Antechinus subtropicus, Van Dyck and Crowther

Dyck, Steve Van, 2014, The Black-tailed Antechinus, Antechinus arktos sp. nov.: a new species of carnivorous marsupial from montane regions of the Tweed Volcano caldera, eastern Australia, Zootaxa 3765 (2), pp. 101-133 : 118-119

(16) A. arktos versus A. subtropicus Van Dyck and Crowther

Pelage: A. arktos has a brownish-grey head that changes markedly to an orange-brown rump, fuscous black hindfeet, a thick-based, finely-furred, black tail and an orange-yellow eye and cheek patch; A. subtropicus is uniformly brownish on the head and back.

External Measurements: A. arktos is larger than A. subtropicus in absolute measurement for hf in males and females. A. arktos is significantly larger than A. subtropicus for males at tv ( Table 5).

Craniodental Characters: A. arktos is larger than A. subtropicus in absolute measurement for a range of characters in males and females, as follows: APV, BL, Dent, IBW, IOW, IPV, HT, PL, NWR, PML, UML, HT-B, I 1 -P 3, LML, I 1 -P 3 and UPL. A. arktos is significantly larger than A. subtropicus for a range of characters: in males NW, OBW and ZW, and in females at OBW, TC and BuL ( Table 5).

Other Comments: A. arktos occurs in south-east Qld and north-east NSW in areas of high elevation and rainfall on the Tweed Volcano caldera, whereas A. subtropicus appears to have a more subtropical distribution, occurring from Gympie south-east Qld south to Border Ranges NP in north-east NSW. The two species conceivably co-occur. Genetics: uncorrected pairwise difference at the mitochondrial gene CytB between A. arktos and A. subtropicus is 16.3%.

Bivariate Scatterplots

A range of scatterplots are shown for dental variables differentiating A. arktos from the three subspecies of A. swainsonii ( Figures 6 and 7 are A. arktos versus A. s. swainsonii and A. s. mimetes; Figures 8 and 9 are A. arktos versus A. s. insulanus). Compared with A. swainsonii , A. arktos is most easily differentiated from A. s. swainsonii and A. s. mimetes at numerous dental characters, particularly those associated with palatal vacuity length, skull and tooth breadth. A. arktos has smaller holes in the front of the skull and tends to have smaller 2 nd upper molar teeth than A. s. insulanus.

DFA and CVA

Discriminant Function Analysis (DFA) indicated that 100% of females and males were clustered into the 4 taxon groups ( A. arktos , A. s. swainsonii , A. s. mimetes, A. s. insulanus) correctly (posterior probabilities all equal to 1.00, not shown), based on the Mahalanobis distance of each individual from the centroid of the a priori species group. For CVA, 100% of the variation in dental characters was explained in the first three canonical roots for males and females. Variation was very well resolved for both sexes (although more clearly for females than males), as eigenvalues for the first three canonical roots were well above 1 (males: root 1 = 55.9; root 2 = 16.0; root 3 = 11.3; females: root 1 = 366.9; root 2 = 282.9; root 3 = 6.5) and about two-thirds of the variation was explained in the first root (67%) for males, whereas just over half (56%) was explained in the first root for females. However, cumulatively the first two roots explained 86% of variation in males and a massive 99% in females. Figures 10–11 show scatterplots of canonical roots 1–2, for males and females, respectively; all four taxa are very tightly clustered within their taxon and very well separated between taxa, for both sexes, but particularly females. Canonical analysis suggests that A. arktos most closely resembles A. s. mimetes and A. s. insulanus, and to a lesser degree A. s. swainsonii , which reflects their relative geographical proximities. This is a reflection of the large and robust A. arktos skulls, compared with the generally narrow and slender A. s. swainsonii skulls from Tasmania as differentiated from the generally more robust A. s. mimetes from south-east Australia and particularly A. s. insulanus from the Grampians.

Figures

FIGURE 6. Scatterplot of anterior palatal vacuity length (APV) versus inter palatal vacuity distance (IPV) measures for male A. arktos (closed circles), A. s. swainsonii (open triangles) and A. s. mimetes (open circles).

FIGURE 7. Scatterplot of anterior palatal vacuity length (APV) versus inter palatal vacuity distance (IPV) measures for female A. arktos (closed circles), A. s. swainsonii (open triangles) and A. s. mimetes (open circles).

FIGURE 8. Scatterplot of anterior palatal vacuity length (APV) versus upper molar 2 width (M2W) measures for male A. arktos (closed circles) and A. s. insulanus (closed triangles).

FIGURE 9. Scatterplot of anterior palatal vacuity length (APV) versus upper molar 2 width (M2W) measures for female A. arktos (closed circles) and A. s. insulanus (closed triangles).

FIGURE 10. Scatterplot of canonical variates scores (roots 1 and 2) for males of A. arktos (closed circles) and the three subspecies of A. swainsonii: A. s. swainsonii (open triangles), A. s. mimetes (open circles) and A. s. insulanus (closed triangles).

FIGURE 11. Scatterplot of canonical variates scores (roots 1 and 2) for females of A. arktos (closed circles) and the three subspecies of A. swainsonii: A. s. swainsonii (open triangles), A. s. mimetes (open circles) and A. s. insulanus (closed triangles).