Evaluating contemporary pollen dispersal in two common grassland species Ranunculus bulbosus L. (Ranunculaceae) and Trifolium montanum L. (Fabaceae) using an experimental approach

Abstract

Pollen flow is a key biological process that connects plant populations, preventing genetic impoverishment and inbreeding. Pollen-mediated long-distance dispersal (LDD) events are especially important for plant species in increasingly fragmented landscapes. Patterns of pollen dispersal were directly estimated and dispersal kernels modelled in an experimental population of Ranunculus bulbosus and Trifolium montanum to determine the potential for LDD. Eight and 11 microsatellite markers were used for R. bulbosus and T. montanum, respectively, to run a likelihood-based paternity analysis on randomly chosen offspring (Ntotal = 180 per species) from five maternal plants. High rates of selfing were found in R. bulbosus (average 45.7%), while no selfing was observed in T. montanum. The majority (60%) of mating events occurred at very short distances: the median of the observed dispersal distances was 0.8 m in both species, and the average distances were 15.9 and 10.3 m in R. bulbosus and T. montanum, respectively. Modelling the pollen dispersal kernel with four different distribution functions (exponential-power, geometric, 2Dt and Weibull) indicated that the best fit for both species was given by a Weibull function. Yet, the tail of the T. montanum pollen dispersal kernel was thinner than in R. bulbosus, suggesting that the probability for LDD is higher in the latter species. Even though the majority of pollen dispersal occurred across short distances, the detection of several mating events up to 362 m (R. bulbosus) and 324 m (T. montanum) suggests that pollen flow may be sufficient to ensure population connectivity in these herb species across fragmented grasslands in Swiss agricultural landscapes.

Florally rich habitats reduce insect pollination and the reproductive success of isolated plants

“…This pattern is consistent with a wealth of research indicating that although capable of travelling large distances (Hagler, Mueller, Teuber, Machtley, & Van Deynze, 2011), pollinators predominantly travel considerably shorter distances (Rader et al, 2011), remaining in localized resource patches (Pasquet et al, 2008). This results in a distance decay distribution of pollen movement (Matter, Kettle, Ghazoul, Hahn, & Pluess, 2013), suggesting that between block movement (>500 m) in this experiment would be minimal. In spatially genetically structured plant populations, reduced long-distance pollination events, particularly in florally rich habitats, will result in a higher frequency of mating between close relatives.…”

Effects of forest fragmentation on the mating system of a cool-temperate heterodichogamous tree Acer mono

“…Although a similar pattern had been reported from anemophilous and entomophilous plants (e.g., Albaladejo et al, 2012;Goto et al, 2006;Matter et al, 2013;Nakanishi et al, 2012;Robledo-Arnuncio and Gil, 2005), our results suggested a highly leptokurtic distribution compared with other entomophilous genera such as pollen dispersal in A. mono, which implies that a considerable amount of long-distance dispersal occurred whereas shortdistance pollen transfer predominated might be attributable to a wide variety of the pollinator fauna. Although the visitors to A. mono flowers, such as small insects such as flies, hover flies and solitary bees are generally habitat-dependent and have narrow foraging ranges (Steffan-Dewenter et al, 2002), occasional visits by honey bees ) might contribute to long-distance pollen dispersal because they have a large foraging range (Visscher and Seeley, 1982).…”

Paternity analysis, pollen flow, and spatial genetic structure of a natural population ofEuterpe precatoriain the Brazilian Amazon

“…The tail shape of the dispersal kernel (i.e., whether thin-or fat-tailed) affects the ultimate distribution of genetic diversity within and between populations. Some studies report that pollen dispersal kernels are fat-tailed in tree species (Austerlitz et al, 2004;Klein, Lavigne, & Gouyon, 2006;Matter, Kettle, Ghazoul, Hahn, & Pluess, 2013;Ramos, Dequigiovanni, Sebbenn et al, 2016;Saro et al, 2014).…”