Carapace dentition patterns, morphometrics and allozyme differentiation amongst two toothed freshwater crab species (Potamonautes warreni and P-unispinus) (Decapoda : Brachyura : Potamonautidae) from river systems in South Africa

The taxonomic relationship between two toothed South African river crabs, Potamonautes warreni and P. unispinus, is unclear. The problem stems from the widespread variation in carapace dentition patterns amongst P. warreni individuals over its biogeographic range, where single toothed individuals may appear similar in carapace morphology to P. unispinus. Ten populations of P. warreni and 18 populations of P. unispinus were collected and the morphometric and genetic differentiation between the two taxa quantified. Patterns of morphometric and genetic variation were examined using multivariate statistics and protein gel electrophoresis, respectively. Principal component analyses of carapace characters showed that the two species are morphologically indistinguishable. However, discriminate functions analyses and additional statistical results corroborate the morphological distinction between the two taxa. Allozyme electrophoresis of 17 protein coding loci, indicated a close genetic similarity between the two species (I = 0.92). A fixed allelic difference at one locus (LT-2) and extensive genetic variability at another locus (PGM-1) indicate that two gene pools are present and that the two taxa are genetically isolated. Intraspecific genetic I values for both species were > 0.97 and indicated no apparent genetic structuring on a micro or macro-geographic scale. The variation in carapace dentition among P. warreni populations possesses no genetic basis and may possibly toe the product of ecogenesis. The value of dentition patterns in the systematics of river crabs is discussed. Dentition patterns among river crab species appear to be conserved and reliable as species specific diagnostic markers, but should ideally be used in combination with other morphological data sets and genetic evidence.

Ecology, shell morphology, anatomy and sperm ultrastructure of the caenogastropod Pyrgula annulata, with a discussion of the relationship between the 'Pyrgulidae' and Caspian and Baikalian rissooideans

The composition of the Pyrgulidae and its relationships to other member families of the caenogastropod superfamily Rissooidea are examined after a consideration of new anatomical (including gross anatomy, sperm ultrastructure), conchological (including protoconch features), ecological, biogeographical and palaeontological data and a re-evaluation of existing literature. Pyrgulidae can be distinguished from hydrobiids unequivocally only with the aid of the radula. Sperm ultrastructural features suggest a very close relationship between the Pyrgulidae, the Hydrobiidae and the Bithyniidae (in fact no family-diagnostic sperm characters can be found to separate these three taxa). Based upon neontological and fossil evidence it is likely that pyrgulids represent a Miocene offshoot from a paratethyal hydrobiid lineage. Pyrgulids may also represent the stock from which the baicaliids arose, in which case the Pyrgulidae must be considered a paraphyletic group. The huge biogeographic gap between the Caspian Sea and Lake Baikal is to some extent bridged by the finding of a Neogene pyrgulid from the Altai Mountains. An alternative scenario for the origin of baicaliids is presented.

Habitat use, diet and body size of Heard Island weevils

Habitat use, diet and body-size variation are examined in weevils from Heard Island. with specific attention being given to the Ectemnorhinus viridis species complex. E. viridis shows marked altitudinal variation in body size and vestiture, but there are no consistent associations between body size and diet. nor are there consistent among-individual differences in conventional taxonomic characters. Thus, the status of E. viridis as a single, variable species is maintained. This species occurs from sea level to 600 rn and it feeds on vascular plants and bryophytes. Canonopsis sericeus also feeds on bryophytes and vascular plants and occurs over a narrower altitudinal range. Palirhoeus eatoni is restricted to the surpralittoral zone where it feeds on marine algae and lichens. Bothrometopus brei,is and B. gracilipes both feed on cryptogams, with the former species occurring from sea level to 450 m. and the latter from 50 to 550 m above sea level. In all species, males are smaller than females and there is a size cline such that populations from higher elevations are smaller than those at lower altitudes. This cline is the reverse of that found on the Prince Edward Islands which, unlike Heard Island, lie to the north of the Antarctic Polar Frontal Zone. This difference in body-size clines between weevils on the two island groups is ascribed to the shorter growing season on the colder Heard Island. The information presented here supports previous ideas regarding the evolution of the Ectemnorhinus-group of weevils on the South Indian Ocean Province Islands, although it suggests that subsequent tests of these hypotheses would profit from the inclusion of molecular systematic work.

Phylogenetic revision of Agapophytinae subf.n. (Diptera : Therevidae) based on molecular and morphological evidence

Agapophytinae subf.n. is a highly diverse lineage of Australasian Therevidae, comprising eight described and two new genera: Agapophytus Guerin-Meneville, Acupalpa Krober, Acraspisa Krober, Belonalys Krober, Bonjeania Irwin & Lyneborg, Parapsilocephala Krober, Acatopygia Krober, Laxotela Winterton & Irwin, Pipinnipons gen.n. and Patanothrix gen.n. A genus-level cladistic analysis of the subfamily was undertaken using sixty-eight adult morphological characters and c. 1000 base pairs of the elongation factor-1 alpha (EF-1 alpha) protein coding gene. The morphological data partition produced three most parsimonious cladograms, whereas the molecular data partition gave a single most parsimonious cladogram, which did not match any of the cladograms found in the morphological analysis. The level of congruence between the data partitions was determined using the partition homogeneity test (HTF) and Wilcoxon signed ranks rest. Despite being significantly incongruent in at least one of the incongruence tests, the partitions were combined in a simultaneous analysis. The combined data yielded a single cladogram that was better supported than that of the individual partitions analysed separately. The relative contributions of the data partitions to support for individual nodes on the combined cladogram were investigated using Partitioned Bremer Support. The level of support for many nodes on the combined cladogram was non-additive and often greater than the sum of support for the respective nodes on individual partitions. This synergistic interaction between incongruent data partitions indicates a common phylogenetic signal in both partitions. It also suggests that criteria for partition combination based solely on incongruence may be misleading. The phylogenetic relationships of the genera are discussed using the combined data. A key to genera of Agapophytinae is presented, with genera diagnosed and figured. Two new genera are described: Patanothrix with a new species (Pat. skevingtoni) and Pat. wilsoni (Mann) transferred from Parapsilocephala, and Pipinnipons with a new species (Pip. kroeberi). Pipinnipons fascipennis (Krober) is transferred from Squamopygin Krober and Pip. imitans (Mann) is transferred from Agapophytus. Agapophytus bicolor (Krober) is transferred from Parapsilocephala. Agapophytus varipennis Mann is synonymised with Aga, queenslandi Krober and Aga. flavicornis Mann is synonymised with Aga. pallidicornis (Krober).

Phylogenetic revision of Agapophytus Guerin (Diptera : Therevidae : Agapophytinae)

Morphologically diverse and species-rich, the endemic Australasian genus Agapophytus is revised. Eleven previously described species are redescribed and twenty-nine species are described for the first time: A. adonis, sp. nov., A. annamariae, sp. nov., A. antheliogynaion, sp. nov., A. asprolepidotos, sp. nov., A. atrilaticlavius, sp. nov., A. biluteus, sp. nov., A. borealis, sp. nov., A. caliginosus, sp. nov., A. cerrusus, sp. nov., A. chaetohypopion, sp. nov., A. chrysosisyrus, sp. nov., A. decorus, sp. nov., A. dieides, sp. nov., A. discolor, sp. nov., A. eli, sp. nov., A. fenestratum, sp. nov., A. galbicaudus, sp. nov., A. labifenestellus, sp. nov., A. laparoceles, sp. nov., A. lissohoplon, sp. nov., A. lyneborgi, sp. nov., A. notozophos, sp. nov., A. novaeguineae, sp. nov., A. pallidicrus, sp. nov., A. palmulus, sp. nov., A. paramonovi, sp. nov., A. septentrionalis, sp. nov., A. yeatesi, sp. nov. and A. zebra, sp. nov. All 40 species of Agapophytus were compared in a cladistic analysis with three species of Acupalpa Krober using 134 states across 58 adult morphological characters. The analysis resulted in 36 most parsimonious trees with a length of 240 steps. The phylogenetic relationships of the species of Agapophytus are discussed with three main clades recognised: A. dioctriaeformis clade, A. australasiae clade and A. queenslandi clade.

The marginal dentition of the Australian lungfish, Neoceratodus forsteri (Osteichthyes : Dipnoi)

The dentary, a component of the transient marginal dentition found in the mandible of juveniles of the living Australian lungfish Neoceratodus forsteri, is a tooth plate exactly comparable to the tooth plates with radiating ridges that make up the marginal dentitions of Devonian dipnoans like Andreyevichthys, Orlovichthys and Ichnomylax. In N. forsteri, the dentary consists of two ridges, set almost in line with each other, and growing by the addition of cusps, of increasing sizes, to the extremity of each ridge. It is therefore equivalent to two ridges of a more normal tooth plate with radiating ridges. Despite its appearance, as a long row of sharp cusps ankylosed to a slender bone, and its position, embedded in soft tissue above the anterolabial margin of Meckel's cartilage, it is a tooth plate and is not comparable to the marginal dentitions of other vertebrates. Structure and development of the transient marginal dentition of this lungfish is another indication that dipnoans may not be the sister group of tetrapods.

Interaction between natural and sexual selection during the evolution of mate recognition

The interaction between natural and sexual selection is central to many theories of how mate choice and reproductive isolation evolve, but their joint effect on the evolution of mate recognition has not, to my knowledge, been investigated in an evolutionary experiment. Natural and sexual selection were manipulated in interspecific hybrid populations of Drosophila to determine their effects on the evolution of a mate recognition system comprised of cuticular hydrocarbons (CHCs). The effect of natural selection in isolation indicated that CHCs were costly for males and females to produce. The effect of sexual selection in isolation indicated that females preferred males with a particular CHC composition. However, the interaction between natural and sexual selection had a greater effect on the evolution of the mate recognition system than either process in isolation. When natural and sexual selection were permitted to operate in combination, male CHCs became exaggerated to a greater extent than in the presence of sexual selection alone, and female CHCs evolved against the direction of natural selection. This experiment demonstrated that the interaction between natural and sexual selection is critical in determining the direction and magnitude of the evolutionary response of the mate recognition system.

Microevolution in island forms: the roles of drift and directional selection in morphological divergence of a passerine bird

Theory predicts that in small isolated populations random genetic drift can lead to phenotypic divergence; however this prediction has rarely been tested quantitatively in natural populations. Here we utilize natural repeated island colonization events by members of the avian species complex, Zosterops lateralis, to assess whether or not genetic drift alone is an adequate explanation for the observed patterns of microevolutionary divergence in morphology. Morphological and molecular genetic characteristics of island and mainland populations are compared to test three predictions of drift theory: (1) that the pattern of morphological change is idiosyncratic to each island; (2) that there is concordance between morphological and neutral genetic shifts across island populations; and (3) for populations whose time of colonization is known, that the rate of morphological change is sufficiently slow to be accounted for solely by genetic drift. Our results are not consistent with these predictions. First, the direction of size shifts was consistently towards larger size, suggesting the action of a nonrandom process. Second, patterns of morphological divergence among recently colonized populations showed little concordance with divergence in neutral genetic characters. Third, rate tests of morphological change showed that effective population sizes were not small enough for random processes alone to account for the magnitude of microevolutionary change. Altogether, these three lines of evidence suggest that drift alone is not an adequate explanation of morphological differentiation in recently colonized island Zosterops and therefore we suggest that the observed microevolutionary changes are largely a result of directional natural selection.

Spermatozoal morphology of the freshwater anomuran Aegla longirostri Bond-Buckup & Buckup, 1994 (Crustacea : Decapoda : Aeglidae) from South America

Unique sperm morphology is described for Aegla longirostri Bond-Buckup & Buckup, 1994. a representative of the freshwater anomuran family Aeglidae from South America. Comparisons of the spermatozoal ultrastructure of this species with that described for other anomurans indicate that A. longirostri has a distinct suite of spermatozoal characters. Within the Anomura, the aeglids share more spermatozoal characters with the superfamily Lomoidea. represented by the monotypic Australian endemic genus, Lomis, than to any previously described representative from the Galatheoidea, Hippoidea. or Paguroidea. A more basal ancestry, with an independent evolutionary lineage. within the Anomura is Postulated for the Aeglidae. A Superficial resemblance of the spermatozoal ultrastructure of A. longirostri to that described for a palinurid lobster, Jasus, and a thalassinidean mud shrimp, Neaxius, is also noted.

Phylogenetic revision of Australian members of the Allomethus genus group (Diptera : Pipunculidae)

The Australian species of Allomethus and Claraeola are revised and include one described species, Claraeola erinys (Perkins), and five new species: Allomethus unicicolis sp. n., Claraeola cyclohirta sp. n., C. sicilis sp. n., C. spargosis sp. n., and C. yingka sp. n.. Claraeola hylaea (Perkins) is proposed to be a synonym of C. erinys (Perkins). A key to species is provided and male and female genitalia are illustrated. The Australian species are placed phylogenetically into a world context using available taxa within the Allomethus genus group. The phylogenetic relationships are discussed in light of a cladistic analysis involving 22 taxa and 60 characters.

A molecular phylogeny of rainbow skinks (Scincidae : Carlia): taxonomic and biogeographic implications

The phylogenetic relationships amongst 29 species of Carlia and Lygisaurus were estimated using a 726-base-pair segment of the protein-coding mitochondrial ND4 gene. Results do not support the recent resurrection of the genus Lygisaurus. Although most Lygisaurus species formed a single clade, this clade is nested within Carlia and includes Carlia parrhasius. Due to this new molecular evidence, and the paucity of diagnostic morphological characters separating the genera, Lygisaurus de Vis 1884 is re-synonymised with Carlia Gray 1845. Our analysis is also inconsistent with a previous suggestion that Lygisaurus timlowi should be removed to Menetia, a genus that is distantly related relative to outgroups used here. Intraspecific variation in Carlia is, in several instances, greater than interspecific distance. The most strikingly divergent lineages are found within C. rubrigularis, which appears to be paraphyletic, with southern populations more closely related to C. rhomboidalis than to northern populations of C. rubrigularis. The two C. rubrigularis-C. rhomboidalis lineages form part of a major polytomy at an intermediate level of divergence. Lack of resolution at this level, however, does not appear to be due to saturation or loss of phylogenetic signal. Rather, the polytomy probably reflects a period of relatively rapid diversification that occurred sometime during the Miocene.

Partitioned Bremer support and multiple trees

Partitioned Bremer support (PBS) is a valuable means of assessing congruence in combined data sets, but some aspects require clarification. When more than one equally parsimonious tree is found during the constrained search for trees lacking the node of interest, averaging PBS for each data set across these trees can conceal conflict, and PBS should ideally be examined for each constrained tree. Similarly, when multiple most parsimonious trees (MPTs) are generated during analysis of the combined data, PBS is usually calculated on the consensus tree. However, extra information can be obtained if PBS is calculated on each of the MPTs or even suboptimal trees. (C) 2002 The Willi Hennig Society. Published by Elsevier Science (USA). All rights reserved.

Spatial structure and habitat variation in a grasshopper hybrid zone

A hybrid zone between the grasshoppers Chorthippus brunneus and C. jacobsi (Orthoptera: Acrididae) in northern Spain has been analyzed for variation in morphology and ecology. These species are readily distinguished by the number of stridulatory pegs on the hind femur. Both sexes are fully winged and inhabit disturbed habitats throughout the study area. We develop a maximum-likelihood approach to fitting a two-dimensional cline to geographical variation in quantitative traits and for estimating associations of population mean with local habitat. This method reveals a cline in peg number approximately 30 km south of the Picos de Europa Mountains that shows substantial deviations in population mean compared with the expectations of simple tension zone models. The inclusion of variation in local vegetation in the model explains a significant proportion of the residual variation in peg number, indicating that habitat-genotype associations contribute to the observed spatial pattern. However, this association is weak, and a number of populations continue to show strong deviations in mean even after habitat is included in the final model. These outliers may be the result of long-distance colonization of sites distant from the cline center or may be due to a patchy pattern of initial contact during postglacial expansion. As well as contrasting with the smooth hybrid zones described for Chorthippus parallelus, this situation also contrasts with the mosaic hybrid zones observed in Gryllus crickets and in parts of the hybrid zone between Bombina toad species, where habitat-genotype associations account for substantial amounts of among-site variation.

Molecular evidence for the common origin of snap-traps among carnivorous plants

The snap-trap leaves of the aquatic waterwheel plant (Aldrovanda) resemble those of Venus' flytrap (Dionaea), its distribution and habit are reminiscent of bladderworts (Utricularia), but it shares many reproductive characters with sundews (Drosera). Moreover, Aldrovanda has never been included in molecular phylogenetic studies, so it has been unclear whether snap-traps evolved only once or more than once among angiosperms. Using sequences from nuclear 18S and plastid rbcL, atpB, and matK genes, we show that Aldrovanda is sister to Dionaea, and this pair is sister to Drosera. Our results indicate that snap-traps are derived from flypaper-traps and have a common ancestry among flowering plants, despite the fact that this mechanism is used by both a terrestrial species and an aquatic one. Genetic and fossil evidence for the close relationship between these unique and threatened organisms indicate that carnivory evolved from a common ancestor within this caryophyllid clade at least 65 million years ago.

Testing the relationship between morphological and molecular rates of change along phylogenies

Molecular evolution has been considered to be essentially a stochastic process, little influenced by the pace of phenotypic change. This assumption was challenged by a study that demonstrated an association between rates of morphological and molecular change estimated for total-evidence phylogenies, a finding that led some researchers to challenge molecular date estimates of major evolutionary radiations. Here we show that Omland's (1997) result is probably due to methodological bias, particularly phylogenetic nonindependence, rather than being indicative of an underlying evolutionary phenomenon. We apply three new methods specifically designed to overcome phylogenetic bias to 13 published phylogenetic datasets for vertebrate taxa, each of which includes both morphological characters and DNA sequence data. We find no evidence of an association between rates of molecular and morphological rates of change.