8 research outputs found
Debris discs in the 27 Myr old open cluster IC4665
We present Spitzer IRAC and MIPS 24um imaging of members of the 27+/-5Myr old
open cluster IC 4665. Models for the assembly of terrestrial planets through
planetesimal collisions and mergers predict episodic dust debris discs at this
epoch. We determine that 42(+18-13)% of the solar-type (F5-K5) cluster members
have excess emission at 24um indicative of these debris discs, the highest
frequency of the clusters studied with Spitzer to date. The majority of these
discs have intermediate levels of excess (F_24/F_phot < 2), and no source is
found to have extreme levels of excess indicative of a recent transient event
as opposed to steady-state collisional evolution. We find no evidence of a link
between multiplicity and 24um excess in this cluster sample. Only the
early-type star TYC424-473-1 (T_eff~8420K) has significant near-infrared excess
from 4.5um as measured with IRAC. Two solar-type targets have low significance
8um excess but no significant 24um excess. All other targets show no evidence
for near-infrared excess which could indicate the presence of an optically
thick primordial disc, demonstrating that the observed 24um excess arises from
a debris disc.Comment: 14 pages, 11 figures, accepted for publication in MNRA
Niche partitioning due to adaptive foraging reverses effects of nestedness and connectance on pollination network stability
Much research debates whether properties of ecological networks such as nestedness and connectance stabilise biological communities while ignoring key behavioural aspects of organisms within these networks. Here, we computationally assess how adaptive foraging (AF) behaviour interacts with network architecture to determine the stability of plant-pollinator networks. We find that AF reverses negative effects of nestedness and positive effects of connectance on the stability of the networks by partitioning the niches among species within guilds. This behaviour enables generalist pollinators to preferentially forage on the most specialised of their plant partners which increases the pollination services to specialist plants and cedes the resources of generalist plants to specialist pollinators. We corroborate these behavioural preferences with intensive field observations of bee foraging. Our results show that incorporating key organismal behaviours with well-known biological mechanisms such as consumer-resource interactions into the analysis of ecological networks may greatly improve our understanding of complex ecosystems.University of Arizona, US NSF, Rocky Mountain Biological Laboratory, Emory University, University of California, Santa Cruz, FONDECYT, Chilean CONICYT doctoral fellowshi