Abundance matters: a field experiment testing the more individuals hypothesis for richness–productivity relationships

Abstract

The more individuals hypothesis (MIH) postulates that productivity increases species richness by increasing mean equilibrium population size, thereby reducing the probability of local extinction. We tested the MIH for invertebrates colonizing microcosms that simulated tree holes by manipulating productivity through additions of leaf or animal detritus and subsequently determining the relationships among richness, total abundance, abundance per species, and measures of productivity. We quantified productivity as the rate of microorganism protein synthesis, microorganism metabolic rate, nutrient ion concentration, and type and amount of detritus. Microcosms with animal detritus attracted more species, more individuals per species, and more total individuals than did microcosms with similar amounts of leaf detritus. Relationships between richness or abundance and productivity varied with date. Richness in June increased as a linear function of productivity, whereas the power function predicted by the MIH fit best in July. Abundance in June and July was best described by a power function of productivity, but the linear function predicted by the MIH fit best in September. Abundance per species was best described by a power function of productivity in June and July. Path analysis showed that the indirect effect of productivity through abundance on richness that is predicted by MIH was important in all months, and that direct links between productivity and richness were unnecessary. Our results support many of the predictions of the MIH, but they also suggest that the effects of abundance on richness may be more complex than expected.

Flood disturbance and predator–prey effects on regional gradients in species diversity

“…The processes underlying the variations in taxonomic richness of collector-filterers and collector-gatherers/ shredders through their own community densities are consistent with the ''more individuals'' hypothesis (Srivastava andLawton 1998, Yee andJuliano 2007). This hypothesis postulates that greater productivity supports higher population densities, which lower the extinction rates of rare species, i.e., more individuals give rise to a greater number of species by enhancing the persistence of rare species (Srivastava andLawton 1998, Mori et al 2010).…”

“…Dissolved nitrogen can enhance the growth of microbes that colonize BPOM (Gulis et al 2004), resulting in high-quality BPOM (e.g., Cross et al 2006). A high quantity and quality of food resources may have the same function as high productivity (Yee and Juliano 2007), and thus promote an increase in community density, leading to an increase in taxonomic richness. Disturbance can play a similar role to productivity in terms of influencing population densities; flood disturbance depresses the growth of community density, resulting in a decrease in species richness (Mori et al 2010).…”

“…5). The first process, which worked from collector-gatherers/shredders to predators, can be interpreted by the more individuals hypothesis (Srivastava andLawton 1998, Yee andJuliano 2007), as it is for collector-gatherers/shredders and collectorfilterers. Collector-gatherers/shredders are food resources for predators, and the total biomass of collectorgatherers/shredders increased with their community density.…”

Nestedness patterns of container-dwelling mosquitoes: effects of larval habitat within variable terrestrial matrices

“…Mosquito larval survival and development time and adult size are affected strongly by the addition of detritus, including senescent plant material (Fish & Carpenter, 1982;Lé onard & Juliano, 1995;Lounibos et al, 1993;Walker et al, 1997) and animal detritus (Daugherty et al, 2000;Yee & Juliano, 2006). Richness and abundance of colonizing invertebrates also is affected by detritus type and amount (Yee & Juliano, 2007). Adult females may maximize their reproductive success by ovipositing in high quality larval habitats (Mayhew, 2001;Scheirs & De Bruyn, 2002), responding to a variety of cues directly related to the larval environment, including olfactory (e.g., volatiles from the aquatic habitat or larvae), tactile (e.g., container surfaces), and visual (e.g., color) cues (reviewed in Bentley & Day, 1989;Clements, 1999).…”

Relation entre facteurs environnementaux et densités larvaires d’Ochlerotatus caspiusPallas 1771 etOchlerotatus detritusHaliday 1833 (Diptera: Culicidae) en Tunisie

“…caspius pour les milieux aquatiques les plus basiques (fi g. 5) est également démontrée par Yee & Juliano (2007) ainsi que Zalizniak et al (2006) Ochlerotatus detritus est observé dans les biotopes les plus riches en S. fruticosa. Il semblerait que son attraction vers les milieux fortement salés, confi rmée dans cette étude et démontrée auparavant par Service (1968), soit à l'origine de l'association d'Oc.…”