Comparative biogeography of Southeast Asia and the West Pacific region

Abstract

The relationship between the areas of Southeast Asia and the West Pacific region is still debated because of their complex historical geology and the enormous diversity of taxa. Cladistic methods have previously been used to reconstruct the relationships between areas in the region but never with such a high number of unrelated taxa (35). We use a compilation of phylogenies to investigate area relationships among Southeast Asia and the West Pacific region, run the comparative analysis with LisBeth [based on three-item analyses (3ia)] and compare the results with recently published geological reconstructions of the region. We discuss the relevance of such an approach to the interpretation of general pattern. The two questions addressed are: (1) is there an emerging common pattern; and (2) how to explain actual distributions of taxa in Southeast Asia and the West Pacific region. Three-item analysis found 27 optimal trees. An intersection tree reconstructed from the common threearea statements had an overall retention index of 84.8% and retrieved 13 nodes with two major branches compatible with a separation between Southeast Asia and the West Pacific region (i.e. congruent with some geological reconstructions). Any congruent patterns revealed by the combination of unrelated taxa should reflect a common cause. The extraction of information on area relationships contained in phylogenetic analyses of taxa consists of testing for area homologues. We obtained the tree from this region based on an empirical dataset which we hope will contribute to new insights into area classification in the region.

Tropical Asian species show that the Old World clade of ‘spiny solanums’ (SolanumsubgenusLeptostemonum pro parte: Solanaceae) is not monophyletic

“…Van Welzen et al, 2011;Ung et al, 2015), perhaps indicating recent speciation and active dispersal. This indicates independent dispersal events that have given rise to small numbers of closely related species in the Old World Tropics.…”

“…Morphological diversity in the Old World clade is similarly broad (Symon, 1981(Symon, , 1985Vorontsova & Knapp, in press). They all occur east of Lydekker's Line (see Simpson, 1977) and occupy part of the 'Australian area' defined by Ung et al (2015). 2), highlighting its importance as a centre of biodiversity in the region.…”

“…With the western Pacific, the region is well known as a centre of marine and terrestrial biodiversity (Michaux, 2010) and distribution patterns there have long intrigued biologists (e.g. Studies of distribution of native species of diverse groups of organisms have been used to reconstruct the historical biogeography and area relationships in the region (Van Welzen et al, 2011;Ung, Zaragueta-Bagils & Williams, 2015). Various lines have been drawn through the region demarcating biogeographic shifts in fauna and flora (Simpson, 1977;Van Welzen, Parnell & Slik, 2011); the differences among these reflect the complex history of geology and distribution of the taxonomic groups used in individual studies.…”

“…Wallace, 1863). Area relationships of the islands of Indonesia are particularly difficult to resolve (see differences in area definition between Van Welzen et al, 2011 andUng et al, 2015) and the region is seen as an important link between continental Asia and Africa, particularly in groups like Solanum, the evolutionary history of which is relatively recent (S€ arkinen et al, 2013). Studies of distribution of native species of diverse groups of organisms have been used to reconstruct the historical biogeography and area relationships in the region (Van Welzen et al, 2011;Ung, Zaragueta-Bagils & Williams, 2015).…”

“…Various lines have been drawn through the region demarcating biogeographic shifts in fauna and flora (Simpson, 1977;Van Welzen, Parnell & Slik, 2011); the differences among these reflect the complex history of geology and distribution of the taxonomic groups used in individual studies. Studies of distribution of native species of diverse groups of organisms have been used to reconstruct the historical biogeography and area relationships in the region (Van Welzen et al, 2011;Ung, Zaragueta-Bagils & Williams, 2015). Area relationships of the islands of Indonesia are particularly difficult to resolve (see differences in area definition between Van Welzen et al, 2011 andUng et al, 2015) and the region is seen as an important link between continental Asia and Africa, particularly in groups like Solanum, the evolutionary history of which is relatively recent (S€ arkinen et al, 2013).…”