Revision of Australian "Centroptilum"

Details

The two species described as Centroptilum from Australia are actually a new genus mostly closely related to the New World genus Callibaetis, based on several synapomorphies in both the larvae and adults. Genetic data (primarily ribosomal DNA) is also showing Callibaetis to be the sister taxon of the Australian species, but sequences of other potentially related taxa or not yet available.

Several species have been identified by a combination of morphological and mtDNA. Nuclear markers are being obtained to test species boundaries among closely related mtDNA groups. Adults and some larvae can be identified relatively easily, but several species are highly similar as larvae. Larvae of the sp1 complex, including sp1, spTAS, and spSnowy cannot be reliably differentiated at this time, although the adults of sp1 and spTAS do differ (the adult of spSnowy is unkown), and all form a clade with relatively short branches separating them relative to the differences among the other species. It is possible the sp1 complex is actually a single variable species, but at this time we are treating them as different.

Diagnosis of Genus:

Adults: the combination of single marginal intercalaries in the basal half of the forewing and the presence of hindwings will differentiate "Centroptilum" from all other Australian genera except females of the Edmundsiops sp14 complex in northern Queensland which can have either single or no marginal intercalaries in the forewing; E sp14 occurs in northern QLD along with Centroptilum sp ARR1, but differs in having a forked second longitudinal vein in the hind wing.

Larvae:

Species known:

elongatum Suter 1986: SA, VIC, NSW. Males, females, and larvae described

collendum Harker 1957:NSW. Male and female subimagos and larvae described. Type material apparently missing.

sp ARR1/sp4: NT, NQLD. males, females and larvae known

spLogan: NNSW, SE QLD. Larvae only, although a single poorly preserved specimen has been tentatively associated with this species

spTAS: TAS. Larvae only, although a series of pinned male and female adults has been tentatively associated with this species as it is the only known from Tasmania. Larvae appear cryptic with mainland sp1 and spSnowy.

sp1: VIC, NSW. Larvae, males and females known. Larvae are cryptic with those of spTAS and spSnowy and highly similar to sp6, but COI data shows them to be distinct. Adults differ from those of spTAS by colour pattern (sp Snowy unknown)

spANIC: NNSW, ACT. Males and females known. Easily diagnosed by the presence of many small red punctations on the abdominal sterna. May be the adult of sp Snowy or spWonnangatta

spWonnangatta: VIC. Larvae only. Known from a small series from the Wonnangatta River, VIC. Larvae are highly similar to those of sp1, spSnowy, and spTAS, but differ in having a distinct subapcial elongate spot rather than a band on the femora (a terrible character, but so far it works!)

spSnowy: VIC. Larvae only. Known from a small series of specimens from Snowy Creek, Vic. Cryptic with sp1 and spTAS.

sp6: NSW. Larvae only. May be the larvae of C. collendum. Highly similar to larvae of sp1, spSnowy, and spTAS, but significantly smaller and genetically very distinct.

spBlackStripe: western VIC. Larvae only. Structurally the same as C. elongatum, but have a highly distinctive dark stripe on the abdomen and a pair of dark stripes on the notum.Known only from the Wimmera R, and is sympatric with elongatum, and may just be a colour variant. When fresh material becomes available DNA will be extracted for analysis and an attempt will be made to rear adults.

sp1E. VIC. Larvae only, and only from slide mounted material. Differs by having the superlingua much shorter than the lingua, but this may be an artifact of being slide mounted (this has not been observed in slides of other species, however). The setae on the dorsal side of the femora are of a slightly different shape and size than those of the sp1 complex, but additional material is needed to verify this. Fresh material will be sought this spring.

Keys

Images with diagnostic characters highlighted are available in the attached pdf at the bottom of the page. Larval images coming soon!

Preliminary Key to Adults
1aHind wing with 2 longitudinal veins, second vein unforked (3rd is present but attaches to hind margin << � length of wing)2
bHind wing with 3 longitudinal veins, second vein usually forked3
2amarginal intercalaries of forewing long; crossveins absent between costa and subcostaspLogan?
bMarginal intercalaries of forewing short; crossveins present between costa and subcostaARR1/sp4
3aHind wing with second longitudinal vein unforked, costal process pointed and distinctly curved, and two crossveins veins between 1 and 2, and 2 and 3. collendum Harker
b
Hind wing with second longitudinal vein forked; costal process never distinctly curved
4
4aHind wing with > 4 crossveins in between 1st longitudinal vein and anterior margin; marginal intercalaries single; abdominal terga uniformly coloured with dark transverse line in median area of posterior margin; mesonotum dark brown; area between costa and subcosta yellowishelongatum
bHind wing no or fewer than 2 crossveins between 1st longitudinal vein and anterior margin; males with paired marginal intercalaries anterior to MA (females with all intercalaries single) 5
5aAbdominal sterna with numerous small red spots,most dense laterally
spANIC
bAbdominal sterna without scattered red spots6
6aTasmania; dark transverse line at midpoint of each abdominal tergum; mesonotum of males dark reddish brown spTAS?
bmainland; dark transverse line at posterior margin of each abdominal tergum sp1

Preliminary Key to Larvae
1
a
With robust setae on outer margin of tibae; subapical pair of robust setae on femora pointed and relatively long
2
b
No robust setae on outer margin of tibiae or tarsi; subapical pair of robust setae on femora short and blunt 4
2
a
distinct brown median stripe on abdomen; thorax with pair submedian stripes; known only from western VIC in temporary rivers sp blackstripe
b
with longitudinal stripes on thorax and abdomen 3
3a
3-4 rows of robust setae on dorsal margin of femora; posterior margins of abdominal terga usually with alternating short and long spines, nearly contiguous basally; gena pale; mature larvae > 7mm; SA, VIC, NSW elongatum
b
1-2 rows of robust setae on dorsal margin of femora; posterior margins of abdominal terga with spines all of similar length and distinctly separated basally; genae and base of mandibles usually dark brown and conspicuously different than rest of head capsule; mature larvae nearly always < 7mm; northern NSW, southern QLD spLogan
4
a
Spines on posterior margins of terga as long as wide; small size; northernQLD, NT ARR1
b
spines on posterior margins of terga much longer than wide; NSW, VIC, TAS 5
5
a
Tas sp TAS
b
VIC, SA, NSW? 6
6
a
femora with indistinct subapical band, or band palest medially 7
b
femora with distinct subapical dark streak just on median part of surface of femora spWonnangatta
7
a
mature larvae < 7.5mm; NSW
sp6
b
mature larvae >8.0 mm
8
8
a
superlinguae much shorter than lingua
sp1E
b
superlinguae subequal in length to lingua

9
9
a
? sp1
b
? Only known from Snowy Creek, VIC at this time spSnowy

JeffWebb - 09 Feb 2009

I Attachment Action Size Date Who Comment
CentroptilumAdults.pdfpdf CentroptilumAdults.pdf manage 7 MB 2010-02-21 - 19:23 JeffWebb Photo plates of adults of 'Centroptilum' with diagnostic characters