Search results for "Systematics"
showing 10 items of 6702 documents
Phylogenetic analysis of the thiolase family. Implications for the evolutionary origin of peroxisomes
1992
The thiolase family is a widespread group of proteins present in prokaryotes and three cellular compartments of eukaryotes. This fact makes this family interesting in order to study the evolutionary process of eukaryotes. Using the sequence of peroxisomal thiolase from Saccharomyces cerevisiae recently obtained by us and the other known thiolase sequences, a phylogenetic analysis has been carried out. It shows that all these proteins derived from a primitive enzyme, present in the common ancestor of eubacteria and eukaryotes, which evolved into different specialized thiolases confined to various cell compartments. The evolutionary tree obtained is compatible with the endosymbiotic theory fo…
Molecular markers reflect differentiation of Fusarium oxysporum forma speciales on tomato and forma on eggplant
2013
Selective pressure induces pathogens to change their method of infection and, sometimes, causes species to become infectious. Pathogenic fungi must differentiate different morphological and physiological properties during the process of host specialization in their life cycle. In the present study, we conducted a genetic investigation and compared similarities within a generation of Fusarium oxysporum forma speciales (f. sp.) infecting tomato and forma (f.) infecting eggplants using selected ISSR and RAPD markers, two horticultural commodities belonging to the same taxon of the Solanaceae. Interestingly, genetic data showed that fungi belonging to F. oxysporum f. sp. infecting tomato have a…
Genetic evidence for divergent selection onOenanthe conioidesandOe. aquatica(Apiaceae), a candidate case for sympatric speciation
2014
The opportunity for habitat shift in sympatry is thought to be an important factor in sympatric speciation by facilitating assortative mating and offering opportunities for divergent selection. Oenanthe conioides (Apiaceae) is a narrow endemic from the lower Elbe river area (Germany) where it is restricted to areas experiencing fresh water tides inundating the plants twice a day. The species was shown to have originated from Oe. aquatica which is widely distributed in Europe and grows in still or slowly flowing fresh water. Reciprocal transplant experiments have previously shown that in both habitats the non-native species is less fit than the native, and several phenotypic traits have been…
Genetic cohesion of Eresus walckenaeri (Araneae, Eresidae) in the eastern Mediterranean
2005
The eresid spider genus Eresus is morphologically and ecologically conservative. At least three species occur in Europe. However, deep genetic divergence among geographical samples within two species, E. cinnaberinus and E. sandaliatus, may suggest more cryptic species. In the present study we investigate the genetic cohesion of the third species, Eresus walckenaeri, throughout its eastern Mediterranean distribution range, relative to the E. cinnaberinus–E. sandaliatus species complex. Eresus walckenaeri specimens were monophyletic. Genetic discreteness of E. walckenaeri in a region of sympatry with its sister species in Greece provides evidence for species integrity of E. walckenaeri withi…
Impact of a social parasite on ant host populations depends on host species, habitat and year
2011
Parasites often affect the abundance and life-history traits of their hosts. We studied the impact of a social parasite - a slavemaking ant - on host ant communities using two complementary field manipulations. In the first experiment, we analysed the effect of social parasite presence on host populations in one habitat. In a second experiment, conducted in two habitats, we used a cross-fostering design, analysing the effect of sympatric and allopatric social parasites. In the first experiment, host colonies benefited to some extent from residing in parasite-free areas, showing increased total production. Yet, in the second experiment, host colonies in plots containing social parasites were…
Species-specific song convergence in a moving hybrid zone between two passerines
2003
Moving hybrid zones are receiving increasing attention. However, so far little is known about the proximate mechanisms underlying these movements. Signalling behaviour, by individuals engaged in interspecific sexual and aggressive interactions, may play a crucial role. In this study, we investigated song variation within a moving hybrid zone between two warblers, Hippolais polyglotta and H. icterina. In these species, song is involved in interspecific territoriality and, probably, in mixed pairings. We showed that allopatric populations of the two species are clearly acoustically differentiated. However, interspecific differences faded out in sympatry as a result of an overall pattern of co…
Interspecific aggression and character displacement in the damselfly Calopteryx splendens
2004
Problems in species recognition are thought to affect the evolution of secondary sexual characters mainly through avoidance of maladaptive hybridization. Another, but much less studied avenue for the evolution of sexual characters due to species recognition problems is through interspecific aggression. In the damselfly, Calopteryx splendens, males have pigmented wing spots as a sexual character. Large-spotted males resemble males of another species, Calopteryx virgo, causing potential problems in species recognition. In this study, we investigate whether there is character displacement in wing spot size and whether interspecific aggression could cause this pattern. We found first that wing …
The component helminth community in six sympatric species of Ardeidae.
2005
We studied the helminth communities in 6 sympatric species of Ardeidae (Ixobrychus minutus (Linnaeus, 1766), Nycticorax nycticorax (Linnaeus, 1758), Bubulcus ibis (Linnaeus, 1758), Egretta garzetta (Linnaeus, 1766), Ardea cinerea (Linnaeus, 1758), and Ardea purpurea (Linnaeus, 1766)) from "La Albufera de Valencia," Spain. The survey revealed 13 species of helminth parasites: 5 digeneans, 2 cestodes, and 6 nematodes. The component helminth communities of the Ardeidae examined are depauperate and conform to the pattern typically found in isolationist communities, probably because of their high trophic dependence on a few prey species. Evenness was positively correlated with richness and abund…
Low parasitism rates in parthenogenetic bagworm moths do not support the parasitoid hypothesis for sex
2012
The parasite hypothesis for sex is one of the many theories that have been suggested to solve the mystery of the widespread occurrence of sex despite its high short-term costs. It suggests that sexual lineages have an evolutionary advantage over parthenogens because they can frequently generate new genotypes that are temporarily less prone to coevolving parasites. In this study, we looked for further supporting evidence for the parasite hypothesis of sex in an attempt to understand the coexistence of sexual and parthenogenetic bagworm moths (Naryciinae). The bagworm moths and their parasitoids form one of the few natural host-parasite systems where sexual and parthenogenetic hosts are appar…
Hybridization in Calopteryx damselflies: the role of males
2008
Females are often considered responsible for hybridization between two species because usually they are the choosier sex and their cooperation is needed for successful copulation. However, males can also be responsible for hybridization, for example in species in which males are able to force copulation. We studied the pattern of hybridization in two congeneric damselfly species, Calopteryx splendens and Calopteryx virgo, and provide evidence that F1 hybrids between the two damselfly species occur in the wild. According to mitochondrial DNA analysis, hybridization is reciprocal: five of seven hybrids were sired by C. splendens and two by C. virgo males. We conducted an experiment that revea…