Triops species

Meusel, Franziska & Schwentner, Martin, 2017, Molecular and morphological delimitation of Australian Triops species (Crustacea: Branchiopoda: Notostraca) - large diversity and little morphological differentiation, Organisms Diversity & Evolution (New York, N. Y.) 17 (1), pp. 137-156 : 153-154

Distribution of Triops species in Australia

The large number of species derived from our analyses inevitably limits the number of individuals studied per species and impedes well-founded conclusions regarding the species’ distribution, biogeography, and phylogeography. Nevertheless, certain patterns are apparent. Although a majority of species has been found in only one of the regions studied with some found only in a very small area, several others have wide geographic distributions over central and eastern Australia. These patterns are comparable to those reported for other Australian large branchiopods like Spinicaudata ( Schwentner et al. 2012b, 2014, 2015a, b), Cyclestheria ( Schwentner et al. 2013) , and Anostraca ( Rogers and Timms 2014; Timms 2012), where a few species are widespread, while many others are restricted in their distribution. The majority of species are confined to either western, central, north-eastern, or south-eastern Australia. It is noteworthy that the lower Cooper Creek basin features predominantly species that also occur in south-eastern Australia, rather than those from the upper Cooper Creek basin (i.e., north-eastern Australia) ( Schwentner et al. 2014, 2015b), as was also the case for Triops . Species with wider geographic distributions tend to feature higher levels of genetic diversity (i.e., B, D, and L).

The level of sympatric and syntopic co-occurrences of Australian Triops species is noteworthy as syntopic occurrences of Triops species are very rare. There are only four reports of two syntopically occurring species each ( Murugan et al. 2009; Packard 1877; Pérès 1939; Thiéry 1991), and one of these includes Marsilea Pan in south-eastern Australia ( Murugan et al. 2009; locality 6 in the present study). In a similar study, Korn et al. (2010) identified four Triops species living in relative close proximity in the southern Iberian Peninsula, but none of these occur in syntopy and their geographic distributions do not even overlap. Conversely, in central and eastern Australia, sympatric and syntopic occurrences of different Triops species are relatively common, and up to three well-differentiated species were recorded from some localities. This suggests that some Australian Triops species may have relatively similar overall ecological requirements, possibly coupled with specialized niche differentiation to allow their coexistence.