INTENSE SELECTION OF MITE CLONES IN A HETEROGENEOUS ENVIRONMENT

Genetic diversity within obligatorily parthenogenic species can be high, contrary to common views of the evolutionary consequences of this reproductive system. How this clonal diversity is maintained within populations is not clearly understood. Previous studies showing high clonal diversity have used parthenogenic organisms with known sexual forms or relatives. Here we report significant spatial and temporal clonal diversity within two populations of an obligatorily parthenogenic mite, Penthaleus major, which has no known sexual form or close sexual relative. Fitness estimates from temporal sampling at two sites and manipulated field plots reveal intense natural selection acting on ecologically different clones. We propose that environmental heterogeneity contributes to the maintenance of clonal diversity within populations of P. major and that selection is strong enough to overcome the problems of relative niche size.     

Reproduction and sexual development in a freshwater gastrotrich

Summary Post-embryonic development of parthenogenic eggs of Lepidodermella squammata was studied by light and electron microscopy in animals of known age and reproductive history. Each bilateral gonad initially contains eight cells. No mitotic proliferation occurs during parthenogenic egg development. Germ cells are tightly clustered, have smooth plasma membranes with no interconnections, and are uninucleate. There is no surrounding ovary or oviduct. At hatching, two cells in each gonad are identifiable as parthenogenic eggs. The enlarged nucleolus of the most mature egg has already attained the morphology that persists throughout vitellogenesis, with intertwined granular and fibrillar threads. Less mature eggs have earlier stages of nucleolar development, and lack indications of meiotic events. Parthenogenic eggs enter vitellogenesis singly, with formation of RER and active Golgi complexes, and the accumulation of lipid, yolk, and various granules. The shell is formed in situ, whereas the spines elongate after egg deposition. Most animals produce four parthenogenic eggs, which undergo immediate development (tachyblastic eggs). Resting (opsiblastic) eggs are rare in isolation culture. Both types of eggs are produced only prior to the formation of sperm and primary oocytes. The absence of synaptonemal complexes, which would indicate synapsis of homologous chromosomes in prophase of meiosis I, implies that parthenogenesis is by apomixis in L. squammata.     

An electron microscope study on in vitro parthenogenesis in sunflower

Summary Electron microscope studies have been conducted on the parthenogenesis induced by in vitro culture of unfertilized ovules of sunflower (Helianthus annuus). In comparison with the state of the egg prior to inoculation, some eggs 5 days after culture show striking ultrastructural changes, which include, among others, nuclear migration, an increase in the number and activity of the organelles, a loss of polarity and wall formation at the chalazal end of the cell. Most of these changes are similar to those that occur normally in the zygote, indicating that parthenogenic development has been triggered in these eggs. Such eggs have been termed activated and are presumed to be capable of undergoing parthenogenesis. The parthenogenic proembryos which result share some features in common with zygotic proembryos. In addition, some parthenogenic proembryos exhibit unique properties not found in zygotic proembryos. These include embryos that consist of two parts differing markedly in density, an inversion of polarity, the frequent occurrence of autophagic vacuoles, the thickening of cell walls, a centripetal growth mode of wall formation, the appearance of an incomplete cell wall, free nuclear division, amitosis and degeneration. We believe that these ultrastructural peculiarities are the effects of in vitro culture.     

Morphological diversity of the <Emphasis Type="BoldItalic">Cynoscion</Emphasis> group (Perciformes: Sciaenidae) in the Gulf of Guayaquil region,Ecuador: A comparative approach

Synopsis We assess morphological diversity of species of the Cynoscion group in the Gulf of Guayaquil (GOG) using traditional morphometric methods. Five species from the GOG assemblage (C. albus, C. analis, C. phoxocephalus, C. squamipinnis, and Isopisthus remifer) are compared to four species from a relatively well-studied assemblage in the western Atlantic (C. arenarius, C. nebulosus, C. nothus, and C. regalis). The two regional species assemblages broadly overlap in morphology, but sympatric species segregate relatively well within each assemblage. The GOG species segregate primarily along the major axis of shape variation in the study, which is associated with variation in the anal, second dorsal, and caudal fins. The western Atlantic species segregate primarily along the second major axis of shape variation, which is most strongly associated with variation in gill raker length, and less strongly with pectoral fin length, eye diameter, and length of the third dorsal spine. Patterns of morphological divergence among the western Atlantic species support the hypothesis that morphological divergence is associated with ecological divergence. Comparisons across assemblages indicate that morphological divergence among species in the GOG is substantial. Consequently, Cynoscion species in the GOG may be highly divergent in ecological habits, which would have important management implications, but further ecological research is needed. This study provides a first glimpse into the major patterns of morphological diversification in the Cynoscion group.¹Bryant D., E. Rodenburg, T. Cox & D. Nielsen. 1995. Coastlines at Risk: an Index of Potential Development-Related Threats to Coastal Ecosystems. WRI Indicator Brief, World Resources Institute, Washington, D.C.     

Morphological,ecological and genetic aspects associated with endemism in the Fly Orchid group

The European genus Ophrys (Orchidaceae) is famous for its insect‐like floral morphology, an adaptation for a pseudocopulatory pollination strategy involving Hymenoptera males. A large number of endemic Ophrys species have recently been described, especially within the Mediterranean Basin, which is one of the major species diversity hotspots. Subtle morphological variation and specific pollinator dependence are the two main perceptible criteria for describing numerous endemic taxa. However, the degree to which endemics differ genetically remains a challenging question. Additionally, knowledge regarding the factors underlying the emergence of such endemic entities is limited. To achieve new insights regarding speciation processes in Ophrys, we have investigated species boundaries in the Fly Orchid group (Ophrys insectifera sensu lato) by examining morphological, ecological and genetic evidence. Classically, authors have recognized one widespread taxon (O. insectifera) and two endemics (O. aymoninii from France and O. subinsectifera from Spain). Our research has identified clear morphological and ecological factors segregating among these taxa; however, genetic differences were more ambiguous. Insights from cpDNA sequencing and amplified fragment length polymorphisms genotyping indicated a recent diversification in the three extant Fly Orchid species, which may have been further obscured by active migration and admixture across the European continent. Our genetic results still indicate weak but noticeable phylogeographic clustering that partially correlates with the described species. Particularly, we report several isolated haplotypes and genetic clusters in central and southeastern Europe. With regard to the morphological, ecological and genetic aspects, we discuss the endemism status within the Fly Orchid group from evolutionary, taxonomical and conservation perspectives.     

Clarification of the Rhipicephalus sanguineus group (Acari,Ixodoidea, Ixodidae). I. R. sulcatus Neumann, 1908 and R. turanicus Pomerantsev, 1936

For many years the biosystematic status of several species in the Rhipicephalus sanguineus group has been confused, with the result that they have often been misidentified. Over the years some 18 of these species have been synonymised with R. sanguineus (Latreille, 1806) itself. More recently four new species in the group have been described: R. guilhoni Morel & Vassiliades, 1963; R. moucheti Morel, 1964; R. bergeoni Morel & Balis, 1976; and R. camicasi Morel, Mouchet & Rodhain, 1976.The literature on this group is critically reviewed and the main systematic problems analysed. R. sulcatus Neumann, 1908 and R. turanicus Pomerantsev, 1936 are two species that were confused both morphologically and ecologically. This has resulted in erroneous conclusions regarding their host relationships and distributions. Integrated biological, morphological and ecological studies on these two species have been conducted. Cross-breeding experiments have proved that both are distinct taxonomic entities. Interbreedings between African and Cypriot strains of R. turanicus demonstrated marked heterosis.A scanning electron microscope was used to determine the main diagnostic morphological differences between the larvae, nymphae and adults of R. sulcatus and R. turanicus, and the morphological similarities between African and Cypriot strains of R. turanicus. Rhipicephalus sulcatus occurs widely in the Afrotropical region in wetter ecological habitats and most frequently parasitises hares, dogs and jackals. R. turanicus occurs more-or-less throughout the Afrotropical region in a wide range of climatic biotopes, as well as in parts of southern Europe, Arabia and Asia, and is most abundant in the late rainy/early dry seasons. It occurs on a wide range of domesticated and wildlife hosts, including ground-feeding birds.     

Morphological differentiation correlates with ecological but not with genetic divergence in a Gehyra gecko

Body size affects life history, the ecological niche of an organism and its interactions with other organisms. Resultantly, marked differences in body size between related organisms are often an indication of a species boundary. This is particularly evident in the Gehyra variegata species complex of geckos, which displays differential body sizes between genetically divergent species, but high levels of intraspecific morphological conservatism. We report on a Gehyra population that displays extraordinary body size differentiation in comparison with other G. variegata species. We used morphological and environmental data to show this population is phenotypically and ecologically distinct from its parapatric congener Gehyra lazelli and that morphology and ecology are significantly correlated. Contrastingly, mtDNA analysis indicates paraphyly between the two groups, and allele frequencies at six microsatellite loci show no population structure concordant with morpho‐/ecotype. These results suggest either ecological speciation or environmentally induced phenotypic polymorphism, in an otherwise morphologically conservative group.     

Postembryonal morphological variation of <Emphasis Type="Italic">Daphnia galeata</Emphasis> in water bodies of different types

Despite many ecological studies the population morphological variability within the freshwater crustacean genus Daphnia is poorly investigated, especially during postembryonic development. Unusual phenotypic plasticity of some Daphnia species results in tremendous difficulties in morphological species delineation. The ontogenetic morphological variation of this species was studied, revealing the general trends in body shape variation in different populations. The morphotypes of size and age groups of D. galeata turned out to be more variable at the mouth of the Kargat River (Lake Chany basin) than in Lake Todzha (Bol’ shoi Yenisei River basin); however, the growth of characters such as the helmet and tail spine was described by an allometric function and their absolute sizes decreased with age in Daphnia from both water basins. It is shown that the first mature size-and-age group of D. galeata is most suitable for investigating population morphological variation.     

Four new species of Typhlocharis (baetica group) (Coleoptera: Carabidae: Anillini) from southwestern Iberian Peninsula with notes on their biogeographical and morphological implications

Four new species of Typhlocharis (Carabidae: Anillini) are described from the southwest of the Iberian Peninsula, assigned to the baetica species group. T. prima sp.n. , T. secunda sp.n. and T. tertia sp.n. (from La Palma del Condado, Huelva, Spain) are syntopic, and T. quarta sp.n. (from Barrancos, Beja, Portugal) is the first species of the group with umbilicate series 4 + 4. They represent, respectively, the southernmost and westernmost distribution data for the group. The baetica group remains well defined and includes ten species. The diagnosis is simplified, with the confirmation that many morphological features characteristic of this group are widespread within the genus. The defining character is the presence of denticles in apical margin of elytra, not associated to the seventh stria or to the elytral suture. The new species provide morphological data that suggest the baetica and silvanoides groups are closely related. Distribution of both groups in the south of the Iberian Peninsula and the presence of morphological characters that are considered plesiomorphic are coherent with the hypothesis of betic‐riffain origin of the genus. They also support the hypothesis of easy alteration of the umbilicate pattern between closely related species and the independent origin of apical denticles in the group compared with those present in other species of the genus. The presence of three well‐differentiated size ranges in syntopic populations suggest ecological diversification to avoid interspecific competition.     

Ecological differentiation,speciation, and rarity: How do they match in Tephroseris longifolia agg. (Asteraceae)?

Tephroseris longifolia agg. is a complex group of outcrossing perennials distributed throughout Central Europe. Recent morphological study revealed six morphotypes corresponding to five previously distinguished subspecies, together with Alpine and Pannonian morphotypes of T. longifolia subsp. longifolia. The delimited morphotypes differ in relative DNA content, geographical range, and rarity. We compared ecological niches of the six morphotypes in order to assess the impact of ecological differentiation on the speciation processes within the T. longifolia agg. Further, we examined whether morphotypes with small range are more ecologically specialized than their widespread relatives. The distribution area of the aggregate includes the Alps, Apennines, Carpathians, and the Pannonian Basin. Ecological variables linked to climate, topography, soil, and vegetation were gathered from 135 circular plots recorded in 35 localities. Related variables were grouped to describe the partial ecological niches: climatic, topographic, pedological, biotic, and coenotic (based either on vascular plants or on bryophytes), each of them visualized as an envelope in the two‐dimensional nonmetric multidimensional scaling ordination space. Each partial ecological niche for a given morphotype was characterized by its position (location of the envelope centroid), breadth (surface of the envelope), and overlaps with envelopes of the other morphotypes. Mantel statistics based on Spearman correlation coefficients were used to quantify differentiation of morphotypes in ecological parameters represented by the partial ecological niches. The significant niche differentiation was confirmed for climatic, topographic, pedological, and vascular plant‐based coenotic niches. Ecological niche differentiation corresponded well to morphological and partially also to karyological differentiation. Narrowly distributed morphotypes occupied more specific habitats and had narrower ecological niches than their widespread relatives. Ecological differentiation could be considered an important driver in allopatric speciation within the T. longifolia agg. Our results demonstrate that quantification of ecological divergence is helpful in assessing evolutionary history of closely related taxa.     

Correlates of ecological dominance within Pheidole ants (Hymenoptera: Formicidae)

1. In any group of organisms, one can almost invariably find some species that are ecologically dominant (i.e. disproportionately more abundant and widespread), whereas others are comparatively less prevalent. Understanding of the causes of variation in ecological dominance has been elusive, particularly given that dominant and subordinate species often lack obvious features that could predict their abundance in nature. 2. In this study, physiological, behavioural, morphological, and phylogenetic information is integrated in an effort to understand the mechanisms underlying ecological dominance in ants using the hyperdiverse ant genus Pheidole (Formicidae: Myrmicinae) as a model system. Field estimates of the relative abundance of 10 Pheidole species were compared with potential correlates, which included behavioural (walking velocity), physiological (tolerance to high and low temperatures and desiccation), and morphological traits (body size and degree of dimorphism in the worker caste). A molecular phylogeny of the tested species was also generated to account for potential confounding effects of phylogenetic non‐independence. 3. Dominant Pheidole species were characterised by higher environmental tolerance with respect to temperature and humidity, as well as faster walking speeds. On the other hand, no morphological correlates of ecological dominance were detected. Interestingly, subordinate species showed no evidence of trade‐off in performance, being both more fragile to environmental challenges and slower in their walking speeds. 4. These results provide important insights into the mechanisms involved in local species coexistence in Pheidole.     

ECOLOGICAL DIVERSIFICATION AND COMMUNITY STRUCTURE IN THE OLD WORLD LEAF WARBLERS (GENUS PHYLLOSCOPUS): A PHYLOGENETIC PERSPECTIVE

I investigated the historical basis for variation in regional species diversity. I used a molecular phylogenetic analysis within a single genus of birds (the Old World leaf warblers, genus Phylloscopus) in conjunction with ecological studies in Europe, the Himalayas, and Japan to evaluate the importance of historical events in shaping the present constellation of morphology and behavior in the three different regions. The relatively depauperate assemblages have different histories. In Japan, there was invasion of several lineages, which have more closely related species elsewhere in Asia, whereas in Europe there was also limited in situ speciation. Much of the structure of peripheral communities is attributable to invasions from species-rich Asia, with little in situ morphological diversification. Within the Phylloscopus there are several phylogenetic clades with nonoverlapping size distributions. Major ecological and morphological shifts occurred early in the history of diversification within the group, and rarely since.     

Variation in morphology and functional performance across distinct evolutionary lineages of the Moorish gecko (Tarentola mauritanica) from the Iberian Peninsula

Deciphering the mechanisms that underlie morphological and functional diversity is essential for understanding how organisms adapt to their environment. Interestingly, phenotypic divergence does not necessarily correspond to the geographic and genetic separation between populations. Here, we explored the morphological and functional divergence among populations of two genetically differentiated clades of the Moorish gecko, Tarentola mauritanica. We used linear and geometric morphometrics to quantify morphological variation and investigated how it translates into biting and CLIMBING PERFORMANCE, to better understand the mechanisms potentially underlying population and lineage divergence. We found marked morphological differences between clades, both in body size and head shape. However, much of this differentiation is more strongly related to local variation between populations of the same clade, suggesting that recent ecological events may be more influential than deep evolutionary history in shaping diversity patterns in this group. Despite a lack of association between morphology and functional diversification in the locomotor system of the Moorish gecko, straightforward links are observed between head morphology and biting performance, providing more hints on the possible underlying causes. Indeed, variation in bite force is mostly determined by size variation and sexual dimorphism, and differences between the two clades concern how sexual variation is expressed, reinforcing the idea that both social and ecological factors contribute in shaping differentiation. Interestingly, the individuals from the islets off the coast of Murcia exhibit particular morphological and functional traits, which suggests that the ecological conditions related to insularity may drive the phenotypic differentiation of this population.     

Comparative morphology of Western Australian varanid lizards (Squamata: Varanidae)

Varanid lizards, which vary considerably in body mass both interspecifically and intraspecifically, are generally considered to be morphologically similar. However, significant and non-isometric variation in the relative appendage dimensions for 17 species of Western Australian goannas suggest that these lizards are not morphologically conservative. The first and second canonical variates clearly distinguish the two subgeneral Odatria and Varanus, and species are generally sexually dimorphic. The morphological variation observed among these 17 species of goanna is associated with foraging mode and ecology. However, no single or small group of morphological dimensions discriminates phylogenetic groups, sexes, or ecological groups, and body size is an important component in these analyses. J. Morphol. 233:127–152, 1997. © 1997 Wiley-Liss, Inc.     

ADAPTIVE RADIATION AND GENETIC DIFFERENTIATION IN HAWAIIAN BIDENS

The genus Bidens (Asteraceae) has undergone extensive adaptive radiation on the Hawaiian Islands. The 19 species and eight subspecies endemic to Hawaii exhibit much more morphological and ecological differentiation than the continental members of the genus. However, the Hawaiian taxa have the same chromosome number and retain the capacity to interbreed in all possible combinations. Twenty-two populations of 15 Hawaiian taxa and four populations of American taxa were compared at 21 loci controlling eight enzyme systems. Populations of Hawaiian taxa are highly polymorphic. However, little genetic differentiation has occurred among taxa in spite of the high levels of genetic variability. Genetic identities calculated for pairs of populations show that populations of the same taxon are genetically more similar than are populations belonging to different taxa, but all values are high. The level of genetic differentiation that has occurred among the species of Hawaiian Bidens is comparable to the level of genetic differences found among populations within single continental plant species. Moreover, there is no correlation between the isozyme data and morphological data. No groups of taxa are evident in the genetic data, although morphological groups exist. Genetic differentiation at isozyme loci has not occurred at the same rate as the acquisition of presumably adaptive morphological and ecological characters in Hawaiian Bidens. Adaptive radiation may be limited to a few genes controlling morphological and ecological characters.     

Evolution of skull and body shape in Triturus newts reconstructed from three‐dimensional morphometric data and phylogeny

To explore the relationship between morphological change and species diversification, we reconstructed the evolutionary changes in skull size, skull shape, and body elongation in a monophyletic group of eight species that make up salamander genus Triturus. Their well‐studied phylogenetic relationships and the marked difference in ecological preferences among five species groups makes this genus an excellent model system for the study of morphological evolution. The study involved three‐dimensional imagery of the skull and the number of trunk vertebrae, in material that represents the morphological, spatial, and molecular diversity of the genus. Morphological change largely followed the pattern of descent. The reconstruction of ancestral skull shape indicated that morphological change was mostly confined to two episodes, corresponding to the ancestral lineage that all crested newts have in common and the Triturus dobrogicus lineage. When corrected for common descent, evolution of skull shape was correlated to change in skull size. Also, skull size and shape, as well as body shape, as inferred from the number of trunk vertebrae, were correlated, indicating a marked impact of species' ecological preferences on morphological evolution, accompanied by a series of niche shifts, with the most pronounced one in the T. dobrogicus lineage. The presence of phylogenetic signal and correlated evolutionary changes in skull and body shape suggested complex interplay of niche shifts, natural selection, and constraints by a common developmental system. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 243–255.     

The phylogeny ofActaea (Ranunculaceae): A biogeographical approach

Phylogenetic analyses of the genusActaea were performed using morphological, ecological and biogeographical characters. Using solely morphological characters, the relationships of the three identified species-groups remain uncertain. Close biogeographical examination and comparison of the areas with ecological peculiarities as well as climate data gave important insight into the phylogeny ofActaea and the whole tribe. Consequently, the obtained biogeographical data were used for phylogenetic reconstructions. Both, from the point of view of morphological and biogeographical data,A. pachypoda andA. asiatica are the most ancestral species. They grow on the east sides of the continents, mainly in broad-leaved forests. In West Eurasia the apomorphicA. spicata andA. acuminata occur under similar climatic and ecological conditions, but these species are adapted to another climate rhythm. The most advanced species (A. erythrocarpa, A. rubra) are to be found in the boreal forests where they are widely distributed. This biogeographical approach revealed that the evolution of the species led to a gradual widening and shifting of their ecological constitutions.     

Solenicola setigera is the first characterized member of the abundant and cosmopolitan uncultured marine stramenopile group MAST‐3

Culture‐independent molecular methods based on the amplification, cloning and sequencing of small‐subunit (SSU) rRNA genes are a powerful tool to study the diversity of prokaryotic and eukaryotic microorganisms for which morphological features are not conspicuous. In recent years, molecular data from environmental surveys have revealed several clades of protists lacking cultured and/or described members. Among them are various clades of marine stramenopiles (heterokonts), which are thought to play an essential ecological role as grazers, being abundant and distributed in oceans worldwide. In this work, we show that Solenicola setigera, a distinctive widespread colonial marine protist, is a member of the environmental clade MArine STramenopile 3 (MAST‐3). Solenicola is generally considered as a parasite or an epiphyte of the diatom Leptocylindrus mediterraneus. So far, the ultrastructural, morphological and ecological data available were insufficient to elucidate its phylogenetic position, even at the division or class level. We determined SSU rRNA gene sequences of S. setigera specimens sampled from different locations and seasons in the type locality, the Gulf of Lions, France. They were closely related, though not identical, which, together with morphological differences under electron microscopy, suggest the occurrence of several species. Solenicola sequences were well nested within the MAST‐3 clade in phylogenetic trees. Since Solenicola is the first identified member of this abundant marine clade, we propose the name Solenicolida for the MAST‐3 phylogenetic group.