Isoodon spp

Smales, L. R., Wood, J. A. L. & Chisholm, L. A., 2024, A review and comparison of the nematode assemblages of the Australian golden bandicoot, Isoodon auratus, the quenda, I. fusciventer and southern brown bandicoot, I. obesulus (Peramelidae), from material held in the south Australian museum, International Journal for Parasitology: Parasites and Wildlife 24, pp. 100938-100938 : 100938-

4.6. Comparison of nematode communities of Isoodon spp .

Historically there appears to have been little or no overlap of the geographic ranges of I. fusciventer , I. macrourus and I. obesulus and, as populations have declined, even less opportunity for interaction between the components of their nematode assemblages. The known fossil records of all the extant and extinct bandicoot species show overlap of range only between the extinct Perameles myosuros Wagner and P. papillon Travouillon & Phillips with I. fusciventer and the extinct P. papillon and P. eremiana Spencer with I. obesulus (see the distribution maps of Baker and Gynther, 2023). This suggests that Isoodon speciation could be the result of the dissolution of east-west connectivity and gene flow during the mid- Miocene. Rix et al. (2015), however, argue that although the biogeographic barrier of the Nullabor divide was formed through the late Oligocene and the Miocene many mammal species were sufficiently vagile to cross that barrier. Quantitative phylogenetic data is needed to provide further evidence as to the possibilities of interaction between the components of the nematode assemblages of Isoodon spp . Insufficient information is available to comment on the nematode assemblage of I. auratus or to compare it with that of I. macrourus , although their geographic ranges overlap in the Kimberley district of Western Australia and northern parts of the Northern Territory ( Baker and Gynther, 2023). Isoodon macrourus has the largest geographic range (along the northern and eastern coasts of Australia), the greatest climatic differences (tropical monsoon to humid subtropical) ( Australian Bureau of Meteorology, 2023) and the most speciose nematode community (18 genera, 27 fully identified species) ( Smales et al., 2023a). By comparison I. fusciventer has the smallest geographic range (southwestern Western Australia), the least varied climate (warm to hot mediterranean) ( Australian Bureau of Meteorology, 2023) and the least speciose nematode community (10 genera, 8 species). Isoodon obesulus , having the most fragmented geographic range (the southern and southeastern coasts) and a variable climatic range (cool temperate to warm to hot mediterranean) ( Australian Bureau of Meteorology, 2023) has a nematode community (12 genera, 14 species) that falls between the two other host species. These findings are consistent with analyses that demonstrate that host geographical range size is one of the major determinants of parasite species richness ( Kamiya et al., 2013; Dallas et al., 2020). The differences in parasite species composition are also reflected in the Sorensen’ s indices of similarity with I. fusciventer and I. macrourus having the least similar communities (17.1 %). Only one species, the dromeostrongylid Peramelistrongylus skedastos was found in all three host species.

7

The most prevalent nematode taxa in species of Isoodon were ascaridids. Seven species of Linstowinema and four species of Labiobulura were identified and each host species has a unique fauna of nematode species ( Table 7). For example, Li. inglisi was present only in I. fusciventer , Li. tasmaniense and Li. cinctum only in I. obesulus and Li. maplestonei and Li. latens only in I. macrourus . Most ascaridids have complex life cycles with larval stages using insects, earthworms and small vertebrates as intermediate hosts ( Anderson, 2000) and all bandicoot species include a range of such items in their preferred diets ( Baker and Gynther, 2023). Differences in specific dietary choices and availability of infected food items due to geographic and climatic range could be the drivers of each host’ s unique nematode species profile.

The differing species composition of the nematode assemblages of the three brown bandicoots, Isoodon spp . can be further demonstrated by the species profile of the strongylids. Of the families represented in this study, most have direct life cycles ( Anderson, 2000). There is a high prevalence, 25.4%, of Asymmetracantha tasmaniensis in I. fusciventer a lower prevalence of 6.5% in I. obesulus and absence in I. macrourus . Mackerrastrongylus mawsonae is found only in I. fusciventer while M. peramelis and M. isoodon , with the exception of a single instance in I. obesulus , are found only in I. macrourus ( Table 7). There was a greater similarity in community composition (Sorensen’ s indices greater than 50%) when genera were considered. The characteristic nematode fauna of all the species of the host genus was a fauna in which species of Labiobulura and Linstowinema were the most prevalent. This prevalence was emphasized in that the only nematode species recovered from I. auratus were one species of each genus.