Species–energy relationships and habitat complexity in bird communities

Abstract

Species-energy theory is a commonly invoked theory predicting a positive relationship between species richness and available energy. The More Individuals Hypothesis (MIH) attempts to explain this pattern, and assumes that areas with greater food resources support more individuals, and that communities with more individuals include more species. Using a large dataset for North American birds, I tested these predictions of the MIH, and also examined the effect of habitat complexity on community structure. I found qualitative support for the relationships predicted by the MIH, however, the MIH alone was inadequate for fully explaining richness patterns. Communities in more productive sites had more individuals, but they also had more even relative abundance distributions such that a given number of individuals yielded a greater number of species. Richness and evenness were also higher in structurally complex forests compared to structurally more simple grasslands when controlling for available energy.

Environmental correlates of avian diversity in lowland Panama rain forests

“…Not surprisingly, avian diversity along the Panama Canal showed a response to plant species richness, probably because of associated higher vegetation complexity, higher arthropod diversity and diversity of ecological niches (MacArthur et al, 1962;MacArthur, 1964;Terborgh & Weske, 1969;Ricklefs & Schluter, 1993;Siemann et al, 1998;Gillespie & Walter, 2001;Waltert et al, 2003Waltert et al, , 2005Hurlbert, 2004;Tews et al, 2004). Higher rainfall, relating to higher plant diversity in the Panama Canal region, can be a good indicator of ecosystems with a higher productivity (Kaspari et al, 2000;Clark et al, 2001;Hawkins et al, 2003Hawkins et al, , 2005Santiago & Mulkey, 2005).…”

“…Specific examples include the increase in plant and bird diversity with variation in mean annual rainfall (Gentry, 1982;Cueto & Lopez de Casenave, 1999;Gillespie & Walter, 2001;Hawkins et al, 2005;Schnitzer, 2005), topographic complexity and variability of elevation (Kerr & Packer, 1997;Kerr et al, 2001;Rahbek & Graves, 2001). Many potential explanations for diversity gradients have been proposed, including speciesenergy relationships (Hurlbert & Haskell, 2003;Hurlbert, 2004), habitat heterogeneity-animal species diversity relationships (Kerr & Packer, 1997;Tews et al, 2004) and historical factors (Ricklefs & Schluter, 1993;Ricklefs, 2004;Hawkins et al, 2006). Few studies have examined relationships across small geographical areas in the species-rich tropics.…”

Plant diversity effects on insect herbivores and their natural enemies: current thinking, recent findings, and future directions

“…'Resource Specialization Hypothesis' argues that increased plant diversity provides a greater diversity of resources which favours an increase in consumer species richness due to an accumulation of consumers specializing on different resources [16,17].…”

“…A rich body of theory has been developed to predict the effects of plant diversity on communities at higher trophic levels ( [16][17][18][19][20][21][22], see Box 1). Despite this vast collection of theory behind plant diversity effects on associated faunas and the large number of empirical studies conducted thus far, formal evaluations of the mechanisms behind the observed patterns have been developed in natural communities (but see [20] for e.g.…”

“…Based on these findings, we argue that a push towards studies that explicitly manipulate diversity in ecologically relevant traits, particularly in the case of intra-specific diversity, is needed in order to gain a predictive understanding of plant diversity effects on plant-centred arthropod communities. Moreover, we recommend manipulating plant diversity on the basis of functional traits with particularly strong effects on consumers and for which we know the 2 Ecology/parasites/parasitoids/biological control Box 1 Ecological theories for the effects of plant diversity on communities at higher trophic levels and the mechanisms underpinning such effects.'Resource Specialization Hypothesis' argues that increased plant diversity provides a greater diversity of resources which favours an increase in consumer species richness due to an accumulation of consumers specializing on different resources [16,17].'More Individuals Hypothesis' postulates that high plant diversity increases plant productivity, such that an increase in the resource base positively influences consumer abundance, and that this in turn leads to an abundance-driven accumulation of consumer species [18].'Resource Concentration Hypothesis' poses that herbivores frequently forage in a density-dependent manner, and therefore increasing plant species or genotype number while keeping plant density constant reduces the probability of finding a preferred host plant species (or genotype), ultimately leading to lower herbivore abundance and damage on individual plants [21].'Resource Dilution Hypothesis' posits exactly the opposite: as the density of plant items (species or genotypes) decreases (i.e. dilution), herbivores concentrate on the few available items and thus cause more damage in species-rich than in species-poor communities [22].…”