Revision of the Australian millipede genus Pogonosternum Jeekel , 1965 , with descriptions of two new species ( Diplopoda , Polydesmida , Paradoxosomatidae )

Abstract. The southeastern Australian millipede genus Pogonosternum Jeekel, 1965 is revised. Pogonosternum nigrovirgatum (Carl, 1902), P. adrianae Jeekel, 1982 and P. laetificum Jeekel, 1982 are redescribed; P. jeekeli Decker, sp. nov. and P. montanum Decker, sp. nov. are described from Victoria, New South Wales and Tasmania. P. nigrovirgatum infuscum Jeekel, 1982 and P. coniferum Jeekel, 1965 are junior synonyms of P. nigrovirgatum (Carl, 1902). An updated key to all five species of the genus is presented.


Introduction
The family Paradoxosomatidae is one of the largest families of millipedes with 198 named genera and at least 975 valid species (Nguyen & Sierwald 2013).Australia has 40 genera and more than 139 described species of predominantly short range endemics (Mesibov 2006(Mesibov -2016) ) and hundreds of undescribed paradoxosomatid species in New South Wales (Car 2009), Queensland (Mesibov 2008) and Western Australia (Car et al. 2013).
Relationships within the genus Pogonosternum were recently investigated, using an integrative approach incorporating sequence data and morphology of gonopods (Decker 2016a).The phylogenetic analysis revealed five species groups, of which two were undescribed: one from the Australian Alps in New South Wales and Victoria, and another with a trans-Bass Strait distribution in northeastern Tasmania and eastern Victoria.The five species groups exhibit a high intraspecific genetic variability and highly localized haplotypes, suggesting that they were confined to multiple refugia during Pleistocene glacial cycles on the southeastern Australian mainland.Furthermore, the data suggest that northwestern Tasmania was colonized by P. nigrovirgatum, probably from central Victoria, and northeastern Tasmania by an as yet undescribed species from eastern Victoria (Decker 2016a).
The present paper reviews the genus Pogonosternum based on extensive new collections and adds two new species from Victoria, New South Wales, and Tasmania.Three species are redescribed, one species and one subspecies are synonymised, and an updated key to all species is provided.

Specimen collecting and preservation
Pogonosternum specimens were collected by hand in Victoria and New South Wales in August 2014 by Decker, Voigtländer and Mesibov.Most sites were searched for 1-3 hours with the aim of finding 1-3 adult males; at only a few localities Pogonosternum was abundant.Specimens were killed and stored in 95% ethanol, with a change of ethanol (95%) after 1-2 months.Specimens in 70-80% ethanol were borrowed from the collections of various natural history museums noted in the text.A total of 810 specimens were examined, and locality, date, collector, collection number and coordinates (WGS84 decimal degrees) for all records are provided in Supplement 1.

Illustrations
Millipedes were photographed alive in the field.Preserved specimens were imaged with a Leica® Z6 Apo stereo microscope and Leica® DFC420 camera.Focus-stacked images were assembled from 25-40 source images using the software package Leica® Application Suite 4.5.
Gonopod drawings were traced from printed photographic images using a light box.
For scanning electron microscopy (SEM), samples were dehydrated through an ethanol series (80%, 90%, 2× 99.9%), dried in a desiccator overnight, and mounted on aluminium stubs before being sputter coated with gold-palladium.SEM images were acquired digitally using a JEOL JSM-6510 LV microscope, and samples were removed from stubs and returned to alcohol after examination.
All images were later edited using Adobe Photoshop CS4 and assembled into plates.The distribution map was created with ArcGIS version 10.
The genus is best defined by the gonopod structure (Fig. 1).All Pogonosternum species have an anterior laminate femoral process 1 (fp1) with a second adjacent smaller femoral process 2 (fp2).A large prolongation of the femorite (prof) bears close to its base a lateral femoral sub-process (lp), slightly distal to the anteriorly arising solenomere (S).The solenomere is long, laminate and nearly semicircular with a single slender solenomere tip process (stp) directed apically.
A similarly curving solenomere is present in the antichiropodinae genera Antichiropus Attems, 1911, Helicopodosoma Verhoeff, 1924and Notodesmus Chamberlin, 1920, but, apart from Antichiropus, a prolongation of the femorite (prof) is absent or only poorly developed in these genera.Antichiropus species differ in having a longer, nearly circular solenomere with a process on its inner surface one third of the distance to the apex and often additional solenomere processes.
In the field, Pogonosternum species are easily distinguished from other paradoxosomatid species in southeastern Australia by their distinctive colour pattern and lack of midbody paranota.

Description
The members of the genus Pogonosternum are very homogeneous in their morphology, although some non-gonopod characters can be used in combination with gonopod features to distinguish species: body length, colouration, distribution of male leg brushes, coxal processes on second legpair of females and form of anterior spiracles.
The following general description applies to all species if not otherwise mentioned in the text or descriptions of species.
Colouration.Colour in fresh material (Figs 8,12,15,18,22,26): head blackish brown, lateral side, labrum and behind antennal sockets chestnut brown.Antennae blackish brown; distal margins of antennomeres, basal antennomere and base of setae lighter.Legs chestnut brown, tarsus darker.Collum blackish brown with median brownish-yellowish goblet-shaped stripe narrowing in anterior 1/3 of length from anterior margin.Dorsum with one or two contrasting light yellowish brown, broad, longitudinal stripes reaching from collum to epiproct.Flanks and area around ozopores more or less lighter.Anal ring blackish brown with light yellowish brown median stripe, epiproct entirely light brown to pale.Colour stripe sometimes absent from anal ring and only epiproct lighter.Margin of anal ring and anal valves lighter.Hypoproct pale.
Gonopod morpholoGy.Parts of the telopodite are named following Car et al. (2013), with differing terms used by Jeekel (1965Jeekel ( , 1982a) ) given in brackets (Fig. 1).Coxite = C; femorite = F; femoral process = fp1 (femoral process, process f), fp2 (lobe at transition between femur and postfemur, process a); lateral process = lp (postfemoral process, process c); prefemorite = PF; prolongation of femorite = prof (tibiotarsus, process b); solenomere = S (process k); solenomere tip process = stp.Femorite (F) moderately long, moderately slender or slightly enlarged distally.Femoral process 1 (fp1) arising from anterior apical part of translucent fringe of femorite, in most species developed as moderate to large subtriangular process.Femoral process 2 (fp2) arising mesad-posteriad to femoral process 1 (fp1) and, except in P. adrianae, often much smaller than fp1 or greatly reduced, as in P. laetificum.Long prolongation of femorite (prof) arising posteriorly.Above base of prof a slender lateral process (lp), except in P. montanum Decker, sp. nov.where it is on mesal side and arises distal to the solenomere.Semicircular solenomere (S) arising anteromesally above lp, with a single slender solenomere tip process (stp).Antennomere pubescence moderately dense, denser and longer distally.A slightly swollen and lighter circular area, called the bean-shaped area by Jeekel (1982a), behind antennal sockets and a slightly swollen and lighter circular area in a depression within the postantennal groove (Fig. 2A).The two structures may represent sense organs such as the Tömösváry organ or intracerebral photoreceptors (= accessory lateral eyes), which have not yet been studied in Polydesmida (see Müller & Sombke 2015).present on metazonites, especially on metatergites and towards posterior margin (Fig. 2C), ventrally cells with dentation (Fig. 2D).Limbus long, lamellar with microdentate fringe arising from a row of subrectangular cells.Single cells of second cell row anterior to limbus anterolaterally with two micropores, between these cells, 3-6 cells without micro-pores (Fig. 2E).
Sternites a little wider than long, transverse depressions deeper than longitudinal, moderate and long setation, directed mostly posteroventrally.Rounded-trapezoidal lamella between anterior legpair on ring 5 (Fig. 3).No significant variation of shape of lamella was observed within or between species.
Small to prominent cones near base of anterior and midbody legs pointing ventrad are only present within local populations of P. nigrovirgatum.spiraCles.Well-separated on diplosegments (Fig. 4A).Anterior spiracle located anterodorsally of anterior leg coxa, posterior spiracle located relatively more anteriorly above posterior leg.Spiracular rim a more or less raised wall.Spiracular opening filled with spiracular filter composed of numerous distally bifurcated lamellae (Fig. 4B); filter can be U-folded or twisted, emergent above rim or not.
Anterior spiracles ovoid, rim raised and often with an anterodorsal extension.Posterior spiracle ovoid to subtriangular, rim low without conspicuous extensions.
telson.With two dorsolateral setae and one lateral seta in one line on each side with slightly produced papillae (Fig. 4C).Epiproct with tip truncate, slightly curving downwards, lateral and dorsal setal papillae moderately produced.Spinnerets located in smooth depression, arranged in trapezoid with dorsal setae slightly closer together than ventral.A more or less distinct rounded notch located lateral to ventral row of spinnerets.Individual spinneret seta with short single-walled sleeve (Fig. 4D).Anal valves each with two long setae and raised margin, with broad uncinate process on lateroventral portion of anal valves.
leGs.Of moderate length extending laterally and easily visible from above.All species of Pogonosternum have similarly shaped legs.Male legpair 1 with well-developed ventral adenostyle on femur (Fig. 5A).
Coxa of legpair 2 with posteroventrally directed conical process bearing laterally a set of setae and the gonopore opening at tip of process (Fig. 5B).
In female, legs are slightly shorter than in male.Coxa of legpair 2 with prominent swelling on posterior side (Fig. 5F) especially, distinct processes in P. montanum sp.nov.and P. adrianae (Fig. 5G-H).
No significant interspecific differences were observed, and both shorter and longer setae on valves can occur within a species.

Distribution
On the Australian mainland, the genus Pogonosternum has its main distribution area in eastern, northeastern and central Victoria and southeastern New South Wales (Fig. 7).

Notes on ecology and biology
Adults and juveniles (mostly subadults) of Pogonosternum are present on the surface in the cold or cool and rainy winter months, with a mating and activity peak between July and September.The genus can be found from near sea level (P.nigrovirgatum, P. jeekeli sp.nov.) to 1110 m a.s.l.(P.montanum sp.nov. in Kosciuszko National Park) and mostly inhabits forests, but P. jeekeli Decker, sp.nov.can also be found in coastal heathland in northeastern Tasmania (Mesibov & Churchill 2003), whereas P. jeekeli sp.nov.and P. montanum sp.nov.also occur in pine plantations (Car 2010).Pogonosternum species were preferably recorded from moist, but not wet, leaf litter.In some cases, specimens were found under loose bark on the forest floor and in a few cases, adult males were observed walking during the daytime on gravel roads.

Relationships
According to Jeekel (1982a)  However, the gonopods of Pogonosternum are unique within Antichiropodini, and its relationships within Antichiropodini are unclear due to our lack of understanding of the homology of the different processes of the gonopod.Jeekel (1987: 11) even questioned the division of Australian Australiosomatinae into two tribes: "Although these two groups are maintained here, it must be emphasized that this division probably gives an oversimplified picture of the actual systematic relationship between the genera involved.With the recent discovery of more taxa, it becomes more and more obvious that the classification of the Australian Paradoxosomatidae is more complicated than formerly understood and needs a critical revision".Future integrative phylogenetic studies covering the described and the many undescribed genera will increase our knowledge of relationships and the importance of gonopod characters.

Diagnosis
Differs from the other Pogonosternum species in having two lighter paramedian stripes and a median darker stripe; from P. jeekeli Decker, sp.nov., primarily by lateral process (lp) often shorter, not reaching or projecting most distad position of prolongation of femorite (prof), male tarsal and tibial brushes present to legpair 7, sometimes present to legpair 9, but then prof distinctly elongated and broadly curved.26A): margin of lateral edges of collum often slightly to distinctly lighter (Fig. 8B).Dorsum with 2 paramedian light yellowish brown stripes and darker median brown stripe.On prozonites the trapezoidal paramedian light band slightly broader anteriorly, and on metazonites slightly broader posteriorly, broadest at 1/3 of length (Figs 8D, 26A).Median darker stripe narrow to rhombic, broadest 3/4 of length on metazonites and prozonites.Flanks often distinctly lighter.Area around ozopores slightly to distinctly lighter, cloudy pale (Fig. 8C).
sternites.Sometimes with slightly developed sternal cones, especially in anterior and midbody rings.
leGs.Male tarsal and tibial brushes present from legpair 1 to 7 or 9, rarely to 8. Male coxa of legpair 6 and 7 slightly swollen to cone-like.Female coxa of legpair 2 rarely with slightly enlarged rounded process on caudal side directing posterodistad.

Distribution
From Central Gippsland and central Victoria to the Otway Ranges and Ballarat area; also present in northwestern Tasmania and on King Island (Fig. 7).It has recently been found in the city of Launceston in north central Tasmania, and is apparently introduced there (with short prof).

Remarks
Carl (1902) described Strongylosoma nigrovirgatum based on one male and one female in the Muséum d'histoire naturelle de la Ville de Genève.The male right gonopod is missing.We designate the male as lectotype and female as paralectotype.
The subspecies P. nigrovirgatum infuscum, described from Central Gippsland, only differs by a broader fp1 from the nominate species.In the material studied here, including material from the type locality of P. nigrovirgatum, the width of the fp1 differed within some populations from slender to broadly infuscum-like.Pogonosternum n. infuscum is treated here as a synonym of P. nigrovirgatum.
Specimens fitting the description of P. coniferum by Jeekel (1965) are restricted to the coastal area around Port Philip Bay.These have a very long and curved prof, a moderate to long lp, and male tarsal and tibial brushes present from legpair 1 to 9 (Fig. 9E-H), while in P. nigrovirgatum sensu stricto, distributed from northern central Victoria to Gippsland, prof and lp are short and tarsal and tibial brushes are present to legpair 7 (Fig. 9A-D).However, the Tasmanian, Otway Ranges and western central Victorian populations contain long coniferum-like (Fig. 9E-H) to intermediate states of prof (Fig. 10), sometimes both forms present within one population, with male brushes ranging to legpair 7, except in Brisbane Ranges National Park to legpair 9. Pogonosternum coniferum is here made a synonym of P. nigrovirgatum due to the existence of these intermediate forms and the fact that P. coniferum clusters with P. nigrovirgatum in a phylogenetic analysis based on mitochondrial COI and 16S rDNA sequences (Decker 2016a).

Diagnosis
Differs from other Pogonosternum species in having one lighter longitudinal stripe and no median darker stripe; from P. montanum Decker, sp.nov.and P. laetificum primarly by the enlarged femoral process 1 (fp1) and 2 (fp2) and the lateral process (lp) directed laterally, but also by the presence of a subtriangular pointed process of the female leg 2 coxa; male tarsal and tibial brushes present from legpair 1 to 7; anterior spiracles obliquely ovoid with anterodorsally slightly extended rim and spiracular filter not protruding; largest known species of Pogonosternum with midbody width of 2.8-3.2mm.

Distribution
Strzelecki Ranges and central southern part of the Victorian Highlands (Fig. 7).

Remarks
A phylogenetic analysis (Decker 2016a) showed that this species is very closely related to P. laetificum with low genetic distances between populations of the two species.
We accept P. adrianae as a valid species because of its constant morphology, larger size and distinctive details of the gonopods (prof, fp1, fp2, F), spiracles, dorsal colouration and process of female second leg 2 coxa, with no intermediate features between P. adrianae and P. laetificum noted.

Diagnosis
Differs from other Pogonosternum species in having one lighter longitudinal stripe and no median darker stripe; from P. adrianae and P. montanum Decker, sp.nov., primarily by the small femoral process 2 (fp2) and the lateral process (lp) being directed laterally, but also the presence of a rounded subtriangular, not pointed, process on the female leg 2 coxa; male tarsal and tibial brushes present from legpair 1 to 7-12; anterior spiracles obliquely ovoid with anterodorsally extended rim and spiracular filter not or slightly protruding.
spiraCles.Anterior spiracles distinctly obliquely ovoid.Rim raised with anterodorsal side broadly extended, not lobiform and spiracular filter not or slightly protruding.Posterior spiracle ovoid with low rim and spiracular filter not protruding (Fig. 17).

Distribution
Victorian Highlands north and east of Melbourne and northwestern Strzelecki Ranges (Fig. 7).

Remarks
There is no apparent geographical pattern to gonopod variation in P. laetificum (see also Decker 2016a).The distribution of male tarsal and tibial brushes often varies within a population at a single site.

Diagnosis
Differs from the other Pogonosternum species in having two lighter paramedian stripes and a median darker stripe; from P. nigrovirgatum, primarily by lateral process (lp) often longer, reaching or projecting distad of most distal position of prolongation of femorite (prof), male tarsal and tibial brushes present to legpair 9, but prof never distinctly elongated and broadly curved.Darker median stripe narrow to rhombic, broadest 3/4 of length on metazonites and prozonites.Flanks often distinctly lighter.Area around ozopores slightly to distinctly lighter, cloudy pale (Fig. 18C).
leGs.Male tarsal and tibial brushes present from legpair 1 to 9, abruptly absent after.
Gonopods.spiraCles.Anterior spiracles distinctly obliquely ovoid.Rim raised with anterodorsal side often broadly extended, not lobiform and spiracular filter not or slightly protruding.Posterior spiracle ovoid with low rim and spiracular filter not protruding (Fig. 21).

Ecology
Pogonosternum jeekeli Decker, sp.nov.was mostly found in forests to 400 m a.s.l., but was also collected at ca 920 m a.s.l. and was found in pine plantations by Car (2010).26E).Flanks and area around ozopores slightly lighter (Fig. 22C).

Ecology
Pogonosternum montanum Decker, sp.nov.Decker was mostly found in mountain forests from 600 to 1110 m a.s.l.It also occurs in pine plantations (Car 2010 and new collections west of Tumbarumba, New South Wales) and was collected in coastal Central Gippsland near Bruthen (AMS KS.105106), where it is possibly introduced.

Distribution
Australian Alps in far eastern Victoria and far southeastern New South Wales and adjacent regions (Fig. 7).
probably refers to P. nigrovirgatum, although Jeekel does not state what material he examined.