Global knowledge on the distribution of alien animal species in regions around the world has dramatically improved in the last decade (e.g., Kraus 2009; Capinha et al. 2015; Dyer et al. 2017), and recently much information has also become available for plants (van Kleunen et al. 2015; Pyšek et al. 2017). This is an important development because many of the current theories of the distribution, causes, and consequences of biological invasions are based on macroecological analyses of regional floras and faunas (e.g., Jeschke and Strayer 2005; Cadotte et al. 2006; Lambdon et al. 2008; Blackburn et al. 2009; Capinha et al. 2015). However, there are still major gaps in data availability and the quality of information varies among regions (van Kleunen et al. 2015).

The new series launched in this issue of Biological Invasions thus aims to collect papers that provide information on complete alien floras or faunas of large regions; they can be complete checklists of all alien biota including casual, non-established taxa, or checklists of all naturalized (established) or invasive species occurring in a given region. Authors are invited to submit papers for this series in which they will describe the structure of the studied alien flora or fauna of the target region (for example, in terms of geographic origin, life histories, invaded habitat, time of introduction or introduction pathways), possibly accompanied by an analysis of basic patterns of alien species richness, diversity, or impacts, as well as factors underlying variation in these characteristics.

Submissions must clearly describe criteria used to identify species as alien, and to classify them according to their invasion status, and how these criteria relate to definitions used in invasion biology (e.g., Richardson et al. 2000; Blackburn et al. 2011). The geographic region for which the alien species diversity is reported must be clearly delimited and characterized. It is assumed that submissions will mostly refer to a large geographic scale (countries/states and administrative units within large countries; e.g., see van Kleunen et al. 2015; Pyšek et al. 2017).

Full species lists with other relevant available information (such as distribution in subunits of the target region where applicable, time of introduction into the region, habitat affinities, whether or not the taxon is invasive, or pathways of introduction into the region) must be published with the paper in the form of electronic supplementary material (preferably as an excel spreadsheet).

Papers published in Biological Invasions in the last decade that would have qualified for inclusion in the series span a wide range of taxonomic groups and geographic areas for which complete inventories of alien species were compiled (e.g., Novillo and Ojeda 2008; Borroto-Páez 2009; Galil 2009; Arianoutsou et al. 2010; Kull et al. 2012; Khuroo et al. 2012). We believe that the newly introduced Alien Floras and Faunas series, starting in this issue with an inaugural paper by Inderjit et al. (2017), based on thoroughly revisited information on the alien flora of India, will stimulate rapid closing of many existing gaps in our knowledge of regional alien species richness.