65 research outputs found
Presence of the Eucalyptus gall wasp Ophelimus maskelli and its parasitoid Closterocerus chamaeleon in Portugal: first record, geographic distribution and host preference
The Eucalyptus gall wasp Ophelimus
maskelli (Hymenoptera: Eulophidae) and its parasitoid
Closterocerus chamaeleon (Hymenoptera:
Eulophidae) were observed for the first time in
Portugal, in 2006 and 2007, respectively. Data on
the distribution of O. maskelli in Portugal, differences
in the susceptibility of two host species, Eucalyptus
globulus and Eucalyptus camaldulensis, and parasitism
by C. chamaeleon are given
Genetic differentiation among host-associated Alebra leafhoppers (Hemiptera: Cicadellidae)
The limited importance ascribed to sympatric speciation pro cesses via host race formation is partially due to the few
cases of host races that have been reported among host
populations. This work sheds light on the taxonomy of Alebra
leafhoppers and examines the possible existence of host
races among host-associated populations. The species of
this genus show varying degrees of host association with
deciduous trees and shrubs and, frequently, host popu lations of uncertain taxonomic status coexist and occasion ally become pests. Allozyme electrophoresis of 21 Greek
populations including sympatric, local and geographically
distant samples collected on 13 different plant species, show
that they represent at least five species: A. albostriella
Falle´n, A. viridis (Rey) (sensu Gillham), A. wahlbergi Bo Keywords: host races; leafhoppers; sympatric speciation; sibling species; allozymes; Alebra
Introduction
Sympatric speciation is a controversial subject in evol utionary biology (see Mayr, 1963; Futuyma and Mayer,
1980; Paterson, 1981; Via, 2001). One of the reasons for
this controversy is that sympatric speciation seems to be
an extremely rare phenomenon occurring only in very
few groups of taxa, represented chiefly by phytophagous
insects (Tauber and Tauber, 1977; Menken, 1981; Wood,
1993; Emelianov et al, 1995; Via, 1999; Finchak et al, 2000;
Craig et al, 2001). The limited number of reported cases
among organisms with sexual reproduction can be at
least partially attributed to the fact that taxa undergoing
sympatric speciation events must fulfill very restrictive
biological and ecological requirements.
Most sympatric speciation models demand that there is
intraspecific genetic variation in traits that differentially
affect the fitness of individuals that colonise new habitats
or hosts (Dieckman and Doebeli, 1999; Hawthorne and
Via, 2001 but see Higashi et al, 1999 and Takimoto et al,
2000). They assume that selection acting on these traits
can prevent genetic exchange between populations
(Bush, 1975; Tauber and Tauber, 1977; Diehl and Bush,
1989). In phytophagous insects, this means that host pref erences must be genetically determined and mating
should occur on the host (Bush, 1975; Diehl and Bush,
Correspondence: D Aguin-Pombo, Department of Biology, University of
Madeira, Campus Universitario da Penteada, 9000 Funchal, Madeira,
Portugal. E-mail: aguin uma.pt
Received 12 December 2000; accepted 13 December 2001
heman and two new species. Of these, one is associated
to Quercus frainetto and other is specific to Crataegus spp.
Significant genetic differences among sympatric and local
host populations were found only in A. albostriella, between
populations on Turkey oak, beech and common alder. It is
suggested that the last two of these host populations may
represent different host races. The results show that both
the host plant and geographical distance affect the patterns
of differentiation in the genus. The formation of some spec ies seems to have been the result of allopatric speciation
events while, for others, their origin can be equally explained
either by sympatric or allopatric speciation.info:eu-repo/semantics/publishedVersio
Nota preliminare al ritrovamento di monete romane e medievali nello scavo archeologico del Cortile del Tribunale di Verona
Analisi delle monete rinvenute nel corso dell'indagine archeologica nel Cortile del Tribunale di verona, uno dei primi scavi estensivi nell'Italia settentrional
Le monete
Notizia preliminare dei ritrovamenti monetali provenienti dalle indagini archeologiche dei Teatro romano di Concordia Sagittari
Quello che l'Iconografia rateriana non rappresenta
Vengono confrontate le diverse ipotesi interpretative e cronologiche dell'Iconografia rateriana, lasciando aperta la soluzion
Monete rinvenute nei livelli tardo antichi nello scavo del Capitolium di Verona
Vengono esaminati i ritrovamenti dallo scavo del Capitolium di Veron
Le monete
Vengono considerati tutti reperti numismatici recuperati nell'indagine archeologica del Capitolium di Verona nel tentativo di ricostruire il quadro della circolazione monetaria in et\ue0 tardo antic
Verona: monete provenienti dallo scavo archeologico del fabbricato del Monte dei Pegni
Notizia preliminare a proposito dei ritrovamenti monetali emersi nell'indagine archeologica del Capitolium romano di Veron
Monete
In Lessinia nel corso di una serie prolungata di ricerche di superficie sono stati rinvenuti molti reperti, testimonianza della vita e del lavoro dei pastori in un arco temporale molto lungo. Sono state recuperate anche pi\uf9 di 400 monete, prevalentemente di bronzo del XV secolo, alcune sono anche di et\ue0 romana e provengono da pascoli a quota molto alta
Le monete
Notizia preliminare a proposito dei rinvenimenti monetali emersi nel corso dell'indagine archeologica del teatro romano di Concordia Sagittari
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