Helicarion mastersi, (COX, 1868)

HELICARION MASTERSI ( COX, 1868) View in CoL

( FIGS 6 View Figure 6 , 20–24 View Figure 20 View Figure 21 View Figure 22 View Figure 23 View Figure 24 )

Vitrina mastersi Cox, 1868: 86 , pl. 14, figs 12, 12a; Pfeiffer, 1876: 24.

Helicarion mastersi View in CoL – Cox, 1909: 6; Iredale, 1941: 6; Pfeiffer & Clessin, 1881: 32; Tryon, 1885: 170, pl. 38, figs 48–49; Hyman & Ponder, 2010: 24, figs 6A, B, 7C, D, 8C, D, 9C, D, 12B, 13B, 14C, 15A–C; Stanisic et al., 2010: 302–303, 326.

Vercularion mastersi – Iredale, 1937: 9.

Helicarion mastersi mastersi View in CoL – Smith, 1992: 234.

Material examined

Holotype: AM C.101139 (Kiama, 34°40′S, 150°51′E, leg. G. Masters, pre-1868). GoogleMaps

Paratypes: AM C.103648 (same data as holotype) GoogleMaps .

Non-type material. See Supporting Information ( Table S1).

Description

External morphology: Shell golden brown to pale amber, 3.1–3.7 whorls. Body cream, greyish or fawn, with pink to orange-brown pink coloration, deepening on the tail; sole cream. Mantle lobes and shell lappets cream, sometimes lined with grey, with dark markings on underside.

Genital anatomy: Penis tubular, sometimes slen- der with a small bulge at proximal end, sometimes broad and slightly curving; epiphallus 1.5–3 times penis length, entering penis either apically or laterally (leaving a small blind tip) through a simple pore. Penial interior with> 20 closely spaced lamellae. Spermatophore with nine to 14 evenly spaced spines (N = 5) (in specimens from Kangaroo Valley, first branch is separated from remainder by a small gap).

Remarks

This species is delimited herein in a different manner from previous taxonomic studies, in that several populations from throughout NSW previously subsumed under the name H. mastersi are now recognized as members of H. cuvieri . This also applies to the two nominal species-taxa ‘ H. leopardinus ’ and ‘ H. callidus ’ introduced by Iredale (1941). See the description of H. cuvieri above for features that can be used to distinguish H. cuvieri and H. mastersi .

Helicarion mastersi is found from Kangarooo Valley in southern NSW to southern Sydney ( Fig. 6 View Figure 6 ). This species encompasses three well-differentiated subclades (I, J and K), described below. Differences between these three subclades include size and coloration, the presence or absence of a small blind penis tip and a varying number of spines on the spermatophore. To clarify the distinct status of these three forms further, denser sampling throughout the Upper Nepean dam catchment region and the Kangaroo Valley is necessary, particularly along potential zones of contact.

CLADE I

( FIGS 6 View Figure 6 , 20C View Figure 20 , 21G–I View Figure 21 , 22C View Figure 22 , 23C, F, I View Figure 23 , 24B View Figure 24 )

Diagnosis

External morphology: Shell golden brown to pale amber, 3.1–3.5 whorls ( Figs 20C View Figure 20 , 21G–I View Figure 21 ). Body greyish or orange brown, darkening on the tail; sole cream. Shell lappets often lined with grey, with dark markings on underside ( Fig. 22C View Figure 22 ).

Genital anatomy: Penis broad; penis-to-epiphallus ratio of 0.67–0.89, epiphallus entering penis laterally through simple pore. Spermatophore with nine to 11 evenly spaced branching spines of decreasing complexity; formula (1, 2, 6–8, 0–2) ( Figs 23C, F, I View Figure 23 , 24C View Figure 24 ).

Remarks

The range of this clade stretches from Macquarie Pass to southern Sydney ( Fig. 6 View Figure 6 ). The phylogenetic tree shows two clear groups: one from Razorback and Mt Kembla, and the other from Royal NP and Bulli Pass, but there are no significant anatomical differences.

Members of clade I can be distinguished from other Helicarion by their smaller size (they are similar in size to members of clades G and H but smaller than the other members of the genus) and from other NSW taxa by their grey-brown to orange-brown coloration. Like semislugs belonging to clades J and K, they have an interior penial sculpture of numerous rows of fine lamellae, but differ from these taxa in their broader penis, with a slightly lateral entry point, and spermatophore with fewer, less highly branched spines.

CLADE J

( FIGS 6 View Figure 6 , 20B View Figure 20 , 21D–F View Figure 21 , 22B View Figure 22 , 23B, E, H View Figure 23 , 24B View Figure 24 )

Diagnosis

External morphology: Shell golden, 3.2–3.7 whorls ( Figs 20B View Figure 20 , 21D–F View Figure 21 ). Body cream, with pale yellowish brown coloration on tail; sole cream. Mantle lobes and shell lappets pale ( Fig. 22B View Figure 22 ).

Genital anatomy: Penis slender, tubular, with small bulge at proximal end; penis-to-epiphallus ratio of 0.40–0.52, epiphallus entering penis apically through a simple pore. Spermatophore with 13–14 branching spines; formula (1–2, 12, 0, 0); first branch separated from remainder by a small gap ( Figs 23B, E, H View Figure 23 , 24B View Figure 24 ).

Remarks

Clade J is known only from near Bellawongarah, north of Nowra (see Fig. 6 View Figure 6 ). The majority of specimens have been collected along Kangaroo Valley Road as it crosses Berry Mountain. Very little material exists, reflecting the lack of collecting in this area; additional collecting might reveal a broader range.

Specimens belonging to clade J are similar in size to those of clade K but are slightly flatter in shape and can be distinguished by their paler body colouring. Individuals are similar in appearance to those belonging to clade F (part of H. cuvieri ) but can be distinguished by the lack of pigmented warts on the shell lappets. Members of this taxon have a unique genital anatomy of a relatively short penis (penis-to-epiphallus ratio 0.4–0.52) with a small swelling at the proximal end and no blind tip, and a robust spermatophore with 13–14 heavily branched spines and a gap between the first and second spines.

CLADE K

( FIGS 6 View Figure 6 , 20A View Figure 20 , 21A–C View Figure 21 , 22A View Figure 22 , 23A, D, G View Figure 23 , 24A View Figure 24 )

Diagnosis

External morphology: Shell golden, 3.2–3.7 whorls ( Figs 20A View Figure 20 , 21A–C View Figure 21 ). Body fawn, with pink coloration, deepening on the tail; sole cream ( Fig. 22A View Figure 22 ).

Genital anatomy: Penis broad, curved, with small blind tip; penis-to-epiphallus ratio of 0.50–0.81, epiphallus entering penis laterally through a simple pore. Spermatophore with 11 evenly spaced spines (N = 4), formula (0, 3, 7, 1) ( Figs 23A, D, G View Figure 23 , 24A View Figure 24 ).

Remarks

Clade K is found in and around Kiama (the type locality of H. mastersi ), at localities including M i n n a m u r r a N P a n d B a r r e n G r o u n d s N a t u r e Reserve ( Fig. 6 View Figure 6 ). Its nearest relatives are distributed close by (clade I in Macquarie Pass to the north and clade J in Kangaroo Valley to the west), but the three taxa are allopatric. Members of clade K can be distinguished from other members of H. mastersi by their pink body coloration and pale sole. These semislugs are similar in size to clade J but slightly larger than clade I. Anatomically, this taxon differs in the shape and size of the penis (particularly in the presence of a large blind penis tip) and the spermatophore type.

BIOGEOGRAPHY

The genus Helicarion is widespread and comparatively abundant in south-eastern Australia; a probable testimony to its fairly well-developed dispersal ability. It occurs throughout the zone of temperate forests and woodlands with mild to warm summers, but generally not in the zones of hot summers to the north and west of its current range and the zone of cold summers in the alpine areas of Tasmania ( Fig. 6 View Figure 6 ).

This entire region was exposed to more xeric conditions during the Plio-Pleistocene glacial cycles. A review of phylogeographical analyses has revealed that climatic fluctuations in this region have caused range contractions of mesic biota during the Quaternary, followed by expansions during wetter periods ( Byrne et al., 2011). Furthermore, it has been demonstrated that these contractions have produced high levels of intraspecific differentiation in a range of species that are restricted to wet forests and alpine areas, which has resulted from the long-term isolation of populations in refuges and from local extirpations of populations in areas with more xeric conditions ( Byrne et al., 2011).

A concordant history of historical range contraction into climatic refuges and subsequent range expansions is the probable cause of the observed genetic structuring in Helicarion . Such a scenario may also explain the existence of morphologically well-differentiated high-altitude groups in Helicarion , which may have undergone a long history of isolation, whereas lowland forms are deemed to have expanded their ranges relatively recently.

Based on the phylogeographical relationships documented here (e.g. Fig. 3 View Figure 3 ), it is reasonable to postulate that Helicarion has originated on the Australian mainland and has colonized Tasmania subsequently. Quaternary climatic cycles have impacted Tasmania even more profoundly than the continental mainland as they caused repeated glaciations and created links to the continental Australia owing to sea level fluctuations. These processes have promoted both the isolation of populations in glacial refugia and an exchange between Tasmanian and mainland biota (e.g. McKinnon et al., 2004). The signature of such fluctuations is seen in the phylogeny of Helicarion revealing significant lineage divergence among the Tasmanian populations and links with the continental fauna (subclade A).