The systematics of Australian Daphnia (Cladocera: Daphniidae). Electrophoretic analyses of the Daphnia carinata complex

Genetic variation at eleven allozyme loci was scored in approximately 1600 individual Daphnia. The samples included representatives of all nine taxa described from the D. carinata complex in Australia. Principal coordinates and cluster analyses revealed only three groups of genotypes within the complex, corresponding to the taxa D. cephalata, D. nivalis, and a conglomerate of all other taxa described from the complex, D. carinata (sensu lato). These results are consistent with recent multivariate morphological analyses of the complex.     

Phenetic relationships inClerodendrum (Verbenaceae) and some phylogenetic considerations

Cluster analyses by different methods and a minimum spanning tree were used to study phenetic relationships in the genusChlerodendrum. 129 species were scored for 52 morphological characters corresponding to 119 character states. The phenetic results suggest a classification into 7 distinct groups, which may be grouped into two subgenera. This classification is supported by the iridoid distribution as well as by some phylogenetic considerations.     

Phylogenetic relationships within phylum Rotifera: orders and genus Notholca

We investigated evolutionary relationships among orders in phylum Rotifera and among species in genus Notholca (Rotifera) by computing parsimonious cladograms. All of the most-parsimonious cladograms generated for the ordinal level confirm the view that class Monogononta, superclass Eurotatoria, and phylum Rotifera are monophyletic. Species within the genus Notholca were separated into six groups (clades), but some species have been defined based on highly variable characters not reliably studied using cladistics. Therefore, phenetic studies are warranted, especially for species possessing caudal processes.     

Population dynamics and production of Daphnia hyalina Leydig and Daphnia cucullata Sars in Tjeukemeer

As part of a research programme on the food chains in Tjeukemeer, the Daphnia hyalina and Daphnia cucullata populations were studied for three successive years. To analyse the factors regulating the production of these two species, their population parameters (density, size distribution, fecundity) and population dynamics (birth rate, mortality rate) were studied and related to environmental factors. Since Daphnia in Tjeukemeer shows continuous recruitment, the population dynamics model INSTAR was developed and used to integrate field data with laboratory data on development rates and length-weight relationships. The dynamics of the Daphnia species are mainly regulated by temperature and fish predation, the latter affects both birth rate and mortality. Total annual Daphnia production was 3.1–6.9 g org. dry wt M^–2, and annual P/B ratio ranged from 25 to 40 for D. cucullata and from 45 to 49 for D. hyalina.     

The systematics of Australian Daphnia (Cladocera: Daphniidae). Multivariate morphometrics

Forty nine characters were measured in each of 76 male and 200 female Daphnia including specimens from all eleven taxa described from the genus in Australia, except D. jollyi. Separate multivariate analyses (cluster, principal components and discriminant) of males and females each revealed only five morphological groups in the genus corresponding to the species D. occidentalis, D. lumholtzi, D. cephalata, D. nivalis, and a conglomerate of all other taxa described from the D. carinata complex, D. carinata (sensu lato). Interpretation of the male results was straightforward, but that for females was not because of the occurrence of an environmentally induced seasonal change in morphology (cyclomorphosis) in females. Log transformations of the female data successfully isolated the effects of cyclomorphosis. The seasonal morphs formed two groups which were further differentiated into taxonomic groups.     

Multivariate and cladistic analyses of the purple-flowered species ofErysimum (Cruciferae) from the Iberian Peninsula

A taxonomically difficult purple-flowered group within the genusErysimum, restricted to the Iberian Peninsula, is analyzed by multivariate and cladistic analyses. 51 specimens have been scored for 14 characters. Both principal components and discriminant analyses provide support to the recognition of the five species considered by the author, namelyE. linifolium, E. lagascae, E. baeticum, E. popovii, andE. cazorlense. Cladistic analysis, using 7 characters resulted in a single most parsimonious cladogram containing no homoplasies. The pattern of morphologic divergence follows a clear NW.-SE. trend, which is congruent with the topology of the cladogram. This trend significantly affects growth-form as well as fruit characters, both providing the main grounds for species recognition. The different behavior and significance of several characters in both kinds of analysis is discussed. The co-occurrence of morphologically similar individuals differing in the flower color is discussed, too. Possible explanations for this phenomenon involve hybridization in a wide sense or, alternatively, rejecting the assumption of monophyly for the group.     

A comparison of phenetic and phylogenetic methods applied to the systematics of Oligochaeta

A comparative study of naidid subfamilies shows that a combination of ordination, Jaccard/Average Linkage cluster analysis and Wagner parsimony provides a useful basis for a rational phylogeny but that this does not differ markedly from the original proposed by Sperber nearly four decades ago. Hennig rules, modified by Wiley, permit a preliminary phylogeny and classification of the Annelida to be made by hand. An error in earlier versions suggested that the Dorydrilidae lacked prostate glands, and this is corrected.     

Egg predation by copepods in Daphnia brood cavities

Both field observations and enclosure experiments show that juvenile copepods enter Daphnia brood cavities to feed on Daphnia eggs and embryos. The ability to perform such in vivo exploitation is reported for both cyclopoid and calanoid copepods. Copepodites of Acanthocyclops robustus (G.O. Sars) were found to eat eggs in brood cavities of D. magna, D. pulex and D. pulicaria in experimental enclosures rich in algae. Copepodites of Eudiaptomus gracilus (G.O. Sars) were found in brood cavities of D. hyalina in a mesotrophic lake. The copepods' intrusions into brood cavities caused dramatic declines in the clutch size of infested Daphnia, and this predation effect could easily be confused with the effect of severe food limitation.     

Sexual reproduction in Daphnia: interspecific differences in a hybrid species complex

To investigate whether reproductive variation in the Daphnia galeata-cucullata-hyalina hybrid species complex can explain the occurrence of hybrids and backcrosses, a total of 43 clones from three north German lakes were tested for allocation to sexual reproduction under equal stress conditions. Six replicates per clone were followed until the seventh adult instar. I used the following cues to promote sexual reproduction: short photoperiod, water from a crowded Daphnia culture, fish-conditioned water and low food concentration. For each animal, clutch size and clutch sex were recorded. Ephippia, which were empty since the animals were cultured individually, were only produced by D. cucullata and D. cucullata x hyalina (26% and 6% of the broods, respectively), whereas almost all taxa produced males (the range was 2–15%). Intraspecific variation for male and ephippial production was also found. The fact that the taxa tested show different responses to the stimuli of-fered may indicate that there is reproductive isolation between them. This is supported by field data from the Tjeukemeer (The Netherlands) which shows that D. galeata mostly produces ephippia in spring and D. cucullata in autumn. The presence of hybrids with ephippia in both seasons, however, shows that backcrossing is also possible.     

The phylogenetic position of the Pterosauria within the Archosauromorpha

In recent years the hypothesis that pterosaurs were the major sister-group of dinosaurs and a closely-linked hypothesis that pterosaurs evolved flight from the ground up have gained general acceptance. A cladistic analysis of the Archosauromorpha using characters presented by previous workers results in a single most parsimonious tree with the Pterosauria as the major sister-group of the Dinosauria. However, that sister-group relationship is supported only by a suite of hindlimb characters that are correlated with bipedal digitigrade locomotion in dinosaurs. In pterosaurs the characters have been interpreted as correlates of bipedal cursorial locomotion, arboreal leaping, or involvement of the hindlimb in the wing. The homology of those characters in dinosaurs and pterosaurs cannot be supported. Reanalysis of the data after exclusion of those hindlimb characters results in most parsimonious trees with the Pterosauria as the sister-group of the Erythrosuchidae + Proterochampsidae + Euparkeria + Archosauria, in that order. This sister-group relationship is supported by a diverse assemblage of functionally independent skeletal characters from all regions of the skeleton. The results of the analysis cast doubt on the hypothesis that pterosaurs evolved flight from the ground up.     

Morphological differentiation within the Daphnia longispina group

Although morphological evolution is assumed to be slow within Daphnia species complexes, discontinuities in morphological space can be detected. Here, morphological data derived from females of genetically-defined clones (cf. Gießler et al., 1999) are presented, in order to estimate the genetic component of phenotypic variance under standardised laboratory conditions. Animals originated from clonal assemblages of pre-alpine lakes and ponds, and a remote lake in western Germany, covering a wide range of morphotypes known from the traditional species D. cucullata, D. galeata, D. hyalina, D. rosea, and a variety of interspecific hybrids. Phenotypic analyses were based on quantitative and qualitative morphological characters of females in the first and fifth instars. Morphological divergence between clones was analysed using discriminant analysis or multidimensional scaling and the significance of the morphological groupings was estimated using neighbour-joining trees and bootstrapping. All analyses confirmed that (a) phenotypic similarities among taxa change with instar, (b) in contrast to low genetic divergence, pronounced morphological divergence exists between animals separated on the lake/pond level favouring speciation by the habitat shift hypothesis.     

Relative effects of Daphnia and Ceriodaphnia on phosphorus-chlorophyll relationships in small urban lakes

Empirical models based on zooplankton biomass were used to predict mean summer chlorophyll a (Chl a) and to examine how zooplankton influenced the total phosphorus (TP) - Chl a relationship. Four years of data were analyzed for three lakes having similar TP concentrations but varied abundances of Daphnia and Ceriodaphnia. Mean TP did not correlate significantly with mean Chl a during the study period, although mean Daphnia density was a good predictor of Chl a concentration (p > 0.001). Both residuals from the TP - Chl a relationship (p > 0.001) and Secchi depth (p > 0.007) were negatively correlated with Daphnia abundance. Ceriodaphnia abundance was positively correlated with Chl a (p > 0.002) and Secchi depth (p > 0.001). Mean size of Daphnia during spring was the best predictor of the Daphnia-Ceriodaphnia shift in mid-summer. Early establishment of a large-sized Daphnia cohort may prevent their summer elimination by Chaoborus and intensify competition with Ceriodaphnia. These results imply an important link between Daphnia and Ceriodaphnia thereby limiting the utility of Chl a - TP model predictions in these small, urban lakes. This linkage and the differential effect of these two zooplankton species on planktonic algae deserve further consideration in similar lakes where phytoplankton and zooplankton tend to be tightly coupled.     

Daphnia (Cienodaphnia) menucoensis (Anomopoda; Daphniidae): a new species from athalassic saline waters in Argentina

Daphnia (Ctenodaphnia) menucoensis n. sp. is described from various localities in arid and semiarid Argentina. D. menucoensis has no ocellus, and a characteristic head, fornices, ephippium and denticular arrangement of postabdomen in females and males. The species belongs to a group, along with D. mediterranea, D. dolichocephala Negrea 1984, and D. salina, sharing ecological and morphological characteristics.     

Mechanisms of the filtering area adaptation in Daphnia

The changes of selected parameters of the filtering comb of the third thoracic limb were studied in a natural population of Daphnia pulicaria Forbes, as well as in experimental enclosures and in lab cultures, including individual life history. Two hypotheses were tested: 1. either these changes are related to the succession of clones coexisting within one population, or 2. the size of the filtering area changes gradually as an individual adaptation during the moulting. No evidence supporting the clonal hypothesis was found. On the contrary, the adaptability of the filtering comb is the same in a natural population as it is in a clone and in individuals.     

Phylogenetic analyses within three sections of the genus Vicia

The averaged genomic similarities based on multilocus randomly amplified polymorphic DNA (RAPD) were calculated for eight species representing three sections of the genus Vicia: faba, bithynica and narbonensis. The frequency of appearance of the sequences corresponding to 25 decamers selected at random from genomes of different Fabace species was checked, and a high correlation with the frequency observed for Vicia allowed us to assume their similar weight in typing Vicia species. The RAPD-based similarity coefficients compared with those related to whole genome hybridization with barley rDNA and those based on restriction fragment length polymorphism (RFLP) revealed similar interspecies relationships. The averaged RAPD-based similarity coefficient (Pearson’s) was 0.68 for all the species, and was sectionspecific: 0.43 (bithynica), 0.50 (faba) and 0.73 (narbonensis). The averaged similarity coefficient for V. serratifolia (0.63) placed it apart from the rest (0.75) of its section. The results correspond to the interspecies relationships built upon non-genetic data. The averaged similarity coefficient for particular RAPD was related to the presence and type of tandemly repeated motif in a primer: 0.7–0.8 for heterodimers (GC, AG, CA, GT, CT), 0.5–0.6 for homodimers (CC, GG) and 0.6 for no repeat, indicating the sensitivity of diversity range to the type of target sequences.     

Daphnia vertical distribution and the presence of toxic cyanobacteria

Daphnia can alter its vertical position in the water column in response to chemical cues from predators. In this study we tested the hypothesis that a Daphnia pulex clone with little evolutionary exposure to cyanobacteria would move away from patches of cyanobacteria (Anabaena affinis and A. flos-aquae) which contain potent endotoxins. Daphnia was censused at 2 h intervals for 6 h in laboratory columns in which there was a steep vertical gradient of cyanobacteria. Data were analyzed by repeated-measures ANOVA. Control (no Anabaena) and experimental columns showed no significant differences in Daphnia distributions. Daphnia in experimental columns frequently moved into areas with dense concentrations of Anabaena and stayed there for long periods of time. Our results show that this D. pulex clone does not exhibit a rapid (within 6 h) avoidance response to toxic Anabaena.     

Phylogenetic relationships among species of the genus Issatchenkia Kudriavzev

The phylogenetic relatedness of Issatchenkia spp. was estimated from partial rRNA sequences in two regions of the large subunit and one region of the small subunit. I. terricola was the most divergent species of the genus, differing from other members by 18% nucleotide differences in the highly variable 25S-635 region. These data indicate Issatchenkia to be the most divergent ascomycetous yeast genus presently known.     

RFLP analysis of phylogenetic relationships and genetic variation in the genus Lycopersicon

Summary Forty single-copy, nuclear probes of known chromosomal position were used to examine restriction fragment length polymorphism in the tomato genus Lycopersion. The probes were from three libraries: one cDNA, and two genomic libraries ne genomic made with EcoRI and the other with PstI. Total DNA from 156 plants representing eight species was cut with five different restriction enzymes and scored in 198 probe-enzyme combinations. Genetic distances between accessions (populations) and species were calculated from the resultant restriction patterns and proportion of shared bands. Accessions belonging to the same species largely clustered together, confirming their current classification. However, one mountain accession, classified as L. peruvianum var. humifusum (LA2150), was sufficiently distinct from the other accessions of L. peruvianum that it may qualify as a separate species L. esculentum and L. pimpinellifolium were the least clearly differentiated, possibly reflecting introgressive hybridization, known to have been promoted by man in recent history. Dendrograms constructed from cDNA versus genomic clones were nearly identical in their general grouping of species. The dendrograms revealed two major dichotomies in the genus: one corresponding to mating behavior [self-compatible (SC) versus self-incompatible (SI) species] and the other corresponding to fruit color (red versus green-fruited species). The ratio of withinversus between-accession diversity was much lower for SC species, indicating that most of the diversity within these species exists between populations, rather than within populations. Overall, the amount of genetic variation in the SI species far exceeded that found in SC species. This result is exemplified by the fact that more genetic variation could be found within a single accession of one of the SI species (e.g., L. peruvianum) than among all accessions tested of any one of the SC species (e.g., L. esculentum or L. pimpinellifolium). Results from this study are discussed in relationship to germ plasm collection/utilization and with regard to the use of RFLPs in tomato breeding and genetics.     

The taxonomic relationships within the genus Excoecaria L. (Euphorbiaceae) based on leaf morphology and rDNA sequence data

The tropical Indo-Pacific genus Excoecaria L. (Euphorbiaceae) has several closely related species in Australia whose taxonomic relationships are unclear. The most widely reported species in Australia is the mangrove species Excoecaria agallocha L. (type species), whose taxonomic and geographic limits are difficult to define from its closely related species or sub-species. Two additional taxa have also been described but not clearly differentiated from the type species: Excoecaria dallachyana Baillon and Excoecaria ovalis Endl. This project aimed to determine the taxonomic relationships of the Australian Excoecaria species using both leaf morphological data and DNA sequence data from the internal transcribed spacer (ITS) region of ribosomal genes. The nucleotide differences in the examined ITS1 region show that E. agallocha from eastern Australia and E. ovalis from Western Australia respectively, are genetically uniform within species but differ from each other consistently, thus supporting species status. The leaf morphological data also support this view: single factor analysis of variance consistently separated E. ovalis from E. agallocha on the basis of leaf width, leaf length and length of petiole. In contrast, E. ovalis from the Gulf of Carpentaria differs only slightly from E. ovalis in Western Australia, but no evidence was found to suggest any leaf morphological differentiation within this species. The analysis also suggests that E. dallachyana is not closely related to either mangrove species E. agallocha or E. ovalis, despite superficial morphological similarities.