Maintenance of high pollen dispersal in Eucalyptus wandoo, a dominant tree of the fragmented agricultural region in Western Australia

Pollen dispersal was investigated in five remnant populations of Eucalyptus wandoo, a dominant insect-pollinated tree in the fragmented agricultural region of southern Western Australia. Paternity analysis using six microsatellite loci identified a pollen source for 45% of seedlings, and the remainder were assumed to have arisen from pollen sources outside the stands. Outcrossing was variable, ranging from 52 to 89%, and long distance pollen dispersal was observed in all populations with up to 65% of pollen sourced from outside the populations over distances of at least 1 km. Modelling dispersal functions for pollination events within the two larger populations showed little difference between the four two-parameter models tested and indicated a fat-tailed dispersal curve. Similarity of direct and indirect historical estimates of gene flow indicates maintenance of gene flow at levels experienced prior to fragmentation. The study revealed extensive long distance pollen dispersal in remnant patches of trees within a fragmented agricultural landscape in the southern temperate region and highlighted the role of remnant patches in maintaining genetic connectivity at the landscape scale.     

Paternity analysis of pollen-mediated gene flow for Fraxinus excelsior L. in a chronically fragmented landscape

Paternity analysis based on microsatellite marker genotyping was used to infer contemporary genetic connectivity by pollen of three population remnants of the wind-pollinated, wind-dispersed tree Fraxinus excelsior, in a deforested Scottish landscape. By deterministically accounting for genotyping error and comparing a range of assignment methods, individual-based paternity assignments were used to derive population-level estimates of gene flow. Pollen immigration into a 300 ha landscape represents between 43 and 68% of effective pollination, mostly depending on assignment method. Individual male reproductive success is unequal, with 31 of 48 trees fertilizing one seed or more, but only three trees fertilizing more than ten seeds. Spatial analysis suggests a fat-tailed pollen dispersal curve with 85% of detected pollination occurring within 100 m, and 15% spreading between 300 and 1900 m from the source. Identification of immigrating pollen sourced from two neighbouring remnants indicates further effective dispersal at 2900 m. Pollen exchange among remnants is driven by population size rather than geographic distance, with larger remnants acting predominantly as pollen donors, and smaller remnants as pollen recipients. Enhanced wind dispersal of pollen in a barren landscape ensures that the seed produced within the catchment includes genetic material from a wide geographic area. However, gene flow estimates based on analysis of non-dispersed seeds were shown to underestimate realized gene immigration into the remnants by a factor of two suggesting that predictive landscape conservation requires integrated estimates of post-recruitment gene flow occurring via both pollen and seed.     

High Levels of Genetic Contamination in Remnant Populations of Acacia saligna from a Genetically Divergent Planted Stand

It is essential to understand the patterns of pollen dispersal in remnant vegetation occupying highly disturbed landscapes in order to provide sustainable management options and to inform restoration programs. Direct and indirect methods of paternity analysis were used to detect genetic contamination via inter‐subspecific pollen dispersal from a planted stand of nonlocal Acacia saligna ssp. saligna (ms) into remnant roadside patches of local A. saligna ssp. lindleyi (ms). Genetic contamination was detected in 25.5% (indirect paternity assignment) to 32% (direct paternity assignment) of ssp. lindleyi progeny and occurred over a distance of 1.6 km. The results support studies that suggest genetic continuity is maintained by high levels of pollen dispersal in temperate entomophilous species. The results also indicate that patchily distributed remnant populations may be exposed to substantial amounts of genetic contamination from large‐scale restoration with native taxa in the highly fragmented agricultural landscape of southern Western Australia. Management practices to reduce the risk of genetic contamination are considered.     

Mating pattern and pollen dispersal in the wild olive tree (<Emphasis Type="Italic">Olea europaea</Emphasis> subsp. <Emphasis Type="Italic">cuspidata</Emphasis>)

In this study, the mating system, contemporary pollen flow, and landscape pollen connectivity of the wild olive tree (Olea europaea subsp. cuspidata) were analyzed in a fragmented landscape of less than 4-km diameter located in north-western Ethiopia. Four remnant populations of different sizes were investigated. Eight highly polymorphic microsatellite markers were used to genotype 534 adults and 704 embryos. We used contrasting sampling schemes and different methodological approaches to analyze the pollen flow. We observed a lower rate of inbreeding and correlated mating in the fragmented vs. the non-fragmented subpopulation. Using parentage analysis, we detected a bidirectional pollen movement across subpopulations. Pollen flow was found to be directed towards small subpopulations based on parentage and anisotropic analysis. Pollen immigration amounted to more than 50%. Although most pollination occurred within a distance of less than 200 m, longer distance pollen movements of more than 3 km were also detected. Pollen dispersal in the large and dense subpopulation was reduced, and a smaller number of effective pollen sources were detected compared to a smaller fragmented subpopulation. We obtained consistent estimates for the number of effective pollen donors (approximately 6 per mother tree) using three different methods. The average pollen dispersal distance at the landscape level amounted to 276 m while at the local level, 174 m was estimated. Bigger trees were better pollen contributors than smaller trees. We showed here for the first time that pollen dispersal in wild olive follows a leptokurtic distribution.     

Effects of pollen load size on seed paternity in wild radish: the roles of pollen competition and mate choice

For sexual selection to be important in plants, it must occur at pollen load sizes typical of field populations. However, studies of the impact of pollen load size on pollen competition have given mixed results, perhaps because so few of these studies directly examined the outcome of mating when pollen load size was varied. We asked whether seed paternity after mixed pollination of wild radish was affected by pollen load sizes ranging from 22 to 220 pollen grains per stigma. We examined the seed siring abilities of 12 pollen donors across 11 maternal plants. Seed paternity was statistically indistinguishable across the pollen load sizes even though, overall, the pollen donors sired different numbers of seeds. This lack of effect of pollen load size on seed paternity may have occurred because fruit abortion and early abortion or failure of fertilization of seeds increased as load size decreased. Thus, failures of fruits and seeds sired by poorer pollen donors may keep seed paternity constant across pollen load sizes.     

Effects of pollination method on paternal success in Lesquerella fendleri (Brassicaceae)

Hand pollinations are frequently used to assess the postpollination success of different donors. We present evidence that the method used for hand pollinations can alter pollen germination rates and paternity of the resulting seeds. Two commonly used methods for hand pollination experiments are mixed pollinations, where pollen from several donors is physically mixed together, and adjacent pollinations, where pollen from one donor is close to, but not in physical contact with, pollen from other donors. These methods offer differing opportunities for pollen interaction, and for females to choose among mates. We found that the success of pollen donors in multidonor pollinations varied with pollination method in unpredictable ways across maternal plants. Pollen germination was significantly lower in adjacent pollinations, perhaps explaining some of the effects of pollination method on paternity. These results may yield insights on the factors influencing pollen success, and indicate that hand pollination experiments should employ pollination methods that mimic as closely as possible the natural arrival of pollen in nature.     

Patterns of pollen and seed dispersal in a small, fragmented population of the wind-pollinated tree Araucaria angustifolia in southern Brazil

Paternity analysis based on eight microsatellite loci was used to investigate pollen and seed dispersal patterns of the dioecious wind-pollinated tree, Araucaria angustifolia. The study sites were a 5.4 ha isolated forest fragment and a small tree group situated 1.7 km away, located in Paranalpha State, Brazil. In the forest fragment, 121 males, 99 females, 66 seedlings and 92 juveniles were mapped and genotyped, together with 210 seeds. In the tree group, nine male and two female adults were mapped and genotyped, together with 20 seeds. Paternity analysis within the forest fragment indicated that at least 4% of the seeds, 3% of the seedlings and 7% of the juveniles were fertilized by pollen from trees in the adjacent group, and 6% of the seeds were fertilized by pollen from trees outside these stands. The average pollination distance within the forest fragment was 83 m; when the tree group was included the pollination distance was 2006 m. The average number of effective pollen donors was estimated as 12.6. Mother-trees within the fragment could be assigned to all seedlings and juveniles, suggesting an absence of seed immigration. The distance of seedlings and juveniles from their assigned mother-trees ranged from 0.35 to 291 m (with an average of 83 m). Significant spatial genetic structure among adult trees, seedlings, and juveniles was detected up to 50 m, indicating seed dispersal over a short distance. The effective pollination neighborhood ranged from 0.4 to 3.3 ha. The results suggest that seed dispersal is restricted but that there is long-distance pollen dispersal between the forest fragment and the tree group; thus, the two stands of trees are not isolated.     

Extensive pollen dispersal in a bird-pollinated shrub, Calothamnus quadrifidus, in a fragmented landscape

Pollen dispersal was investigated in six populations of Calothamnus quadrifidus, a bird-pollinated shrub in the fragmented agricultural region of southern Western Australia. Paternity analysis using six microsatellite loci identified a pollen source within populations for 67% of seedlings, and the remainder were assumed to have arisen from pollen sources outside the populations. Outcrossing was variable, ranging from 5% to 82%, and long-distance pollen dispersal was observed in all populations with up to 43% of pollen sourced from outside the populations over distances of up to 5 km. This extensive pollen immigration was positively associated with population size but not isolation. Comparison of two populations of similar size but different density showed greater internal pollination and less selfing in the denser population, suggesting an influence of density on pollinator behaviour. The study revealed extensive long-distance pollen dispersal for C. quadrifidus within this fragmented agricultural landscape and highlighted the interaction between reserve populations and isolated road verge remnants in maintaining genetic connectivity at the landscape scale.     

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

Background and Aims 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.Methods 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.Key Results 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.Conclusions 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.     

Genetic Connectivity of the Moth Pollinated Tree Glionnetia sericea in a Highly Fragmented Habitat

Long-distance gene flow is thought to be one prerequisite for the persistence of plant species in fragmented environments. Human influences have led to severe fragmentation of native habitats in the Seychelles islands, with many species surviving only in small and isolated populations. The endangered Seychelles endemic tree Glionnetia sericea is restricted to altitudes between 450 m and 900 m where the native forest vegetation has been largely lost and replaced with exotic invasives over the last 200 years. This study explores the genetic and ecological consequences of population fragmentation in this species by analysing patterns of genetic diversity in a sample of adults, juveniles and seeds, and by using controlled pollination experiments. Our results show no decrease in genetic diversity and no increase in genetic structuring from adult to juvenile cohorts. Despite significant inbreeding in some populations, there is no evidence of higher inbreeding in juvenile cohorts relative to adults. A Bayesian structure analysis and a tentative paternity analysis indicate extensive historical and contemporary gene flow among remnant populations. Pollination experiments and a paternity analysis show that Glionnetia sericea is self-compatible. Nevertheless, outcrossing is present with 7% of mating events resulting from pollen transfer between populations. Artificial pollination provided no evidence for pollen limitation in isolated populations. The highly mobile and specialized hawkmoth pollinators (Agrius convolvuli and Cenophodes tamsi; Sphingidae) appear to promote extensive gene flow, thus mitigating the potential negative ecological and genetic effects of habitat fragmentation in this species. We conclude that contemporary gene flow is sufficient to maintain genetic connectivity in this rare and restricted Seychelles endemic, in contrast to other island endemic tree species with limited contemporary gene flow.     

Does long‐distance pollen dispersal preclude inbreeding in tropical trees? Fragmentation genetics of Dysoxylum malabaricum in an agro‐forest landscape

Tropical trees often display long‐distance pollen dispersal, even in highly fragmented landscapes. Understanding how patterns of spatial isolation influence pollen dispersal and interact with background patterns of fine‐scale spatial genetic structure (FSGS) is critical for evaluating the genetic consequences of habitat fragmentation. In the endangered tropical timber tree Dysoxylum malabaricum (Meliaceae), we apply eleven microsatellite markers with paternity and parentage analysis to directly estimate historic gene flow and contemporary pollen dispersal across a large area (216 km²) in a highly fragmented agro‐forest landscape. A comparison of genetic diversity and genetic structure in adult and juvenile life stages indicates an increase in differentiation and FSGS over time. Paternity analysis and parentage analysis demonstrate high genetic connectivity across the landscape by pollen dispersal. A comparison between mother trees in forest patches with low and high densities of adult trees shows that the frequency of short‐distance mating increases, as does average kinship among mates in low‐density stands. This indicates that there are potentially negative genetic consequences of low population density associated with forest fragmentation. Single isolated trees, in contrast, frequently receive heterogeneous pollen from distances exceeding 5 km. We discuss the processes leading to the observed patterns of pollen dispersal and the implications of this for conservation management of D. malabaricum and tropical trees more generally.     

Reduced density due to logging and its consequences on mating system and pollen flow in the African mahogany Entandrophragma cylindricum

In tropical forests, selective logging removes large trees that are often the main contributors to pollination. We studied pollination patterns of the African mahogany, Entandrophragma cylindricum (Sapelli). We investigated two plots in Cameroon corresponding to three tree densities: unlogged forest (Ndama 2002), a mildly logged forest 1 year after logging (Ndama 2003) and a severely logged forest 30 years after logging (Dimako). We used four microsatellite markers to perform paternity analysis. Selfing remained below 2% in all treatments. Pollen flow was mainly long distance but with some proximity effects. Average observed within-plot pollination distances were 338, 266 and 385 m, and pollination by trees outside the plots was 70% (Ndama 2002), 74% (Ndama 2003) and 66% (Dimako). Despite sampling a limited number of seeds from a limited number of mother trees, we obtained seeds sired by 35.6-38.3% of the potential within-plot pollen donors. While trees 20 cm in diameter contributed to pollination, results in Dimako suggest that individual larger trees contribute more to pollination than small ones. This effect was not detected in the other treatments. The results suggest extensive pollen flow in Sapelli. Hence, in Sapelli, the main limiting factor for regeneration after logging may be a reduction in the number of trees capable of producing seeds rather genetic effects due to limits to pollen dispersal.     

Pollinator-mediated competition between two congeners, Limnanthes douglasii subsp. rosea and L. alba (Limnanthaceae)

? Premise of Study: Pollinator visits are essential for reproduction in many plants, yet interspecific movements of pollinators can also lead to competitive interactions between coflowering species. Pollination-mediated reductions in fertility could potentially lead to exclusion of competing plant species, and may generate spatial variation in the associations among coflowering species across a landscape. ? Methods: I documented the potential for heterospecific pollen transfer to cause competitive interactions between two annual grassland species native to California, Limnanthes douglasii subsp. rosea and L. alba, two reproductively incompatible species that have broadly overlapping geographic ranges in the foothills of the Sierra Nevada. I observed pollinator movement in constructed arrays and controlled crosses in the greenhouse and field to investigate the consequences of heterospecific pollen transfer. ? Key Results: Pollinators move readily between species when they are presented together in experimental arrays. In the greenhouse, deposition of heterospecific pollen decreased fertility in both species. The decrease in seeds produced per flower was much more pronounced in L. d. rosea (90.6% reduction) than in L. alba (40.8% reduction). In field experiments, L. d. rosea plants that received pollen from heterospecific neighbors first showed >50% reduction in per-flower fertility. ? Conclusions: Under natural pollination conditions, heterospecific pollen transfer has the ability to decrease the fertility of L. d. rosea when it occurs at low frequency in mixed stands. Accordingly, pollinator-mediated competition may contribute to the locally disjunct distributions of these two species. It may also influence important restoration decisions in vernal pool habitats.     

Does restored plant diversity play a role in the reproductive functionality of Banksia populations?

Vegetation structure and plant species diversity of restoration sites are predicted to directly affect pollinator attraction, with potential impacts on gene flow, reproduction, genetic diversity of future generations, and ultimately restoration success. We compared Banksia attenuata R.Br. (Proteaceae) in a low species diversity restoration site and an adjacent natural remnant. We assessed fecundity genetic diversity in adult plants and their offspring, mating system parameters and pollen dispersal using paternity assignment. Results were compared to an earlier study of reproductive functionality within a high species diversity restoration site that was restored in a similar manner, enabling us to investigate any association between plant species diversity and fecundity. Seed set data indicated no significant differences between restored and adjacent natural sites; however, seed set data between restoration sites was significantly different (2.08 ± 0.39 and 6.89 ± 1.12, respectively). The mean number of fruits (follicles) per inflorescence was not significantly different between restoration sites. Genetic diversity of adult plants and their offspring were comparable in all sites. Higher allelic richness and genetic differentiation in one restored site reflected sourcing beyond local provenance. Low correlated paternity indicated high levels of multiple siring of seeds and paternity assignment demonstrated strong genetic connectivity between sites. Reproductive functionality, as measured by fecundity and genetic diversity in the offspring of B. attenuata, is resilient to low species diversity within a restored plant community. We consider our results in the context of establishing seed production areas (SPAs) that maximize the quantity and genetic quality of Banksia seeds for restoration.     

Do differences in plant and flower age change mating patterns and alter offspring fitness in Raphanus sativus (Brassicaceae)?

When more pollen is present on stigmas than needed to fertilize all ovules, selection among pollen grains may occur due to effects of both pollen donors and maternal plants. We asked whether increasing plant age and flower age, two changes in maternal condition, altered the pattern of seed paternity after mixed pollination. We also asked whether changes in seed paternity affected offspring success in an experimental garden. While flower age did not affect seed paternity, there was a dramatic shift in pollen donor performance as plants aged. These differences were seen in the offspring as well, where the offspring of one pollen donor, which sired more seeds on young plants, flowered earlier in the season, and the offspring of another pollen donor, which sired more seeds on old plants, flowered later in the season. Thus, change in maternal condition resulted in altered seed paternity, perhaps because the environment for pollen tube growth was different. The pattern of seed paternity and offspring performance suggests that pollen donors may show temporal specialization.     

How robust is nonrandom mating in wild radish: do small pollen loads coupled with more competing pollen donors lead to random mating?

In previous studies of the weedy annual Raphanus sativus we have demonstrated that mating is nonrandom in greenhouse plants, suggesting that sexual selection is possible. To investigate how these greenhouse results might translate to conditions more similar to the field, we manipulated both pollen load size and the number of competing pollen donors on stigmas. While the smallest pollen loads (22 grains per stigma) were small enough to reduce fruit and seed set, seed siring success was unaffected by pollen load size. When the number of competing donors in a mixed pollination was increased to four, the proportion of seeds sired by the pollen donors was the furthest from expectation, suggesting that nonrandom mating increases as the number of donors per pollination increases. There was no significant interaction between pollen load size and number of competitors per pollination. Overall, mating remained nonrandom across all treatments. Thus differential seed paternity is likely to occur in the field as well as in the greenhouse.     

Outcrossing between an agroforestry plantation and remnant native populations of Eucalyptus loxophleba

Gene dispersal among populations of a species is an important force influencing their genetic structure. Dispersal may also occur between taxa that would normally be isolated when nonendemic, domesticated or transgenic species are planted within the natural range of interfertile taxa. Such a mosaic of populations is typical of many agricultural landscapes, and investigations are needed to assess the risks of genetic contamination of the endemic populations but a combination of approaches may be necessary because of the limitations of research in this landscape. This study used microsatellite markers and a range of analyses (mating system, paternity exclusion, Bayesian assignment) to examine gene dispersal between remnants of the endemic Eucalyptus loxophleba ssp. supralaevis and a plantation of a nonendemic subspecies. Our results indicate that remnant populations are connected by significant dispersal to pollen sources up to 1.94 km away including the plantation. The combined analyses showed that the pollen pool and outcrossing rates of individuals within remnants varied significantly probably because of asynchronous flowering and that the likelihood of paternity was not correlated with spatial proximity. More than half of all progeny had male parents from outside their stand with the largest proportions estimated to come from the plantation by exclusion (42.4%) or Bayesian analyses (18.8–76%). Fragmentation may not be associated with decreased gene dispersal between populations of tree species, natural or planted, so that the distances required to buffer endemic trees in fragmented rural landscapes are likely to be large.     

Genetic variation among females affects paternity in a dioecious plant

Flowering plants rely on vectors for pollen transfer, and cannot choose their mates. Although recipient plants are unable to choose which pollen they receive, post‐pollination selection (acting pre‐ or post‐zygotically) may modify the outcome of pollination. Here we show that genetic variation among pollen recipients can predict the outcome of pollen competition (seed paternity) in the dioecious white campion. To investigate whether genetic variation among pollen recipients affects paternity, we applied the same pollen mixture from two males to three females, two of which full sisters and the third one chosen at random (unrelated). To control for maternal environmental effects, the plants used for these crosses were greenhouse‐reared F₁. We replicated this in two populations, for a total of 51 crosses, and genotyped a total of 772 offspring to assign paternity. If genetic variation affects paternity, we expected greater similarity of paternity success of the focal male with the sisters, compared to the unrelated female. Paternity of the focal male was significantly more repeatable over sisters, compared to repeatability over the mean of sisters and the unrelated females. When populations were analyzed separately, this was significant in one of the two populations. Paternity was not significantly correlated with stigma size. This provides evidence that in at least one population, genetic variation among individual plants influences the donors’ paternity success, as assessed through genetic analysis of the seedling. Since due to gravity‐dispersed seeds natural patches may often consist of related plants, the observed effect may contribute to variation in male reproductive success.     

Mating dynamics of Scots pine in isolation tents

Seed orchards are forest tree production populations for supplying the forest industry with consistent and abundant seed crops of superior genetic quality. However, genetic quality can be severely affected by non-random mating among parents and the occurrence of background pollination. This study analyzed mating structure and background pollination in six large isolation tents established in a clonal Scots pine seed orchard in northern Sweden. The isolation tents were intended to form a physical barrier against background pollen and induce earlier flowering relative to the surrounding trees. We scored flowering phenology inside and outside the tents and tracked airborne pollen density inside and outside the seed orchard in three consecutive pollination seasons. We genotyped 5683 offspring collected from the tents and open controls using nine microsatellite loci, and assigned paternity using simple exclusion method. We found that tent trees shed pollen and exhibited maximum female receptivity approximately 1 week earlier than trees in open control. The majority of matings in tents (78.3 %) occurred at distances within two trees apart (about 5 m). Self-fertilization was relatively high (average 21.8 %) in tents without supplemental pollination (SP), but it was substantially reduced in tents with SP (average 7.7 %). Pollen contamination was low in open controls (4.8–7.1 %), and all tents remained entirely free of foreign pollen. Our study demonstrates that tent isolation is effective in blocking pollen immigration and in manipulating flowering phenology. When complimented with supplemental pollination, it could become a useful seed orchard management practice to optimize the gain and diversity of seed orchard crops.     

Remnant Pachira quinata pasture trees have greater opportunities to self and suffer reduced reproductive success due to inbreeding depression

Habitat fragmentation is extensive throughout the world, converting natural ecosystems into fragments of varying size, density and connectivity. The potential value of remnant trees in agricultural landscapes as seed sources and in connecting fragments has formed a fertile area of debate. This study contrasted the mating patterns of bat-pollinated Pachira quinata trees in a continuous forest to those in pasture through microsatellite-based paternity analysis of progeny. The breeding system was determined by analysis of pollen tube growth and seed production from controlled pollinations. Fitness of selfed and outcrossed seed was compared by germination and seedling growth. There was more inbreeding within pasture trees (outcrossing=0.828±0.015) compared with forest trees (0.926±0.005). Pasture trees had fewer sires contributing to mating events, but pollen dispersal distances were greater than those in the forest. Paternity analysis showed variation in outcrossing rates among pasture trees with high proportions of external and self pollen sources detected. A leaky self-incompatibility system was found, with self pollen having reduced germination on stigmas and slower growth rate through the style. Controlled pollinations also showed a varied ability to self among trees, which was reflected in the selfing rates among pasture trees shown by the paternity analysis (0–80% selfing). Self pollination resulted in lower seed set, germination and seedling growth compared with outcrossing. While remnant trees in agricultural landscapes are involved in broader mating patterns, they show increased but varied levels of inbreeding, which result in reduced fitness.