Decapoda, Brachyura, Xanthidae)
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Zoologica Scripta Phylogenetic relationships of the ubiquitous coral reef crab subfamily Chlorodiellinae (Decapoda, Brachyura, Xanthidae) ROBERT M. LASLEY JR,SEBASTIAN KLAUS &PETER K. L. NG Submitted: 5 July 2014 Lasley, R.M. Jr, Klaus, S., Ng, P.K.L. (2015). Phylogenetic relationships of the ubiquitous Accepted: 26 October 2014 coral reef crab subfamily Chlorodiellinae (Decapoda, Brachyura, Xanthidae). —Zoologica doi:10.1111/zsc.12094 Scripta, 44, 165–178. The xanthid subfamily Chlorodiellinae is one of the most ubiquitous coral reef crab taxa in the Indo-West Pacific region. Many species are common in coral rubble and rocky shores from Hawaii to eastern Africa, often dominating reef cryptofauna in terms of biomass. Phylo- genetic analyses of mitochondrial (COX1, 12S rRNA and 16S rRNA) and nuclear (histone H3) gene sequences of 202 specimens indicate that the Chlorodiellinae is polyphyletic as presently defined. Three genera, Pilodius, Cyclodius and Chlorodiella, and two previously unde- scribed lineages were recovered as a well-supported clade. In combination with morphological data, the subfamily is redefined and restricted to this clade. Two new genera, Soliella gen. n., and Luniella gen. n., are described based on features of the carapace, male thoracic sternum and male gonopods. The remaining chlorodielline genera and members of the Etisinae, a sub- family with supposedly close morphological affinities to the Chlorodiellinae, were recovered at various positions throughout the xanthid phylogeny, although with relatively low support values. These results reiterate the unresolved status of xanthid subfamilial relationships, but nevertheless provide progress for xanthid systematics. Corresponding author: Robert M. Lasley Jr, Department of Biological Sciences, National Univer- sity of Singapore, Kent Ridge, Singapore 119260, Singapore and Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Suitland, MD 20746, USA. E-mail: [email protected] Sebastian Klaus, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, 610041, China and Department of Ecology and Evolution, J. W. Goethe-Universit€at, Frankfurt am Main, D-60438, Germany. E-mail: [email protected] Peter K. L. Ng, Raffles Museum of Biodiversity Research, National University of Singapore, Kent Ridge, Singapore, 119260, Singapore. E-mail: [email protected] Introduction taceans found in gut contents were chlorodielline crabs The 50 described species, in eight genera, of chlorodielline (extrapolated from Leray et al. 2012). crabs (Xanthidae) are widely distributed throughout the Delimiting Chlorodiellinae Ng & Holthuis 2007 is diffi- tropical and subtropical Indian and Pacific oceans, with one cult due to tenuous interfamilial relationships. The taxon- western Atlantic representative (Ng et al. 2008; Mendoza omy of most of the 16 subfamilies of Xanthidae is in serious & Manuel-Santos 2012; Lasley et al. 2013). Members of need of revision based on morphology and molecular phy- the subfamily are abundant on rocky seashores, within live logenetics, including the Chlorodiellinae (Ng et al. 2008; coral, and, most notably, in coral rubble. They often domi- Lai et al. 2011; Mendoza & Guinot 2011; Mendoza & nate coral reef cryptofauna in terms of biomass (pers. obs.; Manuel-Santos 2012; Mendoza et al. 2012). This subfamily Peyrot-Clausade 1977, 1979) and are especially common in is characterized by spoon-tipped chelae; a non-projecting microhabitats that have been recently targeted in large- front; a broad, transversely ovate carapace; and a dactylo- scale biodiversity surveys, for example dead Pocillopora propodal locking mechanism on the walking legs (sensu heads, and ARMS (autonomous reef monitoring structures) Serene 1984). Many of these characters, however, are pres- (Plaisance et al. 2011). Furthermore, chlorodielline crabs ent in genera of other subfamilies (e.g. Cymo, Cymoinae; likely play a major ecological role in reef food webs, as a Leptodius, Xanthinae; Etisus, Etisinae; Kraussia, Kraussiinae; recent study carried out on five species of reef-associated and Garthiella, Garthiellinae) (Ng et al. 2008; Mendoza & fishes in French Polynesia indicated that 37% of the crus- Manuel-Santos 2012). Furthermore, the closest relatives of ª 2014 Royal Swedish Academy of Sciences, 44, 2, March 2015, pp 165–178 165 Phylogenetic relationships of Chlorodiellinae Lasley et al. Chlorodiellinae, namely Etisinae, are polyphyletic and additional etisine species were added, as the taxon is mor- defined by morphological characters of doubtful homology, phologically similar and, in previous molecular phyloge- making generic assignment based on common ancestry diffi- netic studies, tends to group with the Chlorodiellinae, cult (Ng et al. 2008; Felder & Thoma 2010; Lai et al. 2011). albeit with low support (Ng & Yang 1998; Clark & Ng Dana (1851) described the subfamily ‘Chlorodinae’ in 1999; Ng et al. 2008; Lai et al. 2011; Lasley et al. 2013). four sentences and included genera from several xanthid Menippe rumphii (Menippidae), Benthochascon hemingi (Por- subfamilies, as well as Daira (Dairidae). Subsequent authors tunidae), Trapezia cymodoce and Quadrella coronata (Trapez- split and reorganized the subfamily with varying results. iidae) were selected as outgroups following Lai et al. Most notably, Serene (1984) gave a concise historical review (2011). The following abbreviated subfamilial and familial of ‘Chlorodiinae’ and limited the taxon to five genera: Chlo- names are used for clades recovered in our analyses that rodiella Rathbun, 1897; Cyclodius Dana, 1851; Pilodius Dana, are congruent with clades recovered in Lai et al. (2011): 1851; Liocarpilodes Klunzinger, 1913; and Tweedieia Ward, Eux (= Euxanthinae), Lio (= Liomerinae), Xan (= Xanthi- 1934. Three monotypic genera were subsequently assigned nae), Act (= Actaeinae), Zos (= Zosiminae), Pol (= Poly- to this group: Sulcodius Clark & Ng, 1999; Vellodius Ng & dectinae), Cym (= Cymoinae), Pse (= Pseudorhombilidae), Yang, 1998; and Garthiella Titgen, 1986. The latter genus Pan (= Panopeidae) and Chl (= Chlorodiellinae). was eventually elevated to a monotypic subfamily (Mendoza & Manuel-Santos 2012). The monotypic genera Sulcodius Phylogenetic analysis and Vellodius were compared to Cyclodius, Pilodius and Chlo- Single-gene trees were constructed to examine congruence rodiella in their original descriptions (Ng & Yang 1998; between loci (not shown), in addition to trees based on the Clark & Ng 1999). However, only cursory attention was concatenated data set (Fig. 1). A total of 753 mitochondrial given to Liocarpilodes and Tweedieia historically; both only (12S rRNA gene = 199, 16S rRNA gene = 200, mentioned briefly and without supporting figures. The focus COX1 = 170) and nuclear (H3 = 184) sequences were used on Cyclodius, Pilodius and Chlorodiella may suggest a notion for the analyses, of which 151 were generated for this study of the authors that these three genera are monophyletic to (Table 1); the remaining sequences, most of which are non- the exclusion of Liocarpilodes and Tweedieia. This has recently chlorodielline taxa, were previously published and obtained been supported in part by recent molecular phylogenetic from GenBank (Lai et al. 2011; Lasley et al. 2013). New studies (Lai et al. 2011; Lasley et al. 2013). sequences were amplified following Thoma et al. (2009) Provided here is the first comprehensive molecular phy- (12S and 16S rRNA genes), Buhay et al. (2007) (12S rRNA logeny of the Chlorodiellinae. Chlorodielline taxa are anal- gene), Lai et al. (2009) (16S rRNA gene) Colgan et al. ysed within a framework of previously published xanthid (1998) (H3), Thoma et al. (2013) (COX1) and Geller et al. sequences to emphasize the polyphyletic state of the sub- (2013) (COX1). As these publications comprise several pri- family. The Chlorodiellinae is restricted to a well-sup- mer and PCR profile combinations, we provide our opti- ported, monophyletic clade and redefined based on a suite mized combinations using Promega PCR Master Mix. The of morphological characters, and two new genera are most successful primers used were as follows: 12sf and 12slr described. Any chlorodielline genera outside of this clade (12S) (Buhay et al. 2007); crust16sf1 and crust16sr2 (16S) are regarded as incertae sedis for the time being. (Lai et al. 2009); jgHCO2198 and jgLCO1490 (COX1) (Geller et al. 2013); and H3af and H3ar (H3) (Colgan et al. Materials and methods 1998). Reactions were carried out using the following Taxon sampling cycling parameters: initial denaturation at 95°C for 5 min; Two hundred and two specimens representing 189 nominal four cycles at 94°C for 30 s, 57°C (12S), 52°C (16S), 50°C species, 89 genera and 14 xanthid subfamilies were selected (COX1), 50°C (H3) for 45 s, 72°C for 1 min; then 34 cycles for the molecular analyses. All eight chlorodielline genera at 94°C for 30 s, 52°C (12S), 47°C (16S), 45°C (COX1), were represented, and 37 of 48 chlorodielline species were 47°C (H3) for 45 s; and a final extension at 72°C for 8 min. included. The sequences generated for this study are All new sequences were submitted to GenBank (Table 1). recorded in Table S1. Specimens for morphological and COX1 and H3 sequences were checked for stop codons. molecular analyses are deposited at the following institu- Alignments were generated with MUSCLE (multiple tions: the Florida Museum of Natural History, Gainesville, sequence comparison by log expectation) (Edgar 2004) Florida, USA (UF); the