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Latitudinal Shifts of Introduced Species: Possible Causes and Implications

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Latitudinal Shifts of Introduced Species: Possible Causes and Implications Biol Invasions (2012) 14:547–556 DOI 10.1007/s10530-011-0094-8 ORIGINAL PAPER Latitudinal shifts of introduced species: possible causes and implications Qinfeng Guo • Dov F. Sax • Hong Qian • Regan Early Received: 26 January 2011 / Accepted: 22 August 2011 / Published online: 4 September 2011 Ó Springer Science+Business Media B.V. (outside the USA) 2011 Abstract This study aims to document shifts in the those in their native ranges. Only a small fraction of latitudinal distributions of non-native species relative species examined (i.e.\20% of animals and\10% of to their own native distributions and to discuss plants) have expanded their distributions in their possible causes and implications of these shifts. We exotic range beyond both high- and low-limits of used published and newly compiled data on inter- their native latitudes. Birds, mammals and plants continentally introduced birds, mammals and plants. tended to shift their exotic ranges in similar ways. In We found strong correlations between the latitudinal addition, most non-native species (65–85% in differ- distributions occupied by species in their native and ent groups) have not reached the distributional extent exotic ranges. However, relatively more non-native observed in their native ranges. The possible drivers species occur at latitudes higher than those in their of latitudinal shifts in the exotic range may include native ranges, and fewer occur at latitudes lower than climate change, greater biotic resistance at lower latitudes, historical limitations on ranges in native regions, and the impacts of humans on species Electronic supplementary material The online version of this article (doi:10.1007/s10530-011-0094-8) contains distributions. The relatively restricted distribution of supplementary material, which is available to authorized users. most species in their exotic range highlights the great potential of future spread of most introduced species & Q. Guo ( ) and calls for closely monitoring their directional USDA FS, Eastern Forest Environmental Threat Assessment Center, 200 WT Weaver Blvd., Asheville, spread under climate change. NC 28804, USA e-mail: [email protected] Keywords Climate change Á Invasion potential Á Land use Á Niche Á Risk assessment Á Species range D. F. Sax Ecology and Evolutionary Biology, Brown University, 80 Waterman Street, Box G-W, Providence, RI 02912-0001, USA H. Qian Research and Collections Center, Illinois State Museum, Introduction 1011 East Ash Street, Springfield, IL 62703, USA Non-native populations have a profound influence on R. Early native species and ecosystems across the globe, Ca´tedra ‘‘Rui Nabeiro’’ Biodiversidade, Universidade de E´ vora, Casa Cordovil 2a Andar, Rua Dr. Joaquim causing extinctions and changes in ecosystem func- Henrique da Fonseca, 7000-890 E´ vora, Portugal tioning (Mooney and Hobbs 2000). These impacts 123 548 Q. Guo et al. have led to interest and extensive study of the Walther et al. 2009; Britton et al. 2010). But given distribution of non-native populations—hereafter the consistent limitations of climate as an ideal referred to as non-native species (e.g., Lonsdale predictor of non-native species distributions, it is 1999; Sax et al. 2002, 2005; Leprieur et al. 2008; important to consider the utility of other potentially Pysˇek et al. 2010). A persistent theme in these studies informative indicators. has been a search for characteristics of non-native Latitudinal patterns and the search for latitudinal species that predict their capacity to spread broadly in ‘rules of thumb’ for non-native species distributions an introduced region (e.g., Baker and Stebbins 1965; have the potential to be useful, but this topic has not Lockwood et al. 2007; Davis 2009). Much work has been addressed comprehensively. This is unfortunate indicated that species traits can be used to predict since latitude integrates many aspects of biotic, their potential to spread and the eventual size of their abiotic and human influences that are believed to be non-native distribution (e.g., Richardson et al. 1994; important in limiting species distributions—such as Rejma´nek and Richardson 1996; Smith et al. 2007). climate, soil type, biotic diversity, and land use. Recent work, however, has indicated that in addition Consequently, examining non-native distributions in to species traits, human influences on the environ- the context of latitude, which can be easily quantified, ment and the size of human economies can be can potentially inform the limitations and potential strongly correlated with the distributional patterns of expansion of distributions of non-native species, large numbers of non-native species (Leprieur et al. particularly at a large scale. Indeed, work conducted 2008; Pysˇek et al. 2010). to-date has shown latitude to be an important The distribution of non-native species is also predictor of non-native species distributions and presumed to be strongly influenced by climate. For mediator of ecological processes affecting distribu- instance, the concept of ‘climate matching’ suggests tions. Colautti et al. (2009) found that differences in that species have the potential to become naturalized species performance between native and naturalized only in places with climates similar to those expe- ranges were strongly influenced by the latitude at rienced in their own native ranges (e.g. Mack 1996; which species performance was measured. Rejma´nek Thuiller et al. 2005). Although there is support for the (1996) and Lonsdale (1999), among others, have importance of climate matching in limiting the observed that temperate mainlands are more invaded distribution of non-native species, much of this than tropical ones. Sax (2001) showed that non-native support suggests that a species’ native climatic species of many taxonomic groups on many conti- distribution is not a perfect predictor of its potential nents show predictable latitudinal gradients in species non-native distribution. For example, most studies richness and geographic range size. Sax (2001) also that have compared the climate-niche envelope of showed that birds and mammals were less likely to species’ native and naturalized distributions have become naturalized at latitudes lower than those in found that non-native species are distributed at least their native range than at latitudes higher than those in some places that they are not predicted based in their native range. Pysˇek and Richardson (2006) solely on their native climatic distributions (Beerling found a general pattern of decreasing naturalization et al. 1995; Welk et al. 2002; Broennimann et al. rates with increasing latitude in plants. Finally, over 2007; Fitzpatrick et al. 2007; Alexander and Edwards paleontological timescales, Jablonski (2008) has 2010; Gallagher et al. 2010). In some cases, climate shown that temperate latitudes are generally invaded appears to be a particularly poor predictor of potential from species that inhabit tropical latitudes. Thus, we distributions of non-native species, e.g., species with believe that a large-scale study is needed to identify small native distributions (and presumably restricted the existence and predictive importance of latitude in native climatic distributions) that have nonetheless limiting non-native species distributions. acquired extensive non-native distributions, such as Here we examine whether there are rules of thumb the Monterey pine, Pinus radiata (Sax et al. 2007). regarding how naturalized species’ latitudinal distri- Additional work, particularly in the context of global butions compare to their own native distributions. climate change, is continuing to pursue the relative Specifically, we compare the highest and lowest influence of climate on non-native species distribu- latitudinal-limits between the introduced and their tions (e.g., Thuiller et al. 2005; Peterson et al. 2008; native ranges, with a particular focus on whether 123 Latitudinal shifts of introduced species 549 non-native species approach or exceed the latitudinal hemisphere and have tropical, subtropical, temperate, limits experienced in their own native distributions. and boreal areas along a latitudinal gradient. This Species included in this study are birds and mammals close matching provides unique opportunities for introduced to continents and islands across the world comparing species range size and location in terms of and plants introduced between eastern Asia and North latitude and climate zone in native and naturalized America. Our primary goal is to address whether and regions. Because many species are distributed in to what extent non-native species might have super- more than one climatic zone, the continuous and seded their native latitudinal distributions. We dis- more-or-less parallel arrangements of multiple cuss the possible mechanisms, consequences, and climatic zones in eastern Asia and North America implications of such observations, while bearing in provide a full spectrum of latitude and climate mind the differences in observed patterns among gradients from the tropics to the arctic, within which taxonomic groups, particularly between woody and the spread of a species in its recipient region can be herbaceous plants or between birds and mammals. meaningfully compared to that in its native region (see examples of these climatic gradients in Fig. S1). Eastern Asia and North America each have received many non-native species from each other and else- Methods where and the numbers continue to increase due to growing trade and human travel between the
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