The role of biotic interactions in shaping distributions and realised assemblages of species: implications for species distribution modelling

Abstract

Predicting which species will occur together in the future, and where, remains one of the greatest challenges in ecology, and requires a sound understanding of how the abiotic and biotic environments interact with dispersal processes and history across scales. Biotic interactions and their dynamics influence species' relationships to climate, and this also has important implications for predicting future distributions of species. It is already well accepted that biotic interactions shape species' spatial distributions at local spatial extents, but the role of these interactions beyond local extents (e.g. 10 km(2) to global extents) are usually dismissed as unimportant. In this review we consolidate evidence for how biotic interactions shape species distributions beyond local extents and review methods for integrating biotic interactions into species distribution modelling tools. Drawing upon evidence from contemporary and palaeoecological studies of individual species ranges, functional groups, and species richness patterns, we show that biotic interactions have clearly left their mark on species distributions and realised assemblages of species across all spatial extents. We demonstrate this with examples from within and across trophic groups. A range of species distribution modelling tools is available to quantify species environmental relationships and predict species occurrence, such as: (i) integrating pairwise dependencies, (ii) using integrative predictors, and (iii) hybridising species distribution models (SDMs) with dynamic models. These methods have typically only been applied to interacting pairs of species at a single time, require a priori ecological knowledge about which species interact, and due to data paucity must assume that biotic interactions are constant in space and time. To better inform the future development of these models across spatial scales, we call for accelerated collection of spatially and temporally explicit species data. Ideally, these data should be sampled to reflect variation in the underlying environment across large spatial extents, and at fine spatial resolution. Simplified ecosystems where there are relatively few interacting species and sometimes a wealth of existing ecosystem monitoring data (e.g. arctic, alpine or island habitats) offer settings where the development of modelling tools that account for biotic interactions may be less difficult than elsewhere.

Fig. 1

The main processes and filters that interact to structure species assemblages across geographical extents. Refined from Lortie et al. (2004) and Guisan & Thuiller (2005).

Fig. 2

Spatial extents at which the influence of environmental variables is likely to be detectable in spatially explicit data. Dark arrows are those presented in Pearson & Dawson (2003), and these are updated with examples cited herein (light arrows).

Fig. 3

Examples of how biotic interactions can shape distributions and realized assemblages of species at broad spatial scales. (A) Present-day geographic ranges of pumas (Puma concolor, red) in the New World and leopards (Panthera pardus, blue) in the Old World (IUCN, 2010) plotted together with additional range extent of both species during the Late Quaternary (dotted curved lines) and palaeorecords of pumas (Puma pardoides, triangles) from Eurasia (based on Hemmer et al., 2004). Expansion of leopards during the early Middle Pleistocene probably replaced pumas in their Old World area of origin (Hemmer, 2004). (B) Cross-taxon congruence in species richness of figs (Ficus spp.) and avian obligate frugivores across sub-Saharan Africa (data from Kissling et al., 2007). Species richness of both groups was subdivided into quartiles with cells in dark red (fourth quartile) indicating areas where both groups have highest species richness and cells in dark blue (first^t quartile) indicating lowest richness. The example illustrates how the broad-scale distribution of consumers is linked to the distribution of keystone food plants. (C) Distribution of hedgehogs (Erinaceus spp.) in Europe (IUCN, 2010) with post-glacial expansion routes (black arrows) as proposed by Hewitt (1999). Mutual exclusion over large spatial extents of such closely related species is likely to result from competition or other negative interactions. (D) Present-day geographic range (black circles) and Late Glacial-Early Holocene pollen records (red triangles) of Hippophaë rhamnodies compared with the current natural distribution of forest in Europe (blue shading). Natural post-last glacial maximum (LGM) reforestation of central and northern Europe restricted this shade-intolerant shrub H. rhamnoides to marginal tree-less habitats in the region. The current distribution is represented by diagonal shading. Present and past occurrence records were compiled from Lang (1994) and Hultén & Fries (1986). The distribution of natural forest in Europe was based on Bohn & Neuhäusl (2003).