DNA Fingerprinting Validates Seed Dispersal Curves from Observational Studies in the Neotropical Legume Parkia

Background: Determining the distances over which seeds are dispersed is a crucial component for examining spatial patterns of seed dispersal and their consequences for plant reproductive success and population structure. However, following the fate of individual seeds after removal from the source tree till deposition at a distant place is generally extremely difficult. Here we provide a comparison of observationally and genetically determined seed dispersal distances and dispersal curves in a Neotropical animal-plant system. Methodology/Principal Findings: In a field study on the dispersal of seeds of three Parkia (Fabaceae) species by two Neotropical primate species, Saguinus fuscicollis and Saguinus mystax, in Peruvian Amazonia, we observationally determined dispersal distances. These dispersal distances were then validated through DNA fingerprinting, by matching DNA from the maternally derived seed coat to DNA from potential source trees. We found that dispersal distances are strongly rightskewed, and that distributions obtained through observational and genetic methods and fitted distributions do not differ significantly from each other. Conclusions/Significance: Our study showed that seed dispersal distances can be reliably estimated through observational methods when a strict criterion for inclusion of seeds is observed. Furthermore, dispersal distances produced by the two primate species indicated that these primates fulfil one of the criteria for efficient seed dispersers. Finally, our stud

Contrasting effects of long distance seed dispersal on genetic diversity during range expansion

Currently many attempts are made to reconstruct the colonization history of plant species after the last ice age. A surprising finding is that during the colonization phase genetic diversity did not decrease as much as expected. In this paper we examine whether long distance seed dispersal events could play a role in the unexpected maintenance of genetic diversity during range expansion. This study is based on simulations carried out with a maternally inherited haploid locus using a cellular automaton. The simulations reveal a close relationship between the frequency of long distance seed dispersal events and the amount of genetic diversity preserved during colonization. In particular, when the colonized region is narrow, a complete loss of genetic diversity results from the occurrence of very rare long distance dispersal (LDD) events. We call this phenomenon the 'embolism effect'. However, slightly higher rates of LDD events reverse this effect, up to the point that diversity is better preserved than in a pure diffusion model. This phenomenon is linked to the reorganization of the genetic structure during colonization and is called the 'reshuffling effect

Modelling the population fluctuation of winter moth and mottled umber moth in central and northern Germany

Abstract Background Winter moth (Operophtera brumata) and mottled umber moth (Erannis defoliaria) are forest Lepidoptera species characterized by periodic high abundance in a 7–11 year cycle. During outbreak years they cause severe defoliation in many forest stands in Europe. In order to better understand the spatio-temporal dynamics and elucidate possible influences of weather, stand and site conditions, a generalized additive mixed model was developed. The investigated data base was derived from glue band catch monitoring stands of both species in Central and North Germany. From the glue bands only female moth individuals are counted and a hazard code is calculated. The model can be employed to predict the exceedance of a warning threshold of this hazard code which indicates a potential severe defoliation of oak stands by winter moth and mottled umber in the coming spring. Results The developed model accounts for specific temporal structured effects for three large ecoregions and random effects at stand level. During variable selection the negative model effect of pest control and the positive model effects of mean daily minimum temperature in adult stage and precipitation in early pupal stage were identified. Conclusion The developed model can be used for short-term predictions of potential defoliation risk in Central and North Germany. These predictions are sensitive to weather conditions and the population dynamics. However, a future extension of the data base comprising further outbreak years would allow for deeper investigation of the temporal and regional patterns of the cyclic dynamics and their causal influences on abundance of winter moth and mottled umber

Data from: Quantification of the zygotic barrier between interbreeding taxa using gene flow data

Hybridization and introgression via interspecific gene flow are common processes in the plant kingdom. The effectiveness of these processes is governed by the strengths of multiple zygotic barriers. These barriers have often been quantified in artificial settings using laborious and time-consuming hand-pollination experiments, but their quantification is nonexistent at the landscape level. In this study, we utilized gene flow data within a spatially explicit simulation to assess the strengths of zygotic barriers. Our model system consisted of Populusnigra and its hybrid, P.×canadensis, which interbreed under natural conditions. The study population was located in the floodplain of the Eder River in Central Germany. Pollen-mediated introgression rates from hybrid males into the seeds of individual female trees were used as the target pattern using an inverse modeling approach. Simulations that treated pollen from both taxa equally revealed a large discrepancy between the observed and modeled rates of introgression for both taxa. The discrepancy was reduced by introducing a zygotic barrier against the pollen from the hybrid males. The best model outcome indicated comparably strong zygotic barriers acting against pollen-mediated introgressive gene flow into the two parental taxa, P.nigra and P.×canadensis. The sensitivity of our model was tested by applying different dispersal functions. Four common probability density functions were used along with a pollen dispersal function that had previously been fitted to gene flow data from the same dataset. The best barrier value was almost independent of the dispersal functions used here. Moreover, it was within the range previously determined in hand-pollination-based investigations, validating our model. These data indicate that the inverse modeling approach is a powerful method for quantifying hidden processes, and we discuss its use as a valuable tool for generating new insights into plant mating systems that are relevant to evolutionary biology and risk analysis in conservation effort

Ecology and genetics of tree invasions: from recent introductions to Quaternary migrations

The use of fossil sediments and genetic markers has allowed reconstruction of range shifts of forest trees induced by past climatic changes. Independently, studies of the ecology and population biology of human-induced tree invasions have started to appear. Here, we review the literature on the ecology and the genetics of past and contemporary invasions of forest trees and argue that population research dealing with past (natural) or with ongoing (human-induced) invasions should be better integrated. In particular, we suggest using identical terms to describe artificial and natural invasions, as this should help integrate the two fields. We then discuss the modalities of introduction of tree species, the life history traits associated with invasiveness, the importance of long-distance seed dispersal, the establishment of small populations, the role of biotic interactions and the specific contribution of palaeoecology to the study of tree invasions. Next, we discuss genetic and evolutionary aspects, including the genetic characteristics of invasive woody species, the genetic consequences of dispersal (founder effects and admixture), shifts in dispersal-related traits and in mating system and the importance of hybridization and introgression during invasion. We then review models of the genetic consequences of tree invasions, examine the possibility for rapid adaptation of trees to new environmental conditions and discuss the relative importance of environmental versus genetic factors in controlling tree invasions. We conclude by proposing solutions for two central “genetic paradoxes” of invasions. The first one is the necessity for invasive species to adapt to new conditions, which seems difficult to reconcile with the expected loss of diversity through founder events. The second is the common observation of invasive species outcompeting native ones, which does not seem to fit with the belief in widespread local adaptatio

Introgression data

The file was produced using the command 'save()' from the R software. This resulted in the file “introgression.RData”, which includes two dataframes: (1) intro.rates.paper and (2) tree.data. The first dataframe comprises the empirical introgression rates recorded by Bialozyt et al. (2012). The columns are the individual tree number followed by the percentage of introgression for year 2006 and 2007 respectively. The second dataframe (tree.data) comprises the name, coordinates, sex and taxa of all trees used in the simulation. In the column 'SEX' females are coded '0' and males are coded '1'. In the column 'SPECIES' Populus nigra are coded '0' and the hybrids (Populus × canadenis) are coded '1'

Distribution patterns of plants explained by human movement behaviour

Distribution patterns of plants are affected by human activities such as creation, destruction or modification of habitats. However, another important question is to what extent humans shape plant distributions by acting as dispersal vectors. In order to answer this question we developed a simulation model for the spread of plant species between human settlements. This was done on the basis of extensive sociological and ecological data on a regional scale. With regard to the sociological data, human movement behaviour defined the amount of exchange between the settlements. Gardening types represented the potential habitat in our model. The ecological data was derived from a vegetation survey carried out in 2003, which was a repeat of a survey between 1974 and 1981 along the same transects. From these surveys, we studied the distributions of 13 species in 67 settlements. In our model, the earlier survey provided the data for the initial distribution. The simulated pattern was consequently compared with the distribution pattern in 2003. In the model, dispersal kernels based on patterns of human movement between settlements led to a better match with the distribution patterns than a null model simulating pure distance dependent dispersal for all species. This was statistically significant for seven of the thirteen species. A striking result was that alien species seem to benefit more from human dispersal than native species. We emphasize the importance of the sociological data on human movement behaviour in parameterizing our regional scale model. This study provides quantitative evidence on the impact of human movement behaviour on the distribution of plant species in suburban areas

Distribution fitting to the dispersal distance distributions obtained with observational (A) and genetic methods (B).

<p>Fitted distributions do not differ between genetically and observationally obtained dispersal distance distributions.</p

Examples of electrofluorograms showing the comparison between tissue from the mother tree and from seed coats for markers Parpan 4 and Parpan 5.

<p>x-axis: fragment length (number of bases), y-axis: signal intensity. In all cases the diploid heterozygous genotypes exhibit more than just two peaks. This is due to stuttering which is common. The true allele is the one with the highest signal intensity.</p

Number of seeds assigned to source trees and mean dispersal distances per source tree.

<p>Number of seeds assigned to source trees and mean dispersal distances per source tree.</p