Stable Clades Research Articles

The Complete Mitochondrial Genomes of Aelia sibirica and A. fieberi (Hemiptera, Pentatomidae), and Phylogenetic Implications

Species of genus Aelia are important pests of wheat crops in arid areas. In this study, the mitogenomes of A. sibirica and A. fieberi were sequenced using high-throughput sequencing technology. The mitochondrial genome characteristics of both Aelia species were compared and analyzed, and the phylogenetic relationships of Pentatomidae were constructed based on protein-coding genes. In addition, the taxonomic status of the genus Aelia was confirmed. The results showed that the total length of the mitogenome sequences of A. sibirica and A. fieberi were 15,372 bp and 15,450 bp, respectively, including 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes, and a control region. By comparing the mitochondrial genome structure, base composition, codon usage, RNA secondary structure, and other characteristics, it was found that the mitochondrial genome characteristics of the two species were similar. Phylogenetic analysis showed that Phyllocephalinae and Asopinae both formed monophyletic groups, but the relationship between Podopinae and Pentatominae was not resolved. Within the subfamily Pentatominae, (Nezarini + Antestiini), (Aeliini + Carpocorini), and (Strachiini + Pentatoma) formed stable clades. Aelia sibirica and A. fieberi were found to be a stable sibling pair, and the clade was closely related to Dolycoris baccarum.

Systematic Redefinition of the Hypotricha (Alveolata, Ciliophora) Based on Combined Analyses of Morphological and Molecular Characters

The systematics of Hypotricha is one of the most puzzling problems in ciliate biology, having spanned numerous conflicting hypotheses with unstable relationships at various levels in molecular trees, for which the constant addition of newly discovered species has only increased the confusion. The hypotrichs comprise a remarkable morphologically diversified group of ciliates, and the phylogenetic potential of morphological traits is generally recognized. However, such characters were rarely used in phylogenetic reconstructions, and congruence with molecular data never assessed from simultaneous analyses. To properly reconciliate morphological and molecular information, maximum-likelihood and parsimony analyses of 79 morphological characters and 18S rDNA sequences were performed for 130 ingroup terminals, broadly sampled to represent the known hypotrich diversity. As result, well-supported and relatively stable clades were recovered, based on which the redefined Hypotricha comprises at least six higher taxa: The "arcuseriids", Holostichida, Parabirojimida, and the "amphisiellids", plus the two large clades Kentrurostylida nov. tax. (Hispidotergida nov. tax. and Simplicitergida nov. tax.) and Diatirostomata nov. tax. ("bistichellids", "kahliellids", Gonostomatida and Dorsomarginalia [Postoralida nov. tax. and Uroleptida]). Each taxon was circumscribed by synapomorphies, of which most were homoplastic, as the natural history of hypotrichs is portrayed by an outstanding quantity of convergences and reversions.

Phylogenetic relationships and classification of the Chloropinae of the world (Diptera: Chloropidae)

Abstract The Chloropidae is a species-rich family of flies with about 3000 species in four subfamilies. The Chloropinae is the second most species-rich subfamily with almost 1000 described species in 75 accepted genera. There is agreement about the monophyly of the subfamily; however, the relationships among the genera are still poorly understood and some genera are clearly paraphyletic. Thus, the interpretation of the evolution of morphological traits, such as male terminalia sclerites, remains challenging. This is the first phylogenetic study of the Chloropinae using a formal analytical approach, including representatives of 73 genera of the subfamily and 124 morphological characters. The monophyly of the Chloropinae is corroborated. Chloropella is sister to the remainder of the subfamily. Slightly different analytical procedures show stable clades and rogue taxa. We propose a system for the subfamily with ten tribes, three of which are newly proposed here—Chloropellini trib. nov., Chloropini, Chloropsinini trib. nov., Diplotoxini, Eurinini stat. nov., Lasiosinini, Mepachymerini, Meromyzini, Mindini and Pseudothaumatomyini. Eight genera are kept incertae sedis and two new genera are erected. There is compelling evidence that Chlorops and Ectecephalina are paraphyletic.

Phylogeny and reclassification of Cryptini (Hymenoptera, Ichneumonidae, Cryptinae), with implications for ichneumonid higher‐level classification

AbstractThe first comprehensive phylogenetic study of the wasp tribe Cryptini (Hymenoptera, Ichneumonidae, Cryptinae) is presented, based on 109 morphological characters and molecular data from seven loci. The dataset includes 370 species, 308 of which are from Cryptini, covering 182 of its 250 genera. Results from parsimony and likelihood analyses are generally congruent. The topology has several implications for ichneumonid higher‐level classification. Previous definitions of the Ichneumoniformes clade are supported, though newly including the Microleptinae. The cryptine subtribe Ateleutina is consistently recovered outside of the Cryptini clade and should be treated as a separate subfamily, Ateleutinae stat.n. The tribe Phygadeuontini is shown to be polyphyletic: while most of the sampled taxa were recovered in a single clade, many of its members are more closely related to the Ichneumoninae, Ateleutinae or Cryptini. Pending a more detailed study, the group should be treated as a separate subfamily, Phygadeuontinae stat. rev. The former Hemigastrini are recovered as largely monophyletic but with important exceptions. Hemigaster Brullé is recovered as part of the Phygadeuontini and is transferred to that group. Echthrus Gravenhorst is consistently recovered as part of Cryptini, rendering Aptesini as the correct name for the tribe. The subfamily Cryptinae should be restricted to the tribes Aptesini and Cryptini. Within Cryptini, the results show little support for the current subtribal classification, with most subtribes recovered as polyphyletic. A number of relatively stable clades are identified and discussed, but the relationships among them are weakly supported. Most of these clades are morphologically heterogeneous and building a subtribal classification based on them would be ineffectual; they are therefore treated under the informal designation of genus groups. The results highlight the ubiquity of morphological homoplasy in Cryptini, and provide a framework from which to address further systematic and evolutionary questions on this hyperdiverse group of parasitic wasps.

Phylogeny and chromosomal diversification in the Dichroplus elongatus species group (Orthoptera, Melanoplinae).

In an attempt to track the chromosomal differentiation in the Dichroplus elongatus species group, we analyzed the karyotypes of four species with classical cytogenetic and mapping several multigene families through fluorescent in situ hybridization (FISH). We improved the taxon sampling of the D. elongatus species group adding new molecular data to infer the phylogeny of the genus and reconstruct the karyotype evolution. Our molecular analyses recovered a fully resolved tree with no evidence for the monophyly of Dichroplus. However, we recovered several stable clades within the genus, including the D. elongatus species group, under the different strategies of tree analyses (Maximum Parsimony and Maximum Likelihood). The chromosomal data revealed minor variation in the D. elongatus species group’s karyotypes caused by chromosome rearrangements compared to the phylogenetically related D. maculipennis species group. The karyotypes of D. intermedius and D. exilis described herein showed the standard characteristics found in most Dichroplini, 2n = 23/24, X0♂ XX♀, Fundamental number (FN) = 23/24. However, we noticed two established pericentric inversions in D. intermedius karyotype, raising the FN to 27♂/28♀. A strong variation in the heterochromatic blocks distribution was evidenced at interespecific level. The multigene families’ mapping revealed significant variation, mainly in rDNA clusters. These variations are probably caused by micro chromosomal changes, such as movement of transposable elements (TEs) and ectopic recombination. These observations suggest a high genomic dynamism for these repetitive DNA sequences in related species. The reconstruction of the chromosome character “variation in the FN” posits the FN = 23/24 as the ancestral state, and it is hypothesized that variations due to pericentric inversions has arisen independently three times in the evolutionary history of Dichroplus. One of these independent events occurred in the D. elongatus species group, where D. intermedius is the unique case with the highest FN described in the tribe Dichroplini.

Molecular phylogeny of four ascidian species inferred from mitochondrial Cytochrome Oxidase subunit I (COI) sequence

Ascidians is a crucial group for the studies of deuterostome evolution and the origin of chordates, yet little molecular work has been done to determine the evolutionary relationships and largely unexplored beyond a few species. The phylogenetic analysis are presented for four different species of solitary ascidians, Ascidia virginea, Ascidiella aspersa, Clavelina oblonga and Aplidium fuscum, obtained from Great Nicobar Biosphere reserve (GNBR). Mitochondrial Cytochrome Oxidase subunit 1(COI) gene was amplified and the genetic diversity at the phylogenic level was measured. Bar-coded sequences were extracted with BLAST format from NCBI and the genetic diversity of the submitted sequences were compared with the related ascidian species. Maximum divergences measured among the four species were as follows: Ascidia virginea (96%), Ascidiella aspersa (96%), Clavelina oblonga (94%) and Aplidium fuscum (97%). This is the first report of molecular phylogeny of ascidians from Great Nicobar Biosphere Reserve, Andaman and Nicobar Islands. From this study, we found some stable clades on the evolutionary relationships among these ascidian species that may prompt a reevaluation of some morphological characters.

Multi-gene-based phylogenetic analysis of oligotrich ciliates with emphasis on two dominant groups: Cyrtostrombidiids and strombidiids (Protozoa, Ciliophora)

Phylogenetic analyses of ciliated protists are frequently based on single molecular markers, usually the small subunit ribosomal RNA gene (SSU rDNA), despite the well-known limitations of this approach. Here, 78 new sequences of three linked genes (SSU rDNA, ITS1-5.8S rDNA-ITS2, LSU rDNA) were characterized and applied to phylogenetic analyses of oligotrichs (s. str.). It was found that: (1) three taxa, that is tontoniids, pelagostrombidiids and cyrtostrombidiids should be split from the family Strombidiidae (s. l.), which supports Agatha’s classification based on morphological characters; (2) the families Tontoniidae and Cyrtostrombidiidae are both monophyletic whereas Strombidiidae is polyphyletic; (3) the positions of the families Cyrtostrombidiidae and Pelagostrombidiidae varied in different trees although with low support values; (4) the close relationship between Varistrombidium and Apostrombidium is confirmed, which updates the evolutionary hypothesis for oligotrichs based on ciliary patterns; and (5) two relatively stable clades were found in the family Strombidiidae.

Molecular phylogeny of Pamphagidae (Acridoidea, Orthoptera) from China based on mitochondrial cytochrome oxidase II sequences

Phylogenetic relationships of Pamphagidae were examined using cytochrome oxidase subunit II (COII) mtDNA sequences (684 bp). Twenty-seven species of Acridoidea from 20 genera were sequenced to obtain mtDNA data, along with four species from the GenBank nucleotide database. The purpose of this study was analyzing the phylogenetic relationships among subfamilies within Pamphagidae and interpreting the phylogenetic position of this family within the Acridoidea superfamily. Phylogenetic trees were reconstructed using neighbor-joining (NJ), maximum parsimony (MP) and Bayesian inference (BI) methods. The 684 bp analyzed fragment included 126 parsimony informative sites. Sequences diverged 1.0%–11.1% between genera within subfamilies, and 8.8%–12.3% between subfamilies. Amino acid sequence diverged 0–6.1% between genera within subfamilies, and 0.4%–7.5% between subfamilies. Our phylogenetic trees revealed the monophyly of Pamphagidae and three distinct major groups within this family. Moreover, several well supported and stable clades were found in Pamphagidae. The global clustering results were similar to that obtained through classical morphological classification: Prionotropisinae, Thrinchinae and Pamphaginae were monophyletic groups. However, the current genus Filchnerella (Prionotropisinae) was not a monophyletic group and the genus Asiotmethis (Prionotropisinae) was a sister group of the genus Thrinchus (Thrinchinae). Further molecular and morphological studies are required to clarify the phylogenetic relationships of the genera Filchnerella and Asiotmethis.

Phylogeny of the bristle worm family Eunicidae (Eunicida, Annelida) and the phylogenetic utility of noncongruent 16S, COI and 18S in combined analyses

The bristleworm family Eunicidae is distributed worldwide and well-known for the large size of many of its species, its hard jaws and its economic importance in the bait industry. Monophyly of Eunicidae has been contradicted in previous molecular and morphological phylogenetic analyses focusing on Eunicida or on its type genus, Eunice. The current study focused on the phylogeny of the family per se combining mitochondrial and nuclear genes in different analyses. It recovered well-resolved phylogenetic hypotheses supporting the monophyly of Eunicidae and Palola, the only monophyletic genus among the genera for which we tested their monophyly ( Eunice, Marphysa, Palola, Lysidice and Nematonereis). Four other stable clades containing the type species of different genera, or species deemed very similar to them, were recovered within Eunicidae. These clades may represent monophyletic redefinitions of current genera, except for Eunice, and of previous synonymized genera. Evolution of the number of peristomial cirri and prostomial appendages in Eunicidae happened by independent step-by-step reduction in the opposite order of their ontogenetic development, suggestive of sequential heterochrony. All three genes were informative, however, at different levels within the combined trees. 16S and COI were important in recovering a monophyletic Eunicidae and relationships within the family, while 18S was important in the resolution of basal eunicidan relationships, monophyly of Onuphidae and basal relationships within this family. Moreover, results of congruence tests (SH and WRST using PABA) indicate that hidden support is picked up in the combined analyses, which is not revealed in the single gene analyses. Further supporting the idea that congruence is not a requirement for combining different partitions.

Phylogeny of Apaturinae Butterflies (Lepidoptera: Nymphalidae) Based on Mitochondrial Cytochrome Oxidase? Gene

The phylogenetic relationships of genera in the subfamily Apaturinae were examined using mtDNA sequence data from 1,471 bp of cytochrome oxidase subunit?( COI). The mitochondrial COI gene from a total of 16 species in 11 genera were sequenced to obtain mtDNA data, along with those of 4 species obtained from GenBank, to construct the MP and the NJ trees using Athyma jina, Penthema adelma, Polyura nepenthes, and Charaxes bernardus as outgroups. The transitions at the third codon positions of the COI data set were found saturated, but they were retained for analysis, because they contain the majority of the phylogenetic information. The impacts of equal weight assumptions for all characters in the parsimonious analysis were assessed by potential alternations in clades in response to different transition/transversion weighting schemes. The results indicated four distinct major groups in Apaturinae. Moreover, several well supported and stable clades were found in the Apaturinae. The study also identified undetermined taxon groups whose positions were weakly supported and were subject to changes under different weighting schemes. Within the Apaturinae, the clustering results are approximately identical to the classical morphological classification. The mtDNA data suggest the genus Mimathyma as a monophyletic group. Lelecella limenitoides and Dilipa fenestra have close relationship with very strong support in all phylogenetic trees. It also supports the taxonomic revision of removing several species from Apatura to other genera, namely Mimathyma schrenckii, M. chevana, M. nycteis, Chitoria subcaerulea, C. fasciola, C. pallas, and Helcyra subalba.

The importance of looking at small-scale patterns when inferring Gondwanan biogeography: a case study of the centipedeParalamyctes(Chilopoda, Lithobiomorpha, Henicopidae)

Gondwanan biogeography has fascinated zoologists and botanists for over a century, but most biogeographical work has used continent-scale areas as analytical units. More finely resolved patterns, as can be obtained from small invertebrates with limited dispersal abilities, will be obscured in those studies. A common case is treating Australia as a single biogeographical region. In the present study, the necessity of splitting Australia into multiple microareas is demonstrated using centipedes as an example. The lithobiomorph centipede Paralamyctes is distributed on fragments of Gondwana, with species in southern Africa, Madagascar, southern India, Patagonia, eastern Australia, and New Zealand. A cladogram for Paralamyctes is based on morphology and sequences for four molecular markers for 30 terminals that sample 20 of 26 known ingroup species and four outgroups. Analysis with direct optimization across a range of indel costs and transversion : transition cost ratios identifies two main clades: Paralamyctes (Paralamyctes) unites species from southern Africa, Madagascar, tropical and warm temperate Australia, and New Zealand. The other group includes the temperate Australian/New Zealand Paralamyctes (Haasiella) and Paralamyctes (Thingathinga) and a Chilean clade. Subtree analysis finds that different parts of Australia have closest affinities to other Gondwanan fragments, and some of these relationships (such as that between north Queensland and New Zealand) are based on taxonomically stable clades. Area delimitation for large continental fragments should use sufficiently fine resolution to test the ‘monophyly’ of those fragments and attempt to eliminate spurious geographical paralogy. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 89, 65–78.

Can taxon-sampling effects be minimized by using branch supports?

Rydin and Kallersjo (2002) found that taxon-sampling effects were a strongly disturbing factor in a high-level phylogenetic analysis. I have reanalyzed some of their data to assess whether bootstrap frequencies can be used to predict the stability of clades to taxon sampling, and to compare it with the performance of a stability measure based on taxon resampling (“taxon jackknifing”). High bootstrap frequencies correctly identify a small number of stable clades, but miss many other equally stable clades. When the total error rate is considered, no cut-off level based on bootstrap frequencies performs better than using all clades in the strict consensus, whereas a slight improvement was observed when cut-off levels based on taxon jackknifing frequencies are used. © The Willi Hennig Society 2006.

A century later - a total evidence re-evaluation of the phylogeny of scutigeromorph centipedes (Myriapoda:Chilopoda)

Scutigeromorpha (‘house centipedes’) play a pivotal role in myriapod systematics in being the sister group to all other chilopods, but their internal phylogeny has not been comprehensively appraised since K. W. Verhoeff’s morphological investigations a century ago. Relationships between the three families of Scutigeromorpha are inferred based on a combined analysis of approximately 5.5 Kb of sequence data from five molecular markers (complete 18S rRNA, a 2.2-Kb fragment of 28S rRNA, 16S rRNA, cytochrome c oxidase subunit I, histone H3) and 33 ingroup morphological characters. Molecular data are available for 19 ingroup terminals representing 14 morphospecies that include the genera Scutigerina, Madagassophora (family Scutigerinidae), Sphendononema (family Pselliodidae), Scutigera, Thereuopoda, Thereuopodina, Thereuonema, Allothereua and Parascutigera (family Scutigeridae). Morphology resolves the southern African–Malagasy Scutigerinidae as sister to all other Scutigeromorpha, whereas rival sister-group relationships between the Neotropical–Afrotropical Pselliodidae and Scutigerinidae + Scutigeridae or Pselliodidae + Scutigerinidae and Scutigeridae are resolved by the molecular and combined analyses. Monophyly of Scutigeridae and Thereuoneminae are stable across a broad range of analytical parameters. Thereuoneminae is composed of two stable clades: an Allothereua + Parascutigera group, and a grouping of Thereuopoda, Thereuonema and Thereuopodina. Molecular and combined analyses resolve the genus Scutigerina and the morphospecies Scutigerina weberi as paraphyletic, in both cases with a Malagasy clade excluding populations from southern Africa.

Phylogenetic relationships and historical biogeography of tribes and genera in the subfamily Nymphalinae (Lepidoptera: Nymphalidae)

We infer for the first time the phylogenetic relationships of genera and tribes in the ecologically and evolutionarily well-studied subfamily Nymphalinae using DNA sequence data from three genes: 1450 bp of cytochrome oxidase subunit I (COI) (in the mitochondrial genome), 1077 bp of elongation factor 1-alpha (EF1-α) and 400–403 bp of wingless (both in the nuclear genome). We explore the influence of each gene region on the support given to each node of the most parsimonious tree derived from a combined analysis of all three genes using Partitioned Bremer Support. We also explore the influence of assuming equal weights for all characters in the combined analysis by investigating the stability of clades to different transition/transversion weighting schemes. We find many strongly supported and stable clades in the Nymphalinae. We are also able to identify ‘rogue’ taxa whose positions are weakly supported (the different gene regions are in conflict with each other) and unstable. Our main conclusions are: (1) the tribe Coeini as currently constituted is untenable, and Smyrna, Colobura and Tigridia are part of Nymphalini; (2) ‘Kallimini’ is paraphyletic with regard to Melitaeini and should be split into three tribes: Kallimini s.s., Junoniini and Victorinini; (3) Junoniini, Victorinini, Melitaeini and the newly circumscribed Nymphalini are strongly supported monophyletic groups, and (4) Precis and Junonia are not synonymous or even sister groups. The species Junonia coenia, a model system in developmental biology, clearly belongs in the genus Junonia. A dispersal-vicariance analysis suggests that dispersal has had a major effect on the distributions of extant species, and three biotic regions are identified as being centres of diversification of three major clades: the Palaearctic for the Nymphalis-group, the Afrotropics for Junoniini and the Nearctic for Melitaeini.

Ascidian molecular phylogeny inferred from mtDNA data with emphasis on the Aplousobranchiata

We explored the usefulness of mtDNA data in assessing phylogenetic relationships within the Ascidiacea. Although ascidians are a crucial group in studies of deuterostome evolution and the origin of chordates, little molecular work has been done to ascertain the evolutionary relationships within the class, and in the studies performed to date the key group Aplousobranchiata has not been adequately represented. We present a phylogenetic analysis based on mitochondrial cytochrome c oxidase subunit I (COI) sequences of 37 ascidian species, mainly Aplousobranchiata (26 species). Our data retrieve the main groups of ascidians, although Phlebobranchiata appeared paraphyletic in some analyses. Aplousobranch ascidians consistently appeared as a derived group, suggesting that their simple branchial structure is not a plesiomorphic feature. Relationships between the main groups of ascidians were not conclusively determined, the sister group of Aplousobranchiata was the Stolidobranchiata or the Phlebobranchiata, depending on the analysis. Therefore, our data could not confirm an Enterogona clade (Aplousobranchiata + Phlebobranchiata). All of the tree topologies confirmed previous ideas, based on morphological and biochemical characters, suggesting that Cionidae and Diazonidae are members of the clade Aplousobranchiata, with Cionidae occupying a basal position within them in our analyses. Within the Aplousobranchiata, we found some stable clades that provide new data on the evolutionary relationships within this large group of ascidians, and that may prompt a re-evaluation of some morphological characters.

EVOLUTIONARY HISTORY OF THE ARCTIC GROUND SQUIRREL (SPERMOPHILUS PARRYII) IN NEARCTIC BERINGIA

Pleistocene glaciations had significant effects on the distribution and evolution of arctic species. We focus on these effects in Nearctic Beringia, a high-latitude ice-free refugium in northwest Canada and Alaska, by examining variation in mitochondrial cytochrome b (Cytb) sequences to elucidate phylogeographic relationships and identify times of evolutionary divergence in arctic ground squirrels (Spermophilus parryii). This arctic-adapted species provides an excellent model to examine the biogeographic history of the Nearctic due to its extensive subspecific variation and long evolutionary history in the region. Four geographically distinct clades are identified within this species and provide a framework for exploring patterns of biotic diversification and evolution within the region. Phylogeographic analysis and divergence estimates are consistent with a glacial vicariance hypothesis. Estimates of genetic and population divergence suggest that differentiation within Nearctic S. parryii occurred as early as the Kansan glaciation. Timing of these divergence events clusters around the onset of the Kansan, Illinoian, and Wisconsin glaciations, supporting glacial vicariance, and suggests that S. parryii survived multiple glacial periods in Nearctic Beringia. Across the Arctic, Beringia has been identified as an important regional refugium for a number of species. Within Nearctic Beringia, genetic differentiation across populations of arctic ground squirrels further reflects the effect of glacial patterns on a finer scale. The arctic ground squirrel has had a long evolutionary history in the Nearctic, with strong phylogeographic structure and stable clades persisting through multiple glacial cycles.

MOLECULAR CONSIDERATIONS IN THE TYLOPHORINAE K. SCHUM. (APOCYNACEAE-ASCLEPIADOIDEAE)

More than 30 collections of Tylophora from all over its geographic range were analysed together with representatives of all other genera in subtribe Tylophorinae except Rhyncharrhena. Regions of the chloroplast genome (trnT-L spacer, trnL intron and trnL-F spacer) as well as the nuclear genome (internal transcribed spacer including 5.8S of nuclear ribosomal DNA) were sequenced. Both the cpDNA dataset and the rDNA dataset yield a number of stable clades, but a completely resolved and stable phylogeny is not obtained from either alone or by combining them. The small East African and Arabian genera Blyttia, Diplostigma, Goydera and Pleurostelma form a well-supported clade in both datasets. Pentatropis is always recognized as monophyletic. Vincetoxicum is not clearly separable from Tylophora, and probably covers the temperate species, while Tylophora covers those in the tropics and subtropics.

Phylogenetic Study of the African Members of Cynanchum (Apocynaceae- Asclepiadoideae)

Based on morphological characters a phylogenetic analysis of 97 African and Madagascan Cynanchum species is conducted. Of these, 93 are members of sect. Cynanchum and their relationships are explored using sect. Rhodostegiella, sect. Roulinia, and Pentarrhinum as outgroups. Stable clades of two to five taxa are identified, and their relationships to the outgroups and to the remaining four African Cynanchum species are explored using Tylophora as outgroup. All analyses are performed with all characters considered as unordered and under the assumption that some characters are ordered. Monophyly of the leafless succulent taxa is tested by excluding characters directly related to succulence. The Madagascan taxa as a whole are not monophyletic. The small Madagascan succulent genus Folotsia should probably be included in Cynanchum. Three African species are excluded from sect. Cynanchum and transferred to the small African genus Pentarrhinum as P. balense, P. gonoloboides, and P. somaliense. The position of C. ledermannii, of which only incomplete material is available, cannot be resolved at present. After a long period of neglect, research in the Apocynaceae-Asclepiadoideae has intensified in recent years around the globe, mainly in the course of major flora projects (e.g., Li et al. 1995, for China; Forster 1996, for Australia; Morillo, in press, for the Venezuelan Guyanas). Parallel to these studies, analyses of important character complexes have been undertaken (e.g., Liede and Kunze 1993; Liede and Weberling 1995; Liede 1996a), and a review of tribal assignments of all genera has been presented (Liede and Albers 1994). However, phylogenetic studies have been few and mainly restricted to the subtribal and generic level (Liede 1994a, 1996b, 1996d). There are probably three main reasons for this lack of phylogenetic studies on species level. First, the subfamily contains very few mediumsized genera; genera are either large (more than 100 species, e.g., Hoya, Marsdenia, Tylophora) or very small (less than five species). In all the larger genera, there is still a vast number of species insuffiently known. Second, differences between species are rather subtle, difficult to quantify and polarize. Third, as so little is known about generic relationships, identification of suitable outgroups presents a serious problem. By examining part of the large genus Cynanchum, this paper explores the possibilities and limits of a phylogenetic study on species level in the Asclepiadoideae. In the most likely highly derived tribe Asclepiadeae (Liede 1996a, 1997b), which is characterized by hanging pollinia, Cynanchum constitutes the largest genus. It is usually defined by a corona of gynostegial origin consisting of at least partly fused staminal and interstaminal parts. Due to this rather vague generic definition, however, circumscription and size of Cynanchum vary widely between workers. In the narrow sense, Cynanchum comprises ca. 200 species living mainly in secondary growth in the semi-arid tropics. The genus comprises a wide array of growth forms; most species are medium-sized leafy twiners sprouting from a woody rootstock; however, erect herbs and succulent twiners with leaves reduced to papery scales are also found. After completing a revision of Cynanchum on the African mainland (31 species; Liede 1993a, 1994b, 1996e) and Madagascar (66 species; Liede 1993b, 1996c; Meve and Liede 1994; Liede and Meve 1996) this paper explores relationships of the species involved by phylogenetic analysis. Regarding the choice of ingroup taxa, two questions need to be addressed: 1) why not examine the whole genus?, and 2) are the species included really monophyletic? Analysis of the whole genus Cynanchum is premature because its subgeneric delimitation is still subject to debate. Liede (1996b) found conclusive morphological and chemical evidence to separate Vincetoxicum from Cynanchum, and Liede and Meve (1997), following Stevens (1988), argued to re-established Metastelma as a separate genus, distinguished from Cynanchum by its bearded corolla lobes and corona of free staminal parts. Inclusion of Ditassa in Cynanchum has been recognized as untenable even by its earlier supporters (compare Morillo 1986, 1989). Liede (1997a) sug-

Higher taxonomic level relationships among diplolepidous pleurocarpous mosses — a cladistic overview

The relationships between 66 representative pleurocarpous mosses were studied using cladistic analyses. Ten different analyses were perfoqned with different outgroups or single taxa deleted to check the stability of the analyses (all resulted in too many trees for other tests of stability to be applicable). Another three analyses were performed with different sets of characters excluded to see if some kinds of characters were more important than the others for the results of the analyses. The study suggests that the Fleischer-Brotherus system has support for large parts of the classification, although the order Isobryales (Leucodontales), in the sense of Brotherus, is a grade taxon. More recent ideas about the classification of the Isobryales, which are partly based on the differences between perfect and reduced peristomes, are not supported. Jmportant and relatively stable clades are formed by (1) the species of the Amblystegiaceae (s.l.) plus Thaidium and some members of the Hypnaceae, (2) the members of the Plagiotheciaceae (in a relatively wide sense) and (3) the Hookeriales-Sematophyllaceae-Garovagliodeae. Two of the analyses indicate that the last clade may be related to the Ptychomniaceae. The families Brachytheciaceae, Hypnaceae and Thuidiaceae, in their usual sense, appear to be polyphyletic. Characters of the sporophyte and perichaetia were in general more important for the results of the analyses than characters of the vegetative gametophyte, due to their more consistent patterns of variation among the taxa. However, in some cases, such as the definition of the Plagiotheciaceae clade, vegetative gametophytic features proved to be more important than other characters.