Search results for " Najas"
showing 3 items of 3 documents
Founder population size and number of source populations enhance colonization success in waterstriders.
2002
Understanding the factors that underlie colonization success is crucial both for ecological theory and conservation practices. The most effective way to assess colonization ability is to introduce experimentally different sets of individuals in empty patches of suitable habitat and to monitor the outcome. We translocated mated female waterstriders, Aquarius najas, into 90 streams that were not currently inhabited by the species. We manipulated sizes of propagules (from 2 to 16 mated females) and numbers of origin populations (one or two). Three origin populations were genetically different from each other, but they were less than 150 km from the streams of translocation. The results demonst…
The unnoticed northward expansion of Najas marina subsp. armata (Hydrocharitaceae) in the Mediterranean area: an effect of climate change?
2022
Recent reports of Najas marina L. (Hydrocharitaceae) from Sicily have been interpreted as a confirmation of its presence on the island, where it was earlier mentioned in the 1800s. However the recent finds do not represent “N. marina” (currently N. major All.) but N. marina subsp. armata Horn (= N. delilei Rouy), a different taxon, previously not recorded from Sicily. According to those reports and several new finds presented here, it appears to be invading reservoirs and lakes in southern Sicily and seems to be naturally expanding its range. Climate change is suggested as possible cause of this shift. The same trend appears to be taking place across the whole N Mediterranean area, from Por…
Geographical variation in wing polymorphism of the waterstrider Aquarius najas (Heteroptera, Gerridae)
1999
The waterstrider Aquarius najas is wingless in Northern Europe, while winged individuals occur frequently in Central and Southern Europe. To test if the latitudinal difference is genetically controlled, we collected mature individuals from 10 different populations and raised their offspring in ‘common garden’ laboratory conditions. Half of these populations were from southern and the other half from central Finland. Daylength and temperature do influence wing development among other species of waterstriders, and thus we maintained a similar short daylength and warm conditions for all populations. These conditions should be favourable for wing development in general. Among laboratory-bred in…