Mitogenomic analysis of decapod crustacean phylogeny corroborates traditional views on their relationships

Phylogenetic relationships within decapod crustaceans are highly controversial. Even recent analyses based on molecular datasets have shown largely contradictory results. Previous studies using mitochondrial genomes are promising but suffer from a poor and unbalanced taxon sampling. To fill these gaps we sequenced the (nearly) complete mitochondrial genomes of 13 decapod species: Stenopus hispidus, Polycheles typhlops, Panulirus versicolor, Scyllarides latus, Enoplometopus occidentalis, Homarus gammarus, Procambarus fallax f. virginalis, Upogebia major, Neaxius acanthus, Calocaris macandreae, Corallianassa coutierei, Cryptolithodes sitchensis, Neopetrolisthes maculatus, and add that of Dromia personata. Our new data allow for comprehensive analyses of decapod phylogeny using the mitochondrial genomes of 50 species covering all major taxa of the Decapoda. Five species of Stomatopoda and one species of Euphausiacea serve as outgroups. Most of our analyses using Maximum Likelihood (ML) and Bayesian inference (BI) of nucleotide and amino acid datasets revealed congruent topologies for higher level decapod relationships: (((((((Anomala, Brachyura), Thalassinida: Gebiidea), Thalassinida: Axiidea), (Astacidea, Polychelida), Achelata), Stenopodidea), Caridea), Dendrobranchiata). This result corroborates several traditional morphological views and adds new perspectives. In particular, the position of Polychelida is surprising. Nevertheless, some problems can be identified. In a minority of analyses the basal branching of Reptantia is not fully resolved, Thalassinida are monophyletic; Polychelida are the sister group to Achelata, and Stenopodidea are resolved as sister group to Caridea. Despite this and although some nodal supports are low in our phylogenetic trees, we think that the largely stable topology of the trees regardless of different types of analyses suggests that mitochondrial genomes show good potential to resolve the relationship within Decapoda.     

Phylogeny of Decapoda using two nuclear protein-coding genes: origin and evolution of the Reptantia

The phylogeny of Decapoda is contentious and many hypotheses have been proposed based on morphological cladistic analyses. Recent molecular studies, however, yielded contrasting results despite their use of similar data (nuclear and mitochondrial rDNA). Here we present the first application of two nuclear protein-coding genes, phosphoenolpyruvate carboxykinase and sodium-potassium ATPase alpha-subunit, to reconstruct the phylogeny of major infraorders within Decapoda. A total of 64 species representing all infraorders of Pleocyemata were analyzed with five species from Dendrobranchiata as outgroups. Maximum likelihood and Bayesian inference reveal that the Reptantia and all but one infraorder are monophyletic. Thalassinidea, however, is polyphyletic. The nodal support for most of the infraordinal and inter-familial relationships is high. Stenopodidea and Caridea form a clade sister to Reptantia, which comprises two major clades. The first clade, consisting of Astacidea, Achelata, Polychelida and three thalassinidean families (Axiidae, Calocarididae and Eiconaxiidae), corresponds essentially to the old taxon suborder Macrura Reptantia. Polychelida nests within Macrura Reptantia instead of being the most basal reptant as suggested in previous studies. The high level of morphological and genetic divergence of Polychelida from Achelata and Astacidea justifies its infraorder status. The second major reptant clade consists of Anomura, Brachyura and two thalassindean families (Thalassinidae and Upogebiidae). Anomura and Brachyura form Meiura, with moderate support. Notably thalassinidean families are sister to both major reptant clades, suggesting that the stem lineage reptants were thalassinidean-like. Moreover, some families (e.g. Nephropidae, Diogenidae, Paguridae) are paraphyletic, warranting further studies to evaluate their status. The present study ably demonstrates the utility of nuclear protein-coding genes in phylogenetic inference in decapods. The topologies obtained are robust and the two molecular markers are informative across a wide range of taxonomic levels. We propose that nuclear protein-coding genes should constitute core markers for future phylogenetic studies of decapods, especially for higher systematics.     

The complete mitochondrial genome of the mantid shrimp Harpiosquilla harpax, and a phylogenetic investigation of the Decapoda using mitochondrial sequences

The complete mitochondrial DNA sequence was determined for the mantid shrimp Harpiosquilla harpax. These data demonstrate that the H. harpax mitochondrial genome is a 15,714 bp circular molecule and encodes the typical 37 metazoan mitochondrial genes (13 protein-coding, 22 tRNA, and two rRNA genes). The gene arrangement of H. harpax is consistent with that of the putative arthropod ancestral gene order as depicted by Limulus polyphemus. H. harpax was employed as an outgroup taxon for a phylogenetic investigation of the Decapoda using sequences from complete mitochondrial genomes. Whilst our results are largely in agreement with current taxonomic treatments, the relationships indicated among the reptantian decapods are novel. Our results provide strong statistical support for a sister-group relationship between the Achelata and the Astacida. These findings not only refute previous phylogenetic hypotheses, but also have serious implications for the interpretation of morphological and developmental evolution in the Decapoda. In addition we also investigated the effects of outgroup selection on the resolution of ingroup relationships. We found outgroup choice to significantly influence tree topology thus reinforcing the importance of appropriate outgroup selection in phylogenetic studies.     

Model-based multi-locus estimation of decapod phylogeny and divergence times

Phylogenetic relationships among all of the major decapod infraorders have never been estimated using molecular data, while morphological studies produce conflicting results. In the present study, the phylogenetic relationships among the decapod basal suborder Dendrobranchiata and all of the currently recognized decapod infraorders within the suborder Pleocyemata (Caridea, Stenopodidea, Achelata, Astacidea, Thalassinidea, Anomala, and Brachyura) were inferred using 16S mtDNA, 18S and 28S rRNA, and the histone H3 gene. Phylogenies were reconstructed using the model-based methods of maximum likelihood and Bayesian methods coupled with Markov Chain Monte Carlo inference. The phylogenies revealed that the seven infraorders are monophyletic, with high clade support values (bp>70; pP>0.95) under both methods. The two suborders also were recovered as monophyletic, but with weaker support (bp=70; pP=0.74). Although the nodal support values for infraordinal relationships were low (bp<50; pP<0.77) the Anomala and Brachyura were basal to the rest of the 'Reptantia' in both reconstructions and using Bayesian tree topology tests alternate morphology-based hypotheses were rejected (P<0.01). Newly developed multi-locus Bayesian and likelihood heuristic rate-smoothing methods to estimate divergence times were compared using eight fossil and geological calibrations. Estimated times revealed that the Decapoda originated earlier than 437MYA and that the radiation within the group occurred rapidly, with all of the major lineages present by 325MYA. Node time estimation under both approaches is severely affected by the number and phylogenetic distribution of the fossil calibrations chosen. For analyses incorporating fossils as fixed ages, more consistent results were obtained by using both shallow and deep or clade-related calibration points. Divergence time estimation using fossils as lower and upper limits performed well with as few as one upper limit and a single deep fossil lower limit calibration.     

Phylogenetic analysis of the Brachyura (Crustacea, Decapoda) based on characters of the foregut with establishment of a new taxon

The Brachyura, within the decapod crustaceans, is one of the most species-rich taxa with up to 10 000 species. However, its phylogenetic history, evolution and fossil record remain subjects of controversy. In our study, we examined the phylogenetic relationships of the Brachyura based on morphological characters of the foregut. The cladistic analysis supports a monophyletic Brachyura including the Dromiidae and Raninidae. A clade comprising Dromiidae and Dynomenidae forms the most basal assemblage within the Brachyura, followed by the Homolidae and Latreilliidae. As a result, neither Podotremata nor Archaeobrachyura form a clade. In contrast, foregut data suggest that the classical taxon Oxystomata, comprising Calappidae, Parthenopidae, Dorippidae, Leucosiidae, Cymonomidae and Raninidae, is monophyletic. This makes the Heterotremata paraphyletic or polyphyletic. A newly established taxon, Neobrachyura, embraces some representatives of the Heterotremata and the monophyletic Thoracotremata.     

Comparative study of the stomatogastric system of several decapod crustacea. I. Skeleton

The skeletal structure of the stomachs of several decapod Crustacea is described in detail. The general organization of the ossicles is similar for all species and the homologies of the elements can be recognized despite large variations from group to group. The Reptantia are characterized by a complex ossicle organization while the Natantia, on the other hand, are characterized by a simple organization. The various types of ossicle organization found in the decapod stomach can be arranged in a series ranging from simple to complex. The Brachyura have the most complex ossicle system and the Penaeidea the most simplified. This graded series of complexity closely follows the evolution of the Decapoda.     

Characterization of the complete mitochondrial genome of Uca lacteus and comparison with other Brachyuran crabs

Brachyuran crabs comprise the most species-rich clade among the crustacean order Decapoda and are divided into several major superfamilies. However, the monophyly of the superfamilies Ocypodoidea and Grapsoidea in their current compositions within the Brachyura remains inconclusive. In this study, the complete mitochondrial genome (mitogenome) of Uca lacteus (Ocypodoidea, Ocypodidae) was sequenced, annotated, and compared with those of other Brachyuran crabs. The circular mitogenome of U. lacteus is 15,661 base pairs long and contains the entire set of 37 genes and an A + T-rich region typically observed in decapod mitogenomes. Secondary structures of several tRNAs are partly missing (trnS1), and the number of bases is significantly decreased (trnD and trnF), as discovered in many other metazoans. We compared the gene order of U. lacteus with other species of Ocypodidae and found that they are consistent. The gene rearrangement of Ocypodidae is also identical to that of the ancestor of Brachyura. However, the order of the trnH gene varies from the rearrangement of ancestral Decapoda. Accordingly, we hypothesized that this rearrangement of trnH underwent a translocation during the evolution from Decapoda to Brachyura. The phylogenetic relationship of the 81 Brachyura species and one outgroup was recovered based on 13 protein-coding genes. This analysis confirmed that U. lacteus belongs to the family Ocypodidae and established a paraphyletic relationship between Ocypodoidea and Grapsoidea.     

Phylogenetic relationships and genetic distances between some monostiliferous interstitial nemerteans (Ototyphlonemertes, Hoplonemertea, Nemertea) indicated from the 16s rRNA gene

Part of the 16s rRNA mitochondrial gene is used to reconstruct the relationships within five populations (representing three currently recognized species) of interstitial nemerteans ( Ototyphlonemertes , Hoplonemertea, Nemertea), and to assess genetic divergence between representatives of these populations. The non-helicophoran individuals form a monophyletic sister-group to the helicophoran taxon, which further resolves a previous hypothesis based on morphological characters. The small nucleotide differences between some of the populations are within levels expected for panmictic populations and fail to distinguish them genetically; without applying a phylogenic perspective, some of the populations may be allocated into paraphyletic species assemblages.     

Ribosomal DNA phylogeny of the Bangiophycidae (Rhodophyta) and the origin of secondary plastids

We sequenced the nuclear small subunit ribosomal DNA coding region from 20 members of the Bangiophycidae and from two members of the Florideophycidae to gain insights into red algal evolution. A combined alignment of nuclear and plastid small subunit rDNA and a data set of Rubisco protein sequences were also studied to complement the understanding of bangiophyte phylogeny and to address red algal secondary symbiosis. Our results are consistent with a monophyletic origin of the Florideophycidae, which form a sister-group to the Bangiales. Bangiales monophyly is strongly supported, although Porphyra is polyphyletic within Bangia. Bangiophycidae orders such as the Porphyridiales are distributed over three independent red algal lineages. The Compsopogonales sensu stricto, consisting of two freshwater families, Compsopogonaceae and Boldiaceae, forms a well-supported monophyletic grouping. The single taxon within the Rhodochaetales, Rhodochaete parvula, is positioned within a cluster containing members of the Erythropeltidales. Analyses of Rubisco sequences show that the plastids of the heterokonts are most closely related to members of the Cyanidiales and are not directly related to cryptophyte and haptophyte plastid genomes. Our results support the independent origins of these secondary algal plastids from different members of the Bangiophycidae.     

Interrelationships of lower actinopterygian fishes

The lower actinopterygian fishes are classified using dermal skull roof pattern, in particular the various configurations displayed by the bones on the otic branch of the infraorbital canal (dermosphenotic, intertemporal-supratemporal/dermopterotic). Where possible these patterns are related to the sequential acquisition of derived features, and the resulting cladogram represents a synthesis of dermal bone pattern and endochondral and dermal skeletal characters. We have proposed 27 terminal groups which we tentatively regard as monophyletic and have concluded that Polypterus is the most primitive living taxon, that the Chondrostei is the sister-group of Saurichthys and Luganoia the most derived stem-group neopterygian.     

Interrelationships of the ostariophysan fishes (Teleostei)

The history of ostariophysan classification is summarized and it is noted that traditional concepts of relationships have never been supported by characters found to be unique to the taxa. We present a new hypothesis of relationships among four of the five major ostariophysan lineages: Cypriniformes, Characiformes, Siluroidei, and Gymnotoidei (Otophysi). Cypriniforms are the sister-group of the remaining three (Characiphysi), and characiforms are the sister-group of siluroids plus gymnotoids (Siluriformes). Placement of the Gonorynchiformes as the sister-group of the Otophysi is supported by additional evidence. Each of the five lineages is monophyletic. Analysis was concentrated upon species thought to be the least specialized within each lineage; choices of these species are discussed. Chanos is determined to be a relatively primitive gonorynchiform morphologically and the sister-group of all other Recent members of the order. Opsariichthys and Zacco are found to be morphologically primitive cypriniforms. We propose that a monophyletic group comprising the Citharinidae and Distichodontidae forms the sister-group of all other characiforms. Within the two families, Xenocharax is the least specialized. We suggest that Hepsetus, the erythrinids, and the ctenoluciids are more derived than the distichodontids and citharinids, and may form a monophyletic group within die characiforms. The traditional hypothesis that Diplomystes is the primitive sister-group of all Recent siluroids is substantiated. Our evidence suggests that Sternopygus is the most primitive gymnotoid morphologically; but rather than being the sister-group of all other gymnotoids, it is the primitive sister-group within a lineage called the Sternopygidae by Mago-Leccia. Previous explanations of otophysan distribution have been based on notions of relationships which are unsupported by the evidence presented herein. Our own analysis of relationships serves primarily to make clear the extent of sympatry, and therefore the probability of dispersal, among the major ostariophysan lineages. The extent of sympatry, together with the widespread distribution of ostariophysans, suggests that the group is older than previously supposed, and our hypotheses of relationships among the characiforms implies that many of the extent characiform lineages evolved before the separation of Africa and South America. Further understanding of ostariophysan distribution must await phylogenetic analysis within each of the five major lineages so that distributions linked with vicariance patterns and dispersal events can be sorted out.     

The Entire Mitochondrial Genome of Macrophthalmus abbreviatus Reveals Insights into the Phylogeny and Gene Rearrangements of Brachyura

Brachyuran crabs comprise the most species-rich clades among extant Decapoda and are divided into several major superfamilies. However, the phylogeny of Brachyuran remains controversial, comprehensive analysis of the overall phylogeny is still lacking. Complete mitochondrial genome (mitogenome) can indicate phylogenetic relationships, as well as useful information for gene rearrangement mechanisms and molecular evolution. In this study, we firstly sequenced and annotated the complete mitogenome of Macrophthalmus abbreviatus (Brachyura; Macrophthalmidae). The mitogenome length of M. abbreviatus is 16,322 bp, containing the entire set of 37 genes and a control region typically observed in Brachyuran mitogenomes. The genome composition of M. abbreviatus was highly A+T biased 76.3% showing positive AT-skew (0.033) and negative GC-skew (??0.351). In M. abbreviatus mitogenome, most tRNA genes were folded into the clover-leaf secondary structure except trnH, trnS1 and trnC, which was similar to the other species in Macrophthalmidae. Phylogenetic analysis showed that all families form a monophyletic, and Varunidae and Macrophthalmidae clustered into a monophyletic clade as sister groups. Comparative analyses of rearrangement among Brachyura revealed that Varunidae (Grapsoidea) and Macrophthalmidae (Ocypodoidea) had the same gene order, which reinforced the result of phylogeny. The combined results of two aspects revealed that the polyphyly of Ocypodoidea and Grapsoidea were well supported. In general, the results obtained in this research will contribute to further studies on molecular based for the classification and gene rearrangements of Macrophthalmidae or even Brachyura.

     

Squamate phylogeny and the relationships of snakes and mosasauroids

Cladistic analysis of extant and fossil squamates (95 characters, 26 taxa) finds the fossil squamate, Coniasaurus Owen, 1850, to be the sister-group of the Mosasauroidea (mosasaurs and aigialosaurs). This clade is supported in all 18 shortest cladograms (464 steps; CI 0.677; HI 0.772) by nine characters of the dermatocranium, maxilla, and mandible. A Strict Consensus Tree of the 18 shortest trees collapses to a basal polytomy for most major squamate clades including the clade (Coniasaurus, Mosasauroidea). A Majority Rule Consensus Tree shows that, in 12 of 18 shortest cladograms, the clade Coniasaurus- Mosasauroidea is the sister-group to snakes (Scolecophidia (Alethinophidia, Dinilysia); this entire clade, referred to as the Pythonomorpha ([[Scolecophidia [Alethinophidia, Dinilysia]], [Coniasaurus, Mosasauroidea]]) is the sister-group to all other scleroglossans. Pythonomorpha is supported in these 12 cladograms by nine characters related to the lower jaw and cranial kinesis. In 6 of 18 shortest cladograms, snakes are the sister-group to the clade (Amphisbaenia (Dibamidae (Gekkonoidea, Eublepharidae))). None of the cladograms support the hypothesis that coniasaurs and mosasauroids are derived varanoid anguimorphs. Two additional analyses were conducted: (1) manipulation and movement of problematic squamate clades while constraining ‘accepted’ relationships; (2) additional cladistic analyses beginning with extant taxa, and sequentially adding fossil taxa. From Test I, at 467 steps, Pythonomorpha can be the sister-group to the Anguimorpha, Scincomorpha, ‘scinco-gekkonomorpha’ [scincomorphs, gekkotans, and amphibaenids-dibamids]. At 471 steps Pythonomorpha can be placed within Varanoidea. Treating only mosasauroids and coniasaurs as a monophyletic group: 469 steps, mosasauroids and coniasaurs as sister-group to Anguimorpha; 479 steps, mosasauroids and coniasaurs nested within Varanoidea. Test II finds snakes to nest within Anguimorpha in a data set of only Mosasauroidea + Extant Squamates; the sistergroup to snakes + anugimorphs is (Amphisbaenia (Dibarnidae (Gekkonoidea, Eublepharidae))). No one particular taxon is identified as a keystone taxon in this analysis, though it appears truc that fossil taxa significantly alter the structure of squamate phylogenetic trees.     

Phylogeny of the Anomala (Crustacea, Decapoda, Reptantia) based on the ossicles of the foregut

We present a cladistic analysis of the Anomala based on 66 ingroup species and 5 outgroup representatives. Based on a comparative analysis of the morphology of the foregut we scored 124 characters related to size, shape, and fusion of foregut ossicles and other foregut structures. Our parsimony analysis resulted in 30 equally parsimonious trees which differ mainly at the lower hierarchical level. Our study reveals two large clades within Anomala. One large clade consists of Galatheoidea and Chirostyloidea. The internal relationships show a monophyletic Porcellanidae nested within a group comprising paraphyletic Galatheidae, and Munididae as well as Munidopsidae. The other large clade contains Aegla as sister group to a monophyletic group consisting of the Hippoidea and a clade formed by Lomis and the Paguroidea. Coenobitidae are nested within paraphyletic Diogenidae and Lithodidae are nested within paraphyletic Paguridae. The results are discussed in the context of other morphological and molecular analyses. Furthermore, some aspects of carcinization are touched upon; in particular, an anomalan stem species with a, at least to some extent, ventrally folded pleon is suggested.     

Molecular phylogeny of the brachyuran crab superfamily Majoidea indicates close congruence with trees based on larval morphology

In this study, we constructed the first molecular phylogeny of the diverse crab superfamily Majoidea (Decapoda: Pleocyemata: Brachyura), using three loci (16S, COI, and 28S) from 37 majoid species. We used this molecular phylogeny to evaluate evidence for phylogenetic hypotheses based on larval and adult morphology. Our study supports several relationships predicted from larval morphology. These include a monophyletic Oregoniidae family branching close to the base of the tree; a close phylogenetic association among the Epialtidae, Pisidae, Tychidae, and Mithracidae families; and some support for the monophyly of the Inachidae and Majidae families. However, not all majoid families were monophyletic in our molecular tree, providing weaker support for phylogenetic hypotheses inferred strictly from adult morphology (i.e., monophyly of individual families). This suggests the adult morphological characters traditionally used to classify majoids into different families may be subject to convergence. Furthermore, trees constructed with data from any single locus were more poorly resolved than trees constructed from the combined dataset, suggesting that utilization of multiple loci are necessary to reconstruct relationships in this group.     

The mitochondrial genomes of Cambaroides similis and Procambarus clarkii (Decapoda: Astacidea: Cambaridae): the phylogenetic implications for Reptantia

Kim, S., Park, M.‐H., Jung, J.‐H., Ahn, D.‐H., Sultana, T., Kim, S., Park, J.‐K., Choi, H.‐G. & Min, G.‐S. (2012). The mitochondrial genomes of Cambaroides similis and Procambarus clarkii (Decapoda: Astacidea: Cambaridae): the phylogenetic implications for Reptantia. —Zoologica Scripta, 41, 281–292. We determined the complete mitochondrial (mt) genome sequences of two northern hemisphere freshwater crayfish species, Cambaroides similis and Procambarus clarkii (Decapoda: Astacidea: Cambaridae). These species have an identical gene order with typical metazoan mt genome compositions. However, their gene arrangement was very distinctive compared with the pan‐crustacean ground pattern because of the presence of a long inverted block, which included 19 coding genes and a control region (CR). Because the CR was inverted, their nucleotide frequencies showed a reversed strand‐specific bias compared with the other decapods. Based on a comparative analysis of mt genome arrangements between southern and northern hemisphere crayfish and their putative close marine relative (Homarus americanus, a true clawed lobster), we postulated that the ancestor of freshwater crayfish had a typical pan‐crustacean mtDNA gene order, similar to its marine relatives. Based on this assumption, we traced the most parsimonious gene rearrangement scenario of the northern hemisphere crayfish. In a phylogenetic study on the infraordinal relationships in reptan decapods, the lineage Lineata [Thalassinidea (Brachyura, Anomura)] was well supported, while the infraorder positions of Achelata and Astacidea remained unidentified.     

Reptile phylogeny and the interrelationships of turtles

A comprehensive analysis of amniote interrelationships is presented in an attempt to test turtle interrelationships. The results refute earlier hypotheses that turtles are related to parareptiles, i.e. to procolophonids or pareiasaurs. Instead, turtles are shown to be the sister-group of Sauropterygia, the two clades being nested within Sauria as sister-group of Lepidosauriformes. This scenario is also supported by several developmental and soft tissue characters which are shown to be congruent with the current phylogeny. The analysis strongly supports a monophyletic Parareptilia, sister-group of a monophylctic Eurcptilia. The Diapsida, however, is paraphyletic unless it includes turtles and sauropterygians. Additionally, the position of turtles within Diapsida has major implications for the evolutionary history and/or significance of many characters, i.e. temporal fenestration.     

Recent vicariant and dispersal events affecting the phylogeny and biogeography of East Asian freshwater crab genus Nanhaipotamon (Decapoda: Potamidae)

The molecular phylogeny and biogeography of the East Asian freshwater crabs of the genus Nanhaipotamon (Decapoda: Brachyura: Potamidae) were studied, using two mitochondrial (16S rRNA and cytochrome oxidase I) and one nuclear (28S rRNA) markers, and correlated with various vicariant and dispersal events which have occurred in this region. The results showed Nanhaipotamon to be a monophyletic taxon with four clades which correspond to the topography of the coastal region of southeastern China and Taiwan Island. Mountains appear to play an important role in the distribution. The genus occurs only from east of the Wuyishan Range (Zhejiang and Fujian) and south of the Nanling Range (Guangdong) in southern China, and is also present west of the Central Range in Taiwan. The molecular and geological data suggest that Nanhaipotamon originated in an area between the Wuyishan and Nanling Ranges. In this area, the main and earliest cladogenesis occurred at ～4.8 million years ago (mya), with speciation probably taking place at around 4mya. The molecular evidence strongly supports the recent invasion of the genus into Taiwan Island from northeastern Fujian, via the paleo-Minjiang River on the landbridge of Taiwan Strait. The presence of the genus in Dongyin Island, however, is through invasion from southeastern Zhejiang, during the Pleistocene glaciation period. Nanhaipotamon reached Taiwan and Dongyin Island at ～1.0 and 0.4 mya, respectively. A small population of Nanhaipotamon formosanum from Penghu Islands (Pescadores) in the central Taiwan Strait has a slightly different genetic constitution and suggests it is a relict of past Pleistocene glaciations.     

Genets and 'genet-like' taxa (Carnivora, Viverrinae): phylogenetic analysis, systematics and biogeographic implications

The subfamily Viverrinae is a taxon of uncertain systematic status. This study consists of cladistic analyses based on morphological characters of specimens belonging to the genera Genetta , Osbornictis , Poiana and Prionodon . Two levels of analysis are carried out, one concerning generic relationships (intergeneric analysis) and one dealing with the interrelationships of species within the genus Genetta (intrageneric analysis). In the first analysis, different outgroups were used in order to test the ingroup topology.
With regard to the intergeneric analysis, Osbornictis , Poiana and Prionodon , together with Genetta johnstoni , constitute a monophyletic group (including Nandinia ), which is the sister-group of a clade formed by the other species of genets. Thus, the genus Genetta is regarded as paraphyletic. Prionodon appears to be a derived taxon. The Poiana – Prionodon clade is well supported, especially by ultrastructural hair characters. The cladogram topology in the intrageneric analysis indicates an ecological transition from the rain forest genets to the savanna genets. This supports a rain forest origin of the genus Genetta , a conclusion which may be generalized to the entire study group. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society , 2002, 134 , 317–334.     

Environmental effects on fished lobsters and crabs

The fisheries for crabs and lobsters (Reptantia, Decapoda) are shaped by environmental variation through the distribution ecology, productivity or even their market traits such as colour and size. Many crabs and lobsters have a wide latitudinal distribution and therefore are exposed to significant abiotic gradients throughout their geographic range. Environmental factors affect reptantians throughout their complex life cycle, including embryo development, timing and length of the spawning period, the duration and quality of the larval stages, the level and spatial distribution of the settlement, growth rates and size of the juveniles, size at maturity, and catchability. The most consistent environmental response is of growth and reproduction to temperature. Growth rates increase with increasing temperatures in a parabolic function, tapering and then declining as the boundaries of thermal tolerance are reached. With increasing temperature the intermoult duration decreases. Once the upper thermal boundary is reached, increases in temperature result in longer intermoult duration and smaller growth increments so that growth is reduced. Declines in temperature generally suppress moulting, and consequently reptantians rarely moult in winter. Increasing temperature decreases the time for egg incubation, larval development and the maturational age. Catchability increases with water temperature and also varies, although less predictably, with moon phase and wind strength. Catchability decreases with an increase in population density. Larval settlement of many reptantian species depends on current strength, increasing with the strength of certain local currents. Reptantians can tolerate a wide-variety of conditions and have flexible life-histories to respond to conditions throughout their broad geographic ranges. Information on environmental effects on reptantians not only assists in understanding probable effects of ocean warming and acidification, but also seasonal and interannual changes in fisheries production.