Fig. 1. Overview of positive and non-positive relationships
between dispersal-related traits and range size examined in this review.
The number of positive and non-positive relationships is indicated for
(a) each realm (terrestrial, marine, freshwater), (b) clade and specific
taxonomic groups (animals, plants, fish, insects, crustaceans, birds,
mammals, echinoderms, molluscs, amphibians, liverworts, reptiles) and
(c) total. Mycorrhiza, trematodes, diatoms and invertebrates were not
included here because they had less than four reported relationships
(all non-positive).
There is also a clear spatial structure in study location (Fig. 2). For
terrestrial systems, most of the studies have been performed in the
palearctic region (23 studies), followed by studies including multiple
regions (i.e., studies that include more than one region, including
global studies) (15 studies), whereas much less attention has been given
to neotropical and paleotropical regions (including the Madagascar
region). For marine systems, 32% of the studies (10 studies) examined
multiple regions, followed by studies in the Indo-Pacific and the
Tropical Eastern Pacific (26%, 8 studies each), whereas the Atlantic
and Mediterranean regions were much less studied (4 and 1 study
respectively, Fig. 1). For freshwater systems, only 2 studies have been
performed for multiple regions, the remaining 5 studies have only
considered Nearctic a Palearctic regions (2 and 3 studies,
respectively).