Latitudinal gradients in biotic niche breadth vary across ecosystem types

Abstract

Several properties of food webs-the networks of feeding links between species-are known to vary systematically with the species richness of the underlying community. Under the 'latitude-niche breadth hypothesis', which predicts that species in the tropics will tend to evolve narrower niches, one might expect that these scaling relationships could also be affected by latitude. To test this hypothesis, we analysed the scaling relationships between species richness and average generality, vulnerability and links per species across a set of 196 empirical food webs. In estuarine, marine and terrestrial food webs there was no effect of latitude on any scaling relationship, suggesting constant niche breadth in these habitats. In freshwater communities, on the other hand, there were strong effects of latitude on scaling relationships, supporting the latitude-niche breadth hypothesis. These contrasting findings indicate that it may be more important to account for habitat than latitude when exploring gradients in food-web structure.

Niche-breadth of freshwater macrophytes occurring in tropical southern African rivers predicts species global latitudinal range

“…Our results complement the findings of Cirtwill et al (2015), who used a very different measure of niche-breadth to our approach, but nevertheless found, for freshwater communities (but not for communities in other ecosystem types), strong effects of latitude on scaling relationships (between species richness and average generality, vulnerability and links per species across empirical food webs).…”

“…Species which occupy lengthy ranges along niche-axes associated with such measures, and with correspondingly wide niche-breadth, are usually considered to be generalist strategists (Grime 1979;Murphy et al, 1990), with broad geographical range (Slatyer et al, 2013;Cirtwill et al, 2015). The converse is likely to hold for species which exhibit only short niche-axis lengths, with specialised survival strategies, and only limited geographical range.…”

“…Other approaches aim to determine species niche-breadth in terms of the proportion of populations found in, or using, the individual states of given resources (e.g., Carrillo-Angeles et al (2016), who utilised a resource-state niche-breadth index developed by Hulbert (1978), in a study of the cactus genus Astrophytum). At the other end of the spectrum is the approach of Cirtwill et al (2015) who used a biotic measure of niche-breadth based on average generality, vulnerability and links per species across a set of 196 empirical food webs, in their study of relationships between latitude and biotic niche-breadth in different ecosystems. In a recent meta-data analysis, Slatyer et al (2013) identified a number of niche-breadth measures for plant and animal species, 15 of which they categorised as "habitat" measures (e.g., number of different habitat-types occupied); six as "diet" measures (e.g., number of different food-types used); and five as "tolerance measures" (e.g., elevational range).…”

The use of DNA barcodes in food web construction—terrestrial and aquatic ecologists unite!

“…Indeed, multiple recent studies stress the need for identifying common rules dictating who interacts with whom within large communities (Gravel et al 2013;Morales-Castilla et al 2015;Bartomeus et al 2016). Interestingly, when food webs from different environments are collated in joint analyses of, e.g., latitudinal trends, partly different patterns appear in different environments, again suggesting slightly different drivers in different systems (Schleuning et al 2012;Morris et al 2014;Cirtwill et al 2015).…”

Size diversity and species diversity relationships in fish assemblages of Western Palearctic lakes

“…A1), maybe reflecting that biogeographical differences and ecological processes (e.g. higher interspecific competition) at local or evolutionary scales lead to increased niche specialisation towards low latitudes, as has been found in several previous studies (Griffiths 2006, Reyjol et al 2007, Mason et al 2008, Tedesco et al 2012, Schleuter et al 2012, Cirtwill et al 2015.…”