Biome: evolution of a crucial ecological and biogeographical concept

Abstract

A biome is a key community ecological and biogeographical concept and, as such, has profited from the overall progress of community ecology, punctuated by two major innovations: shifting the focus from pure pattern description to understanding functionality, and changing the approach from observational to explanatory and, most importantly, from descriptive to predictive. The functional focus enabled development of mechanistic and function-focused predictive and retrodictive modelling; it also shaped the current understanding of the concept of a biome as a dynamic biological entity having many aspects, with deep roots in the evolutionary past, and which is undergoing change. The evolution of the biome concept was punctuated by three synthetic steps: the first synthesis formulated a solid body of theory explaining the ecological and biogeographical meaning of zonality and collated our knowledge on drivers of vegetation patterns at large spatial scales; the second translated this knowledge into effective mechanistic modelling tools, developing further the link between ecosystem functionality and biogeography; and the third (still in progress) is seeking common ground between large-scale ecological and biogeographic phenomena, using macroecology and macroevolutionary research tools.

Keywords: azonal biomes; biogeography; biome modelling; climate; evolution of biome; genomic tools; plant functional types; vegetation zonality.

Figure 1

Two very popular biome schemes based on bioclimatic approach: (a) Holdridge's scheme (reproduced from Archibold, 1995; after Holdridge, 1947); (b) Whittaker's scheme (after Whittaker, 1970). Reproduced with permission from Elsevier Ltd (a) and Prentice Hall/Pearson Higher Education (b).

Figure 2

A modified classification scheme of zonal and azonal terrestrial biomes across subcontinental to global spatial scales; motivated by the original scheme of Walter & Box (1976). The bottom‐up succession follows the axis progressing ecosystem complexity and increasing spatial scale. Synusia is a functional (or spatial) subunit of a (biotic) community.

Figure 3

Physiognomic aspects of the African savanna. (a) Arid savanna grasslands with scattered scrub of the southern Kalahari, Khalaghadi Transfrontier Park, South Africa: partly stabilized dunes and calcrete outcrops fringing dry bed of the Nossob River. (b) Central Bushveld of Central Namibia: open savanna woodland dominated by Senegalia (Acacia) hereroensis in the Danie Viljoen National Park near Windhoek. (c) Woodland dominated by mopane (Colophospermum mopane): South Africa, Honnet Nature Reserve neat Tsipise, Venda. (d) Subescarpment Vachellia (Acacia) karroo thornveld with intensively grazed C4 grassland understorey, near Butterworth, Eastern Cape, South Africa. (e) Lowveld savanna woodlands of the Kruger National Park, South Africa, dominated by broadleaved Combretaceae. (f) Miombo woodlands (dense seasonal forest) with Brachystegia boehmii, Brachystegia microphylla, Brachystegia spiciformis, Uapaca kirkiana and Vangueriopsis lanciflora, Zimbabwe, Chimanimani Mountains. (g) Iconic Serengeti savanna grasslands; blue wildebeest (Connochaetes taurinus) migrating to Masai Mara Game Reserve (Kenya). Photo credits: (a–e) L. Mucina; (f) M.C. Lötter; (g) B.C. Tørrissen ( http://bjornfree.com/galleries.html).

Figure 4

Biomes of the world as modelled by BIOME4 (Kaplan et al., 2003) – a typical example of an equilibrium vegetation model. Reproduced from: Paleoclimate Modeling Intercomparison Project II ( http://pmip2.lsce.ipsl.fr/synth/biome4.shtml).

Figure 5

Ages of crown‐groups of selected lineages of Australian flora grouped by six inferred ancestral ‘biomes’, showing that the lineages that originated in the ‘sclerophyll’ (Mediterranean‐type woodlands and scrub biome) and ‘ever‐wet’ (rainforest) biomes are the oldest. The blue bar represents the Oligocene (34–23 million years ago (Ma)). The boxes show the median and the 25^th and 75^th percentiles, whereas the error bars show the 2.5^th and 97.5^th percentiles; n is the number of lineages analysed per ‘biome’. The alpine biome includes temperate grassland. (Source: Crisp & Cook, 2013: Fig. 8; reproduced with permission of the Annual Reviews Inc.). [Correction added after online publication 27 November 2018; the figure has been replaced with the correct figure; the figure legend is unchanged.]

Figure 6

A scheme of the conceptual evolution of a biome, involving basic objects, abstractions, elements, tools, and approaches of ecological (left lane) and evolutionary (right lane) pathways, both progressing from the observational to the explanatory phase of progress towards the modern understanding of the biome.