Neighborhood aggregation effect and its effective scale on reproductive success in Shorea laxa (Dipterocarpaceae)

Abstract

This study investigated whether reproductive success is affected by the intensity of neighborhood aggregation of adults in the tropical tree Shorea laxa. We focused on three processes in the early reproductive stages: seed maturation; seed survival (categorizing sound seed, predation by insects and predation by vertebrates) in pre-seed dispersal; and seedling survival in the post-seed dispersal stage. We used a model selection procedure to examine the aggregation effect on reproductive success. The intensity of neighborhood aggregation was represented by the neighborhood aggregation index, which contains the adult number within a specific radius and the distances to neighboring adults (weight of proximity). Then, we evaluated the models exhaustively with the aggregation index having different scales (radius and weight of proximity) to assess the scale on which aggregation had significant effects. In particular, the best effective neighborhood scale, which is defined as the scale of the index in the model with minimum Akaike information criterion, was examined to compare those scales among processes. We found that the probability of seed maturation, seed survival and seedling survival decreased with the aggregation index at specific scales. This suggests that aggregation influenced reproductive success negatively in both the pre- and post-seed dispersal stages. However, the selected radii differed among processes: >200 and 130 m in pre- and post-seed dispersal stages, respectively. The selected weight of proximity also seemed to have a weak effect on all processes and was not different among processes.

Genetic consequences of subtropical rainforest fragmentation onMacadamia tetraphylla(Proteaceae)

“…If dense populations have a high degree of genetic structuring, which seems likely, then the progeny of these trees are more likely to be inbred. This has been found to be the case for other rainforest trees (TAKEUCHI, 2010) as well as in herbaceous species (KITA-MOTO et al, 2007). There may also be an interaction with pollinator behaviour, which is apparently influenced by interflowering-tree density (BAWA, 1998).…”

Molecular and quantitative signatures of biparental inbreeding depression in the self-incompatible tree species Prunus avium

“…Isolation of this P. avium population may have thus resulted in loss of genetic diversity and homozygote excess in seed and seedlings, as a consequence of low pollen immigration (Hanson et al, 2008;Sebbenn et al, 2010), significant spatial genetic structure (see Supplementary File 3; We analysed eight nuclear microsatellite loci and the gametophytic incompatibility locus. Waser and Price, 1994;Isagi et al, 2007;Grindeland, 2008;Hasegawa et al, 2009;Takeuchi et al, 2010), inbreeding (see Supplementary Material 1) or generation overlapping (Litrico et al, 2005). Seed sampling and seed germination resulted in loss of genetic diversity in the stand Bayern only.…”

Rare events of massive plant reproductive investment lead to long‐term density‐dependent reproductive success

“…Takeuchi et al. () found that aggregation of Shorea laxa (Dipterocarpaceae) influenced PRS negatively in both the pre‐ and post‐dispersal stages. Positive density‐dependent effects of reproductive output are also common (Aizen & Harder, ; House, ; Jones & Comita, , ; Mezquida & Olano, ).…”

“…For example, high density or aggregation of flowering plants can increase crop size by attracting more pollinators or by satiating flower and seed predators (see Aizen & Harder, ; Ghazoul, ; Mezquida & Olano, ). However, high density of conspecifics can also decrease reproductive success by boosting intraspecific competition for resources or pollinators (Gunton & Kunin, ; Mustajärvi et al., ), or by attracting more seed predators or pathogens (Jones & Comita, ; Takeuchi, Samejima, Nakagawa, Diway, & Nakashizuka, ). Interestingly, the amount of plant reproductive investment (e.g.…”