Morphological and molecular concordance of Rhynchozoon clades (Bryozoa, Cheilostomata) from Alaska

Abstract. Alpha‐level taxonomy in the bryozoan order Cheilostomata relies almost exclusively on hard‐part morphology. Geographical, ecophenotypic, and intracolony variation often make it difficult to distinguish intra‐ from interspecific variation and to recognize taxonomically informative characters. DNA sequences provide a source of data independent of morphology by which to gauge the relative reliability of various morphological characters for taxonomy. We present a case study involving a limited number of specimens of Rhynchozoon sp. from Ketchikan, Alaska to show the utility of DNA data in identifying genetic lineages for subsequent morphological analysis. The study illustrates that the use of genetic data need not involve massive, broad‐scale phylogenetic studies to address problems in invertebrate α‐level taxonomy. Phylogeny reconstruction with a 430‐bp fragment of the 16S mitochondrial ribosomal RNA gene showed two moderately diverged clades, here termed Rhynchozoon clades A and B, separated by an average genetic distance of 2.38% (K2P+Γ). Comparison of voucher specimens by scanning electron microscopy showed two congruent, morphologically distinct forms (forms A and B, respectively) distinguishable by a polythetic suite of characters including degree of frontal costation, range of spine number, number of beads on the primary orifice, number of areolar pores, and peri‐orificial sculpturing. Orifice shape and ovicell form proved not to be good diagnostic characters. The status of the two forms as biological species is unclear, although maintenance of distinct suites of morphological characters in the two mitochondrial lineages suggests they may be reproductively isolated from one another. For Rhynchozoon form B, which tends to have a highly costate frontal wall, we suggest a resurrection of the name Rhynchozoon tumulosum, which had been previously synonymized with R. rostratum. Rhynchozoon form A may be conspecific with “Rhynchozoon sp. A” previously reported from Washington state.     

The evolution of the laterophysic connection with a revised phylogeny and taxonomy of butterflyfishes (Teleostei: Chaetodontidae)

The higher‐level relationships of butterflyfishes were examined using 37 morphological characters. This analysis combines characters derived from a histological study describing variation in the morphology of the laterophysic connection (an association between the swim bladder and the lateral‐line canals) with previously described morphological characters. The phylogenetic analysis resulted in four equally parsimonious trees that only differed in the placement of two of the 11 chaetodontid genera (Amphichaetodon and Forcipiger). We compare our analysis with previous hypotheses, present a new taxonomy consistent with the proposed cladistic relationships, and diagnose Chaetodon with five unreversed synapomorphies, including the evolution of characters composing the laterophysic connection. A new character‐based diagnosis of Chaetodon is provided and species are allocated accordingly; Chaetodon now includes the former Parachaetodon ocellatus and excludes the former subgenera Prognathodes and Roa. The evolution of the laterophysic connection is examined by optimizing character‐state transformations on the new hypothesis of relationships.     

Ultrastructural analyses support different morphological lineages in the phylum placozoa Grell, 1971

The morphology and ultrastructure of 10 clonal placozoan lineages were studied. We scored several morphological characters at a cellular and intracellular level and identified a number of morphological differences among clones. Some differences appear clone specific and allow recognizing five distinct lineages based on morphological criteria only. These data will be crucial for a yet to be established placozoan systematics. Furthermore, we here describe three new diagnostic morphological characters for Placozoa: a new structure in the upper epithelium, called “concave disc,” two distinct subpopulations of fiber cells, and especially small cells in the body margin. Besides the fiber cells appear to be arranged in several layers forming a complex, three‐dimensional net not previously described. We also describe the marginal cells as the formerly suggested potential stem‐cell type. The basic morphology is revised. J. Morphol., 2011. © 2011 Wiley‐Liss, Inc.     

Evolutionary constraints in hind wing shape in Chinese dung beetles (Coleoptera: Scarabaeinae)

This study examines the evolution hindwing shape in Chinese dung beetle species using morphometric and phylogenetic analyses. Previous studies have analyzed the evolution of wing shape within a single or very few species, or by comparing only a few wing traits. No study has analyzed wing shape evolution of a large number of species, or quantitatively compared morphological variation of wings with proposed phylogenetic relationships. This study examines the morphological variation of hindwings based on 19 landmarks, 119 morphological characters, and 81 beetle species. Only one most parsimonious tree (MPT) was found based on 119 wing and body characters. To better understand the possible role of the hindwing in the evolution of Scarabaeinae, additional phylogenetic analyses were proposed based on the only body features (106 characters, wing characters excluded). Two MPT were found based on 106 body characters, and five nodes were collapsed in a strict consensus. There was a strong correlation between the morphometric tree and all phylogenetic trees (r>0.5). Reconstructions of the ancestral wing forms suggest that Scarabaeinae hindwing morphology has not changed substantially over time, but the morphological changes that do occur are focused at the base of the wing. These results suggest that flight has been important since the origin of Scarabaeinae, and that variation in hindwing morphology has been limited by functional constraints. Comparison of metric disparity values and relative evolutionary sequences among Scarabaeinae tribes suggest that the primitive dung beetles had relatively diverse hindwing morphologies, while advanced dung beetles have relatively similar wing morphologies. The strong correlation between the morphometric tree and phylogenetic trees suggest that hindwing features reflect the evolution of whole body morphology and that wing characters are suitable for the phylogenetic analyses. By integrating morphometric and cladistic approaches, this paper sheds new light on the evolution of dung beetle hind wings.     

Evolutionary trends in Tetrastigma (Vitaceae): Morphological diversity and taxonomic implications

Tetrastigma (Miq.) Planch. (Vitaceae) is a genus with ca. 100 species showing great morphological diversity. Previous molecular phylogenetic studies suggested that traditional classification systems are not consistent with the molecular phylogeny, and Tetrastigma is undergoing further systematic investigation. We traced the evolutionary trends of 20 morphological characters within a robust phylogenetic framework. Our results revealed that many morphological characters show either multiple transitions or few state changes, however, some characters show distinct variation. The two subgenera in Tetrastigma (subgen. Tetrastigma and subgen. Palmicirrata) based on unbranched/bifurcate versus digitately branched tendrils are not supported because subgen. Tetrastigma is paraphyletic. However, the unbranched versus bifurcate/digitately branched tendril is of taxonomic utility to characterize some of the major clades. Inflorescences in Tetrastigma appear axillary, but are leaf‐opposed on a compressed axillary shoot. We found most of the species in Tetrastigma retained the ancestral compound dichasial inflorescence, except those of clade IV that have derived pseudo‐umbellate inflorescences. Other characters including habit, leaf organization, and berry shape provide additional morphological support for the major clades. Our morphological analysis and recent molecular study suggest each of the five major clades within Tetrastigma be treated as distinct taxonomic sections (five sections in the genus).     

Phylogenetic implications of the morphology of the braincase of caecilian amphibians (Gymnophiona)

Caecilian morphology is strongly modified in association with their fossorial mode of life. Currently phylogenetic analyses of characters drawn from the morphology of caecilians lack resolution, as well as complementarity, with results of phylogenetic analyses that employ molecular data. Stemming from the hypothesis derived from the mammal literature that the braincase has the greatest potential (in comparison to other cranial units) to yield phylogenetic information, the braincase and intimately associated stapes of 27 species (23 genera) of extant caecilians were examined using images assembled via microcomputed tomography. Thirty‐four new morphological characters pertaining to the braincase and stapes were identified and tested for congruence with previously recognized morphological characters. The results reveal that when added to previous character matrices, characters of the braincase and stapes resolve generic‐level relationships in a way that is largely congruent with the results of molecular analyses. Analysis of a combined data set of molecular and morphological data provides a framework for conducting ancestral character state reconstructions, which resulted in the identification of 95 new synapomorphies for various clades and taxa, 27 of which appear to be unique for the taxa that possess them. Together these data demonstrate the utility of the application of characters of the braincase and stapes for resolving phylogenetic relationships for a group whose morphology is largely confounded by functional modifications. In addition this study provides evidence of the utility of the braincase in resolving problematic morphology‐based phylogeny outside of Amniota, in an amphibian group. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 166 , 160–201.     

Character analysis in morphological phylogenetics: problems and solutions

Many aspects of morphological phylogenetics are controversial in the theoretical systematics literature and yet are often poorly explained and justified in empirical studies. In this paper, I argue that most morphological characters describe variation that is fundamentally quantitative, regardless of whether they are coded qualitatively or quantitatively by systematists. Given this view, three fundamental problems in morphological character analysis (definition, delimitation, and ordering of character states) may have a common solution: coding morphological characters as continuous quantitative traits. A new parsimony method (step-matrix gap-weighting, a modification of Thiele's approach) is proposed that allows quantitative traits to be analyzed as continuous variables. The problem of scaling or weighting quantitative characters relative to qualitative characters (and to each other) is reviewed, and three possible solutions are described. The new coding method is applied to data from hoplocercid lizards, and the results show the sensitivity of phylogenetic conclusions to different scaling methods. Although some authors reject the use of continuous, overlapping, quantitative characters in phylogenetic analysis, quantitative data from hoplocercid lizards that are coded using the new approach contain significant phylogenetic structure and exhibit levels of homoplasy similar to those seen in data that are coded qualitatively.     

Systematic implications of brain morphology in potamotrygonidae (Chondrichthyes: Myliobatiformes)

The gross brain morphology, brain proportions, and position of cranial nerves in all four genera (Potamotrygon, Plesiotrygon, Paratrygon, and Heliotrygon) and 11 of the species of the Neotropical stingray family Potamotrygonidae were studied to provide new characters that may have a bearing on internal potamotrygonid systematics. The brain was also studied in four other stingray (Myliobatiformes) genera (Hexatrygon, Taeniura, Dasyatis, and Gymnura) to provide a more inclusive phylogenetic context for the interpretation of features of the brain in potamotrygonids. Our results indicate, based on neuroanatomical characters, that the genera Paratrygon and Heliotrygon are sister groups, as are the genera Potamotrygon and Plesiotrygon, agreeing with previous morphological and molecular phylogenetic studies. Both groups of genera share distinct conditions of the olfactory tracts, telencephalon and its central nuclei, hypophysis and infundibulum, morphology and orientation of the metencephalic corpus cerebelli, orientation of the glossopharyngeal nerve, and overall encephalic proportions. The corpus cerebelli of Paratrygon and Heliotrygon is interpreted as being more similar to the general batoid condition and, given their phylogenetic position highly nested within stingrays, is considered secondarily derived, not plesiomorphically retained. Our observations of the corpus cerebelli of stingrays, including Hexatrygon, corroborate that the general stingray pattern previously advanced by Northcutt is derived among batoids. The morphology of the brain is shown to be a useful source of phylogenetically informative characters at lower hierarchical levels, such as between genera and species, and thus, has significant potential in phylogenetic studies of elasmobranchs. J. Morphol. 277:252–263, 2016. © 2015 Wiley Periodicals, Inc.     

Conflict and congruence in a combined DNA–morphology analysis of megachiropteran bat relationships (Mammalia: Chiroptera: Pteropodidae)

The phylogeny of megabats (Mammalia: Chiroptera: Megachiroptera) has been addressed only on molecular grounds, as little effort has previously been made to describe the impressive morphological variation of the group in terms of phylogenetically informative characters. Here we provide a morphological matrix of 236 characters from the integument, dentition, cranial and post‐cranial skeleton, digestive apparatus and urogenital system. This data set covers most characters discussed previously in more restricted taxonomic contexts, as well a large number of new characters. Our aim was to generate a phylogenetic hypothesis for megabats based on a combined analysis of morphological characters and available gene sequence data from four mitochondrial and one nuclear loci. We used direct optimization under conventional equal costs, as well as under a cost ratio that maximizes homology when inapplicables (gaps) are present. Our results contradict the allegedly high level of conflict between the molecular and morphological partitions. We found that, although morphology alone recovered trees different and to some extent incompatible with those from previous molecular analyses, the combination of the two sources of evidence easily accommodated the morphological and molecular signals, yielding a resolved and relatively well‐supported phylogeny of Megachiroptera that is in reasonable agreement with the current morphology‐based taxonomy of the group. Overall congruence favored the maximization of homology by a narrow margin. In addition, partial analyses showed that implied weighting of morphology performed slightly better than equal weighting with respect to the combined analyses. © The Willi Hennig Society 2005.     

Phylogenetic analysis of the African papionin basicranium using 3‐D geometric morphometrics: The need for improved methods to account for allometric effects

The basicranium has been argued to contain a strong phylogenetic signal in previous analyses of primate cranial morphology. Therefore, further study of basicranial morphology may offer new insights into controversial phylogenetic relationships within primate groups. In this study, I apply 3‐D geometric morphometric techniques in a phylogenetic analysis of the African papionin basicranium. The effects of allometry strongly influence African papionin basicranial morphology and, unless these size effects are controlled or eliminated, phylogenetic analyses suggest traditional phylogenetic groupings of small taxa (mangabeys) and large taxa (geladas, mandrills, drills, and baboons). When the effects of allometry are eliminated by excluding size‐correlated principal components (PCs) or by regression analysis with retention of residuals, phylogenetic analyses of African papionin basicranial morphology are incongruent with recent molecular and morphological studies. By contrast, a cladistic analysis of basicranial characters using the narrow allometric coding method suggests the same phylogenetic relationships as recent molecular and morphological studies. These results suggest that important phylogenetic information is contained within the size‐correlated data, and this information is being discarded during the attempt to eliminate the effects of body size. Future 3‐D morphometric studies of phylogeny should focus on the development of new methodologies to adjust for allometric effects, as current techniques appear to be ill‐equipped to deal with the case of a size‐disparate, lower‐level taxonomic group. Am J Phys Anthropol, 2010. © 2010 Wiley‐Liss, Inc.     

Review: Taxonomy of Nitella (Charales, Charophyceae) based on comparative morphology of oospores and multiple DNA marker phylogeny using cultured material

The genus Nitella is the largest group in the Charales and has the highest diversity of vegetative and oospore morphologies. In his worldwide monograph on the Charales, R. D. Wood characterized the sections and species of Nitella mainly on the basis of vegetative morphology and treated oospore wall morphology as diagnostic at the infraspecific level. Therefore, many species of Nitella exhibiting distinct external morphology of the oospore wall (EMOW) were reduced to infraspecific rank and only 53 of 204 species previously described were recognized within Nitella . However, recent morphological and molecular phylogenetic studies have demonstrated the phylogenetic validity of using EMOW for diagnosing some species of Nitella . More recently, a scanning electron microscopy (SEM) study of internal morphology of the oospore wall (IMOW) and multiple DNA marker analyses using both nuclear and chloroplast gene sequences were conducted to improve our understanding of the taxonomy of Nitella at the species level, on the basis of cultured material of a large number of species. Multiple DNA marker analyses resolved detailed and robust phylogenetic relationships within the genus and demonstrated the taxonomic and phylogenetic significance of IMOW. In addition, they supported the taxonomic decisions based on differences in oospore morphology, suggesting that an integrated approach, involving both SEM studies of the EMOW and IMOW and multiple DNA marker analyses, is appropriate to address problems at lower taxonomic levels within the genus, as well as to construct a natural taxonomic system for the genus. In this paper, recent morphological and molecular phylogenetic studies are reviewed and recent improvements in taxonomy of Nitella are summarized. Moreover, the evolution of morphological features and phylogenetic relationships within Nitella are discussed, focusing especially on oospore morphology.     

Phylogeny of the Brachytheciaceae (Bryophyta) based on morphology and sequence level data

Brachytheciaceae is often considered a taxonomically difficult group of mosses. For example, morphological variation has led to difficulty in generic delimitation. We used DNA sequence data (chloroplast psbT‐H and trnL‐F and nuclear ITS2) together with morphology (63 characters) to examine the relationships within this family. The combined unaligned length of the DNA sequences used in the phylogenetic analyses varied between 1277 and 1343 bp. For phylogeny reconstruction we performed direct optimization, as implemented in POY. Analyses were performed with three different gap costs and the morphological data partition was weighted both: (1) equal to gap cost, and (2) with a weight of one. The utility of sensitivity analysis has recently been cast into doubt; hence in this study it was performed only to explore the effects of weighting on homology statements and topologies and to enable more detailed comparisons between earlier studies utilizing the direct optimization method. The wide sequence length variation of non‐coding ITS2 sequences resulted in character optimizations (i.e., “alignments”) of very different lengths when various gap costs were applied. Despite this variation, the topologies of equally parsimonious trees remained fairly stable. The inclusion of several outgroups, instead of only one, was observed to increase the congruence between data sets and to slightly increase the resolution. An inversion event in the 9 bp loop region in the chloroplast psbT‐N spacer in mosses has been postulated to include only uninformative variation, thus possibly negatively impacting the phylogeny reconstruction. Despite this inversion, its variation within Brachytheciaceae was clearly congruent with information from other sources, but inclusion of these 9 bp in the analysis had only a minor effect on the phylogenetic results. In the most parsimonious topology, which was obtained with equal weighting of all data, Meteoriaceae and Brachytheciaceae were resolved as monophyletic sister groups, which had recently been suggested based on a few shared morphological characters. Our study revealed some new generic relationships within the Brachytheciaceae, which are discussed in light of the morphological characters traditionally used for generic delimitation.     

Walk it off: predictive power of appendicular characters toward inference of higher‐level relationships in Laniatores (Arachnida: Opiliones)

Morphological characters are essential for establishing phylogenetic relationships, delimiting higher‐level taxa, and testing phylogenetic relationships inferred from molecular sequence data. In cases where relationships between large clades remain unresolved, it becomes imperative to establish which character systems are sound predictors of phylogenetic signal. In the case of Laniatores, the largest suborder of Opiliones, some superfamilial relationships remain unresolved or unsupported, and traditionally employed phenotypic characters are typically of utility only at the family level. Here we investigated a promising set of morphological characters that can be discretized and scored in all Opiliones: cuticular structures of the distal podomeres (metatarsi and tarsi). We intensively sampled members of all known families of Laniatores, and define here three new, discrete appendicular characters toward refinement of Laniatores superfamilial systematics: metatarsal paired slits (MPS; occurring in all Laniatores except Sandokanidae), proximal tarsomeric gland (PTG; in Icaleptidae, Fissiphalliidae, and Zalmoxidae), and tarsal aggregate pores (TAP; found in Gonyleptoidea, Epedanoidea, and Pyramidopidae). We conducted statistical tests on each character to characterize the strength of phylogenetic signal and assess character independence, based on alternative tree topologies of Laniatores. All three characters had high retention indices and bore significantly strong phylogenetic signal. Excepting one pairwise comparison, morphological characters did not evolve in a correlated manner, indicating that appendicular morphology does not constitute a single character system. Our results demonstrate the predictive power and utility of appendicular characters in Opiliones phylogeny, and proffer a promising source of diagnostic synapomorphies for delimiting superfamilies.     

Craniodental characters and the relationships of Procyonidae (Mammalia: Carnivora)

Recent phylogenies of Procyonidae based on molecular data differ significantly from previous morphology‐based phylogenies in all generic sister taxon relationships. I have compiled the most comprehensive dataset of craniodental morphology that incorporates previous morphological characters, and with the aid of high‐resolution X‐ray computed tomography, new characters. This expanded craniodental analysis is based on 78 characters and yields new phylogenetic results regarding the ingroup relationships of Procyonidae. These results include Bassariscus astutus as the least derived member of Procyonidae and Ailurus fulgens nested well within the clade. Additionally, there are some similarities to previous morphological analyses of Procyonidae. Although the characters used to unite and diagnose Procyonidae vary depending on the phylogenetic analysis and have ambiguous taxonomic distribution amongst both Procyonidae and Musteloidea, there is significant morphological support for clades within Procyonidae. In addition to the strength of the morphological support within the clade, the disparate topographical regions of the skull from which the characters are derived may indicate that these synapomorphies are indeed the result of homology rather than adaptive convergence, as suggested by analyses based on molecular data. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 669–713.     

Butterfly morphology in a molecular age – Does it still matter in butterfly systematics?

We review morphological characters considered important for understanding butterfly phylogeny and evolution in the light of recent large-scale molecular phylogenies of the group. A number of the most important morphological works from the past half century are reviewed and morphological character evolution is reassessed based on the most recent phylogenetic results. In particular, higher level butterfly morphology is evaluated based on a very recent study combining an elaborate morphological dataset with a similar molecular one. Special attention is also given to the families Papilionidae, Nymphalidae and Hesperiidae which have all seen morphological and molecular efforts come together in large, combined works in recent years. In all of the examined cases the synergistic effect of combining elaborate morphological datasets with ditto molecular clearly outweigh the merits of either data type analysed on its own (even for ‘genome size’ molecular datasets). It is evident that morphology, far from being obsolete or arcane, still has an immensely important role to play in butterfly (and insect) phylogenetics. Not least because understanding morphology is essential for understanding and evaluating the evolutionary scenarios phylogenetic trees are supposed to illustrate.     

Taxonomic classification of the reef coral family Mussidae (Cnidaria: Anthozoa: Scleractinia)

Molecular analyses are transforming our understanding of the evolution of scleractinian corals and conflict with traditional classification, which is based on skeletal morphology. A new classification system, which integrates molecular and morphological data, is essential for documenting patterns of biodiversity and establishing priorities for marine conservation, as well as providing the morphological characters needed for linking present‐day corals with fossil species. The present monograph is the first in a series whose goal is to develop such an integrated system. It addresses the taxonomic relationships of 55 Recent zooxanthellate genera (one new) in seven families (one new), which were previously assigned to the suborder Faviina (eight genera are transferred to incertae sedis). The present monograph has two objectives. First, we introduce the higher‐level classification system for the 46 genera whose relationships are clear. Second, we formally revise the taxonomy of those corals belonging to the newly discovered family‐level clade (restricted today to the western Atlantic and Caribbean regions); this revised family Mussidae consists of ten genera (one of which is new) and 26 species that were previously assigned to the ‘traditional’ families Faviidae and Mussidae. To guide in discovering morphologic characters diagnostic of higher‐level taxa, we mapped a total of 38 morphologic characters [19 macromorphology, eight micromorphology, 11 microstructure] onto a molecular tree consisting of 67 species [22 Indo‐Pacific and seven Atlantic species in the traditional family Faviidae; 13 Indo‐Pacific and ten Atlantic species in the traditional family Mussidae; 13 species in the traditional families Merulinidae (5), Pectiniidae (7), and Trachyphylliidae (1); two Atlantic species of traditional Montastraea], and trace character histories using parsimony. To evaluate the overall effectiveness of morphological data in phylogeny reconstruction, we performed morphology‐based phylogenetic analyses using 27 (80 states) of the 38 characters, and compared morphological trees with molecular trees. The results of the ancestral state reconstructions revealed extensive homoplasy in almost all morphological characters. Family‐ and subfamily‐level molecular clades [previously identified as XVII?XXI] are best distinguished on the basis of the shapes of septal teeth and corresponding microstructure. The newly revised family Mussidae (XXI) has septal teeth with regular pointed tips (a symplesiomorphy) and a stout blocky appearance. It has two subfamilies, Mussinae and Faviinae. The subfamily Mussinae is distinguished by spine‐shaped teeth and widely spaced costoseptal clusters of calcification centres. The subfamily Faviinae is distinguished by blocky, pointed tricorne or paddle‐shaped teeth with elliptical bases, transverse structures such as carinae that cross the septal plane, and well‐developed aligned granules. Defining diagnostic characters for the broader data set is more challenging. In analyses of taxonomic subsets of the data set that were defined by clade, morphological phylogenetic analyses clearly distinguished the families Mussidae (XXI) and Lobophylliidae (XIX), as well as the two subfamilies of Mussidae (Mussinae, Faviinae), with one exception (Homophyllia australis). However, analyses of the entire 67‐species data set distinguished the family Lobophylliidae (XIX), but not the Merulinidae (XVII) and not the newly defined Mussidae (XXI), although the subfamily Mussinae was recovered as monophyletic. Some lower‐level relationships within the Merulinidae (XVII) agree with molecular results, but this particular family is especially problematic and requires additional molecular and morphological study. Future work including fossils will not only allow estimation of divergence times but also facilitate examination of the relationship between these divergences and changes in the environment and biogeography. Published 2012. This article is a U.S. Government work and is in the public domain in the USA. Zoological Journal of the Linnean Society, 2012, 166 , 465–529.     

Which Morphological Characteristics Are Most Influenced by the Host Matrix in Downy Mildews? A Case Study in Pseudoperonospora cubensis

Before the advent of molecular phylogenetics, species concepts in the downy mildews, an economically important group of obligate biotrophic oomycete pathogens, have mostly been based upon host range and morphology. While molecular phylogenetic studies have confirmed a narrow host range for many downy mildew species, others, like Pseudoperonospora cubensis affect even different genera. Although often morphological differences were found for new, phylogenetically distinct species, uncertainty prevails regarding their host ranges, especially regarding related plants that have been reported as downy mildew hosts, but were not included in the phylogenetic studies. In these cases, the basis for deciding if the divergence in some morphological characters can be deemed sufficient for designation as separate species is uncertain, as observed morphological divergence could be due to different host matrices colonised. The broad host range of P. cubensis (ca. 60 host species) renders this pathogen an ideal model organism for the investigation of morphological variations in relation to the host matrix and to evaluate which characteristics are best indicators for conspecificity or distinctiveness. On the basis of twelve morphological characterisitcs and a set of twelve cucurbits from five different Cucurbitaceae tribes, including the two species, Cyclanthera pedata and Thladiantha dubia, hitherto not reported as hosts of P. cubensis, a significant influence of the host matrix on pathogen morphology was found. Given the high intraspecific variation of some characteristics, also their plasticity has to be taken into account. The implications for morphological species determination and the confidence limits of morphological characteristics are discussed. For species delimitations in Pseudoperonospora it is shown that the ratio of the height of the first ramification to the sporangiophore length, ratio of the longer to the shorter ultimate branchlet, and especially the length and width of sporangia, as well as, with some reservations, their ratio, are the most suitable characteristics for species delimitation.     

Comparative histology of the vaginal–cloacal region in Squamata and its phylogenetic implications

We described the histology and morphology of the vaginal–cloacal region in 18 species from 12 Squamata families. This comparative study revealed a wide variation in the cloacal morphology. Fifteen morphological characters were considered to be primary homology hypotheses and were optimized over the topology derived from the parsimony analysis of the available soft morphological evidence, including the characters described in this study. The synapomorphies optimized for Squamata are bifid urodaeum, common urodaeal cavity with similar histological features of the urodaeal horns, and presence of glands in the anterior urodaeum; for Scleroglossa the synapomorphy is the lateral position of the vaginal intrusion into the anterior urodaeal chamber, for Nyctisaura + Scincomorpha the synapomorphy is the presence of a bifid posterior urodaeum; and for Xantusidae + Annulata it is the presence of simple glands in the anterior urodaeum. The central position of the vaginal intrusion into the urodaeal chamber and the intraepithelial position of the glandular unit in the anterior urodaeum behave as autapomorphies for Iguanidae. This study contributes evidence that defines the relationships within Scleroglossa. Cloacal features provide interesting information that is useful as a source of morphological characters for phylogenetic studies in Squamata.     

A comparison of the external morphology of the membranous inner ear in elasmobranchs

Studies on the elasmobranch inner ear have focused predominantly on a small group of sharks, particularly, carcharhinids. As a result, subsequent studies in other species have subdivided species into two main groups: those typical and those atypical of carcharhinid sharks. This study proposes a different set of inner‐ear morphology groupings to those previously suggested. The inner ears from 17 species of elasmobranchs (representing both sharks and rays) are examined in this study and based on morphometric data some groups include both rays and sharks. Four groups are now proposed based predominantly on the shape and dimensions of the membranous otoconial organs, and characteristics of the semicircular canals. Evident morphological differences between the ear types belonging to the new groups include the membranes of the semicircular canals being bound to the otoconial organs in some species, while only being connected via the canal ducts in others, as well as clear variation present in saccular organ size. Previous studies examining variation in the inner ear have attributed differences to either phylogeny or functional significance. Results from this study suggest that neither phylogeny nor feeding strategy solely accounts for the morphological diversity present in the external morphology of the elasmobranch inner ear. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Linking stream ecology with morphological variability in a native freshwater fish from semi‐arid Australia

Environmental variation is a potent force affecting phenotypic expression. While freshwater fishes have provided a compelling example of the link between the environment and phenotypic diversity, few studies have been conducted with arid‐zone fishes, particularly those that occur in geographically isolated regions where species typically inhabit intermittent and ephemeral creeks. We investigated morphological variation of a freshwater fish (the western rainbowfish, Melanotaenia australis) inhabiting creeks in the Pilbara region of northwest Australia to determine whether body shape variation correlated with local environmental characteristics, including water velocity, habitat complexity, predator presence, and food availability. We expected that the geographic isolation of creeks within this arid region would result in habitat‐specific morphological specializations. We used landmark‐based geometric morphometrics to quantify the level of morphological variability in fish captured from 14 locations within three distinct subcatchments of a major river system. Western rainbowfish exhibited a range of morphologies, with variation in body depth accounting for a significant proportion (>42%) of the total variance in shape. Sexual dimorphism was also apparent, with males displaying deeper bodies than females. While the measured local habitat characteristics explained little of the observed morphological variation, fish displayed significant morphological differentiation at the level of the subcatchment. Local adaptation may partly explain the geographic patterns of body shape variation, but fine‐scale genetic studies are required to disentangle the effects of genetic differentiation from environmentally determined phenotypic plasticity in body shape. Developing a better understanding of environment–phenotype relationships in species from arid regions will provide important insights into ecological and evolutionary processes in these unique and understudied habitats.