Contributions to Zoology, 77 (2) - 2008

Blurring the picture: introductions, invasions, extinctions – biogeography in a global world

Vincent Nijman1,2, Ronald Vonk2

1.  Oxford Brookes University, School of Social Sciences and Law, Department of Anthropology and Geography, OX3 0BP Oxford, UK

2.  Zoological Museum, University of Amsterdam, PO Box 94766, 1090 GT Amsterdam, The Netherlands

Keywords: extinction, globalization, invasions, reintroductions, zoogeography

Global biogeography is the study of the natural distributions of plants and animals over the globe. Research in this discipline must reckon with the profound impact made by humans on the distribution of living organisms of which some impacts date back to historic times and others are more recent. Introductions nowadays occur almost everywhere, sometimes by deliberate action as part of conservation initiatives. One might say that these types of introductions take place on the ‘good side’ of human interference, but even then the effort of restoring the evolutionary balance may be counterproductive (see for instance the reintroduction of the ‘wrong’ species of lorises throughout Southeast Asia – Nekaris and Jaffe, 2007). A long list could be made of species re-introductions, rehabilitation, and restocking in Europe (wolves, beaver, red kite, e.g. Gorman, 2007; South et al., 2000; Nolet and Baveco, 1996; Evans et al., 1999) and North America (black-footed ferret, wolf; Reading and Kellert, 1993; Ripple and Beschta, 2003), but also South America (golden lion tamarind; Kierulff and De Oliveira, 1996), Africa (African wild dog; Gusset et al., 2008), South Asia (lions: Johnsingh et al., 2007), and Southeast Asia (orangutan, gibbon, leopard: Yeager, 1997; Nijman, 2006; Gippoliti and Meijaard, 2007). The only continent where no species have been introduced as part of a conservation programme seems to be Antarctica but surely this is only a matter of time.

Other phenomena that use human vectors are invasions, such as those of dreissenid mussels in the North American Great Lakes (e.g. Johnson and Padilla, 1996), or of Ponto-Caspian amphipods in Northwestern Europe’s freshwaters (Platvoet, 2007), sometimes greatly altering the balance and bringing along huge economic losses. Indeed, the impact of these non-native species can take on numerous forms, including predation and grazing impacts that are often strikingly apparent, while changes can also be more cryptic, but nonetheless profound, such as alterations to pollination and dispersal networks, or hybridisation (Whittaker and Fernandez-Palacios, 2007). While in time, these ‘additions’ to any given faunal assembly may blur our picture on the biogeography (‘…represents a newly discovered population of a species at a far-flung locality part of a relict distribution or was it simply transported there aided by humans?’), this is much more apparent when human-induced extinctions are involved. The lemurs from Madagascar (Burney et al., 2004), many large terrestrial vertebrates of North America and Australia (Flannery, 1994, 2001), birds of the Pacific (Steadman and Olson, 1985), and primates from China (Geissmann, 1995), were all wiped out by humans over a relatively short time period, and greatly alter our perspective of what animals ‘naturally’ are supposed to occur in any given area.

In our paper (Vonk and Nijman, 2007) analysing the topics of papers published in Contributions to Zoology in the last quarter of a century we noted that over this period the journal has changed from a largely alpha taxonomic journal to one that is, again, truly general in scope. The subject of Systematic Biology, in which we included topics such as biogeography, evolutionary biology, phylogenetics, and phylogeography, and Comparative Morphology nowadays make up about half of the papers published. Import papers in recent years dealt with the biogeography of well-known groups in much-studied regions such as amphibians in the West Palearctic (Arntzen et al., 2007; Veith et al., 2006) but also of lesser-known species from regions largely unstudied (isopods from the northern Sahara or pycnogonida from Socotra (Boughrous et al., 2007; Bartolino and Krapp, 2007). Biogeography and phylogeography have gained importance as research topics in zoology as is attested by the steady increase in both the number of journals devoted to this topic, such as the Journal of Biogeography (established in 1974), Ecography (1978), Global Ecology and Biogeography (1991) and Diversity and Distributions (1998), and the number of papers they publish (Fig.1).

Fig. 1. Number of zoogeographical papers that have appeared in four biogeographical journals (Journal of Biogeography, Global Ecology and Biogeography, Ecography, and Diversity and Distributions) and Contributions to Zoology during the last nine years, showing a steady increase in numbers (source Thomson Scientific Web of Science)