Fig. 5: Factors underlying the observed differences in endemism (complementarity) between hemispheres.

a, b Extratropical landmasses in the southern hemisphere (S) are smaller and more disconnected than in the northern hemisphere (N; a), resulting in smaller ranges and higher endemism (here exemplified by phylogenetic complementarity) in the southern hemisphere (b). Values for rank phylogenetic complementarity against latitude (n = 14,640 grid cells) are summarised in latitudinal bands of 5° (n = 26 latitudinal bands). Points are coloured according to relative rank and boxplots according to median values. Values for absolute range size (log-transformed) of phylogenetic lineages against latitude (n = 19,914) are summarised in latitudinal bands of 5° (n = 25 latitudinal bands) according to the range midpoint. Colours represent southern (red) and northern (blue) hemispheres; latitudinal bands inside the tropics are lighter coloured. Boxes show median and 1st and 3rd quartiles; whiskers extend to largest and smallest, respectively, values up to 1.5 x inter-quartile range beyond the quartiles; data points beyond the end of the whiskers are plotted individually. c,d Functional and phylogenetic endemism in the southern hemisphere (S) is high because of the occurrence of old phylogenetic lineages with unusual morphologies that have no equivalent in northern high latitudes (N). These include c basal lineages of Australaves (Cariamiformes [green, 2 spp.]) and Passeriformes (e.g. Atrichornithidae [orange, 2 spp.], Menuridae [red, 2 spp.], Acanthisittidae [blue, 2 spp.]) and d the Palaeognathae (Tinamiformes [orange, 47 spp.], Rheiformes, Struthioniformes, and Casuariformes [red, 9 spp.], and Apterygiformes [blue, 5 spp.]), many of which also occupy small ranges. e Several other bird lineages, e.g. penguins (Sphenisciformes [red, 18 spp.]) or albatrosses (Diomedeidae [blue, 22 spp.]) are largely restricted to southern mid and high latitudes, i.e. the Antarctic region. Despite their highly endemic avifauna, sub-Antarctic islands and Antarctica are commonly omitted from global diversity studies. Bird silhouettes by DMD.