British plants as aliens in New Zealand cities: residence time moderates their impact on the beta diversity of urban floras

Anthropogenic activities have weakened biogeographical barriers to dispersal, thereby promoting the introduction, establishment and spread of alien species outside their native ranges. Several studies have identified a number of biological and ecological drivers that contribute to the establishment of plant species in the invaded range. One long-term factor that is generally accepted as a relevant determinant of invasion success is residence time, or time since first introduction into the new region. Residence time is often an important correlate of range extent in the invaded region, such that alien species with longer residence times in the novel environment tend to be more widely distributed. Plant species that were introduced in different regions at different times provide a unique opportunity to examine the effect of residence time on invasion success. In this paper, we examined how residence time affects the beta diversity of alien plants in selected urban floras of New Zealand and of English and Irish cities. We used an intercontinental plant exchange as a model system, comparing groups of species introduced to New Zealand and to the British Isles at different times (i.e., species native to the British Isles, British archaeophytes and British neophytes) and asked if differences in their beta diversity can be related to differences in their residence times. Our results suggest that observed patterns of beta diversity among the urban floras of New Zealand and of English and Irish cities can be attributed to a combination of residence time and of pre-adaptation to urban habitats that evolved, or were filtered in association with human activities, before the species were introduced into the invaded range

Seed treatment affects Meloidogyne incognita penetration, colonization and reproduction on cotton Tratamento de sementes afeta a penetração, colonização e reprodução de Meloidogyne incognita em algodão

The effect of abamectin, applied as seed treatment, on Meloidogyne incognita penetration, colonization, and reproduction on cotton was evaluated in two greenhouse experiments. Second stage juveniles (J2) penetration was evaluated 3, 9 and 15 days after germination (dag), whereas the nematode colonization was evaluated 27dag, by counting the total number of galls and egg masses per root system. Eggs and J2 were extracted from the roots to assess the nematode reproduction at 50 and 100dag. The seed treatment caused a decrease in J2 penetration in the roots, resulting in lower colonization and reproduction of M. incognita. These findings are discussed considering the environmental aspects of abamectin in the soil and the current practices for the crop management.<br>O efeito de abamectina em tratamento de sementes na penetração, colonização e reprodução de Meloidogyne incognita, em algodão, foi avaliado em dois experimentos de casa de vegetação. A penetração de juvenis de segundo estádio (J2) foi avaliada aos três, nove e 15 dias após a germinação (dag), enquanto que a colonização 27dag foi avaliada por meio da contagem do número total de galhas e massas de ovos por sistema radicular. Ovos e J2 de M. incognita foram extraídos das raízes para determinar a reprodução do nematoide aos 50 e 100dag. O tratamento de sementes diminuiu a penetração dos J2 nas raízes, resultando em menor colonização e reprodução de M. incognita. Os resultados obtidos são discutidos tendo em vista os aspectos ambientais da presença de abamectina no solo e as práticas agrícolas em uso