapustulosa, Reticulidia
change size gradually [0], whereas in the other halgerda, and R. suzanneae has two ducts lead-
species of Reticulidia they show an alternation ing from it 10]. One of them connects to the
of larger and smaller ones [1]. seminal receptacle and the uterine duct and the
other one becomes the vaginal duct. In Reticu-
lidia fungia and R. gofasi, there is a single duct
leadingfromthe bursacopulatrixthatsplitsinto
two distally 11].
8. Genital atrium. This is the duct formed by the
fusion of the deferent duct and the vagina near
the reproductive opening. In all species exam-
ined here, the atrium is a short structure [0].
However, in two species, Reticulidia fungia and
R. suzanneae, the atrium is very elongate [1].
RESULTS
From the analysis of the data matrix a single most
parsimonious tree, 10 steps long, was obtained
(Fig. 4). This tree has a consistency index of0.800
and a retention index of 0.818. The tree is fully
resolved and shows that R. fungia and R. suzan-
neae are sister taxa, and the sister group to R. hal-
gerda. Reticulidia gofasi is the most basal member
ofReticulidia, which is a monophyletic group. The
Figure 4 Most parsimonious tree of the phylogenetic re- Bremer support analysis shows that the Reticulidia
lationships ofReticulidia, withthe Bremersupportvalues
in terms of steps on the left side of the each branch (in clade is well supported (with a value of 3). The
bold), and character evolution on the right side of each genus Reticulidia is sustained by three synapomor-
branch. Numbers on the right referto characters listedin phies: buccal bulb oval to elongate [4], disc-shaped
the text. Characters printed in bold and italic face pre- oral glands [5], and esophagus connected dorsally
sented one instance ofreversal to the buccal mass [6]. Only one character [3]
showed one instance of reversal in R. fungia.
8 Contributionsin Science, Number 492 Valdes and Behrens: Phylogeny ofReticulidia
DISCUSSION (Ghristmas Islands). Reticulidia suzanneae appears
to be endemic to the Indian Ocean coast of Thai-
TsuhpeporetvsidReentcieculfirdoima atshiasmpohnyolpohgyelneettiicc ghryopuopt,hessuiss- flarnodm o(tAhnedralmocaanlitSieeas);initthehaIsndon-ePvaecrifibce.enThreecroarndgeesd
tained by three synapomorphies and supported by
of the sister pair R. fungia-R. suzanneae do not
a high value in the Bremer analysis. This confirms
overlap, and a vicariant event could also be in-
Brunckhorst’s (1993) perceptions, which were later
volved in the speciation of these taxa. In this case,
sustained in a phylogenetic hypothesis by Valdes
their populations are separated by Sumatra andthe
and Gosliner (1999).
Malaysian Peninsula. However, given the small
Reticulidia suzanneae is the sister taxon to R. number of specimens of R. suzanneae collected to
fungia. Resemblances between these two speciesin- date, not much can be said about the geographic
clude the presence ofblack spots and the small size
range of this taxon.
and similar shape of the penial hooks. These two
characters were not included in the phylogenetic ACKNOWLEDGMENTS
analysis, but corroborate the hypothesis proposed.
However, as mentioned above, both species are We thank Mark Strickland and Suzanne Foremanforcol-
clearly distinguishable in other regards. lection oftype material. We also thank Narongpon Sitti-
thaweepat and Erwin Kohler for additional information
BIOGEOGRAPHY on the geographic range of the new species. Additional
specimens examined were collected by Terrence Gosliner,
The development of a phylogenetic hypothesis for James McLean, Gary Williams, and Antonio Ferreira.
the genus Reticulidia allows furtherinvestigationof This paper has been supported by the National Science
the biogeography of the group. Reticulidia gofasi, Foundation through the PEET grant DEB-9978155 Phy-
which is the only Atlantic member of this clade, is logeneticsystematics ofdoridnudibranchstoTerrenceM.
the sister taxon to the other species ofthe genus. A Gosliner and the senior author.
vicariant event, most likely the closure ofthe east-
west communication in the Suez area during the LITERATURE CITED
Oligocene-Miocene transaction (23 Ma), produced
Bremer, K. 1994. Branch support and tree stability. Cla-
the split ofthe original range ofthe ancestor ofthe distics 10:295-304.
Reticulidia clade and subsequent speciation. Dis- Brunckhorst, D.J. 1990. Description of a new genus and
persal of Indo-Pacific Reticulidia into the Atlantic species belonging to the family Phyllidiidae (Nudi-
or vice versa seems to be very unlikely, because of branchia: P)ondo\de2i).JournalofMolluscanStudies
the presence of large land barriers separating both 56:567-576.
basins. Valdes (2001) hypothesized that the vicari- . 1993. The systematicsandphylogenyofphyllidid
ant event derived from the separation of the Indo- nudibranchs (Doridoidea).RecordsoftheAustralian
Pacific and Atlantic basins explains the presence of Museum Supplement 16:1-107.
Debelius, H. 1999. Indian Ocean ReefGuide. Frankfurt,
a distinct clade of Atlantic and eastern Pacific spe-
Germany: IKAN-Unterwasserarchive, 321 pp.
cisietsheinstishteergetnauxsonPhtyollsidoimoepsiosthBeerrgIhnd,o-1P8a7c5i,fiwchsipceh- Kitchilniga,msI..J.1,9P9.8L.. FColraediys,tiGc.sJ.. THuhmephthreioersy,aannddpDr.acMt.icWeilo-f
cies. Acceptance of this hypothesis implies that the parsimonyanalysis. Edition2. Oxford,UnitedKing-
genus Reticulidia appeared beforetheclosureofthe dom: Oxford University Press, 228 pp.
east-west communication (during the Oligocene or Maddison, W.P., and D.R. Maddison. 2000. MacClade,
earlier). The absence of species ofReticulidia from Version4.0. Sunderland,Massachusetts: SinauerAs-
most of the Indian Ocean and the Mediterranean sociates.
could be due to subsequent extinction in these ar- Rudman, W.B. 2000. Reticulidia sp. 1. Availablevia http:
eas. The higher stability of the deep sea could ac- //www.seaslugforum.net/retispl.htm. Accessed date:
January 2001.
count for the survival of a species of Reticulidia in Swofford, D.L. 2001. PAUP'\ Phylogeneticanalysisusing
the Atlantic Ocean, despite documented environ- parsimony (''"andothermethods),Version4. Sunder-
mental changes in shallow areas. Again, Valdes land, Massachusetts: Sinauer Associates.
(2001) proposed a similar line of thinking to ex- Valdes, A. 2001. Depth-related adaptations, speciation
plain the presence of several deep-water Atlantic processes and evolution ofcolor in the genus Phyl-
species of Phyllidiopsis. lidiopsis (Mollusca, Nudibranchia). Marine Biology
Within the tropical Indo-Pacific clade, R. halger- 139:485-496
da is the sister taxon to the clade containing the Valdes, A., and T.M. Gosliner. 1999. Phylogeny of the
other two species, jR. fungia and R. suzanneae. Re- rtahdeuldae-slcersisptidoonridosf a(Mnoellwusgcean,usNuadnidbraanncehiwa)famwiiltyh.
ticulidia halgerda and R. fungia are sympatric for Zoologica Scripta 28:315-360.
the most part, and widespread throughoutthe cen- Valdes, A., andJ. Ortea. 1996. ReviewofthefamilyPhyl-
tral to western Pacific (including Fiji and Micro- lidiidae in the Atlantic Ocean (Nudibranchia, Dori-
nesia), from easternAustralia toTaiwan. Therange doidea). American MalacologicalBulletin 13:1-9.
ofR. fungia is the larger ofthe two species, includ-
ing populations reaching the eastern Indian Ocean Received 18 January 2001; accepted 5 October 2001.

SMITHSONIANINSTITUTIONLIBRARIES
3 9088 01402 9615
Natural History Museum
Los Angeles County
900 Exposition Boulevard
Los Angeles, California 90007