Effects of pollen quantity and quality on reproduction and offspring vigor in the rare plant Scorzonera humilis (Asteraceae)

Abstract

We studied the effects of pollinator exclusion, interparental distance, and supplementary hand pollination on reproduction and progeny vigor in Scorzonera humilis (Asteraceae), a rare plant of fragmented, nutrient-poor grasslands. Caged flowers produced no seeds and selfed flowers only very rarely, indicating that S. humilis is mainly self-incompatible. Seed production, seed mass, and seed germination following between-population crosses were consistently, but not significantly, higher than after within-population crosses. Seed set increased with local density of conspecifics, indicating that the reduced plant density in fragmented populations may reduce plant reproductive success. Seed set was pollen limited in all four populations studied. Supplementary hand-pollination strongly increased the survival of offspring, indicating that either pollinators transferred pollen from related individuals resulting in inbreeding depression in spite of the incompatibility system or that higher pollen loads increased pollen competition and the selectivity among gametes. In one of the populations, adding pollen from a different population strongly increased progeny fitness compared with both natural pollination and pollen supplementation from the same population. The results indicate that S. humilis is sensitive to inbreeding and that pollen limitation can reduce both the number and quality of offspring.

Abnormalities in sexual development and pollinator limitation in Michelia coriacea (Magnoliaceae), a critically endangered endemic to Southeast Yunnan, China

“…It is well known that plants rely on vectors transferring pollen to their stigmas for fertilization. It could be that in fragmented populations plant-pollinator interactions may become disrupted and reproduction may be reduced because of insufficient pollination (AEgisdó ttir et al, 2007;Chacoff et al, 2008;Colling et al, 2004;Kearns et al, 1998;Moody-Weis and Heywood, 2001). Plants in small populations are often less attractive to pollinators and may be visited less frequently (Rathcke and Jules, 1993).…”

“…Pollen quantity and quality as well as abnormal gametic development can often result in limited seed production and subsequent population decline and eventual extinction. The study of plant species with low reproductive capabilities has been the subject of much recent research and has become an important aspect in plant conservation (Byers, 2004;Colling et al, 2004;Evans et al, 2004;Hedrick and Kalinowski, 2000;Pan et al, 2003;Rocha and Aguilar, 2001). In addition, self pollen can limit seed production through inbreeding depression (Bosch and Waser, 1999;Brown and Kephart, 1999).…”

Interaction frequency and per-interaction effects as predictors of total effects in plant–pollinator mutualisms: a case study with the self-incompatible herb Linaria lilacina

“…In plant-pollinator mutualistic interactions, both components may have a significant influence on the outcome of plant-pollinator interactions in terms of reproductive or demographic success of the interacting species (e.g. Herrera 1987Herrera , 1989Colling et al 2004;Aizen and Harder 2007). The need to take into account both the Communicated by Rebecca Irwin.…”

“…Wilson and Thomson 1991, Wilson 1995, Robertson et al 2005; and (2) the composition of the pollen mixture delivered by those pollinator groups (most relevant in self-incompatible species, or in self-compatible ones with high levels of inbreeding depression; e.g. Ivey et al 2003, Colling et al 2004Williams 2007). This variation in perinteraction effect is the result of pollinator foraging strategies and is strongly affected by the pollination environment (i.e.…”

Population structures and individual performances of Trillium grandiflorum in hedgerow and forest habitats

“…For hedgerows to act as efficient dispersal corridors, they would need to support persistent populations of forest herbs that can produce dispersing propagules for the gradual movement of species across landscapes. Hedgerow populations, however, appear more vulnerable than forest populations because of their small size and sparse distribution which can increase extinction risk due to genetic and environmental stochasticity (Newman and Pilson 1997) and reduce seed production and recruitment by influencing pollination (Groom 1998;Sih and Baltus 1987), mate availability (Wagenius et al 2007), or progeny fitness (Colling et al 2004). These risks are further enhanced by edge effects that alter habitat quality (Harrison and Bruna 1999) due to changes in microclimatic conditions (Chen et al 1995(Chen et al , 1999Matlack 1993), soil chemistry (Honnay et al 2002;Weathers et al 2001), or biotic interactions (Jules and Rathcke 1999).…”