Molecular Phylogeny of Western Atlantic Representatives of the Genus Hexapanopeus (Decapoda: Brachyura: Panopeidae)

BRENT P. THOMA 1 , CHRISTOPH D. SCHUBART2 & DARRYL L. FELDER 1

1 University of Louisiana at Lafayette, Department of Biology and Laboratory for Crustacean Research, PO Box 42451, Lafayette, Louisiana 70504-2451, U.S.A.

2 Universittit Regensburg, Biologie 1,93040 Regensburg, Germany

ABSTRACT

Species of the brachyuran crab genus Hexapanopeus Rathbun, 1898, are common benthic inhabi­tants in coastal and nearshore waters of the Americas. Despite the frequency with which they are encountered, they are taxonomically problematic and commonly misidentified by non-experts. Lit­tle previous work has been undertaken to explain relationships among the 13 nominal species of Hexapanopeus or their relationship to other phenotypically similar genera of the family Panopei­dae. In the present study we examine partial sequences for 16S and 12S mitochondrial rDNA for 71 individuals representing 46 species of Panopeidae and related families of the Brachyura. Phylo­genies inferred from both of these datasets are largely congruent and show, with one exception, the included genera and species of the Panopeidae to represent a monophyletic grouping. Within this group, Hexapanopeus is polyphyletic, being distributed among several separate major clades and clearly warranting taxonomic subdivision.

INTRODUCTION

As part of ongoing studies of the superfamily Xanthoidea sensu Martin & Davis (2001), we have undertaken a reexamination of phylogenetic relationships among genera assigned to the family Panopeidae Ortmann, 1893, on molecular and morphological bases. Early in the course of our morphological studies, we saw reason to conclude that the genus Hexapanopeus Rathbun, 1898, as currently defined, was polyphyletic. Differences in the characters of the carapace, chelipeds, and male first pleopod (gonopod) served to obscure what, if any, relationship existed among the species in the genus. The present study serves as the first step towards restricting species composition of the genus Hexapanopeus s.s. (sensu stricto) and defining its phylogenetic relationships.

Presently, the genus Hexapanopeus consists of 13 species distributed on both coasts of the Amer­icas; six species are known from the western Atlantic ranging from Massachusetts to Uruguay, while seven more range in the eastern Pacific from Mexico to Ecuador (Table 1). Representatives of Hexa­panopeus are commonly encountered in environmental studies and inhabit a variety of nearshore environments ranging from sand-shell bottoms to rubble and surface fouling accumulations, where they often reside amongst sponges and ascidians (Rathbun 1930; Felder 1973; Williams 1984; Sankarankutty & Manning 1997). Even so, available illustrations and morphological descriptions are of limited detail and quality for many species, and little can be deduced from present literature to clarify their phylogenetic relationships.

Herein, we provide evidence for polyphyly in the genus Hexapanopeus on the basis of two mitochondrial genes (16S rDNA and 12S rDNA). We also examine relationships among species

552 Thoma el 01.

Table I. Known species presentl y assigned to I-Iexapanopells with authority and known di striblllion. Those

preceded by an asterisk (*) arc incl uded in the present phylogenetic analyses, along with one putative new

s jX:cies o f the genus from the western Gulf of Mex ico, yet to be described .

Taxon Name

* HexapallopellS allg llsl;jrolls (Benedict & Rathbun, 189 1)

Hexapallopeus beebe; Garth, 1961 * Hexapallopells car;bbaells (Stimpson, 187 I) Hexapallopeus cartagoellsis Garth, 1939 HexapmlOpeus costaricensis Garth, 1940 * Hexapanopeus lohipes CA. Milne-Edwards,

1880) * Hexapallopells lIIal1l1;II8; Sankaranku lLy &

Ferrci ra, 2000 Hexapallopells Iliearagllellsis (Rathbun, 1904) HexapallopeLls oretllI; Rathbun, 1930 * Hexapal/opells pallleflsis Rathbun, 1930 Hexapallopells qLlinqlledenraIlIs Rathbun,

1901 Hexapallopells rtlbicllndus Rathbun, 1933 HexapmlOpelis sinaloensis Rathbun, 1930

Distribution

Western Atlant ic; from MassachuselLs to Brazil

Eastern Pacific; Nicaragua Western Atlant ic; southeast Florida to Brazil Eastern Pac ific; Galapagos Islands, Ecuador Eastern Pac ific; Costa Rica Western Atlantic; Gulf of Mex ico

Western Atlantic; Rio Grande do Norte, Braz il

Eastern Pac ific; Nicaragua EaslCrn Pac ific; Mexico Western At lantic; South Carolina to Uruguay Western Atlantic; Pueno Rico

Eastern Pac ific; Gulf of California Eastern Pac ific; Mexico

currently ass igned to H exapmlOpeus and relationships o f th is genus to other genera and species en­compassed wi th in the family Panopcidae. This serves to further clarify the species compos ition of Hexapanopeus s.s., and to confirm its phylogenetic prox imity to other taxa constituting a putative panopeid lineage.

2 MATERIALS AND METHODS

2. 1 Taxon sampling

Seventy-one individuals representing 46 spec ies. 30 genera , and 10 families were subjected to molecular analyses. Of the 142 sequences used in thi s study. 132 were genera ted for this project, whi le the remaining 10 were obtained from GenB ank (Table 2). Since the identity of the sister group to the fa mily Panopeidae remains debatab le (see Martin & Davis 200 1, Karasawa & Schweitzer 2006, and Ng e t al. 2008 for di scuss ion), we incl uded 22 taxa that represent the fam ilies Xanthidae MacLcay, 1838, Pscudorhombilidae Alcock, 1900, Pilumnidae Samouelle, 1819, Chasmocarc inidae Serene, 1964, Euryplacidae Stimpson, 187 1, Goneplacidae MacLeay, 1838, Carpiliidac Onmann, 1893, Eriphiidac M acLcay, 1838, and Ponunidae Rafinesquc, 18 15.

Specimens used in thi s study were collec ted during research cruises and fie ld expeditions and ei lher directl y preserved in 80% ethyl alcohol (EtOH) or first frozen in e ither seawater or glycerol at - 80°C before later being transferred to 80% EtOH. Additional materials were obtained on loan from the National Museum of Natura l History-Smithsonian Institution (USNM). When possible, identifications of specimens were confirmed by two or more of the investigators to limit the chance of misidentificat ions.

Table 2. Crab species used for phyl ogeny reconstruction, showing catalog number. collection locality. and GenBank accession numbers for partial sequences of 16S and 12S. respectively (ULLZ = University of Lou isiana at Lafayette Zoological Collection, Lafayette, Louisiana: USN M = United States National Museum of Natural History. Smithsonian Institution, Washington D.C.).

Taxon Catalog. No. Collection Locality 16S l lS

Carpiliidae Ortmann, 1893 Carpi/ius macula/us (Linnaeus. 1758) GenBank AF50 1732 AFSO l705

Chasmocarcinidae Serene. 196-' Cilasmocarcinus ch(lcei Felder & Rabalais, t986 ULLZ S018 Northem Gulf of Mexico: 2006 EU86340 1 EU863335 CJwsmocarcinus m;ssissippiensis Rathbun, t931 ULLZ 7346 SOUlhwestern Gulf of Mexico; 2005 EU863406 EU863340

Eriphiidae MacLeay, 1838 Eriphia verrucosa (ForskAI, 1775) ULLZ ~275 Ea~ tcm Atlantic: Spai n: Cadiz, 1998 EU863398 EU863332

Euryp lacidae Stimpson. 187 1 Frevillea borbom A. Milne-Edwards. 1880 ULLZ 8369 Southeastern Gulf of Mexico: 2004 EU863399 EU863333 Sorop/ax roberts; Guinot, 1984 ULLZ 7857 Northern Gulf of Mexico: 2006 EU863400 EU863334

Goneplacidae MacLeay, 1838 Bath)p/ax ryphllis A. Milne-Edwards. 1880 ULLZ 8032 Northwestern Gulf of Mexico: 2006 EU863397 EU86333 I

Panopeidac Ortmann, 1893 Acanrholobllfu.f bermudensis (Benedict & Rathbun . 189 1) ULLZ 5843 Gulf of Mexico; Mexico: Campcche, 2002 EU863355 EU863289 Acanth%bll fus bermudensis (Benedict & Rathbun, 189 1) ULLZ6558 Westem Atlantic: Aorida , Ft. Pierce, 2005 EU863354 EU863288 Acamholobulus bermudellsis (Benedict & Rathbun, 1891) ULLZ6924 Western Atlantic: Florida . Ft. Pierce, 2006 EU863372 EU863306 AcO/u}wlobufus schmilti (Rathbun . (930) ULLZ6613 Western Atlantic: Brazil: Sao Paulo, 1999 EU863364 EU863298 Acantholobllills schmitti (Rat hbun , 1930) ULLZ 8367 Western Atlantic: Bral.i l: Sao Paulo. 1999 EU863357 EU86329 1 Cyrlop/ax nr. spill idem(lla (Bened ict, 1892) ULLZ 8423 WeStern Atlantic: Florida, Ft. Pierce, 200 I EU863369 EU863303 Dyspallopeus sayi (Smith, 1869) ULLZ 7227 Western Atlantic: Florida, Ft. Pierce, 2006 EU863395 EU863329 EllcralOpsis crassimanlls (Dana. 185 1) ULLZ6427 Western Atlantic; Florida, Ft. Pierce, 2006 EU!!63392 EU!!63326 £urypanopeus abbreviallls (Stimpson, 1860) ULLZ 3753 Western Atlantic: Aorida, Ft. Pierce, 1998 EU863388 EU863322 Ellrypallopells depresslls (Smith, 1869) ULLZ3976 Northern Gulf of Mexico; Mississippi , 1998 EU86339 I EU863325 Ellrypanopells depresslls (Smith, 1869) ULLZ6077 Eastern Gulf of Mexico; Tampa Bay, 2005 EU863390 EU863324 Eurypanopeus dissimilis (Benedict & Rathbun, 1891) ULLZ 5878 Westcrn Atlantic: Florida, Ft. Pierce. 1997 EU863396 EU863330 Eurypanopeus dissimilis (Benedict & Rathbun, 1891) ULLZ 8424 Western Atlantic: Florida. Ft, Pierce. 1997 EU863387 EU86332 I Ellryponopel4s p/onissinUis (Stimpson. 1860) ULLZ 4140 Eastem Pacifi c: Mexico: Baja California, 1999 EU863386 EU863320 G/)plOplax smithii A, Milne-Edwards, 1880 ULLZ 6793 Southwestern Gulf of Mexico: 2005 EU8633 .. 2 EU863276 G/Wtopla:c smith;; A. Milnc-Edwards. 1880 ULLZ 7686 Northern Gulf of Mexico; 2006 EU863379 EU8633 13 G/)p/Opla:c smithii A. Milne-Edwards, 1880 ULLZ 8142 Northern Gulf of Mexico: 2006 EU863350 EU863284 G/ypfopla:c smi fh ii A. Milne-Edwards, 1880 ULLZ 8335 Northern Gulf of Mexico: 2006 EU86337 I EU863305 Glypropla.t smithii A. Milne-Edwards, 1880 ULLZ 9020 Western Atlantic ; Florida, Ft. Pierce, 2003 EU863384 EU8633 18

." ~

'" -~ " ~

'"' :I: n

" ~ "0 ~ 0 0

"0 ~ c ~

V> V> W

V> V>

Tablc 2. conti nued. "-Cata log .

:::l Taxon No. Collection Locality 16S 12S ~

Hexapanopel/s Gllgllsrifrons (Benedict & Rathbun, 189 1) ULLZ69-'3 We:-.lem Atlantic; Florida. Ft. Pierce. 2006 EU863343 EU863277 S Hexapanopells ongllsrifrolls (Benedict & Rathbun. 189 1) UL LZ 7174 Western Atlantic; t-lorida. FI. Pierce. 2003 EU863368 EU863302 " -Hexapanopeus onglfstifrons (Benedict & Rathbun. 1891) ULLZ 7757 Western Atlantic: R orida. Ft. Pierce, 2006 EU86335 I EU863285 ~

He.mpallopeus al/gusti/rolls (Benedict & Rathbun. 189 1) ULLZ 8368 Ea~ lcm Gul f of M exico; A onda. 2()()..l EU863380 EU8633 1-' ~

Hexapanopeus Glzgustifrolls (Benedict & Rathbun. 189 1) ULLZ 90 19 Western Atlant ic: Florida, FI. Pierce. 2003 ' EU863385 EU8633 19 H e:capol/(Jpells .ar ib/mell! (Stimpson. 187 1) ULLZ 6859 Western Atl ant ic: Florida. Ft. Pierce. 2006 EU86338 I EU8633 t5 H exopollopeus coribbaells (Stimpson. 187 1) ULLZ 6859 Western Atl antic: Florida. Ft. Pierce. 2006 EU8633-' 8 EU863282 H exoponopells coribboells (Stimpson. 1871 ) ULLZ 7743 We~tem Atlant ic: Florida. Ft. Pierce, 2006 EU863353 EU863287 H exopallopells l obipes (A. Mi lne- Edwards, 1880) ULLZ 473 1 Nonhcrn Gulf of Mexico: Louisiana. 2001 EU863356 EU863290 H exapanopeus lobipes (A. Milne-Edwards, 1880) ULLZ 6909 Southeastern Gulf of Mexico: 2004 EU863365 EU863299 H exapanopells l obipes (A. Milne-Edward.'!, 1880) ULLZ 7828 Northern Gulf of Mexico: 2006 EU863352 EU863286 H exapanopells mallni llgi Sankarankuuy & Ferreira, 2000 USNM 260923 Western Atlantic: Brazil: Rio Grande do Norte, EU863383 EU8633 17

1996 Hexapanopeus nov. sp. ULLZ 86-16 Northern Gulf of Mexico: Texa ... , 1998 EU86336I EU863295 He.mpmlOpells pal/lensis Rathbun. 1930 ULLZ 389 1 Northern Gulf of Mex ico: Texa'i, 1998 EU863360 EU86329. HexapmlOpel/s pal/ leI/sis Rathbun. 1930 ULLZ6608 We.qern Atlantic: Brazil: Sao Paulo, 1996 EU863373 EU863307 HexapmlOpelis pmllensis Rathbun, 1930 ULLZ6862 Northern Gulf of Mex ico: Texas, 2006 EU863358 EU863292 Hexapanopell.f pal/leI/sis Rathbu n, 1930 ULLZ6870 Northern Gulf of Mex ico: Texa ... , 2006 EU86337.- EU863308 He:capanopeus pOl/lensis Rathbun, 1930 ULLZ6875 Northern Gu lf of Mex ico: Texas, 2006 EU863376 EU8633 10 He:wpanopeus paulensis Rathbu n, 1930 ULLZ6882 Nonhern Gulf of Mex ico: Texas, 2006 EU863375 EU863309 Hexapanopeus pOl/lensis Rathbun, 1930 ULLZ8645 Northem Gulf of Mex ico: Panama City. 2007 EU863377 EU8633 I I Neopanope packardii Kingsley, 1879 ULLZ 3772 United States: Florida, FI. Pierce, 1998 EU8633'-9 EU863283 PonopellS afr ican lls A, Mil ne·Edwards, 1867 ULLZ .-273 Eastern Atlantic: Spain : Cadiz, 1999 EU863370 EU8633O" POl/opells omericonlls Sau-"surc, 1857 ULLZs.-56 Western Atlantic: Florida, Ft. Pierce, 1996 EU8633-'5 EU863279 POl/opells herbstii H. Milne Edwards. 1834 ULLZ 8-'57 Western Atlantic: South Carolina. 1997 EU863362 EU863296 Ponopells loclistris Dcsbonne, 1867 ULLZ38 18 Western Atlantic: Florida. FI. Pierce. 1997 EU863363 EU863297 Panopells occidentalis Saussure. 1857 ULLZ 8640 Nonhem Gul f of Mexico: Panama City. 2007 EU863393 EU863327 Pallopeus occidelllalis SaUl,sure. t 857 ULLZ 8M3 Nonhcm Gul f of Mexico: Panama City. 2007 EU863394 EU863328 Pallop/ax dep ressa Stimp~on . 187 1 ULLZ 8056 Nonhern Gulf of Mexico: 2006 EU 863347 EU86328 I Rhi rhropal1opells harrisii (Gould, 184 1) ULLZ 3995 Northern Gulf of Mexico: Texas. 1998 EU863346 EU863280

Pilumnidae Sa mouelle. 1819 Lobopi/umnus agassizi i (Stimpson. 187 t) ULLZ 7121 Southwestern Gulf of Mexico: 2005 EU863402 EU863336 Pilwrmus jloridalllis Stimpson. 187 t ULLZ 7343 Southern Gulf of Mexico: 2005 EUK63403 EU863337

Table 2. continued.

Taxon

Portunidae Rafinesque. 1815 O~'aJjpes pllnctatlls (De Haan. 1833)

Pseudorhombilidae Alcock. 1900 Trapeziop!ax Iridentma ( A . Milne-Edwards. 1880)

Xanthidae MacLeay. 1838 Atergatis reticula/lis (De Haan. 1835) Batodaells urillator (A. Mi lne-Edwards. 1881) Eucratodes agassizii A. Milne-Edwards. 1880 Garthiope barbadensis (Rathbun . 192 1) Garthiope barbadens;s (Rat hbun . 192 1) Liomera cillctimtllla (White, 1847) Macromedaeus distinguelldlls (De Haan. 1835) Micropanope sculplipes Stimpson. 187 1 Micropallope sculplipes Stimp.~on . [87 1 Speocarcillus lobatlls Guinot. 1969 Speocarcillus mOllotliberclllatlls Felder & Rabalais. 1986 Xamhias callaliclllalllS Rathbun . 1906

Catalog. No.

GenBank

ULLZ 8054

GenBank UI..LZ 8131 UllZ 8400 Ul..lZ 8170 ULLZ 8183 GenBank GenBank ULLZ6603 UI..LZ 8025 UI..LZ 7820 ULLZ 7562 Ul..LZ4381

Collection Locality 16S

DQ062733

Northern Gulf of Mellico: 2006 EU863344

DQ062726 Southern Gulf of Mellico; 2005 EU863405 Northern Gulf of Mellico; louisiana. ]996 EU863389 Northern Gulf of Mellico: 2006 EU863367 Northern Gulf of Mell ico: 2006 EU863366

AF50 1736 DQ06273 I

Southeastern Gul f of Mellico; 2004 EU863404 Northern Gulf of Mellico: 2006 EU863378 Northern Gulf of Mexico: 2006 EU863-'07 Southwestern Gulf of Mexico: 2005 EU863359 Indian Ocean: South Africa: Sodwana Bay. 200 ] EU863382

118

DQ060652

EU863278

DQ060646 EU863339 EU863323 EU863301 EU863300 AF501708 DQ060654 EU863338 EU8633 12 EU86334 I EU863293 EU8633 16

j ~ .Q, :I: ~ x

] ~

~ c ~

u. u. u.

556 Thoma el al.

Table 3. Primers used in thi s study.

Gene Primer Sequence 5' -+3' Ref.

16S 16Sar CGC CTG 1TT ATC AAA AAC AT (I) 16S 16Sbr CCG GTC TGA ACT CAG ATC ACG T ( I ) 16S 16L2 TGC CTG 1TT ATC AAA AAC AT (2) 16S 1472 AGA TAG AAA CCA ACC TGG (3) 12S 12sf GAA ACC AGG ATT AGA TAC CC (4) 12S 12slr AGC GAC GGG CGA TAT GTA C (4)

References: ( I) Palumbi ct al. 1991. (2) Schubart ct 31. 2002. (3) Crandall & Filzpatrick 1996. (4) Buhay Cl al. 2007.

2.2 DNA extractioll, peR. and sequencing

Genomic DNA was extrac ted from muscle tissue of the pcrcopods of a (Olal of 66 specimens of the fami ly Panopeidac and related taxa of the Xanthoidea sensu Martin & Davis (200 1) utili zing one of the following extraction protocols: Genomic DNA Extrac tion Kit for Arthropod Samples (Carlagcn Molecular Systems, Cal. No. 208 10-050), Qiagen DNeasy" Blood and Tissue Kit (Qiagcn. Cal. No. 69504) , or isopropanol precipitation following Robles ct al. (2007).

Two mitochondrial markers were selec ti ve ly amplified using polymerase cha in rcacti on (PCR). A fragment of the 165 large subunit rONA approximately 550 basepairs (bp) in length was am­plified using the primers 1472 or 165br in combi nation with 16L2 and 16Sar and a fragment of the 12S small subunit rONA approximately 3 10 bp in length was amplified using the primers 12sf and 12s1r (sec Table 3 for complete primcr information). PCR reactions were performed in 25-1-'1 volumes containing: 0.5 .uM forward and reverse primcr, 200 /.LM cach dNTP, 2.5 1-'1 lOx PCR buffer, 3 mM MgCI" I M betaine, I unit NEB Standard Taq polymerase (New England Bioiabs, Cal. No. M0273S), and 30--50 ng of genomic DNA. Rcac tions were carried out using the following cycli ng parameters: initial denaturation at 94°C for 2 min; 40 cycles at 94°C for 25 sec, 40°C (l6S) or 52°C ( 12S) for I min , 72°C for I min ; fin al ex tension at 72°C for 5 min. PCR products were purified using EPOCH GenCatch PCR C lean-up Kit (EPOCH BioLabs, Cal. No. 13-60250) and sequenced in both directions using ASI BigDye@ Term inator v3.1 Cy­cle Sequencing Kit (Applied Biosystcms, Foster City, CA, USA). Cycle sequencing products were purified us ing Scphadex G-SO columns (S igma-Aldrich Chemicals, Cal. No. S6022). Sequencing products were run on an ABI PRJSM@ 3100 Genetic Analyzer (Applied Biosyslems, FOSLer City, CA, USA).

2.3 Phylogenetic allalyses

Sequences were assembled using Sequencher 4.7 (GcneCodes, Ann Arhar, MI, USA). Once assem­bled, sequences were aligned using MUSCLE (MUltiple Sequence Compari son by Log-Expectation), a computer program found to be marc accuratc and faster than other alignmcnt algorithms (Edgar 2004). Alignments were further refined using GBlocks vO.9 lb (Castrcsana 2000) to om it poorly aligned or ambiguous posi tions. Default parameters were used for GBlocks except: I) minimum length of a block = 4, 2) allowcd gap positions = half. We conducted a partition heterogene ity test or incongruence length difference test (ILD) (Bull et al. 1993), as implemcnted in PAUP* v4blO (Swofford 2003), to determ ine if the two gene regions could be combined.

The model of evolu ti on that best fit each of the datasets was determined by like lihood tests as implemented in Modeltest version 3.6 (Posada & Cranda ll 1998) under the Akaike Informat ion

Phylogeny of Hexapanopeus 557

Criterion (AlC). The maximum likelihood (ML) analyses were conducted using PhyML Online (Guindon et aL 2005) using the model parameters selected with free parameters estimated by PhyML. Confidence in the resulting topology was assessed using non-parametric bootstrap esti ­mates (Felsenstein 1985) with 500 replicates.

The Bayes ian (BAY) analyses were conducted in MrBayes (Huelsenbeck & Ronquist 2(01 ) with computations performed on the computer cluster of the CyberJnfrastructure for Phylogeneti c RESearch project (CIPRES) at the San Diego Supercomputer Center, using parameters selected by Modeltesl. A Markov Chain Monte Carlo (MCMC) algorithm with 4 chains and a tempera­ture of 0.2 ran for 4,000,000 generations, sampling I tree every 1,000 generations. Preliminary analyses and observation of the log. likelihood (L) va lues allowed us to detennine burn-ins and stationary distri butions for the data. Once the values reached a plateau, a 50% majority rule con­sensus tree was obtained from the remaining trees. Clade support was assessed with posterior probabililies (pP).

3 RESULTS

The ini tial sequence alignment of the l6S dataset. including gaps and primer regions, was 606 bp in length , while that of the 12S dataset was 384 bp in length . GBlocks was used to further refine the alignment , removing ambiguously aligned regions resulting in fin al alignments of 52 1 bp (86%) and 284 bp (74%) for 16S and 12S, respectively. Despite recent studies combining multiple loci into a single alignment (Ahyong & 0 ' Meally 2004, Porter et al. 2(05), we chose in this instance not to combine the datascts. The partition heterogeneity test or incongruence length difference test, as implemented in PAUP*, indicated that the combination of the two gene regions was significantly rejec ted (P = 0.0240). Furthermore, preliminary analys is of the combined dataset resulted in lower support for some of the tip branches than was the case in the single gene trees. This is due to different branching patterns ( 16S vs. 12S) at this level of the tree, which will be discussed later in this paper. This information would be lost in a combined tree.

Application of the likelihood lests as implemented in Modellest revealed that the selected model of DNA substitution by AIC for the 16S dataset was HKY+i+G (Hasegawa et al. 1985) with an assumed proportion of invariable sites of 0.3957 and a gamma distri bution shape parameter of 0.4975. The seleeled model for Ihe I2S dalasel was GTR+I+G (Rodriguez CI al. 1990) wilh an assumed proportion of invari able sites of 0.3228 .and a gamma distribution shape parameter of 0.6 19 1.

Phylogenetic relationships among 7 1 individuals representing 46 species of the Xanthoidea sellsu Martin & Davis (2001) were detennined us ing Bayesian and ML approaches for both the 16S and 12S datasets. For the Bayesian analyses, the fi rst 1,000 trees were discarded as burn- in and the consensus tree was estimated using the remaining 3,000 trees (= 3 million generations). Topologies resulting from the Bayesian analyses o f both the 16S and 12S datasets were largely congruent (Figs. I and 2). A number of monophyletic clades are supported by both datasets, as fo llow: I) Acamholobullls bermudellsis, Acantholobulus schmitti, and Hexapallopeus caribbaells with pP ( 16S/ 12S) of 99n7 ,2) Hexapanopeus allgLlsrijrolls and Hexapallopeus pau/ellsis with pP of 100199, 3) Eurypallopells depresslIs, Ell rypanopells dissimi/is, Dyspallopeus sayi, Neopanope packardii, and Rhithropanopeus harrisii with pP of 97/99, 4) Ew ypanopeus abbreviaw s and £ 11-rypallopeus planissimus with pP of 99/87. In general, Bayes ian IX>sterior probabilities have been shown 10 be higher than the corresponding bootstrap values. but, in many cases, posterior proba­bilities tend to overrate confidence in a topology while bootstrap values based on neighbor joining, maximum parsimony, or ML methods tend to slightly underestimate support (Huelsenbeck et al. 2001 , Huelsenbeck et al. 2002, Suzuki et al. 2002). With this in mind, it is not surprising to find that ML bootstrap supports for the same four clades are lower than the pP. The bootstrap values of the above clades are as follows: I) < 50/ < 50,2)7215 1, 3) < 50/< 50, and 4) < 50/< 50.

558

./1

Thoma et al.

1 100

88/1 Hexapanopeus paulensis - ULLZ 6870 Hexapanopeus p8ulensis · ULll 6875

97"00 Hexapanopeus paulensis - ULLZ 6882 Hexapanopeus pau/ensis - UlLZ 3891 Hexapanopeus p8u/ensis - UlLZ 6862

Hexapanopeus paulensis· ULLZ 8645 Hexapanopeus pau/ensis - UlLZ 6608

Hexapanopeus angustifrons - ULlZ 8368 '-,,,,,.,\. Hexapanopeus angustiflOns - ULLZ 7174 - Hexapanopeus angustifrons - UlLZ 9019

91188 Hexapanopeus angustifrons - ULtz 7757 Hexapanopeus angustifrons - ULll 6943

'-_-:- Hexapanopeus nov. sp. - ULLZ '8646 Cyt10iY8x nr. spinidentata - UlLZ 8423

Panopeus americanus - UlLZ 8456 Hexapanopeus lobipes - ULLZ 7828

. J""'-----"IOOI=,oo"-Hexapanopeus Iobipes - ULLZ 4731 Hexapanopeus /obipes - UlLZ 6909

~/99;~=~EUrypanopeus panissimus - ULLl 4140

Eurypanopeus abbreviatus - ULLZ 3753 631100 Neopanope packardii - ULLZ 3772

./ Dyspanopeus sayi - UlLZ 7227 '-!1lr-l Eurypanopeus dissimilis - UlLZ 8424 1" Eurypanopeus dissimilis • ULLZ 5878

r"'~.J8LJ--;:::::== Rhithropanopeus harrisii - ULLZ 3995 5 Eurypanopeus depressus - ULLZ 6077

./99

·os

Eurypanopeus depressus - UlLZ 3976 Panopeus oa:identalis - UlLZ 8640

Panopeus ocddentalis - UlLZ 8643 .22!''-- Panopeus lacustris - UlLZ 3818

Panopeus africanus - ULLZ 4273 .J86'"'---Panopeus herbst;; - UlLZ 8457

r ____ ''''OOI,,''''OO''l Garthiope barbadensis - ULLZ 8170

Garthiope barbadensis - UlLZ 8183 r--::-:-.,--.,-- Euaatopsis aassimanus - UlLZ 6427

G/yptoplax smith. - ULLZ 7686 ~L_,oo..l G/y~oplax smith; - ULLZ 9020

G/yfJopJax smith" - ULLZ 8335 Glyptoplax smithii· ULLZ 6793 . Glyptoplax smith;i - ULLZ 8142

100/100 Acantholobulus sdlmitti - ULLZ 6613 Acanth%bu/us schmitti - UlLZ 8367

Acantholobulus bermudensis - ULLZ 6558

r __ 2!IOOI"",OO"l Acantholobulus bermudensis· ULLZ 6924

Acanth%bulus bermudensis - UlLZ 5843 Hexapanopeus manning; - ULlZ 8649

'-___ 1~00I"_"'00"l Hexapanopeus caribbaeus - ULLZ 6859 Hexapanopeus caribbaeus - ULLZ 6859 Hexapanopeus caribbaeus - ULLZ 7743

Speocardnus Iobatus • ULLZ 7820

r_,iiJr~~~~~~~~speocardnus monotuberrulatus · ULLl 7562 Trapezioplax tridentala - ULLZ 8054 Euaatodes agassizii - ULLZ 8400

Miaopanope sculJXipes - ULLZ 6603 '-;;,001=, oIMicropanope srulJXipes - ULLZ 8025

Panopax depressa - ULLZ 8056 Batodaeus urinator - ULLZ 8131 ,...

./99 Xanthias canalirulatus · ULLZ 4381

Atergatis releulatus - GenBank

91/1

""00

0.05

Liomera cindimana - GenBank Maaomedaeus dislinguendus - GenBank

58/100

;6.

Eriphia velTUOOsa - UlLZ 4275 1001100 Lobopifumnus agassizjj· ULLZ 7121

Plumnus fIoridanus - UlLZ 7343 ./99

100/100

Carpiius macula/us - GenBank Ovafipes pundatus - GenBank

Balhypax typh/us· UlLZ 8032 C. mississippiensis - ULLZ 7346

C. chacei - UlLZ 8018 .'58L __ 9§j'iO<lC==~F,.~,~~e~a~b~a~rbala - ULLZ 8369

Soloplax roberts; - ULLZ 7857

!<'igurc 1. Phylogeneti c relati onships among panopeid crab species and selected representatives of the super­family Xanthoidca sel/su Martin & Davis (200 I). inferred by Bayes ian analysis from 521 basepairs of the 16S rDNA gene. Confidence intervals are from 500 bootslrap maximum li keli hood analysis fo ll owed by Bayesian posterior probabilities. Genus shown as "c." = Chasmocarcil1l1s. Values below 50 are indicated by "-".

Phylogeny of Hcxapanopeus 559

./.

'''5

'"

Hexapanopeus paulensis - UlLZ 6870 Hexapanopeus paulensis - UlLZ 6875 Hexapanopeus paulensis - UlLZ 6882 Hexapanopeus paulensis - ULLZ 6862

Hexapanopeus paulensis - UlLZ 3891 Hexapanopeus paulensis - ULLZ 8645

Hexapanopeus paulensis - ULLZ 6608

L---"",,,'OO"1 ,Hexapanopeus angustifrons - ULLZ 8368

Hexapanopeus angustifrons - ULLZ 7174 Hexapanopeus angustifrons - ULLZ 9019 Hexapanopeus angustifrons - ULLZ 7757 Hexapanopeus angustifrons -UL12 6943

Hexapanopeus nov. sp. - ULLZ8646 ~ G/Y!ioplax smithii - ULLZ 7686

G/Y!ioplax smithii · ULLZ 9020 .... m1~ Gly!iopiax smithii · ULLZ 8335

Glvptoplax smithii · ULLZ 6793 Giy!ioplax smithii - UL12 8142

I ~C==="E£Eurypanopeus abbrevia/us· ULll 3753 :ji 7 Eurypanopeus panissimus - UL12 4140

-195 Hexapanopeus Iobipes· UL12 4731 , __ -,'001",,'00, Hexapanopeus lobipes . ULLZ 6909

Hexapanopeus lobipes · ULLZ 7828 Panopeus herbstii · ULLZ 8457

Panopeus africanus - UlLZ 4273 Panopeus lacvstris· ULLZ 3818

L-I-- Panopeus ocddentalis - UlLZ 8640 Panopeus ocddentalis • ULLZ 8643

Eurypanopeus depressus - UlLZ 6077 Eurypanopeus depressus - UlLZ 3976 Eurypanopeus dissimilis - UlLZ 8424

100'100 Eurypanopeus dissimilis - UlLZ 5878 Oyspanopeus sayi· UlLZ 7227

Neopanope packardii . UlLZ 3772 -,~~;C=-:':Rhifhropanopeus harrisi; - ULLZ 3995 Panopeus americanus - ULLZ 8456

Hexapanopeus caribbaeus · ULLZ 6859 Hexapanopeus caribbaeus - UlLZ 6859 Hexapanopeus manningi. ULLZ 8649 Hexapanopeus caribbaeus - ULl2 7743

'001' Acantholobu/us schmitti· ULLZ 6613 Acanth%bu/us schmitti - ULLZ 8367 Acanth%bu/us bermudensis . ULLZ 5843 Acanth%bu/us bermudensis - ULLZ 6924

Acantholobulus bermudensis . ULLZ 6558 Cyrtoplax nr spinidentata . ULLZ 8423

Eucratopsis crasstmanus . ULLZ 6427 Speocarrinus monotubercu/atus · UlLZ 7562

~,,~_--::-_--,-_:-:- Trapezioplax tridentata - UlLZ 8054 + Speocardnus Iobatus - Ul LZ 7820 l ___ ...:... ___________ ....l!"!!!2" t:====-C~h.asmocarcinus mississippiensis· UlLZ 7346

Chasmocarcinus chace; - ULLZ 8018 -"'C===~;;;;;o;~;;; Panoplax depressa • ULLZ 8056 I Eucratodes agassizii· UlLZ 8400 L __ Tciiw;LMicropanope sculpt/pes - ULLZ 6603

100"1 Micropanope sculptipes· ULLZ 8025 ,----Batodaeus urinator - ULLZ 8131

~'[=,~=~~;:~~~L~~· me~~,.~o~n~d~;mana - GenBank Atergatis reticulatus - GeoBank

,.

0.05

Xanth ias canaliculatus - UlLZ 4381 L ____ ,~OOI~,~==Pi/umnus f/oridanus· UlLZ 7343

Lobopilumnus agassizii· ULLZ 7121 L------Macromedaeus distinguendus · GeoBank

1(01 Garthiope barbaclensis - ULLZ 8170 Garthiope barbadensis · ULLZ 8183

Eriphia verrucosa - UlLZ 4275 Carpi/ius mawla/us - GeoBank

Bathypax typllius - ULLZ 8032 Ovalipes punda/us· GenBank

Sotopax robertsi - ULLZ 7857 Frevillea barbata - ULLZ 8369

Figure 2. Phylogenetic relationships among panopeid crab species and selected representalivcs of the super­fam il y Xanthoidea sensu Martin & Davis (2001), inferred by Bayesian analysis from 284 bascpairs of the l2S rDNA gene. Confidence intervals are from 500 bootslrap maxi mum likelihood analysis followed by Bayesian posterior probabililies. Values below 50 are indicated by ;'-".

560 Thoma et al.

4 DISCUSSION

Here we report two molecul ar phylogenies o f the genus Hexapallopeus and related genera of the family Panopcidae. These phylogenies, which are based on parti al sequences of the 165 and 12S rO NA, contain fi ve of the 13 nominal species in Hexapanopeus and a single undescri bed species that appears to be assignable to the genus. In add ition, we have included representatives of 18 species of the family Panopeidae in order to better address both the monophyly of HexapGlwpells and the relat ionships of species currently ass igned to Hexapallopells to other panopeid taxa. Although onl y five species of Hexapollopells arc included in the dataset, these five species represent five of the six nominal species known from the western At lantic. It is clear from our analyses that the genus Hexa­pGllOpellS is markedly polyphyletic and that further study of a ll its putative members is warranted, by both morphological and molecular methods.

4.1 Hexapanopeus angust ifrons and Hexapanopcus paulensis

The phylogenies presented here lend support to a narrowed defini tion of Hexapallopells that in­cludes only the type-spec ies of the genus Hexapallopells allgllst'ijrolls (Benedict & Rath bun, 1891) and Hexapollopells palllensis Rathbun. 1930, pending results o f morphological and molecular anal­yses for the remaining eight present congeners. It is interesting to note that in all ana lyses thcse taxa form a monophyleti c clade and that within both species there is further ev idence for genetic structure. II is unclear if the genctic divergence seen in these clades is the result of cryptic speciation or population diffcrentiation, but the current analyses suggest some combination of the two mighl occur in each complex.

4.2 Hexapanopeus nov. sp.

In the ana lyses of the 165 dataset, the sistcr group to the H. mlgllstijrollslH. paule' lsis clade is an undescribed species from intertidal waters of south Texas in the western Gulf of Mex ico. This undescri bed species resembles H. paulellsis in general morphology, but it has a very dist incti ve gonopod, which most resembles that of AeontllO/obu/lIs schmilli (Rathbun, 1930). In contrast 10 the results of the 165 dataset, the 125 dataset lends support to a clade that is composed of the unde­scri bed species and Glyptoplax smithii A. Milne-Edwards. 1880, as the sister group 10 the H. anglls­ti/ronslH. paulensis clade. Un fortunately, suitable materia l of GJypropJax pugnax Smith, 1870, lhe type species of the genus. has not to date been ava ilable for molecular analysis; therefore. it rcmains unclear whether this undescribed species is Illost appropr iately treated as a member of the genus Hexapallopeus, the genus GlyplOpJa:r, or a new monospecific genus.

4.3 Hexapanopeus lobipcs

The species Hexapallope//s lobipes (A. Milne-Edwards, 1880) has had a very unsettled taxonomic history. After being described as a species of Neopallope A. Milne-Edwards, 1880, it was later transferred to the genus Lop/Jopallopells Rathbun, 1898, by Rathbun in 1898. In his 1948 revision of the gcnus LophopalJopeus. Menzies pointcd out that H. /obipes does not fit the diagnosis of the genus Lophopallopells. Upon transferring the species 10 the genus Hexapallopeus, he noted Ihat " it seems to fit Ihe d iagnosis of that genus beller than tha t of any other American genus." On ly isolated records o f Hexapanopeus lobipes have been reported since Menzies' 1948 work (Wickstcn 2005, Fclder et al. in press), and thcre has been no reassessment o f its placement with in the genus Hexapallopells. The gOllopod of H. lobipes is di stincti ve and has little resemblance 10 those in othcr members of the genus Hexopanopeus. Furthermore, unlike the carapaces of H. allgllstijrons and H. pal/leI/sis, which have five distinct anterolateral teeth, the 1st and 2nd antero-iateral teeth of

PhylogellY of Hexapanopeus 56 1

H. lobipes are generally fused, giving the appearance of four anterolateral teeth . On the basis of these and other morphological fea tures, it is unclear whether H. Jobipes is justifi ably assignab le to the genus Hexapanopeus. Whalever the case to be made on the basis of morphology alone, we cannot concur with Ng el al. (2008) in reass igning thi s species to Lophopanopells .

OUf analyses support removal of H. lohipes from the genus Hexapanopeus and appear to jus­tify establishment o f a new mOllospccific genus for H. lobipes. In both topologies, H. Jobipes fall s outside the clade formed by H. angustifrons and H. pallle'lsis. In the phylogeny inferred from the 165 dataset, H. lobipes is the s ister group 10 Panopells americanus Saussure, 1857, with ML boot· strap and pP values of <50/90, respectively. The phylogeny inferred from the 12S datase t presents H. lobipes as a sister group to Pal10pells s.s. H. Milne Edwards, 1834, with ML bootstrap and pP va lues of < 5015 1, respectively. Despite low support va lues, both topologies lend support to the re· moval of H. lobipes from the genus Hexapanopeus and the erection of a new genus for the species, as is currently in progress.

4.4 Hexapanopeus manningi

HexapmlOpellS malllling; Sankarankutty and Ferreira, 2000, was descri bed on the basis of materi al from Rio Grande do Norte, Brazil. This species was distinguished from Hexapanopells caribbaells (Stimpson, 187 1) by characters of the frontal margin, the 3rd anterolatcral tooth of the carapace, and the apical process of thc gonopocl; however, upon the basis of synoptic comparisons of the male paratypc (USNM 260923) to malerial of H. caribbaells from eastern Florida, it appears that there is considerable morphological overl ap between these two taxa, raising the question as to whether H. l1uUln;ngi might be a junior synonym of H. caribbaeus. The topology inferred from the l6S dataset places H. mamlillgi in very close proximity to H. caribbaeus; distance between these taxa is very short and comparable to that within other accepted single·species clades in our tree. The clade containing both H. manningi and H. caribbaells has high support values, with ML bootstrap and pP values o f 100/ 100, respectively. The strongest support for a synonymy of the two taxa comes from the topology inferred from the 12S datase t, with H. mmmingi positioned with in the clade of H. caribbaeus. Our molecular phylogenies support synonymy of H. mallllillgi wi th H. caribbaeus, and we herewith recommend that taxonomic revision, regardless of the eventual generic assignment to be accorded (see below).

4.5 Hexapanopeus caribbaeus

Hexapanopeus caribbaeus was originally descri bed as a representative of the genus Micropanope; however, upon erection of the genus Hexapallopeus, Rathbun ( 1898) transferred this species to the genus Hexapanopeus apparently on the basis of carapace shape. It wasn' t unt il the 1997 work by Sankarankuuy and Manning that di stinct differences between the gonopod of H. caribbaells and that of the type·species H. angllstijrolls were noted. In the present analys is, this species is clearly separated from Hexapallapeus 5.5., and shown to be more closely a llied to the genus Acam/w lobulus.

4.6 Genlls Acantholobulus

Felder and Martin (2003) erected the genus AcarllllOlobllllls to accommodate a number of species from the genera Panopells and Hexapanopeus, which included: I) the type·spccies Acalltholobl/ ­IllS bermuderzs;s (Benedict & Rathbun, 1898), formerly Panopel/s bermlldensis; 2) Acanth%bu/us mirajlorensis (Abele & Kim, 1989), fannerly Pallopeus mirajlorellSis; 3) Acantholobulus pacifi­C/lS (Edmondson, 1931), formerly Panopells pacijiclls; and 4) Acantho/abu/lls schmitt; (Rathbun, 1930), fonnerl y Hexapanopeus schmilli. Despite similarities between H. caribbaeus and A. schmitti in both carapace and gonopod morphology, the possible re lat ionship between H. caribbaeus and newly assigned members of the genus Acantholobuills was not addressed. The phylogenies inferred

562 Thoma e( at.

from both our datasets strongly support inclusion of H. caribbaells within the genus Acantha/ob­ulus. While the phylogeny inferred from the 16S dataset shows H. caribbaells nested with Acarl ­(h%bu/lls , the topology in ferred by analys is of the 12S datasets supports a sister group relat ionshi p between H. caribbaells and both A. bermudellsis and A. schmif(i. Although both of these relat ion­ships are supported by pP > 75, the 165 dataset shows considerably higher pP (99177 for 1651125, respcclively). As add itional spec ies of Acantho/abulus become avai lable ,for inclusion in our analy­sis, the re lationship between Acantho/abullls and its closest re latives should be more definiti ve ly re­solved. Even so, it is by present find ings establi shed thai H. caribbaells is well separated from Hexa­pallopeus S.S., and we app ly the new combination Acantholobu/lls caribbae/ls (Stimpson, 187 1).

4.7 Panopeus ameri can us

In a study of mud crabs from the northwestern Atlantic, Schubart et al. (2000) clearly showed poly­phyly in the genus Panopells, with both Acan(/IO/ablilus bermlldellsis (as Pallapells bermudellsis , see di scussion above) and POl/opells american liS fa lling we ll oUl side Pal/opells s.s. (Schubart et al. 2000, Fig. I). In the presem study, we find additional support for these findings with the topologies inferred from both datasets positioning P. american lls outside Panopeus s.s.; however, the topolo­gies differ in where P. ameriCQllllS is placed re lat ive to species of other genera. In the topo logy inferred from the 16S dataset, P. americallus is a sister group to H. lobipes, while in the topo logy inferred from the 12S dataset, P. americallllS is Ihe sister group to the clade containing E. depresslIs , E. dissimilis, N. packardii, D. sayi, and R. harrisii. However, thi s arrangement is poorly supported wi th ML bootstrap and pP va lues less than 50. Desp ite the differences in the topologies inferred from these two datasets, both provide evidence for the removal of P. arnericO/III s from Pallopeus. Pending a thorough ana lysis of ad ult and larval morphology, data presented here support the estab­lishment of a new genus for P. americantls.

4.8 Genus Eurypanopeus

Schubart et a1. (2000, Fig. \ ) also provided evidence for polyphyly among spec ies presently as­signed to the genus Eurypanopeus A. Milne-Edwards, 1880, with species of ElirypanopeLls fa lling into three separate clades. In the present stud y, topologies inferred from both datasets support the polyphyle tic nature of Eurypallopells, wi th representatives found in three c lades for 165 (Fig. I) and two clades for 12S (Fig. 2). It is unclear what effect the addition of sequence data from other species of EUl)lPat/Opeus would have on the ana lyses; however, on the basis of evidence presented here and by Schubart et al. (2000), comprehensive study and taxonomic rev ision of the genus are needed .

4.9 Panoplax depressa

Despite a gOllopod that shares little in common with that of the typical panopeid, Panop/ax de­pressa Stimpson, 187 1, has long been considered a member of the subfamily Eucratopsinae within the famil y Panopeidae (Martin & Abele 1986, McLaughlin et al. 2005, Ng et al. 2008). The analyses presented here provide no support for the inclusion of Panoplax within the family Panopeidae. In topologies inferred from both datasets, Panoplax depressa is well separaled from remaining rep­resentatives of the family Panopeidae. III the phylogeny inferred from the 165 dalasel, Panoplax depressa is found nested within a poorly supported clade containing representati ves of the fami lies Xanthidae and Pseudorhombilidae (MLlpP <50/99). In the phylogeny inferred from the 125 dataset, Panoplax depressa is al so excluded from the remaining representat ives of the family Panopeidae, nested within a poorly supported c lade conlaining representatives of the family Xanthidae (MUpP <50/90). Despite the low support values for the clades currently containing Pafloplax depressa, there is little evidence to support the inclusion of Panoplax wi thin the fami ly Panopeidae.

Phylogen), of Hexapanopcus 563

4.10 Garthiope barbadensis

The genus Garrhiope Guinot, 1990, was described to accommodate three small species formerl y at­tributed to the genus Micropanope. Upon its erection, similarities between Garthiope and the family Trapeziidae were noted; however, in their recent review Ng et al. (2008) considered the genus to be a part of the family Xanthidae. In the present analyses the complex relationship of Garth iope to the remaining taxa of the Xanthoidea sensu Martin & Davis (2001 ) is shown in the conflict between the 16S dataset and 12S dataset in regards to the placement of Garthiope. In the phylogeny inferred from the 16S dataset, Garthiope barbade'lsis (Rathbun, 192 1) is found within the famil y Panopei­dae, where it is located within a clade containing representatives of the subfamily Eucratopsinae. However, this clade has support va lues with ML and pP values of <50/98. To further confound our understanding, in the analyses of the 12S dataset, Garthiope barbadellsis falls well outside the family Panopeidae in a clade containing representatives of the Eriphioidea, Carpilioidea, Gonepla­coidea, and Portunoidea. As this arrangement also has poor support values «50), the relationship

. of Garthiope to these groups remains unclear. The type-species of the genus Garthiope spillipes (A Milne-Edwards, 1880) was not ineluded in these analyses; as a result , it is unclear what effect its inclusion may have on the analyses. Further study of the group is needed to clarify how this genus is related [0 other representatives of the Xanthoidea sensu Martin & Davis (2001 ).

4. 11 Olltgroup taxa

Composition of the superfamily Xanthoidea sensu Martin & Davis (2001) is a subject of ongoing debale (Guinol 1978; Jamieson 1993; Coelho & Coelho Filho 1993; Schuba" el al. 2000; Wel­zer et aL 2003; Karasawa & Schweitzer 2006; Ng et a!. 2008). In all of our analyses, the family Xanthidae is clearly shown to be polyphyleti c, Analysis of the 16S dataset reveals a single clade containing representatives of Panopeidae, Pseudorhombilidae, and three subfamilies of Xanrhidae; however, thi s clade is poorly supported with ML bootstrap values and pP of <50/99 (Fig. I). Fur­thermore, a second clade contains a single representative of the family Xanthidae as well as reprc4 sentativcs of Eriphioidea, Pilumnoidea, Carpilioidea, Goneplacoidea, and Portunoidea. This clade is well supported with ML bootstrap values and pP of 97/100. Within this clade we also find rep­resentatives of three families of Goneplacoidea, with two species of Chasmocarcifllls representing Chasmocarcinidae, Frevillea barbara and SOlOplax roberts; representing Euryplac idae, and Bathy­plnx typhlus representing Goneplacidae. While Chasmocarcinidae and Euryplac idae form a poorly supported monophyleti c clade, Gonepl acidae is found in another clade with representatives of Por­tunoidea and Carpilioidea. Although neither of these clades is well supported (MUpP <50/58 & <50/98), they provide evidence for a polyphyletic Goneplacoidea. While the topology inferred from the 12S dataset (Fig. 2) still presents evidence for a polyphyletic Xanthidae and Goneplacoidea, the evidence differs from that inferred by the 16S dataset (Fig. I). However, support va lues for the oul­group topology inferred by the 12S dataset are very low, making any conclusions drawn from this topology questionable: Regardless of differences between these two topologies, it is apparent that both Goncplacoidea and Xanthidae are polyphyletic and in need of revision.

ACKNOWLEDGEMENTS

We thank H. Bracken, M. Bruglcr, J. Felder, S. France, E. Palac ios-Theil , E. Pante, V. Paul , R. Robles, J. Thoma, and A. Windsor for assisting in obtaining specimens or with various aspects of data coJlection, analysis, and manuscript preparat ion. We 'are grateful to J. Martin and G. Davis for providing loans of materials from the Natural History Museum of Los Angeles County, R. Lemaitre for access to specimens at the National Museum of Natural History-Smithsonian Institution, and F. Mantelatto for loans of specimens from Braz il. This study was supported in part by U.S. National

564 Thoma et al.

Science Foundation grants NSF!BS&I DEB-03 15995 and NSF! AToL EF-053 1603 to D. Fe lder, as well as severa l small travel grants from the Smithsonian Marine Stat ion, Ft. Pierce, Florida. Addi ­lional support to B. Thoma was provided under a Louisiana Board of Regents doctoral fellowship. This is Uni versi ty of Louisiana Labora tory for Crustacean Research contribution no. 128 and Smith­sonian Marine Station contribution no. 737.

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