High Immigration Rates Research Articles

Where do Trypanosoma cruzi go? The distribution of parasites in blood components from fractionated infected whole blood.

Platelets (PLTs) are the blood component most frequently involved in Trypanosoma cruzi transfusion transmission cases reported in the literature, although whole blood (WB) and red blood cells (RBCs) have also been incriminated. However, there is little knowledge of the parasite distribution among blood components. The aim of this study was to investigate in which blood component T. cruzi parasites concentrate the most, after fractionating artificially T. cruzi-infected WB. The T. cruzi parasite load was studied by a specific quantitative real-time polymerase chain reaction (qPCR) in WB, buffy coat (BC), PLT concentrates, RBCs before and after leukoreduction, and plasma (PL). The parasite load in WB experimentally infected with 1.5 × 10(6) parasites (2.78 × 10(3) parasite equivalents/mL) was unevenly distributed among the separated blood components. The highest level was found in the BC (6.94 × 10(3) parasite equivalents/mL) and RBCs before leukoreduction by filtration (2.51 × 10(3) parasite equivalents/mL), after which RBCs presented a 99.9% reduction in parasite levels. Both PL and PLTs, partially leukoreduced by centrifugation but nonfiltered, had low parasite levels, the lowest concentration being in PL. The highest parasite concentration was detected in the BC, followed by RBCs before leukoreduction. There is a notable risk of transfusion-transmitted Chagas disease associated with nonleukoreduced RBCs. Leukoreduction may be an effective prevention strategy for transfusion-transmitted T. cruzi infection, especially in endemic countries and in nonendemic countries with a high rate of immigration from Latin America.

Using stable-hydrogen isotopes to reveal immigration in an Arctic-breeding songbird population.

BackgroundKnowledge of immigration and emigration rates is crucial for understanding of population dynamics, yet little is known about these vital rates, especially for arctic songbirds. We estimated immigration in an Arctic population of northern wheatears on Baffin Island, Canada, by the use of stable hydrogen isotopes in tail feathers (δ2HK). We assumed that δ2HK values of juvenile (hatch-year) feathers grown at the breeding grounds were representative of the local population, while those of breeding adults were indicative of where they grew their feathers during their post-breeding molt the previous year. The extent to which adult isotope values differ from those of juveniles provides an estimate of the minimum level of immigration into the breeding population.ResultsMean δ2HK values did not differ in juvenile birds between years. Breeding adult birds did not differ significantly in mean δ2HK values compared to juveniles but did differ in their respective standard deviations, reflecting a significantly wider range of isotopic signatures in adults than in juveniles. Thirty-eight percent of the δ2HK values in adults were greater ± 2 SD of the mean δ2HK values of juveniles, suggesting that at least 38 % of the breeding adults were of non-local origin, thus immigrants from elsewhere.ConclusionsAlthough the use of stable isotopes has limitations, the use of stable-hydrogen isotopic markers has the potential to contribute valuable information towards understanding immigration rates in bird populations. In our study, hydrogen isotope measurements of the feathers of northern wheatears indicated a high rate of immigration into the breeding population, which is consistent with low return rates of banded breeding adults as well as implying high emigration rates of local breeders.Electronic supplementary materialThe online version of this article (doi:10.1186/s40462-016-0081-x) contains supplementary material, which is available to authorized users.

Discouraging partnerships? Teachers’ perspectives on immigration-related barriers to family-school collaboration.

This study investigates barriers to facilitating family-school partnerships with immigrant families as identified by teachers in an urban school district with high rates of immigration. Participants consisted of 18 elementary teachers who identified predominantly as Hispanic (38.9%) or non-Hispanic White (33.3%), were frequently bilingual (55.6%), and were mostly female (94.4%) with an average age of 36.5 years. Participants engaged in focus group interviews that were transcribed and open-coded. Barriers to engagement for immigrant families fell into 3 broad areas: language and culture, family resources, and families' undocumented status. Many teachers attributed the barriers preventing parental collaboration to school policies (94.4%) and ineffective communication strategies (83.3%). Teachers also identified barriers as emanating from the families themselves, including families not attending school functions (88.9%) and being unresponsive to school-initiated communication (72.2%). Teachers noted that many families lacked resources necessary for school engagement (88.9%) and were hesitant to become engaged with schools due to required screening procedures (55.6%). Overall, numerous barriers to effective family engagement were identified, several of which are directly related to immigration and residency status. Given the strong evidence suggesting that family engagement in education mediates risk for children of recent immigrants, strategies to foster meaningful engagement for all families are desperately needed (Naughton, 2004). Roles for school psychologists to facilitate effective family-school partnerships are discussed. (PsycINFO Database Record

Integrated population modelling reveals a perceived source to be a cryptic sink

Summary Demographic links among fragmented populations are commonly studied as source‐sink dynamics, whereby source populations exhibit net recruitment and net emigration, while sinks suffer net mortality but enjoy net immigration. It is commonly assumed that large, persistent aggregations of individuals must be sources, but this ignores the possibility that they are sinks instead, buoyed demographically by immigration.We tested this assumption using Bayesian integrated population modelling of Greenland white‐fronted geese (Anser albifrons flavirostris) at their largest wintering site (Wexford, Ireland), combining capture–mark–recapture, census and recruitment data collected from 1982 to 2010. Management for this subspecies occurs largely on wintering areas; thus, study of source‐sink dynamics of discrete regular wintering units provides unprecedented insights into population regulation and enables identification of likely processes influencing population dynamics at Wexford and among 70 other Greenland white‐fronted goose wintering subpopulations.Using results from integrated population modelling, we parameterized an age‐structured population projection matrix to determine the contribution of movement rates (emigration and immigration), recruitment and mortality to the dynamics of the Wexford subpopulation.Survival estimates for juvenile and adult birds at Wexford and adult birds elsewhere fluctuated over the 29‐year study period, but were not identifiably different. However, per capita recruitment rates at Wexford in later years (post‐1995) were identifiably lower than in earlier years (pre‐1995). The observed persistence of the Wexford subpopulation was only possible with high rates of immigration, which exceeded emigration in each year. Thus, despite its apparent stability, Wexford has functioned as a sink over the entire study period.These results demonstrate that even large subpopulations can potentially be sinks, and that movement dynamics (e.g. immigration) among winters can dramatically obscure key processes driving subpopulation size. Further, novel population models which integrate capture–mark–recapture, census and recruitment data are essential to correctly ascribing source‐sink status and accurately informing development of site‐safeguard networks.

Subsistence in isolation: Fishing dependence and perceptions of change on Kiritimati, the world's largest atoll

Small island nations are reliant on local fishery resources due to their geographic isolation. The people of Kiritimati, the world's largest atoll, are ranked amongst the most vulnerable to degradation of their local reef resources because of their high reef dependence and exposure to threats. We conducted semi-structured interviews in 103 households, stratified across the atoll's five villages, to characterize Kiritimati's fishery, and to examine people's perceptions of the fishery status and their fishery dependence (assessed by responses to hypothetical declines in fishery catches). High immigration rates have created a shifting baseline in the community, with more recent immigrants perceiving the local fishery to be in better condition than those who have fished on Kiritimati over the long term. Due to their high dependence on fishery resources and limited alternatives for feeding their families, 70% of respondents anticipated continuing to fish even during a fifty percent hypothetical fishery decline. Despite these limitations to adaptive capacity, the people of Kiritimati were open to discussing new conservation policies that would conserve their fisheries, suggesting that locally supported conservation strategies may aid in alleviating some of their vulnerability. This study demonstrates how poverty and geographic isolation can drive low adaptive capacity to resource changes, and suggests that policy interventions are needed to avoid further reef fishery degradation and to support fishery-dependent livelihoods.

Reconciling contradictory relationships between mobility and extinction risk in human‐altered landscapes

Summary Some empirical and theoretical studies suggest that more mobile species are less at risk in human‐altered landscapes, while others suggest the opposite. We propose three novel hypotheses to explain these contradictory findings: (i) extinction risk increases with increasing mobility when mobility is measured as emigration, but decreases with increasing mobility when mobility is measured as immigration; (ii) the most mobile species (whether measured by emigration or immigration) in unaltered landscapes are least mobile in human‐altered landscapes, so the relationship between mobility and risk is opposite when mobility is measured in unaltered and altered landscapes; and (iii) the mobility–risk relationship is ∩‐shaped; thus, the relationship is apparently positive when studied species have low‐to‐intermediate mobility, but negative when species have intermediate‐to‐high mobility. We also evaluate a fourth hypothesis that had been previously theorized: that some landscape structures drive evolution of dispersal characteristics that increase both mobility and risk, while others drive evolution of characteristics that increase mobility and decrease risk. To evaluate these four hypotheses, we created an individual‐based, spatially explicit simulation model to simulate population dynamics, evolution of dispersal characteristics and species response to habitat loss. Our simulations supported the first and fourth hypotheses. Extinction risk increased with emigration rate but decreased with immigration rate. Species in landscapes with historically more abundant, less fragmented habitat and more frequent disturbance had increased risk and mobility during habitat loss, while species in landscapes with lower matrix quality had increased risk and decreased mobility. Synthesis. This is the first study to investigate why some studies find that more mobile species are less at risk in human‐altered landscapes, while others find the opposite. Our results suggest that these contradictory relationships occur because of differences in how mobility is measured and differences in the historic structure of species' landscapes. Understanding how mobility and the historic landscape influence extinction risk can help us identify species of conservation concern. Our results suggest that we should focus on species with high emigration rates but low immigration rates, and those that evolved in landscapes with non‐fragmented habitat and high‐risk matrix.

Heart surgery for immigrants in Italy: burden of cardiovascular disease, adherence to treatment and outcomes.

Italy is a country with high rates of immigration and the knowledge of immigrant health is very fragmentary. We provide a current picture of cardiovascular disease causes and clinical outcomes following heart surgery. A clinical and echocardiographic survey was conducted on 154 consecutive immigrants referred for heart surgery to San Raffaele Hospital in Milan between 2003 and 2011. Major causes of heart disease were rheumatic heart disease (RHD) (n = 64, 41%), nonrheumatic valvulopathies (n = 41, 27%), ischemic heart disease (IHD) (n = 25, 16%), congenital heart disease (n = 13, 9%) and miscellaneous (n = 11, 7%). Median age was 49 years [interquartile range (IQR) 7-81]; 55% of patients were male. Among valvulopathies, rheumatic mitral disease was predominant (n = 56, 53%) as both single and multivalvular disease (n = 46, 73%); myxomatous prolapse emerged as the second main pattern of mitral disease (n = 30, 33%). Among patients with IHD, 72% had a high cardiovascular risk. Surgery was scheduled in 138 patients (90%). Clinical follow-up was available in 96 patients (62%) [median time 62 months (IQR 15-123)], among whom 92 (96%) were alive, four patients (4%) had died and 58 (38%) were lost. Cardiovascular diseases represent a major health topic among immigrants in developed countries. RHD still is the predominant cause of hospitalization for heart surgery, nonrheumatic valvulopathies and IHD emerging as second and third causes, respectively. Data underline the need of reinforcement of prevention and care strategies in the matter of immigrant health and warrant the urgent attention of the international public health and research communities.

Molecular Evidence of High Proportion of Plasmodium vivax Malaria Infection in White Nile Area in Sudan.

Plasmodium falciparum is a predominant malaria species that infects humans in the African continent. A recent WHO report estimated 95% and 5% of P. falciparum and P. vivax malaria cases, respectively, in Sudan. However many laboratory reports from different areas in Sudan indicated otherwise. In order to verify, we selected four hundred suspected malaria cases from Aljabalain area located in the White Nile state, central Sudan, and diagnosed them with quality insured microscopy and species-specific nested PCR. Our results indicated that the proportion of P. vivax infections among suspected malaria cases was high. We found that on average 20% and 36.5% of malaria infections in both study areas were caused by P. vivax using both microscopy and PCR, respectively. This change in pattern is likely due to the recent demographic changes and high rate of immigration from neighbouring countries in the recent years. This is the first extensive clinical study of its kind that shows rising trend in P. vivax malaria cases in White Nile area, Sudan.

Uniparental ancestry markers in Chilean populations.

The presence of Native Americans, Europeans, and Africans has led to the development of a multi-ethnic, admixed population in Chile. This study aimed to contribute to the characterization of the uniparental genetic structure of three Chilean regions. Newborns from seven hospitals in Independencia, Providencia, Santiago, Curicó, Cauquenes, Valdívia, and Puerto Montt communes, belonging to the Chilean regions of Santiago, Maule, and Los Lagos, were studied. The presence of Native American mitochondrial DNA (mtDNA) haplogroups and two markers present in the non-recombinant region of the Y chromosome, DYS199 and DYS287, indicative of Native American and African ancestry, respectively, was determined. A high Native American matrilineal contribution and a low Native American and African patrilineal contributions were found in all three studied regions. As previously found in Chilean admixed populations, the Native American matrilineal contribution was lower in Santiago than in the other studied regions. However, there was an unexpectedly higher contribution of Native American ancestry in one of the studied communes in Santiago, probably due to the high rate of immigration from other regions of the country. The population genetic sub-structure we detected in Santiago using few uniparental markers requires further confirmation, owing to possible stratification for autosomal and X-chromosome markers.

Tuberculous Pericarditis: A Complex Puzzle to Put Together

Tuberculous Pericarditis: A Complex Puzzle to Put Together

A simulation analysis of the longer-term effects of immigration on per capita in-come in an aging population

Immigration is a possible instrument for offsetting longer-run adverse effects of population aging on per capita income. Our “laboratory” is a fictitious country Alpha to which we assign demographic characteristics typical of a country experiencing population aging. Si-mulations indicate that a very high immigration rate with heavy concentration in younger working ages might be required to keep per capita income from declining. More rapid produc-tivity growth would also offset population aging as would higher rates of labour participation of older people. Longer life expectancy, taken alone, would lower per capita real income, as would higher fertility rates.

Migration and Development: Equalisation and Inequalities in Ecuador's Southern Sierra

Based upon a case study of the municipality of Cañar, in Andean Ecuador, this paper examines the conflictive relationship between migration and development to show how current approaches fail to consider the political issues implicit in this link. Instead, the concept of displacement is proposed, which, as argued in this work, implies an action (that of moving to another place) which subjects perform reflexively upon themselves. This challenges the notion of this action as a transitive one, in which the subject exerts the action on an object. Cañar combines two important elements that make it relevant for highlighting this relationship: on the one hand, it is a district with a high indigenous population and, on the other, it has had historically a high rate of immigration to the USA and Spain. These two factors make it possible to confront both the immigrants' practices and the role of nation-states in the construction of structures of exclusion and, thereby, to examine why the result of this confrontation does not necessarily turn into development. From this viewpoint, the paper discerns the role of the nation-state in constructing structures of social, political, cultural, and symbolic exclusion in the locality of origin as well as in the locality of destination of migrants, further presenting the forms of agency used by the migrants to overcome these structures. In other words, it is an attempt to take the analysis into a terrain that escapes the dichotomies between state (structures) and actors (agency).

Análisis de la convivencia escolar en las aulas multiculturales de Educación Secundaria

<p>Esta investigación pretende analizar la formación del profesorado para promover y gestionar la convivencia en las aulas en los Centros de Educación Secundaria, describir las conductas del alumnado que la alteran y ofrecer opciones de mejora.</p><p>Se realiza un análisis documental de los programas de formación inicial de las universidades; se elabora un cuestionario descriptivo y valorativo de conductas del alumnado contrarias a la convivencia y respuestas del profesorado, en cinco centros con elevado número de alumnado inmigrante; y realiza un grupo de discusión de profesorado para ofrecer opciones de mejora de estos contextos. Y constata la escasa formación inicial del profesorado en estos aspectos, comprobado la existencia de diferencias significativas en la valoración de algunas conductas en función del género, de la experiencia docente y el uso por ambos géneros de respuestas usualmente sancionadoras, y el escaso empleo de estrategias educativas/formativas que permitan aumentar la convivencia en el Centro.</p>

Colonization of a territory by a stochastic population under a strong Allee effect and a low immigration pressure.

We study the dynamics of colonization of a territory by a stochastic population at low immigration pressure. We assume a sufficiently strong Allee effect that introduces, in deterministic theory, a large critical population size for colonization. At low immigration rates, the average precolonization population size is small, thus invalidating the WKB approximation to the master equation. We circumvent this difficulty by deriving an exact zero-flux solution of the master equation and matching it with an approximate nonzero-flux solution of the pertinent Fokker-Planck equation in a small region around the critical population size. This procedure provides an accurate evaluation of the quasistationary probability distribution of population sizes in the precolonization state and of the mean time to colonization, for a wide range of immigration rates. At sufficiently high immigration rates our results agree with WKB results obtained previously. At low immigration rates the results can be very different.

American black bear population abundance and genetic structure on an island archipelago

American black bears (Ursus americanus) occur on numerous islands within the Apostle Islands National Lakeshore in Lake Superior, Wisconsin, USA, and provide an opportunity to better understand patterns in abundance and genetic structure among island populations. In 2002 and 2010, we derived genotypes from DNA obtained from hair samples collected at hair traps to estimate population abundance on Stockton (40.7 km2), Sand (11.9 km2), and Oak (20.6 km2; 2010 only) islands. We used Huggins closed-population mark–recapture models to estimate island-specific abundance and density. We used Program STRUCTURE and parentage analysis to examine inter-island population structure, migration patterns, and relatedness. In 2010, we estimated abundance on Stockton, Sand, and Oak islands to be 13.1 (95% CI = 12.4–13.8), 10.1 (95% CI = 9.3–11.0), and 18.1 (95% CI = 17.3–19.0) bears, with a density of 0.32, 0.85, and 0.88 bears/km2, respectively. Whereas abundance on Sand Island increased 60% since 2002 (N = 6.3, 95% CI = 4.0–8.6), abundance on Stockton declined 50% (N = 26.3, 95% CI = 24.7–27.9), including an 83% decline in detected females. Density on Oak Island was the highest reported in Wisconsin, although we identified 13 individuals as likely mates or offspring of a single male. We identified 4 genetic groups, corresponding to Stockton, Sand, Oak, and Mainland ancestry. No individuals on Stockton or Sand islands were assigned ancestry from another island, whereas one male on Oak Island was assigned Stockton ancestry. We detected individuals of predominately Mainland ancestry on all but Hermit Island, suggesting a high rate of immigration from the mainland. We suggest these islands can support high bear densities, but may undergo rapid shifts in sex-specific abundance. Genetic connectivity appears maintained by male-mediated gene flow, but a small number of wide-ranging females may sustain inter-island population viability.

A qualitative study of Chinese Canadian fathers' smoking behaviors: intersecting cultures and masculinities.

BackgroundChina is home to the largest number of smokers in the world; more than half of the male population smoke. Given the high rates of Chinese immigration to Canada and the USA, researchers have explored the effect of immigration on Chinese smokers. Reduced tobacco use among Chinese immigrants has been reported in the United States; however, little is known about the social factors underlying men’s smoking practices in settings where tobacco control measures have denormalized smoking, and in the context of fatherhood. The purpose of this Canada-based study was to explore the smoking-related experiences of immigrant Chinese fathers.MethodsIn this qualitative study, semi-structured telephone interviews were conducted with 22 Chinese Canadian fathers who smoked or had recently quit smoking, and had at least one child under the age of five years old.ResultsThe Chinese fathers had dramatically changed their smoking patterns due to concern for their children’s health and social norms and restrictions related to smoking in Canada. The facilitators and barriers for men’s smoking were intertwined with idealized masculine provider and protector roles, and diverse Canadian Chinese cultural norms related to tobacco use.ConclusionsThe findings have implications for the development of future smoking cessation interventions targeting Chinese Canadian immigrant smokers as well as smokers in China.

Who Supports Portable Assessment Caps?: The Role of Lock-Ins, Tax Share, and Mobility

We examine voter support in 2008 for Constitutional Amendment 1 in Florida, which modifies a Proposition 13-like property assessment growth cap by allowing homeowners to port their exempted value to a new home. Despite claims by amendment proponents that it would lower property taxes, we do not find that support was higher in precincts with a greater share of eligible property owners. Nor was support explained by the average size of existing exemptions. Instead, we find that precincts with more mobile households supported Amendment 1. In addition, we find evidence that voters understood how changing assessment methodology could affect their tax share. Under a conventional assessment cap, a homeowner who moves resets the assessed value to the market price, lowering the share of assessed value for remaining homeowners. Remarkably, we find that support for Amendment 1 falls as mobility in other parts of the city increases. This finding suggests that Amendment 1 was viewed as a way for high-mobility voters to shift the tax burden back to low-mobility homeowners. In addition, support is higher when a city has a high number of out-of-state immigrants, who have no tax exemption to port into the city, but support is lower when the city has high rates of in-state immigration. These findings suggest that voters are fairly tax savvy and as concerned with shifting the tax burden as they are with curbing absolute expenditures.

Immigration rates and species niche characteristics affect the relationship between species richness and habitat heterogeneity in modeled meta-communities.

The positive relationship between habitat heterogeneity and species richness is a cornerstone of ecology. Recently, it was suggested that this relationship should be unimodal rather than linear due to a tradeoff between environmental heterogeneity and population sizes. Increased environmental heterogeneity will decrease effective habitat sizes, which in turn will increase the rate of local species extinctions. The occurrence of the unimodal richness–heterogeneity relationship at the habitat scale was confirmed in both empirical and theoretical studies. However, it is unclear whether it can occur at broader spatial scales, for meta-communities in diverse and patchy landscapes. Here, I used a spatially explicit meta-community model to quantify the roles of two species-level characteristics, niche width and immigration rates, on the type of the richness–heterogeneity relationship at the landscape scale. I found that both positive and unimodal richness–heterogeneity relationships can occur in meta-communities in patchy landscapes. The type of the relationship was affected by the interactions between inter-patch immigration rates and species’ niche widths. Unimodal relationships were prominent in meta-communities comprising species with wide niches but low inter-patch immigration rates. In contrast, meta-communities consisting of species with narrow niches and high immigration rates exhibited positive relationships. Meta-communities comprising generalist species are therefore likely to exhibit unimodal richness-heterogeneity relationships as long as low immigration rates prevent rescue effects and patches are small. The richness-heterogeneity relationship at the landscape scale is dictated by species’ niche widths and inter-patch immigration rates. These immigration rates, in turn, depend on the interaction between species dispersal capabilities and habitat connectivity, highlighting the roles of both species traits and landscape structure in generating the richness–heterogeneity relationship at the landscape scale.

Measuring Success in a Community Conservation Project: Local Population Increase in a Critically Endangered Primate, the Yellow-Tailed Woolly Monkey (Lagothrix Flavicauda) at La Esperanza, Northeastern Peru

The yellow tailed woolly monkey ( Lagothrix flavicauda) is one of the world's most threatened primate species. It is endemic to a small area of montane forest in northern Peru, an area with high immigration and deforestation rates. Since 2007, community conservation actions have been implemented in the area of Yambrasbamba, a farming community in Amazonas department. These actions included the signing of voluntary pledges by local villagers to control hunting and forest clearance. A first population density survey was carried out in 2008/9, shortly after the implementation of these pledges; a second survey in the same area that replicated the methods used in the previous survey was carried out in 2012/13. Using transect width estimation from line transects and a Normalized Difference Vegetative Index (NDVI) from satellite images, we compared population density and deforestation rates between surveys. Results showed an increase in the L. flavicauda population at the study site, with significant increases in densities of infant ( P <0.001) and juvenile individuals ( P = 0.019). This suggests that increases are from natural population growth rather than the in-migration of groups or individuals from outlying areas. The NDVI showed low levels of deforestation still occurring in the area, but at a lower rate than the regional and national averages. Our results provide compelling evidence that Community Conservation projects can be successful in highly populated areas, and we urge conservation practitioners to involve local actors when planning and implementing initiatives.

A last stand in the Po valley: genetic structure and gene flow patterns in Ulmus minor and U. pumila.

Ulmus minor has been severely affected by Dutch elm disease (DED). The introduction into Europe of the exotic Ulmus pumila, highly tolerant to DED, has resulted in it widely replacing native U. minor populations. Morphological and genetic evidence of hybridization has been reported, and thus there is a need for assessment of interspecific gene flow patterns in natural populations. This work therefore aimed at studying pollen gene flow in a remnant U. minor stand surrounded by trees of both species scattered across an agricultural landscape. All trees from a small natural stand (350 in number) and the surrounding agricultural area within a 5-km radius (89) were genotyped at six microsatellite loci. Trees were morphologically characterized as U. minor, U. pumila or intermediate phenotypes, and morphological identification was compared with Bayesian clustering of genotypes. For paternity analysis, seeds were collected in two consecutive years from 20 and 28 mother trees. Maximum likelihood paternity assignment was used to elucidate intra- and interspecific gene flow patterns. Genetic structure analyses indicated the presence of two genetic clusters only partially matching the morphological identification. The paternity analysis results were consistent between the two consecutive years of sampling and showed high pollen immigration rates (∼0·80) and mean pollination distances (∼3 km), and a skewed distribution of reproductive success. Few intercluster pollinations and putative hybrid individuals were found. Pollen gene flow is not impeded in the fragmented agricultural landscape investigated. High pollen immigration and extensive pollen dispersal distances are probably counteracting the potential loss of genetic variation caused by isolation. Some evidence was also found that U. minor and U. pumila can hybridize when in sympatry. Although hybridization might have beneficial effects on both species, remnant U. minor populations represent a valuable source of genetic diversity that needs to be preserved.