New molecular data favour an anthropogenic introduction of the wood mouse (Apodemus sylvaticus) in North Africa

According to fossil data, the wood mouse arrived in North Africa 7500 ya, while it was present in Europe since Early Pleistocene. Previous molecular studies suggested that its introduction in North Africa probably occurred via the Strait of Gibraltar more than 0.4 Mya ago. In this study, we widely sampled wood mice to get a better understanding of the geographic and demographic history of this species in North Africa and possibly to help resolving the discrepancy between genetic and palaeontological data. Specifically, we wanted to answer the following questions: (1) When and how did the wood mouse arrive in North Africa? and (2) What is its demographic and geographic history in North Africa since its colonization? We collected in the field 438 new individuals and used both mtDNA and six microsatellite markers to answer these questions. Our results confirm that North African wood mice have a south‐western European origin and colonized the Maghreb through the Strait of Gibraltar probably during the Mesolithic or slightly after. They first colonized the Tingitana Peninsula and then expanded throughout North Africa. Our genetic data suggest that the ancestral population size comprised numerous individuals reinforcing the idea that wood mice did not colonize Morocco accidentally through rafting of a few individuals, but via recurrent/multiple anthropogenic translocations. No spatial structuring of the genetic variability was recorded in North Africa, from Morocco to Tunisia.     

Selection of source material for introduction of the locally rare and threatened fern species Asplenium septentrionale

Background: Forked spleenwort, Asplenium septentrionale, is a mainly petrophilous fern species in European mountains and rare on acidic siliceous rocks in lowland areas of the continent, where habitats are fragmented and populations isolated. In Estonia, the single extant population is very small, occupies a restricted area and is threatened by human disturbances. An introduction project of the species was prepared to form new populations in new protected sites using ex-situ propagated young sporophytes as transplantation material.

Aims: To obtain data on the species recruitment population biology and provide context information for selecting donor plant material.

Methods: We sampled three regional/local donor populations. First, we carried out a laboratory breeding experiment to evaluate the populations’ ability for intra-gametophytic selfing. Second, to estimate differences in fitness of offspring among the populations, we grew young sporophyte plants in a pot experiment under controlled conditions in a common garden.

Results: The Estonian population showed very high capacity (90%) for intra-gametophytic selfing, as well as high rate of sporophytic mortality (83%), but the rates are comparable to one of the reference populations in Finland. However, plants of Estonian population were smaller.

Conclusions: The Estonian population may represent a unique pre-adapted or locally adapted genotype; therefore, it needs more efficient protection in its present location. Planting material for introduction should be collected from the local population, as the best locally adapted. Only in the risk of severe environmental change and of extinction, several neighbouring populations could be pooled to maximise genetic diversity.     

The introduction and recovery in the United States ofAnaphes diana [Hym.: Mymaridae], an egg parasite ofSitona weevils [Col.: Curculionidae]

Anaphes diana (Girault) (=Patasson lameerei Debauche), a mymarid egg parasite ofSitona spp., was introduced from Europe beginning in 1976 and is now tentatively established in the United States. Techniques are described for the separation of eggs ofSitona spp. from soil, using a series of fine-mesh sieves, water, and a saturated salt solution. Data from 9 years of sampling in an alfalfa field at Newark, Del. (>19,300 host eggs extracted), showed that the mean peak density of viable overwintering eggs ofSitona hispidulus (F.) was 14.6 per 100 cm³ of 1 cm deep surface soil. At the study site,Sitona egg densities consistently increased during the fall as a result of oviposition, peaked during January and February and decreased during the spring as a result of egg hatch. Although the incidence of parasitism byA. diana remained surprisingly low (0.29%), the fact that the species was recovered during 3 years and up to 7 years after the last release, indicates that it has colonized at the Delaware release site.      

A strong genetic footprint of the re‐introduction history of Alpine ibex (Capra ibex ibex)

A population’s neutral genetic variation is a composite of its size, degree of isolation and demographic history. Bottlenecks and founder events increase genetic drift, leading to the loss of genetic variation and increased genetic differentiation among populations. Gene flow has the opposite effects. Thus, gene flow can override the genetic patterns caused by founder events. Using 37 microsatellite loci, we investigated the effects of serial bottlenecks on genetic variation and differentiation among 42 Alpine ibex populations in Switzerland with known re‐introduction histories. We detected a strong footprint of re‐introduction events on contemporary genetic structure, with re‐introduction history explaining a substantial part of the genetic differentiation among populations. As a result of the translocation of a considerable number of individuals from the sole formerly surviving population in northern Italy, most of the genetic variation of the ancestral population is now present in the combined re‐introduced Swiss populations. However, re‐introductions split up the genetic variation among populations, such that each contemporary Swiss population showed lower genetic variation than the ancestral population. As expected, serial bottlenecks had different effects on the expected heterozygosity (He) and standardized number of alleles (sNa). While loss of sNa was higher in the first bottlenecks than in subsequent ones, He declined to a similar degree with each bottleneck. Thus, genetic drift was detected with each bottleneck, even when no loss of sNa was observed. Overall, more than a hundred years after the beginning of this successful re‐introduction programme, re‐introduction history was the main determinant of today’s genetic structure.     

Parasites and invasions: a biogeographic examination of parasites and hosts in native and introduced ranges

Aim To use a comparative approach to understand parasite demographic patterns in native versus introduced populations, evaluating the potential roles of host invasion history and parasite life history. Location North American east and west coasts with a focus on San Francisco Bay (SFB). Methods Species richness and prevalence of trematode parasites were examined in the native and introduced ranges of two gastropod host species, Ilyanassa obsoleta and Littorina saxatilis. We divided the native range into the putative source area for introduction and areas to the north and south; we also sampled the overlapping introduced range in SFB. We dissected 14,781 snails from 103 populations and recorded the prevalence and identity of trematode parasites. We compared trematode species richness and prevalence across the hosts’ introduced and native ranges, and evaluated the influence of host availability on observed patterns. Results Relative to the native range, both I. obsoleta and L. saxatilis have escaped (lost) parasites in SFB, and L. saxatilis demonstrated a greater reduction of trematode diversity and infection prevalence than I. obsoleta. This was not due to sampling inequalities between the hosts. Instead, rarefaction curves suggested complete capture of trematode species in native source and SFB subregions, except for L. saxatilis in SFB, where infection was extremely rare. For I. obsoleta, infection prevalence of trematodes using fish definitive hosts was significantly lower in SFB compared to the native range, unlike those using bird hosts. Host availability partly explained the presence of introduced trematodes in SFB. Main conclusions Differential losses of parasite richness and prevalence for the two gastropod host species in their introduced range is probably the result of several mechanistic factors: time since introduction, propagule pressure, vector of introduction, and host availability. Moreover, the recent occurrence of L. saxatilis’ invasion and its active introduction vector suggest that its parasite diversity and distribution will probably increase over time. Our study suggests that host invasion history and parasite life history play key roles in the extent and diversity of trematodes transferred to introduced populations. Our results also provide vital information for understanding community‐level influences of parasite introductions, as well as for disease ecology in general.     

北方引种二乔木兰育苗技术及经济意义

二乔木兰(Magnolia soulangeana Soul.-Bod.)分布于我国广州、杭州、昆明等地。经引种,二乔木兰在辽宁西部(北纬41°12′～42°17′)这块高寒之地也能生长,且已开花结实并培育出引种后的子代苗木。1991年引入二乔木兰栽植成功。1995年开花,2000年该批树木结实。2005年试验播种、扦插等育苗,直到2015年才初步完成播种育苗关。9月下旬采种,种子需经低温储藏100～150天,种子6℃始萌动,催芽需20～25℃,播种25～30天出苗。二乔木兰是辽宁乃至东北少有的阔叶花卉树种,其栽培育苗成功具有重要经济价值。     

Migration patterns and changes in population biology associated with the worldwide spread of the oilseed rape pathogen Leptosphaeria maculans

Pathogen introductions into novel areas can lead to the emergence of new fungal diseases of plants. Understanding the origin, introduction pathways, possible changes in reproductive system and population size of fungal pathogens is essential in devising an integrated strategy for the control of these diseases. We used minisatellite markers to infer the worldwide invasion history of the fungal plant pathogen Leptosphaeria maculans, which causes stem canker (blackleg) of oilseed and vegetable brassicas. Clustering analyses partitioned genotypes into distinct populations corresponding to major geographic regions, along with two differentiated populations in Western Canada. Comparison of invasion scenarios using Approximate Bayesian Computation suggested an origin of the pathogen in the USA, the region where epidemics were first recorded, and independent introductions from there over the last few decades into Eastern Canada (Ontario), Europe and Australia. The population in Western Canada appeared to be founded from a source in Ontario and the population in Chile resulted from an admixture between multiple sources. A bottleneck was inferred for the introduction into Western Canada but not into Europe, Ontario or Australia. Clonality appeared high in Western Canada, possibly because environmental conditions there were less conducive to sexual reproduction. Leptosphaeria maculans is a model invasive pathogen with contrasting features in different regions: shallow population structure, high genetic variability and regular sexual recombination in some regions, by comparison with reduced genetic variability, high rates of asexual multiplication, strong population structure or admixture in others.