Effects of local conspecific abundance on seed set and seed predation, and control of Carpinus laxiflora (Betulaceae) population density

Abstract

In this study, the dependence of local conspecific abundance on seed set and predation was examined, and determinates of population density of the temperate tree species Carpinus laxiflora (Betulaceae) in Inagi city, Tokyo, Japan were identified. During a good seed year (2013), seeds were sampled from 27 individuals and categorized as Sound, Empty, Predated, Immature, Decayed, or Broken. Empty seeds were identified as those that failed to fertilize and predation rates were defined as the proportion of seeds that were affected by predators. The proportion of the seed set that was fertilized was significantly positively correlated with local abundance of conspecific trees, while the proportion of seeds that escaped predation was significantly negatively correlated with local abundance of conspecific trees. Thereby, the production of Sound seeds was highest at sites with moderate local conspecific abundance. Although this phenomenon was only observed in a few cases, it clearly showed optimal reproductive success under conditions of moderate density of conspecific reproductive adults, suggesting a mechanism that controls the population density of this species.

NTFP harvesters as citizen scientists: Validating traditional and crowdsourced knowledge on seed production of Brazil nut trees in the Peruvian Amazon

“…This is called the “Allee” effect [ 26 ] and is related with effects of pollen limitation and increased selfing rates in more isolated trees [ 27 ]. It has been described for numerous tree species [ 28 , 29 ], particularly in predominantly outcrossing ones such as Brazil nut [ 30 ]. However, this effect only applied to Brazil nut trees growing at nearest conspecific distances higher than 100 m, whereas trees growing at very short distances of conspecific neighbours tended to yield slightly lower production estimates than trees at intermediate distances ( Fig 6 ).…”

Pollen dispersal patterns differ among sites for a wind‐pollinated species and an insect‐pollinated species

“…For example, urban sites may differ in active management (e.g., mowing, weeding, planting; Strausz et al, 2012;Madre et al, 2014), and, thus, vegetation composition and cover within and surrounding the sites would be expected to differ. Pollen dispersal and fertilization may be positively affected if there is an increased number of conspecifics nearby (Allison, 1990;Katori and Nakashizuka, 2015) or negatively affected if there is increased competition from heterospecific pollen (Campbell, 1985;Vamosi et al, 2006). Additionally, sites may differ in microclimatic variables, such as air temperature or wind intensity.…”

“…However, Walker et al (2009) showed a decrease in plant species richness with increasing urbanization. These microclimatic differences are important to consider because pollen dispersal in both wind-and insect-pollinated species can be affected by wind (Okubo and Levin, 1989;Vicens and Bosch, 2000;Damialis et al, 2005), temperature (Kuparinen et al, 2009;de la Cruz et al, 2010;Scaven and Rafferty, 2013), and the surrounding vegetation (Vamosi et al, 2006;Katori and Nakashizuka, 2015). Wind-pollination inherently increases with increasing wind persistence and speed (Damialis et al, 2005), but also increases with increasing air temperature (Kuparinen et al, 2009).…”