Parallel phenotypic evolution in a wolf spider radiation on Galápagos

Within island archipelagos, repeated ecological settings may lead to radiations wherein similar niches are recurrently occupied. Although it has been shown that species with common habitat requirements share particular traits, it remains relatively unexplored to what extent this may lead to the repeated evolution of almost identical phenotypes (phenocopies) and how this correlates with traits subjected to sexual selection. Exploring divergence patterns of ecological and sexual relevant traits within spiders seem promising to enhance our understanding of the relative role of natural and sexual selection. Here, we conduct a detailed morphological analysis on a large set of genital and non‐genital traits (morphometrics, colour pattern) within a radiation of the wolf spider genus Hogna Simon, 1885 on Galápagos and interpret these data, taking into account their known phylogenetic relationship. Our results show that recurrent environmental gradients have led to the parallel evolution of almost identical phenotypes, which not only proves that natural selection has driven morphological divergence, but also suggests that a similar genetic or developmental basis most likely underlies this divergence. Among‐species variation in genital traits in contrast rather reflects the phylogenetic relationships on Santa Cruz and San Cristóbal. The combination of these data indicate that speciation in this system is driven by the combined effect of ecological mechanisms and allopatric divergence in sexual traits. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 123–136.     

Delineating the fishes of the Clinus superciliosus species complex in southern African waters (Blennioidei: Clinidae: Clinini), with the validation of Clinus arborescens Gilchrist & Thompson, 1908 and Clinus ornatus Gilchrist & Thompson, 1908, and with descriptions of two new species

The Clinus superciliosus complex comprises six closely related species. Three of the species were originally recognized by Gilchrist and Thompson as two distinct species, Clinus superciliosus (Linnaeus, 1758) and Clinus ornatus Gilchrist & Thompson, 1908, and a variety, Clinus superciliosus var. arborescens Gilchrist & Thompson, 1908. A number of other authors described various similar species, which subsequently were all synonymized with Clinus superciliosus. A further species, Clinus spatulatus Bennett, 1983, an obligate estuarine dweller, is known only from the Bot, Kleinmond, and Klein river estuaries in the Western Cape, South Africa. Two further species, Clinus musaicus sp. nov. (discovered while searching for C. ornatus specimens) and Clinus exasperatus sp. nov. , are herein described: the first is currently known from False Bay and the west coast of the Cape Peninsula, whereas the second species is known from only two specimens just east of False Bay. Clinus ornatus and Clinus arborescens Gilchrist & Thompson, 1908 are recognized as a valid species, and can be distinguished from C. superciliosus and C. spatulatus on the basis of meristic values, form of the orbital cirrus, position of the dorsal‐fin crest, taste bud number and pattern, diet, and coloration. All extant types of C. superciliosus are examined as specimens, or photographs and radiographs, and their validity and identification are assessed. Genetic analysis of mitochondrial and nuclear DNA supports species differentiation. A key is provided for the species complex. Furthermore, the variable coloration of four of the species, probably related to the substrate the larvae settle upon, and the increase in the number of vertebrae, and fin‐ray and spine number, with decreasing water temperature is discussed. © 2012 The Linnean Society of London, Zoological Journal of the Linnean Society 2012, 166 , 827–853.     

Role of Ethylene in Senescence of Petals--Morphological and Taxonomical Relationships

Petal senescence in mature flowers was studied in 93 speciesfrom 22 families. The initial symptom of senescence was eitherwilting or abscission, but in some species the time span betweenwilting and abscission was very short. There was no apparent relationship between corolla form (choripetalousor sympetalous), ovary position (inferior or superior with respectto the corolla) and type of senescence (initial wilting or initialabscission). In monocots no initial abscission was found, whilein dicots the difference between the wilting type and the abscissiontype was generally at the family level. With respect to petalsenescence, sensitivity to exogenous ethylene (C₂H₄) was alsorelated to the family level. Except for a few families (all tested Campanulaceae, Caryophyllaceaeand Malvaceae, and most Orchidaceae), most of the flowers investigatedthat showed initial wilting were not sensitive to exogenousethylene, e.g. all tested Compositae, Iridaceae, and Liliaceae.Most of the flowers showing initial abscission were sensitiveto exogenous ethylene (Geraniaceae, Labiatae, Ranunculaceae,Rosaceae, Scrophulariaceae). Experiments with silver thiosulphate (STS) confirmed the effectsof exogenous ethylene, both in flowers showing initial wiltingand in flowers showing initial abscission. The data indicate,therefore, that ethylene is involved in the natural senescenceof only a minority of the wilting type of flowers and in a majority(if not all) of the abscising type of flowers. Key words: Abscission, ethylene, senescence, silver thiosulphate     

Thick Root Syndrome in Cucumber (Cucumis sativus L.): A Description of the Phenomenon and an Investigation of the Role of Ethylene

In commercial growth of horticultural plants in greenhouses,high financial losses are being suffered due to the so-calledthick root syndrome (TRS), a phenomenon characterized by severedeterioration of the root system. The early symptoms of TRSin cucumber (Cucumis sativus L.) are strongly curving rootsthat are swollen and superficially damaged. Research focusedon ethylene, as both the culture practice of cucumber and theknown effects of ethylene on root growth point to a possiblerole for this phytohormone in TRS. Ethylene induced root curvatureand swelling as well as damage of the epidermal layer and outercortex of roots of cucumber plants similar to TRS symptoms.Formation of root hairs was stimulated and root elongation wasalso severely inhibited by exogenous ethylene. However, basedon experiments with the ethylene inhibitor     

Biogeography and contemporary climatic differentiation among Moroccan Salamandra algira

The opening of the Gibraltar land bridge occurred at the end of the Messinian Salinity Crisis approximately 5.3 Mya, and was one of the main causes of vicariance between European and north‐west African amphibians, resulting in the origin of several new species. However, little is currently known about the causes for post‐Messinian amphibian differentiation in the Maghreb, although it is acknowledged that the Pleistocene glaciations probably had considerable influence on several species. The current study uses both species distribution modelling (MAXENT) and information from a total of 694 bp of mitochondrial data (351 from cytochrome b and 342 from 12S rRNA) from 36 representatives of all three recognized subspecies of Moroccan Salamandra to infer the phylogeny and biogeography of Salamandra algira tingitana, which is characterized by both viviparous and ovoviviparous populations. According to the results, the split between S. a. tingitana and S. a. algira from the Rif and Middle Atlas mountains took place approximately 1.6 Mya, and could have been caused by a shift towards a colder and drier climate that occurred during the upper Pliocene, which may have resulted in the isolation of Salamandra at increasingly higher altitudes, or in other climatically favourable areas. Several lineages within S. a. tingitana originated during the Pleistocene climatic oscillations, one of which gave rise to the viviparous populations north of the Oued Martil. It is suggested that the origin of viviparity in S. a. tingitana occurred during the last 600 000 years. In order to further understand the origin of the unique viviparous population of S. algira from North Africa, predictive distribution models of the viviparous and ovoviviparous populations of S. a. tingitana were created using MAXENT to assess environmental differences. Niche divergence was subsequently determined using Schoener's D and Warren et al.'s I niche similarity metrics. Predictive modelling and niche divergence analyses revealed significant environmental differences between the two reproductive types, which could have influenced the transition from ovoviviparity to viviparity. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 626–641.     

Complex relations between freshwater macro- and meiobenthos: interactions between Chironomus riparius and Chydorus piger

• 1 The potential importance of interactions between macro- and meiobenthos in the littoral zone of takes was studied in a series of laboratory experiments with a chironomid and a chydorid.
• 2 In a situation of intraspecific density dependence, Chydorus piger Sars inhibited the growth of Chironomus riparius Meigen, while both second- and fourth-instar C, riparius stimulated the parthenogenetic reproduction of C. piger.
• 3 The meiofaunal chydorids may thus have a structuring effect on macrofaunal chironomid populations by interfering with the early-instar larvae.
• 4 With macro- and meiofaunal species both operating at the primary consumer-level of the food web, this kind of complex interaction will affect the magnitude of secondary production available to higher trophic levels.

     

A new family of lithophoran Proseriata (Platyhelminthes), with the description of seven new species from the Indo‐Pacific and South America,and the proposal of three new genera

In this contribution a new representative of the taxon Meidiama Marcus, 1946, Meidiama uruguayensis sp. nov. , from Uruguay, is described, as are six more new species, for which three new genera are proposed: Dreuxiola philippi gen. nov. sp. nov. , from the French subantarctic archipelago Kerguelen; Yorknia aprostatica gen. nov. sp. nov. ; Serrula byronensis gen. nov. sp. nov. ; Serrula maxillaria sp. nov. ; Serrula concharum sp. nov. ; and Serrula acuta sp. nov. , from eastern Australia and Tasmania. Arguments are presented to propose a new taxon to contain these new species, rather than include them in the Archimonocelididae Meixner, 1938 (of which Meidiama has been considered a member so far), as well as to remove the Calviriinae Martens & Curini‐Galletti from the Archimonocelididae to become a separate taxon Calviriidae. Possible autapomorphies for the three families are discussed. It is also concluded that, with the present state of our knowledge, no sound indications can be given about close relationships. © 2009 The Linnean Society of London, Zoological Journal of the Linnean Society, 2009, 155 , 759–773.     

Towards a 'natural' time scale for the Precambrian – A proposal

A proposal is put forward to redefine the geological time scale for the Precambrian. Flaws of the present, chronometrically defined, time scale are discussed and illustrated. It is concluded that we need to go back to the rock record to define a “natural” time scale, in which major divisions (eons, eras, etc.) are defined in terms of first-order events and transitions in the observable stratigraphic record. For the earliest part of Earth history, we need a time scale, including a formalized Hadean eon, that is fully consistent with rapidly evolving insights from planetary science.