Myrmecia imaii

Myrmecia imaii is known only from extreme southwest Western Australia: south and SE of Perth, east to Esperance, seldom more than a few km from the coast.

Identification
M. imaii is the only species of the Myrmecia pilosula complex found in WA.

Distribution based on Regional Taxon Lists
Australasian Region: Australia.

Biology
Taylor (2015)

All records of M. imaii are from the “High Rainfall” and “SE Coastal Provinces” of the “South Western Australian Floristic Region” defined by Hopper and Gioia (2004) and Hopper et al. (1996). Heterick (2009) reported the species from the recognized Botanical Districts of Esperance Plains, Jarrah Forest, Mallee and Warren. The fact that its relatives at species-complex level are of eastern Australian provenance implies that Jack-jumpers must previously have ranged or dispersed across southern Australia.

This is the species recorded as Promyrmecia pilosula by Clark (1951) from Albany (confirmed by MVMA voucher specimens), Denmark and Mundaring [-31 54, 116 10], the last locality extends the range indicated by the above records, and was a prime collecting site to Clark (who collected ants widely in the south-west, where he resided for many years). He commented that this species “is quite common in Albany and surrounding district, but it is rare further north” (1951: 204).

Karyology
The basic karyotype, 2K=6A +2Am(2n=8) differs strongly from those of other species reviewed above. Two independent AM inversions on chromosomes 1 and 2 were described in detail by Imai, Taylor et al. (1994: 146, Fig 5c–g). Complicated chromosome polymorphisms accompanying chromosome number reduction (2n=8 >7 > 6) by AM inversion, centric fission and centric fusion were also observed between chromosomes 1L and 4 and between chromosomes IS and 3. Despite this complexity the authors considered all examined specimens to be conspecific.

Nomenclature

 *  imaii. Myrmecia imaii Taylor, 2015: 517 (w.) AUSTRALIA.

Worker
General features as illustrated and in key couplets 1–4. The brassy cephalic pubescence is more diffuse and less evident than in Myrmecia banksi, and the middle and hind tibiae are consistently medium to dark brown, with the tarsi a shade lighter. Local identification remains straightforward as long as M. imaii remains the only species of the Myrmecia pilosula complex found in WA.

(Holotype, smallest paratype, largest paratype (mm): TL = ca 13.40, 12.00, 14.46; HW = 2.68, 2.32, 2.79; HL = 2.49, 2.16, 2.59; CI = 107, 107, 107; EL = 0.99, 0.88, 1.01; OI = 37, 38, 36; SL = 2.15, 1.93, 2.17; SI = 80, 83, 77; PW = 1.63, 1.43, 1.70; WL = 3.90, 3.33, 4.06; PetW = 1.07, 0.85, 1.08; PpetW = 1.64, 1.27, 1.65.

Type Material


Type deposition. Holotype and paratypes in, paratypes or type-compared vouchers in , , , , WAMA, TMHA) and in , , ,.

Etymology
Named for Hirotami T. Imai celebrating long friendship; to commend his leadership of the JACP project, his distinguished research on the karyology of Myrmecia species and other ants, his important “Minimum Interaction Hypothesis” for the evolution of chromosome numbers in animals and his productive stewardship of the Japanese Ant Database Group (2003).